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HEAT CONVECTION

HEAT CONVECTION. Done by: Jonathan Soh Tjai Kang Jie Ng Jing Rou Quek Yan Ching Ong Rui Zhi. What is Convection?. Convection is the transfer of heat by the circulation of currents from one region to another in a liquid or a gas. Description of mechanism.

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HEAT CONVECTION

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  1. HEAT CONVECTION Done by: Jonathan Soh Tjai Kang Jie Ng Jing Rou Quek Yan Ching Ong Rui Zhi

  2. What is Convection? Convection is the transfer of heat by the circulation of currents from one region to another in a liquid or a gas.

  3. Description of mechanism • Heat convection is a mechanism, or type of heat transport in which the fluid motion is not generated by any external source (like a pump, fan, suction device, etc.) but only by density differences in the fluid occurring due to temperature gradients. • In heat convection, fluid surrounding a heat source receives heat, becomes less dense and rises. The surrounding, cooler fluid then moves to replace it. This cooler fluid is then heated and the process continues, forming a convection current.

  4. Diagrams ( 1 ) The simplest convection currents are exampled by these beakers of liquid. Hot fluids rise and cold fluids sink because when a fluid is heated, it expands and becomes less dense than the surrounding cooler fluid.

  5. Diagrams ( 2 ) The air currents around the cake layers baking in the oven . Convection currents move heated air around cake surfaces to aid in baking and browning.

  6. Examples of selected mode of heat transfer in daily lives Warm air rising from all surfaces of radiator . Warm air rising from register. Warm air rising from chimney.

  7. Another Example If you were to fill a bathtub full of water and then realize that it was too hot, you would add more cold water. If you can relate to such an instance, you know that the cold water is often at the faucet end of the tub, while the hot water stays at the other end. If you swirl the water around though, it mixes. The hot water transfers heat to the cold water by heat convection due to the swirling.

  8. For Your Information • The formula for convection is the Grashof number: • g = acceleration due to Earth's gravity • β = volumetric thermal expansion coefficient • Ts = source temperature • T∞ = quiescent temperature • L = characteristic length • ν = kinematic viscosity

  9. Questions 1.In natural convection, fluid surrounding a heat source receives heat, becomes dense and . Which are the words which are most suitable to filled in the first and second blanks respectively? A) more, rises B) less, rises C) more, sinks D) less, sinks

  10. 2. What example of heat transmission is this? A) Heat conduction B) Heat radiation C) Heat convection D) Boiling

  11. Which of the below is an external source of convection? A) Microscope B) Test tube C) Bunsen burner D) Pump

  12. Credits Done by:Tjai Kang Jie (39) Jonathan Soh (36) Ng Jing Rou (11) Quek Yan Ching (18) Ong Rui Zhi (16) Resources/Websites: www. wikipedia.org www. google.com www. food.oregonstate.edu/learn/energy.html Science Textbook 2

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