14.4 Heat Transfer Methods Equally as interesting as the effects of heat transfer on a system are the methods by which this occurs. Whenever there is a temperature difference, heat transfer occurs. Heat transfer may occur rapidly, such as through a cooking pan, or slowly, such as through the walls of a picnic ice chest. We can control rates of heat transfer by choosing materials (such as thick wool clothing for the winter), controlling air movement (such as the use of weather stripping around doors), or by choice of color (such as a white roof to reflect summer sunlight). So many processes involve heat transfer, so that it is hard to imagine a situation where no heat transfer occurs. Yet every process involving heat transfer takes place by only three methods: 1. Conduction is heat transfer through stationary matter by physical contact. (The matter is stationary on a macroscopic scale we know there is thermal motion of the atoms and molecules at any temperature above absolute zero.) Heat transferred between the electric bumer of a stove and the bottom of a pan is transferred by conduction. 2. Convection is the heat transfer by the macroscopic movement of a fluid. This type of transfer takes place in a forced-air furnace and in weather systems, for example. 3. Heat transfer by radiation occurs when microwaves, infrared radiation, visible light, or another form of electromagnetic radiation is emitted or absorbed. An obvious example is the warming of the Earth by the Sun. A less obvious example is thermal radiation from the human body. Convection around windows and doors (cold air) Radiation Convection Figure 14.12 In a fireplace, heat transfer occurs by all three methods: conduction, convection, and radiation. Radiation is responsible for most of the heat transferred into the room. Heat transfer also occurs through conduction into the room, but at a much slower rate. Heat transfer by convection also occurs through cold air entering the room around windows and hot air leaving the room by rising up the chimney. Conduction Convection (hot air)

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Chapter14: Heat And Heat Transfer Methods
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 Heat Transfer Methods
• Discuss the different methods of heat transfer.

14.4 Heat Transfer Methods
Equally as interesting as the effects of heat transfer on a system are the methods by which this occurs. Whenever there is a
temperature difference, heat transfer occurs. Heat transfer may occur rapidly, such as through a cooking pan, or slowly, such as
through the walls of a picnic ice chest. We can control rates of heat transfer by choosing materials (such as thick wool clothing
for the winter), controlling air movement (such as the use of weather stripping around doors), or by choice of color (such as a
white roof to reflect summer sunlight). So many processes involve heat transfer, so that it is hard to imagine a situation where no
heat transfer occurs. Yet every process involving heat transfer takes place by only three methods:
1. Conduction is heat transfer through stationary matter by physical contact. (The matter is stationary on a macroscopic
scale we know there is thermal motion of the atoms and molecules at any temperature above absolute zero.) Heat
transferred between the electric bumer of a stove and the bottom of a pan is transferred by conduction.
2. Convection is the heat transfer by the macroscopic movement of a fluid. This type of transfer takes place in a forced-air
furnace and in weather systems, for example.
3. Heat transfer by radiation occurs when microwaves, infrared radiation, visible light, or another form of electromagnetic
radiation is emitted or absorbed. An obvious example is the warming of the Earth by the Sun. A less obvious example is
thermal radiation from the human body.
Transcribed Image Text:14.4 Heat Transfer Methods Equally as interesting as the effects of heat transfer on a system are the methods by which this occurs. Whenever there is a temperature difference, heat transfer occurs. Heat transfer may occur rapidly, such as through a cooking pan, or slowly, such as through the walls of a picnic ice chest. We can control rates of heat transfer by choosing materials (such as thick wool clothing for the winter), controlling air movement (such as the use of weather stripping around doors), or by choice of color (such as a white roof to reflect summer sunlight). So many processes involve heat transfer, so that it is hard to imagine a situation where no heat transfer occurs. Yet every process involving heat transfer takes place by only three methods: 1. Conduction is heat transfer through stationary matter by physical contact. (The matter is stationary on a macroscopic scale we know there is thermal motion of the atoms and molecules at any temperature above absolute zero.) Heat transferred between the electric bumer of a stove and the bottom of a pan is transferred by conduction. 2. Convection is the heat transfer by the macroscopic movement of a fluid. This type of transfer takes place in a forced-air furnace and in weather systems, for example. 3. Heat transfer by radiation occurs when microwaves, infrared radiation, visible light, or another form of electromagnetic radiation is emitted or absorbed. An obvious example is the warming of the Earth by the Sun. A less obvious example is thermal radiation from the human body.
Convection
around windows
and doors
(cold air)
Radiation
Convection
Figure 14.12 In a fireplace, heat transfer occurs by all three methods: conduction, convection, and radiation. Radiation is responsible for most of the
heat transferred into the room. Heat transfer also occurs through conduction into the room, but at a much slower rate. Heat transfer by convection also
occurs through cold air entering the room around windows and hot air leaving the room by rising up the chimney.
Conduction
Convection (hot air)
Transcribed Image Text:Convection around windows and doors (cold air) Radiation Convection Figure 14.12 In a fireplace, heat transfer occurs by all three methods: conduction, convection, and radiation. Radiation is responsible for most of the heat transferred into the room. Heat transfer also occurs through conduction into the room, but at a much slower rate. Heat transfer by convection also occurs through cold air entering the room around windows and hot air leaving the room by rising up the chimney. Conduction Convection (hot air)
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