Brick City OvenProject 05424

Group Members:Derek StallardAdam George

Nathan Mellenthien Izudin Cemer

Sponsors

VP Office, RIT Finance & Administration

Sponsor contact: Abraham Fansey

A Pizza Venture with a Differentiated Advantage

Goals of Pizza Venture High Quality Product Faster Delivery of Product to

Customers

Objectives of Pizza Venture Product Research and Development Innovative Business/Marketing Plan Proximity to Target Market Great Oven

Process

Define problem Data collection/Research Concept development/Brainstorming Feasibility assessment Performance objectives &

specifications Analysis & synthesis Detailed design

Needs Assessment Overview and Structure Level 0: Project Mission Statement (Qualitative) Level 1: Qualifiers (Qualitative) Level 2: Winners (Qualitative) Level 3: Qualifiers (Quantitative) Level 4: Winners (Quantitative) Level 5: Key Business Goals (Internal Stakeholders) Level 6: Primary Market Goals (External

Stakeholders) Level 7: Secondary Market Goals (Scope Limitations) Level 8: Innovation Opportunities (Pre-empt Future

Needs)

Level 0 : Mission Statement

Design and build a high temperature pizza oven to replicate the unique results of a coal oven

Fabricate a working, scaled-down prototype at R.I.T.

Level 1: Qualifiers (Qualitative) Technological Attributes

Oven will reach high temperatures as per sponsor specifications

Budget and Economic Attributes Oven must be able to be built within a reasonable

budget Performance Attributes

Oven must cook pizzas in the designated amount of time

Oven must be able to sustain high temperatures Schedule or Time Attributes

Prototype of oven must be able to be constructed within the allotted time for Senior Design

Level 2 : Winners (Qualitative) Technological Attributes

Oven should use new technologies to obtain desired temperatures

Oven should have a “high-tech” look and feel to it Oven should reach temperatures above sponsor specifications Oven should be user friendly

Budget and Economic Attributes Prototype should be constructed under sponsor specified

costs Performance Attributes

Oven should maintain high temperatures without much heat loss

Oven should cook pizzas in a shorter period of time than sponsor specifications

Schedule or Time Attributes Prototype should be constructed ahead of the allotted Senior

Design II scheduled time to allow for testing and adjustments ( levels 3-7)

Level 8 : Innovation Opportunities

Few “environmentally friendly” high temperature pizza ovens in market

Few “high tech” interfaces on ovens in market

Opportunity to combine traditional pizza cooking methods with new technologies

Concept Development

Started out defining top Qualifiers according to the sponsors needs High cooking temperature in the

range of 700-850°F Use same heat transfer methods by

original coal oven

Concept Development User friendly

Very little training required for usage by new employees

Interface controls that easily operate the oven features

The final important qualifier that we identified was the aspect of Safety

Research and data collection

Second phase of concept development was research and data collection. Types of ovens and their operating

conditions History and methods employed by

traditional coal ovens Controllers, materials, insulation, and

various components

Research and data collection Types of fuel sources

Electric Natural gas Wood and coal

Styles of applying the fuel source Traditional burner (flame) Infrared technology Electric heating coils Impingement

Common characteristics

Formulated several concepts These concepts shared a few

common design characteristics A refractory dome roof

Supplies radiant heating A stone deck cooking surface

Creates a crisp crust Provides convection surface

Concepts Developed Non-rotating deck with gas under

hearth burner Similar to existing ovens We believe as a group that this could be

easily accomplished to a certain extent Lacks radiant heat transfer method Absence of rotating deck**We have decided that this concept is not going to be pursued

any further.**

Concepts Developed

Rotating deck with gas or IR under hearth burner

Rotating deck stone Under hearth burner

Gas under hearth IR under hearth

**This concept will not be pursued further due to its limitations**

Concepts Developed Rotating deck with IR under hearth and

rear gas burner Rotating deck will create a “user friendly”

oven IR under hearth will heat the stone deck

very efficiently The rear gas burner will provide the heat for

the ambient air and radiant dome. Drawback?

