94932/assignments/4401092 TER VERSIon ASSIGNMENT RESOURCES Problem 3.051 SI Refe

Question

94932/assignments/4401092 TER VERSIon ASSIGNMENT RESOURCES Problem 3.051 SI Referring to the figure shown below, water contained in a piston-cylinder assembly, initially at 1.5 bar and a quality of 60%, is heated at constant pressure until the piston hits the stops. Heating then continues until the water is saturated vapor. The initial height, L1, is 0.0s m and the change in height, Lz, is 0.03 m. ns Water Pa “ 1.5 hur rn For the overall process of the water, evaluate the work and heat transfer, each in k) Kinetic and potential effects are negligible. Part A

Explanation / Answer

Since the process is undergoing in the constant pressure, therefore, the work done for this isobaric process is

W = p(V1 - V2) , since the volume of the gas is proportional to the height of the piston, if the volume of the gas is large, the height of the piston will be more and if the volume of the gas is low therefore, the height of the piaton will be less, therefore, the equation reduces to

W = p(L1 - L2)

W = 1.5( 0.05 - 0.03) = 1.5 x 0.02 = 30/1000 = 0.03 kJ/kg

For a gas of mass of 1kg, the heat transfer is Q = mp(delta L), where m is the mass of the gas, p is the pressure since the specific heat at constant pressure is not given and delta L is the change in height equivalent to volume of the gas, therefore,

Q = 1 x 1.5 x 0.02 = 0.03 kJ/kg, both of the these values are same, which means that work done by the gas is equal to the heat transfer.  

  

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