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The lecture slides of lecture Thermodynamics of the Modelling Course of Industrial Design of the TU Delft
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1Challenge the future
P‐L‐1
Thermodynamics
The Modelling Team Department of Design Engineering
Faculty of Industrial Design EngineeringDelft University of Technology
2Challenge the future
Aim
To develop basic understanding of thermodynamics;
To demonstrate that products with simple heat transfer behaviour can be modelled to provide useful data for designs;
To communicate with experts in their professional languages.
1
2
3
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The contents
• 0th law of thermodynamics• 1st law of thermodynamics
• Case study: The cool box
• Conduction• Convection• Radiation
Fundamentals 1
Heat transfer2
Thermal resistance network3
`Industrial applications4
Summary5
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FundamentalsThermodynamics is the study of transformations of energy
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0th law of thermodynamics
0th Law of thermodynamics
Object ATemperature T0
Object BTemperature T0
Object CTemperature T0
Thermal Equilibrium
Thermal Equilibrium
Thermal Equilibrium
If two systems (A, B) are in thermal equilibrium with a third system (C), they are also in thermal equilibrium with each other.
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0th law of thermodynamics
Thermal Equilibrium Thermal Equilibrium
No Energy transferNo Energy transfer
Temperature
Courtesy of http://iceworld2008.wordpress.com/
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Measuring temperature
Ref. http://en.wikipedia.org/wiki/ThermometerCourtesy of http://en.wikipedia.org/wiki/File:Pakkanen.jpg,
http://en.wikipedia.org/wiki/File:Thermocouple0002.jpg,http://www.kaz-europe.com/in/braun-thermoscan-3020/, Braun' is a registered trademark of Braun GmbH, Kronberg, Germany
Glass thermometer
Thermocouple
Infrared sensors
others
Thermo resistant
Gas thermometer
Langmuir probe
Etc.
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1th law of thermodynamics 1st Law of thermodynamics
Q System
Boundary Surroundings
W
ΔU
U Q - W
The change in the internal energy (ΔU) of a system is equal to the amount of energy added (Q) by heating the system minus the amount lost as a result of the work done (W) by the system to its surroundings
Ref. http://en.wikipedia.org/wiki/First_law_of_thermodynamics
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Conservation of energy
Any other energy change
Heat exchanged through the boundary
System
Sub‐system 1
Sub‐system 4Sub‐system 6
Sub‐system ...Sub‐system 2
Sub‐system 5Sub‐system 3
A: Area of the boundary
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The three classical states
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Latent heat – During the change of state
Q mL
SolidSolid liquidliquid GasGas
Courtesy of http://www.gabrielweinberg.com/blog/2010/11/code-icebergs.html
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Specific heat capacity – With in a state
SolidSolid liquidliquid GasGas
Q mC T In the differential form
q t Heat flow rate
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Heating & Cooling curve
Slope 2
Slope 1
Does slope 1 = slope 2?
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Specific heat capacity
Slope 2
Slope 1Does slope 1 = slope 2?
Substance Phase Cp [J/(g·K)] Volumetric heat capacity [J/(cm3·K)]
Gold solid 0.129 2.492
Silver solid 0.233 2.44
Copper solid 0.385 3.45
Iron solid 0.450 3.537
Carbon dioxide CO2 gas 0.839
Glass solid 0.840
Aluminium solid 0.897 2.422
Air (Sea level, dry, 0 °C) gas 1.004 0.001297
Nitrogen gas 1.040
Water at -10 °C (ice) solid 2.050 1.938
Water at 100 °C (steam) gas 2.080
Polyethylene (rotomolding grade) solid 2.303
Animal (and human) tissue mixed 3.500 3.7*
Water at 25 °C liquid 4.181 4.186
Hydrogen gas 14.30
Specific heat capacity of common materials
Ref. http://en.wikipedia.org/wiki/Heat_capacity
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Specific heat capacity: Case study
At a temperature of 15 °C, the heat required to raise the temperature of a water sample by 1 K (equivalent to 1 °C) is:
Key factors of radiation regarding heat transfer► 4186 joules per kilogram►This is the same amount of energy to lift a 1kg object to level of 418,6m (Potential energy of mechanics)
Case StudyCase Study1
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Heat transfer
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Three ways of heat transfer
1
2
In physics and thermodynamics, heat transfer is the process of energy transfer from one body or system due to thermal contact.
Heat transfer is defined as an energy transfer to a body in any other way than
due to work performed on the body.
