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Heat Exchanger Design Thermal

Required Design Parameters. Heat Exchanger Must Cool the Chemical From 35

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Heat Exchanger Design Thermal

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    1. Heat Exchanger Design Thermal / Fluid System Design Final Project Department of Mechanical Engineering Fall 2005 December 13, 2005 Team Members: Andrew Burian Jack Copenhaver Chris Haire Brandin Ray Professor: John Toksoy

    2. Required Design Parameters Heat Exchanger Must Cool the Chemical From 35°C to 25°C Cannot Exceed 7m In Length or 2m in Diameter Minimize Heat Exchanger Shell Diameter and Tube Length to Reduce Cost Minimize Pressure Drop Chemical Mass Flow Rate Fixed at 80 kg/hr City Water to be Used as Cooling Fluid With an Inlet Temperature of 20°C

    3. Assumptions Isothermal Material Properties (Shell and Tube) Constant Properties Steady State Incompressible Fluids 24 Hour Duty Cycle Heat Transfer Through Shell is Minimal

    4. Initial Possible Factors Effecting Heat Exchanger Design Mass Flow Rate (Shell Side) Tube Length Shell I.D. Tube Pitch Tube Material Shell Thickness Tube O.D. Tube Thickness Number of Tubes Baffle Spacing Baffle Cut Shell Material Flow Direction

    5. “One Factor at a Time” Study

    6. Factors Found to Have Greatest Effect on Weight and Heat Transfer Tube Length Shell I.D. Baffles Tube O.D. Number of Tubes Pitch (Square or Triangular) Mass Flow Rate

    7. Main Effects Plots With Seven Factors

    10. Final Factors Tube Length Tube Material Tube O.D. Shell I.D.

    11. Main Effects Plots With Final Factors

    16. Final Design Specifications (Clean Heat Exchanger) Shell I.D. =.3048m Shell Thick. = 2mm Tube O.D. = 9.25mm Tube Thick. = .559mm Number of Tubes = 550 Weight = 590.80kg

    17. Initial vs. Final Specifications Initial Final Mass Flow Rate ……….. 59.0 kg/s 43.0 kg/s Flow Direction …………. Counter Flow Counter Flow Shell I.D. ……………….. 0.3784 m 0.3048 m Shell Thickness ……….. 2.0 mm 2.0 mm Shell Material ………….. Bronze Stainless Steel Tube O.D. ……………… 9.525 mm 9.525 mm Tube Thickness ……….. 0.889 mm 0.559 mm Tube Length …………… 3.2 m 4 m Number of Tubes……… 889 550 Tube Material…………... Aluminum Stainless Steel Tube Pitch………………. Triangle (30°) Triangle (60°) Baffle space…………….. 0.75 m 2 m Baffle Cut……………….. 0.116 m 0.150 m

    20. The Argument for Stainless Steel

    21. Stainless Steel Pros Cons Not Chemically Reactive Easy to Clean Not as Easily Damaged During Cleaning Food Industry Uses Easy to Repair Harder to Machine Shipping Costs/Requirements Small Decrease in Heat Transfer

    22. Aluminum Pros Cons Easy to Work With Light Weight Slightly Increased Heat Transfer Soft – Easier to Damage During Maintenance Hard to Repair Anodic to Most Other Metals Chemically Reactive Weak (With Respect to Stainless)

    23. Stress Analysis Using General Material Properties for Annealed 300 Series Stainless Steel and “Worse Case” Heat Exchanger Pressures Taken From D.O.E. Study

    24. H. E. Specifications and Properties Shell I.D. = 0.3048 m Shell Thick. = 2 mm Tube O.D. = 9.25 mm Tube Thick. = 0.559 mm ? PShell = 3000 Pa ?PTube = 14000 Pa E = 190 GPa a = 17.2 e – 6 sY = 6.55 GPa

    25. Calculated Stresses sY = 6.55 GPa Shell Hoop Stress = 2.29 GPa Shell Long. Stress = 1.14 GPa Tube Hoop Stress = 1.02 GPa Tube Thermal Stress = 19.7 KPa

    26. Questions?

    27. Appendix

    28. MATLAB Results With Optimized Factors Desired Heat Transfer Rate = 928500.92 W Calculated Heat Transfer Rate = 929320.42 W Difference = -819.50 W Desired-to-Calculated Ratio = 1.00 HE Pressure Drop ===================== Shell Side Delta-P = 2181.04 Pa Tube Side Delta-P = 5363.92 Pa Heat Exchanger Weight ===================== Shell Weight = 60.72 kg Tube Weight = 273.66 kg Shell Fluid Weight = 134.82 kg Tube Fluid Weight = 121.61 kg ----------- Total HE Weight = 590.80 kg Tube Side Heat Transfer Parameters ======================================== Number of Tubes N = 550.00 Number of Passes = 1.00 Tubes OD OD = 0.0095 m Tubes ID ID = 0.0084 m Tube Length L = 4.0000 m Tube Flow Area Af = 0.0305 m2 Tube Solid Area As = 0.0392 m2 Tube Pitch PT = 0.0119 m Average Velocity V = 0.73 m/s Mass Velocity G = 727.87 kg/m2.s Reynolds Number Re = 7657.84 TURBULENT Nusselt Number Nu = 63.05 HT Coefficient h = 4629.32 W/m2.C

    29. Overall Heat Transfer Coefficient ====================================== U (Tube Outside Area) = 1975.17 W/m2.C Heat Transfer Rate ====================================== Desired Heat Transfer Rate = 928500.92 W Calculated Heat Transfer Rate = 929320.42 W Difference = -819.50 W Desired-to-Calculated Ratio = 1.00 Shell Side Heat Transfer Parameters ====================================== Shell ID = 0.3048 m Shell Cross Sec Area = 0.0730 m2 Shell Flow Area = 0.1219 m2 Baffle Space = 2.0000 m Number of Baffles = 1.0000 m Shell Equivalent Dia = 0.0069 m Mass Velocity G = 352.69 kg/m2.s Reynolds Number Re = 2576.25 TURBULENT Nusselt Number Nu = 51.07 HT Coefficient h = 4502.58 W/m2.C

    30. Additional Plots From Seven Factors MINITAB Run

    32. Pareto Charts With All Combinations Considered

    36. Pareto Charts With Irrelevant Combinations Removed

    40. Credits Minitab 14 MatLab 7.0

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