🔍 Key Concepts

• Thermostatic expansion valve (TEV/TXV) basic operation in a refrigeration cycle • Relationship between bulb pressure, evaporator pressure, and the superheat spring • Which side of the diaphragm tends to OPEN the valve vs which forces tend to CLOSE it

💭 Think About

• Picture the diaphragm inside the TEV: ask yourself which pressure is connected to the sensing bulb on the suction line and what that pressure is trying to do to the valve pin. • Consider what evaporator pressure represents: is it pushing up or pushing down on the diaphragm relative to the bulb pressure side? • Think about the superheat spring: is it there to help the valve open more easily, or to resist opening until a certain superheat is reached?

✅ Before You Answer

• Be clear which pressure is from the thermal bulb on the outlet of the evaporator and which is evaporator internal pressure under the diaphragm. • Identify which forces act on the top of the diaphragm and which on the bottom, then decide which direction corresponds to valve opening vs closing. • Verify that the final choice has one side as a single opening force and the opposite side as combined closing forces (or vice versa) that match the physical layout of a standard TEV.