Question 180Refrigeration & AC - Assistant Engineer

The correct answer is C) an increase in sensing bulb temperature. The thermostatic expansion valve in a refrigeration system functions to maintain a constant superheat at the outlet of the evaporator. When the sensing bulb temperature increases, the pressure in the sensing bulb also increases, causing the diaphragm to flex downward. This opens the valve further, allowing more refrigerant to flow into the evaporator, which in turn increases the evaporator pressure. The other options, such as an increase in evaporator pressure (A) or an increase in the superheat setting (D), would have the opposite effect on the valve's opening.