Thermal performance of a single loop pulsating heat pipe with asymmetric adiabatic channel

Abstract

The thermal performance of an asymmetric single-turn closed-loop pulsating heat pipe (aCLPHP) has been investigated experimentally. In an asymmetric closed-loop, the working fluids may exhibit a consistent two-phase oscillatory-circulatory flow as a direct consequence of the capillary pressure difference. The adiabatic channels of different cross-sections will cause a pressure difference, boosting the flow of heated vapor and liquid. So, a novel aCLPHP of 208 mm with an evaporator of 35 mm length was fabricated from 2.4 and 3.4 mm inner diameter copper capillary tubes. The setup was subjected to gradual and abrupt heat loads (in vertical bottom heating mode) to find out the effects of inclination angles (0°, 30°, 60°, and 90°), working fluids, and filling ratios (FR) on the thermal performance. A constant supply of coolant in the condenser chamber through a bath assisted in dissipating the heat from the heat pipe. The simultaneous temperature and pressure signals at 10 Hz were recorded through a data acquisition system to analyze the thermal performance and flow characteristics. The average thermal resistance is mapped to different operating conditions to compare the conventional (uniform cross-section) and asymmetric adiabatic channel configurations. The pseudo-steady state operation was obtained up to 100 W power supply at 60% FR of pure water in the vertical orientation. Due to asymmetry, the heat carrying capacity was increased by 75% and 50% for working fluid water and acetone, respectively. The heat pipe was operating at lower inclination angles, except horizontal orientation only with pure water. Hence, introducing an asymmetric adiabatic section is a simple, reliable, and cost-effective approach to improve the capability of a single-turn CLPHP for the thermal management of various electronic components.