Transient behavior of temperature sensor of expansion valve with various installation

Thermostatic expansion valves are widely used in heat pump systems to control the liquid refrigerant supply to the evaporator based on the degree of superheat at its exit. In a typical thermostatic expansion valve, the degree of superheat at the exit of an evaporator is measured by a temperature bulb sensor that is in contact with the evaporator outlet tube. In this work, a method to experimentally determine the transient behavior of a temperature bulb sensor of a thermostatic expansion valve is presented. From the experimental data, three parameters were extracted and then used in a mathematical model to reproduce the transient behavior of the temperature bulb sensor. In addition, four methods of installing the temperature bulb sensor to the evaporator outlet tube were experimentally studied. The tube–bulb system with the installation band and the insulation showed the best accuracy.