Problem $15$: A piston$/$cylinder device contains $2$ kg of liquid water at $20C$ and $100$ kPa $.$ The water is then heated to $300C$ by a source at $500C.$ A pressure of $1$ MPa will lift the piston off the rests. Note: for the internal energy, enthalpy and entropy of compressed water at pressures less than $2\mathrm{.}5$ MPa we can use the properties of saturated liquid water at the system temperature as a close approximation.

a$)$ Sketch a $P-v$ diagram of the process.

b$)$ Determine the final volume.

c$)$ Calculate the work done.

d$)$ Calculate the heat transferred.

e$)$ Calculate the total entropy generation.

Problem $16$: A well$-$insulated heat exchanger has one line with $2k\frac{g}{s}$ of air at $125$ kPa and $1000$ K entering, and leaving at $100$ kPa and $400K.,m_{\text{w}\text{a}\text{t}\text{e}\text{r}}^{}=0\mathrm{.}5k\frac{g}{s}$ The other line has $0\mathrm{.}5k\frac{g}{s}$ water entering at $200$ kPa and $20C,$ and leaving at $200$ kPa $.$ Calculate the exit

$P_3=200$kPa

$T_3=20C$

$n_{\text{w}\text{a}\text{t}\text{e}\text{r}}^{}=0\mathrm{.}5k\frac{g}{s}$

$P_4=200$kPa

$T_4=$

$m_{\text{a}\text{i}\text{r}}=2k\frac{g}{s}$

$P_2=100$kPa

$T_2=400K$

Solutions:$-$

$15)$

b$)0\mathrm{.}516$ m$^3$

C$)514\mathrm{.}0$ Kj

D$)5933\mathrm{.}5$ Kj

E$)5\mathrm{.}98$ Kj$/$k

$16)$

$120\mathrm{.}21$ C

$1\mathrm{.}507$ Kw$/$k

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