CARO Evaporators and Condensers 5

Question 1

Why must an evaporator be pumped out before hot gas is introduced for defrost?

Accepted Answer

To avoid hydraulic shock from hot gas hitting liquid refrigerant

Answer

Hot gas entering a coil full of cold liquid can collapse vapor and cause dangerous liquid hammer.

Question 2

If liquid backs up in a condenser because the drain to the receiver is restricted, what happens?

Accepted Answer

Head pressure rises because effective condensing surface is lost

Answer

Liquid flooding the condenser tubes reduces the surface available for condensing, raising head pressure.

Question 3

What health hazard makes water treatment and cleaning of evaporative condensers especially important?

Accepted Answer

Legionella bacteria growth

Answer

Warm recirculating water can breed Legionella, which spreads through drift and causes Legionnaires' disease.

Question 4

In a gravity-flooded evaporator, where is the surge drum normally located?

Accepted Answer

Above the evaporator coil

Answer

The drum sits above the coil so liquid can flow by gravity into the coil and vapor can rise back to the drum.

Question 5

Why do low-temperature freezer evaporator coils typically use wider fin spacing than cooler coils?

Accepted Answer

To allow frost to build up without quickly blocking airflow

Answer

Wider fin spacing lets more frost accumulate between defrosts before airflow is choked.

CARO - Certified Assistant Refrigeration Operator Practice Test