40 Heat exchanger Double pipe Flow Configuration Heater temperature (C) Hot water Cold T2 T: flow rate water flow T T: TS TO (L/min) rate (C) (C) O)(O) (C) (C) (L/min) 1 39.6 35.9 335 13.8.17.2 19.7 1 2 39.5 35.2 322 13.4 15.6 17.1 39.7 3.233.2 13.5 16.4 19.1 I 2 39.4 35.332.113.3 15 16 7 Parallel flow Parallel flow Counter-current flow Counter-current flow 1. Determine the heat duty for the cold and hot streams: Q Vc Cold stream: Pc Cpc (T6 - T4) 60 Vh = 60 Hot stream: an Pn Cph (T1-T3) Where, V. and Vn=volumetric flow rate (L/min) of the cold and hot stream, respectively. Pc and Pn= density of the cold and hot stream (From equation A): kg p (49) = 1.004 4.0007 x 10-51 4.582 x 10-652 (A) T is the average stream temperature in C. Cpc and Cpn= mass heat capacity of the cold stream in kJ/kg. C (From equation B). kj kg.K (B) Cp ( x) = 4.2113 2.4403 x 10-3 T + 7.0487 x 10-552 + 1 x 10-673 +6 x 10-9 54 2. Calculate and compare the overall power efficiency: Qc nthermal -x 100% an 3. Compare the cold and hot thermal efficiency of the three heat exchangers. T6 - T4 Pc x 100% T-TA =