Free-convection heat loss from a vertical surface, a small heating panel consists essentially of a flat, vertical, rectangular surface 30 cm high and 50 cm wide. Estimate the total rate of heat loss from one side of this panel by free convection, if the panel surface is at 150°F, and the surrounding air is at 70°F and 1 atm. Use the value C = 0.548 of Lorenz in Eq. 11.4-51 and the value of C recommended by Whitaker, and compare the results of the two calculations.