Search

Developing affordable thermoelectric (TE) materials is critical for efficient waste heat recovery in industries. With the goal of developing novel, affordable TE materials, the present experimental–theoretical investigation, for the first time, presents a rigorous analysis of the electrical and thermal transport properties of a multi-principal-component AlCuFeMn alloy (MPCA). TE properties related to electronic transport, including the Seebeck coefficient, electrical conductivity, and thermal conductivity, were measured on a vacuum-cast sample and were computed using semi-classical Boltzmann transport theory. Additionally, ab initio calculations were performed to calculate the lattice thermal conductivity. The alloy demonstrated overall thermal conductivity of < 4 W/mK, comparable to conventional thermoelectric materials, while the computed lattice thermal conductivity was < 1 W/mK. Such low thermal conductivity may be attributed to the complex microstructure as well as the uniform distribution of aluminium in the matrix. The power factor of the alloy, however, was small (< 0.1 mW/mK2), translating to a low figure of merit (ZT ~ 0.01). Our study indicates that composition engineering can potentially improve the power factor and thus the overall TE response in an AlCuFeMn alloy. [ABSTRACT FROM AUTHOR]

The development of an innovative and highly efficient heat exchanger (HE) solution for gas–gas heat recovery is one of the major objectives of the HYDROSOL-beyond project which aims at enhancing the process efficiency for producing hydrogen from water dissociation with concentrated sunlight. Because of the very high temperature level of the process (up to 1400 °C), an innovative ceramic HE design was proposed with an integrated lattice structure, as secondary surface, to maximize the heat transfer. To assist the design of the HE, a multiscale approach was adopted: a 1D model based on global correlations was developed and a 3D computational fluid dynamics model of the secondary surfaces were generated. The former was applied to assess the performance of the entire HE; while, the latter was exploited to study in detail the thermo-fluid dynamics behavior of a HE core element and to provide the global correlations to be integrated into the 1D model. In this work, the effect of several parameters and operating conditions, namely, number of channels, number of lattice layers located into each channel, solid material exploited for the HE structure, parting plates thickness, heat transfer fluid velocity, radiation heat transfer and solid material emissivity, on the HE effectiveness are reported and accurately described. Furthermore, based upon the results obtained, guidelines on the HE design to maximize its performance are also provided. [ABSTRACT FROM AUTHOR]

Insufficient fresh air supply due to the increased air tightness of building envelopes after building renovations and window upgrades is a major concern of HVAC engineering today. The paper demonstrates the application of CFD simulations in the development of a compact decentralised ventilation unit with integrated heat recovery system for local ventilation of rooms, targeting this common issue. The device houses an innovative cyclically rotating recuperative heat exchanger, allowing effective condensate removal and de-icing in winter for its independent operation throughout the year. The paper introduces the ventilation unit, describes preparation of its numerical models, and conducts CFD simulation using Ansys Fluent software. The initial design of the device was improved following the findings of the numerical analysis, and the proposed adjustments were tested through follow-up CFD simulations, confirming that the desired outcomes were achieved. A separate CFD analysis was performed to assess the use of different air supply elements at the air outlet to the room, recommending the use of adjustable nozzles. A prototype ventilation unit was manufactured and the volume flow rate under different operating conditions was measured to be compared with the simulation results. The outcome of the research is a new type of compact local ventilation unit. An increase in device energy efficiency was achieved, with the aid of simulations, while maintaining its compact size. In addition to presenting the potential of using variant CFD analysis in the development of new HVAC equipment, the paper also indicates the drawbacks of using the Multiple Reference Frame (MRF) method to approximate the rotation of radial fan impellers in CFD simulations. [ABSTRACT FROM AUTHOR]

The article focuses on the issue of efficiently recovering waste heat from low-exergy process gases, which poses a significant challenge for improving energy efficiency in many industrial sectors. To address this problem, the application of a thermoelectric generator (TEG) has been proposed, allowing for the direct conversion of thermal energy into electrical energy. In the course of the research, experimental measurements were conducted for process gases at temperatures of 240 °C and 300 °C, along with CFD (computational fluid dynamics) simulations using Ansys Fluent 2023 R2 software. These simulations enabled the analysis of the temperature distribution in the TEG and the determination of the safe operating range of the device for process gas temperatures of 350 °C, 400 °C and 450 °C. The results obtained from both experiments and simulations demonstrated the effectiveness of the TEG in recovering waste heat from low-exergy gases. Additionally, these findings suggest the potential for scaling the solution to larger industrial systems, making TEG a promising technology for long-term sustainable development efforts. The developed numerical model proved to be a valuable tool in the design of TEG systems, allowing for the analysis and optimization of heat recovery systems. The innovation of the solution lies in the use of TEG for efficiently utilising waste heat from low-temperature gases, which holds significant potential for improving energy efficiency in processes where traditional energy recovery technologies are not effective. [ABSTRACT FROM AUTHOR]

Steam generating heat pump (SGHP) is a key technology for industrial decarbonization. For comprehensive evaluation of the feasibility and reliability of SGHP in different industrial sector, the work develops a thorough evaluation model for assessing the performance of SGHP by considering waste heat recovery, CO2 trading value, and pollutant emission cost, in addition to the conventional evaluation criteria. This work presents a thorough comparison of the thermodynamic performance and sustainability of various types of SGHPs across different industrial sector. Additionally, the conflicting relationships between the coefficient of performance (COP) and exergy efficiency are balanced through the application of the technique for order preference by similarity to ideal solution (TOPSIS). The results show that all the indexes of SGHP connected to an open heat pump (SGHPO) with different application scenarios are higher than those of SGHP connected to a flash tank (SGHPF). At the most unfavorable operating condition of the system, the COP minimum value is 1.31 and the exergy efficiency minimum value is 20.42%. These results indicate that replacing the coal-fired boiler with SGHP is feasible and the work could provide theoretical guidance for optimal design and equipment manufacture. Highlights: • A more comprehensive SGHP valuation model that takes into account the waste heat recovery, CO2 trading value, and pollutant emission cost is proposed. • The SGHPs are classified, compared, and analyzed comprehensively, with design and optimization recommendations provided. • Optimal balance between COP and exergy efficiency of a SGHP using the TOPSIS method. [ABSTRACT FROM AUTHOR]

In order to enhance the heat recovery efficiency and net energy consumption ratio of the run-around heat recovery system applied in gas and oil field and other buildings, this study replaces the conventional heat exchangers with wavy fin tube heat exchangers, slotted fin tube heat exchangers, and fin tube heat exchangers equipped with longitudinal vortex generators.The coupling simulation model of the run-around heat recovery system is established using MATLAB and FLUENT. The coupling model is utilized to simulate and calculate the heat recovery rate and net energy consumption ratio of the heat recovery system with different types of heat exchangers in various seasons, as well as at different temperatures during winter in a hot summer and cold winter region (Wuhan). The simulation results demonstrate a significant enhancement in the heat recovery rate and net energy consumption ratio of the heat recovery system when replacing the conventional heat exchanger with a finned tube heat exchanger incorporating corrugated fins, slotted fins, and longitudinal vortex generators.Among them, the heat recovery rate of the finned tube heat exchanger with slits exhibits the highest increase, while the net energy consumption ratio of the finned tube heat exchanger with longitudinal vortex generator demonstrates the most significant enhancement.The utilization of a finned tube heat exchanger with a complex structure can enhance the optimization of the run-around heat recovery system. However, when considering the overall energy consumption reduction capability of the entire system, it is essential to account for the increased energy consumption associated with its complex structure. [ABSTRACT FROM AUTHOR]

