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Abstract Thermal stress in IGBT power module can lead to sever thermal reliability problems such as module deformation, performance degradation and even permanent damage. So, it is important to develop innovative and efficient IGBT cooling technologies. In this paper, a novel thermal management system is developed for cooling IGBT power module. The module is integrated with a vapour chamber-based heat sink to reduce thermal resistance and improve temperature uniformity significantly. 3D FEM modelling is conducted to investigate the effect of vapour chamber on temperature distribution, thermal stress, energy strain dissipation density and lifetime under power cycle. The simulation results show that the proposed thermal management system is superior to traditional cooling solution regarding cooling capacity, thermal stress, creep and plastic strain energy dissipation and thermal fatigue life. The study of failure mechanism of solder layer under power cycling suggests that creep causes the main is damage in the power cycling and cracks induced by thermal loading can be expected to initiate at the edge.

Abstract In this work, a novel wickless heat pipe fabricated using the roll-bond process and called the roll-bond flat thermosyphon was proposed for electronic component cooling due to its slim and large-size configuration, low-cost, and mass-production capable. The thermal performance of roll-bond flat thermosyphon was investigated through the tests in terms of 3 typical structures (stagger, cross and align) and 4 filling ratios (5%, 10%, 20%, and 40%) under the increasing heat power, and evaluated with the effective thermal conductivity and the maximum heat transfer capacity. The phenomena of boiling regime evolution, geyser effect, liquid entrainment and dry-out, can be found through the temperature responses in the cases of progressive filling ratios and heating powers. The cross-structured sample was found to behave the worst among the three structures due to its blocked up-flowing inflated circuits. The highest effectivity thermal conductivity of 22404 (W/K·m) was found in the 5%-align sample, however, accompanied with early dry-out. The heat transfer capability is positive correlated to the filling ratio, and maximum heat transfer capacity of 100 W (heat flux of 14.9 (kW/m2)) was recorded in the stagger-40% sample. The 20%-stagger sample is recommended as the optimum design, due to its more stable and relative high thermal conductivity, which is peaked to 16019 (W/K·m), and averaged at 12616 (W/K·m) in the range of 0–90 W.

The crossover of nitrogen and oxygen from cathode to anode aggravates the non-uniformity inside dead-end anode proton exchange membrane fuel cell (DEA-PEMFC), inducing some other effects, such as carbon corrosion, to cause irreversible damage to catalyst. Therefore, developing a purge strategy according to the non-uniformity is necessary to improve its stability. In this study, the effects of operating parameters on the uneven electrical-thermal-water performance are investigated based on a three-dimensional transient model of DEA-PEMFC. Afterwards, a purge optimization is carried out based on the uneven distribution of field variables. The results show that the calculated standard deviation (STDEV) of overvoltage is reduced first and then increased quickly for all the cases. Therefore, the purge should be started when the STDEV approaches the minimum value, to avoid the irreversible damage to DEA-PEMFC, achieving high-stability output performance meanwhile. On this basis, the purge interval is optimized to 100 s, which is suitable for almost all the discussed cases. The purge duration is reduced to 0.2 s. In this situation, the minimum voltage is decreased by about 0.95% compared with the maximum value, indicating a good voltage stability. This study is beneficial to provide guidance for the efficient and long-term operation of DEA-PEMFC.

Abstract The performance of thermoelectric generation (TEG) systems is significantly dependent on the hot side temperature of thermoelectric legs and the temperature difference between the hot side and cold side of the legs. To keep the TEG module working at an optimal condition, a high heat flux over 10 W/cm2 through the TEG needs to be maintained. Due to the low heat transfer coefficient of the gas flow to the exhaust pipe wall surface, typically at a high temperature ranging from 400 °C to 800 °C, the actual heat flux into the TEG heat exchanger is limited significantly, resulting in relatively low efficiency of the TEG conversion. In the present study, an effective solution for enhancing the heat transfer of gas flow in the radial direction to the TEG is proposed by means of immersing high temperature heat pipes perpendicularly into the exhaust flow. Similarly, conventional heat pipes are radially inserted into a concentric coolant jacket in order to enhance heat transfer performance at the cold side of TEG modules. Overall, the TEG assembly is configured as a compact and scalable heat pipe heat exchanger. The simulation results show that the hot side temperature of the TEG can reach and be maintained as high as 300 °C while the cold side temperature of the TEG can be maintained at approximately 85 °C for a normal engine coolant loop. The results also show that the closer to the heat source in the pipeline the TEG system is located, the better the power generation that is expected. Moreover, better thermoelectric generation can be expected at a higher engine speed. By installing the TEG heat exchanger between catalytic converter and muffler, the best power output in the thermoelectric heat exchanger can be achieved at 450 W and 5000 rpm. If the TEG heat exchanger is adjacent to the outlet of a catalytic converter, the best-simulated performance at 6000 rpm is 705 W for a single sub pipeline. Therefore, a total power generation of 1410 W is achievable since the existing exhaust pipe is a dual pipeline system.

