In an industrial process 10 kg of water per hour is to be heated from `20^@C` to `80^@C`. To do this steam at `150^@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^@C`. How many kilograms of steam is required per hour (specific heat of steam`=1 cal//g^@C`, Latent heat of vapourization`=540 cal//g`)?

Answer

`1`kg

Explanation

Let m = mass of steam required per hour Heat needed = `(10 xx 1000kg) xx (1"cal"//g) xx (80-20)`
=`60xx 10^(4)"cal//hour"`
Heat supplied = `m xx1 xx(150-100) + m xx540 + m xx 1 xx(100-90)`
Heat needed = Heat supplied
`implies 60 xx 10^(4) = 600m = 1000gm = 1` kg