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This is a heat-exchanger thermal rating calculator. i.e. it will enable you to predict heat transfer coefficient or |
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U of a heat exchanger based on actual heat exchanger geometry consequently sizing it. |
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Use illustration. |
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Design a shell and tube heat exchanger for following use. |
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1. Shell side 5000 kg/hr n-Hexane to be cooled from 80 C to 50 C with water at tube side. CW supply 28 C and return at 32 C. |
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Procedure- |
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1. Input shell mass flowarte as 5000kg/hr , Cp of 2.45 kJ/kg.K, inlet temp 80 C and outlet temp of 50 C. In tube side, input Cp |
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of 4.186, inlet temp of 28 C and outlet temp of 32 C. |
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2. Click on shell details and enter density of 650 kg/m3,Viscosity 0.21 cp,Wall viscosity 0.21 cp, k 0.1 w/mK,Shell ID 500 mm |
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(estimated) ,Baffle spacing 100 mm and fouling factor of 0.0002 m2K/W. Click Done. |
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3. Click on tube details and enter ID 8 mm, OD 12 mm, L 3000 mm, Passes 1, pitch of 6 mm, density of 1000 kg/m3 , viscosity |
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of 0.9 cp, wall viscosity of 0.9 cp, k of 0.179 W/mK, n of 0.4, fouling factor of 0.0002 m2K/W. |
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4. Enter Estimated U of 400 W/m2K . Click on calculate. |
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5. Evaluate the calculated figures. First being shell dia as you estimated the dia in your inputs. Min shell dia recommended in 144 |
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mm while we selected 500 mm. |
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Change the shell dia to 150mm and calculate again. |
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6. Evaluate calculated figures. Tube side pressure drop is 27 Pa. Typical allowable pressure drops are 15 Pa. To get lower |
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pressure drops number of tubes need to be increased. Increase the tube number in tube side inputs to 100 and calculate again. |
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Min. shell dia recommended increases to 177. Input shell dia 200 and calculate again. |
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7. Calculated U is 491 with 44% excess area. We could have reduced excess area but that would increase the pressure drop tube |
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side. Thus this is the final design. We need excess area to have reasonable pressure drop and velocity. |
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The final design is. |
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A 11.31 m2 heat exchanger is required with 100 tubes of 8mm ID,12 mm OD tubes of 3m length with 1 pass arrangement. This |
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fits into a 200 mm shell.with 40% cut baffles at 100 mm baffle spacing. |
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This would have a overall heat transfer coefficient of 491 W/m2K. |
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(Please note there could be many other alternate designs.) |