Combustion Air Pre- heater ME 486 4/25/03 Combustion Air Pre-heater ME 486 4/25/03 Final Design Presentation Photo courtesy of David Pedersen

Combustion Air Pre-Combustion Air Pre-heaterheater

ME 486ME 486

4/25/034/25/03

Combustion Air Pre-heater

ME 486ME 486

4/25/034/25/03

Final Design Presentation

Photo courtesy of David Pedersen

224/25/034/25/03 Carl VanceCarl Vance

Purina Boiler Efficiency TeamPurina Boiler Efficiency Team

Members and RolesMembers and Roles Ryan CookRyan Cook

Documenter and SecretaryDocumenter and Secretary

Kofi CobbinahKofi CobbinahTeam Leader and Website ManagerTeam Leader and Website Manager

Carl VanceCarl Vance

Communicator and HistorianCommunicator and Historian

Matt BishopMatt BishopFinancial Officer and MediatorFinancial Officer and Mediator


Our Client – NestléOur Client – Nestlé Purina Purina

Client Contact:Client Contact: John Cain John Cain

Manager of Engineering at the Flagstaff Manager of Engineering at the Flagstaff Plant. Plant.

NAU Graduate in Mechanical EngineeringNAU Graduate in Mechanical Engineering

Purina as a company:Purina as a company:Flagstaff Plant opened in 1975Flagstaff Plant opened in 1975

Employs 180 peopleEmploys 180 people

Purina is now a division of Nestlé FoodsPurina is now a division of Nestlé Foods


Project DescriptionProject Description

Problem DefinitionProblem Definition NestlNestlé Purina has requested a design for a é Purina has requested a design for a

combustion air pre-heater. The goal of the combustion air pre-heater. The goal of the project is to provide savings for the plant by project is to provide savings for the plant by reducing energy costs and improving reducing energy costs and improving efficiency in the steam system.efficiency in the steam system.


Our Design PhilosophyOur Design Philosophy

Finish Design On Time and Under Budget.Finish Design On Time and Under Budget.

Satisfy the Client’s Requirements.Satisfy the Client’s Requirements.

Design for Safety.Design for Safety.

Act with Integrity.Act with Integrity.


Client’s RequirementsClient’s Requirements

Client’s Needs Statement:Client’s Needs Statement:

Design of a combustion air preheater must Design of a combustion air preheater must be:be: Economically FeasibleEconomically Feasible Minimize Modifications to Existing SystemsMinimize Modifications to Existing Systems Show an improvement in evaporation rate.Show an improvement in evaporation rate.


Purina Steam SystemPurina Steam System

The boiler produces approximately 500,000 The boiler produces approximately 500,000 lbm of steam per day. lbm of steam per day.

40%: cooking products.40%: cooking products.

50%: drying products.50%: drying products.

10%: miscellaneous areas: air and water 10%: miscellaneous areas: air and water heating systems.heating systems.

Steam production is 2/3 of the plant's total Steam production is 2/3 of the plant's total energy use.energy use.


Basic Basic Boiler OperationBoiler Operation

Source: Source: Reducing Energy CostsReducing Energy Costs, KEH Energy Engineering, 1990., KEH Energy Engineering, 1990.


What is a Combustion Air What is a Combustion Air PreheaterPreheater

Device or system that heats the boiler Device or system that heats the boiler intake air before it enters the combustion intake air before it enters the combustion chamber.chamber.

Uses recaptured waste heat that would Uses recaptured waste heat that would normally leave the boiler to the normally leave the boiler to the atmosphere. atmosphere.


Source: Source: Reducing Energy CostsReducing Energy Costs, KEH Energy Engineering, 1990., KEH Energy Engineering, 1990.


Design OptionsDesign Options

What are the industry standards?What are the industry standards?

Which design best meets our client’s Which design best meets our client’s requirements.requirements.


Runaround SystemRunaround System

Source: Source: Canadian Agriculture Library, http://www.agr.gc.ca/cal/calweb_e.htmlCanadian Agriculture Library, http://www.agr.gc.ca/cal/calweb_e.html


Gas - to - Gas Plate Heat Gas - to - Gas Plate Heat ExchangerExchanger

Source: Source: Canadian Agriculture Library, Canadian Agriculture Library, http://www.agr.gc.ca/cal/calweb_e.htmlhttp://www.agr.gc.ca/cal/calweb_e.html

14144/25/034/25/03 Ryan CookRyan Cook

Concentric Duct DesignConcentric Duct Design

Source: Canadian Agriculture Library, http://www.agr.gc.ca/cal/calweb_e.html


Design ChoiceDesign Choice

Final Design Choice: Final Design Choice: Concentric Duct DesignConcentric Duct Design

Air enters into a duct that surrounds the Air enters into a duct that surrounds the stack.stack.

