Question

A mass of 7 kg undergoes a process during which there is heat transler frorn the mass at a rate of 2 kJ per kg, an elevation decrease of 40 m, and an increase in velocity from 13 m/s to 23 m/s. The specific internal energy decreases by 4 kJ/kg and the acceleration of gravity is constant at 9.7 m/s2. Determine the work for the process, in k.J

Answer 1

Answer:44.61 KJ

Explanation:

Let h_1,V_1,Z_1 be the initial specific enthalpy,velocity&elevation of the system

and h_2,V_2,Z_2 be the Final specific enthalpy,velocity&elevation of the system

mass(m)=7kg

Applying Steady Flow Energy Equation

$m\left [ h_1+\frac{v_1^2}{2g}+gZ_1\right ]$+Q=$\left [ h_2+\frac{v_2^2}{2g}+gZ_2\right ]$+W

$h_1-h_2=4 KJ/kg$

$V_1=13m/s$

$V_2=23m/s$

$Z_1-Z_2=40m$

substituting values

$7\left [ h_1+\frac{13^{2}}{2g}+gZ_1\right ]+7\times2$ = $\left [ h_2+\frac{23^2}{2g}+gZ_2\right ]$+W

W=$7\left [h_1-h_2+\frac{V_1^2-V_2^2}{2000g}+g\frac{\left (Z_1-Z_2 \right )}{1000}\right ]$+Q

W=$7\left [4+\frac{13^2-23^2}{2000g}+g\frac{\left (40 \right )}{1000}[\right ]$+$2\times 7$

W=44.61KJ