ME 414Thermal&FluidSystems Design

Heat Exchanger DesignME 414 Thermal / Fluid System Design

William DonelsonJosh FossoLaurie Klank

Jonathan Moore

Fall 2005December 13, 2005

Professor: John Toksoy

ME 414Thermal&FluidSystems Design

Problem

• Cool a Fluid– From 35ºC to 25ºC– Mass Flow 80,000 kg/hr– Fluid is Corrosive– Fluid Properties are Approximated by Water

• Use City Water to Cool– Available at 20ºC

ME 414Thermal&FluidSystems Design

Assumptions

• Shell and Tube HX

• Corrosive Fluid Requires Stainless Steel Tubes– Fouling is Negligible– Easier to Clean

• Shell is Thin, Light as Possible

ME 414Thermal&FluidSystems Design

Begin Study

• Given Tube Arrangement

• Choose Tube Arrangement– Cleaning– Assembly

SDfN

ME 414Thermal&FluidSystems Design

Analysis

HHp TCmQ )( CCp TCm )( lmTUA

LDNhLkN

DD

LDNhUA ii

i

o

oo 1

2

ln11

ME 414Thermal&FluidSystems Design

Observations

• More on this Later

)(, CoC mfT

CSio mDDDfL ,,,

•Length can be Calculated•Heat Transfer is Always as Desired•Nusselt Number Correlation

ME 414Thermal&FluidSystems Design

Minimize Cost

• Assume HX Lifespan is 7 Years

• Labor-Upkeep and Assembly– Arrangement and Materials

• Operating– Electricity for Pumps– Cooling Water Considered Separately

• Materials

ME 414Thermal&FluidSystems Design

Cost Function

• Electricity– $0.06558 kW·hr (IPL)– Pump Efficiency = 0.7

• Materials– Wholesale Metal Prices Compared with Finished Product Prices

to Get Value Added Multiple• Multiple = 5 (McMaster)

– Wholesale Stainless Steel = $2.86/kg– Wholesale Aluminum = $1.88/kg

(metalprices.com)

ME 414Thermal&FluidSystems Design

Approach

• Cost Function Automatically Weighs – Pressure Drops– Weight

• Q is Always Equal to Desired by Calculating Length

• With Trial the Only Other Constraints Were the Fluid Velocities

ME 414Thermal&FluidSystems Design

Trial 1Te

rm

Standardized Effect

Shell ID

876543210

2.447

Pareto Chart of the Standardized Effects(response is Cost, Alpha = .05)

Hi

Lo0.17011D

New

Cur

d = 0.87083

Targ: 1.0

Shell V

d = 0.00950

Targ: 1.50

Tube V

d = 0.59495

Minimum

Cost

y = 1.0646

y = 0.9057

y = 7025.270

0.2591

0.3505

0.0081

0.0110

33.0480

44.7120Tube OD Shell IDM Dot

[38.6390] [0.0095] [0.3048]

Tubes Need to be Standard SizeVelocities Must be Within Acceptable Range 0.6<Shell Velocity<1.5 m/s 0.9<Tube Velocity<2.5 m/s

Minitab Does Not Recognize the Effect of M Dot on Cost

ME 414Thermal&FluidSystems Design

Final TrialTe

rm

Standardized Effect

Tube OD

M Dot

Shell ID

876543210

2.776

Pareto Chart of the Standardized Effects(response is Cost, Alpha = .05)

Hi

Lo0.00000D

New

Cur

d = 0.00000

Targ: 1.0V Shell

d = 0.00833

Targ: 1.50V Tube

d = 0.48624

MinimumCost

y = 1.5225

y = 0.9050

y = 6541.2875

0.2591

0.3505

0.0081

0.0110

52.750

57.750Tube OD Shell IDM Dot

[55.250] [0.0095] [0.3048]

After Further Refinement

Optimum M Dot = 55.25

ME 414Thermal&FluidSystems Design

Final Design

• M Dot Cooling Fluid= 55 kg/s

• Tube OD = 0.38 inch BWG 24

• Shell ID = 12 inches

• Length = 3.4102 m

• Tube Pressure Drop = 6047 Pa

• Shell Pressure Drop = 9308 Pa

• Total Weight = 443 kg

ME 414Thermal&FluidSystems Design

Total Cost

•$5720

• Plus Labor

• Plus Water

ME 414Thermal&FluidSystems Design

Cost of Water

)(, CoC mfT

Since TC,o cannot Exceed TH,i the mass flow of the Cooling Water has Lower Bound of 15 kg/secThis translates into 1,370,000 ft3/month

$13,900/Month

Indianapolis Water