An increase of superheat on the "bulb" of a TXV causes the valve to do what?

When the superheat at the bulb of a thermostatic expansion valve (TXV) increases, it indicates that the refrigerant vapor exiting the evaporator is hotter than necessary for superheating. The function of the TXV is to regulate the amount of refrigerant flowing into the evaporator to maintain the desired superheat, ensuring that the compressor is not fed with liquid refrigerant.

As superheat increases, it signals the TXV to allow more refrigerant into the evaporator to cool down the superheated vapor. Consequently, this adjustment provides more refrigerant flow to match the cooling demands of the system. Thus, the valve either stays open or opens more in response to the rising superheat to ensure optimal performance and prevent compressor damage from liquid refrigerant. This mechanism helps maintain system efficiency and cooling capacity.