solve for e and f 1. 7 kg of water in a piston-cylinder is expanded by heating f

Question

solve for e and f

1. 7 kg of water in a piston-cylinder is expanded by heating from Pi - 5,000KPa (abs) and quality x = 0.6 to T-400°C in a constant pressure process. The piston-cylinder is stationary in place. Answer the followings. (You must mention the source/table of your data) a) Draw the T-v diagram or the process b) What is the initial temperature? c) What are initial and final specific volumes? d) What are initial and final specific internal energies? e) What is the work done during the process? f) What is the heat transfer for the process?

Explanation / Answer

c and d)

Given

State-1

P1 = 5 MPa and x = 0.6

Note the saturation properties at P1 = 5 MPa

Tsat = 264

vf = 0.001286 and vg = 0.03944 (units : m3/kg)

uf = 1148 and ug = 2597 (units: kJ/kg)

Now at x = 0.6

v1 = (1-x)*vf + x*vg

v1 = 0.02418 m3/kg

u1 = 2017 kJ/kg

State-2

Given

P2 = 5 MPa and T2 = 400 C

since T2 > Tsat, the final state is in supeheated region

so the properties are

v2 =0.05781 m3/kg

u2 = 2907 kJ/kg

e) since it is constant pressure process

W = m*P*(v2-v1)

W = 7*5*1000*(0.05781-0.02418)

W = 1177.05 kJ

f)

dU = m*(u2-u1) = 7*( 2907-2017 )

dU = 6230 kJ

From first law

dQ = dU + W

dQ = 6230 + 1177.05

dQ = 7407.05 kJ

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