Radiation losses from the separator, at boiling
temperatures up to 130° F, were negligible. At
higher temperatures, especially at 212° F, these heat
losses may be significant. When the evaporator was
operated at atmospheric pressure, a film of condensate
could be seen falling down the glass walls of
the separator. The following calculation gives an
idea of the possible radiation losses at 212° F:
Assume room temperature, 82° F. Temperature
difference between separator and room, 130° F.
Surface of the separator, 9.2 square feet. Combined
radiation and convection heat transfer
coefficient (6), 2.4 Btu/hr.sq.ft.°F. Heat losses are
equal to 2.4 x 9.2 x 130 = 2,850 Btu/hr. For a
mean evaporation rate of water of 100 lb./hr., the
radiation losses at 212° F are 2.85 per cent.
Therefore, a correction of 3 per cent was made in
calculating the evaporation rate at 212° F from the
weight of condensate.