ThermoAcoustic Refrigeration
ThermoAcoustic
Refrigeration Generation
Engineering Team
Team Members

Trevor Bourgeois
Mike Horne
Peter Smith
Erin MacNeil

Supervisor – Dr. Murat Koksal



Design Description

Thermoacoustic Refrigerator
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–
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
Unpressurized System
Air as Gas Medium
Loudspeaker as Acoustic Driver
Variable design (stacks)
Advantages of Thermoacoustic Refrigeration
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–
No Environmentally-Harmful Refrigerants
Mechanically Simple
Summary of Fall Term


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Work to understand Theory
Development of Mathematical Model
Construction of two Prototypes
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
Standing wave created
No DT
Identification of Stack as most important
component
Main Prototype Components
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Speaker
Gas
Tube
Stack
Heat Exchangers
Speaker

Considerations
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–

Power Capacity
Frequency Response
Choice
–
–
–
10 inch
Operates At Low
Frequencies (100 Hz)
400 W Maximum Power
Gas Medium

Considerations
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–
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Physical Properties
Sealing
Cost
Choice
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–
Air
Atmospheric Pressure
Tube

Considerations
–
–
–
–
–

Length
Diameter
Sound Reflection
Low Acoustic Losses
Sound Transmission
Choice
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–
1.5” PVC Tube
Flat End
c
l
2f
Stack

Considerations
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–
–
–
–
–

Gap Size
Material properties
Material thickness
Location
Length
Does not impede wave
Choice
–
–
Paper
Aluminum Screen
Heat Exchangers

Considerations
–
–

Material
Type
Choice
–
–
Aluminum
Water Circulated
Stack



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Solid Porous Material
Give And Takes Heat From Gas
Heat Transfer
DT Across
Design Considerations


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

Gap Size
Solid Thickness
Position
Length
Ability Of Sound To Pass Through
Physical Properties
Stack Designs
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Foil
Paper
Foam
Lexan
Screen
Foil
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
Aluminum Foil
Crimped
Rolled Up Around Centre
Post
Foil
ALUMINUM FOIL STACK
Units
Value
mm
Outer Diameter 47.86
mm
Length 63.63
mm
Gap Size 1.07
mm
Foil Thickness 0.1
mm
Center Post Diameter 2.42
W/m*K
Thermal Conductivity 180
3
Density 2790
Kg/m
Paper


Couragrated Paper
Rolled Up
Paper
PAPER STACK
Value
Outer Diameter 49.8
Length 55.4
Gap Size 1.44
Paper Thickness 0.12
Thermal Conductivity 0.18
Density 930
Units
mm
mm
mm
mm
W/m*K
3
Kg/m
Foam



Open Cell Foam
Cut To Approximate
Shape
Tape To Hold Two
Pieces Together
Foam
PLASTIC FOAM STACK
Value
Outer Diameter 51.14
Length 54.04
Gap Size 0.5
Units
mm
mm
mm
Lexan



Strips Thin Lexan
Monofilament Fishing
Line Used As Spacers
Rolled Up Around A
Pencil
Lexan
LEXAN STACK
Value
Outer Diameter (no tape) 45.18
Outer Diameter (with tape) 48.71
Length 51.9
Gap Size 0.4
Lexan Thickness 0.2032
Center Post Diameter 7.03
Thermal Conductivity 0.18
Density 1119
Units
mm
mm
mm
mm
mm
mm
W/m*K
Kg/m^3
Screen
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Aluminum Screen
Punch To Cut Circles
Many Layers
Screen
ALUMINUM SCREEN STACK
Value
Units
Outer Diameter 50.56
mm
Length
51
mm
Gap Size 1.69
mm
Wire Diameter 0.24
mm
Thermal Conductivity 180
W/m*K
Density 2790 Kg/m^3
Experimental Setup
Pressure Transducers
Thermocouples
Maximum Pressure vs. Frequency
Stack Pressure at 26.5 W vs Frequency
7000
Pressure (Pa)
6000
5000
4000
3000
2000
1000
110
130
150
170
190
210
230
250
Foam
Aluminum Screen
Frequency (Hz)
Paper
Lexan
Aluminum Foil
Stack Temperature vs. Time @130Hz
Stack Temperatures vs. Time
50
45
Temp(degC)
40
35
30
25
20
15
10
0
10
20
30
40
50
60
70
80
Time(s)
Screen Hot Side
Screen Cold Side
Foam Hot Side
Foam Cold Side
Lexan Hot Side
Lexan Cold Side
Paper Hot Side
Paper Cold Side
Foil Hot Side
Foil Cold Side
Ambient
90
Stack Temperatures at 36 Watts
Aluminum
Screen
44 C
Lexan
Aluminum
Foil
Paper
Foam
48 C
36 C
42 C
44 C
24 C
25 C
18 C
21 C
26 C
Temperature Difference
30 C
18 C
15 C
18 C
19 C
Temperature vs. Frequency
Stack Temperature vs Frequency
Temperature Difference
30.00
25.00
20.00
15.00
10.00
5.00
0.00
110
130
150
170
190
210
230
250
Frequency (Hz)
Paper
Aluminum Foil
Foam
Aluminum Screen
Lexan
Temperature vs. Speaker Power
Tem perature Difference
(degC)
Power vs. Stack Temperature Difference
40
35
30
25
20
15
10
5
0
0
60
40
20
80
Power (W)
ALUMINUM FOIL
FOAM
LEXAN
PAPER
ALUMINUM SCREEN
Temperature vs. Radial Distance
46.4
46.7
41.7
46.4
39.2
39.5
Stack Ranking
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Pairwise Ranking Method
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Important Attributes Determined
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Ranked According to Importance For Each Stack
Attribute
Compatibility
Cost
LTCS
Manu.
P/E
DT
Compatibility ----------0
0
0
0
2
Cost
2
----------2
1
1
2
LTCS
2
0
----------0
0
2
Manu.
2
1
2
----------1
2
P/E
2
1
2
1
----------2
0
0
0
0
0
----------DT
Sum
8
2
6
2
2
10
Weight
0.267
0.067
0.2
0.067
0.067
0.333
Stack Ranking

