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This study investigated self-heating and off-gassing of Scots pine (Pinus sylvestris) wood pellets made from sawdust generated from separated mature and juvenile wood. The pellets were produced at an industrial scale and stored in large piles of about 7.2 tonnes. The production process involved drying the sawdust using three different methods and to varying moisture contents. The results indicated significant influences of both raw material type (F(6) = 61.97, p < 0.05) and drying method (F(2) = 65.38, p < 0.05) on the self-heating of the pellets. The results from the multiple regression analysis further showed that both the raw material type and pellet moisture content significantly influenced the temperature increase, with strong correlations observed for pellets produced using low-temperature drying (F(3, 14) = 83.52, multiple R2 = 0.95, p < 0.05), and medium temperature drying (F(3, 13) = 62.05, multiple R2 = 0.93, p < 0.05). The pellets produced from fresh mature wood sawdust were found to be more prone to self-heating and off-gassing while steam drying the sawdust at high temperature and pressure led to a significant reduction in heat and gas generation across all materials. The heightened self-heating and off-gassing in mature wood pellet can be attributed to a higher proportion of sapwood in the raw material. The probable explanations to the observed differences are in line with biological mechanisms for self-heating and off-gassing, as well as the chemical oxidation of fatty and resin acids.

This study investigated self-heating and off-gassing of Scots pine (Pinus sylvestris) wood pellets made from sawdust generated from separated mature and juvenile wood. The pellets were produced at an industrial scale and stored in large piles of about 7.2 tonnes. The production process involved drying the sawdust using three different methods and to varying moisture contents. The results indicated significant influences of both raw material type (F(6) = 61.97, p < 0.05) and drying method (F(2) = 65.38, p < 0.05) on the self-heating of the pellets. The results from the multiple regression analysis further showed that both the raw material type and pellet moisture content significantly influenced the temperature increase, with strong correlations observed for pellets produced using low-temperature drying (F(3, 14) = 83.52, multiple R2 = 0.95, p < 0.05), and medium temperature drying (F(3, 13) = 62.05, multiple R2 = 0.93, p < 0.05). The pellets produced from fresh mature wood sawdust were found to be more prone to self-heating and off-gassing while steam drying the sawdust at high temperature and pressure led to a significant reduction in heat and gas generation across all materials. The heightened self-heating and off-gassing in mature wood pellet can be attributed to a higher proportion of sapwood in the raw material. The probable explanations to the observed differences are in line with biological mechanisms for self-heating and off-gassing, as well as the chemical oxidation of fatty and resin acids.

This work presents an efficient Discrete Element Method (DEM) framework for the simulation of the thermal behavior of granular media. The main focus is on long-lasting granular flows, involving heat transfer and generation due to mechanical energy dissipation. The proposed approach uses efficient strategies to reduce the computational cost of the analyses and, therefore, to enable its application to problems of practical relevance. For instance, the contact area is adjusted to compensate for the artificial material softening that is typically considered in DEM to increase the time step size. After extended validation, the methodology is applied to the simulation of different setups of an experimental rotating drum. The numerical simulations presented good agreement with the experimental results and allowed a detailed analysis of the mechanisms and patterns of heat generation, which could not be extrapolated from the experimental campaign., The authors acknowledge the support from MCIN/AEI, Spain and FEDER Una manera de hacer Europa for funding this work via project PID2021-122676NB-I00. The authors also acknowledge the Severo Ochoa Programme, Spain through the Grant CEX2018-000797-S funded by the Spanish Ministry of Economy and Competitiveness, Spain through the “Severo Ochoa Programme for Centres of Excellence in R&D”. The first author acknowledges the Marie SKŁODOWSKA-CURIE Innovative Training Network MATHEGRAM, the People Programme (Marie SKŁODOWSKA-CURIE Actions) of the European Union’s Horizon 2020 Programme H2020 under REA grant agreement No. 813202, for funding part of his research., Peer Reviewed, Postprint (published version)

This study investigated self-heating and off-gassing of Scots pine (Pinus sylvestris) wood pellets made from sawdust generated from separated mature and juvenile wood. The pellets were produced at an industrial scale and stored in large piles of about 7.2 tonnes. The production process involved drying the sawdust using three different methods and to varying moisture contents. The results indicated significant influences of both raw material type (F(6) = 61.97, p < 0.05) and drying method (F(2) = 65.38, p < 0.05) on the self-heating of the pellets. The results from the multiple regression analysis further showed that both the raw material type and pellet moisture content significantly influenced the temperature increase, with strong correlations observed for pellets produced using low-temperature drying (F(3, 14) = 83.52, multiple R2 = 0.95, p < 0.05), and medium temperature drying (F(3, 13) = 62.05, multiple R2 = 0.93, p < 0.05). The pellets produced from fresh mature wood sawdust were found to be more prone to self-heating and off-gassing while steam drying the sawdust at high temperature and pressure led to a significant reduction in heat and gas generation across all materials. The heightened self-heating and off-gassing in mature wood pellet can be attributed to a higher proportion of sapwood in the raw material. The probable explanations to the observed differences are in line with biological mechanisms for self-heating and off-gassing, as well as the chemical oxidation of fatty and resin acids.

This study investigated self-heating and off-gassing of Scots pine (Pinus sylvestris) wood pellets made from sawdust generated from separated mature and juvenile wood. The pellets were produced at an industrial scale and stored in large piles of about 7.2 tonnes. The production process involved drying the sawdust using three different methods and to varying moisture contents. The results indicated significant influences of both raw material type (F(6) = 61.97, p < 0.05) and drying method (F(2) = 65.38, p < 0.05) on the self-heating of the pellets. The results from the multiple regression analysis further showed that both the raw material type and pellet moisture content significantly influenced the temperature increase, with strong correlations observed for pellets produced using low-temperature drying (F(3, 14) = 83.52, multiple R2 = 0.95, p < 0.05), and medium temperature drying (F(3, 13) = 62.05, multiple R2 = 0.93, p < 0.05). The pellets produced from fresh mature wood sawdust were found to be more prone to self-heating and off-gassing while steam drying the sawdust at high temperature and pressure led to a significant reduction in heat and gas generation across all materials. The heightened self-heating and off-gassing in mature wood pellet can be attributed to a higher proportion of sapwood in the raw material. The probable explanations to the observed differences are in line with biological mechanisms for self-heating and off-gassing, as well as the chemical oxidation of fatty and resin acids.

This study investigated self-heating and off-gassing of Scots pine (Pinus sylvestris) wood pellets made from sawdust generated from separated mature and juvenile wood. The pellets were produced at an industrial scale and stored in large piles of about 7.2 tonnes. The production process involved drying the sawdust using three different methods and to varying moisture contents. The results indicated significant influences of both raw material type (F(6) = 61.97, p < 0.05) and drying method (F(2) = 65.38, p < 0.05) on the self-heating of the pellets. The results from the multiple regression analysis further showed that both the raw material type and pellet moisture content significantly influenced the temperature increase, with strong correlations observed for pellets produced using low-temperature drying (F(3, 14) = 83.52, multiple R2 = 0.95, p < 0.05), and medium temperature drying (F(3, 13) = 62.05, multiple R2 = 0.93, p < 0.05). The pellets produced from fresh mature wood sawdust were found to be more prone to self-heating and off-gassing while steam drying the sawdust at high temperature and pressure led to a significant reduction in heat and gas generation across all materials. The heightened self-heating and off-gassing in mature wood pellet can be attributed to a higher proportion of sapwood in the raw material. The probable explanations to the observed differences are in line with biological mechanisms for self-heating and off-gassing, as well as the chemical oxidation of fatty and resin acids.

