| A | B |
|---|
| boiling point | the temperature level of a liquid at which it begins to change to a vapor; the boiling temperature is controlled by the vapor pressure above the liquid |
| boiling temperature | the boiling temperature of the liquid can be controlled by controlling the pressure; the standard boiling pressure for water is an atmospheric pressure of 29.92 in. Hg (mercury) where water boils at 212*F |
| compressor | a vapor pump that pumps vapor (refrigerant or oil) from one pressure level to a higher pressure level |
| condenser | the component in a refrigeration system that transfers heat from the system by condensing refrigerant |
| defrost | melting of ice |
| dehumidification | removing moisture from air |
| direct-expansion evaporator (Dry Type) | the term used to describe an evaporator with an expansion device other than a low-side float type |
| evaporator | the component in a refrigeration system that absorbs heat into the system and evaporates the liquid refrigerant |
| expansion (metering) device | the component between the high-pressure liquid line and the evaporator that feeds the liquid refrigerant into the evaporator |
| film factor | the relationship between the medium giving up heat and the heat exchange surface (evaporator); this relates to the velocity of the medium passing over the evaporator. When the velocity is too slow, the film between the air and the evaporator becomes greater and becomes an insulator, which slows the heat exchange |
| finned tube evaporator | a copper or aluminum tube that has fins, usually made of aluminum, pressed onto the copper lines to extend the surface area of the tubes |
| flooded evaporator | a refrigeration system operated with the liquid refrigerant level very close to the outlet of the evaporator coil for improved heat exchange |
| high-temperature refrigeration | a refrigeration temperature range starting with evaporator temperatures no lower than 35*F, a range usually used in air conditioning (cooling) |
| hot gas | the refrigerant vapor as it leaves the compressor; this is often used to defrost evaporators |
| hot pull down | the process of lowering the refrigerated space to the design temperature after it has been allowed to warm up considerably over this temperature |
| low-temperature refrigeration | a refrigeration temperature range starting with evaporator temperatures no higher than 0*F for storing frozen food |
| medium-temperature refrigeration | refrigeration where evaporator temperatures are 32*F or below, normally used for preserving fresh food |
| multiple circuit coil | an evaporator or condenser coil that has more than one circuit because of the coil length; when the coil is too long, there will be an unacceptable pressure drop and loss of efficiency |
| off-cycle defrost | used for medium-temperature refrigeration where the evaporator coil operates below freezing but the air in the cooler is above freezing. The coil is defrosted by the air inside the cooler while the compressor is off cycle |
| saturated vapor | the refrigerant where all of the liquid has just changed to a vapor |
| stamped evaporator | an evaporator that has stamped refrigerant passages in sheet steel or aluminum |
| starved coil | the condition in an evaporator when the metering device is not feeding enough refrigerant to the evaporator |
| superheat | the temperature of vapor refrigerant above its saturation (change-of-state) temperature |
