Convective Heat-Transfer Characteristics of a Channel With One Surface Having Mini-Grooves in the Flow Direction and a Plain Surface Located at a Mini-Distance

Insulated-gate bipolar transistors (IGBTs) have been widely used in power transmission systems in recent years. However, a significant amount of electric energy is converted into heat when they are operated. It is necessary to maintain the temperature of the transistor junction in the power component below the maximum allowable temperature for its normal operation. In this paper, the convective heat-transfer characteristics of a channel with one surface having mini-grooves in the flow direction and another plain surface located at a mini-distance are reported. The surfaces can be arranged as a sandwiched-type cooler, in which the core plate with plain surfaces is located between two cold plates, with one surface having mini-grooves. Two IGBT units are mounted on the outside wall of the cold plates to save space. Water and a mixture of water and ethylene glycol are used as the coolants. The heat-transfer characteristics of the cooler are experimentally investigated. For comparison, a cooler with the same-sized plain-surface channels is tested under the same experimental conditions. The correlations of the mean Nusselt number and the friction factor are obtained, and the heat-transfer enhancement performance is evaluated under the identical mass flow rate, the identical pressure drop, and the identical pumping power criteria. The heat-transfer performance of the surface studied is much better than that of the microchannel surface under conditions in which a large area needs to be cooled. The results show that the mini-grooved channels can effectively enhance the heat transfer.