Control characteristic — another name for a thermostatic expansion valve (TEV) In vapor-compression systems, the thermostatic expansion valve is commonly referred to by which functional description?

Introduction / Context:
Expansion devices regulate refrigerant flow to the evaporator. The thermostatic expansion valve (TEV or TXV) uses a sensing bulb to modulate flow according to evaporator outlet superheat.

Given Data / Assumptions:

• TEV senses temperature at the evaporator outlet and compares it to pressure via an internal diaphragm.
• Goal: maintain a nearly constant superheat to avoid liquid floodback and ensure coil utilization.

Concept / Approach:
“Constant superheat valve” aptly describes the TEV’s control objective. As load increases, outlet superheat rises; the valve opens to feed more liquid. As load drops, superheat falls; the valve throttles to prevent liquid carryover.

Step-by-Step Solution:

Verification / Alternative check:
System commissioning procedures specify setting or checking TEV superheat, confirming its functional name.

Why Other Options Are Wrong:
Constant pressure or temperature valves describe other regulators; fixed-orifice and float valves are different device types not using a thermostatic bulb.

Common Pitfalls:
Assuming TEVs hold evaporator pressure constant; that is influenced by compressor capacity control, not the TEV.

Final Answer:

constant superheat valve