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Exertional heat stroke (EHS) is a true medical emergency with potential for organ injury and death. This consensus statement emphasizes that optimal exertional heat illness management is promoted by a synchronized chain of survival that promotes rapid recognition and management, as well as communication between care teams. Health care providers should be confident in the definitions, etiologies, and nuances of exertional heat exhaustion, exertional heat injury, and EHS. Identifying the athlete with suspected EHS early in the course, stopping activity (body heat generation), and providing rapid total body cooling are essential for survival, and like any critical life-threatening situation (cardiac arrest, brain stroke, sepsis), time is tissue. Recovery from EHS is variable, and outcomes are likely related to the duration of severe hyperthermia. Most exertional heat illnesses can be prevented with the recognition and modification of well-described risk factors ideally addressed through leadership, policy, and on-site health care.

Brush seals are leakage performance systems that are operating against turbine shafts and bucket tips. Flexible bristle structure can compensate the rotor interference during transients, which enables closer clearance control in turbine and turbo-engine applications. During turbomachinery transients, contacting bristles exert force on turbine shaft, which in turn result in wear, frictional heat generation, counter torque and power loss. Brush seal design with proper stiffness has crucial importance since high bristle tip force levels during rotor contact may result in rotor instability, bristle tip melting or thermo-mechanical fatigue due to large amount of local frictional heat input. Counter torque applied by the contacting brush seal with improperly excessive tip force may result in turbine stall and overall efficiency losses. High levels of bristle contact forces may induce elevated wear rates, which degrades the leakage performance of the brush seal during its life cycle. Brush seal contact force evaluation under operating conditions has critical importance and has to be conducted before turbine integration to avoid performance losses and possible turbine failure in some extreme cases. In this paper, ‘Bristle Contact Force Theory’ is developed and closed form bristle tip force (BTF) function is derived where rotor-bristle, inter-bristle and bristle-back plate interactions are included. BTF measurements under pressurized and unpressurized air environment are conducted for the selected test seals by using the custom ‘Rotary Test Rig’. BTF function of bristle contact force theory show high level of correlation with the test data. The effect of cant angle manufacturing tolerance on bristle tip force levels is also examined through bristle tip contact force theory, and compared with the test seal measurements. Methodology for number of bristle row calculation and comparison with the geometric inspection of test seals are also detailed within the content of this paper.

At low operating temperatures, the power capability and charging/discharging capacity of lithium-ion (Li-ion) batteries can decay rapidly. Therefore, it is essential to preheat the Li-ion batteries in advance of the normal operations of a battery electric vehicle. High-frequency AC preheating methods are advantageous to achieve a miniaturized and lightweight design. In this paper, a self-heating circuit topology is used for studying the characteristics of Li-ion batteries at low temperatures and under high-frequency AC excitation. The thermal behaviors of Li-ion batteries under high-frequency AC excitations are comprehensively analyzed with an improved heat generation model. Experimental results exhibit that heat generation due to electrochemical reactions has a significant influence on self-heating rates under the high-frequency AC excitation, and the heating rate is positively correlated with the current frequency and root-mean-square (RMS) value. Specifically, when the current frequency is 90 kHz and the RMS value is 3.51 A or 1.17C, validated by experiment and numerical simulation, a 2.9Ah 18650 Li-ion cell can be heated up from -20 °C to 5 °C in 7.33 min with an average electrochemical heat generation of 2.962 W.

Thermal diffusion and wave phenomena in a two-dimensional solid subjected to convective cooling and an internal exponential heat source are investigated. Both diffusion and Cattaneo–Vernotte (C–V) ...

Thermal management of electrical machines is an important issue to improve electromagnetic performance, reduce system size and prolong lifetime. Based on the equivalent thermal circuit (ETC) and computational fluid dynamics (CFD) methods, the temperature rise characteristic of a high-speed stator-permanent magnet-type flux switching (HS-SPMFS) machine for fuel-cell electric vehicle compressor is predicted. Firstly, the structural features, key dimensions, material properties and heat generation rate of the HS-SPMFS machine and its cooling system are introduced. Secondly, the ETC model of the machine with a liquid cooling channel is proposed, and the size of the cooling system is preliminarily designed. The influence mechanism of the number, size and flow rate of the water channel on the convective heat transfer area, convective heat transfer coefficient, water head loss and winding temperature rise is revealed. On this basis, combined with the CFD method, the temperature distribution of the machine is studied, and the detailed temperature distributions of each component of the machine are obtained and verified by the ETC method considering the cooling system. Finally, a HS-SPMFS machine prototype is manufactured and the temperature test platform of the prototype is built. The temperature rise behaviors of the machine under different working conditions are tested, verifying the theoretical analysis and the prediction methods.

Boilers are one of the most used units for both heat generation plants and industry systems. Their operation is subjected to different working loads and maintenance requirements. Exploitation experience points out critical boiler zones where failures and break downs typically occur. This paper analyzes critical zones in hot water fire-tube boiler. Experimental procedure was performed on the model of this type of boilers and its critical element. The tube plate of hot water boiler was identified as the most critical one. Experimental analysis and numerical model verification were performed using Aramis system based on 3D Digital Image Correlation method. Numerical analysis was done in Ansys Software Package and verification of results was done based on measurements obtained by strain gauges and local measurements performed by the Aramis system. Stress-strain analysis indicates the critical zones of boiler tube plate. The character of change parameters such as strain and stress occurring in the critical zones can be verified both by experimental and numerical data. The paper presents a novel approach in experimental and numerical analyses that can be conducted in similar units and used for existing unit optimization, as well as for new product testing on different loads and provide opportunity for further development and improvement for practical industrial application.

