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Modern Engineering Thermodynamics

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98 CHAPTER 3: Thermodynamic Properties<br />

70. In 1905, Knoblauch, Linde, and Klebe proposed the<br />

following equation for the specific volume of superheated<br />

steam:<br />

v = 0:5962T/p − ð1 + 0:0014pÞð150,300,000/T 3 − 0:0833Þ<br />

where p is in psia, T is in R, and v is in ft 3 /lbm. Develop a<br />

computer program that returns v when p and T are input.<br />

Allow the use of either SI or <strong>Engineering</strong> English units.<br />

Compare your results with steam table values at 0.10, 0.50,<br />

1.00, 1.50, 2.00, 2.50, and 3.00 MPa along the 200.°C<br />

isotherm. Plot these results as a percent error in v vs. p for<br />

T =200.°C.<br />

71. Develop a computer program that calculates the pressure of<br />

superheated ammonia vapor from the Beattie-Bridgeman<br />

equation of state when the specific volume and temperature<br />

are input from the keyboard. Allow the use of either SI or<br />

<strong>Engineering</strong> English units. Using the superheated ammonia<br />

tables (Table C.6), determine the percent error between your<br />

calculated values of pressure and the correct values along the<br />

100.°F isotherm. Plot this percent error vs. p utilizing actual<br />

pressure data of 10.0, 30.0, 50.0, 70.0, 90.0, 140., and<br />

180. psia.<br />

72. The pressure-temperature relation for saturated ammonia can be<br />

written as<br />

logp sat = C 1 − C 2 /T sat − C 3 logðT sat Þ − C 4 T sat + C 5 T 2 sat<br />

where<br />

C 1 = 25:5743247<br />

C 2 = 3295:1254<br />

C 3 = 6:4012471<br />

C 4 = 4:148279 × 10 –4<br />

C 5 = 1:4759945 × 10 –6<br />

In this equation p sat is in psia and T sat is in R. Develop a computer<br />

program that calculates in either SI or <strong>Engineering</strong> English units<br />

(your choice) p sat in either psia or ΚPa when T sat is entered in either<br />

°For°C. Make sure the screen clearly indicates the proper units on<br />

the input information and all output values. Compare the resulting<br />

output values with a series of corresponding saturation values given<br />

in Table C.5 of Thermodynamic Tables to accompany <strong>Modern</strong><br />

<strong>Engineering</strong> <strong>Thermodynamics</strong>.<br />

73. The p-v-T relation for superheated mercury vapor is<br />

pv = RT − ðT/vÞexpð10:3338 − 312:095/T − 2:07951 ln TÞ<br />

where p is in N/m 2 , v is in m 3 /kg, T is in K, and R = 41.45 J/kg · K.<br />

Develop a computer program that outputs p, v, and T with their<br />

appropriate units when either (a) p and T are input or (b) v and<br />

T are input. Allow the user to work in either the SI or <strong>Engineering</strong><br />

English units and to choose which type of input he or she wishes<br />

to use. For extra credit, create an isometric three-dimensional plot<br />

of a p-v-T surface using this equation of state.

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