Performance Investigation of Common Header Pulsating Heat Pipe for Thermal Management of Machines

Abstract

Common Header Pulsating Heat Pipe (CHPHP) is a two-phase passive heat transfer device made by replacing the multiple U-bends of a conventional Pulsating Heat Pipe (PHP). The present CHPHP model consists of ten parallel channels in the adiabatic section and common channels at the evaporator and condenser sections. The flat design at the evaporator and condenser should facilitate a better contact area with the surface to be cooled and heat rejected, thus justifying the design modification. The device is tested with various working fluids (acetone, methanol, and ethanol) at 50% of volumetric filling ratio (FR) and varying heat loads in the range of 0 - 28 W, keeping condenser temperature at 20℃. The lowest thermal resistance of 1.86 ℃/W is observed at FR of 50%, with acetone as the working fluid. Acetone has the lowest boiling point, latent heat of vaporization, dynamic viscosity, and (dP/dT)sat among the fluids at the condenser temperature [1]. The low boiling point helps acetone to vaporize earlier at a lower evaporator temperature and correspondingly condense, helping in the early startup of the device. The low latent heat of vaporization helps the formation of two phases in the liquid as less heat is needed to form the vapor bubbles. Dynamic viscosity helps the fluid flow easily, thus forming fluid circulation in these two-phase systems, aiding in heat transfer. (dP/dT)sat tells about the relative change in pressure compared to the temperature at the saturation point; this property, in simple words, helps in faster nucleation of liquid and the transfer of heat in such two-phase devices. Thus, the above-discussed thermo-physical properties are the variables affecting the device's performance and, in this case, suit the requirement. This investigation shows the device's potential for sensing, monitoring, and controlling temperatures (or thermal management) of devices, which are susceptible to thermal failure. The device can be seen as a substitute for the prevailing aluminum sinks, which fail to meet modern-day requirements.