Question

Steam flows through a nozzle at mass flow rate of $\dot{m}=0.1kg/s$ with a heat loss of 5 kW. The enthalpies at inlet and exit are 2500 kJ/kg and 2350 kJ/kg, respectively. Assuming negligible velocity at inlet $C_1\approx 0)$, the velocity $\left(C_2\right)$ of steam (in m/s) at the nozzle exit is (correct to two decimal places).

• A. 447.213

Answer 1

The correct option is A 447.213
$\dot{m}=0.1kg/s,$
$\dot{Q}=5kW\left(heatloss\right)$
Applying SFEE

$\dot{m}(h_1+\frac{1}{2}{C}^{2}1+gz1)+\dot{Q}=\dot{m}(h_2+\frac{1}{2}{C}_2^2+g{z}_2)+{\dot{W}}_{cv}$

$C_1=0and{\dot{W}}_{cv}=0$

$z_1=z_2\left(assume\right)$
$\dot{m}{h}_1+\dot{Q}=\dot{m}{h}_2+\dot{m}\frac{1}{2}{C}_2^2$
$\Rightarrow \dot{m}\times \frac{1}{2}{C}_2^2=\dot{m}(h_1-h_2)+\dot{Q}$
$\Rightarrow 0.1\times \frac{1}{2}{C}_2^2\times {10}^{-3}=0.1(250-2350)-5$

$C_2=447.213m/s$