Analysis on the performance of convective heat transfer using temperature difference weighted with heat transfer capacity

Abstract

For electronic systems cooling analysis, it is incomprehensive to evaluate heat transfer performance only by one parameter, such as heat transfer coefficient, heat transfer area, heat transfer temperature difference and so on, especially for the multidimensional heat transfer problems. The parameter, temperature difference weighted with heat transfer capacity (TDW), is proposed to evaluate the heat transfer performance and the mean junction temperature of cooling systems with multiple heat source under the fixed heat flux. The weighted residual approach is employed to analyze the heat potential capacity transfer process in control volume of convection, then the variational principle is used as well to deduce the TDW, which could be used to optimize heat transfer performance in electronic systems cooling and reveal the relationship between temperature difference uniformity and heat transfer performance. Moreover, heat transfer performance could be improved by decreasing the TDW or improving the uniformity of temperature difference in cooling multiple heat sources. According to the theoretical analysis, the lower the TDW, which means the lower the thermal resistance, that is, the convection heat transfer is enhanced and heat transfer efficiency is improved. In order to validate the proposed theory, a new heat sink with slotted and folded fins is presented for the sake of obtaining lower value of the TDW. CFD simulations was conducted to validate the theory with the new heat sink. Simulation results indicate that both the mean junction temperature of heat sources and the TDW of the new designed heat sink with slotted and folded fins are lower than those of conventional heat sinks, so a lower TDW can be used to represent to the higher uniformity of temperature differences. Combined with theoretical calculation and CFD simulation, it could be concluded that for the fixed heat flux, if the TDW is low, uniformity of temperature differences will be high, and the mean junction temperature of heat source will be low as well, the efficiency of heat transfer will be high in convection. The new heat sink also could be used for decreasing the mean junction temperature of multiple heat sources and improving the heat transfer performance of conventional heat sinks under the fixed flux. In electronic systems cooling technology, a new parameter named TDW can be used to analysis the heat transfer performance and heat transfer efficiency.