The future energy consumption of data centers is expected to be significant worldwide. From the perspective of carbon neutrality, designing 100 % renewable energy systems with distributed energy resources that can reliably supply energy to data centers is necessary. However, renewables' intrinsic uncontrollable characteristics make the stable energy supply challenging. Herein, we designed a 100 % renewable energy system by combining abundant but uncontrollable solar energy (e.g., photovoltaic (PV) cells) and controllable hydrogen (H2) energy systems (e.g., hydrogen microturbine and fuel cells) for a stable energy supply to an actual data center in South Korea. The hybrid system with on-site hydrogen production would be favorable after 2030 because of the expected decrease in green hydrogen prices and increase in carbon tax. Also, from sensitivity analyses, we found that the total NPC decreased by 75.2 % ($ 83.8M) with the green hydrogen price change from 14.5 $/kg to 3 $/kg. [ABSTRACT FROM AUTHOR]

The design integration of absorption and adsorption cooling systems is a recently emerging research field in which the inherent advantages of both these systems are intended to be combined so as to maximize system performance. However, a vast majority of the conventional integration approaches reported in the literature still suffer from the following drawbacks: (a) the inability to provide a continuous cooling effect of the integrated design during the switching period of the adsorption component, (b) the lack of incorporation of the mass/heat recovery cycles and its subsequent effects upon the integrated performance, and (c) the lack of functional dependence of all thermodynamic variables including heat capacities and adsorption enthalpy upon operational parameters such as temperature and pressure. This study presents the first attempt of a numerically validated performance prediction of such an integrated system with parallel functionality to facilitate a continuous cooling operation. An empirical model of mass recovery cycle has been formulated for the very first time which adequately describes the sorption dynamics during mass transfer. All thermodynamic variables have been expressed as functions of operational parameters during the cooling cycle. For a mean driving temperature predicted to be as low as 38 °C and a mean cycle time of 11.82 min, the proposed integrated design has been predicted to yield a cycle-averaged specific cooling power of 48.93 W kg−1 and a minimum achievable coefficient of performance of 0.74 compared to the corresponding values of 27.64 W kg−1 and 0.57 for the benchmark stand-alone silica gel/water adsorption chiller. [ABSTRACT FROM AUTHOR]

Development of efficient and reliable thermoelectric generators is vital for the sustainable utilization of energy, yet interfacial losses and failures between the thermoelectric materials and the electrodes pose a significant obstacle. Existing approaches typically rely on thermodynamic equilibrium to obtain effective interfacial barrier layers, which underestimates the critical factors of interfacial reaction and diffusion kinetics. Here, we develop a desirable barrier layer by leveraging the distinct chemical reaction activities and diffusion behaviors during sintering and operation. Titanium foil is identified as a suitable barrier layer for Mg3Sb2-based thermoelectric materials due to the creation of a highly reactive ternary MgTiSb metastable phase during sintering, which then transforms to stable binary Ti-Sb alloys during operation. Additionally, titanium foil is advantageous due to its dense structure, affordability, and ease of manufacturing. The interfacial contact resistivity reaches below 5 μΩ·cm2, resulting in a Mg3Sb2-based module efficiency of up to 11% at a temperature difference of 440 K, which exceeds that of most state-of-the-art medium-temperature thermoelectric modules. Furthermore, the robust Ti foil/Mg3(Sb,Bi)2 joints endow Mg3Sb2-based single-legs as well as modules with negligible degradation over long-term thermal cycles, thereby paving the way for efficient and sustainable waste heat recovery applications. The authors identify an ideal thermoelectric barrier layer by exploiting distinct chemical reaction activities and diffusion behaviors during sintering and operation, achieving 11% module efficiency at 723 K with enhanced long-term stability. [ABSTRACT FROM AUTHOR]

Anthropogenic climate change has significantly altered terrestrial and marine ecosystems globally, often in the form of climate-related events such as thermal anomalies and disease outbreaks. Although the isolated effects of these stressors have been well documented, a growing body of literature suggests that stressors often interact, resulting in complex effects on ecosystems. This includes coral reefs where sequential associations between heat stress and disease have had profound impacts. Here we used the model cnidarian Exaiptasia diaphana to investigate mechanisms linking prior heat stress to increased disease susceptibility. We examined anemone pathogen susceptibility and physiology (symbiosis, immunity, and energetics) following recovery from heat stress. We observed significantly increased pathogen susceptibility in anemones previously exposed to heat stress. Notably, prior heat stress reduced anemone energetic reserves (carbohydrate concentration), and activity of multiple immune components. Minimal effects of prior heat stress on symbiont density were observed. Together, results suggest changes in energetic availability might have the strongest effect on pathogen susceptibility and immunity following heat stress. The results presented here provide critical insight regarding the interplay between heat stress recovery and pathogen susceptibility in cnidarians and are an important first step towards understanding temporal associations between these stressors. The anemone Exaiptasia diaphana is more susceptible to pathogenic challenge following exposure to prior heat stress, even after two weeks of recovery at ambient temperatures. [ABSTRACT FROM AUTHOR]

Purpose: Our aim in this study was to examine lettuce production in vertical farming or in conventional greenhouse production in Northern European conditions from the perspective of climate change impact and environmental sustainability. Further, the goal was to identify practices and choices that could mitigate adverse effects and increase resource-use efficiency, allowing the development of more sustainable production systems. Methods: This article provides new information of the environmental impacts of lettuce production in greenhouses and vertical farming in Finland, compared using the life cycle assessment (LCA) methodology. The impact categories used were climate change impact, cumulative energy demand, resource use of fossil energy sources, resource use of minerals and metals, land use, and water scarcity. The system boundaries covered the production chains from cradle to farmgate, including inputs in production, as well as direct emissions caused by fertiliser use and the onsite composting of organic waste. The environmental impacts of the two production systems with different energy scenarios were assessed: (1) a greenhouse either with average or renewable energy; and (2) vertical farming either with average or renewable energy and with or without waste heat recovery. The data for vertical farming were based on one Finnish production site and supplementary data for the construction materials. The greenhouse data were based on a previous LCA investigation of average Finnish lettuce production. Results: The climate change and all other impact categories were lowest for lettuce produced in vertical farming with renewable energy and waste heat recovery. The climate change impact was largest for lettuce produced in greenhouse with average energy use. For energy use and energy resource use, the impacts of vertical farming were lower than greenhouse production, but for mineral and metal use and water scarcity, the impact of vertical farming was higher for average energy use without heat recovery. Direct land and irrigation water use on the production sites in Finnish circumstances represented only a small share of total land-use and water-use impacts on both production methods. Conclusion: Paying attention to the energy source and heat recovery, the environmental sustainability can be advanced in both vertical and greenhouse production systems. [ABSTRACT FROM AUTHOR]

Copyright of Low-Carbon Materials & Green Construction is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An effective heating, ventilation, and air conditioning system has been designed for a three storey north-oriented hospital building. The heat load of this building was calculated using the Hourly Analysis Program software with regard for the recovery of the energy from the exhaust air stream with the use of a heat recovery wheel reducing the temperature of the supply air stream and lowering the load on the air handling unit in the building. The results obtained show that a heat recovery wheel attached to a heating, ventilation, and air conditioning system makes it possible to improve the indoor air quality with conservation of 30% of the the electrical energy. [ABSTRACT FROM AUTHOR]

The testis serves as the primary site for spermatogenesis in mammals and is a crucial organ for the secretion of male hormones. Heat stress (HS) can have adverse effects on the seminiferous tubules, sperm quality, and sperm fertilization capability within the testis. Despite numerous previous studies describing various time points after heat stress in mice, a systematic and comprehensive dataset on heat stress and recovery in mice has been lacking. This study aimed to explore the gene expression changes in the recovery of multiple seminiferous epithelial cycles and spermatogenic cycles in mouse testicles after heat stress. We obtained high-throughput bulk RNA-seq data from testicular tissue of 4 NC mice and 32 HS mice (divided into 9 groups: NC, 30 min, 2 h, 6 h, 24 h, 3d, 8d, 24d, 47d, and 95d) and illustrated the dynamic changes in differential genes. This data set provides valuable insights into the detailed dynamic changes of one or more spermatogenic cycles after heat stress in mouse testicles, as well as the molecular mechanisms involved. [ABSTRACT FROM AUTHOR]

Energy waste from power plants, typically emitted into the atmosphere, contributes to climate change and resource depletion. Integrating heat recovery systems into power plants can improve overall efficiency. This study focused on utilizing waste heat from a 500-MWe coal-based supercritical standalone plant through the organic Rankine cycle. The power plant uses Indian coal as a fuel input, and five distinct working fluids, R245fa, methanol, acetone, ethanol, and benzene, are considered working fluids for the ORC system. Thermodynamic analysis indicates that the standalone plant exhibits energy and exergy efficiencies of 27.33% and 25.01%, respectively. Following the integration of ORC, an overall efficiency improvement is observed. The increment in efficiency is because of the waste heat utilization, where the ORC generates additional electricity generation with outputs of 9.91 MWe for R245fa, 13.71 MWe for methanol, 13.97 MWe for acetone, 14.04 MWe for ethanol, and 14.11 MWe for benzene. Additionally, the study reveals a substantial reduction in CO2 emissions compared to the coal-based power plant with the same production of power, amounting to approximately 216.43 tons for R245fa, 299.43 tons for methanol, 305.10 tons for acetone, 306.63 tons for ethanol, and 308.16 tons for benzene. The thermodynamic investigation identifies the superior performance of the benzene-based ORC among the chosen fluids, and the economic study concludes that the ethanol-based ORC stands out as the most favorable option among the considered alternatives. [ABSTRACT FROM AUTHOR]

As building becomes more leak-tight, air refreshment to improve indoor air quality is needed for healthy living standards. In the quest to ensure comfortable indoor climatic conditions, energy recovery ventilators (ERV) are used to provide air refreshment and thermal comfort. In this study, a fixed plate air-to-air ERV was analysed to determine its effectivity in terms of energy recovery during air refreshment. A customized test bench was built and used to acquire the instantaneous surface temperatures of the heat exchanger plates contained in the ERV during air refreshment. Also, a numerical model of the ERV was developed and validated by comparing its output from simulation with experiment results under the same conditions. The model consisted of a single heat exchanger plate and the air across the plate surface. To capture the effect of heat transfer between the air and the heat exchanger plate in 3D, the model was discretized into numerous cells. From the experiment and simulation results, the air-to-air ERVs were more effective in recovering thermal energy at low flow velocity than at high flow velocity. At lower flow velocity, it will take a longer time duration before any significant impact is made on the thermal conditions of the building, comparatively. The prediction of the model was within acceptable margins and could be used to provide insight on the ERVs performance improvement. [ABSTRACT FROM AUTHOR]

The paper aims to investigate the fuel and system options for a floating power plant (FPP) considering economic performance and the decarbonization goals of the International Maritime Organization. Various case studies have been assessed using a reference FPP, encompassing the instant and future retrofitting scenarios. The ready-to-use scenarios involve alternative fuel and organic Rankine cycle-based waste heat recovery system usage. Nuclear energy systems have been evaluated within the reference FPP since they are suitable candidates for achieving zero-carbon objectives and providing low-cost electricity. A simulation framework created in Python has calculated the fuel consumption regarding the power requirement and organized the approaches used in the study. An environmental model comparing the systems has been built to calculate upstream and operational emissions. The cost projection model for 2030 and 2050 has assessed the economic performance. Technique for Order of Preference by Similarity (TOPSIS) one of the multi-criteria decision-making approaches has ranked the systems considering the outcomes of economic and environmental models over the years. Findings demonstrate that the current fuel usage scenario of the FPP is not suitable both environmentally and economically. The other emissions can be near zero and greenhouse gases can be decreased by up to 15.95% using alternative fuels. Nuclear energy is a strong candidate to meet the 2050 targets, but its viability is largely based on economic performance. [ABSTRACT FROM AUTHOR]

The study performs energy and exergy analyses for each component such as boilers, buildings, distribution networks and heat exchangers of a new generation district heating system. Energy and exergy efficiencies are compared for all system components, and energy and exergy losses are presented using Sankey and Grassman diagrams. Three flue gas condensers with finned bundles are designed for different capacities of boilers that intend to recover water and heat from the waste flue gas in the district heating system due to high flue gas energy losses. Colburn-Hougen and one-dimensional finite difference methods are used to design the flue gas condensers with the MATLAB program. The exergy analysis showed that the exergy input to the system is lost by 4.52% from the distribution networks, 4.15% from all buildings and 2.18% from the flue gas. In the system, the energy and exergy efficiencies of the boilers are calculated to be 87.23% and 17.32%, respectively, and the heat loss from the flue gas is found to be 12%. The design results show that the values of mass convection coefficient (km) for all flue gas condensers decrease from 0.0706 at the inlet condensation zone to 0.0354 towards the outlet. The total condensation rate and condensation efficiency are found to be 86 kg/h and 60%, respectively, for the 2500 kW boiler. [ABSTRACT FROM AUTHOR]

Acid dew point is a crucial factor in determining the low-temperature corrosion rate and the thermal efficiency of downstream process equipment such as stacks in a crude oil refinery. This research was conducted to determine the flue gas acid dew point of a furnace used to pre-heat the input of a crude distillation unit in a refinery. The furnace uses combination of fuel oil and fuel gas sourced from the refinery with a known elemental composition. Three scenarios were analyzed; fired from fuel oil, from fuel gas, and a combination of both. The third scenario is based on a day of which the feed rate of the unit was 5350 tons/day. Using the fundamental analysis of combustion chemistry and two methods of A.G. Okkes' and Verhoff and Banchero's, the theoretical acid dew point in each scenario was determined. It was 150.52 and 155.00°C in the latter scenario. The flue gas temperature was measured as 183°C. Hence, it was determined that the acid dew point was below the flue gas temperature. The determined results can be used as a benchmark to mitigate low-temperature corrosion in downstream equipment and to evaluate further thermal recovery if needed. [ABSTRACT FROM AUTHOR]

Middle-deep geothermal reservoirs, rich in energy, experience deep burial, high temperature, and intense three-dimensional stresses, causing noticeable elastic–plastic rock deformation under high confining pressure. However, existing researches primarily focused on elastic–plastic properties under various confining pressures, overlooking the impact of high temperature on granite's behavior. To address this, we conducted compression experiments at seven temperature points (25–600 °C) under varying confining pressures (0–15 MPa). The results reveal that increasing confining pressure prolongs the plastic yielding stage, linearly enhances compressive strength, and shifts rupture mode from brittle to expansion shear damage. Conversely, under constant confining pressure, compressive strength decreases with rising temperature, accompanied by more intricate artificial cracks. Rock cohesion, internal friction angle, and wave velocity decrease due to increased thermal damage micro-cracks. Heat treatment over 500 °C significantly increases porosity and pore throat radius, explaining heightened plasticity in hot dry rocks. These findings offer theoretical and technical insights for understanding elastic–plastic fracture mechanisms during hydraulic fracturing in middle-deep geothermal reservoirs and enhancing heat recovery efficiency. [ABSTRACT FROM AUTHOR]

