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steam_0912 - STEAM TABLES REVIEW OF DEFINITIONS AND UNITS...

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STEAM TABLES REVIEW OF DEFINITIONS AND UNITS Specific volume ( V’) V’=V/m=1/ρ . Unit: m 3 /kg Internal energy ( E i ) Internal energy is the sum of the kinetic energy due to molecular motion and potential energy intermolecular attractive (or repulsive) forces. Enthalpy and specific Enthalpy Enthalpy is a measure of the quantity of energy contained in a thermodynamic system. H = E i + p V Internal energy (U), enthalpy (H), work (W), and heat (Q) are all measured in kJ. Specific enthalpy ( H’ ) is the enthalpy contained in one kg of a substance. Unit: kJ/kg H = m H’ Sensible and latent Heat Sensible heat causes a temperature change but the body does not change its phase. Q= m. c p . (T fin -T in ) C p : specific heat capacity, the amount of heat required for 1 kg of a given material to rise temperature by 1°C. (or heat released to decrease temperature by 1 °C). Unit: kJ/kg °C. Q is positive when the body is gaining energy and negative when the body is losing energy through heat transfer. Latent heat specifies the amount of heat needed to cause a given change of state of 1 kg of a given material with no change in its temperature. It is further divided into latent heat of boiling (or vapourization) and latent heat of melting (or freezing). Unit: kJ/kg, Q= m. H latent Latent heat is positive when it is supplied to the body (melting and boiling), and negative
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steam_0912 - STEAM TABLES REVIEW OF DEFINITIONS AND UNITS...

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