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Unformatted text preview: rk is not zero. (It is a good thing that it is
not. Otherwise, heat engines that work on a cycle such as steam power plants
would produce zero net work.) Neither is the cyclic integral of heat.
Now consider the volume occupied by a gas in a piston-cylinder device
undergoing a cycle, as shown in Fig. 7–2. When the piston returns to its initial
position at the end of a cycle, the volume of the gas also returns to its initial
value. Thus the net change in volume during a cycle is zero. This is also expressed as
dV 0 (7–3) That is, the cyclic integral of volume (or any other property) is zero. Conversely, a quantity whose cyclic integral is zero depends on the state only 1 m3 3 m3 1 m3 ∫ dV = ∆V cycle =0 FIGURE 7–2
The net change in volume (a property)
during a cycle is always zero. cen54261_ch07.qxd 11/18/03 9:57 AM Page 276 276
FUNDAMENTALS OF THERMAL-FLUID SCIENCES and not the process path, and thus it is a property. Therefore, the quantity
(dQ/T)int rev must represent a property in the diff...
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This document was uploaded on 11/28/2012.
- Spring '09