Question

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Required information NOTE: This is a multi-part question. Once an answer is submitted, you will be unable to return to this part A piston-cylinder device initially contains 15 ft of helium gas at 25 psia and 70'F. Helium is now compressed in a polytropic process (PV" = constant) to 70 psia and 300°F. Use data from tables. Determine the entropy change of helium. (You must provide an answer before moving on to the next part.) The entropy change of the helium is 0.1001

Answer 1

Given Initial condition V = 15 ft² P,= 25psia Ti = 70F final condition P = 70 psia, To = 300°F soil for Helium Cp= 1.25 Btu/lom > R= Cp - Cu = 1.25-0-75 C: 0.75 Btu lebom °F 0.5 Btullant using perfect Gias equation Pivi MRT, nx 0.5x 700 25 X 15 - m=10.71 lb change in Entropy is given by 3-5) = (as)= m [Gen 1) - Ren ()] [1:25 = 10.71 25 en 300 70 200 0.5 er/ro .) S ng 5 = As = 13.97 Btu OF