Evaluation of downstream enthalpies following isentropic and

5 Evaluation of downstream enthalpies following isentropic and frictionally resisted expansions 

We begin by developing a mathematical formula for the change in specific entropy over the expansion from general thermodynamic relationships. We will then consider how the resulting equation may be solved for the three cases of 

From equation (3.4) in Section 3.2, the change in specific entropy is given in terms of a heat increment, dq, added to a system at temperature, T  

Since specific enthalpy is given by equation (3.6) as h = u + pv, i follows that 

Further, from the definition of specific heat at constant pressure (equation 3.18), we have  

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