In a industrical 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 coilo immersed in water. The steam condenses in the coil and is returned to the boiler as water at `90^(@)C`, how many kg of steam is required per hour . ltb rgt (Specific heat of steam = `1 cal per g^(@)C`, latent heat of vaporisation = `540 cal g^(-1)`)

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