Evaporators and Condensers Flashcards

Why is a pressure relief valve required on a condenser or other pressure vessel that can be isolated?

Answer: To protect it from over-pressure, such as from fire or heat with valves closed

Relief valves vent refrigerant if pressure exceeds the vessel's design limit, preventing rupture.

Which type of heat exchanger is commonly used as a compact evaporator in liquid chillers?

Answer: Plate heat exchanger

Plate heat exchangers offer high heat transfer in a small footprint with a low refrigerant charge.

In cold weather, how is condensing pressure on an evaporative condenser commonly kept from falling too low?

Answer: By cycling fans or reducing fan speed

Reducing airflow lowers heat rejection, holding head pressure up for proper system operation.

What is a common method of protecting an evaporative condenser sump from freezing in winter?

Answer: Basin heaters or an indoor remote sump

Basin heaters or a sump located in heated space keep the water from freezing when idle.

Off-cycle (air) defrost is practical only when the refrigerated space is at what condition?

Answer: Above freezing, around 34°F or warmer

Off-cycle defrost relies on room air to melt frost, which only works when the room is above 32°F.

During hot gas defrost, what is the function of the defrost relief regulator on the evaporator outlet?

Answer: To hold coil pressure high enough to melt frost while relieving condensate to suction

The regulator keeps the coil at a saturation temperature above 32°F and passes condensed gas to the suction side.

The capacity of an evaporative condenser depends most directly on which ambient condition?

Answer: Wet-bulb temperature

Evaporative cooling is limited by how much moisture air can absorb, which is indicated by wet-bulb temperature.