Cooling direction

Cooling, direct. A cooling system in which the medium to be cooled is not affected by another medium situated between it and the refrigerating apparatus. 

Remote condenser (split) air-cooled direct expansion unit condenser remote, possibly on roof... 

Air-cooled direct expansion unit, mounted adjacent to an outside wall, or through the roof... 

There are two types of snow cooling system. One is direct heat exchanging system and the other is indirect heat exchanging system. Direct heat exchanging system is the same as the forced convection type. Room air is circulated between a room and a stored snow room by fans and cooled directly. The advantages of this system are... 

An example is the (110) plane of III-V semiconductors, such as GaAs(llO). The only nontrivial symmetry operation is a mirror reflection through a line connecting two Ga (or As) nuclei in the COOl] direction, which we labeled as the X axis. The Bravais lattice is orthorhombic primitive (op). In terms of real Fourier components, the possible corrugation functions are... 

The term Qo is a constant. The next two terms describe the corrugation in the COOl] direction. The last term describes the corrugation in the Cl 10] direction, which should be the smallest among all the terms in Eq. (E.IO). 

Figure 2.30 shows the design principle of such a system. Heating and cooling of the shelves are effected indirectly over a heat transfer medium while the condenser evaporator is cooled directly. Contrary to conventional condenser evaporators which... 

A special complication is formed by thermal inhomogeneities. The polymer follows a circular path in the cross-channel direction, which implies that only a certain amount of polymer passes the thermal boundary layer where it is cooled directly. Therefore, for deep cut channels the heat of reaction in the middle of the channel is difficult to remove. Janeschitz Kriegl [18] compared the thickness of the thermal boundary layer with the channel depth, and identified a criterion for thermal homogeneity in a single-screw extruder. This can be adapted to twin-screw extruders with m thread starts per screw. It may be concluded that thermal inhomogeneities become important if ... 

Fig. 18. Selected structure of Pt(II) complexes. For n = Q, at room temperature, top real samples of pure films sandwiched between glass slides bottom emission spectra (excitation at 420 nm). Left fast cooled from the LC phase after the texture is fully developed. Right fast cooled direct from the isotropic phase. Reproduced with the permission of Wiley-VCH 210).

In a mechanical refrigeration system, the air is cooled directly in an exchanger against a boiling freon. Based on the Montreal Protocol, that choice of refrigerant has been limited but is still a practical system especially with the continual development of environmentally friendly refrigerants. 

Fig. 3.70 CM-AFM height images of the cross-section of etched specimens transverse to the extrusion direction of extruded HDPE pipes (a) cooled edge (b) midway between the cooled edge and the middle (c) middle (d) non-cooled edge. In all images, the cooling direction is from the bottom to the top. Scan size 40 x 40 pm2. Gray scale for the feature heights black = 0.0 nm white = 1.20 pm. Reprinted with permission of John Wiley Sons, Inc. from [148], Copyright 1997. John Wiley Sons, Inc.

In Fig. 4.6 a scheme of cooling circuit related to FCS for automotive application is shown. The main components are the pump for liquid circulation, the water reservoir and the heat exchanger with fan. For small size stacks (from 100 to 500 W) it is possible to use only air forced by fan to cool directly the stack, while for higher powers, more suitable for automotive requirements (1-100 kW), it is reasonable to use an internal coolant circuit fed by a liquid, such as de-ionised water or ethylene glycol-water mixtures, to improve the heat removing capacity of an order of magnitude with respect to the gas. 

The presence of solid solutions has some important implications, as will be illustrated for a highly simplified example of two components, depicted in Figure 15.24. Assume that we have a liquid fat of composition a3 at temperature T. Cooling it to T2, crystals will form (provided that nucleation occurs). Now a liquid phase of composition a2 will result and a solid phase (crystals) a5. The molar ratio of solid to liquid will be given by the ratio (a3 — a2)/(a5 — a3). Assume now that the mixture is cooled further to T3. The crystals of composition a5 remain, and the liquid a2 will separate into a liquid and crystals of composition ax and a5, respectively. Note that the composition of the system differs from that resulting from cooling directly to T3. In other words, there is no equilibrium (i.e., within the polymorphic form, probably p ). There is, however, a surface equilibrium the crystals a4 will probably be formed at and around the existing crystals... 

The domain model is partly successful also in the interpretation of calorimetric measurements the Cp versus T curve, which is. -shaped near Tc [9]. It is not capable of accounting for the hysteresis effect when the domains remain uniformly clustered. However, when the sizes of domains in the heating and cooling directions are different, then the hysteresis appears. 

The solution model is capable of describing the hysteresis effect (Fig. 9.12). In the heating direction the x versus T function increases smoothly up to the point rj where x jumps then it increases smoothly again. In the cooling direction x decreases smoothly up to the point T, then drops abruptly and after that escapes continuously. 

Fig. 9.12. High-spin mole fraction versus temperature curves in the solution model with hysteresis h—heating direction c—cooling direction A H/R = 500 K, A S/R = 5, y/R = 300 K.

Normally it is expected that the temperature changes are moderate enough for the spin crossover system to remain in thermodynamic equilibrium. However, rapid cooling may lead to freezing of the HS state so that the transition temperature in the cooling direction apparently decreases. 

Mesogens in the side-chain have not yet lead to clearly identified condis states of the flexible spacers, probably because of the need of longer spacers. Usually the liquid crystalline state changes on cooling directly to the LC glass. 

The white dendrites are a-Ph particles. As evident from Fig. 4.5a for the Ph—3.5 wt% Sh alloy, the a-Ph dendrites are several hundreds of micrometres in size and are oriented along the cooling direction. These particles are surrounded hy eutectic phase (dark grains). The crystallographic structure of the Ph—11.7 wt% Sh alloy (Fig. 4.5h) comprises mostly eutectic particles with only single a-Ph grains formed on cooling. These two phases (a-Ph and eutectic) have different mechanical properties and therefore the mechanical properties of the alloy will depend on its composition. 

Alloys containing both a metal and a metalloid (P, Si, Ge, B) can often be rapidly cooled directly from a melt to form a material with an... 

The goal of this thesis is to present a design for a workable gas-cooled, direct Brayton cycle reactor that could generate 50-100 kWe. The design has not been optimized, but some sensitivity studies were done. The goals were as follow ... 

Streams of solid particles are commonly heated or cooled directly or indirectly. Heat transfer is much more rapid and controllable when using direct heat exchange. 

The background helium gas temperature is set by channeling gas through the trap superstructure which is heated and held at a constant temperature by ceramic heaters or cooled directly by flowing liquid nitrogen. Fluorescence measurements can be performed over a temperature range of 150-550 K with a precision of 1 K. 

Doppler laser-cooling is an essential ingredient in the SCSI-MS technique. First, it provides the necessary damping force to cool directly and sympathetically the atomic and molecular ions, respectively, such that a cold and strongly-coupled two-ion system is formed. Second, it gives rise to the fluorescence photons used in the detection process. Third, the radiation pressure force can be modulated to excite the common motion of the ions. 

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