Chapter 11, Problem 11.27P

In a dairy operation, milk at a flow rate of 250 L/h anda cow-body temperature of 38.6°C must be chilled to a safe-to-store temperature of 13°C or less. Groundwater at 10°C is available at a flow rate of $0.72{\text{ m}}^{\text{3}}\text{/h}$ .The density and specific heat of milk are $1030{\text{ kg/m}}^{\text{3}}$ and $3860\text{ J/kg}\cdot \text{K}$ , respectively.
(a) Determine the UA product of a counterflow heatexchanger required for the chilling process. Determine the length of the exchanger if the inner pipehas a 50-mm diameter and the overall heat transfer coefficient is $U=1000{\text{ W/m}}^2\cdot \text{K}$ .
(b) Determine the outlet temperature of the water.
(c) Using the value of UA found in part (a), determine the milk outlet temperature if the water flow rateis doubled. What is the outlet temperature if theflow rate is halved?