Experimental Study on Effects of Inlet Water Temperature on the Ramp Rate of a Thermal Chamber Having a Cascading Refrigeration System with A 3-Loop PID Controller

A thermal chamber is an enclosure which is used to test the effects of specified environmental conditions on electrical and electronic components of defense and aerospace applications. These environmental chambers contain a heating system and a refrigeration system to simulate hot and cold environmental conditions respectively. During the refrigeration cycle, a lot of heat will be generated which has to be removed from the chamber for achieving a higher ramp rate. The heat removal process is effective when the inlet water temperature of the chamber is minimum. An experimental study has been conducted to analyze the variations in the ramp rate of a thermal chamber with respect to the changes in the inlet water temperature. This inlet water basically goes to the heat exchanger of the refrigeration system. The experimental results show that inlet water temperature has a direct impact on the achieved ramp rate of the thermal chamber when the set ramp rates are between 7ºC/min to 10ºC/min, a very less impact when the set ramp rates are between 2ºC/min to 6ºC/min and almost negligible impact when the set ramp rate is 1ºC/min. In this paper, optimum inlet water temperature for various ramp rates is also identified.