Phase change materials (PCMs) are considered the most promising cooling technology due to their high latent heat, good reversibility, and low cost. However, in practical applications, PCMs encounter problems such as a sharp temperature increase after full melting and low thermal conductivity. To solve these problems, a new double helix-type liquid cooling plate is developed and coupled with a hydrated salt composite PCM (CPCM) for battery pack cooling. The modified CPCM has a high latent heat (249 J/g), suitable phase change temperature (35 °C), improved thermal conductivity to 1.86 W/(m·K), and reduced subcooling to 1.9 °C. The design of the liquid cooling plate structure can make the average water temperature on both sides of each cell approximate, thereby ensuring the temperature uniformity for the battery pack. A battery module system test rig is constructed and the heat dissipation effect for the battery module is compared with four cooling methods. The results reveal that the CPCM/liquid coupled cooling method is the most effective for cooling the battery pack. At a low coolant flow rate of 0.5 L/min, the maximum temperature difference for the coupled battery module is retained at 1.88 °C, and the average temperature is found to increase by only 9.6 °C. In addition, different coolant flow rates and control strategies of the coupled heat sink system are tested and compared. An optimal strategy is selected for the cyclic charge/discharge test of the coupled cooling module. The system is found to maintain good cooling performance and temperature uniformity after four charge/discharge cycles, and the highest temperature peak for the battery pack is only 40.3 °C, which is within the normal operating temperature range.

No abstract

The elastohydrodynamic model of hydrodynamic air foil bearing has been built to study the influence of rotor speed, the friction coefficient between bearing components, load and other parameters on the foil displacement of hydrodynamic air bearing under steady-state conditions. The static characteristics of hydrodynamic air foil bearing are predicted by using the numerical simulation method. The results show that the radial displacement of the foil is the smallest at both ends of the bearing and the largest at the middle of the bearing, while the top foil changes gently along the width of the bearing away from the maximum pressure. After increasing the rotating speed, the maximum fluid pressure improves and the action position shifts, and the increase of rotating speed has a significant impact on the maximum pressure. improving the friction coefficient μ2 between the bump foil and the bearing sleeve has different effects on the displacement of the foil. When μ1 is 0.1, by promoting μ2, the transverse displacement of the top foil at the pressure peak increases by 20.9%, the longitudinal displacement is reduced by 8.9%, the transverse displacement and the maximum longitudinal negative displacement of the bump foil are decreased by 53.2% and 31.7% respectively. Furthermore, the longitudinal displacement of bump foil at the fixed end has been reduced by increasing the load, and the relative size of the friction coefficient between the components affects the size and direction of the foil displacement at the same load.