A double-pipe counter-flow heat exchanger is to heat water (Cp= 0.24 Btu/ Ibm. °F) flowing at a rate of 0.35 Ibm/s from Tin= 70°F. The heating is accomplished by Hot air available at 190°F and leaves the heat exchanger at 135°F . The inner tube is thin- walled has a diameter of 0.0416 ft. The overall heat transfer coefficient of the heat exchanger is Ui= (1/18) Btu/s.fr. OF.To Design a Heat exchanger determine the length of tube (L) required to achieve the desired heating. Cold Water 70°F Hot Air 135°F 190°F