ideal gas, this general result reduces to (cp - cv ) = —, where ^ is the Universal gas constant and M is the molecular mass of the ideal gas, a well-known relationship. It is also possible to show that for an incompressible substance, i.e., liquid water, (cp - cv ) = 0 which says that for those we must just use _c as the specific heat without any subscripts. For those substances for which we have tables, enthalpies must be used and not Ah = cAT, another common mistake in literature, Çengel and Boles (2008). In analyzing other derivatives of interest, these methodologies become very useful as well when we go through those quantities, for
example, (^^j and , and their values for an ideal gas. In Arnas (2000)
these along with other characteristics are further studied. The slope of various functions on the Mollier, an (h-s) diagram, i.e.) — | = JT — vj ——| j, ( — | ,
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