Minimum Temperature Difference Research Articles

Dung Beetle Optimized Fuzzy PID Algorithm Applied in Four-Bar Target Temperature Control System

With the widespread application of infrared thermal imagers in various fields, the demand for thermal imagers and their performance parameter testing equipment has increased significantly. There are particularly high demands on the detection accuracy of minimum resolvable temperature difference (MRTD) testers. Traditional MRTD testers have an issue with the four-bar target temperatures being easily affected by the external environment, resulting in non-uniform temperatures and imprecise detection results. This paper proposes an improvement to the four-bar targets by making them temperature-controllable. Temperature is controlled by installing thermoelectric coolers (TECs) and thin-film platinum resistors at the center and periphery of the four-bar targets with different spatial frequencies. The dung beetle algorithm is used to optimize fuzzy PID parameters to regulate the TEC’s heating and cooling, improving the overall temperature uniformity of the four-bar targets. Temperature simulations of the four-bar targets were conducted on the COMSOL platform, with the control part simulated on the Simulink platform. The simulation results show that, compared to traditional PID, the fuzzy PID controller reduces overshoot by approximately 3.6%, although the system still exhibits mild oscillations. The fuzzy PID controller optimized by the dung beetle optimization (DBO) algorithm, in comparison to standard fuzzy PID, reduces the settling time by about 40 s and lowers overshoot by around 7%, with oscillations in the system nearly disappearing. Comparing the fuzzy PID optimized by the particle swarm optimization (PSO) algorithm with the fuzzy PID optimized by the DBO algorithm, the DBO-based controller shows shorter rise and settling times, further illustrating the superiority of the fuzzy PID control optimized by the dung beetle algorithm. This provides a theoretical foundation for improving the accuracy of MRTD detector measurements. Finally, experimental verification was carried out. The experimental results indicate that DBO (drosophila-based optimization) has significant advantages, and its optimized results are closer to the actual values.

La Nia and climate degree of contact

Studies have shown that the 2022 anomalous climate change is different from previous La Nia phenomena. Using the data of the maximum temperature, minimum temperature and temperature difference from 2020 to March 2021 in Hong Kong, the grey model was used to compare the maximum and minimum temperature values in 2022 with the actual values and found that the values were close. The La Nia phenomenon occurred in March 2022, concluding that La Nia is not a major contributor to climate change in Hong Kong. Climate change in Hong Kong is also linked to typhoons, increased carbon dioxide levels in the air, ocean temperatures and other factors. The study concluded that the main cause of the extreme weather in Hong Kong in 2022 was not the occurrence of La Nia, but a combination of factors such as cumulative carbon dioxide emissions, human activities, the altitude of the Tibetan Plateau, and typhoons.

Impacts of projected urban growth on simulated near-surface temperature in Mexico City Metropolitan Area: Implications for urban vulnerability

Urbanization impacts the surface temperature fields increasing the vulnerability of urban residents to heat exposure. Identifying vulnerable urban populations to extreme heat exposure is crucial to develop mitigation and adaptation strategies towards sustainability. We used an urban growth model (SLEUTH) to simulate emerging urban areas in Mexico City Metropolitan Area (MCMA) under a hypothetical land-use policy scenario projected to 2060 in which no restrictions were posed to urban growth. SLEUTH outputs were used in the numerical model Weather Research and Forecasting (WRF) to quantify expected changes in near-surface temperature within the MCMA. We calculated and mapped heat exposure as differences in average (Tmean), maximum (Tmax) and minimum (Tmin) temperatures over the diurnal cycle between future and current land cover conditions. Population vulnerability to projected increases in heat exposure was determined using a set of socioeconomic indicators. SLEUTH simulations showed an urban area expansion of nearly 4,790 km2 by 2060. Overall, changes in Tmin were greater than changes observed for Tmax and Tmean. Tmean, Tmax and Tmin increases up to 0.6°C, 1.3°C and 2.6°C, respectively, were recorded for the MCMA with greatest temperature changes observed in the State of Mexico. Results suggested the presence of socioeconomic disparities in the projected spatial exposure of urban-induced heat in MCMA. We argue that our results could be used to inform and guide locally tailored actions aimed at reducing exposure and increasing population´s capacities to cope and adapt to future threats.

