Heat
Heat is one of many forms of energy and formed from the chemical sources. The warmth of his body heat or internal energy, and the change in this energy could show how the temperature changes or changes between solid, liquid and gaseous States.
The matter may also have other forms of energy, potential or kinetic, depending on the pressure, position and movement. Enthalpy is the sum of the internal energy and the flow of work and is given by:
H = u + Pv
In the process, where there is a constant flow factor Pv will not change significantly, and the difference in enthalpy is the amount of heat gained or lost.
Enthalpy can be expressed total above absolute zero, or any other basis, that it is comfortable. Tabulated enthalpy in manual work is often shown above, reference temperature from -40C, as this is also -40 old Fahrenheit scale. In any calculation, the basic condition should always be checked to avoid errors that will occur if two different databases are used.
If the enthalpy change is felt as temperature change, it is called sensible heat.
It is expressed as specific heat capacity, i.e. the enthalpy change in the degree of temperature change, kJ/(kg). If there is no temperature change, but a change of state (solid-liquid, liquid-gas, or Vice versa), it is called latent heat. This is expressed in kJ/kg, but it depends on the temperature of boiling, and therefore, as a rule, qualified for this condition. As a result of overall changes can be shown on the temperature and enthalpy diagram (Fig. 1.3).
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Fundamentals 