The stack transfers heat to the air by The stack transfers heat to the air by convection and radiation.convection and radiation.

The air enters into the boiler at a higher The air enters into the boiler at a higher temperature.temperature.


Why a Concentric Duct?Why a Concentric Duct?

InexpensiveInexpensiveNo modifications to current systemNo modifications to current systemSimple Design that WorksSimple Design that WorksPassive SystemPassive System


Design BenefitsDesign Benefits

Concentric Duct Design Will Provide:Concentric Duct Design Will Provide: Relatively Low Installation CostRelatively Low Installation Cost Low Material CostsLow Material Costs Low Impact on Existing SystemsLow Impact on Existing Systems High Payback on InvestmentHigh Payback on Investment Low Maintenance CostsLow Maintenance Costs


Preheater Design BasicsPreheater Design Basics


Given ConditionsGiven Conditions

Exhaust Stack Surface TemperatureExhaust Stack Surface Temperature 399 K = 258 degrees Fahrenheit399 K = 258 degrees Fahrenheit

Inlet Air TemperatureInlet Air Temperature 305 K = 89 degrees Fahrenheit305 K = 89 degrees Fahrenheit

Exhaust Stack HeightExhaust Stack Height 4.3 meters4.3 meters

Exhaust Stack DiameterExhaust Stack Diameter 3 feet = 0.9144 meters3 feet = 0.9144 meters


Specifications to dateSpecifications to date

The exhaust stack height is 4.3 meters, The exhaust stack height is 4.3 meters, which fixes our duct height and will provide which fixes our duct height and will provide the surface area for heat transfer.the surface area for heat transfer.

Duct diameter will be 1.05 meters to Duct diameter will be 1.05 meters to optimize forced convection.optimize forced convection.

Mass flow rate of air through duct will be Mass flow rate of air through duct will be 4.52 kg/s. This gives an air velocity of 4.52 kg/s. This gives an air velocity of 13.56 m/s.13.56 m/s.


Temperature DistributionTemperature Distribution


Our DesignOur Design


Our DesignOur Design


InstallationInstallation

Two half tubes that will be welded together Two half tubes that will be welded together around the stack.around the stack.

Spacers will be inserted along the bottom Spacers will be inserted along the bottom to to keep the duct steady.to to keep the duct steady.

Will be hung by threaded rod supports Will be hung by threaded rod supports from the ceiling.from the ceiling.

Mathematical ModelsMathematical Models

Convection ModelConvection Model

Heat Exchanger ModelHeat Exchanger Model

Drag ModelDrag Model

Radiation ModelRadiation Model

Insulation ModelInsulation Model

Known Values for ConvectionKnown Values for Convection

Volumetric Flow Rate = 2.84 mVolumetric Flow Rate = 2.84 m33/s/s

Thermal Conductivity = .0263 W/(m*K)Thermal Conductivity = .0263 W/(m*K)

Kinematic Viscosity = 1.59E –05 mKinematic Viscosity = 1.59E –05 m22/s/s

Prandlt Number = 0.707Prandlt Number = 0.707

TTs s – T– Taa = 100 K = 100 K

Stack Surface Area = 12.26 mStack Surface Area = 12.26 m22

Stack Diameter = 0.9144 mStack Diameter = 0.9144 m


variable

O.D. (D2) I.D. (D1) hydraulic diameter X section area (m^2) airspeed (m/s) Re1 0.9144 0.086 0.13 22.04 59300

1.05 0.136 0.21 13.56 578001.1 0.186 0.29 9.66 56400

1.15 0.236 0.38 7.43 550001.2 0.286 0.47 5.98 53700


Pr Nu h (W/(m^2 K)) Ts - Ta (K) q" stack S.A (m^2) Energy transfer (W)0.707 131.8 40.49 100 4050 12.26 49700

129.1 25.04 2500 30700126.6 17.94 1790 21900124.1 13.85 1390 17000121.8 11.22 1120 13700

