The hot water needs of a household are to be met by
heating water at 558F to 2008F by a parabolic solar collector at
a rate of 4 lbm/s. Water flows through a 1.25-in-diameter thin
aluminum tube whose outer surface is blackanodized in order
to maximize its solar absorption ability. The centerline of the
tube coincides with the focal line of the collector, and a glass
sleeve is placed outside the tube to minimize the heat losses. If
solar energy is transferred to water at a net rate of 350 Btu/h per
ft length of the tube, determine the required length of the parabolic
collector to meet the hot water requirements of this house.
Also, determine the surface temperature of the tube at the exit.