A new process is proposed for the pyrolysis of ammonia in a filtration combustion moving bed reactor to produce hydrogen. The process can be implemented in reactors with energy recovery with a separate supply of reagents (including swiss-roll reactors, etc.). The mass-energy balance of the process is calculated. The pyrolysis products are analyzed under a condition of thermodynamic equilibrium with varying temperature and pressure. The system pressure is varied from 1 to 10 bar. The temperature range from 300 to 1100 K iss considered. It is shown that the pyrolysis of ammonia ends at a temperature of 620 K at atmospheric pressure. An increase in pressure in the system leads to a slight increase in the temperature of the pyrolysis of ammonia. The portion of hydrogen that needs to be burned to cover the energy for heating and pyrolysis of the initial ammonia in the case of an adiabatic reactor is 0.13. From one mole of ammonia it is possible to obtain 1.31 moles of hydrogen. [ABSTRACT FROM AUTHOR]

Pulsating heat pipes (PHPs) offer a promising solution for thermal management in diverse industries owing to their simplicity, cost-effectiveness, and impressive cooling capabilities. The angle of inclination of the heat pipe with reference to the horizontal plane significantly influences PHP performance. Unsatisfactory outcomes were observed at 90° and 180° inclination angles. A comprehensive investigation explored the impact of tilt angle and fill ratio on PHP performance indicators, specifically heat transfer rate (HTR), overall heat transfer coefficient (OHTC), and thermal resistance (TR). Tilt angles ranged from 30° to 60°, while fill ratios varied from 40 to 80%. To optimize PHP working parameters that maximize HTR, minimize TR, and enhance OHTC, a modified Taguchi approach was integrated with a robust multi-objective optimization technique. Empirical models for HTR, TR, and OHTC were developed and validated against experimental data. The recommended PHP working parameters are a 60% fill ratio and a 30° tilt angle. For the optimal parameters, HTR estimates ranged from 33.96 to 34.29 W, with the experimental value of 34.124 W falling within this range. TR estimates ranged from 0.0207 to 0.1097 °C W−1, encompassing the experimental value of 0.078 °C W−1. OHTC estimates varied between 835.8 and 958.42 W m−2 K−1, including the experimental value of 835.79 W m−2 K−1. The developed empirical relationships provide valuable insights into PHP performance for any fill ratio and tilt angle within the applicable range. PHPs find diverse applications in refrigeration, aerospace, waste heat recovery, and the utilization of low-grade energy. [ABSTRACT FROM AUTHOR]

Background: Reducing energy consumption and greenhouse gas emissions is a crucial issue in the cassava starch processing industry. In this study, the integrated system combining livestock, cassava cultivation and cassava production in the same area leads to both a zero emission goal and economic efficiency, a typical example of an effective agro-industrial symbiosis. A heat exchange/recovery system was applied including the economizer, heat exchanger tank, biogas tank, and boiler. The economizer attached to the boiler's chimney transfers heat from exhaust gases for pre-heating feed water entering the boiler. The biogas tank recovers energy from the wastewater of starch production and livestock, and the generated biogas was used as fuel for the boiler. Results: The energy and exergy efficiency, energy losses, and exergy destruction for the heat recovery system were analyzed. The specific energy consumption was used to evaluate the overall energy efficiency for a cassava starch factory with a capacity of 20 tons/day. The results show that there is a high potential to recycle waste into energy in the cassava starch industry. The total energy saving and reduced greenhouse gas emissions per year of the cassava starch factory were 0.054%/year and 123,564 kgCO2/per year, respectively. Conclusions: Cassava starch factories can save energy and reduce emissions when applying a heat recovery system in the integrated agro-industrial system. Excess heat from the production was used for evaporating (removal of) NH3 in wastewater flow from the biogas tank, and for heating the biogas system to enhance the efficiency of methane production. A biochar filter was attached to the economizer for adsorption of released ammonium, and the biochar after adsorption was combined with sludge from the biogas tank to produce a solid biofertilizer. [ABSTRACT FROM AUTHOR]

Pulsating Heat Pipe (PHP) is an emerging efficient heat transfer device, that transfers heat passively through oscillating motions of liquid slugs and vapor plugs within the device. PHP is of high effective thermal conductivity with great potential in heat transfer management for various applications. The objective of this review paper is to summarize and analyse the applications of PHP in various fields that have been reported in the open literature, emphasizing on studies reported in past half decade. The thermo-hydraulic behaviour of PHP is influenced by numerous geometric and operational parameters, which are discussed in detail in the first part of the paper. The thermal performance of the PHP under rotation condition, which is seldom discussed in previous review articles, is also discussed. These parameters act individually and in tandem to alter the performance of PHP, which makes its prediction extremely difficult. However, the benefit of numerous influencing parameters is that they can be altered to make PHP suitable for various applications. These highly variable configurations make PHP suitable for applications such as the transfer of absorbed solar energy to the location of interest, waste heat recovery, thermal management of electric vehicle batteries, fuel cells, cooling of electronic components etc. PHPs are recently being studied for applications in cryogenics and cooling of cutting tools in the machining process also. In addition, novel applications of PHP such as high-performance fins for heat exchangers, cooling of building roofs etc. are also being reported. All these applications of PHP reported in the open literature are reviewed and summarized in the present article. [ABSTRACT FROM AUTHOR]

The International Maritime Organization has set targets for reducing greenhouse gas emissions from ships. Thus, it is imperative to investigate novel technologies that have the potential to achieve these targets and reduce emissions in the short and long term. Waste heat recovery (WHR) technology, which generates electricity from engine waste energy, is a promising solution. This research examines the integration of a thermoelectric generator and organic Rankine cycle as a combined WHR system onboard a passenger ship. The purpose of the paper is to analyze the TEG–ORC system parametrically and from a techno-economic perspective. The results showed that the optimum design scenario is achieved by integrating the recuperative ORC system (rcORC) with the TEG system, this integration produces 1569 kW as net output power (19% more than the original TEG–ORC system) at an evaporation pressure of 55 bar. The exergy efficiency of the system is enhanced from 43.2 to 48.6% by the addition of the recuperator. Also, the efficiency of the power system (engine + TEG–rcORC system) is 53.2% (+ 6.1% over the efficiency of the standalone engine). The integration of the TEG–rcORC system with the main engine provides the ship with an energy efficiency existing index (EEXI) of 22.47 g-CO2 ton−1 nm−1, this value is lower than the required EEXI by 11%. From an economical point of view, the levelized power cost of the TEG–rcORC system is 280.2 € kW−1, and the annual saving in expenses is 1.05 M€ with a discounted payback time of 3.9 years. [ABSTRACT FROM AUTHOR]

The rapid decarbonisation of the power generation and aviation sectors will require a move away from incremental development, exposing designers and researchers to the risk of unexpected results from uncertainty in boundary layer state. This problem already exists for parts developed with fully turbulent assumptions, but in novel design spaces the risk increases for both real components, where previous knowledge of similar designs may be inapplicable, and particularly in experimental testing of scaled models, where reducing Reynolds number can result in a drastic change in flow topology that skews the conclusions of a test. Computational methods struggle to reliably predict boundary layer state so experimental techniques for diagnosing boundary layer state are needed. Infrared thermography (IR) is a non-invasive technique that offers simple, fast visualisation of boundary layer state with no additional instrumentation. IR is relatively uncommon in the literature and there is minimal information available on the best practices for its use. This paper aims to encourage the adoption of IR as a diagnostic tool by demonstrating routes for optimisation and pointing out pitfalls to avoid. A low-order model is developed and used to predict how the signal-to-noise ratio (SNR) of an IR visualisation changes depending on the thermal design of the test piece. It is shown that in low-speed flows with active heating from the surface the SNR is maximised through a suitable choice of surface insulation, while in high-speed flows, where passive temperature differences are used, there is a crossover between heat transfer and recovery temperature effects that results in an SNR of zero, an effect that can arise in both steady-state and transient experiments. Experimental validation of the 1D model in both flow regimes is shown alongside two case studies on the use of IR in sub-scale testing where uncertainty in boundary layer state results in critical differences from the full-scale flow. [ABSTRACT FROM AUTHOR]

