Dry air at \(35^{\circ} \mathrm{C}\) and a velocity of \(20 \mathrm{~m} / \mathrm{s}\) flows over a long cylinder of \(25-\mathrm{mm}\) diameter. The cylinder is covered with a thin porous coating saturated with water, and an embedded electrical heater supplies power to maintain the coating surface temperature at \(20^{\circ} \mathrm{C}\).

(a) What is the evaporation rate of water from the cylinder per unit length \((\mathrm{kg} / \mathrm{h} \cdot \mathrm{m})\) ? What electrical power per unit length of the cylinder \((\mathrm{W} / \mathrm{m})\) is required to maintain steady-state conditions?

(b) After a long period of operation, all the water is evaporated from the coating and its surface is dry. For the same free stream conditions and heater power of part (a), estimate the temperature of the surface.