Wood pellets have become a preferred solid biomass fuel for heat and power generation due to their standardized nature, known properties, and consistent quality. However, pellets produced from fresh sawdust sometimes undergo self-heating and off-gassing during storage. This poses a challenge for their transportation and storage. The aim of this thesis was to increase the body of knowledge towards understanding the mechanisms underlying the self-heating and off-gassing of wood pellets, and offer solutions for producing wood pellets from freshly generated sawdust, with reduced self-heating and off-gassing tendencies. The effects of total wood extractive content and types of extractives in the raw material on off-gassing of wood pellets were investigated through two separate studies (papers I and II). The results from paper I showed that the total amount of extractives in the raw material has little effect on off-gassing. While gas emissions were reduced for pellets produced from Scots pine sawdust that had low amounts of extractives (stored and acetone extracted), the coefficients of determination (R2) from the linear correlation analysis between off-gassing and the total extractive content of the raw materials were below 0.5 for all the three off-gasses indicating low or no correlation. The results of cellulose pellets with added additive oils (paper II) showed that the off-gassing is highly dependent on the type of extractives in the raw material. The highest mean concentrations of the carbon oxides and methane were recorded from cellulose pellets with added linseed oil. Pellets with added linseed oil had higher off-gas emissions due to the high content of unsaturated fatty acids of 73.9% linolenic and 7.6% linoleic. The effects of raw material type and pre-treatments on self-heating and off-gassing of wood pellets were also investigated through two separate studies (papers III and IV). The results from both studies indicated significant influences of both raw mater, The global wood pellets production increased from about 18 million tonnes in 2012 to about 46 million tonnes in 2022. Wood pellets have become a preferred solid biomass fuel for heat and power generation due to their standardized nature, known properties, and consistent quality. However, pellets produced from fresh sawdust sometimes undergo self-heating and off-gassing and this poses a challenge for their transportation and storage. The aim of this thesis was to increase the body of knowledge towards understanding the mechanisms underlying the self-heating and off-gassing of wood pellets, and offer solutions for producing wood pellets with reduced tendencies for self-heating and off-gassing using freshly generated sawdust. The results showed that a biological process, in combination with the chemical oxidation of unsaturated fatty acids lay behind the self-heating and off-gassing of wood pellets. While storing of fresh sawdust for a period of time prior to pellet production remains the most effective method for mitigating self-heating and off-gassing, sorting and separating the raw materials at source can facilitate the development of storage schedules tailored to specific raw materials, thereby reducing on the raw material storage time., Wood pellets have become a preferred solid biomass fuel for heat and power generation due to their standardized nature, known properties, and consistent quality. However, pellets produced from fresh sawdust sometimes undergo self-heating and off-gassing and this poses a challenge for their transportation and storage. The aim of this thesis was to increase the body of knowledge towards understanding the mechanisms underlying the self-heating and off-gassing of wood pellets. The results from paper I showed that the total amount of extractives in the raw material has little effect on off-gassing. Although pellets produced from Scots pine sawdust with lower extractive contents exhibited reduced concentrations of off-gasses; CO, CO2 and CH4, increasing the extractive content of the sawdust through the addition of additive oils did not result in increased off-gas emissions. The results of pure cellulose pellets with added additive oils showed that off-gassing is influenced by the type of extractives in the raw material (paper II). The highest concentrations of off-gasses were recorded from pure cellulose pellets with added linseed oil due to their high content of unsaturated fatty acids of 73.9% linolenic and 7.6% linoleic. The results from papers III and IV indicated significant effects of both raw material and drying temperature on off-gassing and self-heating of wood pellets. There was a strong linear correlation between off-gassing and the sapwood content of the raw material, with correlation coefficient (R) values greater than 0.9 at p < 0.001 for all the off-gases (paper III). An increase in sapwood content led to a significant increase in off-gassing of CO2, CO and CH4, and O2 consumption. Storing of sawdust for over six months prior to pellet production, and increasing the drying temperature led to a significant reduction in off-gassing for sapwood pellets. For heartwood pellets, increasing the drying temperature resulted in increased off-gassing while raw mate, This study was part of the collaborative research projects between Karlstad University and the Swedish University of Agricultural Sciences, SLU.

Wood pellets have become a preferred solid biomass fuel for heat and power generation due to their standardized nature, known properties, and consistent quality. However, pellets produced from fresh sawdust sometimes undergo self-heating and off-gassing during storage. This poses a challenge for their transportation and storage. The aim of this thesis was to increase the body of knowledge towards understanding the mechanisms underlying the self-heating and off-gassing of wood pellets, and offer solutions for producing wood pellets from freshly generated sawdust, with reduced self-heating and off-gassing tendencies. The effects of total wood extractive content and types of extractives in the raw material on off-gassing of wood pellets were investigated through two separate studies (papers I and II). The results from paper I showed that the total amount of extractives in the raw material has little effect on off-gassing. While gas emissions were reduced for pellets produced from Scots pine sawdust that had low amounts of extractives (stored and acetone extracted), the coefficients of determination (R2) from the linear correlation analysis between off-gassing and the total extractive content of the raw materials were below 0.5 for all the three off-gasses indicating low or no correlation. The results of cellulose pellets with added additive oils (paper II) showed that the off-gassing is highly dependent on the type of extractives in the raw material. The highest mean concentrations of the carbon oxides and methane were recorded from cellulose pellets with added linseed oil. Pellets with added linseed oil had higher off-gas emissions due to the high content of unsaturated fatty acids of 73.9% linolenic and 7.6% linoleic. The effects of raw material type and pre-treatments on self-heating and off-gassing of wood pellets were also investigated through two separate studies (papers III and IV). The results from both studies indicated significant influences of both raw mater, The global wood pellets production increased from about 18 million tonnes in 2012 to about 46 million tonnes in 2022. Wood pellets have become a preferred solid biomass fuel for heat and power generation due to their standardized nature, known properties, and consistent quality. However, pellets produced from fresh sawdust sometimes undergo self-heating and off-gassing and this poses a challenge for their transportation and storage. The aim of this thesis was to increase the body of knowledge towards understanding the mechanisms underlying the self-heating and off-gassing of wood pellets, and offer solutions for producing wood pellets with reduced tendencies for self-heating and off-gassing using freshly generated sawdust. The results showed that a biological process, in combination with the chemical oxidation of unsaturated fatty acids lay behind the self-heating and off-gassing of wood pellets. While storing of fresh sawdust for a period of time prior to pellet production remains the most effective method for mitigating self-heating and off-gassing, sorting and separating the raw materials at source can facilitate the development of storage schedules tailored to specific raw materials, thereby reducing on the raw material storage time., Wood pellets have become a preferred solid biomass fuel for heat and power generation due to their standardized nature, known properties, and consistent quality. However, pellets produced from fresh sawdust sometimes undergo self-heating and off-gassing and this poses a challenge for their transportation and storage. The aim of this thesis was to increase the body of knowledge towards understanding the mechanisms underlying the self-heating and off-gassing of wood pellets. The results from paper I showed that the total amount of extractives in the raw material has little effect on off-gassing. Although pellets produced from Scots pine sawdust with lower extractive contents exhibited reduced concentrations of off-gasses; CO, CO2 and CH4, increasing the extractive content of the sawdust through the addition of additive oils did not result in increased off-gas emissions. The results of pure cellulose pellets with added additive oils showed that off-gassing is influenced by the type of extractives in the raw material (paper II). The highest concentrations of off-gasses were recorded from pure cellulose pellets with added linseed oil due to their high content of unsaturated fatty acids of 73.9% linolenic and 7.6% linoleic. The results from papers III and IV indicated significant effects of both raw material and drying temperature on off-gassing and self-heating of wood pellets. There was a strong linear correlation between off-gassing and the sapwood content of the raw material, with correlation coefficient (R) values greater than 0.9 at p < 0.001 for all the off-gases (paper III). An increase in sapwood content led to a significant increase in off-gassing of CO2, CO and CH4, and O2 consumption. Storing of sawdust for over six months prior to pellet production, and increasing the drying temperature led to a significant reduction in off-gassing for sapwood pellets. For heartwood pellets, increasing the drying temperature resulted in increased off-gassing while raw mate, This study was part of the collaborative research projects between Karlstad University and the Swedish University of Agricultural Sciences, SLU.

Wood pellets have become a preferred solid biomass fuel for heat and power generation due to their standardized nature, known properties, and consistent quality. However, pellets produced from fresh sawdust sometimes undergo self-heating and off-gassing during storage. This poses a challenge for their transportation and storage. The aim of this thesis was to increase the body of knowledge towards understanding the mechanisms underlying the self-heating and off-gassing of wood pellets, and offer solutions for producing wood pellets from freshly generated sawdust, with reduced self-heating and off-gassing tendencies. The effects of total wood extractive content and types of extractives in the raw material on off-gassing of wood pellets were investigated through two separate studies (papers I and II). The results from paper I showed that the total amount of extractives in the raw material has little effect on off-gassing. While gas emissions were reduced for pellets produced from Scots pine sawdust that had low amounts of extractives (stored and acetone extracted), the coefficients of determination (R2) from the linear correlation analysis between off-gassing and the total extractive content of the raw materials were below 0.5 for all the three off-gasses indicating low or no correlation. The results of cellulose pellets with added additive oils (paper II) showed that the off-gassing is highly dependent on the type of extractives in the raw material. The highest mean concentrations of the carbon oxides and methane were recorded from cellulose pellets with added linseed oil. Pellets with added linseed oil had higher off-gas emissions due to the high content of unsaturated fatty acids of 73.9% linolenic and 7.6% linoleic. The effects of raw material type and pre-treatments on self-heating and off-gassing of wood pellets were also investigated through two separate studies (papers III and IV). The results from both studies indicated significant influences of both raw mater, The global wood pellets production increased from about 18 million tonnes in 2012 to about 46 million tonnes in 2022. Wood pellets have become a preferred solid biomass fuel for heat and power generation due to their standardized nature, known properties, and consistent quality. However, pellets produced from fresh sawdust sometimes undergo self-heating and off-gassing and this poses a challenge for their transportation and storage. The aim of this thesis was to increase the body of knowledge towards understanding the mechanisms underlying the self-heating and off-gassing of wood pellets, and offer solutions for producing wood pellets with reduced tendencies for self-heating and off-gassing using freshly generated sawdust. The results showed that a biological process, in combination with the chemical oxidation of unsaturated fatty acids lay behind the self-heating and off-gassing of wood pellets. While storing of fresh sawdust for a period of time prior to pellet production remains the most effective method for mitigating self-heating and off-gassing, sorting and separating the raw materials at source can facilitate the development of storage schedules tailored to specific raw materials, thereby reducing on the raw material storage time., Wood pellets have become a preferred solid biomass fuel for heat and power generation due to their standardized nature, known properties, and consistent quality. However, pellets produced from fresh sawdust sometimes undergo self-heating and off-gassing and this poses a challenge for their transportation and storage. The aim of this thesis was to increase the body of knowledge towards understanding the mechanisms underlying the self-heating and off-gassing of wood pellets. The results from paper I showed that the total amount of extractives in the raw material has little effect on off-gassing. Although pellets produced from Scots pine sawdust with lower extractive contents exhibited reduced concentrations of off-gasses; CO, CO2 and CH4, increasing the extractive content of the sawdust through the addition of additive oils did not result in increased off-gas emissions. The results of pure cellulose pellets with added additive oils showed that off-gassing is influenced by the type of extractives in the raw material (paper II). The highest concentrations of off-gasses were recorded from pure cellulose pellets with added linseed oil due to their high content of unsaturated fatty acids of 73.9% linolenic and 7.6% linoleic. The results from papers III and IV indicated significant effects of both raw material and drying temperature on off-gassing and self-heating of wood pellets. There was a strong linear correlation between off-gassing and the sapwood content of the raw material, with correlation coefficient (R) values greater than 0.9 at p < 0.001 for all the off-gases (paper III). An increase in sapwood content led to a significant increase in off-gassing of CO2, CO and CH4, and O2 consumption. Storing of sawdust for over six months prior to pellet production, and increasing the drying temperature led to a significant reduction in off-gassing for sapwood pellets. For heartwood pellets, increasing the drying temperature resulted in increased off-gassing while raw mate, This study was part of the collaborative research projects between Karlstad University and the Swedish University of Agricultural Sciences, SLU.