Thermodynamic Analysis and Comparison of Power Cycles for Small Modular Reactors

Small nuclear power plants can provide a stable, carbon-free energy supply to civil infrastructure and industrial enterprises in remote regions isolated from unified energy systems. More than 70 projects of small modular reactors are currently being developed by IAEA member countries; several low-power power units are already supplying thermal and electrical energy to consumers. One of the main limitations standing in the way of widespread dissemination of this technology is the high specific capital cost of a low-power nuclear power plant; therefore, new scientific and technical solutions are needed in this industry. Increasing the thermodynamic efficiency of power cycles of small modular reactors can become a driver for reducing the cost of supplied electrical energy. This paper presents the results of a comprehensive thermodynamic analysis of existing and promising power cycles for small modular reactors. In addition to traditional steam power cycles, cycles using non-traditional working fluids, including carbon dioxide, freons, and helium cycles, are considered. Optimal sets of thermodynamic parameters were determined to ensure maximum net efficiency of electricity production. For water-cooled reactor plants, a maximum efficiency of 33.5% at an initial temperature of 300 °C could be achieved using a steam turbine cycle. It was revealed that for reactor plants with liquid metal and liquid salt coolant in the range of initial temperatures above 550–700 °C, the maximum thermal efficiency was provided by the Brayton recompression cycle with a carbon dioxide coolant: the net electrical efficiency exceeded the level of steam turbine plants, with intermediate superheating of the steam, and could reach a value of 49.4% at 600 °C. This makes the use of these cycles promising for low-power nuclear power plants with a high initial temperature. In small gas-cooled reactor plants with a helium coolant, the use of a binary cycle consisting of a helium Brayton cycle and a steam-powered Rankine cycle provided an efficiency of 44.3% at an initial helium temperature of 700 °C and 52.9% at 1000 °C. This was higher than in the Brayton cycle with a recuperator, with a minimum temperature difference in the heat exchanger of 20 °C: the efficiency was 40.2% and 52%, respectively. Also, the transition to power cycles with non-traditional working fluids will lead to a change in the operating conditions of turbomachines and heat exchangers.

In-situ synthesis and oxidation behaviors of Ti-xAl coatings by high-frequency induction heated combustion

Ti-xAl coatings (x=25, 33.3, 50, 66.7, and 75 at%) were fabricated in situ using high-frequency induction heating synthesis (HFIHCS). The process parameters for preparing Ti-Al coatings via HFIHCS were orthogonally optimized employing the finite element method. The effect of the aluminum content on the microstructures and phase compositions of Ti-Al coatings fabricated by HFIHCS, as well as their oxidation behaviors at 900℃ for 100 h was investigated. The results showed that the distribution of interfacial temperature difference was influenced by induced current (62.11%), relative density of compact (9.86%), and indenter material (28.03%). The minimum interfacial temperature difference was achieved with an induced current of 300 A, a graphite indenter material, and a compact density of 82.9%. The Ti-xAl coatings exhibited a core (Ti)-shell (TixAly) ring structure. The rise in aluminum content in the Ti-xAl coatings led to a gradual reduction in the titanium-rich phase, accompanied by a progressive increase in the aluminum-rich phase and the interface thickness of zones Ⅰ and Ⅱ. The porosities of Ti-xAl coatings containing over 50 at% aluminum exhibited an order of magnitude higher than those of Ti-xAl coatings with 50% aluminum or lower. The mechanisms of reaction, pore-forming, and interfacial diffusion for Ti-xAl coatings were predominantly controlled by dissolution-precipitation, thermal expansion of intrinsic pores within the cold-pressed compact and voids formed after molten aluminum flow, and liquid-solid co-diffusion, respectively. The increase in aluminum content in the Ti-xAl coatings led to in a gradual decrease in its oxidative weight gain, a shift in the oxidation kinetics from a linear-parabolic to a parabolic law, and an enhancement in preservation of internal core-shell characteristics and the likelihood of forming a protective layer of thin Al2O3. The oxidation behaviors of Ti-xAl coatings with a core-shell structure were co-controlled by the aluminum content and the porosity affected by the aluminum content.

