# 7327919 - the thermodynamic property table for propane we...

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Efficiency for a centrifugal compressor for any polytropic process is given by: Polytropic efficiency = = - ηpol wpolwact PiPevdPhe hi where, wpol is the polytropic work of compression And, wact is the actual work of compression. For any polytropic compression process following = Pvn C = = - - - wpol PiPevdP nn 1PiviPePin 1 n 1 Now, For a real gas like in this case propane, Polytropic efficiency can be directly calculated using the equation: = - - ηpol nn 1k 1k ....................................................................................... [1] Where, n is the index of compression which can be calculated using = Pivin Peven For this, we need to know the pressure, P and specific volume, v at the inlet and outlet of the compressor. The pressure and temperature at inlet and outlet can be measured and using
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Unformatted text preview: the thermodynamic property table for propane, we can obtain the value of specific volumes. Engineering units (SI) for pressures & Pe Pi is , Pascal Pa for specific volumes, & ve vi is / m3 kg ** Subscripts ‘e’ for exit and ‘i’ for inlet. And, k is the isentropic index of compression which can be calculated using = k CpCv Value of k in general cases is taken as 1.4. Engineering units (SI) for specific heat at constant pressure, Cp is kJkgK specific heat at constant volume, Cv is kJkgK specific enthalpy at exit, he is / kJ kg specific enthalpy at inlet, hi is / kJ kg Using equation [1] we can obtain the polytropic efficiency for this case....
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