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Temperature, work and heat

The temperature scale is now mainly used by the Celsius scale, on the basis of nominally the melting point of ice at 0C and the boiling point of water at atmospheric pressure 100C (strict definition, the triple point of ice 0.01C at a pressure of 6.1 mbar).

The law of conservation of energy tells us that when work and heat energy exchanged net profit or loss of energy. However, the amount of thermal energy that can be converted into work is limited. As heat flows from hot to cold a certain amount of energy can be converted into work and extracted. It can be used to drive a generator, for example.

Minimal amount of work, to drive a refrigerator can be defined in terms of absolute scale of temperature. On Fig. 1.1 shows reversible engine E driving a reversible heat pump P; Q and W represent the flow of heat and work. They are called reversible machine, because they have the highest efficiency that can be seen, and because there is no loss, E and P are identical machines.

Location the results shown in the absence of external effect, because the reservoirs experience no net gain or loss of heat.

If the efficiency of P must be above, i.e. if the work input required for P to raise the same amount of heat Q2 from a cold reservoir should be less than W, the remaining part of W could authority of another heat pump. This may cause additional heat. As a result, net inflow / outflow of heat from a low temperature to high temperature, without any external labour contribution, which is impossible. Relations between Q1, Q2 and W depend only on the temperature of hot and cold water. French physicist Sadi Carnot (1796-1832) was the first to predict that the relationship between the workers and heat depending on temperature and ideal solution for cooling process is known as Carnot. To find the link, the temperature should be defined more carefully. Degrees on the thermometer only an arbitrary zoom ratio.

Kelvin (1824-1907), together with other leading physicists period, concluded that the absolute temperature scale can be defined in terms of efficiency reversible engines.

Perfect " never achievable in practice the ratio of the performance of the calorific power (W/Qj reversible engine E is equal to a Difference of Temperatures (T1 - T0) are divided into the Hot reservoir Temperature (Tj).

P can be any of the refrigeration unit, we have to think and work Kelvin tells us that the minimum work, W, you need to increase the amount of heat Q2 temperature T0 for temperature T1 is available at:

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