Development of bio-based flexible phase change materials utilizing lauric acid for battery thermal management systems

Lithium-ion batteries, serving as the cornerstone of electric vehicles, generate significant thermal output during their operation. This underscores the imperative need for the implementation of an appropriate battery thermal management system (BTMS). Extensive attention has been directed towards thermal-induced flexible phase change material (FPCM) within the domain of BTMS. However, it is notable that the predominant choice in contemporary practice for FPCM in BTMS remains paraffin (PA)-based, sourced from petroleum origins. This study utilizes an environmentally friendly bio-based phase change material (PCM), lauric acid (LA), to fabricate FPCM. The FPCM is skillfully crafted through the incorporation of styrene-ethylene-propylene-styrene (SEPS) and expanded graphite (EG) as supporting materials, forming the LA/SEPS/EG composite phase change material (CPCM). The addition of EG increases the thermal conductivity of CPCM by 4.97 times and enhances the leakage resistance. Furthermore, comprehensive assessments were conducted to evaluate the thermal performance, thermally induced flexibility, heat storage, release characteristics, and cyclic stability of the fabricated FPCM. In the battery discharge tests conducted at 2C/3C/4C rates, the battery containing FPCM consistently maintained its maximum temperature below 50 °C, with a minimal temperature difference of <1 °C, showcasing excellent thermal management performance.

Cryogenic insulation performance of polyimide foam-filled fluted-core composite sandwich panels

Foam-filled composite sandwich structures have demonstrated superior thermal insulation performance, making them highly suitable for cryogenic tanks in launch vehicles. This study focused on the cryogenic insulation characteristics of carbon fiber-reinforced plastic (CFRP) fluted-core sandwich panels filled with polyimide foam. The fluted-core sandwich panel was simplified into a homogeneous multilayer plate to establish a one-dimensional heat transfer theoretical model. This model was used to predict steady-state temperature approximate solutions by linearizing the temperature-dependent thermal conductivity. The sandwich specimens were fabricated using an integrated forming co-cured method. Self-developed cryogenic insulation experiment and finite element simulations were conducted to acquire temperature distributions and validated the precision of the theoretical model. Results showed that the specimens achieved insulation temperature difference exceeding 143.05 °C, with effective thermal conductivity reaching 0.0326 W/(m·°C), significantly lower than that of CFRP. The temperature distributions along the thickness direction displayed a nonlinear increasing trend. The cryogenic thermal short effect was noticeable at the junction of the bottom facesheet and web. An analysis of geometric parameter influences revealed that increasing the short span, core height, or reducing web thickness could enhance thermal insulation characteristics with minimum effective thermal conductivity of 0.0276 W/(m·°C) and lead to a more uniform distribution of bottom temperatures with minimum temperature difference of 3.30 °C. These findings provide a foundational analysis for designing cryogenic insulation structures.

Temperature prediction and scheduling of data center based on segmented neural network

Task scheduling based on temperature perception is beneficial for avoiding hotspots and optimizing the internal temperature distribution of data centers. However, the accuracy of task scheduling largely depends on the accuracy of temperature prediction. There are many features that affect the accuracy of temperature prediction in data centers, and the variation periods of these features vary greatly. Traditional machine learning models are difficult to accurately fit them. Therefore, this article proposes a step-by-step temperature prediction algorithm based on Gated Recurrent Unit (GRU). This algorithm establishes prediction models for important parameters such as CPU utilization and air conditioning temperature that affect temperature prediction, and uses the outputs of these two models as inputs for the server temperature prediction model to better fit the changes of feature values. The model combines the principle of thermal locality and integrates the temperature of upper and lower servers for joint modeling. Experiments show that our prediction model can accurately predict the inlet temperature evolution of the server with dynamic workload. RSME reaches 0.278 and the average prediction temperature difference is 0.633, which is much higher than the traditional model. In addition, this article also propose a minimum temperature difference scheduling algorithm based on temperature prediction model, which can effectively reduce the number of servers running at high temperature and low temperature in the data center, make the temperature of the data center more balanced and achieve better energy-saving compared with other baseline algorithms.

