Refrigeration is a process in which work is done to move heat from a low temperature to a high temperature and typically also from one location to another. The work of heat transport is traditionally driven by mechanical work, but can also be driven by heat, magnetism, electricity, laser, or other means.
Refrigeration can be used for a variety of purposes:
- refrigerating food
- cooling spaces
Technical
Terms associated with refrigeration:
- coefficient of performance or COP is a measurement of the energy efficiency of a refrigeration (or heat pump) system.
COP for refrigeration is calculated as: Cooling effect/Work input, or COPR= QL/Wnet,in where QL is the desired energy into the low temperature environment and Wnet,in is the required work input into the refrigerator itself.
Carnot efficiency is a theoretical maximum efficiency that can be achieved by running a carnot cycle. The theoretical carnot, or nth=Wnet/QH, where Wnet equals the work input into the refrigerator and QH equals the energy in the high temperature reservoir. nth can also be equated as QH-QL/QH, where QH is the energy in the high temperature reservoir and QL is the energy in the low temperature reservoir.
Flow rate (massrate or m dot) can be equated as: Qdot/h1-h4, where Qdot equals the rate of energy used and the different h values signify enthalpy and can be found or interpolated from a thermodynamic table.
Conversely, Qdot=mdot(uout-uin), where the different u values signify internal energy and can be found or interpolated from a thermodynamic table.
Conversions
Refrigeration systems are generally labelled in terms of tons of refrigeration. One ton of refrigeration is equal to 12,000 Btu/hour or 211 kJ/min.
1 BTU = 778 ft-lbf of work 1 Watt = 3.4122 Btu/hour 3,412 Btu= 1 kwh 1 kWh = 3.6 MJ 1 tonne = 1000 kg 1 BTU/sec= 1.414 hp
Interwiki links
- wikipedia:Refrigeration
- Phase-change incubator, a low cost way for health workers to incubate microbial samples.
- Pot-in-pot refrigerator, using clay pots, cloth and water to keep food fresh.