High Cooling Rates Device

Therefore, Equation 2.62 can be transformed considering the following factors 1) at a high cooling agent flow rate (G °), the temperature can be considered to be " cool = const (as tubular turbulent devices are compact, this requirement is followed in most cases) and 2) the heat transfer coefficient can be substituted by the reaction mixture heat emission coefficient for a fast chemical reaction (in accordance with (Equation 2.63), the heat conductivity coefficient will be determined by the smallest value of the heat emission coefficients). In this case (Equation 2.62) can be transformed using the aforementioned assumptions [97] ... 

This energy deposition rate, 4 GGy s corresponds to a temperature increase of ten million degrees per second for a thermally isolated material of specific heat 0.4 J g K Irradiation of a large piece of material at a dose rate of 1 GGy s" would result in its vaporization in a fraction of a second. Apart from transmission electron microscopes, only nearby nuclear explosions and devices that give short pulses of irradiation for the study of fast radiation processes [96] produce such high dose rates. It is important to realize that continuous irradiation in the electron microscope, even at such dose rates, does not have to cause a large rise in the temperature of the specimen. This is because a very small object like the illuminated area in a TEM has a large surface area per unit volume, and so it is efficiently cooled by thermal conduction into the rest of the specimen. 

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