Anisotropic hybrid nanostructures stand out as promising therapeutic agents in photothermal conversion-based treatments. Accordingly, understanding local heat generation mediated by light-to-heat conversion of absorbing multicomponent nanoparticles at the single-particle level has forthwith become a subject of broad and current interest. Nonetheless, evaluating reliable temperature profiles around a single trapped nanoparticle is challenging from all of the experimental, computational, and fundamental viewpoints. Committed to filling this gap, the heat generation of an anisotropic hybrid nanostructure is explored by means of two different experimental approaches from which the local temperature is measured in a direct or indirect way, all in the context of hot Brownian motion theory. The results were compared with analytical results supported by the numerical computation of the wavelength-dependent absorption efficiencies in the discrete dipole approximation for scattering calculations, which has been extended to inhomogeneous nanostructures. Overall, we provide a consistent and comprehensive view of the heat generation in optical traps of highly absorbing particles from the viewpoint of the hot Brownian motion theory., Ministerio de Ciencia e Innovacion (España), Ministerio de Economía, Industria y Competitividad (España), Depto. de Química Física, Fac. de Ciencias Químicas, TRUE, pub, Descuento UCM

Granular flow is common in many industrial applications, and involves heat generation from frictional contacts and inelastic collisions between particles. The self-heating process is still poorly understood despite being intrinsic to many processes. This work, for the first time, explores this problem experimentally by quantifying the temperature rise of granular flows in a rotating drum with a robust methodology based on infrared thermography. Particles of four different materials (lead, steel, plastic and glass) are used in the experiments, at various rotation speeds and drum fill ratios. To assess the mechanical behaviour, the flow regime of every experiment was determined. It was inferred that particles with higher density tend to generate more heat. It was also revealed that increasing the rotation speed favours the temperature rise. At the same time, the fill ratio had the least influence on the thermal response of the particulate systems considered., his project is funded through Marie SKŁODOWSKA-CURIE Innovative Training Network MATHEGRAM, the People Programme (Marie SKŁODOWSKA-CURIE Actions) of the European Union's Horizon 2020 Programme H2020 under REA grant agreement No. 813202. Dr. Franci acknowledges the support from MCIN/AEI/10.13039/501100011033 and FEDER Una manera de hacer Europa for funding his work via project PID2021-122676NB-I00. Prof. Oñate acknowledges the Severo Ochoa Programme through the Grant CEX2018-000797-S funded by MCIN/AEI/10.13039/501100011033., Peer Reviewed, Postprint (published version)

På grund av energiomställningen, Sveriges mål om att ha en fossilfri elproduktion 2040 samt målet om nettonollutsläpp av växthusgaser 2045 förväntas en omfattande utbyggnad av förnybara energikällor ske. I denna rapport har därför elbehovet, potentialen för elproduktion, möjliga framtida systemproblem samt lösningar undersökts. Efter en omfattande litteraturstudie har det framkommit att elbehovet kommer att öka till det dubbla i Sverige och den största delen av detta ökade behov förväntas komma från vätgasproduktion för tillverkning av fossilfritt stål. Då antal parter som styr investerinsbesluten för de mest energikrävande projekten är få, råder stor osäkerhet kring hur stor denna ökning faktiskt kommer att bli. I det högsta fallet kan elbehovet uppgå till 370 TWh. Med antagandet att elektrifieringstakten i samhället är hög tillsammands med insikten att Sverige har ambitiösa energi- och klimatmål är det sannolikt att det inhemska elbehovet kommer ligga i närheten av 286 TWh. Utöver det förväntas effektbehovet och därmed effektbehovet under topplasttimmen öka markant. Det kommer med stor sannolikhet ligga i intervallet 42 - 49 GW. När det gäller utbyggnad av vattenkraft verkar det osannolikt med nybyggnation. Kärnkraftens potential och produktion i framtiden kommer bero på ett antal lagar om konstruktion av nya reaktorer, huruvida befintlig kärnkrafts livstid förlängs bortom 60 år samt möjligheten att hantera avfallet. Vindkraften spås bli det dominerande kraftslaget med en årsproduktion på upp till 157 TWh men där det finns ett antal flaskhalsar i form av ansökningsprocessen samt intressekonflikter med andra intressenter som påverkar utbyggnadstakten. Solkraftens potential bedöms vara god trots att Sverige har låg solpotential jämfört med många andra länder, detta då solkraften har få intressekonflikter med andra intressenter. Kraftvärmen kan öka sin elproduktion i det fall då antalet produktionstimmar ökar och värmekraften tar tillvara på spillvärmen. Denna potent, Sverige har ambitiösa mål för att bli mer hållbart, inklusive att ha en fossilfri elproduktion 2040 och nollutsläpp av växthusgaser 2045. Examensarbetet utforskar möjliga utmaningar som systemet kan ställas inför genom att titta på landets framtida elbehov och potentialen för de energikällor som kan byggas i Sverige. Rapporten visar att elbehovet kommer att fördubblas, främst på grund av det tillkommande behovet av den fossilfria stålproduktionen. Men det finns osäkerhet kring hur stor denna ökning exakt kommer att vara. Vindkraft förväntas bli den största energikällan, men det finns utmaningar med att bygga ut den då endast en liten del av Sveriges yta är tillgäglig för vindkraften. Dessutom visar det sig att en stor del av projekten inte godkönns i den långa ansökningsprocessen. Solkraft har också potential trots Sveriges låga solinstrålning. Detta beror främst på att den kan byggas på platser där andra energikällor inte får vara. En del av kärnkraften når slutet av sin livlängd och om inte mer kärnkraft byggs ut kan det uppstå problem med elnätets stabilitet. En lösning kan vara att offra en liten del av vindkraftenens produk- tion för att hjälpa till att stabilisera systemet. Detta sker genom att justera hastigheten med vilken vindturbinerna roterar. För att säkerställa att det alltid finns tillräckligt med el, även när det inte blåser eller solen inte lyser, behövs flexibilitet i systemet. Flexibilitet introduceras exempelvis genom energilagring samt genom tillfällig sänkning av förbrukningen. Sammanfattningsvis visar detta arbete att även om det finns utmaningar framför oss, finns det också lösningar som kan hjälpa Sverige att uppnå de satta hållbarhetsmålen men att denna omställning kräver en del investeringar i både utbyggnad samt flexibilitet.

This paper provides experimental data on the temperature rise during granular flows in a small-scale rotating drum due to heat generation. All heat is believed to be generated by conversion of some mechanical energy, through mechanisms such as friction and collisions between particles and between particles and walls. Particles of different material types were used, while multiple rotation speeds were considered, and the drum was filled with different amounts of particles. The temperature of the granular materials inside the rotating drum was monitored using a thermal camera. The temperature increases at specific times of each experiment are presented in form of tables, along with the average and standard deviation of the repetitions of each setup configuration. The data can be used as a reference to set the operating conditions of rotating drums, in addition to calibrating numerical models and validating computer simulations., This project is funded through Marie SKŁODOWSKA-CURIE Innovative Training Network MATHEGRAM1, the People Programme (Marie SKŁODOWSKA-CURIE Actions) of the European Union's Horizon 2020 Programme H2020 under REA grant agreement No. 813202. Dr. Franci acknowledges the support from MCIN/AEI/10.13039/501100011033 and FEDER Una manera de hacer Europa for funding his work via project PID2021-122676NB-I00. Prof. Oñate acknowledges the Severo Ochoa Programme through the Grant CEX2018-000797-S funded by MCIN/AEI/10.13039/501100011033., Peer Reviewed, Postprint (published version)

