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The power generated from TEG is relatively unstable owing to temperature variations at its hot and cold side terminals. The dc-dc converters can provide more stable power output thereby improving the overall efficiency of TEG system. However, to facilitate better performance improvement, maximum power point tracking (MPPT) algorithm can be applied to extract maximum power from TEG system. Therefore, parameter analysis of a TEG/dc-dc converter system in different modes is being carried out. A TEG-dc-dc boost converter model is analysed in both MPPT and direct pulse width modulation (PWM) modes subjected to a variable load. To further study the capability of dc-dc converters to stabilise the TEG power output, increasing ramp and random hot side temperature is applied to the MPPT and direct PWM based modes so that the effect on output parameters i.e. voltage and power, can be analysed. It is noted that even for the random temperature input to the TEG, the output voltage resulting from the converter is almost constant. Therefore dc-dc converters are able to stabilise the power generated from TEG. It is also observed that dc-dc converter with MPPT based model is able to effectively extract the maximum power without having to adjust any component from the MPPT algorithm as it is the case with direct PWM based model. From the study, it has been established that proper selection of converter components is necessary to reduce converter losses as well interferences on the load connected to TEG-dc-dc converter system.

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.

This study investigates the thermal performance of composite ultra-thin heat pipes (UTHPs). UTHPs are fabricated by flattening cylindrical heat pipes with outer diameter of 2 mm. The thickness and width were 0.8 mm and 2.7 mm, respectively. The composite wick structure is made of sintered copper foam-mesh wick (CFMW). CFMW combines the good heat transfer performance of copper foam and the high mechanical strength of mesh. The manufacturing process of UTHP was studied and the thermal performance of UTHP samples were investigated experimentally. The results indicate that the optimum filling ratio of UTHPs is 100% and the maximum temperature difference is 3.7 °C under the maximum heat transport capacity of 5 W. The thermal resistances of UTHPs increase gradually with the heat power before drying out. Too low or too high filling ratios will reduce the heat transfer efficiency of UTHPs by increasing the thermal resistances. With the optimum filling ratio of 100%, the evaporation thermal resistance of UTHP is found to be 0.29 K/W and the condensation thermal resistance is 0.45 K/W at the heat load of 5 W.

AbstractAn overview of current thermal challenges in transport electrification is introduced in order to underpin the research developments and trends of recent thermal management techniques. Currently, explorations of intelligent thermal management and control strategies prevail among car manufacturers in the context of climate change and global warming impacts. Therefore, major cutting-edge systematic approaches in electrified powertrain are summarized in the first place. In particular, the important role of heating, ventilation and air-condition system (HVAC) is emphasised. The trends in developing efficient HVAC system for future electrified powertrain are analysed. Then electric machine efficiency is under spotlight which could be improved by introducing new thermal management techniques and strengthening the efforts of driveline integrations. The demanded integration efforts are expected to provide better value per volume, or more power output/torque per unit with smaller form factor. Driven by demands, major thermal issues of high-power density machines are raised including the comprehensive understanding of thermal path, and multiphysics challenges are addressed whilst embedding power electronic semiconductors, non-isotropic electromagnetic materials and thermal insulation materials. Last but not least, the present review has listed several typical cooling techniques such as liquid cooling jacket, impingement/spray cooling and immersion cooling that could be applied to facilitate the development of integrated electric machine, and a mechanic-electric-thermal holistic approach is suggested at early design phase. Conclusively, a brief summary of the emerging new cooling techniques is presented and the keys to a successful integration are concluded.

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.

Thermoelectric (TE) devices are regarded as alternative and environmentally friendly 7 for harvesting and recovering heat energy. Particularly, thermoelectric generators (TEGs) 8 are used for converting heat into electricity. One of the challenges behind TEG is that the 9 power generated is unstable and therefore needs proper power conditioning mechanism 10 before it is supplied to the load. Moreover, it is necessary to track the maximum power 11 point (MPP) at all times so that maximum power is always extracted from TEG devices. 12 The objective of this work is to analyse the performance of a dc-dc converter with 13 maximum power point tracking (MPPT) enabled by incremental conductance (IC) method. 14 The simplified model is used as the basis for TEG design while the dc-dc boost converter 15 is used for boosting and stabilising the power generated from TEG. The results of the IC 16 based MPPT approach have been compared with those of perturb and observe (P&O) based 17 MPPT from a previous researcher. The results indicate that the IC based MPPT approach 18 is able to track the MPP but with relatively lower efficiencies than the P&O based MPPT 19 method. The matching efficiency within a temperature range of 200oC– 300oC is in the 20 range of 99.92% - 99.95% for P&O and 99.46% - 99.97% for IC method. However IC 21 based MPPT method has higher voltage gain and converter efficiency than the P&O based 22 MPPT method. Therefore, dc-dc converters are able to improve the steady state 23 performance of TEG system as well as boosting the voltage to the desired level, hence 24 improving the overall performance of TEG system. Although both P&O and IC are two 25 classical algorithms that can be implemented to extract the maximum power from TEG, 26 the comparative study has established that P&O technique outperforms the IC method.

The development of electric cars has well been regarded as a major solution for tackling the challenges of carbonneutrality faced by the modern communities. Electric motor is certainly the core and most important components of an electric car, and the thermal management for electric motors has drawn increasing attention from both industry and academic society. This is because electric motors in modern electric cars are required to be more powerful and competitive with higher torque, higher speed and higher power density, therefore the efficient thermal management has become essential to maintain the motors efficiency, durability and safety. The failure of thermal management will result in demagnetization of magnets, aging of the insulation materials, decrease of efficiency, shorter lifetime and even burnout of motors. To enlighten the future research, in this paper, both the theoretical modeling and experimental investigations of the latest thermal management methods are reviewed. The state-of-the-art of various thermal management techniques, including air cooling (natural and forced air cooling, air impingement cooling) and liquid cooling (water/oil jacket cooling, jet impingement cooling, spray cooling, immersion cooling, slot channel forced convection cooling) for the stator, winding and rotor are critically presented. Meanwhile, heat transfer enhancement methods by conduction based on potting materials, thermal paste, heat guides, PCMs and heat pipes are highlighted. Following that, hybrid thermal management technologies to address extreme conditions are also discussed. In the last section, some suggestions are given for future possible research and applications. The paper is expected to be a good reference and inspiration for the development of new thermal management concepts of electric motors.