AN_892| Application Note
AN-892 APPLICATION NOTE
One Technology Way P.O. Box 9106 Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 Fax: 781.461.3113 www.analog.com
Temperature Measurement Theory and Practical Techniques
By Donal McNamara
HEAT TRANSFER THEORY
The transfer of heat is normally from a high temperature object to a lower temperature object. Heat transfer from a cold region to a hot region can be done by forcing the system (refrigerators, for example) to perform the energy transfer. Heat transfer is accomplished by three basic methods. Conduction Convection Radiation
WARM AIR RISES
COOLER AIR DROPS AND REPLACES THE WARMER AIR
HEATER
Conduction
Conduction is the most common means of heat transfer in a solid. On a microscopic scale, conduction occurs as hot, rapidly moving or vibrating atoms and molecules interacting with neighboring atoms and molecules, transferring some of their energy (heat) to these neighboring atoms.
CROSS SECTIONAL AREA = A
Figure 2. Convection
Radiation
Radiation is the only form of heat transfer that can occur in the absence of any form of medium and as such, is the only means of heat transfer through a vacuum. Thermal radiation is a direct result of the movements of atoms and molecules in a material. Because the amount of emitted radiation increases with increasing temperature, a net transfer of energy from higher temperatures to lower temperatures results.
HOT
HEAT FLOW L
COLD
06506-001
Figure 1. Conduction
Convection
Convection is usually the dominant form of heat transfer in liquids and gases. This is a term used to characterize the combined effects of conduction and fluid flow. In convection, heat content transfer occurs by the movement of hot or cold portions of the fluid together with heat transfer by conduction.
Figure 3. Radiation
Rev. 0 | Page 1 of 8
06506-003
06506-002
AN_892 Application Note analog Download PDF
Add this permalink to your bookmarks for future download of AN_892 ApplicationNote
Permalink: http://application.emcelettronica.com/analog/AN_892
