Convection combined

The room models implemented in the codes can be distinguished further by how detailed the models of the energy exchange processes are. Simple models use a combined convective-radiative heat exchange. More complex models use separate paths for these effects. Mixed forms also exist. The different models can also be distinguished by how the problem is solved. The energy balance for the zone is calculated in each time step of the simulation. 

Btu/(hr) (ft2)(°F/ft) i = inside wall pipe o = outside wall surface of pipe Heat loss from fluid inside pipe through exterior insulation to outside air. Combined convection and radiation ... 

Two major approaches to describing combined convection and diffusion have been used by pharmaceutical scientists. These are the convective diffusion approach and the nonequilibrium thermodynamics approach, described in Sections IV.A.l and IV.A.2, respectively. 

Nonequilibrium thermodynamics provides a second approach to combined convection and diffusion problems. The Kedem-Katchalsky equations, originally developed to describe combined convection and diffusion in membranes, form the basis of this approach [6,7] ... 

Kedem-Katchalsky equations Phenomenological equations for combined convection and diffusion, derived from nonequilibrium thermodynamics. See Eqs. (19) and (20). 

Radauer, H. G., Glatzer, A., and Linzer, w., A Model Combining Convective and Radiative Heat Transfer in CFB Boilers, Circ. Fluid. Bed Tech. V, 9 (1996)... 

Next, consider the gradients of temperature. If the reaction is exothermic, the center of the particle tends to be hotter, and conversely for an endothermic reaction. Two sets of gradients are thus indicated in Figure 8.9. Heat transfer through the particle is primarily by conduction, and between exterior particle surface (Ts) and bulk gas (Tg) by combined convection-conduction across a thermal boundary layer, shown for convenience in Figure 8.9 to coincide with the gas film for mass transfer. (The quantities T0, ATp, A7y, and AT, are used in Section 8.5.5.)... 

Specific correlations of individual film coefficients necessarily are restricted in scope. Among the distinctions that are made are those of geometry, whether inside or outside of tubes for instance, or the shapes of the heat transfer surfaces free or forced convection laminar or turbulent flow liquids, gases, liquid metals, non-Newtonian fluids pure substances or mixtures completely or partially condensable air, water, refrigerants, or other specific substances fluidized or fixed particles combined convection and radiation and others. In spite of such qualifications, it should be... 

Combined convection and radiation coefficients, hc + hr, for horizontal steel or insulated pipes in a room at 80°F... 

A complete treatment of mass transport to interfaces requires combining convective (flow) and diffusion processes 36 38) as the molecules present in a flowing stream are transported by flow (convection) and by diffusion simultaneously. Fortunately, this mass transport problem is well-treated38), particularly in the chemical engineering literature. Robertson 39-40) and Leonard41 are chemical engineers who have been... 

For processes in parallel, the conductance is additive so for combined convective and radiative heat transfer at a surface... 

Such combined convective flows are normally associated with low forced velocities. They can occur, for example, in some electronic cooling situations and in some heat exchangers. 

Consider combined convective flow over a series of geometrically identical bodies as indicated in Fig. 9.2. In such a case, as discussed in Chapter 1, the mean heat transfer coefficient, h, will depend on ... 

There are, thus, nine dimensional variables involved in this type of convection. As a result, there are five dimensionless variables involved in describing combined convective heat transfer. Since the angle, t is dimensionless, these dimensionless variables are ... 

FIGURE 9A Assisting and opposing combined convective flow. 

Therefore, the parameter GrIRe2 will be important in determining whether a boundary layer flow can be treated as a forced convective flow or as a free convective flow or as a combined convective flow. 

Before turning to a discussion of other methods of solving the laminar boundary layer equations for combined convection, a series-type solution aimed at determining the effects of small forced velocities on a free convective flow will be considered. In the analysis given above to determine the effect of weak buoyancy forces on a forced flow, the similarity variables for forced convection were applied to the equations for combined convection. Here, the similarity variables that were previously used in obtaining a solution for free convection will be applied to these equations for combined convection. Therefore, the following similarity variable is introduced ... 

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