# Equation 76 is particularly useful for determining

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Unformatted text preview: le process. Equation 7–6 is particularly useful for determining the entropy changes of thermal energy reservoirs that can absorb or supply heat indefinitely at a constant temperature. Notice that the entropy change of a system during an internally reversible isothermal process can be positive or negative, depending on the direction of heat transfer. Heat transfer to a system will increase the entropy of a system, whereas heat transfer from a system will decrease it. In fact, losing heat is the only way the entropy of a system can be decreased. EXAMPLE 7–1 Entropy Change during an Isothermal Process A piston-cylinder device contains a liquid–vapor mixture of water at 300 K. During a constant-pressure process, 750 kJ of heat is transferred to the water. As a result, part of the liquid in the cylinder vaporizes. Determine the entropy change of the water during this process. T = 300 K = const. SOLUTION We take the entire water (liquid ∆Ssys = vapor) in the cylinder as the system (Fig. 7–4). This is a closed system since no mass crosses the system boundary...
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## This document was uploaded on 11/28/2012.

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