Question

In an industrial process $10kg$ of water per hour is to be heated from ${20}^{\circ }C$ to ${80}^{\circ }C$. To do this, steam at ${150}^{\circ }C$ is passed from a boiler into a copper coil immersed in water. The steam condenses in the coil and is returned to the boiler as water at ${90}^{\circ }C$. How many kilograms of steam is required per hour (specific heat of steam $=1cal/g^{\circ }C$, latent heat of vapourization $=540cal/g$)?

• A. $1g$
• B. $1kg$
• C. $10g$
• D. $10kg$

Answer 1

Answer: (B)

$1kg$

Heat released by steam= heat absorbed by water
Let the amount of steam required be $mkg$

Heat released by steam causes following changes
$Steam\left(423K\right)\to steam\left(373K\right)\to water\left(373K\right)\to water\left(363K\right)$

Then, $1000m(1\times 50+540+1\times 10)=10000\times 1\times 60$
$\Rightarrow m=1$
Hence amount steam required per hour is $1kg$.