RSES Refrigeration Fundamentals & System Components 2 — Questions and Answers
Question 1: What is the primary function of a thermostatic expansion valve (TXV) in a refrigeration system?
- Compress the refrigerant to high pressure
- Meter refrigerant flow to maintain superheat at the evaporator outlet (Correct answer)
- Remove heat from the condenser
- Separate liquid and vapor refrigerant
Correct answer: Meter refrigerant flow to maintain superheat at the evaporator outlet
A TXV meters refrigerant flow into the evaporator to maintain a set superheat, preventing liquid slugging at the compressor.
Question 2: Which refrigerant property is measured by a gauge manifold's high-side gauge during normal operation?
- Evaporator saturation pressure
- Condenser saturation pressure (Correct answer)
- Suction line superheat
- Liquid line subcooling
Correct answer: Condenser saturation pressure
The high-side gauge reads the discharge pressure, which corresponds to the condenser saturation pressure.
Question 3: Subcooling in a refrigeration system refers to cooling the liquid refrigerant:
- Above its condensing temperature
- Below its condensing temperature (Correct answer)
- To its boiling point in the evaporator
- To the suction saturation temperature
Correct answer: Below its condensing temperature
Subcooling lowers liquid refrigerant temperature below its saturation point, preventing flash gas before the expansion device.
Question 4: A filter-drier in a refrigeration system is primarily installed to:
- Increase system capacity
- Remove moisture and contaminants from the refrigerant (Correct answer)
- Regulate refrigerant flow rate
- Cool the discharge gas
Correct answer: Remove moisture and contaminants from the refrigerant
Filter-driers adsorb moisture and trap particulates to protect the expansion device and compressor from damage.
Question 5: The suction line accumulator is designed to protect the compressor from:
- High discharge temperatures
- Liquid refrigerant slugging (Correct answer)
- Excessive subcooling
- Oil foaming at startup
Correct answer: Liquid refrigerant slugging
An accumulator collects liquid refrigerant and oil before the compressor inlet, releasing only vapor to prevent hydraulic damage.
Question 6: On a pressure-enthalpy (P-H) diagram, the horizontal distance across the evaporator represents:
- Refrigerant mass flow rate
- Latent heat absorbed (refrigerating effect) (Correct answer)
- Compression work input
- Condenser heat rejection
Correct answer: Latent heat absorbed (refrigerating effect)
The evaporator process appears as a horizontal line at low pressure; its horizontal length equals the enthalpy change, which is the refrigerating effect.
Question 7: Which type of condenser uses ambient air blown across the coil by a fan to reject heat?
- Evaporative condenser
- Water-cooled shell-and-tube condenser
- Air-cooled condenser (Correct answer)
- Double-pipe condenser
Correct answer: Air-cooled condenser
Air-cooled condensers use fans to move ambient air over finned coils, transferring refrigerant heat directly to the air.
RSES Refrigeration Fundamentals & System Components 2
What is the primary function of a thermostatic expansion valve (TXV) in a refrigeration system?