Prediction of Onset Temperature in Standing Wave Thermoacoustic Engine with Mesh Screen Stack

A thermoacoustic engine is a engine that converts thermal energy into acoustic energy, which can be used to generate electricity or cooling. This engine is attractive because it consists only of a stack, heat exchangers, and a resonator. The stack serves as the primary component for the energy conversion process and consists of porous materials like an array of stainless steel mesh screens. To generate the acoustic energy, a minimum temperature difference is necessary between the two sides of the stack, called the onset temperature difference. However, the calculation for prediction of onset temperature on the stack made of mesh screen has not been addressed. Therefore, the objective of this paper is to propose a method that can be used to estimate the onset temperature difference in standing wave thermoacoustic engine with stacks made of mesh screen arrays. The onset temperature difference is predicted numerically using linear stability theory and matrix transfer methods. Experimental verification is carried out by using standing wave thermoacoustic engine from pervious study. The results showed that the lowest onset temperature difference (TH - TC = 140ºC) is obtained when rh = 0.497 mm. Furthermore, the numerical and experimental onset temperature difference comparisons show a qualitative agreement, allowing the onset temperature prediction method to be used in designing standing wave thermoacoustic engines with stacks made of mesh screens.

Variability and drivers of winter near-surface temperatures over boreal and tundra landscapes

Abstract. Winter near-surface air temperatures have important implications for ecosystem functioning such as vegetation dynamics and carbon cycling. In cold environments, the persistence of seasonal snow cover can exert a strong control on the near-surface temperatures. However, the lack of in situ measurements of both snow cover duration and surface temperatures over high latitudes has made it difficult to estimate the spatio-temporal variability in this relationship. Here, we quantified the fine-scale variability in winter near-surface air temperatures (+2 cm) and snow cover duration (calculated from temperature time series) using a total of 441 microclimate loggers in seven study areas across boreal and tundra landscapes in Finland during 2019–2021. We further examined the drivers behind this variation using a structural equation model and the extent to which near-surface air temperatures are buffered from free-air temperatures during winter. Our results show that while average winter near-surface temperatures stay close to 0 ∘C across the study domain, there are large differences in their fine-scale variability among the study areas. Areas with large topographical variation, as well as areas with shallow snowpacks, showed the greatest variation in near-surface temperatures and in snow cover duration. In the tundra, for example, differences in minimum near-surface temperatures between study sites were close to 30 ∘C and topography was shown to be an important driver of this variability. In contrast, flat topography and long snow cover duration led to little spatial variation, as well as long periods of decoupling between near-surface and air temperatures. Quantifying and understanding the landscape-wide variation in winter microclimates improves our ability to predict the local effects of climate change in the rapidly warming boreal and tundra regions.

Optimization and experimental validation of the air intake holes of the lithium-ion battery pack

Energy storage systems enable the storage of energy and provide access to carbon-neutral, environmentally friendly energy whenever or wherever it is needed. Lithium-ion batteries are currently the most preferred type among various battery technologies and are widely used in energy storage systems. Some of the features that make lithium-ion batteries advantageous include high energy density, long life, low maintenance requirements, and high operating voltage. The growing demand for energy throughout the day increases the need for batteries with high storage capacity. However, the increased capacity also leads to heating issues in lithium-ion batteries. The heating problem in lithium-ion batteries can result in nonhomogeneous temperature distribution, shortened lifespan, thermal runaway, increased internal resistance, and performance loss. Therefore, an effective thermal management system is essential for cooling lithium-ion batteries. This study aims to provide insight into the forced air cooling of prismatic 280 Ah LiFePo4 batteries, which have limited information in the literature and are more prone to overheating compared to lower-capacity batteries. In this study, five different battery pack case designs, each with different sizes and numbers of air intake holes, were determined and modelled using the SolidWorks program. Within the battery pack cases, 16 280 Ah lithium-ion batteries are placed, and an axial fan is used to cool these batteries. Initially, computational fluid dynamics analyses of the five different designs were performed in the SolidWorks Flow Simulation program. An experiment was then conducted on the design that provided the most efficient thermal management to validate the numerical results. The selected design, fulfilling the purpose of homogeneous temperature distribution and having the minimum temperature difference between batteries, was designated as Design 5. It exhibited a 62 % improvement in cooling performance with a 0.25 °C temperature difference, indicating successful temperature homogeneity between batteries. During a two-hour experiment with a 140 A discharge current, temperature measurements were taken from the surfaces of the batteries using thermocouples. Finally, the maximum error rate between experimental and numerical studies was determined to be 1.47 %, indicating successful validation of the numerical study. The air intake hole optimization, a novel design approach, prevents temperature distribution inhomogeneity caused by the distance of the batteries to the fan and offers an effective way to cool down high-capacity 280 Ah batteries.