Close proximity of rear burner to edge of pizza

Concepts Developed Rotating deck with IR under hearth and

rear burner with guard Incorporates other concepts’ best features

Rotating stone deck IR burner Rear gas burner

Added a flame guard to direct the heat up and away from the pizza towards the refractory dome

Concepts Developed

Rotating deck with IR under hearth and rear burner with guard

Feasibility Assessment

Compiled feasibility chart Prioritized criteria Set target values Evaluated design options

Performance Objectives & Specifications

Design objectives WHAT the design must do

Performance Specifications HOW the design will meet the

objectives

Design Objectives Replicate and improve upon a coal oven

Reaches high internal temperatures Mixture of traditional baking methods and

current technology Evenly cooked pizza User friendly Capable of high production Oven should be safe with minimum

exposure of the cook to high temperatures

Performance Specifications Stone deck must reach a minimum

temperature of 650°F Internal air temperature must reach a

minimum temperature of 850°F Deck must be rotating and have a variable

speed Oven insulation: outside surface is no higher

than 120°F Cooking time: no longer than five minutes per

pizza Capacity shall be a minimum of six 12” pizzas

Analysis and Synthesis Aspects

Heat Transfer Stress/Strain Electrical

Heat Transfer Conduction

Experimental determination of k value Convection Radiation Determination of heat required to cook

pizza Final time to cook pizza Heat loss Heat generation (still in process)(modes of transfer)

Heat Required to Cook Pizza

Standard oven, pizza stone, and measuring devices required

Set area and thickness Heat required=(mi-mf)*L Values

L=2260 kJ/kg A=.07297 m2 (D=.3048m)

Final value of 1808 kJ

Final Time to Cook Pizza

Total Heat Supplied = Heat Rate * Cooking Time

Total Heat Required = 1808 kJ Heat Rate=

Conduction+Convection+Radiation Heat Rate=12120.4 J/s Total Cooking Time=149s (2 min, 29

sec)

Photos from experiment

Photos from experiment (Continued)

Heat Loss

To Pizza Through Door

Open Closed

Through Wall Through Flue (Still in calculation)

Heat Loss to Pizza

Max Capacity: 120 (12”) pizzas Aim: 100 pizzas per hour Each pizza takes 1808 kJ to bake Average heat lost to pizzas=

180,800 kJ/hr=50,222 J/s 171,365 BTU/hr=47.6 BTU/s

Heat Loss Through Conduction (Closed door and Wall)

Compound Wall Unsure of insulation thickness

desired Wanted to be able to try different

values Plugging numbers into equations

would be time consuming and inefficient

The Solution? A Visual Basic

program Input

k Thicknesses

Output Temperature at

outer surface Heat Rate (calculations)

Heat Loss Results Heat loss to pizzas*: 50,222 J/s Heat loss through walls: 176.32 J/s Heat loss through door:

Open: 942.5 J/s Closed: 26.81 J/s

Heat loss through flue: To Be Determined Total Heat loss Range during operation**:

50,425 J/s to 51,341 J/s*Oven is operating at aimed capacity**Figures do not include heat loss through flue

Mechanical Analysis

Using COSMOS finite element analysis Deformation Displacement of Base Strain Von Mises Stress

Strain Max of 7.335x10-5; Min of 3.072x10-8

Displacement of Base Max of 1.774x10-4 m (6.984x10-3 in.)

(von mises)

Control Type of control problem

determines the type of control system (major types of control are shown in Fig.)

Continuous system: values (temperature) changes smoothly

Linear: simplest control method (it can be modeled mathematically)

Our choice of controller is PID

PID

PID controllers will not be stand alone

PID controllers will be in PLC’s PLC’s will be software based

Controllers Job (PID)

To maintain the output (temperature) at a constant level. Meaning there is no error or

difference between the PV (present temp.) and a SP (desired temp.)

Actual temp. received as an input Therefore it (PID) will control the

valve to regulate flow of gas

Controllers Job (PID) PID automatically finds correct flow of

gas that keeps temp. steady at set point.

If set point is lowered PID reduces the amount of gas flow to the heater

If set point is raised the PID increases the amount of gas flow to the heater

This can be visualized in the following graph

Process Description

Introduction: Software based PLC will be used to control the oven Oven will have two heating elements (controlled

separately) There will be three temp. sensors and four

thermocouples (2 per heating element) Numerous safety controls Two operating Modes

- Preheat mode

- User mode

Process Description

Preheat Mode: User interface screen will display the temperature of

the two heating elements Buttons to control each element Heaters will be fully turned on Can not control the heating elements independently

until moved to User Mode Buttons for aborting preheat mode Safety check will be performed in this mode

(discussed below) Shutdown button (put system into idle state)

Process Description User Mode:

New user interface screen displays temp. of each heating element and of each temp. sensor

User override allows each element to be controlled individually

Status of each heating element will also be displayed Start button will start rotating the deck and maintain

the desired temp. Once the rotating deck is turned off the system goes

into idle state same as if the SHUTDOWN button is pushed

If preheat button is pushed, the system goes into preheat mode

Process Description Safety check will also be performed in user mode as

described in the following slides Idle State:

