Boiler basic knowledge
Enthalpy
The total heat content of the substance comprises three components namely, heat of water or Sensible Heat, heat of evaporation or Latent Heat and superheat – the additional heat imparted to the dry saturated steam to make it superheated called Super Heat. It is also known as enthalpy of water, enthalpy of superheated steam
Enthalpy of Water:
The amount of heat absorbed by one kilogram of water being heated from the freezing point (0 Degree C) to the boiling point is known as the Enthalpy of the Saturated Water (sensible heat of water). It is denoted by the symbol ‘h’.
Sensible heat of 1 kg of water at 0 Degree C is zero and sensible heat of 1 kg of water at
100 Degree C is 4.187 x 100 = 418.7 kJ/kg.
Enthalpy of Evaporation:
The enthalpy of evaporation (or Latent heat) is defined as the amount of heat required to convert one kilogram of water at the saturation temperature tsat corresponding to its pressure into steam at the same temperature and pressure. Latent heat varies with the pressure. Its value decrease with increase of pressure. Its value at 1 bar absolute pressure is 2258 kJ/kg. Value of Latent heat corresponding to any pressure can be directly obtained from the steam tables.
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