Heat TransferNFE 111 DBH Summer 2020 What is
Heat Transfer-NFE 111 DBH –Summer 2020
What is Heat Transfer? • Heat transfer is the movement of heat energy from one substance to another.
What is Heat Transfer? • Heat (energy) always moves from a warmer substance to a cooler substance. Cold Hot
What is Heat Transfer? • Heat will continue to move until both substances are the same temperature. WCaom rl d WHaortm
What is Heat Transfer? • The greater the difference in temperature between the substances, the faster the heat will transfer.
What is Heat Transfer? • There are three types of heat transfer: –Conduction –Convection –Radiation
Examples Anti-Examples • You touch a black car in the summer and the heat from the car transfers into your hand. • A breeze makes you feel cooler because the wind transfers heat away from your body. • You feel the cold of a winter day because the cold air transfers into you. • Your Coke in a cooler gets cold because the cold from the ice moves into the Coke.
Conduction • Heat transfer by conduction is the transfer of heat through direct contact.
Conduction • Molecules transfer energy to the molecules next to them.
Conduction • The molecules do not have to be the same substance.
Example 1 The metal conducts heat from the cup of warm water to the cup of cool water.
Example 2 Your Coke becomes cold because the heat from the soda transfers into the ice, not the other way around.
No matter what it feels like, cold does not transfer into your body. What is really happening here? Why do you wear heavy clothes when it’s cold outside?
Radiation • Heat transfer by radiation is the transfer of heat through electromagnetic waves.
Radiation • There is no direct contact between the substances.
Example 1 Heat from the sun radiates through empty space to earth.
The heat from the campfire transfers into your marshmallow, giving you a yummy, gooey treat! (Direct contact between the fire and your marshmallow will ruin it!) Example 2
Convection • Heat transfer by convection is the transfer of heat through the fluid (liquids and gases) movement of currents.
Convection • Warm fluids rise, cool down, sink, and then are warmed again.
The radiator warms the room by warming the air around it. Then the warm air transfers heat to the rest of the room through convection.
As air above the road warms up, it rises and is replaced by cooler air, forming a convection current.
Conduction Convection Radiation This picture illustrates all three type of heat transfer. Can you identify them all?
GOOD LUCK
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