Air is compressed from 20 psia at 64 degrees fahrenheit to 153 psia in a compres

Question

Air is compressed from 20 psia at 64 degrees fahrenheit to 153 psia in a compressor. The compressor is operated as such that the air tempurature remains constant. Calculate the change in the specific volume of air as it passes through the compressor.

It told me in the 'hints' section to use the ideal gas law, which I did, Pv=RT, I converted the tempurature to rankine, and used the R value of 10.73 ft^3/psiaMolerankine, I kept getting my answer as 244.22ft^3/lbm.

It wants the answer in units of ft^3/lbm, what am I doing wrong?

Explanation / Answer

PV = RT ,: let's consider 1 mol of air

R:10.73 ft^3/psiaMolerankine

64 f = 523.67 *Rankine

20*V = 10.73*523.67

V = 280.9489 ft^3/mol

now when air is compressed keeping T constant,

P1V1= P2V2,

20*280.9489= 153* V2 ,

V2 =36.725 ft^3/mol

specific volume,

v = V/molar mass

molar mass of air ,

M = 28.97,

specific volume , v , =36.725/28.97 = 1.2677 ft63/lbm

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