Aggregate Scoring System
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10 = Highly Effective 0 = Not Effective
Attribute
Compatibility
Cost
LTCS
Manu.
P/E
DT
Score
Al Screen
6
6
9
7
5
9
7.605
Paper
5
8
8
9
5
9
7.406
Foam
7
8
2
10
4
4
5.075
Lexan
5
8
6
1
3
5
5.004
Al Foil
4
8
3
4
4
6
4.738
Weight
0.267
0.067
0.2
0.067
0.067
0.333
1
Stack Temperature Results
Heat Exchanger
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Cold Side
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Side temperature
Heat Exchanger
To use theHot
cold
produced and cool a cold space
Hot Side
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Wooden Cartridge
Experiments: heat conduction from
hot side to cold side
If we cool Cold
theSide
hotHeat
side,
we will be
Exchanger
able to obtain a colder cold side
Heat Exchanger Evolution
Four Bolt Holes
Floating fastener assembly
Heat exchanger must be
compatible with our
present design
Center Hole
To hold part of the stack
Heat Exchanger Evolution
Drill Thru Channel Design
Manufacturing
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Drill three thru holes
Intersect at right angles
Four ends tapped and plugged
Front two ends tapped for a
1/8” NPT thread
Heat Exchanger Evolution
Drill Thru Channel Design
Pros: Few manufacturing steps
Low cost operation
Cons: Long enough drill bit
Possible tool wandering
Heat Exchanger Evolution
Tube Flow Design
Manufacturing
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CNC machine a pocket for the
tube insert
Tube insert
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Tube Insert
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Machined block
Connects five 1/16” diameter
tubes.
Seal with silicone
Drill and tap two ends for a 1/8”
NPT thread
Heat Exchanger Evolution
Tube Flow Design
Pros: Greater heat transfer rate
Cons: Higher manufacturing costs
Longer build time
Sealing
1
Larger pump ( P  4 )
R
Heat Exchanger Evolution
CNC Milled Channel Design
Manufacturing
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CNC – end mill curved profile
Thickness of wall is 2mm
 max
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2
a
Pi  Po 
 12  y  2
2
a b
Front two ends drill and tap for
a 1/8” NPT thread
Heat Exchanger Evolution
CNC Milled Channel Design
Pros: Better rate of heat transfer
than the first design.
Lower machining costs than
the second design.
Cons: Sealing
Heat Exchanger Setup
Hot Side Heat Exchanger
Wooden Cartridge
Reservoir
Cold Side Heat Exchanger
Large Reservoir to keep
water at a constant
temperature
Heat Exchanger Setup
Hot Side Heat Exchanger
Represents our refrigerating capacity
Wooden Cartridge
Cold Side Heat Exchanger
Cold
Space
Heat Exchanger Experiments
H.E. Experiment (Aluminum Screen)
50
+ve Slope
45
Temperature (°C)
40
35
-ve Slope
30
25
20
+ve Slope
15
10
-ve Slope
5
0
0
20
40
60
80
100
Time (s)
Cold Side - No Pump
Cold Side - Hot Side Pump
Hot Side - No Pump
Hot Side - Hot Side Pump
Ambient
120
5.5°C
Heat Exchanger Experiments
4.8°C in 30 minutes
1.2°C in 30 minutes
Cold
Space
Cold
Space
Cooling From Prototype
Cooling from atmosphere
Heat Exchanger Experiments
3.6°C in 30 minutes
Heat removal rate of 16.7W
Cold
Space
Cooling From Prototype
Speaker drawing power at 90.25W
COP = 0.185
Comparison with Project Goals
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Less than ½ meter long, less than 20lb
DT of 5-10ºC below ambient (17 º C)
Sound Insulation
Introduce Heat Exchangers
10-20 Watts Cooling (16.7 W)
Build for less than $2,000.00
User’s Manual
Recommendations

Theoretical Work
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Calculate Operating Frequency
Heat Exchanger Calculations
Recommendations
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Theoretical Work
Experimentation
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Stack Gap Size
Stack Location
Stack Length
Recommendations
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Theoretical Work
Experimentation
Equipment Improvements
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Pressure Transducers
Signal Generator
Recommendations
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Theoretical Work
Experimentation
Equipment Improvements
Design Changes
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Speaker Funneling
Helium
Heat Exchangers
Insulation (thermal, acoustic)
Mechanical Resonator
Term Summary
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Built prototype with variable stacks
Performed comprehensive set of experiments
Determined optimum stack
Designed Heat Exchanger
Heat Exchanger tests performed
16.7 W cooling power
Coefficient of Performance 0.185
Thank You

Questions??