The paper takes the Jidong Nanbu high temperature oil reservoir as the research object and establishes the comprehensive numerical model of CO2 storage and displacement based on the CO2 displacement mechanism, CO2 heat recovery mechanism, and CO2 geological storage mechanism. On this basis, the injection and production optimization model is established by combining the theory of multi-objective and single-objective optimization algorithm respectively. The objective function of the multi-objective injection and production optimization model is NPV and CO2 heat recovery. The model is solved using the NSGAII and MOPSO algorithm. The results show that the objective function value obtained by the MOPSO algorithm is better than the NSGAII algorithm. The optimal values of NPV and CO2 heat recovery were 4.781 × 108 CNY and 1.078 × 1016 J respectively. The objective function of the single objective injection and production optimization model is the NPV. GA and DE optimization algorithms are used to solve the model. The results show that the DE algorithm gets the better objective function value than the GA algorithm. The optimal value of NPV is 3.69 × 1010 CNY. [ABSTRACT FROM AUTHOR]

Industrial symbiosis (IS) is known as an effective strategy to reduce resource consumption. Recently, the utilization of efficient energy conversion technologies in symbiotic relations has been suggested to enhance the flow exchange efficiency and economic effectiveness of energy-based industrial symbiosis schemes. In this work, the possibility of improving industrial symbiosis between agricultural greenhouses and waste heat sources in industries is investigated by utilizing the organic Rankine cycle (ORC) in different configurations. For this aim, a modelling tool is developed to analyse the thermo-economic justification of energy-based industrial symbiosis and estimate the possibility of simultaneous waste heat utilization for power generation and greenhouse heating. The results show that the selection of working fluid, capacity and configuration has a significant effect on the successful implementation of ORC technology and can reduce the payback period time to less than 5 years for the proposed case study. However, results indicate that even using an optimized ORC system is not always accompanied by improving the economic effectiveness and justification of IS establishment. [ABSTRACT FROM AUTHOR]

In this study CoZrMnSb, a quaternary Heusler alloy has been explored utilizing the density functional theory based simulation package WIEN2k. The structural analysis exhibits an X1-type structure with a relaxed lattice constant of 6.27 Å in ferromagnetic phase. The band structure calculations show its half-metallic nature with full spin polarization states around the Fermi level at 0.56 eV energy. In addition, the magnetic moment is calculated to be 1.0 μB, which is in accordance with the Slater Pauling rule (Mtot = (Ztot–24) μB). The study shows the d-d hybridization of the transition metals Co, Zr, and Mn elements. Further, optoelectronic performances in terms of dielectric function, reflectivity, energy loss function, absorption coefficient have been determined for a range of photon energy up to12 eV (ultraviolet region). In optoelectronic applications, absorption of this material in visible light enhances its significance. The thermoelectric properties with chemical potential and thermodynamic properties in the pressure range of 0–40 GPa and temperature range of 0–1200 K have been analysed. Specific heat capacity and Debye temperature authenticate similar metallic behaviour of CoZrMnSb alloy at temperature versus pressure variations. At room temperature, the chemical potential study suggests high figure of merit ~ 0.9, which makes it a potential thermoelectric material. The suggested material has a high Seebeck coefficient and low thermal conductivity, making it a better match for waste heat recovery and spintronic applications. [ABSTRACT FROM AUTHOR]

A new power and refrigeration cycle is examined in the present study. The system proposed is a combination of organic Rankine cycle (ORC) and an ejector refrigeration cycle (ERC). An ERC is introduced into the ORC to recover heat from partial expansion of the ORC fluid. The heat recovery is enhanced with the incorporation of recuperator, evaporator and superheater as heat exchangers. Among the various working fluids opted for, R245fa and R236ea have been considered in the present work. The properties of the combined cycle state points are evaluated through Engineering Equation Solver (EES) software. The impact of decision variables (such as hot source temperature, turbine expansion ratio, extraction ratio, and separator temperature) on performance parameters (such as exergy destruction, energy efficiency of power generation, exergy efficiency of power generation, energy efficiency of combined system, exergy efficiency of combined system, COP, and cooling power ratio) is examined and reported. The series heater configuration in ORC has improved system performance by recovering waste heat more effectively. At the same parametric conditions, the energy and exergy performances of R245fa are higher than those of R236ea. [ABSTRACT FROM AUTHOR]

Thermoelectrics have great potential for use in waste heat recovery to improve energy utilization. Moreover, serving as a solid-state heat pump, they have found practical application in cooling electronic products. Nevertheless, the scarcity of commercial Bi2Te3 raw materials has impeded the sustainable and widespread application of thermoelectric technology. In this study, we developed a low-cost and earth-abundant PbS compound with impressive thermoelectric performance. The optimized n-type PbS material achieved a record-high room temperature ZT of 0.64 in this system. Additionally, the first thermoelectric cooling device based on n-type PbS was fabricated, which exhibits a remarkable cooling temperature difference of ~36.9 K at room temperature. Meanwhile, the power generation efficiency of a single-leg device employing our n-type PbS material reaches ~8%, showing significant potential in harvesting waste heat into valuable electrical power. This study demonstrates the feasibility of sustainable n-type PbS as a viable alternative to commercial Bi2Te3, thereby extending the application of thermoelectrics. The authors fabricate a thermoelectric cooling device based on n-type PbS based material, which exhibits a remarkable cooling temperature difference of 36.9 K at room temperature, and the single-leg power generation efficiency of 8%. [ABSTRACT FROM AUTHOR]

The energy conversion performance of commercial photovoltaic (PV) systems is only 15–20 percent; moreover, a rise in working temperature mitigates this low efficiency. To enhance their performance and prevent damage, researchers test new technologies and integrate heat recovery devices with PV systems. Concentrated photovoltaic systems (CPVs) are especially vulnerable to high radiation levels. This paper explores novel cooling techniques for PV systems, an area that has not been extensively investigated before. The cooling methods are categorized into front-surface and back-surface cooling methods, offering a unique perspective on how to keep PV systems cool. Moreover, the paper delves into the advancements made in PV cooling systems and CPVs, shedding light on the cutting-edge developments in this field. The results demonstrate the profound impact of various operational factors, such as radiation and wind speed, on the selection of suitable cooling systems or heat recovery methods. These findings unveil the crucial importance of considering these factors when choosing cooling techniques, adding a compelling dimension to the research. For example, it was depicted that optical cooling techniques can enhance the performance of PV systems by up to 4.2% and the solar-to-heat conversion efficiency by up to 47%. Furthermore, this research ventures into uncharted territory by subjecting both the front and back sides of the PV module to active and passive cooling techniques under differing work conditions. The comprehensive list provided here exhaustively describes the advantages, disadvantages, and developments of each technique, revealing the novelty of the approaches explored in this paper. It was reported that back cooling techniques can decline the cell temperature of PV systems by up to 57.8% and grow the electrical and thermal efficiencies by up to 82.6% and 97.75%, respectively. The groundbreaking nature of this research lies in its ability to empower decision-makers to select the optimal cooling system based on specific requirements and environmental factors, thereby bridging the gap between theory and practical application. The paper also introduces a new concept of cooling using hydrogel, a 3D porous network structure that can enhance photovoltaic energy conversion and storage, and reviews two recent studies that demonstrated the effectiveness of hydrogel cooling methods for PV panels. Moreover, the paper discusses the issue of dust deposition and mitigation, which affects the performance and lifetime of PV modules, and evaluates various methods for cleaning or reducing dust on PV panels, such as manual, passive, self-cleaning, and mechanical. [ABSTRACT FROM AUTHOR]

