A hollow, porous cylinder \(25 \mathrm{~mm}\) in OD, \(15 \mathrm{~mm}\) in ID, is fed internally with liquid diethyl ether at \(293 \mathrm{~K}\). The ether flows radially outward and evaporates on the outer surface. Pure nitrogen at \(373 \mathrm{~K}\) and \(1 \mathrm{~atm}\) flows perpendicular to the cylinder axis at \(3 \mathrm{~m} / \mathrm{s}\) carrying away the evaporated ether. The ether flow is to be that which will just keep the outer surface of the cylinder wet with liquid. Since mass-transfer rates vary about the periphery, the cylinder will be rotated slowly to keep the surface uniformly wet. Calculate the surface temperature and the rate of ether flow, in \(\mathrm{kg} / \mathrm{h}\) per meter of cylinder length.