Reconsider Prob. 22–40. Using an appropriate software, investigate the effects of temperature and mass flow rate of geothermal water on the length of the tube. Let the temperature vary from 100°C to 200°C, and the mass flow rate from 0.1 kg/s to 0.5 kg/s. Plot the length of the tube as functions of temperature and mass flow rate and discuss the results.

Reconsider Prob. 22–40.

A double-pipe parallel-flow heat exchanger is to heat water (c_p = 4180 J/kg·K) from 25°C to 60°C at a rate of 0.2 kg/s. The heating is to be accomplished by geothermal water (c_p = 4310 J/kg·K) available at 140°C at a mass flow rate of 0.3 kg/s. The inner tube is thin-walled and has a diameter of 0.8 cm. If the overall heat transfer coefficient of the heat exchanger is 550 W/m²·K, determine the length of the tube required to achieve the desired heating.