General Study on Heat Transfer

The laws of heat transmission are of controlling importance in the design of equipment and the operation of many diverse instruments in many different industries. This applies particularly to the rubber industry. 

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The wall heat flux qmi cannot be evaluated as in Section II,B. Numerous experimental studies on heat transfer in this two-phase forced-convection region have been carried out, and the results of these investigations are usually presented in the form of a correlation for the wall heat-transfer coefficient hmi, which is defined as in Eq. (32b). Most of these correlations fit one of two generalized forms. The first is... 

Eckert, E.R.G. and Soehnghen. E., "Interferometric Studies on the Stability and Transition to Turbulence of a Free-Convection Boundary Layer , Proc. of the General Discussion on Heat Transfer, pp. 321-323. ASME-1ME. London. 1951. 

At present, there is general agreement among the studies that addressed the effect of saturation conditions on heat transfer, that a higher saturation pressure/temperature yields higher heat transfer coefficients (see for example [14, 15, 18]). 

In general, comprehensive studies have been made on heat transfer of different liquid metals (Hg, Na, NaK, PbBi, Li, etc.). Unless special measures are taken for liquid metal purification, heat transfer coefficients follow the relationship (for tubes) ... 

In the current literature on heat transfer in microchannels in homogeneous systems, large deviations between the different correlations and measurements can be seen. So far, no general conclusion can be drawn and the available heat transfer coefficient correlations are often restricted to the experimental setup and device used in a particular study. Therefore, there is still a need for precise experimental and numerical work in heat transfer analysis in microchannels to gain a better understanding. 

For the region near the attachment point, Mullis found a strong effect of axial position on flux, but no satisfactory general correlation for this effect. In addition, he found no quantitative relation for the heat-transfer characteristics of jets directed toward the propellant surface. Under most conditions studied by Mullis, the radiation contribution is approximately 10% of the convective flux. The effects of solid-particle impingement were not investigated. 

Bastress (B4) investigated the effect of incorporating particles of a solid such as A1203 in the exhaust of a rocket-exhaust igniter. The general conclusion from these studies was that condensible vapors or condensible particles had little effect on the igniter-produced heat transfer, outside of any radiation contributions. 

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