Recent research findings indicate that the non-monotonic consumption of energy from lithium-ion (Li-ion) batteries results in a higher heat generation in electrical energy storage systems. During peak demands, a higher heat generation due to high discharging current increases the temperature from 80 °C to 120 °C, thereby resulting in thermal runaway. To address peak demands, an additional electrical energy storage component, namely supercapacitor (SC), is being investigated by various research groups. This paper provides insights into the capability of SCs in lightweight electric vehicles (EVs) to address peak demands using the worldwide harmonized light-duty driving test cycle (WLTC) driving profile in MATLAB/Simulink at different ambient temperatures. Simulation results indicate that temperature imposes a more prominent effect on Li-ion batteries compared with SCs under peak demand conditions. The effect of the discharging rate limit on the Li-ion battery current is studied. The result shows that SCs can accommodate the peak demands for a low discharging current limit on the battery, thereby reducing heat generation. Electrochemical impedance spectroscopy and cyclic voltammetry are performed on SCs to analyze their thermal performance at different temperatures ranging from 0 °C to 75 °C under different bias values of −0.6, 0, 0.6, and 1 V, respectively. The results indicate a higher specific capacitance of the SC at an optimum operation temperature of 25 °C for the studied bias. This study shows that the hybrid combination of the Li-ion battery and SC for a light-weight EV can address peak demands by reducing thermal stress on the Li-ion battery and increasing the driving range.

Machining of difficult to cut material at advanced range of process parameters is the requirement of modern day machining scenario for achieving the goals of sustainable machining through utilization of modern cooling techniques to minimizing the friction, heat generation and tool damage. Consequently, leads to profitable machining under the provision of suitable volume, application method and environmental friendly cutting fluids. Contrary to this, larger flow rate and inferior methodology of cutting fluid application leads to various health problems, environment issues and imperfect product quality. So, to achieve targets the sustainable machining, the firm has to meet certain environmental norms regarding the application and disposal of cutting fluids. Therefore, to tackle the aforementioned ecological issues the dry machining is preferred which exhibit solution, but this option does not endure economic plan at accelerated machining parameter levels due to lower tool life and impaired quality of product. Hence, the alternative to all these situations are the requirement of such a cooling system which does not pollute the environment, operator friendly as well as economical to use. Henceforth, the minimum quantity lubrication using soybean oil has been used in present investigation as a replacement to flood lubrication. The experiments have been conducted on EN-31 Steel taking advanced ranges of machining parameter in dry and M.Q.L system. Research outcomes revealed that the M.Q.L machining improved the surface finish, lowered the cutting temperature and enhanced the chip reduction coefficient with comparison to dry machining system. The Parametric optimization evaluated by TOPSIS approach pointed out that the best machining combination has been observed at 196 m/min, 0.088 mm/rev in vegetable oil environment.

Heat generation in integrated circuits (ICs) has become a severe issue, which limits the utilization of miniaturized semiconductor devices in high-density 3-D IC technologies. Herein, Al₂O₃ was doped in ZrO₂ thin films by plasma-enhanced atomic layer deposition (PEALD) to enhance their antiferroelectric (AFE) characteristics for highly reliable electrocaloric (EC) cooling applications. The cycling endurance in AFE behaviors of the Al:ZrO₂ thin films under a high electric field of 5 MV/cm was significantly improved because of the enlargement of the energy bandgap with high resistance in trap-induced leakage current. Hence, the reliability of the EC effect of the 1% Al:ZrO₂ thin film was examined with a negligible change in adiabatic temperature change (Δ T) of 2.6% after a cycling endurance test of 10⁶ cycles. With the competitive cycling reliabilities in AFE and EC behaviors, devices with optimized Al₂O₃-incorporated ZrO₂ thin films show significant potential for future nanoscale cooling systems in chip-level ICs.

The thermal resistance of a high electron mobility transistor (HEMT) forming part of a monolithic microwave integrated circuit (MMIC) is noninvasively extracted under real working conditions (electrical and thermal) by infrared thermal imaging. The HEMT thermal resistance considers the device local maximum temperature and dissipated power. An experimental approach to this end is currently not available, as the HEMTs thermal interaction does not allow extracting its individual heat generation. Thanks to thermal field confinement offered by heat source frequency modulation, the power dissipation in each device is inferred, making feasible its individual thermal resistance extraction. As a result, reasonable values of the local thermal resistance of each individual HEMT integrated in the MMIC (i.e., 57.8 ± 3.4 °C/W and 24.8 ± 1.4 °C/W) are obtained in agreement with studies on discrete devices available in the literature.

The knowledge of cutting forces in various machining processes is of great importance not only for the designer-manufacturer of machine tools, but also for the user, since the cutting force governs cutting heat generation, tool life, and machining accuracy. In this regard, lots of investigations have been conducted on the cutting forces by developing different types of prediction models to make appropriate estimations, which are grouped into the analytical, empirical, and numerical methods. This paper conducts a survey on the development of analytical cutting force models for the orthogonal turning/cutting process. The analytical force models developed from the shear theory are detailed reviewed, and other analytical modeling methods for specially-designed tools, advanced materials, and special kinematics are also presented. The modeling laws and key challenges are also discussed for future researches.

In nanoscale FETs, the confined geometry and increased packaging density induce increased power density, which translates into larger heat generation. The substrate’s low thermal conductivity also leads to poor heat dissipation, leading to a further rise in temperature and aggravated self-heating effects (SHEs). The incessant scaling of transistor size demands a rigorous study on the impact of SHEs and ambient temperature variations on advanced MOSFET structures’ electrical characteristics. Therefore, in this work, an investigation on the electro-thermal (ET) behaviour of the nanoscale RingFET has been conducted using the Sentaurus TCAD device simulator. The hydrodynamic carrier transport model has been used in 3-D ET simulations to analyze the ET behaviour of the RingFET. A comparative analysis of the DC characteristics with and without SHEs has been presented via current-voltage and transconductance-voltage characteristics, which are further used to compute the ZTC (zero temperature coefficient) bias point. A detailed analysis of the device’s electrical behaviour with the variation in channel length, gate oxide thickness, substrate doping, and drain radius has also been presented. Finally, the influence of SHEs on device characteristics at various ambient temperatures has also been reported.

Thailand has increased continuously of renewable energy because of the Alternative Energy Development Plan (AEDP) is targeted at increasing renewable energy use in all sectors. In addition to reducing the use of fossil fuels and energy imports from abroad, it also affects the greenhouse gases (GHG) emission reduction that is a major cause of climate change. In 2019, thermal energy consumption from renewable energy was 60.3% of total final renewable energy consumption. This study aims to assess the marginal abatement costs (MAC) in Thailand renewable energy heat generation which is consisting of (i) the type of natural renewable: solar energy, and (ii) the type of bio-renewable: biomass, biogas, and waste during 2014 to 2018. In 2018, the MAC results range from −18,757.67 to 3,718.38 THB/tCO 2eq. Marginal abatement costs (MAC) are the important tools for prioritizing in GHG reduction strategy which represents the importance and necessity of heat generation from renewable energy that affects to the GHG reduction of the country by expression the form of marginal abatement cost curves (MAC Curve). In addition, it is also a climate change economics indicator that is essential for the Long-term Low Greenhouse Gas Emission Development Strategy (LT-LEDS) of Thailand to affect the operations that will lead to sustainable development in society, economy, and environment to achieve Net-zero targets.