Heat pipe heat exchangers (HPHEs) offer an efficient solution for industrial waste heat recovery by utilizing latent heat transfer. This study compared a traditional water-based HPHE and one augmented with 1% silver nanoparticles by volume. The HPHEs with distinct 500-mm evaporator and condenser sections were assessed on parameters like temperature distribution, heat transfer rates, thermal resistance, and effectiveness under varying thermal loads (70–90 W) and hot/cold fluid mass flow rates (0.2–0.6 kg min−1 and 0.1–0.3 kg min−1). The nanofluid HPHE demonstrated superior performance, with a 12.21 °C peak evaporator temperature difference and 39.25% maximum effectiveness at optimal conditions, exceeding the DI water HPHE by over 10%. The higher heat fluxes proportionally improved heat transfer parameters. Moderate mass flow rates around 0.2 kg min−1 (hot fluid) and 0.1 kg min−1 (cold fluid) optimized performance. The unconventional adiabatic-less design improved heat transfer compared to traditional heat pipes. The nanofluid HPHE's exceptional heat recovery capacity proves its viability for harnessing low-grade industrial waste heat, leading to significant energy savings. The study provides critical insights into thermal performance enhancements through synergistic HPHE design modifications and nanoparticle augmentation of the working fluid. [ABSTRACT FROM AUTHOR]

Though CO2 power cycles are preferred for diesel engine waste heat recovery, a very high operating pressure of the CO2 power cycle is an issue of concern. To address this issue, in the present study, CO2-propane and CO2-R152a mixtures with various CO2 mass fractions are proposed as the working fluid of a regenerative transcritical power cycle recovering waste heat of a diesel power plant. To reduce the possibility of accidental fire hazard; the minimum permissible CO2 mass fraction is restricted to 0.3. It is observed that reducing CO2 mass fraction ensures higher output power and lesser levelized electricity cost (LEC), specifically at a lower turbine inlet pressure. Between two considered CO2-based mixture pairs, the transcritical cycle exhibits a superior performance with CO2-R152a-based mixtures. The LEC of the presented CO2-propane-based optimized cycle is about 6.36% lower compared to that of the optimized supercritical CO2 power cycle. For the CO2-R152a mixture-based cycle, the corresponding achievable reduction in LEC is about 15.20%. Turbine inlet pressures corresponding to the minimum LECs of the optimized CO2-propane and CO2-R152a mixture-based cycles are, respectively, close to 33% and 39% lower than that of the optimized supercritical CO2 power cycle. As R152a is less flammable than propane, an R152a-based mixture working fluid also ensures a safer operation compared to a propane-based mixture. [ABSTRACT FROM AUTHOR]

The objective of this study is to design a heat-recovery boiler for a 1 MW-class gas engine-based cogeneration system intended to recover heat from engine exhaust gas. To accommodate high-pressure applications, a water tube-type boiler is selected. For ensuring effective water circulation within the boiler, an innovative modular-type boiler based on the mini-boiler concept is developed. This boiler comprises finned tube-type risers, and their heat-transfer characteristics are measured and compared with the conventional correlation used in the design process. Additionally, an inlet guide vane is developed to address the temperature nonuniformity resulting from the shape mismatch between the gas engine outlet and heat-recovery boiler inlet. The performance of the proposed boiler was evaluated by integrating it into an experimental rig. The diamond-shaped inlet guide vane, which was designed by computational fluid dynamics, facilitated a uniform temperature distribution. However, the temperature became nonuniform downstream owing to the influence of a downcomer. Although the modular heat-recovery boiler effectively produced steam from gas engine exhaust gasses, its heat-transfer performance in the downstream section was lower than expected, necessitating additional heat-transfer area. [ABSTRACT FROM AUTHOR]

Thermoelectric generation (TEG)-based waste heat recovery technology is an example of a low-grade energy recovery application. This study proposes a waste heat recovery system that can store the recovered energy and run low-power automotive car lamps. Experimental analysis was conducted to examine the output characteristics of the TEG-based waste heat recovery system, focusing on how the structural components and operational parameters influenced these characteristics. The study also explored and optimized the working strategy of the system for driving light-emitting diode (LED) car lamps. Both the dynamic output characteristics of the system and the lighting attenuation rule of the lamps were evaluated. The results revealed that increasing the heating temperature would improve the recovered energy of the system. However, when a high-power LED chip was used for heat generation instead of an electrically controlled heating plate, a slightly larger amount of energy was collected at the expense of a slightly lower thermoelectric conversion rate. Furthermore, connecting a supercapacitor to the waste heat recovery system for energy storage increased the operational time of the lamps. The supercapacitor also served as a buffer for power and voltage fluctuations caused by variations in the heating temperature. These findings demonstrate that the waste heat recovery system not only meets the requirements of the LED car lamps but can also power other low-voltage and low-power devices. [ABSTRACT FROM AUTHOR]

In this study, the partial heating supercritical CO2 power cycle for waste heat recovery is investigated to understand more about the true potential of thermodynamic and economic performance improvement of each system component, as well as a more profound comprehension of the simultaneous interactions between the system components using advanced exergy and advanced exergoeconomics analysis. In addition, the affirmative or nugatory impact of the inefficiency of each component on the exogenous exergy destruction and exogenous costs in other system components separately, as well as the effect of the inefficiency combination of other components on the desired component (mexogenous effect) have been determined. The results demonstrated that according to the technological constraints in the system, the maximum exergy efficiency that can be achieved is 59.8%, and 38.4% (926.9 kW) of the total exergy destruction and 46.18% (32.52 $ h - 1 ) of the total exergy destruction cost of the system is avoidable. According to the mexogenous exergy destruction, the simultaneous interplay among other system components affects the turbine performance most. The priority of improving the components based on the highest avoidable endogenous exergy destruction cost is related to the turbine, cooler, and compressor. The results of this study revealed that 97.8% (79.73 $ h - 1 ) of the system's total cost is relevant to the endogenous part, which shows that the cost caused by the interaction among the components is very small. The turbine and compressor have the most significant cost-saving potential, while the heaters have the lowest. [ABSTRACT FROM AUTHOR]

In order to clarify the effect of mechanical tensioning and SMA wire heating recovery on introducing prestress into CFRP sheet strengthened reinforced concrete (RC) beams, an experimental research on the bending performance of prestressed CFRP sheet strengthened RC beams was conducted. Based on the test results, a bending carrying capacity model for RC beams externally strengthened with prestressed CFRP sheets was proposed. The model provides calculation methods for the decompression moment, cracking moment, yielding moment, and ultimate moment, corresponding to different failure modes of the RC beams strengthened with externally bonded prestressed CFRP sheets. Four experimental beams were designed to verify the accuracy of the model with the prestresses of 100 MPa and 200 MPa. The results show that during the yield stage and strengthening stage, the loading-unloading stress-strain relationship curves of SMA wire under different prestrains are basically consistent. When the prestrain of SMA wire is 10%, the maximum recovery stress reaches 448.5 MPa. Under the same prestrain conditions, the maximum recovery stress of CFRP sheets was reduced by 37.8–39.5% when the prestress was introduced through heating recovery of SMA wires. The failure mode of mechanically tensioned prestressed CFRP sheet strengthened beams is the CFRP sheet debonding caused by mid-span bending cracks, while the failure mode of strengthened beams with prestressed CFRP sheet by SMA wire heating recovery is the CFRP sheet end debonding. The cracking moment and yield moment of the strengthened beams are significantly increased by two methods of introducing prestressing. The stiffness improvement of mechanically tensioned prestressed CFRP sheet strengthened beam is relatively large. While, the prestressed CFRP sheet strengthened beam by SMA wire heating recovery gradually experience end peeling failure of the CFRP sheet, and the prestressing effect does not effectively limit the development of cracks, resulting in limited stiffness improvement. The calculation results are in good agreement with the experimental results, proving that the proposed method for analyzing the entire bending process can be used to predict the bending mechanical properties of the prestressed CFRP sheet strengthened beams. [ABSTRACT FROM AUTHOR]

