Reconsider Prob. 11–54. Using EES (or other) software, investigate the effects of oil exit temperature and water inlet temperature on the overall heat transfer coefficient of the heat exchanger. Let the oil exit temperature vary from 30°C to 70°C and the water inlet temperature from 5°C to 25°C. Plot the overall heat transfer coefficient as functions of the two temperatures, and discuss the results.

Data from problem 54

A thin-walled double-pipe counter-flow heat exchanger is to be used to cool oil (c_p = 2200 J/kg · K) from 150°C to 40°C at a rate of 2 kg/s by water (c_p = 4180 J/kg · K) that enters at 22°C at a rate of 1.5 kg/s. The diameter of the tube is 2.5 cm, and its length is 6 m. Determine the overall heat transfer coefficient of this heat exchanger.