For minimizing the operational cost of an integrated hybrid system, which provides electricity, heating, cooling and water of a residential complex, a new energy management method presented here. The proposed energy management method uses the principles of Reinforcement Learning (RL) based on Deep Q Network (DQN) algorithm to find the operational strategy for the hybrid system. Unlike the stochastic presentation of RL with Markov Decision Process (MDP) in literature, a deterministic approach proposed in this study for energy management of a hybrid system. This presented approach does not require online trial and error or historical data of system performance to determine the operational strategy. This developed RL-DQN method used for energy management of a hybrid system with photovoltaic collectors, ET collectors, wind turbines, CHP units, a water heater, a hot water storage tank and batteries. Thus for a residential complex with variable electrical and thermal loads during a year (8760 h), RL-DQN energy management method estimated two unknown variables in operational strategy, i.e., the partial load of the CHP unit and the amount of heat generation by LPG-fueled water heater. The results of RL-DQN energy management also compared with results of two rule-based methods. The results show a reduction of the operating cost to 10983 $/year by RL-DQN which is lower 6.5% and 30.4% than that for two above mentioned rule-based methods. Lower CO2 production (2.8% and 62.8%) also observed in comparison with that for two above mentioned rule based methods. With the proposed EM method, 80.1% of the required electricity supplied with renewable energies and 82.2% of the thermal load supplied without direct consumption of fossil fuels. The benefit of using predicted load and renewable energies of future hours also investigated for EM. Results show that employing the predicted information decrease the operational cost by about 3.5 percent

Flip chip (FC) light emitting diodes (LEDs) are considered to be more promising in solid state lighting as compared to wire bonded LEDs. For solid-state lighting, thermal management is a very critical factor to enhance the device’s performance. In the Flip Chip Light Emitting Diode (LED), the active region is the main source of heat generation. This heat is to be conducted through different layers to the heat sink. The adhesive layer and bump assembly cause heat dissipation because of their low conductivity values and poor transparency and hence cause degradation in performance of FC-LEDs. In this paper, thermal analysis of flip chip LED is done to find out how material, size of die and bumps affect the thermal performance of FC-LED. A flip chip LED structure is modeled on a GaN substrate. Different material properties of silicon, gold, and aluminum have been studied to perform the thermal analysis and to see the effects of different die sizes, bump sizes, and adhesive materials. Thermal analysis of the high-power FC LED by using the Finite Element Method is done on Ansys Software. The FC structure and its meshing design are presented.Temperature variation with different sizes of bump, chip-die and different adhesives (silver filled epoxy, Au-Sn, Pb-Sn) on flip chip LED is discussed. The result shows that thermal heat is directly proportional to the size of the bump and the type of adhesive material selected also affects the performance of FC-LEDto some extent.

Combustion of fossil fuels is the most important source of polycyclic aromatic hydrocarbons (PAHs) in the environment. Cities are typical of many human activities which are dependent on fossil fuels (road and railway transport, heat generation, waste incineration and industry) on a small area, leading to high concentrations of PAHs in urban air, dust and soil. The aim of this study was to determine the possible influence of urban traffic on the accumulation of sixteen priority PAHs in soils (n = 132 at two soil depths of 0–10 cm and 10–20 cm) taken at intersections (n = 37) with different traffic volumes and road ages. Variable concentrations of the sum of PAHs (∑16PAH) ranging from 188 to 21,950 μg/kg with a mean and median of 3021 μg/kg and 1930 μg/kg were recorded, respectively. Concentrations of PAHs positively correlated with soil organic carbon content (TOC) (rSpearman = 0.518; p

Research focus (problem description, short background): The energy efficiency of a district heating (DH) system can be improved by fine-tuning supply and return temperatures and flow rates without need for invasive renovation of the end user heating systems. Research methods: We employ a correlation coefficient to examine the relationship between the local supply temperature and the use of heat; research relies on data hourly heat generation records from each heat generation facility in the DH system of Omsk, Russia, 2016–2017. Key research results/findings: The correlation declines the further we go from winter. Firstly, the relationship between the transition states and the outside temperature results from the relationship between external conditionings and heat parameters in DH. Secondly, both the energy consumption and the supply temperature are affected by the infrastructure, other weather conditions, and energy price; they are also highly dependent on consumer behavior, which is arbitrary, heterogeneous, and interdependent. Thirdly, the regional heating load is influenced by the characteristics of a building cluster. Although nearly all DH plants have a control system in place, we find that human factor jeopardizes the performance of such systems. Main conclusions and recommendations: To generalize these results to other systems, we emphasize that the effective diffusion coefficients and effective heat-loss coefficients are influenced by the thermal dynamics in the network and change on typical time scale (one year), hence their uncertainty. This study has produced a technique for visualizing the relationship that exists in a DH system between supply temperature and heat consumption; this technique is expected to contribute to the dynamic modeling, control, and planning of future integrated energy systems. The load profiles are dynamic; a thermal storage could be used to shift the timing of heating loads to minimize the flow through DH networks.

District heating and cooling (DHC) networks are traditionally operated with a limited number of controls to secure the required supply task and to optimize economics and ecologic performance. An optimized heat generation and overall network operation is possible with more information on the demand and flexibility options. A wider implementation of information and communication technologies opens up for better network management based on real time measurement data and for the integration of new digital business processes. For a further development it is needed to promote the opportunities of the integration of digital processes into DHC systems and to clarify the role of digitalization for different parts within district heating and cooling systems. Digital technologies are believed to make the whole energy system smarter, more efficient and reliable and to boost the efficiency and the integration of more renewables into the system. In the future, digital applications might enable district energy systems to fully optimize their plant and network operation while empowering the end consumer. On the other hand new challenges need to be tackled, such as data security and privacy as well as questions about data ownership. The paper presents and discusses the first results from the starting research work within the IEA DHC Annex TS4 on Digitalization of District Heating Systems – Optimized Operation and Maintenance of District Heating and Cooling Systems via Digital Process Management.

