Experimental Investigation of the Effects of Relative Physical Orientation between Evaporator and Condenser for a Loop Heat Pipe

This research examined the effects on performance of varying angular orientation and height differences between evaporator and condenser for a loop heat pipe. Performance was defined as the difference in temperature between evaporator and condenser (DELTA T). The pipe was evaluated at varying input power (Qin) for: varying evaporator and condenser angles, different coolant temperatures, and varying relative height differences. All analysis included only steady state operation. The performance was influenced by condenser angles, with an optimal condenser angle for best performance being +45 degrees from horizontal. Additionally, the evaporator angles were found to influence performance only at low Qin and low coolant temperatures. For high Qin\u27 performance was independent of evaporator angle. For small Qin the DELTA T increased (poorer performance) with decreasing coolant temperature. However, for high Qin the DELTA T was independent of coolant temperature. For small Qin the DELTA T increased with increasing heights of evaporator over condenser. However, for high Qin the DELTA T was independent of the height difference. Additionally, pipe operation was sensitive to the rate of decrease of Qin. Finally, an unexplained anomaly shows the pipe to operate at two different DELTA T values for a given heat input