RSES Evaporator Systems 3

Question 1

What is the primary reason a hot-gas defrost system heats evaporator coils faster than electric defrost?

Accepted Answer

Hot gas condenses inside the coil, releasing latent heat directly to the frost

Answer

When hot discharge gas condenses in the evaporator, it releases its latent heat of condensation directly to the coil, providing high heat transfer rates.

Question 2

A plate evaporator used in a beverage cooler develops oil logging. What is the most effective corrective action?

Accepted Answer

Increase suction gas velocity by reducing evaporator circuits or raising suction pressure slightly

Answer

Oil logging in evaporators is corrected by increasing suction gas velocity, which carries trapped oil back to the compressor through the suction line.

Question 3

During off-cycle defrost, what limits how completely frost is removed from a low-temperature evaporator?

Accepted Answer

The ambient or box temperature may not be warm enough to melt all frost before refrigeration restarts

Answer

Off-cycle defrost relies solely on warm air from the refrigerated space, which may not carry enough heat to fully defrost deeply frosted coils in sub-zero applications.

Question 4

What does a 'starved evaporator' mean in refrigeration terminology?

Accepted Answer

The evaporator receives insufficient liquid refrigerant, resulting in high superheat

Answer

A starved evaporator receives too little refrigerant, so the refrigerant evaporates early and the remaining coil surface superheats vapor without contributing to cooling.

Question 5

In a flooded evaporator system, refrigerant level is maintained by a:

Accepted Answer

Float valve that admits liquid to maintain a set liquid level

Answer

Flooded evaporators use a float valve (low-side or high-side float) to maintain the correct liquid refrigerant level in the evaporator vessel.

(RSES) Refrigeration Service Engineers Society Certification Practice Test

(RSES) Refrigeration Service Engineers Society Certification Practice Test

RSES Evaporator Systems 3