Question

mcq

A boiler which produces water vapour at atmospheric pressure, has a 2 cm thick , 500 cm²bottom, which is made up of a metal whose K= 400 Wm^{-1 0}C^-1. A heating coil of 20 kW supplies heat to the boiler. If no heat is lost to the outside and the latent heat of vaporisation L=2.3 x 10⁶ Jkg^-1, find the maximum rate of production of water vapour in kgs^-1?

(1) 3.07 x 10^-1 (2) 8.7 x 10^-3 (3) 4.2 x 10^-2 (4) 8.7 x 10^-4 (5) 2.3 10^-3

need a detailed answer

Answer 1

See for maximum water vapour production the condition is that the

Total heat produced by coil= heat absorbed by water

If water vapour production rate is m then

m× heat of vaporization= heat produced by coil

m×2.3×10⁶= 20×10³. (1 KW= 1000 W)

m=8.7×10^-3 kg/s

Answer is option 2.