CARO Refrigeration System Components 2 — Questions and Answers
Question 1: In an ammonia system, what is the primary function of the high-pressure receiver?
- Cool the discharge gas before it reaches the condenser
- Separate oil from discharge gas
- Store liquid refrigerant and absorb fluctuations in system charge (Correct answer)
- Remove non-condensable gases from the condenser
Correct answer: Store liquid refrigerant and absorb fluctuations in system charge
The high-pressure receiver stores condensed liquid and buffers charge changes as load varies.
Question 2: Which compressor type uses two meshing helical rotors to compress refrigerant vapor?
- Reciprocating compressor
- Centrifugal compressor
- Scroll compressor
- Rotary screw compressor (Correct answer)
Correct answer: Rotary screw compressor
A rotary screw compressor traps and compresses gas between intermeshing male and female rotors.
Question 3: What device on a screw compressor is used to vary capacity by changing the effective length of the rotors?
- Volume ratio plate
- Slide valve (Correct answer)
- Unloader solenoid on a cylinder
- Suction stop valve
Correct answer: Slide valve
The slide valve moves to recirculate gas back to suction, reducing the effective compression length and capacity.
Question 4: In an evaporative condenser, how is heat primarily rejected from the refrigerant?
- By direct contact between refrigerant and spray water
- By water flowing through tubes inside a shell
- By evaporation of water sprayed over the coil while air is drawn through (Correct answer)
- By air passing over dry finned coils only
Correct answer: By evaporation of water sprayed over the coil while air is drawn through
Evaporative condensers reject heat mainly through the latent heat of water evaporating off the coil surface.
Question 5: What is the purpose of an oil separator installed in the compressor discharge line?
- Separate liquid refrigerant from suction vapor
- Remove oil from discharge gas and return it to the compressor (Correct answer)
- Remove water from the refrigerant
- Filter solid contaminants from the liquid line
Correct answer: Remove oil from discharge gas and return it to the compressor
The oil separator captures oil carried over in discharge gas so it does not foul condensers and evaporators.
Question 6: Which component protects a compressor from liquid slugging by separating liquid from returning suction vapor?
- Oil separator
- King valve
- Suction accumulator or low-pressure receiver (Correct answer)
- High-pressure receiver
Correct answer: Suction accumulator or low-pressure receiver
Accumulators and low-pressure receivers trap liquid so only vapor reaches the compressor suction.
Question 7: What does a thermostatic expansion valve (TXV) control?
- Subcooling at the condenser outlet
- Oil pressure
- Discharge pressure
- Superheat at the evaporator outlet (Correct answer)
Correct answer: Superheat at the evaporator outlet
A TXV meters refrigerant flow to maintain a set superheat at the evaporator outlet using a sensing bulb.
CARO Refrigeration System Components 2
In an ammonia system, what is the primary function of the high-pressure receiver?