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Topic: Law of heat conduction


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In the News (Tue 22 Jul 14)

  
  Heat conduction - Wikipedia, the free encyclopedia
Heat transfer is always directed from a higher to a lower temperature.
The law of heat conduction also know as Fourier's law states that the time rate of heat flow Q through a slab (or a portion of a perfectly insulated wire, as shown in the figure) is proportional to the gradient of temperature difference:
When heat is being conducted from one fluid to another through a barrier, it is sometimes important to consider the conductance of the thin film of fluid which remains stationary next to the barrier.
en.wikipedia.org /wiki/Newton's_law_of_cooling   (413 words)

  
 Hail Info: HailStorms Prevention, Information and Photo Galleries of Hail Stones and Storms. Weather Encyclopedia   (Site not responding. Last check: 2007-10-20)
For example, heat is transferred predominantly by conduction through the brick wall of a house, a pan of water on a stove is largely heated by convection, and the Earth receives heat from the Sun almost wholly by radiation.
This law states that the rate at which heat is conducted through a body per unit cross-sectional area is proportional to the negative of the temperature gradient existing in the body.
Wien's displacement law, named after the German physicist Wilhelm Wien, is a mathematical expression of this observation and states that the wavelength of maximum energy, expressed in micrometres (millionths of a metre), multiplied by the temperature of the body in kelvins, is equal to a constant, 2,878.
www.hailinfo.com /info/h.php3?name=heat_transfer.html   (1525 words)

  
 Heat conduction -- Facts, Info, and Encyclopedia article   (Site not responding. Last check: 2007-10-20)
Conduction is the transfer of (A form of energy that is transferred by a difference in temperature) heat or electric current from one substance to another by direct contact.
In the case of heat, the transfer is always from a higher (The degree of hotness or coldness of a body or environment (corresponding to its molecular activity)) temperature to a lower temperature.
When heat is being conducted from one fluid to another through a barrier, it is sometimes important to consider the conductance of the thin (Photographic material consisting of a base of celluloid covered with a photographic emulsion; used to make negatives or transparencies) film of fluid which remains stationary next to the barrier.
www.absoluteastronomy.com /encyclopedia/h/he/heat_conduction.htm   (539 words)

  
 Heat Conduction
and the heat flow are, in fact, oppositely directed, for the gradient (by definition) is in the direction of increasing temperature, while heat flows from higher to lower temperatures.
Until now we have used the phrase "heat flow" in an intuitive sense; but to formulate the basic law of heat conduction, equation (2.1) below, we must be more precise.
, and that the heat flux is proportional to the magnitude of the gradient.
www.ibiblio.org /links/devmodules/heatflow/compat/page12.html   (192 words)

  
 Heat equation   (Site not responding. Last check: 2007-10-20)
Solutions of the heat equation are characterized by a gradual smoothing of the initial temperature distribution by the flow of heat from warmer to colder areas of an object.
Heat conduction in non-homogeneous anisotropic media In general, the study of heat conduction is based on several principles.
Heat flow is a form of energy flow, and as such it is meaningful to speak of the time rate of flow of heat into a region of space.
read-and-go.hopto.org /Thermodynamics/Heat-equation.html   (484 words)

  
 Heat Transfer
The transfer of heat is normally from a high temperature object to a lower temperature object.
Conduction is heat transfer by means of molecular agitation within a material without any motion of the material as a whole.
Convection is heat transfer by mass motion of a fluid such as air or water when the heated fluid is caused to move away from the source of heat, carrying energy with it.
hyperphysics.phy-astr.gsu.edu /hbase/thermo/heatra.html#c1   (441 words)

  
 Conductive Heat Transfer
Heat transfer is the study of energy movement in the form of heat which occurs in many types of processes.
It can be done by conduction (within one solid or between two solids in contact), by convection (between two fluids or a fluid and a solid in direct contact with the fluid), by radiation (transmission by electromagnetic waves through space) or by combination of the above three methods.
Heat transfer is said to be at steady-state when the quantity of heat flowing from one point to another by unit time is constant and the temperatures at each point in the system do not change with time.
www.afns.ualberta.ca /Hosted/FoodEng/ht/conduct.html   (555 words)

  
 Heat conduction   (Site not responding. Last check: 2007-10-20)
Conduction is the transfer of heat or electric current from one substance to another by direct contact.
In the case of heat, the transfer is always from a higher temperature to a lower temperature.
A is the transversal surface area, x is the thickness of the body of matter through which the heat is passing, K is a conductivity constant dependent on the nature of the material and its temperature, and T is the temperature difference through which the heat is being transferred.
read-and-go.hopto.org /Thermodynamics/Heat-conduction.html   (455 words)

