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