In a food industry, 12,000 kg/h of a fluid (p=2.12 kJ/kg R) are processed at 15C. The fluid temperature is increased to 72 C in a countercurrent double tube heat exchanger, using 20,000 kg/h of saturated liquid water as heating fluid. The water is fed at 1 atm. The overall heat transfer coefficient is 1.75 kW/m2 K. a) Use the NTU method and calculate the surface area of the heat exchanger. b) Repeat the previous part assuming that the flows are in parallel.