Gas flow turbulent

In modem Hquid-fuel combustion equipment the fuel is usually injected into a high velocity turbulent gas flow. Consequently, the complex turbulent flow and spray stmcture make the analysis of heterogeneous flows difficult and a detailed analysis requires the use of numerical methods (9). 

Riber, E., et al.. Towards large eddy simulation of non-homogeneous particle laden turbulent gas flows using Euler-Euler approach, in Eleventh Workshop on Two-Phase Flow Predictions. 2005, Merseburg, Germany. 

Very little work has been reported on vaporization under conditions of turbulent gas flow. Ingebo (61), for example, took pains to minimize approach stream turbulence. Two exceptions are the investigations of Maisel and Sherwood (83) and Fledderman and Hanson (27). Neither went so far in analysis as insertion into the Nusselt number equations of allowance for the additional relative velocity between droplet and air stream occasioned by turbulence. In the case of Maisel and Sherwood s investigation with model droplets at fixed positions, the effect would not be expected to be extreme, because at all times there was appreciable relative velocity, discounting turbulence. However, in Fledderman and Hanson s experiments the relative velocity, discounting turbulence, fell away as the droplets accelerated up to stream velocity. Thus turbulence would eventually provide the only appreciable relative velocity. The results indicate a substantial increase in vaporization rate because of the turbulence and provide some basis for gross engineering estimates. 

A short cocurrent horizontal pipeline contactor gives 86 percent removal of NH3. There is no bypassing because of the highly turbulent gas flow and injection of liquid into the center of the pipe. What would we expect the exit gas temperature to be ... 

In computation using the stochastic trajectory model, the Monte Carlo approach is commonly employed. It is necessary to calculate several thousands, or even tens of thousands, of trajectories to simulate the particle flow field. The central issue in developing the stochastic trajectory model is how to model the instantaneous turbulent gas flow field. The method... 

Time- and space-resolved major component concentrations and temperature in a turbulent gas flow can be obtained by observation of Raman scattering from the gas. (1, 2) However, a continuous record of the fluctuations of these quantities is available only in those most favorable cases wherein high Raman scattering rate and/or slow rate of time variation of the gas allow many scattered photons (> 100) to be detected during a time resolution period which is sufficiently short to resolve the turbulent fluctuations. (2, 3 ) Fortunately, in other cases, time-resolved information still can be obtained in the forms of spectral densities, autocorrelation functions and probability density functions. (4 5j... 

Three main processes appear to control the modification and loss (or transport) of analyte aerosol in the spray chamber droplet-droplet collisions resulting in coagulation, evaporation, and impact of larger droplets into the walls of the spray chamber. Aerosol droplets can be lost (impact the walls and flow down the drain) as a result of several processes in the spray chamber [11,20]. Because turbulent gas flows are key to generating aerosols with pneumatic nebulizers, the gas in the spray chamber is also turbulent. Droplets with a variety of diameters... 

Browne, E.W. B., 1974, Deposition of particles on rough surfaces during turbulent gas flow in a pipe. Atmos. Environment 8, 8, 801. 

Heat delivery. Convection and conduction from hot gas sweeping by is the leading mode of heat transfer to a drying coating to supply the latent heat of vaporization of solvent. Except when solvent evaporation is so very rapid as to produce an appreciable convective velocity away from the surface, in turbulent gas flow the mechanisms of heat transfer to and solvent transfer away from the evaporating surface are virtually identical combinations of convective action with thermal conduction on the one hand and molecular diffusion on the other. This is reflected in useful correlations, like Colburn s, of the mass transfer coefficient with the more easily measured heat transfer coefficient in turbulent flow. It is also the reason that the now fairly extensive literature on the performance and design of driers focuses on heat transfer coefficients and heat delivery rates. 

In the considered case, the basic mechanisms of formation of droplets in the turbulent gas flow are processes of coagulation and breakage of drops. These two processes proceed simultaneously. As a result, the size distribution of the drops is established. Assuming homogeneity and isotropy of the turbulent flow, this distribution looks like a logarithmic normal distribution [1] ... 

Breakage of drops in a turbulent gas flow occurs due to the inertial effect caused by a significant difference of density of liquid and gas, and also due to difference of pulsation velocities, i.e. velocities of turbulent pulsations flowing around a drop, at opposite ends of the drop. Breakage of a drop thus occurs due... 

Consider the mass-exchange of a drop with radius R suspended in a turbulent gas flow. At the initial moment in time, the composition of the drop is specifled in the form of a mass concentration pjoL (kg m ) and a gas concentration PiOG, where i= 1,2..., s, and s is the number of components. Two simplifying assumptions are made ... 

Of special interest is the process of drop breakup in a turbulent gas flow. An expression for the dynamic thrust acting on the drop surface in an isotropic turbulent flow of gas is obtained in [2] ... 

Coagulation of drops in a turbulent gas flow was considered in Section 15.2. The change of the average drop volume with time is described by... 

Consider first the behavior of an isolated drop in quiescent gas, and then the process of mass-exchange in an ensemble of drops in the quiescent gas and in the turbulent gas flow in the pipe. Then the behavior of spectrum of drops injected into a gas flow through atomizers will be analyzed. 

Consider as an example the mass exchange for water-methanol solution drops that were input into a turbulent gas flow in a pipe at the following parameter values pipe diameter d = 0.4 m pressure P = S MPa gas temperature Tg = 313 °K inhibitor flow rate q = 1 kg/thousand nm initial mass concentration of methanol in the solution xmo = 95%. Fig. 21.6 shows the dependence of the characteristic relaxation time of the system, t q, on the flow rate Q of the gas under normal conditions. The decrease of t q with the growth Q is explained by the reduction of the average drop size. All other factors being equal, the time teq grows with the increase of the pipe diameter and the pressure. Knowing Tgq, it is... 

Separation processes of gas-liquid (gas-condensate) mixtures are considered in Section VI. The following processes are described formation of a liquid phase in a gas flow within a pipe coalescence of drops in a turbulent gas flow, condensation of liquid in throttles, heat-exchangers, and turboexpanders the phenomena related to surface tension efficiency of division of the gas-liquid mixtures in gas separators separation efficiency of gasseparators equipped with spray-catcher nozzles of various designs - louver, centrifugal, string, and mesh nozzles absorbtive extraction of moisture and heavy hydrocarbons from gas prevention of hydrate formation in natural gas. 

The purpose of this chapter is to show the role of the model used for the interfacial shear at different stages of stability analyses of the stratified flow configuration and to summarize progress made in formulating a closure law which reflects the dynamics of the interaction involved in turbulent gas flow over a mobile wavy interface. 

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