Question

10.00 points 1 out of 3 attempts Assist Round your final answers to one decimal place. A piston-cylinder device contains 1.340 kg of saturated water vapor at 200°C. Heat is now transferred to steam, and the steam expands reversibly and isothermally to a final pressure of 800 kPa. Determine the heat transferred and the work done during this process. k.J k.J

Answer 1

Given that, T= 200⁰C = 200 + 273.15 = 473.15 K

and m = 1.340 kg

Process is isothermal ans reversible

Thus, $\Delta$S = q/T

Where T = 200^oC

But q = Tm(s₂-s₁)

Where s₂ and S₁ are the entropies at final and initial stages.

also From First Law of thermodynamics, $\Delta$U = q-W

W = Q - $\Delta$U = q - m(u₂ -u₁)

Where u₂ and u₁ are the internal energies at final and initial stages respectively

Initially, we have T = 200^oC

and from literature, s₁ = 6.4302 kJ/kg. K and u₁ = 2594.2 kJ/kg

At final stage, P = 800 kPa and T = 200^oC

s₂ = 6.8177 kJ/kg. K and u₂ = 2631.1 kJ/kg

Thus, Q = Tm(s₂-s₁) = 473.15K *1.340 kg ( 6.8177 - 6.4302) kJ/kg. K = 245.7 kJ = 246 kJ

W = Q - m(u₂ -u₁) = 246 kJ - (1.340 kg)(2631.1 kJ/kg - 2594.2 kJ/kg) = 196 kJ