Question

17.2 To exchange heat between four streams: Stream C (kW/°C) Ts (°C) T' (°C) С1 2.5 125 C2 3.0 20 25 150 HI 100 60 H2 2.5 8.0 90 60 with AT min = 20°C, the HEN in Figure 7.43 is proposed Determine if the network has the minimum utility require mentsOf not, design a network with the minimum utility requirements. Selso, break the heat loops to design a network with the minimum number of units in the specifications Exatrpie 7.5, which alternative- ja preferred?

Answer 1

solution Gioen data ATmin = 20°C In these we cannot where two fluids are difference of temperatur design a heat exchanger exchanging heat and between them is showo below 20°c 2006 250 600 90°c ooc 10500 1500 exchanger netcork across pinch Now, design temperature a heat 70°C. cn >> coche 90°c soko - 60°C 8 (Hz) goc 10kW = }}ok 600 (205) (Hi) 150 0 0 2 106°c Lookism 56.01 3. 25 C le 90% 43.670 1 90kw Ø-pousesc (8.5) heat mcpOT transfer poom 150° to 40° a = 1150 - 70) x2.5 Q = 200 kW Scanned with CamScanner

Heat Tansfer from 70 C to 600 (H) 8x10 = 80 kw and for (Co) - 45X3 135 kW at These pore, heat toanspor from is cooling sokw Bokwu 70°c to 60°c 18 temperature At point 3 80 - 3(70-x) 80 70-43 x = 70-80 is X3 = 43.3°C ne-4, corresponding heat loss 0 = 25 (70-x4) 10 - 70 - X4 2.5 = 70 - 10 tt = 66°C Xq in cool and hot added must be heat cticity Then, si de In hot side - - from 106 to 1500 is 2.5 (150-106) 110kw Scanned with CamScanner

is 66°C to doc cold utility → 46x3 = 138kW 43.67°C to 25°C added added cob Oficity Ricet y & 3x (43•67-25) 56.01kw across node uticity diagram final the Noco, doaw 780 temperatur pinch soku 170 - 600 lokw 60 1060 (Hi) 150°C lokwa Na kw x =560/40 (62) 100% 43.67 67 290w = 3846 (0) 1256 -110 10 s, & hot oticity - 110kw # 2 no. of cold oticity is -56.01 and 138kw added. Scanned with CamScanner