In a counter flow heat exchanger, water is being chilled by a sodium chloride brine. If the rate of flow of the brine is 1.8 kg s-1 and that of the water is 1.05 kg s-1, estimate the temperature to which the water is cooled if the brine enters at -8°C and leaves at 10°C, and if the water enters the exchanger at 32°C. If the area of the heat-transfer surface of this exchanger is 55 m2, what is the overall heat-transfer coefficient? Take the specific heats to be 3.38 and 4.18 kJ kg-1 °C-1 for the brine and the water respectively.
With heat exchangers a small sketch is often helpful: