Q7. A furnace wall is made from 10 mm thick steel plate lined internally with refractory 100 mm thick. The external surface is a sheet steel casing, creating a 200 mm wide air gap. A 40 % reduction in heat loss is to be achieved by insulating the external side of the furnace wall, while the position of the steel casing remains unchanged.
The internal surface temperature of the refractory is 1800℃ and the temperature of the surroundings remains constant at 25℃.
The effect of the sheet steel casing may be ignored.
(a) Calculate EACH of the following:
(i) The rate of heat loss per m2 without insulation; (4)
(ii) The required thickness of insulation;(5)
(iii) The temperature drop across the final air gap. (4)
(b) Sketch the thermal gradient across the insulated wall showing the interface temperature. (3)
Note: thermal conductivity of the refractory = 0.31 W/mK
thermal conductivity of steel = 55 W/mK
thermal conductivity of air = 0.04 W/mK
thermal conductivity of insulation = 0.023 W/mK
outer surface heat transfer coefficient = 11 W/m2K
Please buy a membership plan and login via our app to view answers.
Download our App
