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The rapid and orderly heat transfer of asphalt pavement has emerged as a crucial focus in solving the high temperature problem of pavement. At present, it is not comprehensive and accurate to characterize the heat transfer capacity of asphalt pavement only by thermal conductivity. In order to further investigate the heat transfer characteristic, the entransy was selected to characterize the heat transfer capacity of asphalt pavement. The heat transfer model was constructed using COMSOL. The temperature and heat flux were analyzed by entransy dissipation, and the heat transfer characteristics of asphalt pavement was determined. The results show that the entransy dissipation in the heat transfer process mainly occurs in the surface layer, where the entransy dissipation was 4.11 times that of the base layer, resulting in the heat accumulation and an increase in the surface temperature. There is still a big difference of entransy dissipation under the same thermal conductivity of surface layer. The entransy dissipation of the upper surface layer was 2.61 times that of the lower surface layer at 11:00. In addition, the thermal conductivity has a greater influence on the entransy dissipation than the heat capacity and density. The increase of thermal conductivity can reduce the entransy dissipation, thereby improving the heat transfer capacity of the pavement. When the thermal conductivity of the upper surface layer increased from 1 to 3 W m −1  K −1 ), the entransy dissipation decreased by 37.94%. What is more, the larger gradient distribution of the thermal conductivity between different surface layer in asphalt pavement would increase the entransy dissipation.

With the continuous increase in the thermal power of electronic devices, air cooling is becoming increasingly challenging in terms of meeting heat dissipation requirements. Liquid cooling media have a higher specific heat capacity and better heat dissipation effect, making it a more efficient cooling method. In order to improve the heat dissipation effect of liquid cooling, a TPMS structure with a larger specific surface area, which implicit function parameters can control, can be arranged in a shape manner and it is easy to expand the structural design. It has excellent potential for application in the field of heat dissipation. At present, research is still in its initial stage and lacks comparative studies on liquid cooled convective heat transfer of TPMS structures G (Gyroid), D (Diamond), and P (Primitive). This paper investigates the heat transfer performance and pressure drop characteristics of a sheet-like microstructure composed of classic TPMS structures, G (Gyroid), D (Diamond), and P (Primitive), with a single crystal cell length of 2π (mm), a cell number of 1 × 1 × 5, and a microstructure size of 2π (mm) × 2π (mm) × 22π (mm) using a constant temperature surface model. By analyzing the outlet temperature tout, structural pressure p, average convective heat transfer coefficient h0, Nusselt number Nu, and average wall friction factor f of the microstructure within the speed range of 0.01–0.11 m/s and constant temperature surface temperature is 100 °C, the heat transfer capacity D > G > P and pressure drop D > G > P were obtained (the difference in pressure drop between G and P is very small, less than 20 Pa, which can be considered consistent). When flow velocity is 0.01 m/s, the maximum temperature difference at the outlet of the four structures reached 17.14 °C, and the maximum difference in wall friction factor f reached 103.264, with a relative change of 646%. When flow velocity is 0.11 m/s, the maximum pressure difference among the four structures reached 8461.84 Pa, and the maximum difference in h0 reached 7513 W/(m2·K), with a relative change of 63.36%; the maximum difference between Nu reached 76.32, with a relative change of 62.09%. This paper explains the reasons for the above conclusions by analyzing the proportion of solid area on the constant temperature surface of the structure, the porosity of the structure, and the characteristics of streamlines in the microstructure.

