Analysis of sintered wicked heat pipes for space constrained multiple component cooling

Contemporary electronic cooling applications can feature complex heat pipe configurations with multiple heat sources (MHS), and one or more bends in various locations to meet physical constraints. It is typically understood that implementing a bend or adding MHS to a heat pipe that was tested for a straight single heat source (SHS) heat pipe can degrade thermal performance. However, the severity of combining the two phenomenon and the effects of changing the location of a bend in a MHS heat pipe are unknown. In this context, this study presents an experimental investigation of the thermal performance of four configurations for 400 mm long, 6 mm diameter; cylindrical copper sintered heat pipes, where small, heated copper saddles are configured as evaporators: a pipe with a SHS; a pipe with MHS; an MHS heat pipe with an increasing bend angle from 0° – 90°; and an MHS heat pipe where the location of a 90° bend is moved along the axis. The results demonstrate that a bent MHS heat pipe does not act in a similar manner to a conventional SHS heat pipe or a straight MHS heat pipe. It was found that the thermal resistance increases by up to 65% when the configuration is changed from SHS to MHS, and bend angle is found to increase the resistance by a further 15-65%. For the MHS cases, bend location induces resistance increases of ~5-18%. Furthermore, the optimum bend location for the MHS case is found to be adjacent to the middle evaporator (of five), for cases in which the heat load is evenly distributed before and after the bend. The results suggest that the combination of MHS, bend angle and bend location have unique effects on the fluid transport mechanisms inside the heat pipe and, thus, thermal performance changes between bend location configurations. Therefore, it is concluded that a bent MHS heat pipe configuration should not be designed on the basis of the thermal characteristics for straight SHS heat pipes.