Utilization and performance of low-temperature heat pipes in thermal applications

The purpose of tins study is to investigate the performance oflow-temperature heat pipes. A special machining technique has beendeveloped for production of heat pipes with internally axial grooves andinternal smooth surface. Experiments are performed to investigate theeffect of heat load, cooling water flow rate, filling ratio, (volume ofworking fluid to the evaporator volume) and the inclination angle on heatpipes performance. Two heat pipes are used which are made of copperwith 2.54 cm outside diameter. They have 31 cm long evaporator, 32cmlong adiabatic section, and 31 cm long condenser, with acetone as theworking fluid. The first has an axial groove heat pipe with a groove width0.8 mm and a depth 1 mm and tile second has wrapped screen heat pipeusing 100 mesh copper screen wick. The inclination angle in this study isvaried from 0° (vertical position) to 90° (horizontal position). Theexperimental test rig consists of a copper/acetone heat pipes, a heater forevaporator section equipped with a digital clamp-meter to measureelectrical power, a direct jacket calorimeter for heat removal (condenser),temperature measurement equipment, a vapor temperature probe and someother auxiliary equipment.Wick fabrication and insertion was accomplished using a woodenmandrel with suitable dimensions. Heat pipe wall surface temperature wasmeasured at three different locations in each section.Computer programs were constructed III order to calculateentrainment limit, boiling limit, temperature DROP, and heat transfercoefficient for the two types of the heat pipes.Results of present study showed that: