CLASSIFICATION OF REFRIGERATION SYSTEM
Types of Refrigeration
Vapour Compression Refrigeration (VCR): uses mechanical energy
Vapour Absorption Re frigeration (VAR): uses thermal energy
Vapour Compression Refrigeration
Highly compressed fluids tend to get colder when allowed to expand.
If pressure high enough.
Compressed air hotter than source of cooling.
Expanded gas cooler than desired cold temperature.
Lot of heat can be removed (lot of thermal energy to change liquid to vapour).
Heat transfer rate re mains high (temperature of working fluid mu ch lower than what is being cooled)
Low pressure liquid refrigerant in evaporator absorbs heat and changes to a gas
The superheated vapour enters the compressor where its pressure is raised
The high pressure superheated gas is cooled in several stages in the condenser
Liquid passes through expansion device, which reduces its pressure an d controls the flow into the evaporator
Type of refrigerant-
-Refrigerant determine d by the required cooling temperature
-Chlorinated fluorocarb ons (CFCs) or freons: R-11, R-12, R-21, R-22 and R-502
Choice of compressor, design of condenser, evaporator determined by
Ease of maintenance
Physical space requirements
Availability of utilities (water, power)
Vapour Absorption Refrigeration-