Convection Model SavingsConvection Model Savings

Estimate

Btu/h Yearly Btu Savings Gallons per year saved Yearly monetary savings 5- year savings 169600 1.038E+09 6920 $3,180 $15,900104800 6.410E+08 4270 $1,960 $9,80074700 4.570E+08 3050 $1,400 $7,00058000 3.550E+08 2370 $1,090 $5,45046700 2.860E+08 1910 $880 $4,400

Known Values for Known Values for Heat Exchanger Heat Exchanger

Cp,c = 1007 (J/kg*K) Cp,c = 1007 (J/kg*K)

Cp,h = 1030 (J/kg*K)Cp,h = 1030 (J/kg*K)

hhi i = 17.31 (W/m = 17.31 (W/m22*K)*K)

hhoo = 25.05 (W/m= 25.05 (W/m22*K)*K)

TTc,Ic,I = 305.4 (K) = 305.4 (K)

TTh,Ih,I = 509.1 (K) = 509.1 (K)

Mass Flow Rate = 4.52 kg/sMass Flow Rate = 4.52 kg/s


variableTh,o (K) Th,I (K) mdot h (kg/s) mdot c (kg/s) q (Watts)503.72 509.10 4.52 4.52 25050503.73 25000503.74 24950503.75 24910503.76 24860503.77 24810503.78 24770


result checkTc,I (K) Tc,o (K) Delta Tlm (K) U (W/m^2*K) Area (heat transfer)305.40 310.90 198.26 10.24 12.34

310.89 198.27 12.32310.88 198.28 12.29310.87 198.29 12.27310.86 198.30 12.25310.85 198.31 12.22310.84 198.32 12.20

Heat Exchanger SavingsHeat Exchanger Savings

Btu/h Yearly Btu Savings Gallons per year saved Yearly monetary savings 5- year savings85500 5.23E+08 3490 $1,610 $8,05085300 5.22E+08 3480 $1,600 $8,00085100 5.21E+08 3470 $1,600 $8,00085000 5.20E+08 3470 $1,600 $8,00084800 5.19E+08 3460 $1,590 $7,95084700 5.18E+08 3450 $1,590 $7,95084500 5.17E+08 3450 $1,590 $7,950

Known Values for Drag ModelKnown Values for Drag Model

Mass Flow Rate Mass Flow Rate

““a” = O.D. / 2a” = O.D. / 2

““b” = I.D. / 2b” = I.D. / 2


a (O.D./2) b (I.D./2) f duct friction head loss h f

0.5 0.4572 1.500 1.619E-03 2.0000.525 0.4572 1.500 1.660E-03 0.4900.55 0.4572 1.499 1.701E-03 0.1860.575 0.4572 1.499 1.744E-03 0.089

0.6 0.4572 1.498 1.786E-03 0.049


Sum of K values minor losses hm

0.25 6.1910.3 2.812

0.31 1.4750.35 0.9840.37 0.675

Drag Model CostsDrag Model Costs

specific energy loss (J/kg) power loss (W) kWh per year cost per year 5 year cost 80.3 363 2220 $133.2 $66632.4 146 890 $53.4 $26716.3 74 450 $27.0 $13510.5 47 290 $17.4 $877.1 32 200 $12.0 $60

Known Values for Radiation Known Values for Radiation

Inner and Outer DiametersInner and Outer Diameters

Emissivity of Steel Stack, εEmissivity of Steel Stack, ε1 1 = 0.87 = 0.87

Emissivity of Aluminum Duct, εEmissivity of Aluminum Duct, ε2 2 = 0.15= 0.15

Stack Surface AreaStack Surface AreaStefan- Boltzmann Constant Stefan- Boltzmann Constant σ = 5.67E –08 (W/(m2*Kσ = 5.67E –08 (W/(m2*K44))))Stack Temperature = 399.7 KStack Temperature = 399.7 KDuct Temperature = 322 KDuct Temperature = 322 K

Radiation ModelRadiation Model

variable

O.D. I.D. ε1 ε2 σ (W/(m2*K4)) stack surface area (m^2) T1 T2

1 0.9144 0.87 0.15 5.67E-08 12.26 399.7 3221.051.1

1.15

Radiation Model SavingsRadiation Model Savings

q (W) Btu/h Yearly Btu Savings Gallons per year saved Yearly monetary savings 5- year savings1620 5530 3.38E+07 225 $104 $5201690 5770 3.53E+07 235 $108 $5401750 5970 3.65E+07 243 $112 $5601820 6210 3.80E+07 253 $116 $580

