FREE CARO Evaporators and Condensers Questions and Answers

Question 1

An operator observes a steady increase in the condenser approach temperature. Which of the following is the MOST likely cause?

Accepted Answer

Fouling or scale buildup on the condenser's heat transfer surfaces.

Answer

A significant drop in the ambient wet-bulb temperature.

Answer

Excessive subcooling of the liquid refrigerant leaving the condenser.

Answer

The system has a low refrigerant charge.

Question 2

In an industrial ammonia refrigeration system, what is the primary purpose of an automatic purger connected to the high side of the system?

Accepted Answer

To remove non-condensable gases like air and hydrogen.

Answer

To remove refrigerant that has broken down over time.

Answer

To drain excess lubricating oil from the condenser.

Answer

To vent off high-pressure liquid refrigerant during an over-pressure event.

Question 3

During a hot gas defrost cycle for a freezer evaporator, which of the following actions occurs?

Accepted Answer

Hot, high-pressure vapor from the compressor discharge is diverted into the evaporator.

Answer

The compressor shuts down and liquid refrigerant is drained from the evaporator.

Answer

The evaporator fans continue to run to circulate warm air from the freezer space.

Answer

Cold liquid refrigerant is circulated through the coil to melt the frost.

Question 4

A flooded-type shell-and-tube evaporator is being used to chill brine. Where are the refrigerant and the brine typically located within this component?

Accepted Answer

The brine is in the tubes, and the refrigerant is in the shell.

Answer

The refrigerant is in the tubes, and the brine is in the shell.

Answer

Both the refrigerant and the brine are mixed together in the shell.

Answer

The refrigerant and brine flow through alternating plates.

Question 5

Which of the following conditions would most likely cause an evaporator to become 'starved' of refrigerant?

Accepted Answer

A dirty or clogged filter-drier upstream of the expansion device.

Answer

An overcharged system.

Answer

The superheat setting on the expansion valve is set too low.

Answer

The evaporator fans are shut off.

Question 6

An operator at a plant with an evaporative condenser notices that the discharge (head) pressure is significantly higher than normal on a mild day. The water spray nozzles are working correctly and the sump water level is normal. What is the MOST appropriate next check?

Accepted Answer

Verify that the condenser fans are operating correctly and airflow is not obstructed.

Answer

Check for a low refrigerant charge in the system.

Answer

Check the superheat at the evaporator outlet.

Answer

Ensure the compressor's oil level is correct.