Heat generation, internal

If an electric current flows through a wire, ihe heat generated internally will result in a temperature distribution between the central axis and the surface of the wire. This type of problem will also arise in chemical or nuclear reactors where heat is generated internally. It is necessary to determine the temperature distribution in such a system and the maximum temperature which will occur. 

Echigo, R., Y. Yoshizawa, K. Hanamura, and T. Tomimura. 1986. Analyticzd and experimental studies on radiative propagation in porous media with internal heat generation. International Heat Transfer Conference 8 827. 

Liquid immersed transformers usually have some form of external radiator to dissipate the heat generated internally by the windings and the core. The radiator is often the surfaces of the tank specially folded into corrugated fins, or is in the form of fins, which are attached to the tank sides. 

Due to the highly exothermic nature of such reactions, some of them can be self-propagating processes (Fig. 5.8). The powder mixture containing metal and carbon is locally preheated only to initiate the reaction and then the external heating is switched off. The temperature rises due to the heat generated internally at the reaction... 

Since cells generate heat, that heat must be dissipated or the ceU temperature will rise. Heat generated internally in a ceU is transferred by conduc-... 

Spontaneous low resistance internal short circuits can develop in silver—zinc and nickel—cadmium batteries. In high capacity cells heat generated by such short circuits can result in electrolyte boiling, cell case melting, and cell fires. Therefore cells that exhibit high resistance internal short circuits should not continue to be used. Excessive overcharge that can lead to dry out and short circuits should be avoided. 

A useful approximation to estimate the possibility of a particular reaction which depends on internal heat generation to produce the products in the proper state for separation is to ignore the heat losses from die reactor, and assumes an average heat capacity calculated from die Neumann-Kopp law... 

Consider a small control volume V = SxSySz (Fig. 4.27), where the inner heat generation is Q "(T) (heat production/volume) and the heat conductivity is A(T). The material is assumed to be homogeneous and isotropic, and the internal heat generation and thermal conductivity are functions of temperature. 

Convection is the heat transfer in the fluid from or to a surface (Fig. 11.28) or within the fluid itself. Convective heat transport from a solid is combined with a conductive heat transfer in the solid itself. We distinguish between free and forced convection. If the fluid flow is generated internally by density differences (buoyancy forces), the heat transfer is termed free convection. Typical examples are the cold down-draft along a cold wall or the thermal plume upward along a warm vertical surface. Forced convection takes place when fluid movement is produced by applied pressure differences due to external means such as a pump. A typical example is the flow in a duct or a pipe. 

The introduction of the internal combustion engine in the late nineteenth century opened up an entirely new approach to combined heat and power. Rather than using the same fluid for the heat and power process as was the case with hot air and steam processes, the tremendous waste heat generated by the internal combustion process can easily be transformed into useful heat. Cogeneration applications using stationary engines were common in Europe prior to World War I and remain quite popular because the heat is relatively... 

Internal gear None Power input and heat generated increases with increasing viscosity For higher viscosities (a) Speed may be reduced (b) Number of gear teeth reduced (c) Lobe-shaped gears employed... 

Internal sources of heat - lights, fan motors, machinery, personnel, etc. - and heat generated by the product... 

Assume a FT boiler of, say, 500 HP, having 2,500 sq ft of heat generating surfaces (and 225 sq ft of internal shell below the waterline, which becomes hot and to which scale can adhere). If we also assume that the boiler has a uniform deposit of scale and corrosion debris on all waterside surfaces to an eggshell thickness (31 mil), then the total mass of dirt equates to ... 

L8. Levy, S., Polomik, E. E., Swan, C. L., and McKinney, A. W., Eccentric rod burnout at 1000 psia with net steam generation, Intern. J. Heat Mass Trans. 5 (July 1962). 

Drums containing moist quinone self-heated, generating smoke and internal pressure. Investigation showed that the moist material showed an exotherm at 40-50°C and decomposed at 60-70°C, possibly owing to presence of impurities. Drums exposed to direct sunlight soon attain a surface temperature of 50-60°C. 

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