With regard to the decarbonisation of the heating sector, district heating is of paramount importance considering its potential for the efficient utilisation of renewable energies and waste heat sources. Against this background, the transformation and expansion of an existing heating network in the city of Moosburg an der Isar (Germany) is planned within the “District Heating 4.0” funding programme of the German Federal Office of Economic Affairs and Export Control. The innovative concept involves a heat supply based entirely on renewable energies and industrial waste heat. In particular, the integration of unused waste heat from mechanical and chemical industrial processes enables an ecologically and economically optimal supply concept. Depending on the temperature level, the waste heat is fed into the grid directly or by an intermediate heat pump. In addition, solar thermal systems on roofs are integrated into the grid and optimised in terms of efficiency by using a heat storage. Biomass boilers operated by woodchips of waste wood cover peak loads as well as part of the base load and guarantee the security of supply. Considering the overall system behaviour, the multivalent concept is designed to maximise the share of renewable fuel-free heat sources and capitalise on the beneficial marginal costs of waste heat and solar thermal energy. A profitability analysis shows that low heat generation costs can be realised, not least because of the funding of investment costs. In addition to the technical design process and the economic evaluation, the analysis of legal aspects is a key element of this first phase of the project. In further project phases, the implementation of the heating network, the monitoring of the energy flows and the ongoing acquisition of new customers will be carried out.

A cooling technology roadmap is defined for power electronics modules such as insulated gate bipolar transistors (IGBT) and wideband gap semiconductor modules (SiC/GaN). These power modules are widely used for inverter and converter applications. Cooling technologies studied include natural air cooling, forced air cooling, forced liquid cooling, and thermal management technologies employing phase change. This work reviews the standard modes of failures of power electronics modules. The work helps to understand the thermal resistances at various interfaces in the module stack. The study highlights the importance of using electrothermal models for power loss estimation. Effective thermal management must ensure the power electronics components' junction (die) temperature is within the desired limits. The developed cooling technology roadmap suggests using heat flux at the module base and heat generation per temperature rise in the die as a metric for selecting cooling technology. Further, the review also stresses the importance of junction temperature swings experienced by the die during transient operation.

Background Skeletal muscle as a metabolic consumer determines systemic energy homeostasis by regulating myofibre type conversion and muscle mass control. Perturbation of the skeletal muscle metabolism elevates the risk of a variety of diseases including metabolic disorders. However, the regulatory pathways and molecules are not completely understood. The discovery of relevant responsible molecules and the associated network could be an attractive strategy to overcome diseases associated with muscle problems. Methods An initial screening using quantitative trait locus analysis enabled us to extract a set of genes including ubiquitin‐specific proteases21 (USP21) (r = 0.738; P = 0.004) as potential targets associated with fasting blood glucose content. Given tight regulation of the ubiquitination status of proteins in muscle, we focused on USP21 and generated whole‐body (KO) and skeletal muscle‐specific USP21 knockout (MKO) mice. Transcriptomics, proteomics, and lipidomics assays in combination with various in vivo and in vitro experiments were performed to understand the functions of USP21 and underlying mechanisms. A high‐fat diet (60%)‐fed mouse model and diabetic patient‐derived samples were utilized to assess the effects of USP21 on energy metabolism in skeletal muscle. Results USP21 was highly expressed in both human and mouse skeletal muscle, and controlled skeletal muscle oxidative capacity and fuel consumption. USP21‐KO or USP21‐MKO significantly promoted oxidative fibre type changes (Δ36.6% or Δ47.2%), muscle mass increase (Δ13.8% to Δ22.8%), and energy expenditure through mitochondrial biogenesis, fatty acid oxidation, and UCP2/3 induction (P

This study presents a novel structure for electrochemical discharge machining (WECDM) of nonconductive quartz wafers with continuous electrolyte flow. A small and stable insulating gas film was formed in the gap between the wire electrode and workpiece to achieve improved WECDM in a small area. A pulsed power supply and ultrasonic-assisted processing were combined to machine the quartz workpiece. This approach can considerably reduce unstable discharge phenomena and discharge heat generation. Furthermore, it can avoid easy breakage and subsequent loss of the wire electrode. The machining accuracy and the machining speed can be improved using appropriate WECDM parameters. Experimental results revealed that a minimum slot width of 0.208 mm was obtained at a voltage of 44 V, duration time of 100 μs, duty factor of 40%, feed rate of 20 μm/s, and ultrasonic power level of 2. Accordingly, the proposed design can obtain a smaller slot width, which improves processing accuracy.

The need for weight reduction in aerospace and automotive industries requires use of lightweight materials. In order to attain the aforementioned, joining of dissimilar materials such as steel and aluminum came into practice. Friction stir spot welding is a solid-state welding technique capable of joining the materials with wide variation in their properties. This paper discusses the friction stir spot welding process and its variants along with effect of heat generation and material flow on the macrostructure, and mechanical behaviour of FSSW aluminum alloys. Finally, the major issues in friction spot stir welding will be discussed followed by the summary of outcomes and the scope for future work.

Real-time monitoring of heat loads in cryogenic systems is critical for many applications, particularly high field magnets. We demonstrated that by monitoring changes in the capacitance of local probes consisting of thin metal strips with a porous glass fiber dielectric, boiling helium from as little as 0.1 J of deposited heat can be located by an analysis of the response speed and amplitude in nearby probes. We further implemented stray-capacitance monitoring of a magnet's metal support structures, a more global probe of the magnet volumes, in three high temperature superconducting Bi-2212 magnet types. Global structural stray-capacitance monitoring was evaluated for a single racetrack coil, a common coil dipole, and a canted cosine theta winding, showing a quench response comparable to voltage signals without inductive effects. The response of the local and global probes was compared in the single racetrack coil with well-known quench properties. Monitoring the cool-down of the common coil dipole demonstrated the added benefit of the global stray-capacitance as a liquid level monitor. This simple method of monitoring the capacitance has proven to be a versatile and robust technique for monitoring and locating heat.

