Heat transfer: thermodynamics

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3 methods of heat transfer

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Heat transfer: thermodynamics

  1. 1. Have you ever grabbed theHave you ever grabbed the handle of a hot metal pan?handle of a hot metal pan? What did you feel?What did you feel?
  2. 2. Boiling a pot of water on theBoiling a pot of water on the stove to cook some elbow pasta.stove to cook some elbow pasta. What did you notice to theWhat did you notice to the pasta?pasta?
  3. 3. We feel heat from the fire evenWe feel heat from the fire even though we are not touching it.though we are not touching it. How did it happen?How did it happen?
  4. 4. Heat TransferHeat Transfer  The transfer of thermal energy betweenThe transfer of thermal energy between substances due to difference in theirsubstances due to difference in their temperature.temperature.  HeatHeat is thermal energy that it is transmit fromis thermal energy that it is transmit from warmer object to the cooler matterwarmer object to the cooler matter Heat hot to cold
  5. 5. ConductionConduction ConvectionConvection RadiationRadiation Method of HeatMethod of Heat TransferTransfer
  6. 6. What is conduction? Is the transferof heat through a material by direct contact.
  7. 7. Prepare a coffee in same volume of hot 40ml water at 70Prepare a coffee in same volume of hot 40ml water at 70ºCºC after 2 mins. measure the temperature of the coffeeafter 2 mins. measure the temperature of the coffee using thermometer. Observe what happen?using thermometer. Observe what happen? Prepare a coffeePrepare a coffee Group 1 Group 2 Group 3 Styrofoam cup Metal glass Fiber glass
  8. 8. Thermal Conductivity  The thermal conductivity of a material describes how well the material conducts heat. Styrofoam cup Metal glassFiber glass
  9. 9. Conductors and InsulatorsConductors and Insulators  Conductors — Materials that allow heat to— Materials that allow heat to quickly pass throughout the material (suchquickly pass throughout the material (such as metals).as metals).  Insulators — Materials that do not allow— Materials that do not allow heat to quickly pass throughout a materialheat to quickly pass throughout a material (such as wood or plastic).(such as wood or plastic).  This mainly deals with the movement ofThis mainly deals with the movement of electrons.electrons.  Metals have a “sea of electrons” that allows forMetals have a “sea of electrons” that allows for quick heat transfer.quick heat transfer.
  10. 10. Heat is transferred to your bodyHeat is transferred to your body because it is direct contact with abecause it is direct contact with a body that is at a higherbody that is at a higher temperature.temperature. Imagine that you are walkingImagine that you are walking barefoot across asphalt onbarefoot across asphalt on scorching summer day. Whyscorching summer day. Why do this object feels hot todo this object feels hot to you?you?
  11. 11. {{ {{ We feelWe feel discomfortdiscomfort When you grabbed theWhen you grabbed the handle of hot metal pan.handle of hot metal pan. What would you feel?What would you feel?
  12. 12. Boiling a pot of water on theBoiling a pot of water on the stove to cook elbow pasta.stove to cook elbow pasta. What do you notice to the pasta when it suddenly drop to the boiled water? The pasta rises to the top of the pan gets pushed to the side and sink to the bottom it rises.
  13. 13.  The cooler water at the top sinks and theThe cooler water at the top sinks and the warmer water dense, less dense water rises towarmer water dense, less dense water rises to the top.the top.  As the cooler ware sinks it heats up and movesAs the cooler ware sinks it heats up and moves back to the top.back to the top.  There is a reversible process of hot and warmThere is a reversible process of hot and warm water. The water being heated up and thewater. The water being heated up and the warmer water sinks in a continuouslywarmer water sinks in a continuously movement .movement . How it was happen?How it was happen?
  14. 14. What is convection?What is convection?  is the transfer ofis the transfer of heat by theheat by the motion of liquidsmotion of liquids and gases.and gases.
  15. 15. What is radiation?What is radiation?  is heat transfer by electromagneticis heat transfer by electromagnetic waves.waves. Is heat transfer that travels throughIs heat transfer that travels through empty spaceempty space It does not require a medium
  16. 16.  The heat comingThe heat coming from the sunfrom the sun emitted by theemitted by the boy, that feels himboy, that feels him warm.warm.  ElectromagneticElectromagnetic radiation giveradiation give heats to the bodyheats to the body of the Earth.of the Earth. Sun the heat coming from the sun give us a temperature or energy negligible by the air resistance.
  17. 17. How will radiation method explain theHow will radiation method explain the picture?picture? Branches preheated by convection and radiation Brush preheated by radiation Log preheated by conduction/radiation Duff preheated by conduction/radiation Tree trunk preheated by radiation
  18. 18.  Is the transfer of heatIs the transfer of heat through directthrough direct contact with thecontact with the material.material.  is the transfer of heatis the transfer of heat by the motion ofby the motion of liquids and gases.liquids and gases.  Is the transfer of heatIs the transfer of heat through emptythrough empty space.space. Radiation Conduction Convection
  19. 19. Convection MethodConvection Method  Cooler temperature is denser than theCooler temperature is denser than the warm one, that is why it cooler atwarm one, that is why it cooler at night than in day timenight than in day time
  20. 20.  In ¼ sheet of paper explain briefly andIn ¼ sheet of paper explain briefly and accurately the following: (5 points each)accurately the following: (5 points each)  1. Explain the water cycle and relate it in1. Explain the water cycle and relate it in heat transfer.heat transfer.  2. How energy is transfer in the process of:2. How energy is transfer in the process of:  A. ConductionA. Conduction  B. ConvectionB. Convection  C. RadiationC. Radiation EssayEssay
  21. 21.  Define thermal conductivity.Define thermal conductivity.  List some thermal conductivities ofList some thermal conductivities of different materials.different materials.  What are the different equations to getWhat are the different equations to get radiation rate?radiation rate? AssignmentAssignment
  22. 22. PREPARED BY:PREPARED BY: KAREN A. ADELANKAREN A. ADELAN BSE 3BSE 3  Thank you!!!!!MabuhayThank you!!!!!Mabuhay

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