Papers by Author: Li Wen Po

Abstract: Log mean temperature difference (LMTD) method neglecting the influence of heat radiation is conventionally used to calculate the total heat transfer rate of heat exchangers. From recent investigation of a single-pipe heat exchanger in some practical situations, it is found that the total heat transfer rate error of single-pipe heat exchanger obtained by LMTD method is up to 40% in the situation of oxidized metal heat exchanger with higher surface emissivity located in ambient air with low heat convection coefficient. A log mean heat transfer rate (LMHTR) method considering heat radiation has been developed to calculate the total heat transfer rate of a single-pipe heat exchanger and more accurate results can be achieved. It is also found in the present investigation that LMTD method is also not suitable to apply to non-insulated double-pipe heat exchangers and a more accurate LMHTR method considering heat radiation is developed to obtain the more reasonable results.

Abstract: The main function of junction box on a solar photovoltaic module is to transmit the electricity from solar photovoltaic panel to the load. The invented smart junction box is designed for the following purposes: (1) to optimize efficiency through auto control, (2) to reduce the vicious effect of the cloud and dust on electricity output, and (3) to prevent the battery from overcharging. When actuated, the temperature of inner transistor is raised up to 158 °C because it consumes more solar electric power than a conventional junction box. Thus, a more effective thermal diffusion system is invented to cool down inner transistor to avoid failure. It is found that the presented heat plate diffusion system modified from heat pipe is capable of satisfying all required thermal diffusion conditions of the smart junction box.