Direct cooling

Catalytic methanation processes include (/) fixed or fluidized catalyst-bed reactors where temperature rise is controlled by heat exchange or by direct cooling using product gas recycle (2) through wall-cooled reactor where temperature is controlled by heat removal through the walls of catalyst-filled tubes (J) tube-wall reactors where a nickel—aluminum alloy is flame-sprayed and treated to form a Raney-nickel catalyst bonded to the reactor tube heat-exchange surface and (4) slurry or Hquid-phase (oil) methanation. 

There are limits to the precipitation hardening that can be produced by direct cooling if the cooling rate is too liigh we will miss the nose of the C-curve for the precipitation reaction and will not get any precipitates at all But large increases in yield strength are possible if we age harden the alloy. 

Barometric condensers are direct contact coolers and condensers. They may be counter flow or parallel flow. Good contact direct cooling is an efficient inexpensive design, being considerably cheaper and more efficient than indirect surface or tubular coolers. 

Another contributing mechanism is the direct cooling of hot propellant surface by contact with the injected fluid. The fluid should cause the decomposing surface to reduce its pyrolysis rate to a point where combustion cannot be sustained. In addition, the presence of water on the surface would obstruct heat transfer from the gas-phase reaction zones to the solid surface, thus augmenting the cooling of the surface. Proponents of these two approaches have correlated the injection data on the basis of mass of fluid required per unit area of surface, but theoretical justifications for the use of this particular correlating parameter have not been presented. 

The reaction is exothermic, and multitubular reactors are employed with direct cooling of the reactor via a heat transfer medium. A number of heat transfer media have been proposed to carry out the reactor cooling such as hot oil circuits, water, sulfur, mercury, and so on. However, the favored heat transfer medium is usually a molten heat transfer salt, which is a eutectic mixture sodium-potassium nitrate-nitrite. 

Directly cools the vessel metal wall by spray impingement and rundown and, in sufficient quantity, can prevent vessel failure by reducing excessively high metal wall temperatures even in an empty, or nearly empty, vessel. 

Gou Teng is sweet and slightly cold, and enters the Liver and Pericardium meridians. It can directly cool the Liver and extinguish wind. It can effectively relax the tendons because it is a type of vine that particularly enters the meridians and collaterals. 

Qing Dai and Da Qing Ye are very cold herbs. They can directly cool the blood and reduce fever so as to extinguish wind. They can be selected as chief in the formula to treat a severe condition. 

In the case of the nonisothermal first-order exothermic reaction heat is auto catalytic, for it raises the temperature and provokes an increase of reaction rate, yet is itself a product of the reaction. In the Gray-Scott scheme, B is plainly autocatalytic and its degeneration by the second reaction plays the role of the direct cooling in the non-isothermal case. This reaction appears in the chemical engineering literature in 1983,16 and is the keynote reaction in Gray and Scott s 1990 monograph on Chemical Oscillations and Instabilities.17 A justification of the autocatalytic mechanism in terms of successive bimolecular reactions is the subject of Chapter 12. 

The temperature difference between the desired temperature of the conditioned space and the actual underground soil or groundwater temperature (Figure 1.24) can be used for direct cooling in the summer and direct... 

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