1 High- and Very-High-Pressure Refrigeration Systems Free Online FlashCards

What saturation-pressure range defines a high-pressure refrigerant?

High pressure means a refrigerant’s liquid-phase saturation pressure is 170 to 355 psia at 104°F (40°C).

What is the difference between psia and psig?

Psia is absolute pressure; psig is pressure measured relative to the surrounding atmosphere.

How do EPA categories classify R-410A and R-134a?

R-410A is high pressure, while R-134a is medium pressure under the EPA categories described.

What does the compressor do in a vapor-compression system?

The compressor draws in low-pressure vapor and raises its pressure and temperature.

Why can two refrigerants have different pressures at the same temperature?

Pressure depends on both refrigerant identity and temperature, so different refrigerants can have substantially different pressures at the same temperature.

Does a pressure category indicate toxicity or flammability?

No. Pressure category does not by itself show whether a refrigerant is toxic, flammable, or an asphyxiant.

Why can trapped liquid refrigerant create a pressure hazard?

Liquid trapped between closed valves can expand as it warms, raising pressure in the isolated section.

What qualifies a refrigerant as very high pressure?

A refrigerant is very high pressure if its critical temperature is below 104°F, or its saturation pressure exceeds 355 psia at 104°F.

What determines a refrigeration appliance’s EPA pressure category?

The category depends on the refrigerant’s properties, not system size, compressor type, or a pressure-gauge reading.

What happens to refrigerant in the condenser?

The condenser rejects heat, causing refrigerant vapor to condense into liquid on the high side.

What is the expansion device’s role?

The expansion device meters refrigerant and reduces its pressure before it enters the evaporator.

What happens in the evaporator?

The evaporator absorbs heat as refrigerant evaporates at lower pressure.