Consider a 1m3 rigid vessel A It has got a valve on top with

Consider a 1m³ rigid vessel A. It has got a valve on top with a cross sectional area of A = 6 cm² with a pressure of 100kPa outside and a pressure of P_A1 = 200 kPa inside.

(a) Find the force needed to open the valve if the area of the rod is ignored.

Consider now also the frictionless piston/cylinder arrangement, B, which is connected to vessel A by a pipe line and a valve. Initially both contain water, with A having saturated vapor and B at 400 degree celsius, 300 kPa and 1m³. If we keep the top valve in vessel A closed and we open the valve that connects A and B, the water in both A and B slowly comes to a uniform state.

(b) Find the initail mas in A and B.
(c) If the process results in T₂ = 200 degree Celsius, find the heat transfer ₁Q₂ and ₁W₂ to or from the water.

Solution

a) Force required to open the valve = PxA = (200kPa-100kPa) x 6x10^-4 m² = 6 x 10^-2 kN = 60 N