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The Essential Principles
The simplest way to describe a heat pump is a device that move
heat from one area to another. A heat pump works by extracting heat form a higher temperature "source" (TH) and converts some of that energy into work (W).
Excess energy is deposited into a lower temperature heat "sink" (TL).
Heat pumps obey the rules of thermodynamics and thus total energy must be conserved within the system.
From the above relationship, the total energy in the system can be expressed as TH= W+TL.
The fundamental rules
For a machine to be classified as heat engine it must adhere
to the following characteristics. 1. Heat engines operate on a cycle
2. They extract energy from a high temperature source
3. They convert some of the energy into usable work
4. They deposit the remainder of the energy to a lower temperature sink.
Common occurring examples are compressors in refrigerators which work on a regular cycle.