Vanadium redox flow batteries (VRFBs) are one of the most promising technologies for renewable energy storage. However, complex thermal issues caused by excessive heat generation during high-rate operations and various heat transfer behaviors in diverse climates dramatically affect the efficiency and stability of VRFBs. In this review, we summarize the thermal issues of VRFBs reported in the literature. First, the fundamental mechanisms of heat generation and heat transfer are elaborated. Thermal effects on electrochemical reactions and critical components in VRFBs are then presented. An operating temperature range of 10∼40 °C for VRFBs with high efficiency, weak side reactions, high electrolyte stability, and low crossover is suggested. Furthermore, thermal models including two-dimensional models, three-dimensional models, and lumped models are summarized. Moreover, existing thermal management methods are analyzed. Employing titanium heat exchangers with anti-corrosive properties to adjust the temperature of electrolytes is recommended. Finally, the remaining challenges to enhance the efficiency and stability of VRFBs under harsh thermal conditions are provided. This review offers an in-depth insight into the thermal issues of VRFBs, facilitating the design of next-generation VRFBs with high-power density. © 2022 Elsevier Ltd

Tesi amb menció de Doctorat Industrial (Generalitat de Catalunya), (English) The fresh water scarcity has become a concern for societies as a result of the scientific evidence about climate change and the intensive human activities. Thermal separation is one of the best available techniques for waste water treatment where the pollutants are removed from wastewaters by evaporating the water at the expense of large amounts of energy. In many industries there is no access to heat waste, thus a clean source of energy is required. The so-called hydrodynamic heat generators are claimed as high efficiency heating devices, avoiding scaling by warming liquids without transfer surfaces with the help of cavitation effects. However, neither the heat transfer mechanisms nor the amount of energy released to the surrounding liquid have been sufficiently understood yet. Based on this, the objective of the thesis has been to investigate the effects of cavitation on heating processes confirm the generation of heat in cavitating hydraulic systems and quantify the energy released by cavitation. The produced knowledge about the heat transfer mechanisms and the behaviour of cavitation in heat processes helps to assess the design of hydrodynamic heat generators. For that, an experimental approach has been adopted in a new test rig devoted to study the macroscale thermodynamic effects of attached sheet cavitation developed inside an ad hoc converging-diverging pipe with asymmetric rectangular cross section. This cavitation tunnel has been equipped with a control system to set a wide range of stable flow conditions by means of the centrifugal pump rotating speed and the opening ratio of a control valve. A pneumatic system has permitted to modify the reference pressure and a data acquisition system is used to record the operating parameters such as the pressures, temperatures and pump electrical power consumption and rotating speed. Initially, a series of short-term tests at non-cavitating and cavitating regimes have been performed to map the operation of t, (Català) L'escassetat d'aigua dolça s'ha convertit en una qüestió rellevant per a les societats com a resultat de l'evidència científica sobre el canvi climàtic i les activitats humanes intensives. La separació tèrmica és una de les millors tècniques disponibles per al tractament d'aigües residuals on els contaminants s'eliminen de les aigües residuals mitjançant l'evaporació de l'aigua mitjançant grans quantitats d'energia. En moltes indústries no hi ha accés a fonts de calor residuals, per tant es requereix una font d'energia neta. Els anomenats generadors de calor hidrodinàmics es proclamen com a dispositius d'escalfament d'alta eficiència, que eviten la formació d'incrustacions escalfant sense superfícies de transferència amb l'ajuda de la cavitació. Tanmateix, encara no s'han descrit ni els mecanismes de transferència de calor ni la quantitat d'energia alliberada al líquid en aquest tipus de dispositius. A partir d'això, l'objectiu de la tesi ha estat investigar els efectes de la cavitació en els processos de calefacció, confirmar la generació de calor en sistemes hidràulics cavitants i quantificar l'energia alliberada per la cavitació. El coneixement produït sobre els mecanismes de transferència de calor i el comportament de la cavitació en els processos de calor ajuda a avaluar el disseny de generadors de calor hidrodinàmics. Sota aquesta situació, s'ha adoptat un enfocament experimental en una nova instal·lació experimental dedicada a estudiar els efectes termodinàmics a macroescala de la cavitació de làmina desenvolupada dins d'un tub ad hoc convergent-divergent amb secció transversal rectangular asimètrica. Aquest túnel de cavitació ha estat equipat amb un sistema de control per establir una àmplia gamma de condicions de cabal estable mitjançant la velocitat de rotació de la bomba centrífuga i l'obertura d'una vàlvula de control. Un sistema pneumàtic ha permès modificar la pressió de referència i s'utilitza un sistema d'adquisició de dades per enregistrar, Postprint (published version)

The influence of friction stir welding parameters on thermo-mechanical behavior of the material during welding is analyzed. An aluminum alloy is considered (Al 2024 T351), and different rotating and welding speeds are applied. The finite element model consists of the working plate (Al alloy), backing plate and welding tool. The influence of the welding conditions on material behavior is taken into account the application of the Johnson-Cook material model. The rotation speed of the tool affects the results. If increased, it contributes to an increase of friction-generated heat intensity. The other component of the generated heat, which stems from the plastic deformation of the material, is negligibly changed. When the welding speed, i.e. tool translation speed, is increased, the intensity of friction-generated heat decreases, while the heat generation due to plastic deforming is becoming more pronounced. Summed, this leads to rather small change of the total generation. The changes of the heat generation influence both the temperature field and reaction force. Also, the inadequate selection of welding parameters resulted in occurrence of the defects (pores) in the model.

This dissertation reviews and clarifies the fundamental thermodynamic relationships relevant to the interpretation of potentiometric entropy measurements on lithium-ion batteries (LIBs) to gain insight into the physicochemical phenomena occurring during cycling. First, contributions from configurational, vibrational, and electronic excitations to the entropy ofan ideal intercalation compound used as a cathode in a battery system were analyzed. The results of this analysis were used to provide an interpretative guide of open circuit voltage Uocv(x, T) and entropic potential ∂Uocv(x, T)/∂T measurements to identify different mechanisms of intercalation, including (i) lithium intercalation as a homogeneous solid solution, (ii) ion ordering reactions from a homogeneous solid solution, (iii) first-order phase transitions involving a two-phase coexistence, and/or (iv) first-order phase transitions passing through a stable intermediate phase. These interpretations were illustrated with experimental data for different battery electrode materials including TiS2, LiCoO2, Li4/3Ti5/3O4, LiFePO4, and graphite electrodes with metallic lithium as the counter electrode. The systematic interpretation of Uocv(x, T) and ∂Uocv(x, T)/∂T can enhance other structural analysis techniques such as X-ray diffraction, electron energy-loss spectroscopy, and Raman spectroscopy. Thermal signatures associated with electrochemical and transport phenomena occurring in LIB systems were investigated by performing potentiometric entropy measurement and isothermal operando calorimetry on LIB systems. Here, LIB system consisting of electrodes made of TiNb2O7 and PNb9O25 were investigated. The potentiometric entropy measurements of TiNb2O7 and PNb9O25 featured signatures of intralayer ion ordering upon lithiation that could not be observed with in situ X-ray diffraction. Furthermore, entropy measurements also confirmed the semiconductor-to-metal transition taking place at PNb9O25 upon lithiation. Furthermo

The objective of this paper is to analyze the influence of heat absorption/generation and mass diffusion on magnetohydrodynamics(MHD) Jeffrey fluid flow over a perpendicular plate moving exponentially immersed in a porous media. The Newtonian heating condition are udes for the fluid motion. The impact of thermal radiation is used in the energy equation. The two types of magnetic field have been evaluated. The main purpose of present work is to acquire the analytical solution with the help of Atangana-Baleanu (AB), Caputo, and Caputo-Fabrizio fractional derivatives. We have drawn a graphical comparison between the solutions of these three types of fractional models of jeffery fluid. Graphs of different parameters have been also plotted using MathCad software. Furthermore, comparison among ordinary and fractionalized velocity fields are made to observe the impact of fractional parameter . It is clear from graph that velocity obtained with ordinary derivative is higher than that obtained with fractional derivatives. It is also found that velocity obtained with Atangana-Baleanu (AB) fractional derivative is smaller than that obtained with Caputo and Caputo-Fabrizio fractional derivatives. Therefore, Atangana-Baleanu fractional derivative is the best choice to obtain controlled velocity.

This work aims to investigate the generation of heat by dissipation of mechanical energy in particulate flows. The behavior of material in a rotating drum is considered in experimental and numerical analyses. In the physical experiments, the temperature of the particles inside the drum was monitored by means of infrared thermography and the influence of rotation speed and filling ratio was explored. The experimental data were later used to calibrate numerical simulations using the Discrete Element Method (DEM). The numerical results were then analyzed to gain more insights into the mechanisms of heat generation., This project is funded by the Marie SKŁODOWSKA-CURIE Innovative Training Network MATHEGRAM, the People Programme (Marie SKŁODOWSKA-CURIE Actions) of the European Union’s Horizon 2020 Programme H2020 under REA grant agreement No. 813202., Postprint (published version)

The objective of this paper is to analyze the influence of heat absorption/generation and mass diffusion on magnetohydrodynamics(MHD) Jeffrey fluid flow over a perpendicular plate moving exponentially immersed in a porous media. The Newtonian heating condition are udes for the fluid motion. The impact of thermal radiation is used in the energy equation. The two types of magnetic field have been evaluated. The main purpose of present work is to acquire the analytical solution with the help of Atangana-Baleanu (AB), Caputo, and Caputo-Fabrizio fractional derivatives. We have drawn a graphical comparison between the solutions of these three types of fractional models of jeffery fluid. Graphs of different parameters have been also plotted using MathCad software. Furthermore, comparison among ordinary and fractionalized velocity fields are made to observe the impact of fractional parameter . It is clear from graph that velocity obtained with ordinary derivative is higher than that obtained with fractional derivatives. It is also found that velocity obtained with Atangana-Baleanu (AB) fractional derivative is smaller than that obtained with Caputo and Caputo-Fabrizio fractional derivatives. Therefore, Atangana-Baleanu fractional derivative is the best choice to obtain controlled velocity.

