Nova Kool Manufacturing ULC

Basic Refrigeration Principles

Most users normally associate refrigeration with cold and cooling, yet the practice of refrigeration engineering deals almost entirely with the transfer of heat. This seeming paradox is one of the most fundamental concepts that must be grasped to understand the workings of a refrigeration system.

Cold is really only the absence of heat, just as darkness is the absence of light, and dryness is the absence of moisture.

Pressure-Temperature Relationships, Liquids

The temperature at which a liquid boils is dependent on the pressure being exerted on it. The vapor pressure of the liquid, which is the pressure being exerted by the tiny molecules seeking to escape the liquid and becomes vapor, increases with an increase in temperature until at the point where the vapor pressure equals the external pressure, boiling occurs.

Water at sea level boils at 212° F.,. but at 5,000 feet elevation it boils at 203° F.' due to the decreased atmospheric pressure. If some means, a compressor for example, were used to vary the pressure on the surface of the water in a closed container, the boiling point could be changed at will. At 100 psig, the boiling point is 327.8' degrees F., and at 1 psig, the boiling point is 102° F.

Since all liquids react in the same fashion, although at different temperatures and pressure, pressure provides a means of regulating a refrigerating temperature. If a cooling coil is part of a closed system isolated from the atmosphere and a pressure can be maintained in the coil equivalent to the saturation temperature (boiling point) of the liquid at the cooling temperature desired, then the liquid will boil at that temperature as long as it is absorbing heat -- and refrigeration has been accomplished.

Katey Werner