Designer fluid performance and inclination angle effects in a flat grooved heat pipe

Abstract

A flat heat pipe was used to study the effects of an advanced working fluid previously shown to improve the thermal performance of phase change heat transfer devices through surface augmentation of the wick. Surface structures were created by the working fluid through chemical oxidation reactions and solubility forced deposits. The modular heat pipe apparatus allowed water and the advanced working fluid to be compared in the same device. A clear viewing cover plate allowed for visual observation of the evaporating section of the heat pipe. The setup was first tested for repeatability with water and produced three sets of thermal resistance values within 5%. The advanced working fluid decreased thermal resistance by approximately 20% and nearly tripled the capillary limit. The advanced working fluid was also tested at larger angles and was able to maintain normal operation due to the additional capillarity of the fluid deposits. This work also provides insight into the design of fluids for other wick geometries by examining the effect of increasing the concentration of the fluid and how the fluid deposits on the surface. The results indicate that concentration of the fluid was over the amount necessary for the evaporative surface area of the grooved wick.