Conduction heat source

A solution for the unknown temperatures could be obtained If all element conductances, heat sources and sinks were known. 

The third characteristic of interest grows directly from the first, ie, the high thermal conductance of the heat pipe can make possible the physical separation of the heat source and the heat consumer (heat sink). Heat pipes >100 m in length have been constmcted and shown to behave predictably (3). Separation of source and sink is especially important in those appHcations in which chemical incompatibilities exist. For example, it may be necessary to inject heat into a reaction vessel. The lowest cost source of heat may be combustion of hydrocarbon fuels. However, contact with an open flame or with the combustion products might jeopardize the desired reaction process. In such a case it might be feasible to carry heat from the flame through the wall of the reaction vessel by use of a heat pipe. 

There is assumed to be no interaction between the superfluid and normal components, thus the superfluid component can diffuse very rapidly to a heat source where it absorbs energy by reverting to the normal state. It thereby produces the very high effective thermal conductivity observed in helium II. 

Figure 8. Effect on conductivity, heat of fusion (degree of crystallinity), and Tg of adding zeolite to PEO-UBF4. Adapted from B. kumar, L. G. Scanlon, J. Power Sources 1994, 52, 261.

In all cooled appliances, the heat from the device s heat sources must first arrive via thermal conduction at the surfaces exposed to the cooling fluid before it can be transferred to the coolant. For example, as shown in Fig. 2.2, it must be conducted from the chip through the lid to the heat sink before it can be discharged to the ambient air. As can be seen, thermal interface materials (TIMs) may be used to facilitate this process. In many cases a heat spreader in the form of a flat plate with high thermal conductivity may be placed between the chip and the lid. 

Fig. 2.3 Effect of thickness on heat spreading for different heat source areas, material thermal conductivities, and heat transfer coefficients (A in cm, in W/mK, hinW/m K). Reprinted from Lasance and Simons (2005) with permission...

A typical method for thermal analysis is to solve the energy equation in hydrodynamic films and the heat conduction equation in solids, simultaneously, along with the other governing equations. To apply this method to mixed lubrication, however, one has to deal with several problems. In addition to the great computational work required, the discontinuity of the hydrodynamic films due to asperity contacts presents a major difficulty to the application. As an alternative, the method of moving point heat source integration has been introduced to conduct thermal analysis in mixed lubrication. 

Q is the heat generated per unit area and time 4 is the contact length of the heat source p is the density c is the specific heat K is its heat conductivity... 

An one-point heat source. Of special interest is the nonstationary heat conduction problem in the situation when a heat source is located only at a single point x = under the agreement that at this point the solution of problem (l)-(3) satisfies the condition of conjugation... 

For the heat conduction equation with a heat source depending on the temperature in accordance with the law... 

Here Go(a ,t) is a function of the heat source of the Cauchy problem associated with the one-dimensional heat conduction equation... 

Thermal conduction is assumed to take place from the small spherical heat source with a radius, r. This approximation leads to the one-dimensional heat conduction... 

Here, q is the flux of heat (W m ), X is the thermal conductivity (W K ), T is temperature (K), and r is the distance from the center of the spherical heat source. Under the steady state approximation, the heat generated in the small sphere, Qj , is equal to the heat flow, Qflow. from the surface of the small sphere to the surrounding medium, as expressed by Eq. (8.7). 

The simulation example DRY is based directly on the above treatment, whereas ENZDYN models the case of unsteady-state diffusion, when combined with chemical reaction. Unsteady-state heat conduction can be treated in an exactly analogous manner, though for cases of complex geometry, with multiple heat sources and sinks, the reader is referred to specialist texts, such as Carslaw and Jaeger (1959). 

Nickel is a malleable, ductile, tenacious, slightly magnetic, silvery white metal, which conducts heat and electricity fairly well. It is ferromagnetic at ordinary temperatures but becomes paramagnetic at elevated temperatures. Nickel is closely related in chemical properties to iron and cobalt. While sulphidic sources of nickel account for the world s major nickel supplies, it may be pointed out that lateritic nickel deposits (which essentially constitute an oxidic source of the metal) are more extensive than the sulphidic sources. 

The fluid physical properties required for heat-exchanger design are density, viscosity, thermal conductivity and temperature-enthalpy correlations (specific and latent heats). Sources of physical property data are given in Chapter 8. The thermal conductivities of commonly used tube materials are given in Table 12.6. 

Keywords Geothermal response test, ground thermal conductivity, line source, GENOPT, TRNSYS, borehole heat exchanger... 

In this equation S includes heat of chemical reaction, any interphase exchange of heat, and any other user-defined volumetric heat sources. At is defined as the thermal conductivity due to turbulent transport, and is obtained from the turbulent Prandtl number... 

In normal atmospheric conditions, fire usually is initialed by a combustible material coming in contact with a heat source. The spread of fire occurs due to direct flame impingement or the transfer of heat to the surrounding combustible materials. Heat transfer occurs by three principal mechanisms - conduction, convection, and radiation. Conduction is the movement of heat through a stationary medium, such as solids, liquids or gases. Steel is a good conductor of heat as is aluminum, therefore they can pass the heat of a fire if left unprotected. 

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