Evaporators & Expansion Devices Flashcards

What is an accumulator and where is it installed in a refrigeration system?

Answer: A vessel installed in the suction line between the evaporator and compressor to catch liquid refrigerant and prevent slugging

A suction line accumulator is a vessel that catches any liquid refrigerant or oil carryover from the evaporator, allowing only vapour to enter the compressor suction and protecting against liquid slugging.

What is the purpose of a suction line filter-drier?

Answer: To remove moisture and debris from the suction line, protecting the compressor from acid, moisture, and particulates after a compressor burnout

A suction line filter-drier is typically installed after a compressor burnout to remove acid, moisture, and carbon deposits from the refrigerant before they can damage the replacement compressor.

What is the purpose of a pressure-limiting TXV (also called a 'maximum operating pressure' or MOP TXV)?

Answer: To prevent evaporator pressure from rising above a set point during high-load conditions, protecting the compressor motor from overload

A MOP TXV has a built-in feature that limits the maximum suction pressure (and therefore evaporator temperature) to protect the compressor motor from drawing excessive current during pulldown of a warm load.

What effect does a low evaporating temperature have on compressor capacity?

Answer: It decreases compressor capacity because suction vapour density decreases, reducing the mass of refrigerant pumped per revolution

At lower evaporating temperatures, suction pressure decreases and the refrigerant vapour becomes less dense; since the compressor displaces a fixed volume, less refrigerant mass is moved per revolution, reducing capacity.

What is a solenoid valve used for in the liquid line of a refrigeration system?

Answer: To open or close the liquid line fully in response to an electrical signal, controlling refrigerant flow on-off for pumpdown or zone control

A liquid line solenoid valve is an electrically actuated on-off valve that opens to allow refrigerant flow when the system calls for cooling and closes to stop flow, commonly used in pumpdown control cycles or multi-zone systems.

What is 'pumpdown control' in a refrigeration system?

Answer: A control strategy that closes the liquid line solenoid valve on system shutdown, allowing the compressor to pump refrigerant out of the low side into the receiver before stopping

Pumpdown control closes the liquid line solenoid on a call to stop cooling, and the compressor continues to run until suction pressure drops to a low-pressure cutout, drawing refrigerant out of the low side into the receiver to prevent migration during the off-cycle.