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Q22. A counter flow shell and tube oil cooler has 150 tubes of inside diameter 20 mm and wall thickness 3 mm. The tubes are each 3.2 m long. Oil flows in the tubes and water in the shell. The surface heat transfer coefficients are 1000 W/m² K and 2000 W/m² K on the oil and water sides respectively. Oil enters at a temperature of 80°C and water enters at 20°C. The mass flow rate of the oil is 16 kg/s and that of the water is 20 kg/s. The specific heat capacities are 2.0 kJ/kg K and 4.2 kJ/kg K for oil and water respectively.

(a) Determine the overall U value bared on the outside surface area of the tubes.

(b) Verify that the rate of heat transfer is approximately 880 kW.