Known Values for InsulationKnown Values for Insulation(Modeled as Fiberglass)(Modeled as Fiberglass)

R – Values:R – Values: Preheated Air = 0.559 (mPreheated Air = 0.559 (m2*2*K)/WK)/W Duct = 4.9E –04 (mDuct = 4.9E –04 (m2*2*K)/WK)/W Fiberglass Insulation = 16.78 (mFiberglass Insulation = 16.78 (m2*2*K)/W K)/W

(per inch)(per inch)

Average Temperature DifferenceAverage Temperature Difference

Insulation ModelInsulation Model

insulation thickness (inches) preheated air duct insulation0 R value 0.559 0.00041 0.001 0.559 0.00041 9.272 0.559 0.00041 18.534 0.559 0.00041 37.066 0.559 0.00041 55.59

Insulation Model CostsInsulation Model Costs

q (watts) Btu/h yearly cost 5 year cost5.36 18.30 $0.34 $1.720.31 1.04 $0.02 $0.100.16 0.54 $0.01 $0.050.08 0.27 $0.01 $0.030.05 0.18 $0.00 $0.02

insulation thickness (inches)01246

44444/25/034/25/03 Kofi CobbinahKofi Cobbinah

5 Year Savings Summary5 Year Savings Summary

Force ConvectionForce Convection $7980.00$7980.00

RadiationRadiation $540.00$540.00

Drag LossDrag Loss - $270.00- $270.00

Insulation LossInsulation Loss - $2.00- $2.00

Total Total $8250.00$8250.00


Design EstimateDesign Estimate

Total implementation cost:Total implementation cost:

Materials--- $350Materials--- $350

Labor--- $1650 Labor--- $1650

Total of approximately: $2,000Total of approximately: $2,000Source: McGuire Construction Co.Source: McGuire Construction Co.


Energy SavingsEnergy Savings

The energy added to the system was The energy added to the system was converted to kBtu’s per hour.converted to kBtu’s per hour.

Total kBtu’s per year saved = 553,000Total kBtu’s per year saved = 553,000

The evaporation rate will improve 1% for The evaporation rate will improve 1% for a daily average.a daily average.


Financial SavingsFinancial Savings

The Financial Savings were based on fuel The Financial Savings were based on fuel oil at $0.46 per gallon and 150 kBtu/gallon.oil at $0.46 per gallon and 150 kBtu/gallon.

This provides a 5 year savings of $8,248.This provides a 5 year savings of $8,248.

Simple payback for the project is 1.3 Simple payback for the project is 1.3 years.years.


Expenses Expenses

Total Expenses: $150.00Total Expenses: $150.00

Printing/Binding ---$100.00Printing/Binding ---$100.00

Photocopying --- $50.00Photocopying --- $50.00


Time LogTime Log

Average individual Hours: 120.7Average individual Hours: 120.7

Total Team Hours: 482.8Total Team Hours: 482.8


Our Appreciation Goes To:Our Appreciation Goes To:

Nestle Purina Company at Flagstaff.Nestle Purina Company at Flagstaff.

Mr. John Cain – Client Contact.Mr. John Cain – Client Contact.

Dr Peter Vadasz – Advisor.Dr Peter Vadasz – Advisor.

Dr. David Hartman – ME 486 Professor.Dr. David Hartman – ME 486 Professor.

Everyone at our presentation today.Everyone at our presentation today.


Project WebsiteProject Website

http://www.cet.nau.edu/Academic/Design/http://www.cet.nau.edu/Academic/Design/D4P/EGR486/ME/02-Projects/Heat/index.D4P/EGR486/ME/02-Projects/Heat/index.htmhtm

Or go to Or go to www.cet.nau.eduwww.cet.nau.edu and click on and click on “Design 4 Practice” and follow links to “Design 4 Practice” and follow links to “Senior Project Websites” and click on our “Senior Project Websites” and click on our websitewebsite


ConclusionConclusion

The team has been able to prove that The team has been able to prove that adequate heat transfer is available to pay adequate heat transfer is available to pay for the design, reduce energy costs, and for the design, reduce energy costs, and improve the efficiency of the boiler.improve the efficiency of the boiler.

Questions?

Photo courtesy of David Pedersen

Documents

Combustion Air Pre- heater ME 486 4/25/03 Combustion Air Pre-heater ME 486 4/25/03 Final Design Presentation Photo courtesy of David Pedersen