Heat transfer local

Heat transfer Local velocities, concentration, and pressure Indirect... 

S. Faggiani and W. Grassi, Round Liquid Jet Impingement Heat Transfer Local Nusselt Numbers in the Region with Non-Zero Pressure Gradient, in G. Hestroni (ed.) Proceedings of the 9th International Heat Transfer Conference, 4, pp. 197-202, Hemisphere, New York, 1990. 

The shaded areas in Fig. 6.24, known as pockets, represent areas of additional process-to-process heat transfer. Remember that the profile of the grand composite curve represents residual heating and cooling demands after recovering heat within the shifted temperature intervals in the problem table algorithm. In these pockets in Fig. 6.24, a local surplus of heat in the process is used at temperature differences in excess of AT ,in to satisfy a local deficit. ... 

As the amount of temperature cross increases, however, problems are encountered, as illustrated in Fig. 7i8c. Local reversal of heat flow may be encountered, which is wasteful in heat transfer area. The design may even become infeasible. 

Characterization and influence of electrohydro dynamic secondary flows on convective flows of polar gases is lacking for most simple as well as complex flow geometries. Such investigations should lead to an understanding of flow control, manipulation of separating, and accurate computation of local heat-transfer coefficients in confined, complex geometries. The typical Reynolds number of the bulk flow does not exceed 5000. 

The maximum velocity at the axis is twice the average, whereas the velocity at the wall is zero. The effect of the burner wall is to cool the flame locally and decrease the burning velocity of the mixture. This results in flame stabilization. However, if the heat-transfer processes (conduction, convection, and radiation) involved in cooling the flame are somehow impeded, the rate of heat loss is decreased and the local reduction in burning velocity may no longer take place. This could result in upstream propagation of the flame. 

Figure 5 shows conduction heat transfer as a function of the projected radius of a 6-mm diameter sphere. Assuming an accommodation coefficient of 0.8, h 0) = 3370 W/(m -K) the average coefficient for the entire sphere is 72 W/(m -K). This variation in heat transfer over the spherical surface causes extreme non-uniformities in local vaporization rates and if contact time is too long, wet spherical surface near the contact point dries. The temperature profile penetrates the sphere and it becomes a continuum to which Fourier s law of nonsteady-state conduction appfies. 

Individual Coefficient of Heat Transfer Because of the comphcated structure of a turbulent flowing stream and the impracti-cabifity of measuring thicknesses of the several layers and their temperatures, the local rate of beat transfer between fluid and solid is defined by the equations... 

Limiting Nusselt numbers for laminar flow in annuli have been calculated by Dwyer [Nucl. Set. Eng., 17, 336 (1963)]. In addition, theoretical analyses of laminar-flow heat transfer in concentric and eccentric annuh have been published by Reynolds, Lundberg, and McCuen [Jnt. J. Heat Ma.s.s Tran.sfer, 6, 483, 495 (1963)]. Lee fnt. J. Heat Ma.s.s Tran.sfer, 11,509 (1968)] presented an analysis of turbulent heat transfer in entrance regions of concentric annuh. Fully developed local Nusselt numbers were generally attained within a region of 30 equivalent diameters for 0.1 < Np < 30, lO < < 2 X 10, 1.01 <... 

Heat transfer from immersed bodies is discussed in detail by Eckert and Drake, Jakob, and Knudsen and Katz (see Tutreduction General References ), where equations for local coefficients and the effects of uuheated starting length are presented. Equation (5-44) may also be expressed as... 

Local equilibrium theory Shows wave character—simple waves and shocks Usually indicates best possible performance Better understanding Mass and heat transfer very rapid Dispersion usually neglected If nonisothermal, then adiabatic... 

The initial moisture content is a determinant factor in the rate of heat transfer to the center of the core mat [226,227]. At short press closing times the rapid temperature rise occurs at the same time for both lower and higher moisture content percentages indicating that the steam condensation front reaches the core at the same rate and that this is then determined more by local permeability rather than local moisture content. The slope of the rise is similar as it is the balance of horizontal and vertical permeability which controls the rate of steam flow to the core layer. Furthermore, water remains in the surface layer in a quantity such as... 

Both primary factors and lesser secondary factors affect our sense of satisfac tion with the thermal environment. The primaiy factors have significant reproducible effects and directly affect heat transfer and the occupant s thermal state, Secondar factors that may affect one s sense of satisfaction with a space are conditions such as color and ambiance, local climate, age, physical fitness, sound, food, and illness. These secondary factors have smaller to negligible effects on one s thermal state and will not be discussed here, but such information is available. ... 

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