301 HW_5_Solution

301 HW_5_Solution - 1 MAE 301 Engineering Thermodynamics...

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Unformatted text preview: 1 MAE 301: Engineering Thermodynamics Spring 2010 HOMEWORK #5 ( Solutions ) Problem 1. Problem 4.61 from the book. Solution: The gas constant of neon is R = 0.4119 kJ/kg ⋅ K and the constant-pressure specific heat of neon is 1.0299 kJ/kg ⋅ K (Table A-2 a ). At the compressor inlet, the specific volume is /kg m 207 . 1 kPa 100 K) 273 K)(20 /kg m kPa (0.4119 3 3 1 1 = + ⋅ ⋅ = = P RT v Similarly, at the compressor exit, /kg m 2414 . kPa 500 K) 273 K)(20 /kg m kPa (0.4119 3 3 2 2 = + ⋅ ⋅ = = P RT v The change in the specific volume caused by the compressor is /kg m 0.966 3 − = − = = Δ 207 . 1 2414 . 1 2 v- v v Since the process is isothermal, kJ/kg = Δ = Δ T c h p Problem 2. Problem 4.68E from the book. Solution: Air is an ideal gas since it is at a high temperature and low pressure relative to its critical point values of − 221.5 ° F and 547 psia. The kinetic and potential energy changes are negligible, pe ke ≅ Δ ≅ Δ . Constant specific heats at room temperature can be used for air. This assumption results in negligible error in heating and air-conditioning applications. The tank is insulated and thus heat transfer is negligible. We take the entire tank as the system. This is a closed system since no mass crosses the boundaries of the system. The energy balance for this system can be expressed as ) ( 1 2 energies etc. potential, kinetic, internal, in Change system mass and work, heat, by nsfer energy tra Net T T mc U E E E out in − = Δ = Δ = − v 3 2 1 43 42 1 Since the internal energy does not change, the temperature of the air will also not change. Applying the ideal gas equation gives psia 50 = = = = = ⎯→ ⎯ = 2 psia 100 2 2 / 1 2 2 1 2 1 1 2 2 2 1 1 P P P P P P V V V V V V 2 Problem 3. Problem 4.74 from the book. Problem 4....
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This note was uploaded on 05/19/2010 for the course MAE 301 taught by Professor Hassan during the Spring '08 term at N.C. State.

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301 HW_5_Solution - 1 MAE 301 Engineering Thermodynamics...

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