A furnace wall consists of 200 mm of refractory fireclay bricks, 100 mm of kaolin brick, and 6 mm of steel plate (mild grade). The fires side of the refractory is at 1150C and the outside of the steel is at 30C. An energy balance show the heat loss from the wall to 300 W/m2. During construction thin layers of air were allowed between the layers of brick and steel. How many millimeters of kaolin insulation were saved by having these layers present? You will need to search for appropriate thermal conductivity values.
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