Question

A blower handles 1 kg/s of air at ${20}^o$C and consumes a power of 15 kW. The inlet and outlet velocities are 100 m/ s and 150 m/ s respectively. The exit air temperature, assuming adiabatic conditions is ________${}^{o}C$

(Take $c_p$ of air as 1.005 kJ/ kgK

• A. ${28.70}^{\circ }C$
• B. ${23.70}^{\circ }C$
• C. ${58.50}^{\circ }C$
• D. ${18.90}^{\circ }C$

Answer 1

The correct option is A ${28.70}^{\circ }C$

Given, $m=1kg/s,T_1={20}^{o}C,W=-15kW,V_1=100m/s,V_2=150m/s,c_p=1.005kJ/kgK$

Using SFEE, $\dot{m}(h_1+\frac{V_1^2}{2000})=\dot{m}(h_2+\frac{V_2^2}{2000})+W$

So, $\dot{m}{c}_p(T_1-T_2)+\frac{\dot{m}}{2000}(V_1^2-V_2^2)=W$

$1\times 1.005(293-T_2)+\frac{{100}^2-{150}^2}{2000}=-15$

$\therefore$ $T_2=293+8.70=301.70K={28.70}^{o}C$