Heat of transport

Thuring s radiation group pc,u bulk transport of heat... 

The buoyancy-driven natural convection along the freezing interface in horizontal operation tends to be fairly vigorous. However, it also leads to sprea ding of the zone at the top owing to convection transport of heat upward. 

Generation and transport of heat within the core, including boiloff of water from the reactor vessel. 

Boilers are heat-transfer devices, wherein water, in the form of either liquid water or gaseous steam, is commonly employed as a medium for the transport of heat to some distant point of use. Although other heat-transfer mediums are sometimes utilized, water is particularly suitable because of its relative abundance, low cost, and high heat capacity. It is generally the medium of choice in most boiler applications, whether for domestic, commercial, institutional, or industrial purposes. 

In addition to biogeochemical cycles (discussed in Section 6.5), the hydrosphere is a major component of many physical cycles, with climate among the most prominent. Water affects the solar radiation budget through albedo (primarily clouds and ice/snow), the terrestrial radiation budget as a strong absorber of terrestrial emissions, and global temperature distribution as the primary transporter of heat in the ocean and atmosphere. 

The variable gap method is a steady-state method, with the merit that transport of heat by radiation can be separated from the total heat flow ... 

The governing equation for the transport of heat contains convective and diffusive contributions. Inside the fluid phase, convective transport often dominates. Within... 

The transport of heat a fine example for this factor may be cited thermal decomposition of limestone endothermically to lime. The heterogeneous reaction is chemically shown as ... 

Figure 3.27 Endothermic thermal decomposition of limestone to lime, showing the need for transport of heat.

The general transport models for the turbulent convective transport of heat and mass can be expressed as follows ... 

The transport of heat between latitude bands is assumed to be diffusive and is proportional to the temperature difference divided by the distance between the midpoints of each latitude band. This is the temperature gradient. In this simulation all these distances are equal, so the distance need not appear explicitly. The temperature gradient is multiplied by a transport coefficient here called diffc, the effective diffusion coefficient. The product of the diffusion coefficient and the temperature gradient gives the energy flux between latitude zones. To find the total energy transport, we must multiply by the length of the boundary between the latitude zones. In... 

I also applied the revised computational method to calculate zonally averaged temperature as a function of latitude. I introduced an energy balance climate model, which calculates surface temperature for absorbed solar energy, emitted planetary radiation, and the transport of heat between... 

Even when the number of grid cells in a LB LES simulation of a stirred vessel 1.1 m3 in size amounts to some 36 x 106 grid cells, this implies a cell size, or grid spacing, of 5 mm only. Even a cell size of just a few millimeters makes clear that substantial parts of the transport of heat and species as well as all chemical reactions take place at scales smaller than those resolved by the flow simulation. In other words concentrations of species and temperature still vary and fluctuate within a cell size. The description of chemical reactions and the transport of heat and species therefore ask for subtle approaches to these SGS fluctuations. 

An alternative approach (e.g., Patterson, 1985 Ranade, 2002) is the Eulerian type of simulation that makes use of a CDR equation—see Eq. (13)—for each of the chemical species involved. While resolution of the turbulent flow down to the Kolmogorov length scale already is far beyond computational capabilities, one certainly has to revert to modeling the species transport in liquid systems in which the Batchelor length scale is smaller than the Kolmogorov length scale by at least one order of magnitude see Eq. (14). Hence, both in RANS simulations and in LES, species concentrations and temperature still fluctuate within a computational cell. Consequently, the description of chemical reactions and the transport of heat and species in a chemical reactor ask for subtle approaches as to the SGS fluctuations. 

Let us consider a case of steady evaporation. We will assume a one-dimensional transport of heat in the liquid whose bulk temperature is maintained at the atmospheric temperature, 7 X. This would apply to a deep pool of liquid with no edge or container effects. The process is shown in Figure 6.9. We select a differential control volume between x and x + dx, moving with a surface velocity (—(dxo/df) i). Our coordinate system is selected with respect to the moving, regressing, evaporating liquid surface. Although the control volume moves, the liquid velocity is zero, with respect to a stationary observer, since no circulation is considered in the contained liquid. 

As the fluid s velocity must be zero at the solid surface, the velocity fluctuations must be zero there. In the region very close to the solid boundary, ie the viscous sublayer, the velocity fluctuations are very small and the shear stress is almost entirely the viscous stress. Similarly, transport of heat and mass is due to molecular processes, the turbulent contribution being negligible. In contrast, in the outer part of the turbulent boundary layer turbulent fluctuations are dominant, as they are in the free stream outside the boundary layer. In the buffer or generation zone, turbulent and molecular processes are of comparable importance. 

The latitudinal heat gradient in the atmosphere and ocean remains relatively constant over time despite the short-term and spatial variations in insolation. This steady state is maintained by the net transport of heat from low to high latitudes where it is radiated back into space. Atmospheric currents (winds) are responsible for about half of this meridional net transport of heat. The rest is accomplished by water movement in the... 

Conduction (1) The transport of heat via molecular processes. (2) The transport of electrons causing an electrical current to flow. 

Convection The transport of heat as a result of the physical movement of a carrier, such as air, water, or magma. Convection occurs spontaneously due to density differences. 

The transport of heat to the conversion zone controls the conversion rate in regime n. Regime II exists in the mid range of the volume flux of primary air and is characterised by a conversion zone without extension and an off-gas with relatively high contents of combustibles. Regime II is a consequence of macroscopic conversion front rates being equal to the overall conversion rate. Consequently, the conversion zone has no thickness and no distinct bed process structure. 

Homeostasis. The blood ensures that a balanced distribution of water is maintained between the vascular system, the cells (intracellular space), and the extracellular space. The acid-base balance is regulated by the blood in combination with the lungs, liver, and kidneys (see p. 288). The regulation of body temperature also depends on the controlled transport of heat by the blood. 

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