Pneumatic temperature control characteristics of a variable-load heat source with a pressure-controlled loop heat pipe

The operating temperature of a variable-load heat source was precisely regulated using a pneumatic temperature control method employing a pressure-controlled flat-evaporator loop heat pipe (PC-FELHP). In this method, the evaporator temperature of the PC-FELHP was adjusted by varying the compensation chamber pressure in response to the heat load change, thereby maintaining the heat source temperature within a narrow range. Under variable heat load conditions, the maximum deviation in the heat source temperature over a 100 W change in heat load was reduced from approximately 6.6 °C to 0.4 °C with the application of compensation chamber pressure control. In addition, the control characteristics of the heat source temperature under changes in the PC-FELHP operating position (i.e., elevation) were investigated. Upon activation of the pneumatic temperature control, the maximum deviation in the heat source temperature over a 60 mm elevation change was reduced from approximately 14.5 °C to 0.5 °C. Overall, with responsive pressure control of the compensation chamber, the operating temperature of the variable-load heat source under elevation changes of the PC-FELHP was maintained within approximately ±0.5 °C, demonstrating the efficacy of the pneumatic temperature control as a promising thermal control method for precision heat-generating devices. • Thermal control of a variable-load heat source was conducted with a loop heat pipe. • Pneumatic temperature control of a pressure-controlled loop heat pipe was attained. • The temperature of the variable-load heat source under position change was controlled. • The pneumatic temperature control method was responsive and precise. • The heat source temperature was controlled within ±0.5 °C over a 100 W heat load change.