Experimental Studies of Heat Transfer Under Natural Convection in Heat Pipe Insulated with Vacuum Chamber

An experimental model has been evolved to compute the RHT and CCHT under free condition of HPHEVC. The model evaluates the RHT and CCHT at different–different tilting position of a heat pipe from vertical axis, i.e., 0 °C, 15 °C, 30 °C, 45 °C and 60 °C and various inlet temperature provided by the heater to working fluid, i.e., 40 °C, 43 °C, 46 °C, 49 °C, 52 °C, 55 °C, 58 °C and 61 °C. Water, ethanol, methanol and butanol are utilized as working fluids. A hollow cylindrical steel heat pipe has been developed for calculating heat transfer rate under natural convective conditions. The heat pipe is covered with cuboids glass chamber for creating the vacuum across the pipe. This vacuum chamber utilized as insulating material for reducing the heat loss through heat pipe. The range of ambient temperature is about 25 ± 2 °C. The experimental study observed that inclination of heat pipe from vertical axis affected to the flow of working fluid and RHT and the inlet temperature of heater affected to the CCHT and RHT of a heat pipe. The value of CCHT depends upon the position of heat pipe and properties of working fluids. The RHT also depends upon the position of heat pipe and properties of working fluids. The experimental observations have been found that inclination of heat pipe increases from vertical axis 0° to 15°, then CCHT increases, and it starts decreasing beyond 15° tilt angle for inlet evaporator temperature 61 °C for methanol, ethanol and butanol used as working fluids. This study shows that when water is used as working fluid, then maximum value occurs of CCHT as compared to other working fluids like ethanol, methanol and butanol. The maximum practical value of coefficient of convective heat transfer is 1839.22 W/m2 °C at 0° tilt angle of heat pipe from vertical position at 61 °C inlet fluid temperature of evaporator when water used as working fluid. The maximum practical value of heat transport rate of HPHE is 775.90 W at 0° tilt angle of heat pipe from vertical position at 61 °C inlet fluid temperature of evaporator when water used as working fluid. The overall results conclude that the execution of experimental model of heat pipe is suitable for working under natural convection conditions.