Lecture Slides: Lecture Thermodynamics

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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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Lecture Slides: Lecture Thermodynamics

  1. 1. P‐L‐1 Thermodynamics The Modelling Team  Department of Design Engineering Faculty of Industrial Design Engineering Delft University of Technology Challenge the future 1
  2. 2. Aim 3 2 1 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. Challenge the future 2
  3. 3. The contents Fundamentals • 0th law of thermodynamics • 1st law of thermodynamics Thermal resistance network • Case study: The cool box Summary 1 2 3 4 Heat transfer • Conduction • Convection • Radiation Industrial applications ` 5 Challenge the future 3
  4. 4. Fundamentals Thermodynamics is the study of transformations of energy Challenge the future 4
  5. 5. 0th law of thermodynamics 0th Law of thermodynamics If two systems (A, B) are in thermal equilibrium with a third system (C), they are also in thermal equilibrium with each other. Object C Temperature T0 Thermal Equilibrium Object A Temperature T0 Thermal Equilibrium Thermal Equilibrium Object B Temperature T0 Challenge the future 5
  6. 6. 0th law of thermodynamics Thermal Equilibrium  Temperature No Energy transfer Courtesy of http://iceworld2008.wordpress.com/ Challenge the future 6
  7. 7. Measuring temperature Glass  thermometer Thermo couple Infrared  sensors others Thermo resistant  Gas thermometer Langmuir probe Etc. Ref. http://en.wikipedia.org/wiki/Thermometer Courtesy 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 Challenge the future 7
  8. 8. 1th law of thermodynamics 1st Law of thermodynamics 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 ΔU Q Boundary System W Surroundings U  Q - W Ref. http://en.wikipedia.org/wiki/First_law_of_thermodynamics Challenge the future 8
  9. 9. Conservation of energy Heat exchanged through the boundary Any other energy change Sub‐system 1 Sub‐system 6 Sub‐system 4 Sub‐system 2 Sub‐system 3 Sub‐system ... Sub‐system 5 A: Area of the boundary System Challenge the future 9
  10. 10. The three classical states Challenge the future 10
  11. 11. Latent heat – During the change of state Q  mL Solid liquid Gas Challenge the future 11 Courtesy of http://www.gabrielweinberg.com/blog/2010/11/code-icebergs.html
  12. 12. Specific heat capacity – With in a state liquid Solid Q  mC T Gas In the differential form Heat flow rate qt Challenge the future 12
  13. 13. Heating & Cooling curve Slope  1 Does slope 1 = slope 2? Slope  2 Challenge the future 13
  14. 14. Specific heat capacity Specific heat capacity of common materials 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 solid 0.897 Aluminium Slope 1 Air (Sea level, dry, 0 °C) 2.422 Does slope 1 = slope 2? gas 1.004 0.001297 Nitrogen gas 1.040 Water at -10 °C (ice) solid 2.050 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 Challenge the future 1.938 Slope 2 14 Ref. http://en.wikipedia.org/wiki/Heat_capacity
  15. 15. Specific heat capacity: Case study 1 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) Challenge the future 15
  16. 16. Heat transfer Challenge the future 16
  17. 17. Three ways of heat transfer 1 In physics and thermodynamics, heat transfer is the process of energy transfer from one body or system due to thermal contact. 2 Heat transfer is defined as an energy transfer to a body in any other way than due to work performed on the body. Challenge the future 17
  18. 18. Three ways of heat transfer 3 ways of heat transfer Conduction via solid contact Convection via fluid contact Hot object Radiation via electromagnetic waves Cold Object Courtesy of http://www.roasterproject.com/2010/01/heat-transfer-the-basics/ Challenge the future 18
  19. 19. Three ways of heat transfer 3 ways of heat transfer Conduction via solid contact Convection via fluid contact Hot object Radiation via electromagnetic waves Cold Object Energy transfer happens due to  Temperature difference Challenge the future 19
  20. 20. Conduction Challenge the future 20
  21. 21. Conduction: An case study Case study: Conduction 373K 293K A steel beam Initial Temperature 293K Challenge the future 21
  22. 22. Conduction q (t )  kA (Thot (t )  Tcold (t )) L Challenge the future 22
  23. 23. Key parameters in conduction: K & A Challenge the future 23
  24. 24. Thermal conductivity Thermal conductivity of common materials Material Thermal conductivity k [W/(m·K)] Air Wood Polypropylene 0.025 0.04 - 0.4 0.25 Rubber 0.16 Cement, Portland 0.29 Water (liquid) 0.6 Thermal grease 0.7 - 3 Glass 1.1 Concrete, stone 1.7 Ice 2 Stainless steel 12.11 ~ 45.0 Steel, Carbon 1% 43 Aluminium 237 (pure) 120—180 (alloys) Gold 318 Copper 401 Silver 429 Ref. http://en.wikipedia.org/wiki/Thermal_conductivity Challenge the future 24
  25. 25. Thermal conductivity: A case study Aluminum Structural steel Stainless steel Challenge the future 25
  26. 26. Thermal resistant: Conduction dQ(t ) Thot (t )  Tcold (t ) Thot (t )  Tcold (t )   L dt R kA dQ(t ) kA  (Thot (t )  Tcold (t )) dt L L R kA Challenge the future 26
  27. 27. Understanding the thermal resistant Challenge the future 27
  28. 28. Convection Challenge the future 28
  29. 29. Natural convection Challenge the future 29
  30. 30. Convection: Newton's law of cooling q (t )  hA(Thot (t )  Tcold (t )) h The typical Value of h Fluid properties The velocity of Fluid Air: 10~100 Water: 500 to 10,000 Ref. http://en.wikipedia.org/wiki/Heat_transfer_coefficient Challenge the future 30
  31. 31. Thermal resistant: Convection dQ(t ) Thot (t )  Tcold (t ) Thot (t )  Tcold (t )   1 dt R hA dQ (t )  hA(Thot (t )  Tcold (t )) dt 1 R hA Challenge the future 31
  32. 32. Case study: Cool an iron ball The iron How long will it take to cool an iron? 1. In still air 2. With ventilations System The air Choice: Except the area that exposed to the air, the iron is well insulated. Cause Iron cools down The air is heated Effect Heat loss Absorb heat 0 1/ Courtesy of http://www.philips.com Challenge the future 32
  33. 33. Case study: Cool an iron ball – The implementation Still Simulated by h=10 Ventilated Simulated by h=20 Challenge the future 33
  34. 34. Radiation Challenge the future 34
  35. 35. What is radiations Radiation 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  Courtesy of http://www.nuonsolarteam.nl Courtesy of http://en.wikipedia.org/wiki/Radiation Challenge the future 35
  36. 36. The black body & The grey body q (t )   (Tobj (t ) 4  Tenv (t ) 4 ) A q (t )   (Tobj (t ) 4  Tenv (t ) 4 ) A Challenge the future 36
  37. 37. Thermal resistance network Challenge the future 37
  38. 38. Thermal resistances regarding conduction & convection Conduction dQ(t ) Thot (t )  Tcold (t ) Thot (t )  Tcold (t )   L dt R kA A more  complicated  scenario Convection dQ(t ) Thot (t )  Tcold (t ) Thot (t )  Tcold (t )   1 dt R hA Challenge the future 38
  39. 39. Case study: thermal resistance network Case study 1 Case study 2 Insulator Outside Air (20ºC) 20 Watt Insulator Aluminum Aluminum Inside air (20ºC initial) Insulator Outside Air (20ºC) 20 Watt Insulator Aluminum Aluminum Inside air (20ºC initial) Gold Gold Which one is hotter? Challenge the future 39
  40. 40. Case study: thermal resistance network Case study 1 Case study 2 Challenge the future 40
  41. 41. Compose the thermal resistance network Tc (t ) Th (t ) R1  1 hgas1 A R2  1 L R3  1 hgas 2 A K1 A q(t )  1 1 L2 R6  R5  R4  hliquid 2 A hliquid 1 A K2 A Th (t )  Tc (t ) R1  R2  R3  R4  R5  R6 If we don’t  neglect the heat  capacity  Challenge the future 41
  42. 42. Case study: The cool box Air in the oven Put a cool box in an oven which is 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.  Layer 1 of the cool box  Layer 2 of the cool box  The air inside Challenge the future 42
  43. 43. Case study: The cooling box - Cause-effect Cause effect: Abstract Cause Cause Cause Hot air Layer 1 is heated Layer 2 is heated Effect Effect Effect Layer 1 is heated Layer 2 is heated Air inside is heated Challenge the future 43
  44. 44. Case study: Thermal resistances 1 /2 /2 /2 /2 1 Challenge the future 44
  45. 45. Case study: Cause-effect regarding layer 1 Cause-effect regarding hot air to layer 2 Cause Layer 1 absorb heat Hot air Layer1 temperature higher than layer 2 Effect Temperature arise – q2 Heat transferred to layer 1 – q1 Heat transferred to layer 2 – q3 0 1 2 2 Challenge the future 2 45
  46. 46. Case study: Cause-effect regarding layer 2 Cause-effect regarding hot air to layer 2 Cause Layer 2 absorb heat Hot air Layer2 temperature higher than air Effect Heat transferred to layer 2 – q3 Temperature arise – q4 Heat transferred to air – q5 0 2 2 2 Challenge the future 1 46
  47. 47. Case study: Cause-effect regarding air Cause-effect regarding hot air Cause Air absorb heat Layer2 temperature higher than air Effect Heat transferred to air – q5 Temperature arise – q6 0 2 1 Challenge the future 47
  48. 48. The implementation T1 T4 T3 T2 Challenge the future 48
  49. 49. Industrial design applications Challenge the future 49
  50. 50. Conduction, Convention or Radiation? Thermodynamics & heat transfer Courtesy of http://en.wikipedia.org/wiki/Infrared_heater http://en.wikipedia.org/wiki/Radiator http://missouribeefcouncil.com/?m=201004 http://www.tefal.com http://www.daalderop.nl http://www.ikea.nl Challenge the future 50
  51. 51. Summary 1 • Basic law of thermodynamics  2 • Heat transfer 3 • Case studies 3 2 1 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. Challenge the future 51
  52. 52. Thank You The Modelling Team  Department of Design Engineering Faculty of Industrial Design Engineering Delft University of Technology Challenge the future 52

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