The influence of friction stir welding parameters on thermo-mechanical behav-ior of the material during welding is analyzed. An aluminum alloy is considered (Al 2024 T351), and different rotating and welding speeds are applied. The finite element model consists of the working plate (Al alloy), backing plate and welding tool. The influence of the welding conditions on material behavior is taken into account the application of the Johnson-Cook material model. The rotation speed of the tool affects the results. If increased, it contributes to an increase of friction-gen-erated heat intensity. The other component of the generated heat, which stems from the plastic deformation of the material, is negligibly changed. When the welding speed, i.e. tool translation speed, is increased, the intensity of friction-generated heat decreases, while the heat generation due to plastic deforming is becoming more pronounced. Summed, this leads to rather small change of the total genera-tion. The changes of the heat generation influence both the temperature field and reaction force. Also, the inadequate selection of welding parameters resulted in occurrence of the defects (pores) in the model.

In the new age of illumination, light emitting diodes (LEDs) have been proven to be the most efficient alternative to conventional light sources. Yet, in comparison to other lighting systems, LEDs operate at low temperatures while junction temperature (Tj) is is among the main factors dictating their lifespan, reliability, and performance. This indicates that accurate measurement of LED temperature is of great importance to better understand the thermal effects over a system and improve performance. Over the years, various Tj measurement techniques have been developed, and existing methods have been improved in many ways with technological and scientific advancements. Correspondingly, in order to address the governing phenomena, benefits, drawbacks, possibilities, and applications, a wide range of measurement techniques and systems are covered. This paper comprises a large number of published studies on junction temperature measurement approaches for LEDs, and a summary of the experimental parameters employed in the literature are given as a reference. In addition, some of the corrections noted in non-ideal thermal calibration processes are discussed and presented. Finally, a comparison between methods will provide the readers a better insight into the topic and direction for future research.

The influence of friction stir welding parameters on thermo-mechanical behavior of the material during welding is analyzed. An aluminum alloy is considered (Al 2024 T351), and different rotating and welding speeds are applied. The finite element model consists of the working plate (Al alloy), backing plate and welding tool. The influence of the welding conditions on material behavior is taken into account the application of the Johnson-Cook material model. The rotation speed of the tool affects the results. If increased, it contributes to an increase of friction-generated heat intensity. The other component of the generated heat, which stems from the plastic deformation of the material, is negligibly changed. When the welding speed, i.e. tool translation speed, is increased, the intensity of friction-generated heat decreases, while the heat generation due to plastic deforming is becoming more pronounced. Summed, this leads to rather small change of the total generation. The changes of the heat generation influence both the temperature field and reaction force. Also, the inadequate selection of welding parameters resulted in occurrence of the defects (pores) in the model.

The influence of friction stir welding parameters on thermo-mechanical behavior of the material during welding is analyzed. An aluminum alloy is considered (Al 2024 T351), and different rotating and welding speeds are applied. The finite element model consists of the working plate (Al alloy), backing plate and welding tool. The influence of the welding conditions on material behavior is taken into account the application of the Johnson-Cook material model. The rotation speed of the tool affects the results. If increased, it contributes to an increase of friction-generated heat intensity. The other component of the generated heat, which stems from the plastic deformation of the material, is negligibly changed. When the welding speed, i.e. tool translation speed, is increased, the intensity of friction-generated heat decreases, while the heat generation due to plastic deforming is becoming more pronounced. Summed, this leads to rather small change of the total generation. The changes of the heat generation influence both the temperature field and reaction force. Also, the inadequate selection of welding parameters resulted in occurrence of the defects (pores) in the model.

The objective of this paper is to analyze the influence of heat absorption/generation and mass diffusion on magnetohydrodynamics(MHD) Jeffrey fluid flow over a perpendicular plate moving exponentially immersed in a porous media. The Newtonian heating condition are udes for the fluid motion. The impact of thermal radiation is used in the energy equation. The two types of magnetic field have been evaluated. The main purpose of present work is to acquire the analytical solution with the help of Atangana-Baleanu (AB), Caputo, and Caputo-Fabrizio fractional derivatives. We have drawn a graphical comparison between the solutions of these three types of fractional models of jeffery fluid. Graphs of different parameters have been also plotted using MathCad software. Furthermore, comparison among ordinary and fractionalized velocity fields are made to observe the impact of fractional parameter . It is clear from graph that velocity obtained with ordinary derivative is higher than that obtained with fractional derivatives. It is also found that velocity obtained with Atangana-Baleanu (AB) fractional derivative is smaller than that obtained with Caputo and Caputo-Fabrizio fractional derivatives. Therefore, Atangana-Baleanu fractional derivative is the best choice to obtain controlled velocity.

An energy transition is needed in order to combat climate change. With the rise of intermittent renewable energy, a need for energy storage is also inevitable. Carbon dioxide electrolysis is a potential solution as CO2 emissions can be recycled and subsequently converted for energy storage. However, the technology is rather new and research has yet to be conducted in this field. An important aspect is the temperature within an electrochemical cell, especially when scaling up. An increase in temperature can benefit the performance of the cell, but it also has downsides. Hot-spot formation with non-uniform reaction kinetics and thermal sensible components can have a great influence on the life-time of the cell. For that reason, a modeling study on the heat generation within carbon dioxide electrolysis systems is done. Different volumetric gas flow rates of carbon dioxide have been considered for two geometries: the membrane electrode assembly (MEA) and the gas diffusion electrode (GDE). The model considers three separate models: a mass model, electrochemical model and thermal model, and operates at a fixed current. The finite difference method is applied using Python 3.0 to solve the relevant conservation equations. Furthermore, the model includes different material layers, where the materials and dimensions are based on recently done experiments. The model showed that irreversible losses caused by the activation overpotentials are the biggest contributor to the total heat generation. Reversible heat also contributes to the heat generation, where heat is required in the anode and heat is generated in the cathode. Furthermore, within the cathodic catalyst layer most heat is generated. Joule heating caused by ohmic losses has proven to have negligibly impact on the total heat generation. As a result, the hot-spot is located within the cathodic catalyst layer for both geometries. Due to the additional electrolyte in the

In the coming years, the use of high-strength concrete is estimated to increase rapidly, with a substantial impact on the economy and the development of sustainable concrete technology. The use of fly ash (FA) as a partial replacement of Portland cement in high strength concrete is a most important topic because the use of FA not only benefits the economy, environmental aspects but also improves the properties of the concrete. In this study, the properties of high strength concrete (HSC) with FA was compared to HSC without FA. Workability, compressive strength, autogenous shrinkage, temperature rise, chloride penetration, and carbonation resistance were tested on nine HSC mixtures. The test results reveal that using FA in HSC mixture significantly enhances many properties when compared to mixtures containing only silica fume (SF) or mixtures with the combination of both SF and ground granulated blast furnace slag (GGBS). Its viscosity decreased while solid volume concentration increased, particularly in the ternary binder mixtures containing 20% FA and 10% SF. Combining 20% FA with 7% SF in the HSC reduces the peak temperature measured by the semi-adiabatic temperature rise test, and is equivalent to the HSC mixture with 20% FA or mixture with combined 30% GGBS and 7% SF. Concrete mixtures comprising 20% FA and SF show slightly lower 28-day compressive strength than the SF-only mixture, but their 91-day compressive strengths are equivalent to those of the SF-only mixtures. Due to the improved microstructures, all HSC mixtures perform well in terms of carbonation and rapid chloride permeability, particularly the ternary binder mixtures. The effects of FA on HSC properties were further investigated using WPD, SEM, XRD, and SP dosage to reveal the mechanical characteristics. Although 30% GGBS showed better performance compared to 20% FA in term of compressive strength, utilizing FA in HSC improved concrete performance in terms of viscosity, autogenous shrinkage, heat g

In the coming years, the use of high-strength concrete is estimated to increase rapidly, with a substantial impact on the economy and the development of sustainable concrete technology. The use of fly ash (FA) as a partial replacement of Portland cement in high strength concrete is a most important topic because the use of FA not only benefits the economy, environmental aspects but also improves the properties of the concrete. In this study, the properties of high strength concrete (HSC) with FA was compared to HSC without FA. Workability, compressive strength, autogenous shrinkage, temperature rise, chloride penetration, and carbonation resistance were tested on nine HSC mixtures. The test results reveal that using FA in HSC mixture significantly enhances many properties when compared to mixtures containing only silica fume (SF) or mixtures with the combination of both SF and ground granulated blast furnace slag (GGBS). Its viscosity decreased while solid volume concentration increased, particularly in the ternary binder mixtures containing 20% FA and 10% SF. Combining 20% FA with 7% SF in the HSC reduces the peak temperature measured by the semi-adiabatic temperature rise test, and is equivalent to the HSC mixture with 20% FA or mixture with combined 30% GGBS and 7% SF. Concrete mixtures comprising 20% FA and SF show slightly lower 28-day compressive strength than the SF-only mixture, but their 91-day compressive strengths are equivalent to those of the SF-only mixtures. Due to the improved microstructures, all HSC mixtures perform well in terms of carbonation and rapid chloride permeability, particularly the ternary binder mixtures. The effects of FA on HSC properties were further investigated using WPD, SEM, XRD, and SP dosage to reveal the mechanical characteristics. Although 30% GGBS showed better performance compared to 20% FA in term of compressive strength, utilizing FA in HSC improved concrete performance in terms of viscosity, autogenous shrinkage, heat g

