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Unformatted text preview: the inlet and the exit valves to the
radiator are closed. After a while the temperature of the steam
drops to 80°C as a result of heat transfer to the room air. Determine the entropy change of the steam during this process, in
kJ/K. Answer: 0.0806 kJ/K
7–32 A 0.5-m3 rigid tank contains refrigerant-134a initially at
200 kPa and 40 percent quality. Heat is transferred now to the
refrigerant from a source at 35°C until the pressure rises to
400 kPa. Determine (a) the entropy change of the refrigerant,
(b) the entropy change of the heat source, and (c) the total
entropy change for this process.
Answers: (a) 3.873 kJ/K, (b) 3.432 kJ/K, (c) 0.441 kJ/K 7–33 Reconsider Prob. 7–32. Using EES (or other)
software, investigate the effects of the source
temperature and final pressure on the total entropy change for
the process. Let the source temperature vary from 30°C to
210°C, and the final pressure vary from 250 kPa to 500 kPa.
Plot the total entropy change for the process as a function of
the source temperature for final pressures of 250 kPa, 400 kPa,
and 500 kPa, and discuss the re...
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This document was uploaded on 11/28/2012.
- Spring '09