課程名稱︰熱力學 Thermodynamics
課程性質︰大二必修
課程教師︰馬小康教授
開課系所︰機械系
考試時間︰12/2 2004
試題
（18％）（1）A 12-kg iron block initially at 350℃ is quenched in an insulted
tank that contains 100kg of water at 22℃. Assuming the water that vaporizes
during the process condenses back in the tank, determine the total entropy change
during this process.（The specific heat of water at 25℃ is Cp＝4.18kJ/kg℃
The specific heat of iron at 25℃ is Cp＝0.45J/kg℃ ）
（20％）（2）An ideal gas with constant heat capacities undergoes the reversible cycle
shown. The processes making up the cycle are：
1-2 is a constant volume process
2-3 is an isothermal process
3-4 is an adiabatic process
4-1 is a constant pressure process
Please （a）plot the P-V and T-S diagrams,（b）state as many thing as you
Can about ∮dQ, ∮dU and ∮dW, for the cycle, （c）state the cycle
efficiency, （d）the entropy generation.
（15％）（3）An insulted rigid tank is divided into two equal parts by partition.
Initially, one part contains 5 kmol of ideal gas at 400kPa and 50℃, and
The other side is evacuated. The partition is now removed, and the gas fills
the entire tank. Determine the total entropy change during this process.
（Ru=8.314kJ/kmol K）
（15％）（4）Consider two Carnot heat engines operating in series. The first engine
receives heat from the reservoir at 2400K and reject the waste heat to
another reservoir at temperature T. The second engine receives this energy
rejected by the first one, converts some of it to work, and rejects the rest
to a reservoir at 300K. If the thermal efficiencies of both engines are the same,
determine the temperature T.
（12％）（5）Please explain the following terms：
a. Carnot refrigerator
b. Clausius statement of second law
c. Turbine efficiency
d. Coefficient of performance for heat pump
（20％）（6）A heat pump is used to maintain a house at 22℃ by extracting heat from
the outside air on a day when the outside air temperature is 2℃. The house is
estimated to lose heat at a rate of 110000kJ/h, and the heat pump consumes
8kW of electric power when running. Is this heat pump powerful enough to
do the job？
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