A novel topology optimization of fin structure in shell-tube phase change accumulator considering the double objective functions and natural convection

Shell-tube phase change accumulator (STPCA) has been widely applied in renewable energy generation and energy-saving building field. However, due to the low thermal conductivity of phase change material (PCM), its structure needs to be carefully designed to obtain the best heat release and storage rate. Most of the traditional design schemes are trial and error method, which has long design cycle, low efficiency, and difficulty in obtaining the optimal structure. In this contribution, we firstly adopt the topology optimization methods to obtain novel fins in STPCA considering natural convection. Then, we compared the difference between different objective functions and demonstrated the superiority of topology optimization. In addition, we have further studied fin design under double objective functions with different weight ratios and analyzed the synergistic effects on the objective functions. The results have shown that after natural convection has been considered in the topological optimization process, it can help obtain a better structure, and the generated fins can better enhance the performance of STPCA. For the case of single objective function, the conclusions are as follows: the maximum average temperature can be used to obtain the faster melting speed, while the minimum temperature difference can be used to obtain the best temperature uniformity. The conclusions of using double objective function are as follows: when the weight ratio of the maximum average temperature and the minimum temperature difference is 0.6: 0.4, the field synergy angle is smallest, and the performance of STPCA is further improved. This contribution can provide a guidance for STPCA design and enhance its thermal storage performance.

Thermal performance of ultra-thin vapor chamber with etched micro-structure for electronics cooling

As a two-phase heat transfer element, vapor chambers (VCs) have received widespread attention in recent years due to the advantages of high-effective thermal conductivity, lightweight, and flexibility in design and application. With the development of microelectronic products towards higher levels of integration and compactness, there is also a growing demand for thinner VCs. In this paper, the heat transfer performance of novel ultra-thin vapor chambers (UTVCs) with a thickness of only 0.3 mm was designed and tested. The composite wick is made of an etched micro-structure and 300 in−1 copper mesh. The heat transfer performance of UTVCs such as the temperature distribution, the temperature difference and the thermal resistance was investigated under different heating power by evaluating the effect of etched micro-structures, liquid charging ratio and test direction. The results of the experiment showed that the optimal liquid charging ratio for continuous micro-structure and non-continuous micro-structure is 60 % and 80 %, respectively, and the minimum temperature difference is 1.3 °C and 3.5 °C for the heating power of 5.5 W, respectively. In addition, the continuous micro-structure UTVC with a liquid charging ratio of 60 % has better heat transfer performance and the maximum temperature difference is less than 5 °C in all test directions of horizontal direction, gravity direction and anti-gravity direction.

Investigation of an improved cold plate design with circuitous minichannel: a computational study involving the effect of conjugate heat transfer

Purpose This study aims to investigate a new circuitous minichannel cold plate (MCP) design involving flow fragmentation. The overall thermal performance and the temperature uniformity analysis are performed and compared with the traditional serpentine design. The substrate thickness and its thermal conductivity are varied to analyse the effect of axial-back conduction due to the conjugate nature of heat transfer. Design/methodology/approach The traditional serpentine minichannel is modified into five new fragmented designs with two inlets and two outlets. A three-dimensional numerical model involving the effect of conjugate heat transfer with a single-phase laminar fluid flow subjected to constant heat flux is solved using a finite volume-based computational fluid dynamics solver. Findings The minimum and maximum temperature differences are observed for the two branch fragmented flow designs. The two-branch and middle channel fragmented design shows better temperature uniformity over other designs while the three-branch fragmented designs exhibited better hydrodynamic performance. Practical implications MCPs could be used as an indirect liquid cooling method for battery thermal management of pouch and prismatic cells. Coupling the modified cold plates with a battery module and investigating the effect of different battery parameters and environmental effects in a transient state are the prospects for further research. Originality/value The study involves several aspects of evaluation for a conclusive decision on optimum channel design by analysing the performance plot between the temperature uniformity index, average base temperature and overall thermal performance. The new fragmented channels are designed in a way to facilitate the fluid towards the outlet in the minimum possible path thereby reducing the pressure drop, also maximizing the heat transfer and temperature uniformity from the substrate due to two inlets and a reversed-flow pattern. Simplified minichannel designs are proposed in this study for practical deployment and ease of manufacturability.

