hw_w7 - EML 5104 Classical Thermodynamics, Spring...

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Unformatted text preview: EML 5104 Classical Thermodynamics, Spring 2010 Use as cover sheet Name (Print): ___________________________________ UF ­ID: ___________________________________ Homework Week 7 Due Feb 22 at the begin of class P1: Steam enters a turbine operating at steady state at 6 MPa, 500 °C with a mass flow rate of 400 kg/s. Saturated vapor exits at 8 kPa. Heat transfer from the turbine to its surroundings takes place at a rate of 8 MW at an average surface temperature of 180 °C. Kinetic and potential energy effects are negligible. a) For a control volume enclosing the turbine, determine the power developed and the rate of exergy destruction each in MW. b) If the turbine is located in a facility where the ambient temperature is 27 °C, determine the rate of exergy destruction for an enlarged control volume that includes the turbine and its immediate surroundings so the heat transfer takes place from the control volume at the ambient temperature. Explain why the exergy destruction values of parts (a) and (b) differ. P2: Estimate the pressure of water vapor at a temperature of 500 °C and a density of 24 kg/m3 using the a) Steam tables. b) compressibility chart. c) Redlich-Kwong equation. d) van der Waals equation. e) ideal gas equation of state. P3: For water the critical properties are: Tc= 647.3 K, pc= 220.9 bar, Zc = (pcvc)/(RTc). Use a computer program (Matlab, Excel, Gnuplot, or others) to plot Tr = 0.25, Tr = 0.5, Tr = 1, Tr = 2, Tr = 4 isotherms for vr = 0.1 to 4 in the p ­v diagram based on a) the van der Waals EOS. b) the Redlich-Kwong EOS. Also plot the saturated liquid and saturated vapor lines as taken from the steam tables. What do you observe? P4: Using p ­v ­T data for saturated water from the steam tables calculate at 50 °C a) hg-hf b ) u g -u f c) s g -s f P5: Develop expressions for the specific enthalpy, internal energy, and entropy change [h(v2,T) ­h(v1,T), (u(v2,T) ­u(v1,T)), (s(v2,T) ­s(v1,T))], using the a) Van der Waals equation of state. b) Redlich-Kwong equation of state. ...
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