Effect of dissolved gases

The subject of Chap. 6 is boiling in micro-channels. Several aspects of boiling are also considered for conventional size channels and comparison with micro-channels was carried out. Significant differences of ONB in micro-channels have been discussed compared to conventional channels. Effect of dissolved gases on boiling in water and surfactant solution was revealed. Attention was paid on pressure drop and heat transfer, critical heat flux and instabilities during flow boiling in microchannels. 

Effect of Dissolved Gases on ONE During Flow Boiling of Water and Surfactant Solutions in Micro-Channels... 

The objective of this chapter is to compile work related to the beginning of sonochemical research and its extension to the aqueous solutions of metal ions. Ultrasound propagation in aqueous salt solutions leads to the hydrolysis, reduction, complexation, decomplexation and crystallization. Such works from different laboratories, along with the effect of dissolved gases on the production of free radicals in water and aqueous solutions upon sonication has been reviewed in this chapter. The generation of turbidity, due to the formation of metal hydroxides and changes in the conductivity of these aqueous solutions, carried out in this laboratory, has also been reported, to give firsthand information of the ultrasound interaction of these solutions. 

The effect of dissolved gases that are not chemically reactive in the ordinary sense on the activity of surfaces and more deeply situated layers has attracted too little attention although it is industrially important. The gases may remain in solid solution or they may be liberated again,... 

Effect of Dissolved Gas. The presence of dissolved gas can lead to a considerable reduction in critical heat flux in pool boiling, as illustrated by the results of Jakob and Fritz [151] shown in Fig. 15.62. The effect of dissolved gases diminishes with decreasing subcooling (increasing fluid temperature), the effect being minimal near saturation conditions. 

FIGURE 15.62 Results of Jakob and Fritz [151] for the effect of dissolved gases on critical heat flux (from Rohsenow [2], with permission of The McGraw-Hill Companies). 

Several models that include the effect of pressure on viscosity are outlined herein. For applications at high pressures, one may also require estimates of the viscosity of liquid hydrocarbons and their mixtures with dissolved gases (such as with CO2, Nj, H2S, etc.) because, due to the high solubility of such gases in hydrocarbon mixtures at elevated pressures, there is a very large reduction in the mixture viscosity. Indeed, such behavior is part of the basis for enhanced oil recovery by miscible gas injection. Even though the effect of dissolved gases is beyond the scope of this chapter, some comments about this are included due to the importance of this subject. 

There are few alternatives for predicting or correlating the viscosities of pure fluids and of mixtures at high pressures, and none of the methods has been extensively tested because of the lack of available data. Only the method of Orbey and Sandler [13] has been partially tested for the effect of dissolved gases on the viscosity of hydrocarbon liquids under pressure [14]. This method has been found to be successful, and therefore is recommended here. 

D. A. Doshi, E. B. Watkins, J. N. Israelachvili, J. Majewski, Reduced water density at hydrophobic surfaces Effect of dissolved gases, Proc. Natl. Acad. Sci. U.S.A. 102 (2005) 9458-9462. 

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