All heating elements are off Rotating deck is off Message on user interface screen will be displayed

“In Idle State” A safety check will also be performed continuously

Safety Check Run continuously in all modes 1st the temp. differential between the two thermocouples

will be performed on each heating element Large differential could indicate faulty thermocouple or

fire inside the oven Temp. of each sensor will be compared to a given

maximum temp. This prevents the oven from getting dangerously hot

Different WARNING error will be generated for each error and displayed on the screen

The system will return to the Idle State The system can be restarted once the problem has been

resolved

Characteristics of PID controllers

Continuous process controllers Analog input (actual temp. PV) Analog output Set point

Example of “continuous process control” Temp. pressure, and flow

Simple control Two temp. limit sensor (one low one high), and then switch

the heater on when low temp. sensor turns on, and switch the heater off when high temp. sensor goes on. (something probably done on our prototype)

Analog Input (PV (process variable)) Want PV to be highly accurate For example if we want to maintain a temp +/- of 10

degrees then we typically strive for at least 10X of that (or 1 degree)

If analog input is 12 bit and the temp. range for the sensor is 0 to 1000 then

Theoretical accuracy = 1000 degrees/ 4096 (12 bits) =0.244 degrees

Theoretical because no noise in sensors, wiring, and analog converter.

Output In the heating oven it would mean is the valve totally

closed (0%) or totally open (100%) Setpoint (SP): what temperature do you want

Senior Design II Timeline Spring Break: Complete calculations Week 1: Review PDR feedback,

submit final budget Week 2: Order approved parts Week 3-6: Construction Week 7-8: Test and analysis,

modifications Week 9-10: CDR preparation

Trial 1

Toven=232.2 °C Mi=.805 kg Mf=.715 kg T=11 minutes Heat=2034 kJ

Trial 2

Toven=260 °C Mi=.655 kg Mf=.585 kg T=10 minutes Heat=1582 kJ

Trial 3

Toven=287.8 °C Mi=.800 kg Mf=.720 kg T=8 minutes Heat=1808 kJ

(back)

Conduction Assume

1-D conduction Standard pressure Constant Area and

Thickness Avg. temp of pizza=330.7 K

Values λ(k)=3.43 W/mK A=.07297 m2 (D=.3048m) W=.00635m T1=616.5 K T2=330.7 K

Q=11264.9 J/s(back)

Convection Assume

1-D convection Steady State Standard pressure Constant area and

thickness Free Convection Avg. temp of pizza=135.5°F

Values α=3.43 W/mK A=.07297 m2 (D=.3048m) W=.00635m T=727.6 K TW=330.7 K

Q=144.8 J/s

Radiation Assume

1-D radiation Standard pressure Constant Area and

Thickness Avg. temp of

pizza=330.7 K Values

ε=.75 W/m2K A=.07297 m2 (D=.3048m) σ=5.67x10-8 W/m2K4

T1=697.3 K T2=330.7 K

Q=710.7 J/s

Determination of Thermal Conductivity Lack of availability of

specific k value for pizza Standard oven, pizza stone,

and measuring devices required

Set area and thickness dQ=(mi-mf)*L Values

L=2260 kJ/kg A=.07297 m2 (D=.3048m) dt=240 s mi=.300 kg mf=.290 kg Ti=23.2°C Tf=65.5°C

Solving for k yields k=3.43 W/mK

(back)

x

TkA

dt

dQ

Heat Transfer Through Door (Open)

Assume 1-D radiation Standard pressure Steady State

Values ε=.75 W/m2K (concrete) A=.096774 m2 (door) σ=5.67x10-8 W/m2K4

T1=697.3 K T2=293.2 K

Q= 942.5 J/s

Heat Transfer Through Door (Closed) Conduction

AISI 304 Stainless Steel k=16.6 W/mK .003175 m thick (1/8”) on

both sides Insulation (Durablanket S

Ceramic Fiber Blanket) k=.087 W/mK .1016 m thick (4”)

between Stainless Steel plates

Using Program Q=26.81 J/s TSurface=168.1 °F

Code for Wall CalculationsPrivate Sub CommandButton1_Click()s = steelthickness.Valuet = insulationthickness.Valueks = ksteel.Valueki = kinsul.Valueq = (727.6 - 293.2) / ((1 / (5 * 0.09677)) + (s / (ks * 0.09677)) +

(t / (ki * 0.09677)) + (s / (ks * 0.09677)) + (1 / (5 * 0.09677)))tinsul = 727.6 - (q * ((1 / (5 * 0.09677)) + (s / (ks * 0.09677)) + (t /