Steam reforming is an effective method for improving heat sinks of hypersonic aircraft at high flight Mach numbers. However, unlike the industrial process of producing hydrogen with a high water content, the catalytic steam reforming mechanism for the regeneration cooling process of hydrocarbon fuels with a water content below 30% is still unclear. Catalytic steam reforming (CSR) and catalytic thermal cracking (CTC) reactions occur at low temperatures, with the main products being hydrogen and carbon oxides. Thermal cracking (TC) reactions occur at high temperatures, with the main products being alkanes and alkenes. The above reaction exists simultaneously in the regeneration cooling channel, which is referred to as partial catalytic steam reforming (PCSR). Based on the experimental measurement results, an improved neural network correction method was used to establish a four-step global reaction model for the PCSR of n-decane under low water conditions. The reliability of the four-step model was verified by combining the model with a numerical simulation program and comparing it with the experimental results obtained by electric heating hydrocarbon fuels with a pressure of 3 MPa and a water content of 5/10/15%. The experimental and predicted results using the developed kinetic model are consistent with an error of less than 5% in the decane conversion rate. The average absolute error between the fuel outlet temperature and total heat sink is less than 10%. Using the PCSR model to predict the heat transfer characteristics of mixed fuels with different water contents, the convective heat transfer coefficient is basically the same, and the Nu number is affected by the thermal conductivity coefficient, showing different patterns with changes in the water content.

Electrical heating ice removal pavement represents a promising technology for pavement ice melting. Existing studies primarily focus on optimizing cable-heated asphalt pavement through indoor model tests or finite element results. To obtain more accurate and reasonable temperature rise processes and heat transfer results, we propose a new evaluation metric for heat transfer capability and optimization in electric heating asphalt pavement. Firstly, a three-dimensional heat transfer model considering environmental heat exchange is established, and the accuracy of the model is verified by outdoor measured data. A dual-variable control experiment was carried out between the cable buried depth and insulation layer configuration to specifically analyze their influence on the temperature field of the asphalt layer. We further investigated heat transfer performance metrics (entransy dissipation and entransy dissipation thermal resistance), with results indicating that shallower cable burial depths reduce environmental interference on pavement heat transfer; the thermal insulation layer most significantly enhances pavement surface temperature (35.66% improvement) when cables are embedded in the lower asphalt layer. Placing cables within corresponding pavement layers according to burial depth reduces heat transfer loss capacity and thermal resistance, and positioning cables in the lower asphalt layer with a thermal insulation layer significantly decreases thermal resistance in both concrete and lower asphalt layers while reducing heat transfer capacity loss, demonstrating that installing thermal insulation layers under this structure improves heat transfer efficiency. The combined experimental and simulation verification method and fire dissipation evaluation system proposed in this study provide a new theoretical tool and design criterion for the optimization of electric heating road systems.

He–Xe, with a 40 g/mol molar mass, is considered one of the most promising working media in a space-confined Brayton cycle. The thermodynamic performance of He–Xe in different configuration channels is investigated in this paper to provide a basis for the optimal design of printed circuit board plate heat exchanger (PCHE). In this paper, the factors affecting the temperature distribution of the He–Xe flow field are analyzed based on the flow heat transfer mechanism. It is found that the flow patterns in the logarithmic and outer zones determine the temperature distribution pattern of the flow field. A series of numerical simulations verify the above conclusions, and it is found that reasonable channel structure and operating conditions can significantly improve the thermodynamic performance of the He–Xe flow. Based on the above findings, the Zig channel is optimized, obtaining Sine and Serpentine channels with different structural characteristics. Comprehensive thermodynamic comparisons of the helium–xenon flow domains inside channels are performed, and the Serpentine channel with a shape factor of tan 52.5° is found with the best performance. This work aims to improve the understanding of the thermodynamic performance of He–Xe in microchannels and provide theoretical support for further optimization of PCHE employing He–Xe.

The use of electrically driven drivetrains is increasing for passenger cars and light-, medium-, and heavy-duty trucks. Off-the-shelf automatic transmission fluids (ATFs) are still being used as electric drivetrain fluids (EDFs). EDFs are trending toward lower viscosity for better energy efficiency and better heat transfer capacity, while satisfying all the other challenging requirements, such as gear/bearing scuffing/wear protection, oxidative stability, copper corrosion, and coating/seal material compatibility. In this paper, we will highlight the importance of low foaming, low aeration, and low traction coefficient which are critical for the performance of the EDF during high-speed applications, measured using metrics such as energy efficiency, heat transfer capacity, and longer oil drain interval.