Many engineering applications, such as waste heat recovery, air-conditioning and refrigeration systems, include heat exchangers. In this work, the performance of a double-tube heat exchanger with a rotating tube, perforated ring inserts and nanofluids as working fluids has been studied. After developing a 3D numerical model, verifying its discretization and validating it with experimental results, an optimal design for maximizing heat transfer while keeping a relatively low pressure drop was found (11 eight-holed rings with a 2.2 pitch ratio). Increasing the cold fluid Reynolds number to 4946 and the inner tube rotational speed to 500 rpm increased the heat transfer coefficient from around 7500 to 9500 W (m2 K)−1. Considering the nanofluids studied, the best performance was found with Cu nanoparticles, followed by Al2O3–Cu and Al2O3. With Cu nanoparticles at 3%, heat transfer coefficients above 12,100 W (m2 K)−1 were obtained, increasing heat exchanger effectiveness from 27 to 51%. Pressure drop levels increased up to 235 Pa, resulting in increasing pumping requirements by around 0.1 kJ kg−1. Hence, only very high flowrates would represent a problem when using the exchanger. Explanations for the underlying physical phenomena that cause the enhancement of heat transfer due to the rotational speed, the perforated rings and the nanofluids were provided. Turbulent kinetic energy contours, flow streamlines, and temperature contours were used to gain insight into the thermal and flow fields, identifying the mechanisms responsible for the enhancement of the heat exchanger effectiveness. [ABSTRACT FROM AUTHOR]

This study focuses on CO2 capture by pressure swing adsorption (PSA), with modified clinoptilolite as the adsorbent. Natural clinoptilolite is modified by roasting, by acid pickling, by a combination of acid pickling and roasting, and by ion exchange. Modification by acid pickling–roasting and by ion exchange are found to give the highest CO2 adsorption capacities, of 730 mL/g and 876.7 mL/g, respectively. It is found that regeneration of clinoptilolite by a combination of vacuum desorption and heating enables recovery of as much as 89% of its previous CO2 adsorption capacity. To examine the CO2 adsorption capacity of clinoptilolite when applied to mixed gas, a simulated coking exhaust containing 12% CO2 and 4% O2 is used, and it is found that ion exchange modified clinoptilolite achieves a CO2 removal efficiency of 92.5%. A BET test reveals that acid pickling–roasting and Na+ modification enhance the porosity of clinoptilolite, thereby improving its adsorption capacity. This work demonstrates the feasibility of applying modified clinoptilolite as an effective adsorbent for CO2 capture, providing a promising tool for dealing with greenhouse gases. [ABSTRACT FROM AUTHOR]

Decoupling cooling and ventilation tasks with an existing air conditioning methodology are a promising performance-enhancement technology. In this direction, different configurations of a desiccant-integrated independent ventilation element attached to a conventional cooling system are proposed in this study. This work establishes a quantitative comparative performance analysis among the different process air cooling (obtained through desiccant dehumidification) techniques for three different climates, namely, hot-dry, tropical, and Mediterranean. EnergyPlus simulations have been executed on a small-scale office building of 400-m2 area. The building constructional details and other required simulation input parameters follow benchmark standards. As the chemical dehumidification increases, the process air, i.e., supply air temperature that cannot be sent directly to the room, needs to be cooled. Three approaches for process air cooling have been considered: direct expansion (DX) cooling coil, indirect evaporative cooling (IEC), and sensible heat recovery wheel (SHRW). A solar collector assembly with a supporting heating arrangement is coupled with desiccant unit for regeneration. Outdoor air is used for regeneration in the case of the DX cooling coil and IEC, whereas return air is used in the heat recovery wheel case. Annual simulation results reveal that the SHRW-aided case performs superior than DX coil case for the pertinent climatic conditions, with 9.6 to 45.01% of annual energy savings. For the IEC, energy consumption was 1.8 to 18.38% less than that of DX coil. Also, using return air in this best-suited case reduces the net thermal energy requirement for regeneration by 14.63 to 71.65% with respect to DX coil. [ABSTRACT FROM AUTHOR]

Chile is one of the countries with most growing industries worldwide due to their mining and manufacturing industries. Nevertheless, at the same time there is a lack on energy generation and processes efficiency. The objectives of this paper are to estimate the amount of available industrial waste heat derived from the manufacturing industry in Chile, to locate these heat sources geographically, to assess the best technologies to be used to take advantage of this heat, and finally, to estimate the environmental savings of its reuse. Results showed that the sectors with the highest potential for the use of residual heat are food and beverages with an average accumulated potential of 62.9 PJ, basic metals with 21.5 PJ, chemical products with 15.1 PJ, paper products with 10.8 PJ, and non-metallic minerals with 10.6 PJ. With these data, the energy generation in Chile could be more efficient as well as the industrial processes could save more energy, reducing costs and raw materials. [ABSTRACT FROM AUTHOR]

Internal combustion engine inefficiencies and waste heat emissions raise environmental concerns, as they waste fuel energy in the form of heat, increasing fuel consumption and greenhouse gas emissions. Additionally, waste heat contributes to the urban heat island effect. Waste heat recovery is a vital solution, capturing and repurposing heat to reduce fuel use, emissions, and costs while promoting sustainability, innovation, and economic growth. Polygenerative waste heat recovery maximizes energy efficiency by generating multiple forms of energy from a single source, enhancing overall sustainability. The proposed Trinitor model is a polygenerative system encompassing power generation, product drying, space cooling/heating, and oxygen production. Power generation utilizes exhaust heat stored in a phase change material (PCM) to generate electricity through a Hot Air Turbine. The PCM also stores heat from the PVT thermal collector and supports produce drying. In the space cooling/heating process, the temperature contrast resulting from the hot air generated by the turbine and the cooled air from the Cooling chamber is harnessed by the Seebeck principle within the TEG, converting heat energy into electricity, and it is possible to create temperature variations using the Peltier Effect by supplying electricity. Oxygen production involves dehumidifying air, separating oxygen from hydrogen using an electrolyzer and storing oxygen for civilian use. A component review identifies SiC wall flow-diesel particulate filters (DPF), a paraffin-based Latent Heat Storage System, and electric-assisted turbo compounding as cost-effective for energy production. Produce drying relies on hot air or infrared drying, a revolving wicks humidifier, and a cooling coil dehumidifier. Space cooling/heating needs a water-type PV/T collector, MPPT charge controller, lithium-ion batteries, and ceramic TEGs. A PEM electrolyzer with appropriate components (bipolar plates, electrodes, catalyst, membrane, and gasket) enhances oxygen production efficiency. Based on existing literature, the trinitor has the potential to attain an overall efficiency ranging from 40.12–54.81%. Thus, a combination of low-efficiency processes results in a highly efficient waste heat recovery Trinitor system, with further improvements possible through identified components' integration. [ABSTRACT FROM AUTHOR]