(ki * 0.09677)) + (s / (ks * 0.09677))))tinsul = (9 / 5) * (tinsul - 273) + 32tral = Format(tinsul, "#0.000")qvalue = Format(q, "#0.00")qval.Caption = qvalueresult.Caption = tralEnd Sub(back)

Heat Transfer Through Wall Conduction

Reflective Concrete k=.80 W/mK .1016 m thick (4”)

Insulation (Durablanket S Ceramic Fiber Blanket)

k=.087 W/mK .2032 m thick (8”)

Air k=28.5*10^3 W/mK .0254m thick (1”)

AISI 304 Stainless Steel k=16.6 W/mK .003175 m thick (1/8”)

Using Program Q=176.32 J/s TSurface=123.0 °F

Code for Wall CalculationsPrivate Sub CommandButton1_Click()c = concretethickness.Valuet = feltthickness.Values = steelthickness.Valuekc = kcon.Valueki = kinsul.Valueks = ksteel.Valueq = (727.6 - 293.2) / ((1 / (5 * 1.162)) + (c / (kc * 1.162)) + (t / (ki *

1.162)) + (0.0254 / ((28.5 * 10 ^ 3) * 1.162)) + (s / (ks * 1.162)) + (1 / (5 * 1.162)))

tinsul = 727.6 - (q * ((1 / (5 * 1.162)) + (c / (kc * 1.162)) + (t / (ki * 1.162)) + (0.0254 / ((28.5 * 10 ^ 3) * 1.162)) + (s / (ks * 1.162))))

tinsul = (9 / 5) * (tinsul - 273) + 32tral = Format(tinsul, "#0.000")qvalue = Format(q, "#0.00")qval.Caption = qvalueresult.Caption = tralEnd Sub

Von Mises Stress Max of 2,312 kN/m2 (335.3 psi) (back)

Deformation

Level 3 : Qualifiers (Quantitative) Technological Attributes

Oven must reach at least 750°F Budget and Economic Attributes

Prototype must be able to be built within a budget of $3000.

Performance Attributes Oven must cook pizzas in less than 5 minutes. Oven must be able to keep high temperature of

at least 750°F. Schedule or Time Attributes

Prototype of oven must be able to be constructed by May 19, 2005.

(back)

Level 4 : Winners (Quantitative) Technological Attributes

Oven should use some sort of newer technology to cook pizza (Rotating deck, IR burner, etc).

Oven should have a computerized interface. Oven should reach at least 800°F Oven should be able to be used by an average college student

Budget and Economic Attributes Oven should be constructed under $2000.

Performance Attributes Oven should maintain high temperatures without much heat

loss. Oven should cook pizzas in less than 4 minutes.

Schedule or Time Attributes Prototype should be constructed ahead of the allotted Senior

Design II scheduled time to allow for testing and adjustments.

Level 5 : Key Business Goals The costs of the pizza oven must be

reasonable enough to warrant further production.

The pizza oven must perform well enough to maintain a consistent output of a high volume of pizzas.

The oven must not measurably increase the liability of RIT.

The oven must be able to be operated by an average college student with minimal training.

Level 6 : Primary Market Goals

The oven must be visually appealing and attractive to the public.

The oven must convey the senses and feelings of having a local pizzeria.

The oven must cook the pizzas to have similar properties of a bituminous coal oven.

Level 7 : Secondary Market Goals

This oven does not require the expertise of a professional chef

This oven does not necessarily cook other foods.

This oven is not self contained.

Designing a PID controller The absolute error.  This means how big is the difference between

the PV (process variable) and SP (set point)Absolute error is the "proportional" (P) component of the PID controller

The sum of errors over time is important and is called the "integral" (I) component of the PID controller. Every time we run the PID algorithm we add the latest error to the sum of errors.  In other words Sum of Errors = Error1 + Error2 + Error3 + Error4 + ...

Dead Time refers to the delay between making a change in the output and seeing the change reflected in the PV. The classical example is getting your oven at the right temperature.  When you first turn on the heat, it takes a while for the oven to "heat up".  This is the dead time. This is also referred to as the "derivative" (D) component of the PID controller

back

PID proportional (only) controllers are not very good because

there is an offset that has to be continually adjusted The integral portion of the PID controller accounts for the

offset problem in a proportional only controller Ziegler Nichols Tuning Method

1. Initially set the integral and derivative constants to zero -- proportional control only

2. Increase the proportional constant until you get a sinusoidal wave with a constant amplitude

3. For optimal P & I controller (no derivative), the proportional constant should be 0.45 times the proportional constant

4. The integral constant is 1.2 / period of the sinusoidal wave.

Thank you

Questions or Comments