In the coming years, the use of high-strength concrete is estimated to increase rapidly, with a substantial impact on the economy and the development of sustainable concrete technology. The use of fly ash (FA) as a partial replacement of Portland cement in high strength concrete is a most important topic because the use of FA not only benefits the economy, environmental aspects but also improves the properties of the concrete. In this study, the properties of high strength concrete (HSC) with FA was compared to HSC without FA. Workability, compressive strength, autogenous shrinkage, temperature rise, chloride penetration, and carbonation resistance were tested on nine HSC mixtures. The test results reveal that using FA in HSC mixture significantly enhances many properties when compared to mixtures containing only silica fume (SF) or mixtures with the combination of both SF and ground granulated blast furnace slag (GGBS). Its viscosity decreased while solid volume concentration increased, particularly in the ternary binder mixtures containing 20% FA and 10% SF. Combining 20% FA with 7% SF in the HSC reduces the peak temperature measured by the semi-adiabatic temperature rise test, and is equivalent to the HSC mixture with 20% FA or mixture with combined 30% GGBS and 7% SF. Concrete mixtures comprising 20% FA and SF show slightly lower 28-day compressive strength than the SF-only mixture, but their 91-day compressive strengths are equivalent to those of the SF-only mixtures. Due to the improved microstructures, all HSC mixtures perform well in terms of carbonation and rapid chloride permeability, particularly the ternary binder mixtures. The effects of FA on HSC properties were further investigated using WPD, SEM, XRD, and SP dosage to reveal the mechanical characteristics. Although 30% GGBS showed better performance compared to 20% FA in term of compressive strength, utilizing FA in HSC improved concrete performance in terms of viscosity, autogenous shrinkage, heat g

Background: Drilling speed during osteotomy in implant site preparation is an important factor that affects heat generation, cell vitality and primary stability and consequently Osseointegration of the implant. A thorough understanding of this impact is important for taking suitable precautions for successful dental rehabilitation. Aim: The objective of this study is to review the available literature regarding the impact of drilling speed on heat generation and other related parameters that influence the success of dental implants. Material and Methods: Suitable research papers relevant for study were identified through electronic database of available dental literature in PubMed and MEDLINE for all articles published till February, 2021. Peer-reviewed dental and PubMed indexed journals were selected. Search was done using certain relevant key words and terms. Results: The initial search revealed a total of 281 articles which were then screened and a total of 61 articles were selected based on the inclusion criteria. Focus was laid on the studies related to drilling speed and its impact on osseointegration, heat generation during osteotomy, drilling speed and bone viability, drilling speed and primary stability of implant and particle size of the bone collected. Heat generation during implant placement is affected by multiple factors with drilling speed being one of them. Conclusion: Researchers have reached contradictory conclusions regarding the impact of drilling speed on heat generation during osteotomy and other parameters. However, studies in the recent past are favoring low speed drilling owing to the advantage of perfect control of the drilling depth and the possibility of collection of a considerable amount of viable granular bone grafts during the procedure.

An energy transition is needed in order to combat climate change. With the rise of intermittent renewable energy, a need for energy storage is also inevitable. Carbon dioxide electrolysis is a potential solution as CO2 emissions can be recycled and subsequently converted for energy storage. However, the technology is rather new and research has yet to be conducted in this field. An important aspect is the temperature within an electrochemical cell, especially when scaling up. An increase in temperature can benefit the performance of the cell, but it also has downsides. Hot-spot formation with non-uniform reaction kinetics and thermal sensible components can have a great influence on the life-time of the cell. For that reason, a modeling study on the heat generation within carbon dioxide electrolysis systems is done. Different volumetric gas flow rates of carbon dioxide have been considered for two geometries: the membrane electrode assembly (MEA) and the gas diffusion electrode (GDE). The model considers three separate models: a mass model, electrochemical model and thermal model, and operates at a fixed current. The finite difference method is applied using Python 3.0 to solve the relevant conservation equations. Furthermore, the model includes different material layers, where the materials and dimensions are based on recently done experiments. The model showed that irreversible losses caused by the activation overpotentials are the biggest contributor to the total heat generation. Reversible heat also contributes to the heat generation, where heat is required in the anode and heat is generated in the cathode. Furthermore, within the cathodic catalyst layer most heat is generated. Joule heating caused by ohmic losses has proven to have negligibly impact on the total heat generation. As a result, the hot-spot is located within the cathodic catalyst layer for both geometries. Due to the additional electrolyte in the

In the coming years, the use of high-strength concrete is estimated to increase rapidly, with a substantial impact on the economy and the development of sustainable concrete technology. The use of fly ash (FA) as a partial replacement of Portland cement in high strength concrete is a most important topic because the use of FA not only benefits the economy, environmental aspects but also improves the properties of the concrete. In this study, the properties of high strength concrete (HSC) with FA was compared to HSC without FA. Workability, compressive strength, autogenous shrinkage, temperature rise, chloride penetration, and carbonation resistance were tested on nine HSC mixtures. The test results reveal that using FA in HSC mixture significantly enhances many properties when compared to mixtures containing only silica fume (SF) or mixtures with the combination of both SF and ground granulated blast furnace slag (GGBS). Its viscosity decreased while solid volume concentration increased, particularly in the ternary binder mixtures containing 20% FA and 10% SF. Combining 20% FA with 7% SF in the HSC reduces the peak temperature measured by the semi-adiabatic temperature rise test, and is equivalent to the HSC mixture with 20% FA or mixture with combined 30% GGBS and 7% SF. Concrete mixtures comprising 20% FA and SF show slightly lower 28-day compressive strength than the SF-only mixture, but their 91-day compressive strengths are equivalent to those of the SF-only mixtures. Due to the improved microstructures, all HSC mixtures perform well in terms of carbonation and rapid chloride permeability, particularly the ternary binder mixtures. The effects of FA on HSC properties were further investigated using WPD, SEM, XRD, and SP dosage to reveal the mechanical characteristics. Although 30% GGBS showed better performance compared to 20% FA in term of compressive strength, utilizing FA in HSC improved concrete performance in terms of viscosity, autogenous shrinkage, heat g

Thermal management system (TMS) for commonly used lithium-ion (Li-ion) batteries is an essential requirement in electric vehicle operation due to the excessive heat generation of these batteries during fast charging/discharging. In the current study, a thermal model of lithium-titanate (LTO) cell and three cooling strategies comprising natural air cooling, forced fluid cooling, and a flat heat pipe-assisted method is proposed experimentally. A new thermal analysis of the single battery cell is conducted to identify the most critical zone of the cell in terms of heat generation. This analysis allowed us to maximize heat dissipation with only one heat pipe mounted on the vital region. For further evaluation of the proposed strategies, a computational fluid dynamic (CFD) model is built in COMSOL Multiphysics® and validated with surface temperature profile along the heat pipe and cell. For real applications, a numerical optimization computation is also conducted in the module level to investigate the cooling capacity of the liquid cooling system and liquid cooling system embedded heat pipe (LCHP). The results show that the single heat pipe provided up to 29.1% of the required cooling load in the 8C discharging rate. Moreover, in the module level, the liquid cooling system and LCHP show better performance compared with natural air cooling while reducing the module temperature by 29.9% and 32.6%, respectively., QC 20201230

Aufgrund von zunehmend schlankeren Bauwerken nimmt der dynamische Beanspruchungsanteil gegenüber dem Anteil der ständigen Beanspruchungen bei Brückenbauwerken und Windenergieanlagen zu. Daraus ergibt sich ein großer Forschungsbedarf im Bereich der Betonermüdung. Im Rahmen dieser Arbeit werden kraftgeregelte Druckschwellversuche energetisch ausgewertet. Aus den Spannungs-Dehnungslinien lassen sich dabei neben einem elastischen und plastischen Energieanteil ebenfalls die Dissipationsenergiewerte bestimmen. Diese Dissipationsenergie ist wiederum für die Erwärmung der Probekörper infolge der zyklisch-mechanischen Beanspruchung verantwortlich. Auf Basis der festgestellten Korrelation zwischen der Probekörpererwärmung und der Schädigungsentwicklung werden die Hypothesen, die einen Zusammenhang zwischen der Dissipationsenergie und der Rissanzahl sowie der Rissgröße im Probekörper beschreiben, untersucht. Es zeigt sich, dass sich die Verläufe der mit jedem Lastwechsel dissipierten Energie analog zu den bereits bekannten Verläufen anderer Messparameter und Schädigungsindikatoren in drei Phasen aufteilen lassen. Ein direkter quantitativer Zusammenhang zwischen dem Schädigungsgrad und der Dissipationsenergie je Lastwechsel ist hingegen nicht erkennbar. Aus der Auswertung der bis zum Versagen eines Probekörpers kumulierten Dissipationsenergie resultiert hingegen ein funktionaler Zusammenhang zur jeweiligen Bruchlastwechselzahl. Sämtliche Auswertungspunkte, die durch die Bruchlastwechselzahlen und den bis zum jeweiligen Versagen kumulierten Dissipationsenergiewerten beschrieben werden, liegen auf einer Kurve. Diese lässt sich durch eine Potenzfunktion beschreiben und wird als Versagenskurve bezeichnet. Die Gültigkeit der Versagenskurven wird durch die Auswertung weiterer Versuchsserien validiert. Dabei ergeben sich aus der Form der Versagenskurve Rückschlüsse auf das Ermüdungsverhalten der Versuchsserie. Aufbauend auf den Versagenskurven wird in dieser Arbeit ein neuer Schädigun

