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Effectiveness E, % 100 80 60 40 20 0 0.5 kg/s 90 deg C Cmin Cmax . 0.25 0.50 0.75 1.00 10 deg C 1 kg/s Tube fluid O Effectiveness , % 100 80 60 40 20 0 0 15 deg C max Cmin/Củ 50 0.25 -0.75 1.00 Shell fluid Shell fluid 1 2 3 4 5 1 2 3 4 5 Number of transfer units NTU=A,U/C min Number of transfer units NTU=A,U/C min [20] a) Calculate the effectiveness of the parallel flow double pipe heat exchanger shown above. (Water thermal properties could be assumed as constant.) What would have been the outlet temperatures of the cold and hot water streams if the exchanger would be twice as long? [20] b) [20] c) Would you be able to increase the heat transfer rate between the fluids if you would reverse the cold water flow direction on the outer tube? If yes, please quantify the heat transfer rate rise. If not, briefly explain your reasoning. 0 Tube fluid 18