Industrial facilities, including those specializing in chemical fiber production, are a major source of carbon dioxide, sulfur and nitrogen oxides, and particulate matter emissions. These emissions degrade air quality, affect climate change, and have adverse effects on ecosystems and human health. This paper presents a mathematical model for calculating a scrubber for purifying and heat recovery of the moist air emitted by various devices of chemical fiber production enterprises. [ABSTRACT FROM AUTHOR]

This paper explores the industry's feasibility of using industrial exhaust gases to supplement an organic Rankine cycle (ORC) for energy harvesting and waste heat recovery. Three primary configurations were studied with six different dry and isentropic working fluids: (1) ORC driven by flue gas directly, (2) an integrated heat transfer through a thermos-oil circuit to ORC by flue gas, and (3) an enhanced heat recovery ORC drove by flue gas. The generator power output and cycle efficiencies were projected as performance indicators, while pressures, temperatures, and mass flows were altered accordingly. The results showed that adding an extra heat exchanger before the exit of the exhaust gases in Design II caused a > 14% increase in efficiency for pentane and isopentane. Design II reported a maximum power output as high as 10 MW and a first-law efficiency of 44% for isopentane. Combining the thermo-oil circuit in Design III for better heat transfer proved poor in this case and incurred a loss in efficiency and power. Co-current configured heat exchangers resulted in improved results compared with the counter-current configuration for all designs. [ABSTRACT FROM AUTHOR]

Cement production contributes significantly to anthropogenic greenhouse gas emissions (GHG), a major contributor to global carbon emissions. The environmental impacts of cement production have grown in recent years and it is urgent to reduce its carbon footprint. Systems dynamics (SD) is a simulation method used to understand the nonlinear behavior of complex systems over time. It is commonly used in various sectors to predict emissions and conduct policy experiments. Due to the poor implementation of carbon mitigation strategies within the cement industry, enhancing policymaking by employing more advanced decision-support tools is necessary. This paper reviews previous studies that use the SD approach to assess and compare different mitigation strategies proposed and implemented to reduce carbon emissions in the cement industry. These strategies encompass technological advancements and process improvements, including using alternative fuels and raw materials (adopting low-carbon cementitious materials), energy efficiency improvements, carbon capture and storage and waste heat recovery. The review examines the papers' scope, model descriptions, validation method and mitigation methods highlighted in each study, providing valuable insights for decision makers in the cement industry. Furthermore, the paper discusses the limitations and gaps related to SD modeling, highlighting important factors such as stakeholder engagement in designing effective carbon mitigation strategies. The reviewed studies constantly emphasized technical strategies for mitigating carbon emissions from the cement industry, as stated by the International Energy Agency (IEA) classification. Innovative and emerging technologies, such as WHR, depends on adequate funding, motivation and research and development. However, they frequently neglected to address the barriers hindering their implementation or provide detailed policy measures to overcome them using SD. Additional research is required to assess the practicality and costs of implementing these strategies. Navigating the way to sustainability in the cement industry: Exploring mitigation strategies through systems dynamics model [ABSTRACT FROM AUTHOR]

The sinter cooler, essential for cooling hot sintered ore to a specific temperature, has seen recent advancements with the introduction of a vertical sinter cooling furnace. This innovation aims to enhance energy efficiency, reduce emissions, and improve waste heat recovery. Despite significant research, a quantitative analysis of factors impacting its cooling and heat transfer efficiency is lacking. This study utilizes the Euler model and local non-equilibrium thermodynamic theory to identify key factors affecting the gas–solid cooperative cooling process in the vertical cooler. Through an orthogonal experimental approach, the paper determines the optimal structural and operational parameters for the furnace. Key findings include that a gas–solid ratio of 1200m^3/t, inlet air temperature of 50 ℃, cooling section height of 6m, and diameter of 13.25m maximize efficiency, achieving a weighted range normalization value of 0.962. This configuration meets sintered ore cooling requirements while optimizing waste heat recovery. The study reveals that the impact on heat transfer efficiency is influenced primarily by the gas–solid ratio, followed by the cooling section's height, diameter, and inlet air temperature. These insights are crucial for enhancing the vertical sinter cooler's design, contributing to more energy-efficient and environmentally friendly sintering processes. [ABSTRACT FROM AUTHOR]

Energy recovery ventilation plays a crucial role in providing fresh air and managing respiratory diseases, such as COVID-19. This study focuses on the computational fluid dynamics (CFD) analysis of a compact heat exchanger within a heat recovery ventilator and discusses the findings. However, conducting such an analysis is challenging due to the complex nature of the desired modules, which include intricate fin geometry and the combination of crossflow and counterflow regions in a compact heat exchanger, requiring extensive computational resources. To overcome these limitations, the entire model is treated as a computable unit cell, and the complex calculations involving crossflow and counterflow are simplified by summing individual simulations for each flow type. Furthermore, the detailed numerical modeling method is compared with experimental results, demonstrating the utility of the proposed CFD modeling approach for analyzing plate–fin compact heat exchangers. [ABSTRACT FROM AUTHOR]

This paper proposes a novel pn-junction thermoelectric device to improve the conversion of thermoelectric energy. The device was created by depositing films of p-type Zn-doped CuI and n-type Al-doped ZnO onto an ITO glass substrate using electrodeposition technique. The resulting films had a smooth surface with nano-sized grains. They also exhibited strong adhesion at − 1.2 V compared to Ag/AgCl when 5 mol% of zinc acetate dehydrate was used. The UV-visible graphs revealed that both films had an average band gap of 3 eV. X-ray graphs showed that the thin films were highly crystalline, with orientations symmetrically arranged in the (1 0 2) and (2 2 0) planes. AFM images showed that both films have highly crystalline surface and their surface roughness favours strong adhesion. These high conductive films exhibited thermoelectric energy, which was calculated using the Seebeck effect. The hot probe method showed that the p-type Zn-CuI and n-type AZO thin films were dense and exhibited a thermoelectric figure of merit (ZT) of 0.40 and 0.50 up to the temperature of 120 °C. The thermal conductivity of the p-type and n-type materials was determined to be 2.23 W m−1 K−1 and 12.65 W m−1 K−1, respectively. The power factor of the p and n films was found to be 202.74 µW m−1 K−2 and 525.51 µW m−1 K−2, respectively. This was followed by the fabrication of a Zn-based thermoelectric device using a single pair of p-type Zn-CuI and n-type AZO thin-film legs. The fabricated thermoelectric device generated a maximum power of 117 pW. This Zn-based thermoelectric device is highly effective for waste heat recovery and can efficiently accumulate useful electricity over time, thereby prolonging battery life. [ABSTRACT FROM AUTHOR]

We report a numerical evaluation of the impact of continuous helical baffle on the heat recovery efficiency of counterflow tube bundle heat exchangers. The baffle inclination angle has been varied from 11 ∘ to 22 ∘ . Since the fluid flows over the tube bundle at an angle due to helical flow inside the shell, the heat exchanger operates in cross counter mode. Fluent simulations with the k- ω transition shear stress transport turbulence model have been performed to investigate the thermal-hydraulic parameters of the system in terms of heat recovery efficiency, pressure loss, and overall heat transfer rate. Outside air temperature has been varied to mimic cold and warm weather. Pressure loss has been constrained to be less than 250 Pa, conforming to EU guidelines for energy labeling of residential ventilation units. At the maximum volume flow rate of 40 m 3 /h, the device performed with over 80 % heat recovery efficiency for the considered temperature difference. Continuous helical baffles helped to improve convective heat transfer by reducing cross flow area and increasing velocity. Smaller angles result in greater pressure loss while having no discernible effect on heat recovery efficiency for the considered geometry. The analysis demonstrates the potential of a compact counterflowing recuperative heat exchanger with continuous helical baffles for decentralized ventilation systems and serves as a basis for further optimization. [ABSTRACT FROM AUTHOR]