In a dairy operation, milk at a flow rate of 250 liter/hour and a cow body temperature of 38.6°C must be chilled to a safe to store temperature of 13°C or less. Ground water at 10°C is available at a flow rate of 0.72 m3/h. The density and specific heat of water are 1030 kg/m3 and 3860 J/kg•K.
(a) Determine the UA product of a counterflow heat exchanger required for the chilling process. Determine the length of the exchanger if the inner pipe has a 50 mm diameter and the overall heat transfer coefficient is U = 1000 W/m2•K.
(b) Determine the outlet temperature of the water.
(c) using the UA from part a, determine the milk outlet temperature if the water flow rate is doubled