Tank A ha a volume of 0.15 m^3 and contains dry, saturated water vapor at 200 C.

Question

Tank A ha a volume of 0.15 m^3 and contains dry, saturated water vapor at 200 C. A frictionless piston initially rests at the bottom of cylinder B When the valve is opened, water vapor flows slowly into cylinder B. THe piston mass is such that a pressure of 0.3 MPa in cylinder B is required to raise the piston. THe process ends when the pressure in tank A has fallen to 0.3 MPa. During this process heat transfer with the surroundings keep the temperature of the water on each side always at 200 C. Determine the heat transfer (kJ).

Answer: 483.9 kJ

Consider the process of filling a scuba diving tank with air. The tank is initially at T1 and P1, A large reservoir can supply air at T > T1 and P > P . The scuba tank is connected to the reservoir and quickly filled to P . Assume the filling process is adiabatic. The tank temperature returns to T1 as a result of heat transfer with the surroundings. Assuming air is an ideal gas with constant specific

Explanation / Answer

as temperature of both tanks are same ,there is no change in internal energy i.e dU =0;

=>Q =workdone;

work done =integral(PdV) =integral(nRT*dV/V)

as per standard table P at T=200C is 1554.9kPa

now as T remains constant ,PV is also constant =>nRT =PV =1554900*0.15 =233235J

work done = 233235 ln(V2/V1) =233235*(ln(P1/P2) =233235*1.6453 = 383.7kJ

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