Aims: The aim of this study was to assess temperature changes of dental implant body when using different wattage of diode laser (Fox laser 1064-nm) and set a proposed power setting that has no detrimental effect on adjacent bone. Materials and Methods: Seventy-five Titanium implants with healing screws were used in this study. Thermocouple technology was used to measure the temperature level generated in the dental im-plant body when being exposed to laser. The implants were fixed in an acrylic mandible model and then placed in a controlled water bath at 37 °C. Time to reach a temperature degree of 47 °C were recorded after each wattage as well as the dropping time of temperature to reach a degree of 37° C was recorded. Results: The decrease in time needed to reach 47 °C was directly related to an increase in wattage and as such the time is inversely related to wattage. All the recording time measures dropped to 37 °C with no significant differences. Conclusion: It can be concluded that using diode laser in at 6 wattages with pulsed wave settings produced high temperature with minimum time compared when using 2 wattage settings which needed more time to produce the same heat

The paper presents the results of studies aimed to increase the efficiency of centralized heating networks by improving heat supply control at the plant and at the local level. With this in view, we considered issues of choosing the optimal heat supply schedule and its influence on the efficiency of heat generation, transportation and use, as well as the influence of the heat carrier temperature on heat losses at the corner of the temperature curve. We also studied the influence of the heat carrier temperature in the return pipe of heating networks on the operation of heat generators by using various control methods. Another issue considered in the course of the study was the issue of ensuring the hydraulic and thermal stability of heating networks and heating systems connected to them by using the combined control method. The methodology of the study was based on the analysis of heat balance equations for the steady-state operation of a complex including a heating network and a building’s heating system. As a result, we obtained relationships that make it possible to determine the variation in the heat carrier flow rate and temperature depending on the heat load, as well as the reduction in energy consumption for heat carrier transportation. Recommendations were developed for the introduction of combined heat load control. A scheme for the reconstruction of central heat stations is proposed. The scientific and practical results of the study can be used to prevent significant heat losses, ensure optimal operation of heating networks, heat generators, and heating systems, reduce energy consumption, and increase the overall efficiency of centralized heating networks.

Heat generation during the Kirschner wire (K-wire) insertion process, under either unidirectional or oscillatory drilling mode, places bone at risk of thermal osteonecrosis which can lead to infection. There is a lack of quantitative understanding of the heat generation difference between the two drilling modes and knowledge of optimal thrust force level under each mode is missing. The goal of this study is to investigate the effects of drilling modes and thrust force levels on the bone drilling outcomes. Controlled machine-based constant thrust force K-wire insertion experiments were conducted with key process parameters monitored and compared quantitatively. Statistical analysis showed that the oscillatory mode consumed 2.6 times more electricity than the unidirectional mode but generated 53% less thermal energy and 23% lower peak temperature. However, the oscillation also led to 18% higher peak torque in the transient drilling stage and 23% shallower drilling depth. The optimal choice of the drilling mode depends on specific surgical needs to minimize bone damage (control of peak temperature vs. exposure time and torque control). Heat generation was dominated by the torque and corresponding rotational power under both modes. To minimize the bone temperature while keeping high drilling speed efficiency, a moderate thrust force is preferred under the unidirectional mode to balance between feed force and compressed debris resistance. For oscillatory mode, a small thrust force to keep the K-wire engaged with the bone is optimal.

A system analysis of energy production was performed comparing the system of photovoltaic panels and parabolic trough collectors with a hybrid absorber. The paper presents new design of hPTC-CPV absorber. The analysis includes a comparison of the performance of both technologies in different irradiance conditions over the year. The technologies were compared for the same active surface hPTC-CPV and PV. The analysis was performed for a single-family house based on its demand for heat, electricity, and cooling. The calculations are intended to show to what extent an analyzed renewable technology can cover the demand for particular types of energy. The analysis was carried out to assess the legitimacy of using hybrid radiation absorbers in a temperate climate. Hybrid absorber studies were performed using CFD software. The results show that the proposed technology can compete with a PV system in terms of cooling and heat generation. Hybrid absorber covers 74.7% of heat demand for absorption cooling. PV panels with a heat pump cover 44.3% of the heat demand, PV panels with electric heaters 24.3% and hPTC-CPV absorbers 23.3%. The proposed technology cannot compete with PVs in terms of electricity production. Hybrid absorbers cover 8.2% when PVs 71.9% of electricity demand.

In order to increase the optical features of white light-emitting diodes (WLEDs), quantum dots (QDs) and phosphor materials have been proposed because of outstanding performance. The configuration of WLEDs with QDs layer and phosphor-silicone layer suggested placing these components separately to limit light loss, and enhance consistency at contact surface of QDs. In this research, the effects of QDs and phosphor on the performance of WLEDs are concluded through experiments. The emitted light and PL spectra were examined thoroughly, and infrared thermal imagers were applied to simulate the heat generation of an actual WLED device. The results show that with the configuration of 60 mA energy source, WLEDs which has the QDs-on-phosphor form attained luminous efficiency (LE) of 110 lm/W, with color rendering index (CRI) of Ra=92 and R9=80, whereas the WLEDs which has the phosphor-on-QDs form only has 68 lm/W in LE, Ra=57 and R9=24. Furthermore, WLEDs which has the QDs-on-phosphor form has less high temperature generated at the components’ conjunction in comparison to the counterpart, the peak generated heat in QDs-on-phosphor WLEDs is also lower and the heating capacity gap between 2 structures can go up to 12.3°C.

Heat-assisted magnetic recording (HAMR) is one of the next generation technologies in data storage that can increase the areal density to beyond 1.5 Tb/in2. Near-field transducer (NFT) is a key component of the HAMR system that locally heats the recording medium by concentrating light below the diffraction limit using surface plasmons. In this work, we use density-based topology optimization for inverse design of NFT for a desired temperature profile in the recording medium. We first perform an inverse thermal calculation to obtain the required volumetric heat generation (electric field) for a desired temperature profile. Then an inverse electromagnetic design of NFT is performed for achieving the desired electric field. NFT designs for both generating a small heated spot size and a heated spot with desired aspect ratio in recording medium are demonstrated.