Brush seals have been extensively studied for the last thirty years as an advanced sealing solution for gas turbine engines. The research is always aimed towards the reduction of the leakage flow, that has direct repercussions on the specific fuel consumption, the thrust-to-weight ratio, and the emission of pollutants. In addition, the sealing device must cope with side effects related to higher interface speeds, rotordynamics issues, or durability. Brush seals main assets are their excellent leakage performance with low friction properties compared to other contact seals like lip seals, and their ability to withstand rotor radial excursion without permanent damage. However, proper design optimization cannot be performed without the inclusion of the tribological performance. This paper presents a parametric investigation of the friction properties of carbon fibre brush seals as a function of the fibre pack geometry and the rotational speed. Carbon fibre and commonly used metallic brush seals present fundamentally different behaviour in presence of differential pressure or rotational speed. This paper also proposes an alternative method to predict the brush seal torque, based on measurements with a torque sensor. Heat generation was also evaluated with a thermographic camera. Both methods ensured consistency between results., SCOPUS: ar.j, info:eu-repo/semantics/published

Aufgrund von zunehmend schlankeren Bauwerken nimmt der dynamische Beanspruchungsanteil gegenüber dem Anteil der ständigen Beanspruchungen bei Brückenbauwerken und Windenergieanlagen zu. Daraus ergibt sich ein großer Forschungsbedarf im Bereich der Betonermüdung. Im Rahmen dieser Arbeit werden kraftgeregelte Druckschwellversuche energetisch ausgewertet. Aus den Spannungs-Dehnungslinien lassen sich dabei neben einem elastischen und plastischen Energieanteil ebenfalls die Dissipationsenergiewerte bestimmen. Diese Dissipationsenergie ist wiederum für die Erwärmung der Probekörper infolge der zyklisch-mechanischen Beanspruchung verantwortlich. Auf Basis der festgestellten Korrelation zwischen der Probekörpererwärmung und der Schädigungsentwicklung werden die Hypothesen, die einen Zusammenhang zwischen der Dissipationsenergie und der Rissanzahl sowie der Rissgröße im Probekörper beschreiben, untersucht. Es zeigt sich, dass sich die Verläufe der mit jedem Lastwechsel dissipierten Energie analog zu den bereits bekannten Verläufen anderer Messparameter und Schädigungsindikatoren in drei Phasen aufteilen lassen. Ein direkter quantitativer Zusammenhang zwischen dem Schädigungsgrad und der Dissipationsenergie je Lastwechsel ist hingegen nicht erkennbar. Aus der Auswertung der bis zum Versagen eines Probekörpers kumulierten Dissipationsenergie resultiert hingegen ein funktionaler Zusammenhang zur jeweiligen Bruchlastwechselzahl. Sämtliche Auswertungspunkte, die durch die Bruchlastwechselzahlen und den bis zum jeweiligen Versagen kumulierten Dissipationsenergiewerten beschrieben werden, liegen auf einer Kurve. Diese lässt sich durch eine Potenzfunktion beschreiben und wird als Versagenskurve bezeichnet. Die Gültigkeit der Versagenskurven wird durch die Auswertung weiterer Versuchsserien validiert. Dabei ergeben sich aus der Form der Versagenskurve Rückschlüsse auf das Ermüdungsverhalten der Versuchsserie. Aufbauend auf den Versagenskurven wird in dieser Arbeit ein neuer Schädigun

Теплогенерация на основе древесного топлива повышает энергоэффективность в лесопромышленном производстве. Древесное топливо является возобновимым и экологичным ресурсом и рассматривается как эффективная замена топливу из ископаемых ресурсов. Применение нормированных видов древесного топлива позволяет снизить затраты на теплогенерацию. Древесное топливо имеет самые низкие показатели выделения углекислого газа, а также отсутствие серы при сгорании, что обеспечивает экологичность применения данного вида топлива. Важными организационными мероприятиями по переходу на древесные виды топлива являются создание унифицированных муниципальных топливно-технологических терминалов, расширение производства топливной щепы при рубках ухода, а также экспорт избыточной топливной щепы. Эти мероприятия позволяют увеличить количество высокопроизводительных рабочих мест., Heat generation based on wood fuel increases energy effi ciency in the timber industry. Wood fuel is a renewable and environmentally friendly resource and is seen as an effective substitute for fossil fuels. The use of standardized types of wood fuel can reduce the cost of heat generation. Wood fuel has the lowest rates of carbon dioxide emissions, as well as the absence of sulfur during combustion, which ensures environmental friendliness of this type of fuel. Important organizational measures for the transition to wood fuels are the creation of unifi ed municipal fuel technology terminals, the expansion of the production of fuel chips during logging operations, as well as the export of excess fuel chips. These activities increase the number of high-performance jobs.

Electrochemical capacitors (ECs) serve as promising electrical energy storage systems due to their potential to achieve both high energy and high power densities. ECs are usually cycled at high current densities resulting in significant amount of volumetric heat generation. This, in turn, may lead to excessive temperature rise that can reduce their lifetime and performance. This dissertation aims to experimentally measure the heat generation rate at electrodes of ECs with different electrodes materials under various charging and discharging conditions.First, the design, fabrication, and validation of an in operando calorimeter are presented. The in operando calorimeter was able to measure the heat generation rate in each electrode of the EC cell separately. First, EDLC cells consisted of two typical activated carbon (AC) electrodes were investigated. The irreversible heat generation rate in each electrode was in excellent agreement with predictions for Joule heating. The reversible heat generation rate in the positive electrode was exothermic during charging and endothermic during discharging. By contrast, the negative electrode featured both exothermic and endothermic heat generation during both charging and discharging steps. Such asymmetric heating was attributed to asymmetry in the charging mechanism due to the overscreening effect caused by interactions between the anionic functional groups of carboxymethyl cellulose (CMC) binder and the cations at the negative electrode. Second, the effect of potential window on heat generation rate in EDLCs in ionic liquid electrolyte was investigated under galvanostatic cycling. The irreversible heat generation rate increased with increasing the potential window and exceeded Joule heating. This could be attributed to the effect of potential-dependent pore resistance. In addition, a further increase in the irreversible heat generation rate was observed at high potential window due to electrolyte degradation. The reversible he

Municipal solid waste (MSW) in landfills can reach temperatures greater than 50°C that may be sustained for several decades due to methanogenic bacterial activity. The generated heat is an alternative energy source that can be exploited for direct heating of nearby infrastructure or for augmenting industrial processes. However, the proper design of heat extraction systems for landfills requires in-situ measurements of MSW thermal properties and knowledge of the process of heat generation within the waste. Accordingly, the main objective of this study is to understand the processes governing heat generation and heat extraction in MSW and to characterize the thermal properties of the waste. To reach this objective a new MSW landfill cell at the Sycamore Landfill in Santee, California was instrumented with temperature sensors and geothermal heat exchangers, installed at three different elevations in the cell during waste placement. The spatial and temporal evolution of the waste temperature was monitored during 13 months of a self-heating period, followed by a 17-day heat extraction thermal response test, and lastly, a 3-month temperature recovery period. The data collected during the monitoring was analyzed using three different methods of increasing complexity: an infinite line source analysis, a two-dimensional inverse analysis using a finite difference model with simplified heat transfer boundary conditions, and a three-dimensional inverse analysis using a finite element model for heat transfer and nonisothermal pipe flow. The estimated values of in-situ thermal conductivity and thermal diffusivity of the MSW were consistent with values on the higher range of those obtained from laboratory tests on MSW reported in the literature. The data also suggests a dependence of the heat generation rate on the temperature of the surrounding waste, similar to that observed for methanogenic bacterial activity. The experimental and simulation results constitute the basis for the

One of the main aspects which governs the size of ventilation facilities in underground mines is the amount of heat load generated in the underground environment. This heat load comes from many different sources, one of which is the heat contributed by underground diesel machinery operation. One strategy to mitigate the heat and other emissions from such equipment is to substitute these units to similar performance, but more thermally efficient, electric machinery. This study presents a heat load evaluation of the Lithium-iron Phosphate battery system used in a prototype electric mining vehicle. The set of equations which governs the heat generation from these devices have been developed by previous researchers and is used in this thesis to calculate the heat generation and loss. However, in the mining industry, the current methodology for heat load calculation from electric vehicles (EVs) is usually based on the rated power or on a simple power loss equation. This strategy might lead to incorrect estimations of the heat load from this type of machinery. Experimental and simulation work has been conducted as a means to evaluate the heat flux from the Lithium-iron Phosphate battery system. The battery was tested through charging and discharging it under different levels of current within the 10% to 90% range of its maximum capacity. The test was performed firstly with a single cell and then with a module. Furthermore, the battery system was set in operation under different environment temperature settings. These current and temperature levels represent the range of possible conditions in which the prototype will face in service. Through the estimation of the heat released from the other main electrical components in the vehicle, it was possible to calculate the heat impact of these units in the surrounding environment.

