Problem 1.60 of fundamentals of heat and mass transfer. enhanced etext, 8th edition, by theodore l. bergman; adrienne s. lavine: frank p. incropera: david p. the diameter and surface emissivity of an electrically heated plate are d = 300 mm and c = 0.80, respectively. tood ca d=6,3m (a) estimate the power needed to maintain a surface temperature of 200°c in a room for which the air and the walls are at 25°c. the coefficient characterizing heat transfer by natural convection depends on the surface temperature and, in units of w/ m k, may be approximated by an expression of the form h = 0.80(ts - too) (b) assess the effect of surface temperature on the power requirement, as well as on the relative contributions of convection and radiation to heat transfer from the surface.