  
 Heat Transfer   (Site not responding. Last check: 2007-10-20)
Thermal conductivity of the unknown sample is determined from the temperature gradient and the heat flow, which is known for the two brass disks.
Heat conduction is a good fit to temperature gradients in the lithosphere but not the asthenosphere.
Conductive temperature profiles are a good fit to observed temperatures in the continental crust if radioactive elements are concentrated in the upper part of the crust.
www.geol.lsu.edu /Faculty/Nunn/gl7065/Chp4_notes.html   (708 words)

  
 Heat and First Law of Thermodynamics
This energy is called heat, or thermal energy, and the term "heat flow" refers to an energy transfer as a consequence of a temperature difference.
The heat capacity, C’, of a substance is defined as the amount of heat required to increase the temperature of that substance by one Celsius degree.
A substance may undergo a phase change when heat is transferred between the substance and its surroundings, where the flow of heat does not result in a change in temperature.
eml.ou.edu /Physics/module/thermal/pasumarthi/firstlaw.html   (2259 words)

  
 Theory   (Site not responding. Last check: 2007-10-20)
Fourier's Law of Heat Conduction states that the heat flow due to conduction in a given direction is proportional to the temperature gradient normal to the given direction (R.C. Dorf).
The heat flux due to conduction is dependent on the area of the object, the temperature gradient, and the thermal conductivity of that material.
Newton's law of cooling states that the heat flux is in proportion to the heat transfer coefficient to the temperature difference between the material and the fluid.
www.vu.union.edu /~dambruom/senior/4_theory.html   (542 words)

  
 Heat Conduction
The rate at which heat is transferred through a material body is known empirically to be proportional to the temperature difference across the body.
For a rectangular body it is also known to scale in proportion to the cross sectional area of the body perpendicular to the temperature gradient and to scale inversely with the distance over which the temperature difference exists.
The geometry is illustrated in figure 22.3 and the thermal conductivities of common materials are shown in table 22.3.
www.physics.nmt.edu /~raymond/classes/ph13xbook/node229.html   (176 words)

  
 Heat Transfer   (Site not responding. Last check: 2007-10-20)
is the density, C is the heat capacity and k is the thermal conductivity.
The heat capacity, or specific heat, is denoted by C, and describes the amount of heat energy required to produce a unit temperature change in unit mass, that is, the capacity of a material to store thermal energy.
In 2D and 1D, it is often of interest to have heat flux sources in the transversal direction of the modeling, for example, for modeling cooling of thin plates in 2D.
www-math.cudenver.edu /~jmandel/doc/guide/guide62.htm   (783 words)

  
 General Conduction Theory in Heat Transfer
This phenomenon is known as conduction heat transfer, and is described by
This equation determines the heat flux vector q for a given temperature profile T and thermal conductivity k.
The temperature profile within a body depends upon the rate of its internally-generated heat, its capacity to store some of this heat, and its rate of thermal conduction to its boundaries (where the heat is transfered to the surrounding environment).
www.efunda.com /formulae/heat_transfer/conduction/overview_cond.cfm   (232 words)

  
 Heat - Open Encyclopedia   (Site not responding. Last check: 2007-10-20)
Commonly, heat is estrus, a period of increased sexual drive in female mammals.
The amount of heat energy, \Delta Q, required to change the temperature of a material from an initial temperature, T
Definition of symbols used in conduction theory, including disambiguation of different Q notations
open-encyclopedia.com /Heat   (1485 words)

  
 ME315 Thermal Systems Lab
The average heat transfer coefficient between a free convective surrounding and a fin (with known thermal conductivity).
The thermal conductivity of another fin (with the same size and shape) made of a different material.
Consider steady-state 1-D heat conduction in a very long solid rod of uniform cross section subject to a free convective surrounding.
www.calstatela.edu /faculty/cwu/me315/me315ex2.htm   (528 words)

  
 [No title]
Heat Transfer Interpretation The cylinder located inside the cylinder block of the compressor emits heat and transfers to its environment to raise the temperature.
Also, the temperature distribution that was calculated from the heat conduction interpretation was set as one of the load conditions and the bolt contract condition of the cylinder block is set as a separate load condition.
That is, when the temperature distribution calculated from the heat conduction interpretation was used for the load condition of the Static interpretation, it was not necessary to change the data separately and its application procedure is not that complicated.
www.ptc.com /WCMS/files/1982en_file1.doc   (1390 words)

  
 HEAT TRANSFER - brief notes
The rate of heat transfer depends on the temperature driving force, the area available for heat transfer, the nature of the material and the mode of heat transfer (conduction, convection or radiation).
It is the basic transfer mechanism for heat transfer in solids but can also occur through layers of liquids and gases that are not highly mobile.
Conductive transfer occurs across this film which is of unknown thickness.
www.chemeng.ed.ac.uk /people/jack/cheng1h/oldhtnotes/htfrnotes1   (398 words)