Concentrated photovoltaic (CPV) has been identified as an effective method to further enhance the efficiency of photovoltaic cells. Previous studies on CPV mainly focused on III-V multi-junction cells. Nevertheless, III-V CPV technology is mainly used in niche applications due to its high cost. Here, we use metal-halide perovskite solar cell (PSC) to demonstrate a concentrated photovoltaic-thermoelectric tandem device. The thermoelectric generator (TEG) is utilized to reduce the effect of heat generation under concentrated solar irradiance. Our tandem system achieved a peak power conversion efficiency (PCE) of 25.0% at a solar concentration of 3 suns. This efficiency exceeded that of the single PSC by ~4.7%. Our work proves that by controlling the heat flow in concentrated PSC-TEG tandem system, the redundant heat produced by upper PSC can be effectively reused. This tandem structure provides a promising approach to improve the efficiency and stability of PSC under low-concentrated solar irradiation.

The use of high temperature superconducting (HTS) power cables is viable solution to address the growing demand for electric power, while ensuring low loss and high electric power transmission. Usually, HTS power cables and circular connection of substations reduce grid impedance, and the fault current is increased over the capacity of the circuit breaker. To protect the electric power grid, the fault current should be reduced below the allowable level. Of late, research on HTS power cables having fault current limiting (FCL) functions has increased. An inductive FCL HTS power cable uses the increased inductive impedance caused by magnetic flux leakage to a neighboring iron yoke when a quench occurs at the shielding layer of the cable core due to electromagnetic coupling with the conducting layer. Therefore, there is less heat generation, and the temperature rise is suppressed. In this study, we describe the increased inductive impedance and reduced fault current using a FCL model coil. To demonstrate the electromagnetic coupling between the conducting and shielding layers of the cable core, two concentrically wound REBCO coils were fabricated. The iron yoke inside the coil increases the inductive impedance when a fault current flows through the conducting layer, and quench occurs at the shielding layer. The results are used to develop an FCL HTS power cable with 154 kV, 600 MVA class.

Introduction: A precise drilling-sequence-protocol is essential for long-term dental implant success in high bone density (mandibular cortical bone of D1-quality). Cone beam computed tomography (CBCT) radiographic imaging and CBCT-based construction of surgical guides have been substantial for diagnosis and treatment planning. Objectives: The study aimed to measure the effect of different guided drilling techniques on the amount of heat generated during implant placement in high density. Materials and Methods: Twenty-four osteotomies for implant placement, divided equally into three groups, to test the effect of the three drilling techniques " Undersized Drilling (UD), Undersized Drilling + Ridge Spreader size 4 (UD+RS4) and Undersized Drilling + counter sink size 4 (UD+CS4) techniques". Heat generation was assessed using K-type thermocouple. Drilling and thermocouple canals were guided by the surgical template. Bone assessment, virtual planning of the implants and surgical guide construction were based on radiographic CBCT-imaging and software-based processing. Insertion torque values (ITVs) were recorded from readings of a geared motor. Results: The thermocouple results showed the least significant difference at 10 mm depth. At 5mm depth, a significant decrease in the temperature difference of the UD+RS4 group and UD+CS4 group compared to UD group was observed. At 1mm depth, there was a significant difference between the UD group and the two other groups. The UD group showed the maximum peak ITV. Conclusion: the results suggest possible advantages when self-tapping implants are inserted into high density cortical bone of D1-quality by a countersink drill since it provides lesser temperature increase at insertion.

The presently employed synthetic cutting fluids in machining applications lead to skin irritations, hazardous aerosols, ingestion etc., to the machine tool operators. Accomplishing sustainable green machining through bio-cutting fluids, is the key motivating factor behind this work, even though the phenomenon of heat generation is inevitable in the machining process. In the present investigation, Citrullus lanatus extract is chosen as a potential candidate for bio-cutting fluid, since it offers multiple benefits such as increased tool life, cleaner production atmosphere, efficacious heat dissipation, healthy operating conditions, etc. Hybrid LM0-6SiCp-4Grp composite is selected for study since; it has potential applications in marine, aerospace, defence and automotive sectors. Experimentation is carried out with Citrullus lanatus extract as bio-cutting fluid in turning of hybrid LM0-6SiCp-4Grp composite under different processing conditions. The presence of green solution based on Citrullus lanatus extract curtails the rise of temperature significantly during turning operation. Higher magnitude of temperature decrease is observed when the percentage of the concentration of Citrullus lanatus extract is increased, irrespective of depth of turning. Bio-nature and cooling qualities of this green-cutting fluid can contribute its share for green machining and sustainable turning environment. The investigations are further progressed using machine learning algorithms based on the different categories of logical regressions implemented through the Python program. Random forest regression shows better results with 99.8% prediction accuracy compared to other machine learning approaches and the decision tree is constructed through the respective regression model. Decision tree has the ability to handle process parameters systematically and predicts the implications of Citrullus lanatus extract in decreasing the temperature at machine-tool interface during machining operation. This tree structured analysis provides a better inference that delivers flexibility in turning parameters and opens up wider options for operation. Thus, decision tree approach ensures optimized usage of production resources and increases the production capacity through judicial selection of cooling approaches associated with the turning process.

The axial thermal errors of CNC lathes are mostly caused by the thermal deformation of the screw and spindle. It is necessary to establish a prediction model to evaluate the thermal error distribution of CNC lathes. First, a new real-time virtual frictional heat model under the time-varying working speed of various kinematic pairs in the screw and spindle systems was proposed using the real-time torque current. Furthermore, a novel one-dimension lumped capacity method, which can be used to determine the temperature field rapidly, was proposed, considering the sensitiveness of the temperature of the measuring point with the heat generation rate. By an inverse FEM thermal-solid method of screw and spindle systems, the friction heat distribution and sensitiveness of the temperature of the measuring point with the heat generation rate were obtained. Consequently, based on the one-dimension lumped capacity method, the real-time thermal error prediction model was established, which is used to predict the temperatures and axial thermal errors of the screw and spindle of the machine tools. From the FANUC digit control system, the servomotor torque currents of the screw and spindle and the position of the moving-nut were read and used as inputs by the FOCAS library function. The effectiveness of the proposed prediction model of thermal errors is verified through the experimental and FEM results. This method uses the servomotor torque current collected by the FOCAS library function to determine the heat boundary condition. It can quickly and accurately determine the thermal errors without requiring additional temperature sensors.

This article proposes a liquid-cooled battery thermal management system based on a serial-parallel mini-channel cold plate to solve the problem of severe heat generation during high-rate battery di...