This study proposes three composite wick structures (copper power or mesh sintered on grooved tube), namely, single arch-shaped sintered–grooved wick (SSGW), bilateral arch-shaped sintered–grooved wick (BSGW), and mesh–grooved wick (MGW), to improve the thermal performance of ultra-thin heat pipes (UTHPs). Phase-change flattening technology is employed to fabricate UTHPs. The morphologies of the wick structures after flattening are observed. An experimental apparatus is setup to investigate the thermal performance of UTHP samples under incremental heat loads. The heat transfer limits of UTHP are theoretically and experimentally analyzed. Capillary limit is found to be the main heat transfer limit, and the theoretical values of the samples with SSGW and BSGW are in good agreement with the experimental results. Results indicate that the maximum heat transport capacities are 12 W, 13 W and 14 W, under the corresponding optimum filling ratios of 70%, 70%, and 80%, for the SSGW, BSGW and MGW UTHPs, respectively. Evaporation and condensation thermal resistances of UTHP samples increase with the increase in the filling ratio before the occurrence of dry-out. UTHPs with SSGW have the least evaporation thermal resistance whereas UTHPs with MGW have the least condensation thermal resistance.

Ni particle coarsening is an important factor in deteriorating the durability of solid oxide fuel cell (SOFC) operations. In order to investigate the influence of Ni coarsening on SOFC performance, the transient multi-physical field model of SOFC was developed in this paper. The high operating temperature accelerates Ni particle growth and increases the attenuation rate of SOFC current density from 0.23%/kh at 650 °C to 2.6%/kh at 800 °C. The increase in the ratio of steam to carbon also intensifies the Ni particle coarsening process and deteriorates the transient performance of SOFC. Increasing YSZ particle diameter could hinder the growth of Ni particles and slowing down the increase rate of Ni particle diameter. Within the range of preset YSZ diameter dYSZ, increasing dYSZ reduces the attenuation rate and increases the average current density. Improving Ni phase fraction helps to reduce the attenuation rate of current density. Since multi-physical field (MPF) simulation needs long calculation time and it is difficult to achieve fast prediction, artificial neural network (ANN) is trained by the database generated by MPF. The mapping relationship between operating parameters, structural parameters and attenuation indexes is obtained. Finally, the attenuation performance of SOFC is optimized by genetic algorithm (GA) through data-driven method. The absolute average relative errors of all parameters in predicting attenuation rate and average current density are as low as 0.767% and 0.248%, which indicates the reliability of the ANN prediction. After optimization, the maximum current density is 5848 A·m−2 under operating voltage at 0.6 V when the attenuation rate requirement not exceeding 1% is satisfied. The combination of MPF simulation, ANN and GA provides a framework for fast performance prediction and optimization of strong nonlinear system.

This paper proposes new quantitative research methods with computational fluid dynamics (CFD) tools for a sustainable urban design project. This research study is sponsored by Research Councils UK (RCUK) China office. This project is part of the Caofeidian International Eco-town development in North-Eastern China. The research programme addresses the main aspects of good practice in terms of eco-design and sustainability. These aspects include wind flow analysis around buildings, pollutant dispersion in water systems and noise control on urban highways. This programme aims to explore a range of research methods in order to enhance the performance of integrated design with a comprehensive planning stage. The pros and cons, alongside other deficiencies in current forms of comprehensive plan are to be explored further. This project evaluates the Chinese Planning System and introduces new ways of achieving sustainable urban design. The integration in assessment and evaluation across professions and subject boundaries is emphasised to identify the key gaps between sustainability and design.