Glossary
Glossary
- Saturation
The state of saturation is the coexistence of a refrigerant in a liquid and gas state.
- Condensation temperature and evaporation temperature
Condensation temperature: in the condenser, the refrigerant is condensed by the high-temperature gaseous refrigerant to
the temperature of the liquid refrigerant, that is, the saturation temperature under the condensing pressure.
Evaporation temperature: in the evaporator, the refrigerant evaporates from the liquid refrigerant to the temperature of the
gaseous refrigerant, that is, the saturation temperature under the evaporation pressure.
- Degree of subcooling and superheat
Subcooling: condensing temperature – condensing outlet temperature.
Superheat: evaporation outlet temperature - evaporation temperature.
The lower subcooling can make the refrigeration capacity of the system better. Adding subcooling circuit and economizer in
the refrigeration system is to increase the subcooling for refrigerant increasing.
The degree of expansion of the expansion valve (refrigerant charge) affects the degree of superheat.
The greater the degree of superheat, the smaller the opening of the expansion valve can be determined (the refrigerant
charge is less).
- Sensible heat and latent heat
The amount of heat required to raise the water temperature from 0 degrees to 100 degrees is sensible heat, the water is
heated to 100 degrees, and the hot water becomes water vapor, but the temperature is still 100 degrees. The heat required
for this process is called latent heat.
- Gauge pressure and absolute pressure
Gauge pressure: Gauge pressure refers to the pipeline pressure, refers to the pressure measured by pressure gauges,
vacuum gauges, U-shaped tubes, etc., also known as relative pressure. The “table pressure” starts with atmospheric pressure
and the symbol is Pg.
Absolute pressure: The pressure directly acting on the surface of a container or object is called "absolute pressure", the
absolute pressure value is absolute vacuum as a starting point, the symbol is PABS (ABS is a subscript) and the absolute
pressure is atmospheric pr gauge pressure.
At atmospheric pressure, the gauge pressure is 0 and the absolute pressure is 1.013 bar.
- Dry bulb temperature, wet bulb temperature and black ball temperature
Dry bulb temperature: the temperature measured by ordinary thermometers.
Wet bulb temperature: a wet cloth is wrapped around the thermometer, and the temperature indicates a drop due to the
evaporation of water. The temperature at this time is called the wet-bulb temperature.
The device, which has both the dry ball thermometer and the wet bulb thermometer, is called the dry humidy meter, which
can be used to measure the relative humidity in the atmosphere.
Black ball temperature: also called actual temperature, it indicates the actual sensory temperature expressed by temperature
when a person or an object is combined with radiant heat and convective heat in a radiant heat environment.
The black ball temperature measured is generally higher than the ambient temperature, which is the air temperature.
- Relative humidity and absolute humidity
Absolute humidity: the mass of water vapor in a unit volume of air is called the "absolute humidity" of air. It is a
representation of the physical quantity of atmospheric dryness and humidity. It is usually expressed in grams of water vapor
contained in 1 cubic meter of air.
Relative humidity: the actual water vapor density in air and the percentage of saturated water vapor density at the same
temperature are called the “relative humidity” of air.
The degree of dryness and humidity of the air is related to the degree of saturation of water vapor contained in the
air, but it is not directly related to the absolute amount of water vapor contained in the air.
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