Energy balance_0902 - Energy Balance Specific property...

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Energy Balance Specific property Amount of a property per unit mass = (Property) / (Amount (Mass, Mole number, …)) Intensive property E.g. Specific volume (m3/Kg), specific internal energy (J/Kg); specific enthalpy (J/mol) Enthalpy H=E i +PV H: enthalpy (J), P: pressure (Pa), V: volume (m 3 ) E i : internal energy (J), depends on composition, state, temperature of the system. Independent of pressure for ideal gases, liquids, solids. PV is called “pressure energy” or “flow work”, representing the work performed on the system in order to insert the fluid Relative value May be expressed as specific enthalpy H’=E i ’+PV’ Where E i is specific internal energy, V’ is specific volume ( V’=V/m=1/ρ ) Reference states E i and H are defined relative to a reference state Often chosen to be 0˚C at 1 atm We are only interested in how much the internal energy or enthalpy changes Energy balance on closed systems E i : Internal E;
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Energy balance_0902 - Energy Balance Specific property...

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