We do not know the exit temperature of the oil, and thus we cannot
determine the bulk mean temperature, which is the temperature at which the
properties of oil are to be evaluated. The mean temperature of the oil at the
inlet is 20°C, and we expect this temperature to drop somewhat as a result
of heat loss to the icy waters of the lake. We evaluate the properties of the oil
at the inlet temperature, but we will repeat the calculations, if necessary,
using properties at the evaluated bulk mean temperature. At 20°C we read
(Table A-14)