Effect of working fluids on thermal characteristic of a closed-loop pulsating heat pipe heat exchanger: A case of three heat dissipating devices

The closed-loop pulsating heat pipe (CLPHP) is a heat exchanger with a very high thermal conductivity. A single CLPHP is frequently used to release the heat between one heat dissipating device and one heat sink. However, some electrical applications have a number of heat dissipating devices. The CLPHP is applied to transfer the heat from multiple devices. Since the CLPHP primarily transfers the heat by means of working fluid´s phase change, the thermal characteristic of the CLPHP significantly depends on the working fluid type. In order to be the fundamental information for heat exchanger manufacturers, this study on effect of working fluids has been performed. Three electrical plate heaters were installed to the CLPHP as the heat dissipating devices. Experiments were conducted by varying the working fluid which was R123, ethanol and water. For each working fluid, the input heat fluxes of heat dissipating devices were also varied within 6 different patterns. It can be concluded that when the latent heat of evaporation increases - in a case of the vertical CLPHP, and when the dynamic viscosity of liquid increases - in a case of the horizontal CLPHP, the thermal resistance increases and the thermal performance consequently decreases.