Thermal Performance Enhancement of L-Shaped Microgrooved Heat Pipe Containing Water-Based Al2O3 Nanofluids

An experimental study was performed to investigate the thermal performance of an L-shaped grooved heat pipe with cylindrical cross section, which contained 0.5wt% water-based Al2O3 nanofluid as the working fluid. The transient performance of the heat pipe and the effect of cooling water temperature on the heat transfer characteristics of the heat pipe were investigated. The outer diameter and the length of the heat pipe were 6mm and 220mm, respectively. Experimental results revealed that the temperature of the cooling water has a significant effect on the thermal resistance of the heat pipe containing nanofluids as its working fluid. By increasing the cooling water temperature from 5 degrees C to 27.5 degrees C, the thermal resistance decreases by approximately 40%. At the same charge volume, test results indicated an average reduction of 30% in thermal resistance of heat pipes with nanofluid as compared with heat pipe containing pure water. For transient conditions, unsteady state time for nanofluids was reduced by approximately 28%, when compared with water as the working fluid.