  
 News - Story Details
The traditional law of heat conduction introduced by Fourier, coupled with the first law of thermodynamics, leads to the parabolic heat conduction equation normally used to calculate heat transfer.
For these applications, Cattaneo's law of heat conduction is normally used, but it leads to hyperbolic heat conduction equations with a finite speed of propagation, suitable for accurately calculating the rate of heat transfer.
When using a computer program, written by Causley, to provide a visual representation of the heat transfer along a metal rod, they found that as the heat is conducted along the rod it produces waves along the top of a line.
www.gmi.edu /news/storyDetail.asp?storynum=2   (699 words)

  
 Fourier's Law   (Site not responding. Last check: 2007-10-20)
Heat always conducts from warmer objects to cooler objects.
If a copper rod and an iron rod are joined together end to end, and the ends placed in heat sources, the heat will conduct through the copper end more quickly than the iron end because copper has a K value of 92, whereas, iron has a K value of 11.
Which is the integral form of the heat equation.
euler.mcs.utulsa.edu /~class_diaz/cs4533/flowheat/node4.html   (209 words)

  
 THE DIFFUSION EQUATION   (Site not responding. Last check: 2007-10-20)
Darcy's Law is phenomenological because is derived from direct measurements of flow.
There are simple analogous laws for transport of chemical species, heat, and electricity with which you are familiar from previous physical science courses in either high school or college.
The principle behind Fick's Second Law, which is one of the "diffusion equations", is that when flow into a portion of our media doesn't equal flow out then the scalar parameter, concentration, must change with respect to time.
www.geo.utexas.edu /courses/346c/diffusion_equation.htm   (684 words)

  
 Web page of Peter Wapperom
With this dependence the experimentally observed anisotropy of the heat conduction tensor may be described, i.e.\ an increasing thermal conductivity in the direction of orientation and a decreasing thermal conductivity in the direction perpendicular to the orientation.
For the numerical calculations the influence of the mechanical dissipation, the anisotropy of the heat conduction tensor, the cooling due to the thermal expansion and the temperature dependence of the shear modulus will be examined in more detail.
Except the mechanical dissipation, the cooling due to the thermal expansion and the anisotropy of the heat conduction tensor, may be important, particularly for high flow rates (Brinkman numbers).
www.math.vt.edu /people/wapperom/abstracts/thesis.html   (1296 words)

  
 ipedia.com: Law of heat conduction Article   (Site not responding. Last check: 2007-10-20)
Newton 's law of heat conduction says that the heat flow is proportional to the temperature difference Δ T: dq/dt = K Δ T K is the heat resistance of the material over which the temperatur...
K is the heat resistance of the material over which the temperature difference is maintained.
This is the thermal equivalent of Ohm's law for electric flow, although it is much older, but less known.
www.ipedia.com /law_of_heat_conduction.html   (129 words)

  
 [No title]
The rate of flow of energy, or the heat current, is proportional to the difference in end temperatures and inverse of length.
Now in many universities, verification of this law is taken as a project by graduate students and experimental verification is done several thousand times.
Recently we[2] have studied heat conductivity in a known model of magnetic solids (the Heisenberg Spin Chain) with a heat bath which is different from many earlier studies and have found that Fourier's law is obeyed.
www.weizmann.ac.il /home/femohan/RS/popular.html   (762 words)

  
 [No title]   (Site not responding. Last check: 2007-10-20)
Theory: The thermal conductivity of the material can be determined by comparing the measured temperature to that predicted from a mathematical analysis of heat conduction in the solid body.
Fourier’s Law of Heat Conduction states that the heat flux by conduction is proportional to the temperature gradient.
The unknown heat transfer coefficient, h, must first be determined by recording the thermal history of a sample of known shape, thermal conductivity, density and heat capacity.
www.eng.buffalo.edu /Courses/ce328/conductivity.doc   (3864 words)

  
 1 Introduction
The latter permits a heat flux to be generated by an acceleration, or a temperature gradient to be equilibrated by a gravitational field.
He reasoned that under rapid changes of temperature the heat flux is somewhat influenced by the history of the temperature gradient and he was thus able to produce a hyperbolic equation for the temperature - actually a telegraph equation.
The pulse speed problem may not be the most important question in thermodynamics but it is a question that can be answered, and has to be answered, and so there was a series of papers on the problem all using extended thermodynamics of 14 fields.
relativity.livingreviews.org /Articles/lrr-1999-1/node1.html   (1149 words)

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