STREAMS HEAT INTEGRATION IN THE SEPARATION PROCESS OF THE FURFURAL-WATER HETEROAZEOTROPIC MIXTURE BY USING TWO STRETCHING COLUMNS

The process of azeotropic mixtures rectification takes place in many branches of the chemical industry. This process requires significant energy consumption both for heating and evaporation of process streams, and for vapor condensation and cooling of products. The consumption of external energy essentially depends on the methods of separation processes organization. Pinch analysis is one of the modern methods for designing chemical-technological systems with the aim of optimal use of external energy sources by maximizing the heat integration of system process streams, taking into account the limitations of a particular manufacture, the requirements of environmental safety and environmental protection. In this paper the heat integration of the heteroazeotropic furfural-water mixture separation process by two columns was considered. In each column the azeoptrope is a light-boiling one, and one of the mixture components is a low-boiling one. The heat and material balances of the rectifying plant were calculated and the table of its streams was formed, that is, the data of the chemical-technological system were extracted. From the total set of heat streams, the subset was selected for heat integration. Composite curves for the selected heat streams subject to heat integration were built and their relative position on the temperature-enthalpy diagram was analyzed. This analysis showed that for a certain value of the minimum temperature difference in the heat exchange equipment Тmin, there is a threshold problem. The problem was formulated for a value of Тmin slightly less than the threshold value that led to a slight increase in the consumption of external energy carriers. Options for further improvement of the network of heat exchangers were considered, and the occurrence of a cycle through the pseudopinch was identified. It gave possibility to remove a heat exchanger with a low load and redistribute this load among to other ones. Restoring Тmin in this case is impossible, because a strict restriction on the absence of hot utilities is accepted. Significant savings in external utilities load have been demonstrated. For retrofit modern Alfa Laval heat exchange equipment was selected for all the necessary positions.

Using multilayer structures to enhance the electrical properties of porous silicon for thermal sensing

Porous silicon holds great promise as an optically and electrically tuneable material platform for high performance thermo-resistive sensing. Fulfilling this promise requires the ability to independently control the two critical parameters which determine the sensitivity (specifically the minimum temperature difference resolution) of thermal detectors: the temperature coefficient of resistance (TCR) and 1/f noise of the sensing material. In single porosity films these two properties are monolithically dependent, with both TCR and 1/f noise constant increasing with porosity. Here we show that use of multilayer films allows manipulation of properties of the overall structure to simultaneously achieve high TCR and low 1/f noise. Characterization of electrical properties of various porosity combinations revealed that using a two-layer heterostructure on Si substrate with low porosity (48 %) as the top layer and a high porosity (80 %) as the lower layer, both high TCR (∼ 4.4 %/K) and low 1/f noise constant (4 × 10−13) could be simultaneously achieved. This transforms the ability to exploit porous silicon for future high sensitivity based thermal detectors.

Effect of operating conditions of unmanned aerial vehicle powered by PEMFC on water and heat distributions of cell

ABSTRACT The cell performance of a proton exchange membrane fuel cell (PEMFC)-driven unmanned aerial vehicles (UAV) is affected by environmental changes during high-altitude flights. Therefore, the distribution of water and heat in a PEMFC was investigated. The result showed that the uniformity of temperature distribution on the membrane could be improved by increasing the air stoichiometry ratio, but the temperature difference on the membrane was still large and the minimum temperature difference was 14.6°C. When the temperature distribution is uniform, the temperature on the membrane is too low. Consequently, increasing the inlet temperature to 60°C, 70°C and 80°C resulted in inlet and outlet temperature differences of 3.5°C, 0.5°C and 2.7°C for the membrane respectively. By analyzing the distribution of the water content and temperature on the membranes, 70°C and 20 were considered to be the optimal inlet temperature and air stoichiometry, respectively. Under this condition, as the altitude increases, the temperature and water content on the membrane gradually decrease.

