Expansion Devices Flashcards

A float valve in a flooded evaporator system responds to changes in:

Answer: Refrigerant liquid level

The float valve maintains a constant liquid refrigerant level in the flooded evaporator by opening and closing based on liquid level.

What is the primary advantage of an electronic expansion valve (EEV) over a TXV?

Answer: More precise refrigerant flow control across varying conditions

EEVs use electronic controls and stepper motors for precise modulation, outperforming TXVs in variable-load or multi-evaporator applications.

The TXV sensing bulb must be mounted in proper thermal contact with the suction line because:

Answer: It must accurately sense refrigerant temperature to control superheat

The sensing bulb contains a refrigerant charge that expands or contracts based on suction line temperature, which opens or closes the TXV.

Which of the following would cause a TXV to hunt (cycle open and closed rapidly)?

Answer: Oversized TXV for the system load

An oversized TXV over-responds to load changes, causing hunting as it continually opens too far then closes too far.

In a refrigeration system using a capillary tube, what happens during the off cycle?

Answer: Pressures equalize between high side and low side

A capillary tube has no check valve function, so pressures equalize during the off cycle, making startup easier for the compressor.

What is the function of the distributor nozzle connected to a TXV outlet in a multi-circuit evaporator?

Answer: It evenly distributes refrigerant to all evaporator circuits

The distributor nozzle splits the refrigerant mixture from the TXV into equal portions for each evaporator circuit to ensure uniform loading.

A TXV that is overfeeding (flooding) the evaporator will most likely cause:

Answer: Liquid refrigerant entering the compressor

Overfeeding sends excessive liquid through the evaporator, and unevaporated liquid entering the compressor causes liquid slugging damage.