Acceleration cooling

In the reaction zone, superposition of convective cooling and heat consumption through the endothermic reaction leads to an accelerated cooling of the fixed bed. The ratio of the propagation velocity of the reaction front (uw0) and the thermal front can be estimated as follows ... 

Refrigerating the environment is another way of utilizing cold to stabilize wine. Winter cold may be used for this purpose, as well as specialized vat room installations where a chilled atmosphere makes it possible to keep wine at a temperature in the vicinity of 0°C for one or two months. The wine must previously have been filtered. Vats may be equipped with individual exchangers to accelerate cooling. This type of installation is highly effective. Furthermore, it minimizes the risk of oxidation, as the wine does not need to be handled. This system may also be used for fermenting white wines, maintaining a fermentation temperature of around 18-20°C, or even lower. 

Example 4.4 AEth = 0.1 eV, eU = 10 keV Av = 3 x 10 Ano. This means that the Doppler width of the ions in the ion source has been decreased by acceleration cooling by a factor of 300 If the laser crosses the ion beam perpendicularly, the transverse velocity components for ions with n = 3 x 10 m/s at a collimation ratio e = 10 are = n, < 3 x 10 m/s. This would result in a residual Doppler width of An 3 GHz, which illustrates that for fast beams the longitudinal arrangement is superior to the transverse one. 

This reduction of the velocity spread results from the fact that energies rather than velocities are added (Fig. 4.26). If the energy eU Eth, the velocity change is mainly determined by U, but is hardly affected by the fluctuations of the initial thermal velocity. This implies, however, that the acceleration voltage has to be extremely well stabilized to take advantage of this acceleration cooling. 

Although the velocity spread of ions in fast beams is reduced by acceleration cooling, their internal energy (Avib, E t, Ae). which they acquired in the ion source, is generally not decreased unless the ions can undergo radiative transitions to lower levels on their way from the ion source to the laser interaction zone. Therefore, other techniques have been developed to produce cold ions with low internal energies. Three of them are shown in Fig. 4.34. 

Accelerated cooling of controlled-rolled steels to enhance the formation of fine ferrite grains. 

To accelerate cooling speed and shorten the solidification time of the solid-liquid two-phase region. The cooling of melting material will be slowed down, and the macrosegregation also becomes severer in the case of too high column temperature and too fast column speed of the system. 

Higher strength of up to 750 MPa and hardness can be achieved with martensitic chromium steels. Table 1-4. Because of the high carbon content it is possible to transform the austenite to martensite by accelerated cooling. 

Although the velocity spread of ions in fast beams is reduced by acceleration cooling, their internal energy (E ji, E ) which they have acquired... 

The methods used to accelerate cooling are summarised in Table 17.8. There is an approximately even split between natural cooling and using a gas... 

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