Adouble-pipe parallel-flow heat exchanger is to heat water (specific heat = 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 (specific heat = 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. c, determine the length of the tube required to achieve the desired heating