For decades, attentions have been paid to metal cutting processes, especially for the critical components in aerospace, marine, medical industries, etc. Scholars investigated the influence of cutting parameters, tool geometry, lubricant, pursuing a deeper understanding of process signatures, better tool performance, and more superior surface integrity. Edge microgeometry is proved to be an essential factor that significantly influences the tool-workpiece-chip contact, plastic deformation, and heat generation, which in turn affects the cutting phenomena. This paper aims to provide an insight and scientific overview of the role of edge microgeometries in metal cutting, with special attention on material flow state, cutting mechanics, tool performance, as well as the surface integrity. The characterization of edge microgeometries includes edge types (honed, chamfered, mixed), size parameters (edge radius, form-factor K, chamfer angle, chamfer length), and edge preparation techniques (grinding, drag finishing, brushing, micro-blasting, etc.). The researches on the influence of edge microgeometries on material flow state and cutting mechanics are reviewed, mainly focusing on analytical modeling and finite element method to explain how the edge microgeometries affect cutting processes. Then, the researches on the influence of edge microgeometries on tool performance and surface integrity are well organized to present the various findings in these topics. From the current perspective, many scholars have noticed the importance of edge microgeometries in metal cutting and have done numerous researches on this topic. Summary and future suggestions are given based on their state-of-the-art contributions in the last section.

Coke oven gas (COG) is used to generate energy for the iron-making process by burning; however, from an environmental point of view, it can be converted to methanol (MeOH) for effective utilization. This study designs a large-scale process for the MeOH production from COG based on the validated kinetic studies and performs a life cycle assessment (LCA) of the proposed process. The LCA results are compared with those of the conventional option of COG energy generation combined with primary source-based MeOH production by defining the “cradle-to-gate” system boundary and applying the ReCiPe 2016 Midpoint level methodology using SimaPro 9.0 software. Consequently, the LCA results show that the global warming (GW) and fossil resource scarcity (FRS) of the new COG process are lower than those of the conventional option by 64.8% and 38.0%, respectively. The GW and FRS impacts of the new COG process are dominated by the displacement effect of the heat generation of COG by the primary source. Using wood chips as a primary source could reduce both GW and FRS, leading to a carbon-negative (− 0.51 kg CO2 eq.) COG process.

The paper presents an experimental investigation of a solar dish concentrating system with thermal collectors, along with a numerical investigation of a solar cooling installation based on such system by means of dynamic simulation. The main aim of this study is the analysis of heat generation from the system for heating and cooling purposes, with the use of sorption chillers. A computer simulation of the dynamic operation of the proposed solar heating and cooling system was developed within TRNSYS software. The experimental data were used to validate the model of the concentrator and solar collectors. Successively, a solar heating and cooling installation for a residential application, integrating the different configurations of solar energy collecting devices and thermally driven chillers, was proposed and dynamically simulated. Flat-plate, evacuated tube and photovoltaic-thermal collectors were considered along with absorption and adsorption chiller units. In the present study, different system configurations, localities and time bases were considered to investigate the energy and economic performance of the system. The model of the solar dish and collector arrangement overestimates the produced energy by less than 5% as compared to the experimental study. The results show that the space cooling demand is matched in 23.6 and 46.2% by solar energy in Warsaw, while in Lisbon from 38.2 to 46.1%. The simple payback period of the investigated system configuration was for Warsaw between 18.1 years for the combination of flat-plate collector and absorption chiller and 27.2 year for the photovoltaic-thermal collector with adsorption chiller.

This article proposes the one-package structure of –1 MV direct current (dc) filter circuit and dc measurement system composed of dc voltage dividers and dc current transducers (DCCTs). These apparatuses are becoming more important for the expansion of high-voltage dc (HVDC) power grids. However, at present, they are separately installed keeping a huge distance for air insulation, and an increase in equipment size and footprint has become a major issue. We succeeded in reducing the footprint to 1/100 by storing the aforementioned HVDC vital parts in one package of a pressure vessel. Our developed configuration uses sulfur hexafluoride (SF6) gas not only for insulation purpose but also as a refrigerant to forcibly ventilate vertically in order to allow the dc filter circuit, which is heat generation source, and the dc measuring instruments, which need to minimize the effect of temperature drift, to coexist. We also addressed another issue caused by the limited space in the one-package structure, where the stray capacitance of the dc voltage divider tends to become large and then lowers the measurement accuracy for transient voltage variation. As a countermeasure, the dc voltage divider is composed of much larger capacitance than the stray capacitance and additional damping resistance to avoid LC resonance with wiring inductance. The actual-product tests demonstrated the followings; the dc measurement system has satisfied high measurement accuracy of 0.5% and fast responsivity of 3.3 μ s retaining decay rate within −3 dB; the temperature rise of the dc voltage dividers and the DCCTs is reasonably suppressed; the dc measurement system and the dc filter circuit withstood DC −1.2 MV.

The paper investigates the basics for increasing the productivity of gas-phase catalytic oxidation processes effected in multi-tubular reactors due to their operation at more concentrated feedstock. Obviously, an increase in initial concentration of the oxidizable reagent seems very attractive, but it is associated with the need to modify the process parameters and/or technological chart in order to achieve the required performance figures. This often entails excessive formation of by-products and therefore overheating of the catalyst bed due to increased heat generation. The cumulative effect of many factors can prevent attaining an acceptably high conversion of feedstock and the yield of target products within a reasonable size of a multi-tubular reactor. The problems we studied are quite typical for highly exothermic catalytic oxidation processes, but are not widely discussed in the literature. On the example of nicotinic acid (NA) synthesis in multi-tubular reactor, we investigated the advantages of the process with elevated feed load (β-picoline), in comparison with the conventional conditions. On the basis of comprehensive process simulation supported by the experimental evidence, for the first time we have shown how the process should be operated to achieve a significant progress in the reactor performance and the target product yield. Our theoretical study showed that the rise in the initial β-picoline concentration from ∼0.8 to ∼3% accompanied by a relevant adjusting of the process parameters leads to a dramatic 1.5–2-fold gain in the specific productivity of catalyst; this could greatly improve the reactor capacity. Optionally, a given production capacity of multi-tubular reactor may be ensured by ∼2 times less number of tubes. Thus, the synthesis of NA at elevated initial feed of β-picoline shall be significantly enhanced in comparison with the conventional process.

