Stagnation-point flow reactor

Fig. 2 Reported growth rate of tin oxide, prepared from (Ctf3)4Sn + O2, as a function of temperature. Borman et al. [39] used a hot wall reactor with various diameters shown in the legend, [TMT] = 99-390 ppm. Ghostagore [32,33] used a horizontal cold wall reactor with [TMT] = 117-310 ppm. Chow et al. [54] used a stagnation-point flow reactor, and Vetrone et al. [55] a horizontal hot-wall reactor with a tilted substrate...

Vertical reactor or stagnation point flow reactor at atmospheric and reduced pressure conditions... 

Bar JN, Karakaya C, Deutschmann O Catalytic ignition of light hydrocarbons over Rh/ AI2O3 studied in a stagnation-point flow reactor, Proc Combust Inst 34 2313-2320, 2013. 

Vertical CVD Reactors. Models of vertical reactors fall into two broad groups. In the first group, the flow field is assumed to be described by the one-dimensional similarity solution to one of the classical axisymmetric flows rotating-disk flow, impinging-jet flow, or stagnation point flow (222). A detailed chemical mechanism is included in the model. In the second category, the finite dimension of the susceptor and the presence of the reactor walls are included in a detailed treatment of axisymmetric flow phenomena, including inertia- and buoyancy-driven recirculations, whereas the chemical mechanism is simplified to a few surface and gas-phase reactions. 

A.ll experiments were conducted at atmospheric pressure in a quartz-glass flow tube reactor (2.-5 cm diameter. 20 cm length). The reaction gases were premixed and flowed perpendicular to the catalytic foil in a stagnation point flow configuration (inset fig. 1).. All experiments were conducted at total gas flow rates between 1 slpm and 6 slpm. which did not influence the results within experimental error. The high-purity platinum foils were resistively heated and the foil temperature was determined by a chromel/alumel thermocouple spotwelded to the back of the foil. Temperature measurements were reproducible within 10 K on the same foil and within 30 K in independent runs with different foils. 

Figure 6 shows a hot-filament CVD reactor together with a sketch of a stagnation-point flow the simulation is based on. A mixture of H2 and CH4 passes a hot fllament placed at a distance L = 1 cm away from the substrate. The pressure is 33.3 mbar, the temperature of the filament 2430 K, the temperature of the substrate is varied between 800 and 1240 K, and the gas composition is 0.4 mole% CH4 in H2. The corresponding Navier-Stokes equations [10,16] of... 

As mentioned in Section 2.1, the development of surface reaction mechanisms proceeds with optimization of theoretical reaction parameters through comparisons with measurements obtained in a variety of reactors. Catalytic ignition of hydrogen over noble metals has been extensively investigated in stagnation point flow geometries. 

It is probably clear that any number of performance indexes can be written by comparing the various mass fluxes. The important point is that for the stagnation-flow geometries, all the mass fluxes can be written per unit surface area. Thus the indexes, which are ratios of fluxes, are independent of reactor size, so long as the reactor preserves the desirable similarity behavior. It is also important to note that these effectiveness indexes can be derived from the one-dimensional similarity simulations that consider the detailed chemical reaction behavior. 

The drift is formed due to the stagnation regions before the reactant introduction point in this case, the process takes place in the whole reactor volume due to the strong reverse diffusion of the reactant flows (Figure 4.1c). 

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