The pressure of air is maintained constant during

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Unformatted text preview: rmal equilibrium is established after a while as a result of heat transfer between the blocks and the lake water. Determine the total entropy change for this process. FIGURE P7–62 IRON 50 kg LAKE 15°C COPPER 20 kg FIGURE P7–53 Entropy Change of Ideal Gases 7–54C Prove that the two relations for entropy change of ideal gases under the constant-specific-heat assumption (Eqs. 7–33 and 7–34) are equivalent. 7–63 An insulated piston-cylinder device initially contains 300 L of air at 120 kPa and 17°C. Air is now heated for 15 min by a 200-W resistance heater placed inside the cylinder. The pressure of air is maintained constant during this process. Determine the entropy change of air, assuming (a) constant specific heats and (b) variable specific heats. 7–64 A piston-cylinder device contains 1.2 kg of nitrogen gas at 120 kPa and 27°C. The gas is now compressed slowly in a polytropic process during which PV 1.3 constant. The process ends when the volume is reduced by one-half. Determine the entropy change of nitrogen during this pro...
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This document was uploaded on 11/28/2012.

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