Electrochemical capacitors (ECs) serve as promising electrical energy storage systems due to their potential to achieve both high energy and high power densities. ECs are usually cycled at high current densities resulting in significant amount of volumetric heat generation. This, in turn, may lead to excessive temperature rise that can reduce their lifetime and performance. This dissertation aims to experimentally measure the heat generation rate at electrodes of ECs with different electrodes materials under various charging and discharging conditions.First, the design, fabrication, and validation of an in operando calorimeter are presented. The in operando calorimeter was able to measure the heat generation rate in each electrode of the EC cell separately. First, EDLC cells consisted of two typical activated carbon (AC) electrodes were investigated. The irreversible heat generation rate in each electrode was in excellent agreement with predictions for Joule heating. The reversible heat generation rate in the positive electrode was exothermic during charging and endothermic during discharging. By contrast, the negative electrode featured both exothermic and endothermic heat generation during both charging and discharging steps. Such asymmetric heating was attributed to asymmetry in the charging mechanism due to the overscreening effect caused by interactions between the anionic functional groups of carboxymethyl cellulose (CMC) binder and the cations at the negative electrode. Second, the effect of potential window on heat generation rate in EDLCs in ionic liquid electrolyte was investigated under galvanostatic cycling. The irreversible heat generation rate increased with increasing the potential window and exceeded Joule heating. This could be attributed to the effect of potential-dependent pore resistance. In addition, a further increase in the irreversible heat generation rate was observed at high potential window due to electrolyte degradation. The reversible he

Municipal solid waste (MSW) in landfills can reach temperatures greater than 50°C that may be sustained for several decades due to methanogenic bacterial activity. The generated heat is an alternative energy source that can be exploited for direct heating of nearby infrastructure or for augmenting industrial processes. However, the proper design of heat extraction systems for landfills requires in-situ measurements of MSW thermal properties and knowledge of the process of heat generation within the waste. Accordingly, the main objective of this study is to understand the processes governing heat generation and heat extraction in MSW and to characterize the thermal properties of the waste. To reach this objective a new MSW landfill cell at the Sycamore Landfill in Santee, California was instrumented with temperature sensors and geothermal heat exchangers, installed at three different elevations in the cell during waste placement. The spatial and temporal evolution of the waste temperature was monitored during 13 months of a self-heating period, followed by a 17-day heat extraction thermal response test, and lastly, a 3-month temperature recovery period. The data collected during the monitoring was analyzed using three different methods of increasing complexity: an infinite line source analysis, a two-dimensional inverse analysis using a finite difference model with simplified heat transfer boundary conditions, and a three-dimensional inverse analysis using a finite element model for heat transfer and nonisothermal pipe flow. The estimated values of in-situ thermal conductivity and thermal diffusivity of the MSW were consistent with values on the higher range of those obtained from laboratory tests on MSW reported in the literature. The data also suggests a dependence of the heat generation rate on the temperature of the surrounding waste, similar to that observed for methanogenic bacterial activity. The experimental and simulation results constitute the basis for the

One of the main aspects which governs the size of ventilation facilities in underground mines is the amount of heat load generated in the underground environment. This heat load comes from many different sources, one of which is the heat contributed by underground diesel machinery operation. One strategy to mitigate the heat and other emissions from such equipment is to substitute these units to similar performance, but more thermally efficient, electric machinery. This study presents a heat load evaluation of the Lithium-iron Phosphate battery system used in a prototype electric mining vehicle. The set of equations which governs the heat generation from these devices have been developed by previous researchers and is used in this thesis to calculate the heat generation and loss. However, in the mining industry, the current methodology for heat load calculation from electric vehicles (EVs) is usually based on the rated power or on a simple power loss equation. This strategy might lead to incorrect estimations of the heat load from this type of machinery. Experimental and simulation work has been conducted as a means to evaluate the heat flux from the Lithium-iron Phosphate battery system. The battery was tested through charging and discharging it under different levels of current within the 10% to 90% range of its maximum capacity. The test was performed firstly with a single cell and then with a module. Furthermore, the battery system was set in operation under different environment temperature settings. These current and temperature levels represent the range of possible conditions in which the prototype will face in service. Through the estimation of the heat released from the other main electrical components in the vehicle, it was possible to calculate the heat impact of these units in the surrounding environment.

Nanocomposites of magnetite (Fe3O4) and reduced graphene oxide (rGO) generate heat under an alternating magnetic field and therefore have potential applications as thermoseeds for cancer hyperthermia treatment. However, the properties of such nanocomposites as biomaterials have not been sufficiently well characterized. In this study, the osteoconductivity of Fe3O4-rGO nanocomposites of various compositions was evaluated in vitro in terms of their apatite-forming ability in simulated body fluid (SBF). Furthermore, the heat generation of the nanocomposites was measured under an alternating magnetic field. The apatite-forming ability in SBF improved as the Fe3O4 content in the nanocomposite was increased. As the Fe3O4 content was increased, the nanocomposite not only rapidly raised the surrounding temperature to approximately 100°C, but the specific absorption rate also increased. We assumed that the ionic interaction between the Fe3O4 and rGO was enhanced and that Brown relaxation was suppressed as the proportion of rGO in the nanocomposite was increased. Consequently, a high content of Fe3O4 in the nanocomposite was effective for improving both the osteoconductivity and heat generation characteristics for hyperthermia applications.

The main purpose of this study was to examine the difference in intrapulpal temperature (IPT) comparing a “grinding” and a “cutting” technique during single crown preparation. The difference in preparation time between the two techniques was also examined. A thermocouple was placed in the pulp chamber of 20 extracted human permanent molar teeth. The teeth were placed in a silicone model. The model was immersed in a thermostatically controlled water bath with a temperature of 37 degrees centigrade (°C), and with a water level reaching the cementoenamel junction at the teeth. For both preparation techniques an electric handpiece (NSK Ti-Max Ti85L 1:5) was used. A diamond bur was used for the “grinding” and a carbide bur for the “cutting” technique. The IPT during preparation was measured with a K-thermocouple connected to Testo 176 T4 temperature data logger. There was a significant difference in IPT rise between the two techniques for preparing the teeth. The “cutting” technique showed a higher mean temperature, 31.9 °C, compared to the “grinding”, 29.5 °C (p<0.05). Neither reached the critical value of 5.5 °C IPT increase. The “grinding” technique averaged a longer preparation time of 106 seconds per tooth than the “cutting” technique (p<0.05). Our study shows that the “cutting” technique results in a higher mean temperature but that both preparation techniques can be considered as safe in regard to IPT during single crown preparation as long as sufficient water cooling is applied.

The main purpose of this study was to examine the difference in intrapulpal temperature (IPT) comparing a “grinding” and a “cutting” technique during single crown preparation. The difference in preparation time between the two techniques was also examined. A thermocouple was placed in the pulp chamber of 20 extracted human permanent molar teeth. The teeth were placed in a silicone model. The model was immersed in a thermostatically controlled water bath with a temperature of 37 degrees centigrade (°C), and with a water level reaching the cementoenamel junction at the teeth. For both preparation techniques an electric handpiece (NSK Ti-Max Ti85L 1:5) was used. A diamond bur was used for the “grinding” and a carbide bur for the “cutting” technique. The IPT during preparation was measured with a K-thermocouple connected to Testo 176 T4 temperature data logger. There was a significant difference in IPT rise between the two techniques for preparing the teeth. The “cutting” technique showed a higher mean temperature, 31.9 °C, compared to the “grinding”, 29.5 °C (p<0.05). Neither reached the critical value of 5.5 °C IPT increase. The “grinding” technique averaged a longer preparation time of 106 seconds per tooth than the “cutting” technique (p<0.05). Our study shows that the “cutting” technique results in a higher mean temperature but that both preparation techniques can be considered as safe in regard to IPT during single crown preparation as long as sufficient water cooling is applied.

A series of tests were carried out in the cavitation tunnel of the Laboratory for Water and Turbine Machines of the University of Ljubljana in order to investigate the effects of cavitation in the water heating process of closed loop pumping systems. For that, the water temperature was measured at the low pressure reservoir during runs of about 10 minutes. As expected, a constant temperature increase was observed which was proportional to the pump’s rotation speed. Then, the results obtained while keeping the same pump operating point and flow conditions with and without cavitation in the Venturi test section were compared. Surprisingly, it was found that the temperature increase rate was slightly higher when cavitation is present in the system. Moreover, the heat power was always higher than the hydraulic one for all the tests up to a certain cavitation level. However, this trend was inversed for higher cavitation numbers and lower hydraulic powers. Both results seem to prove that there is a clear influence of cavitation in heat generation process. Therefore, a new test rig will be built in Barcelona by the Spanish company Condorchem Envitech, S. L. with the help of Universitat Politècnica de Catalunya BarcelonaTech to continue the current research, Postprint (published version)

Vibrothermogrphy is a promising non-destructive technique that uses ultrasonic elastic waves to detect damages and is typically applied in the aerospace and automotive industries. This technique allows for defect selective imaging using thermal waves that are generated by ultrasound waves. In this paper, vibrothermography technique was applied to the aircraft fuselage to detect its damage. The influence of the damage on the temperature distribution at the damage region on the aluminum was investigated by finite element technique. Comprehensive understanding in edge crack in fuselage heating caused by local friction between crack surfaces was obtained.