Refrigeration System Components Flashcards

What is the main purpose of a hot gas defrost system on an ammonia evaporator?

Answer: Use compressor discharge gas to melt frost from the coil

Hot gas defrost routes warm discharge vapor through the coil to melt accumulated frost.

What is the function of the high-side float valve in a refrigeration system?

Answer: Pass liquid to the low side as fast as it is condensed

A high-side float drains liquid from the condenser or receiver to the low side at the rate it condenses.

On a reciprocating compressor, what indicates a possible broken or leaking discharge valve?

Answer: Higher-than-normal suction pressure and reduced capacity

A leaking discharge valve lets hot gas back into the cylinder, raising suction pressure and lowering pumping capacity.

What does a capillary tube metering device rely on to control refrigerant flow?

Answer: Fixed length and small bore creating a pressure drop

A capillary tube is a fixed restriction whose length and diameter set the pressure drop and flow rate.

In an ammonia plant, what is the purpose of a thermosiphon oil cooler on a screw compressor?

Answer: Cool compressor oil using liquid refrigerant circulated by natural convection

Thermosiphon oil coolers use liquid ammonia from the receiver that boils in the cooler and returns by gravity and density difference.

What does an electronic expansion valve (EEV) use to adjust its opening?

Answer: A controller signal driving a stepper motor or pulse-width modulated actuator

EEVs use sensors and a controller to position the valve electronically for precise superheat or level control.

Which condition is most likely if non-condensable gases accumulate in an ammonia condenser?

Answer: Abnormally high condensing (head) pressure

Non-condensables add their partial pressure and blanket heat transfer surfaces, raising head pressure and energy use.