Biomemristors have attracted significant attention because of their potential applications in logic operations, nonvolatile memory, and synaptic emulators, thus leading to the urgent need to improve memristive performance. In this work, a silk fibroin (SF)-based memristor, integrated with both low power and low operating current simultaneously, has been reported. Doping the SF with Ag and an ethanol-based post-treatment promote microcrystal formation in the bulk of the SF. This induces carrier transport along fixed, short paths and results in a low set voltage, low operating current, and high memristive stability. Such performances can greatly reduce power consumption and heat generation, beneficial for the accuracy and durability of memristor devices. The memristive mechanism of SF-based memristors with different Ag contents is the space-charge-limited conduction (SCLC) mechanism. In addition, the nonlinear transmission property of SF-based memristors suggests useful applications in bioelectronics.

To deeply explore the spontaneous combustion disaster of coal caused by air leakage and oxygen supply, low-temperature coal oxidation experiments under different oxygen concentrations (DOC) were carried out. Within the coal spontaneous combustion characteristic measurement system, a synchronous thermal analyzer (STA) and a Fourier transform infrared spectrometer (FTIR), the macro laws of gas and heat generation under DOC are analyzed, and the mechanism of the development of coal spontaneous combustion restricted by the lean-oxygen environment is also revealed. The results show that the change of oxygen concentration (OC) does not affect the critical temperature value and gas index change trend, but the lean-oxygen environment reduces the gas concentration and heat production rate very obviously. According to the temperature of the intersection, OC needs to be lowered to less than 5% when preventing spontaneous combustion of coal. The chain thermal reaction lags in the lean-oxygen environment, and the pyrolysis activity is significantly reduced. Meanwhile, the temperature points at T6 and T7 show significant differences. Furthermore, with increasing OC and temperature, the content of the aliphatic hydrocarbon presents an overall trend of first increasing, then decreasing, and continuously increasing after stage IV. It is concluded that •OH, aliphatic hydrocarbons, aromatic hydrocarbons, and carboxyl groups are the key groups for the coal spontaneous combustion evolution under DOC. To combine the spontaneous combustion reaction of coal in the DOC environment, the reaction path of the index gas in the macroscopic phenomenon and the reason for the concentration differences are revealed, the mechanism for exotherm varies caused by OC is clarified, and the microscopic inhibition affection on the chain reaction within the lean-oxygen environment is also explored. The results put forward the key groups evolution mechanism under the DOC for coal oxidation, which could provide the technical guidance for the fire prevention and control on coal mines.

Solar energy is abundantly available energy for the generation of heat, and one the best appliances used for this purpose is Induction heaters. For the heat generation application, the combination of solar energy with the induction heat generation technique is the productive solution. Due to high efficiency and high-power density, resonant converters with soft switching are commonly utilized in domestic induction heating applications. For induction heating applications, a low profile and an improved efficiency resonant inverter design and implementation procedure are presented. Reducing conduction losses by using automotive-grade MOSFET devices against the classical IGBT-based converter. Conversion efficiency can be increased by decreasing switching losses which can be done by reducing switching times of MOSFET devices. Heating the metallic pan with circulating eddy currents induced by a high-frequency AC magnetic field is the principle of the induction cooker. If the load has an electrically conducting base, then the coil within the induction cooker and the load (pan/pot) acts as a transformer. The power will be transferred with high efficiency if the conducting base is ferromagnetic. An efficient control scheme incorporated in class E resonance heating by using solar power is presented. The simulation analysis is done in MATLAB-SIMULINK. Index Terms: induction heating, solar energy, class E resonant converter, MOSFET, MATLAB-SIMULINK

The recent social care about the concentration of plastics in the ocean arises with the necessity of developing solutions to this problem. Some projects are dealing with the technology of collection, however, the follow-up transfer onshore is not usually included in the solution. This study suggests designing a vessel with available waste treatment technologies that can use the waste to recover energy. Simultaneously, the technologic vessel has to regularly visit collectors and ports to supply produced commodities and crew. A mixed integer linear model is developed to find the optimal balance between capacities of considered technologies and also to simulate the voyage with all respective operations. Waste-to-Energy, pyrolysis, desalination, sorting and other mechanical processes are assumed onboard. The vessel is designed to utilize the produced energy and products onboard including heat generation, electricity, water, and oil. The evaluation of suitable technologies is realized through techno-economic models which are needed for all considered subsystems from the complex treatment chain. The analysis of project viability requires detailed multi-disciplinary data. The main output of the presented approach is sensitivity analysis for critical parameters, which gives greater insight into the issue and directs further research from a general level through the concept to refine the input data and boundary conditions of the task in the model. The Pacific Garbage Patch was chosen as the testing area for the case study. The presented approach enables to compare different ways of plastic processing.

Background We examined the effect of Kirschner wire (K-wire) reuse and use of oscillating mode on heat generation within cortical bone. Methods Two trocar-tipped K-wires were drilled through the diaphysis of each of 30 human metacarpals and phalanges: one K-wire was inserted in rotary mode and another in oscillating mode. Each wire was reused once. Thermocouples placed within the dorsal and volar bone adjacent to the K-wire drill path measured temperatures throughout each test. Results Peak cortex temperatures were 25°C to 164°C. Rotary drilling achieves peak temperatures quicker (31 ± 78 seconds vs 44 ± 78 seconds, P = .19) than oscillating drilling, but insertion time is also less, resulting in lower overall heat exposure. This effect is also seen when the K-wire is reused (34 ± 70 seconds vs 41 ± 85 seconds, P = .4). The length of time that cortical bone was exposed to critical temperatures (47°C or more) was significantly higher when a wire was reused (36 ± 72 seconds vs 43 ± 82 seconds, P = .008). Peak temperatures greater than 70°C (a temperature associated with instantaneous cell death) were observed on many occasions. Conclusions Overall heat exposure may be higher if a K-wire is reused or inserted in oscillating mode. In the absence of external cooling, K-wire insertion into cortical bone can easily expose bone to temperatures that exceed 70°C and may increase the risk of osteonecrosis.

This research article addresses the physical characteristics of the Carreau fluid flow through a horizontal microchannel subjected to Newton boundary conditions, Hall current, and heat generation. ...