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Three ways of heat transfer3 ways of heat transfer
Hot object
Cold Object
Conduction via solid contact
Convection via fluid contact
Radiation via electromagnetic waves
Courtesy of http://www.roasterproject.com/2010/01/heat-transfer-the-basics/
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Three ways of heat transfer
3 ways of heat transfer
Hot object
Cold Object
Conduction via solid contact
Convection via fluid contact
Radiation via electromagnetic waves
Temperature difference
Energy transfer happens due to
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Conduction
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Conduction: An case study
Case study: ConductionCase study: Conduction
373K
293K
A steel beamInitial Temperature 293K
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Conduction
( ) ( ( ) ( ))hot coldkAq t T t T tL
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Key parameters in conduction: K & A
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Thermal conductivity
Material Thermal conductivity k [W/(m·K)]Air 0.025Wood 0.04 - 0.4Polypropylene 0.25Rubber 0.16Cement, Portland 0.29Water (liquid) 0.6Thermal grease 0.7 - 3Glass 1.1Concrete, stone 1.7Ice 2Stainless steel 12.11 ~ 45.0Steel, Carbon 1% 43Aluminium 237 (pure) 120—180 (alloys)Gold 318Copper 401Silver 429
Thermal conductivity of common materials
Ref. http://en.wikipedia.org/wiki/Thermal_conductivity
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Thermal conductivity: A case study
AluminumAluminum
Structural steelStructural steel
Stainless steelStainless steel
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Thermal resistant: Conduction
( ) ( ( ) ( ))hot colddQ t kA T t T t
dt L
( ) ( ) ( ) ( )( ) hot cold hot coldT t T t T t T tdQ tLdt RkA
LRkA
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Understanding the thermal resistant
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Convection
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Natural convection
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Convection: Newton's law of cooling
( ) ( ( ) ( ))hot coldq t hA T t T t
h Fluid propertiesThe velocity of Fluid
The typical Value of h
Air: 10~100Water: 500 to 10,000
Ref. http://en.wikipedia.org/wiki/Heat_transfer_coefficient
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Thermal resistant: Convection
( ) ( ( ) ( ))hot colddQ t hA T t T t
dt
( ) ( ) ( ) ( )( )1
hot cold hot coldT t T t T t T tdQ tdt R
hA
1RhA
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Case study: Cool an iron ball
The air is heated
Heat loss Absorb heat
Iron cools down
Effect
Cause
1/ 0
SystemThe iron The air
How long will it take to cool an iron?1. In still air2. With ventilations
Courtesy of http://www.philips.com
Choice: Except the area that exposed to the air, the iron is well insulated.
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Case study: Cool an iron ball – The implementation
Ventilated Simulated by h=20
StillSimulated by h=10
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Radiation
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What is radiations
Courtesy of http://www.nuonsolarteam.nl
Radiation is a process in which energetic particles or energy or waves travel through a medium or space. There are two distinct types of radiation: ionizing and non‐ionizing.
Key factors of radiation regarding heat transfer► Frequency►Areas► Surface
RadiationRadiation
Courtesy of http://en.wikipedia.org/wiki/Radiation
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The black body & The grey body
4 4( ) ( ( ) ( ) )obj envq t T t T t A
4 4( ) ( ( ) ( ) )obj envq t T t T t A
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Thermal resistance network
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Thermal resistances regarding conduction & convection
( ) ( ) ( ) ( )( )1
hot cold hot coldT t T t T t T tdQ tdt R
hA
ConductionConduction
ConvectionConvection
( ) ( ) ( ) ( )( ) hot cold hot coldT t T t T t T tdQ tLdt RkA
A more complicated scenario
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Case study: thermal resistance network
Case study 2Case study 2
20 Watt
Inside air(20ºC initial)
OutsideAir (20ºC)
Aluminum
Insulator
Aluminum
Insulator
GoldGold
Case study 1Case study 1
20 Watt
Inside air(20ºC initial)
OutsideAir (20ºC)
Aluminum
Insulator
Aluminum
Insulator
Which one is hotter?Which one is hotter?
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Case study: thermal resistance network
Case study 2Case study 2Case study 1Case study 1
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Compose the thermal resistance network
22
1
gas
Rh A
13
1
LRK A
24
2
LRK A
51
1
liquid
Rh A
( )hT t ( )cT t
1 2 3 4 5 6
( ) ( )( ) h cT t T tq tR R R R R R
11
1
gas
Rh A
62
1
liquid
Rh A
If we don’t neglect the heat
capacity
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Case study: The cool box
Air in the oven
Layer 1 of the cool box
Layer 2 of the cool box
The air inside
Put a cool box in an oven whichis heated to 80 degrees (constant), What is the relations between the Inside temperature and the time? The initial temperature of the cooling box is 20 °C.
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Case study: The cooling box - Cause-effect
Layer 1is heated
Hot air
Effect
Cause
Layer 1is heated
Layer 2 is heated
Effect
Cause
Layer 2is heated
Air inside is heated
Effect
Cause
Cause effect: AbstractCause effect: Abstract
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Case study: Thermal resistances
1
/2
/2
/2
/2
1
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Case study: Cause-effect regarding layer 1
Cause-effect regarding hot air to layer 2
Layer1 temperature higher than layer 2
Heat transferred to layer 2 – q3
Heat transferred to layer 1 – q1
Hot air
Effect
Cause
Layer 1 absorb heat
Temperaturearise – q2
1 2 2 20
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Case study: Cause-effect regarding layer 2
Cause-effect regarding hot air to layer 2
Layer2 temperature higher than air
Heat transferred to air – q5
Heat transferred to layer 2 – q3
Hot air
Effect
Cause
Layer 2 absorb heat
Temperaturearise – q4
2 2 2 10
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Case study: Cause-effect regarding air
Cause-effect regarding hot air
Heat transferred to air – q5
Layer2 temperature higher than air
Effect
Cause
Air absorb heat
Temperaturearise – q6
2 10
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The implementation
T3T4
T2
T1
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Industrial design applications
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Conduction, Convention or Radiation?
Thermo-dynamics
& heat transfer
Courtesy ofhttp://en.wikipedia.org/wiki/Infrared_heater
http://en.wikipedia.org/wiki/Radiatorhttp://missouribeefcouncil.com/?m=201004
http://www.tefal.comhttp://www.daalderop.nl
http://www.ikea.nl
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Summary1
2
3
• Basic law of thermodynamics
• Heat transfer
• Case studies
To develop basic understanding of thermodynamics;
To demonstrate that products with simple heat transfer behaviour can be modelled to provide useful data for designs;
To communicate with experts in their professional languages.
1
2
3
52Challenge the future
Thank You
The Modelling Team Department of Design Engineering
Faculty of Industrial Design EngineeringDelft University of Technology