Question

An engine is producing $3000W$ of heat. To keep it cool, a coolant is circulated in the engine which enters the engine at a temperature of ${30}^{\circ }$ and leaves at $50{}^{\circ }C$. If the specific heat of the coolant is $6000J/\left(kg\text{-}K\right)$, then rate of coolant entering engine so that temperature of engine remains constant is

• A. 3 kg/min
• B. 2 kg/min
• C. 2.5 kg/min
• D. 1.5 kg/min

Answer 1

The correct option is D 1.5 kg/min

Given,
$\frac{\Delta Q}{\Delta t}=3000J/s$

Where,
$\Delta Q=ms\Delta \theta =m\times 6000\times 20$
$20\times 6000\frac{m}{t}=3000\Rightarrow \frac{m}{t}=\frac{3000}{6000\times 20}kg/sec$

or $\frac{m}{t}=\frac{3000\times 60}{6000\times 20}kg/min=1.5kg/min$