Advanced Exergy-Based Analysis of an Organic Rankine Cycle (ORC) for Waste Heat Recovery.

In this study, advanced exergy and exergoeconomic analysis are applied to an Organic Rankine Cycle (ORC) for waste heat recovery to identify the potential for thermodynamic and economic improvement of the system (splitting the decision variables into avoidable/unavoidable parts) and the interdependencies between the components (endogenous and exogenous parts). For the first time, the advanced analysis has been applied under different conditions: constant heat rate supplied to the ORC or constant power generated by the ORC. The system simulation was performed in Matlab. The results show that the interactions among components of the ORC system are not strong; therefore, the approach of component-by-component optimization can be applied. The evaporator and condenser are important components to be improved from both thermodynamic and cost perspectives. The advanced exergoeconomic (graphical) optimization of these components indicates that the minimum temperature difference in the evaporator should be increased while the minimum temperature difference in the condenser should be decreased. The optimization results show that the exergetic efficiency of the ORC system can be improved from 27.1% to 27.7%, while the cost of generated electricity decreased from 18.14 USD/GJ to 18.09 USD/GJ.

Investigation of the thermal management potential of phase change material for lithium-ion battery

With the rapid development of electric vehicles, lithium-ion battery has been widely used as an energy source. However, to avoid thermal runaway and to ensure the correct operation of lithium-ion battery system, effective battery thermal management would be required. In this study the capacity of phase change materials with different thermal-physical properties to respectively manage thermal issues associated with lithium-ion battery is theoretically investigated using computational fluid dynamics. The impacts of shell material, heat transfer coefficient, phase change material fill volume and the shape of the battery pack on the thermal performance of the lithium-ion battery/phase change material system are investigated in detail. The results show that when the ambient temperature was 20 °C or 30 °C, phase change material-RT35 shows the best temperature control ability for the proposed system, while the phase change material-RT50 has better thermal management capability when the ambient temperature is 40 °C. Also, higher heat transfer coefficient or shell material with higher thermal conductivity, effectively reduce the maximum temperature of the lithium-ion battery and the temperature difference within the proposed system. Specifically, the phase transition time in the lithium-ion battery/phase change material system with a heat transfer coefficient of 10 W/m2K is more than twice longer compared to that of 1 W/m2K and the maximum temperature is 47.18 °C after 150 min of charging and discharging. It is also observed that the phase change material with larger volume ratio leads to lower system temperature during phase transition and the continuous charging and discharging after completing transformation of the phase change material impacts negatively on the thermal management of the lithium-ion battery system. Besides, the rectangular lithium-ion battery/phase change material system surpasses the circular one by 14.78 °C in maximum temperature, while attaining a minimum temperature difference of 9.6 °C after 150 min of charging and discharging.

Flexible thermoelectric generator and energy management electronics powered by body heat

Uninterrupted, efficient power supplies have posed a significant hurdle to the ubiquitous adoption of wearable devices, despite their potential for revolutionizing human‒machine interactions. This challenge is further compounded by the requirement of these devices to supply dependable energy for data-intensive sensing and transmission. Traditional thermoelectric solutions fail to deliver satisfactory performance under conditions of extremely low voltages. Here, we present a novel solution of a wearable thermoelectric generator integrated with an energy management system, which is capable of powering sensors and Bluetooth by harnessing body heat. Distinct from previous works, our innovation lies in its ability to consistently operate even with a minimal temperature difference (i.e., 4 K) between the human skin and the ambient environment, ensuring reliable data transmission within a time as short as 1.6 s. Furthermore, our system can recharge utilizing body heat under ultralow voltage conditions (30 mV). Our developed system provides a novel pathway for the continuous, reliable monitoring of self-contained wearable devices without depending on batteries.