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Unformatted text preview: 1214 The validity of the last Maxwell relation for refrigerant134a at a specified state is to be verified. Analysis We do not have exact analytical property relations for refrigerant134a, and thus we need to replace the differential quantities in the last Maxwell relation with the corresponding finite quantities. Using property values from the tables about the specified state, s ? v = P T T P
? s v  P T =80C T P =1200 kPa s1400 kPa  s1000 kPa (1400  1000) kPa ? v 100C  v 60C  (100  60 ) C T =80C P =1200kPa (1.0056  1.0458)kJ/kg K ? (0.022442  0.018404)m 3 /kg  (1400  1000)kPa (100  60)C  1.005 10  4 m 3 /kg K 1.0095 10  4 m 3 /kg K since kJ kPam, and K C for temperature differences. Thus the last Maxwell relation is satisfied. 1217 Using the Maxwell relations, a relation for (s/P)T for a gas whose equation of state is P(vb) = RT is to be obtained. Analysis This equation of state can be expressed as v = R v = T P P From the fourth Maxwell relation, R s v =  = P T T P P 1219 Using the Maxwell relations and the idealgas equation of state, a relation for (s/v)T for an ideal gas is to be obtained. Analysis The ideal gas equation of state can be expressed as P = R P = T v v From the third Maxwell relation, R s P = = v T T v v RT . Then, v RT + b . Then, P ...
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This note was uploaded on 04/08/2008 for the course MECH 216 taught by Professor Beninati during the Spring '08 term at Bucknell.
 Spring '08
 Beninati

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