A countercurrent heat exchanger is being used to heat a liquid
food from 15 to 70°C. The heat exchanger has a 23 mm
internal diameter and 10m length with an overall heat-transfer
coeffi cient, based on the inside area, of 2000 W/(m 2 K). Water,
the heating medium, enters the heat exchanger at 95°C, and
leaves at 85°C. Determine the fl ow rates for product and water
that will provide the conditions described. Use specifi c heats
of 3.7 kJ/(kg K) for product and 4.18 kJ/(kg K) for water.