Q2: A layer of 2.5 in thick firebrick (kb = 1.0 Btu/hr ft °F) is placed between two % in.- thick steel plates (ks = 30 Btu/hr ft °F). The faces of the brick adjacent to the plates are rough, having...

Extracted text: Q2: A layer of 2.5 in thick firebrick (kb = 1.0 Btu/hr ft °F) is placed between two % in.- thick steel plates (ks = 30 Btu/hr ft °F). The faces of the brick adjacent to the plates are rough, having solid-to-solid contact over only 35 % of the total area, with the average height of asperities being L2-2/32 in. If the surface temperatures of the steel plates are 250° and 800°F, respectively. The conductivity of air ka is 0.02 Btu/hr ft °F, determine the rate of heat flow per unit area.