Liquid water at 60 bar and 250C passes through an adiabatic expansion valve, emerging at

Chapter 7, Problem 7.40

(choose chapter or problem)

Liquid water at 60 bar and \(250^{\circ} \mathrm{C}\) passes through an adiabatic expansion valve, emerging at a pressure \(P_{\mathrm{f}}\) and temperature \(T_{\mathrm{f}}\). If \(P_{\mathrm{f}}\) is low enough, some of the liquid evaporates.

(a) If \(P_{f}=1.0\) bar, determine the temperature of the final mixture \(\left(T_{\mathrm{f}}\right)\) and the fraction of the liquid feed that evaporates \(\left(y_{v}\right)\) by writing an energy balance about the valve and neglecting \(\Delta \dot{E}_{\mathrm{k}}\).

(b) If you took \(\Delta \dot{E}_{\mathrm{k}}\) into account in Part (a), how would the calculated outlet temperature compare with the value you determined? What about the calculated value of \(y_{\mathrm{v}}\)? Explain.

(c) What is the value of \(P_{\mathrm{f}}\) above which no evaporation would occur?

(d) Sketch the shapes of plots of \(T_{\mathrm{f}}\) versus \(P_{\mathrm{f}}\) and \(y_{\mathrm{v}}\) versus \(P_{\mathrm{f}}\) for \(1 \text { bar } \leq P_{\mathrm{f}} \leq 60 \text { bar. }\) Briefly explain your seasoning.