Refrigerators

Summary

A refrigerator is any kind of enclosure (like a box, cabinet, or room) whose interior temperature is kept substantially lower than the surrounding environment.
Types of Refrigerators
- non-mechanical
  - for example: ice box, root cellar, wine cellar
  - are not often considered true refrigerators
- mechanical
  - vapor compression
  - vapor absorption
  - multievaporator, cascade
  - gas cycle, air cycle
  - pulse tube
  - thermoacoustic
- electronic
  - thermoelectric
  - magnetic, magneto-calorific
An air conditioner is a mechanical system in a room, building, or vehicle for controlling …
- temperature (by providing cool air),
- humidity (by providing dry air),
- and ventilation (by providing fresh air).
A heat pump is a device for moving heat mechanically.
- A heat pump can move heat against the temperature gradient (from cold to hot).
- Refrigerators and air conditioners are examples of heat pumps.
- In common usage, the tem heat pump often refers to air conditioners that can be run …
  - "forward" to cool a building in summer by extracting heat from the building and depositing it in the environment (refrigerating the building and heating the environment) or
  - "backward" to warm a building in winter by extracting heat from the environment and depositing it in the building (refrigerating the environment and heating the building).
Energy is conserved in the operation of a heat pump.
- The heat extracted from the cold reservoir (Q_c) plus the work done by the system (W) is equal to the heat deposted in the hot reservoir (Q_h).
The coefficient of performance (COP) is the ratio of the useful energy output of a system to the mechanical work required to operate it.
- The COP is a measure of the effectiveness of a mechanical device or system at performing some task.
- The COP of a heat pump used as …
  - an air conditioner or refrigerator is the ratio of the heat extracted to the mechanical work required to operate it.
  - a heater is the ratio of the heat deposited in the room to the mechanical work required to operate it.

	conservation of energy	coefficient of performance
air conditioner and refrigerator	Q_c + W = Q_h	COP = Q_c/W
heat pump used for heating	Q_c + W = Q_h	COP = Q_h/W

The Physics Hypertextbook

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