🔍 Key Concepts

• Thermostatic expansion valve (TXV) force balance: bulb pressure vs evaporator pressure vs superheat spring • Which force(s) tend to open the needle valve and which tend to close it • How the pressure from the sensing bulb is transmitted to the diaphragm compared with the evaporator (equalizer) pressure

💭 Think About

• From the illustration, trace where the capillary from the remote bulb connects on top of the diaphragm and decide whether that force pushes the needle valve open or shut • Look at the connection from the evaporator outlet (external equalizer) and identify whether its pressure acts on the same side of the diaphragm as the bulb pressure or on the opposite side • Ask yourself: which side of the diaphragm the spring is on, and whether it is helping the bulb pressure or helping the evaporator pressure

✅ Before You Answer

• Verify which pressure (bulb or evaporator) is on the top of the diaphragm and which is on the bottom • Confirm whether the spring force is acting in the same direction as the bulb pressure or in the opposite direction relative to valve opening • Make sure the condition you choose is a net force balance between one side that opens the valve and the other side that tends to close it, not just a single force acting alone