i have a piston cylinder device with a total height of 4.5 cm at the stops. from

Question

i have a piston cylinder device with a total height of 4.5 cm at the stops. from 0 to 1cm is the initial quality of the mixture. The piston is 10 cm in diameter with a mass of 40 kg. A  

water-vapor mixture is contained in a piston-cylinder device fitted with stops. The initial quality of the

mixture is 0.25 (25%). The mixture is heated until the piston hits the stops. Then heating continues until the

pressure is 400 kPa. The pressure due to the piston is 100 kPa and the atmospheric pressure is 100 kPa. how do i find the volume? How do i find the mass of the water vapor mixture? how do i find the total work and heat transfer of both? sketch a pv diagram.

Explanation / Answer

let P = pressure when piston hits the top

A = cross sectional area of piston = pi* 0.5^2 = 0.78 m^2

F = total force on piston

   = Mg + 100*10^3 *A*g - P*g*A

F   =0

Mg + 100*10^3 *A*g - P*g*A   =0

   P   = 100 k Pa

V = volume = A*0.1 = 0.078 m^3

   Work done = P*dV = 100*10^3 ( 0.078 -0.0078) = 7800  

mi = initial mass of water vapour = 25

   Mass of water vapour = 4*18* P*V/(RT) = 4*18*10^5/(0.082*373)

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