Heat Exchanger Design Optimization ME 414 Thermal / Fluid System Design Final Project Department of Mechanical Engineering Fall 2005 December 13, 2005 Team Members: Kris Miller Matt Obras Andrew Wall Ben Warner Professor: John Toksoy

Problem Statement Design a heat exchanger to reduce the temperature of a chemical by 10º Celsius with the following parameters: Mass flow rate is 80,000 kg/hr. Fluid enters the heat exchanger at 35º C and should leave at 25º C. Material properties are approximated as water. Cooling of the chemical will be achieved by using treated water. City water is available at 20º C. Mass flow rate is adjustable.

Goals Cool hot fluid by 10º Celsius Minimize costs by: Minimizing weight Minimizing pressure drops Optimizing tube material

Funnel Effect 7 Effecting Variables 3 Critical Variables Tube OD Tube Outer Diameter Tube Thickness Shell Inner Diameter Shell Thickness Tube Length Tube Pitch Number of Tubes Number of Tube Passes Shell and Tube Material Use of Baffles Baffle Spacing Baffle Cut Shell Flow Rate Fluid Allocation Type of Flow Number of Passes Tube OD Shell ID Tube Length Number Passes Shell Mass Flow Rate Use of Baffles Baffle Space Tube OD Shell ID Tube Length 1 Factor Runs Engineering Judgment 2 Factor DOE’s Optimization

Starting Point for Optimization Process Output Variable Output Value Weight 330 kg ΔP Shell 6000 Pa ΔP Tube 30000 Pa Heat Transfer Rate 930000 W

Matlab DOE & Minitab DOE Main Effects Plots 7 Variables

Matlab DOE & Minitab DOE Main Effects Plots 3 Variables

Pareto Charts

Minitab Design Optimization Key Parameter Changes Pressure Drop (Shell and Tube) Number of Tubes Weight

Final Heat Exchanger Parameters Input Variable Input Value Number Tubes 329 Tube Passes 1 Tube OD 0.0127 m Tube ID 0.0102 m Tube Length 4.6 m Tube Pitch 0.0159 m Shell ID 0.3366 m Baffles No Shell Flow Rate 39 kg/s Output Variable Output Value Weight 550 kg ShellΔp 2700 Pa TubeΔp 6140 Pa Heat Transfer Rate* 948302 W Results using nominal values based on Minitab Optimization *Fouling was taken into consideration

Conclusion Chemical was successfully cooled 10 °C and met all specifications Cost minimized Low weight = low material cost Low pressure drop = lower operational cost

Questions