Accurate temperature prediction is vital for the canned permanent magnet synchronous motor (CPMSM) used in the vacuum pump, as it experiences severe heating. In this paper, a novel motor temperature calculation method is proposed, which takes into account the temperature impact on the heat transfer capacity. In contrast to existing electromagnetic-thermal coupled calculation methods, which solely address the temperature effect on the motor electromagnetic field, the proposed method comprehensively considers its impact on motor losses, permanent magnet magnetic properties, thermal conductivity, and heat dissipation ability of motor components, resulting in a motor temperature simulation that closely resembles the actual physical process. To verify the reliability of the proposed temperature calculation method, a 1.5 kW CPMSM was chosen as the research subject. The method was used to analyze the temperature distribution characteristics of the motor and assess the impact of ambient temperature on motor temperature rise. Furthermore, a prototype was fabricated, and an experimental platform was established to test the motor temperature. The results demonstrate good agreement between the calculated results obtained using the proposed method and the experimental data. This research not only provides a theoretical foundation for optimizing the design of the CPMSM but also provides valuable insights into its operational safety and reliability.

As an efficient heat conducting unit, micro heat pipe is widely used in high heat flux microelectronic chips, and thermal resistance is one of the factors that are crucial to its heat transfer capacity. Based on heat transfer theory, this paper established a theoretical model of total thermal resistance through analyzing the structure and heat transfer performance of circular heat pipe with trapezium-grooved wick, simplified the model and tested the micro heat pipe for its total thermal resistance performance by setting up a testing platform. The testing results show that when the micro heat pipe is in the optimal heat transfer state, its total thermal resistance well coincides with that from the established theoretical model. As for a micro heat pipe with trapezium-grooved wick, its total thermal resistance first decreases, then increases with heat transfer capability increment, and reaches the minimum when it is in the optimal state of heat transfer performance. That too much working fluid accumulates in evaporation section and the vapor velocity is rather low is the main cause for the greater thermal resistance when the pipe is in low heat transfer quantity, yet the greater total thermal resistance when the pipe is in high heat transfer quantity is mainly caused by the working fluid drying up in condensation section. The total thermal resistance is related to many factors, such as the thermal conductivity of tube-shell material, wall thickness, wick thickness, the number of the grooves, the lengths of condensation and evaporation sections, the diameter of vapor cavity etc.. Therefore, the structure parameters of a micro heat pipe with trapezium-grooved wick should be rationally designed according to specific conditions to ensure its heat transfer capacity and total thermal resistance to meet the requirements and be in the optimal state.

A pilot-scale wastewater source heat pump was operated for 30 days to recover heat from waste bathwater and to warm up fresh bathwater. The results indicated that the fresh water successfully warmed up to the designated 45℃, 50℃, and 55℃ with the coefficients of performance of 2.3–3.5. Artificial neural networks including back propagation, radial basis function, and nonlinear autoregressive model with exogenous input were used to simulate this process. The root-mean-square error and coefficient of variation of the simulated results, using the experimental data taken on the first 18, 21, 24, and 27 days, respectively, as a package of training data, showed that taking the data measured on more days as the training data improved simulation accuracy. The nonlinear autoregressive model with exogenous input needed at least 24 days’ training data to achieve acceptable simulation results, the back propagation needed 27 days, while the radial basis function did not achieve acceptable results. Predictions based on the nonlinear autoregressive model with exogenous input modeling showed that the performance of the wastewater source heat pump system could gradually be stabilized within 42 days. Practical application: This study showed that the wastewater source heat pump can recover heat from waste bathwater to warm up fresh bathwater, and also demonstrated that the artificial neural network, especially nonlinear autoregressive model with exogenous input, is appropriate for predicting heat pump performance. Using this system can reduce building energy consumption, while using the artificial neural network model can help operate and maintain the wastewater source heat pump system.

In this paper, performance evaluation of miniature heat pipes in LTCC was made by numerical analysis, and the optimum miniature heat pipe design was defined. The effect of the groove depth, width and vapor space on the heat transfer capacity of miniature heat pipes was analyzed. Prototypes of the miniature heat pipes in LTCC were fabricated. Preliminary charging, sealing and thermal measurement of the miniature heat pipes were performed, and the challenges were discussed.