Hole Orifice Plate Research Articles

Intensification of advanced oxidation processes (AOPs) for the degradation of bisphenol-A

Abstract Bisphenol-A (BPA), a precursor for many polymers, is a harmful compound for living organisms if present beyond permissible limits in aqueous streams. The combinations of oxidation processes like Hydrodynamic Cavitation (HC), hydrogen peroxide (H2O2), and Fenton’s reagent (H2O2 + FeSO4) were examined for the degradation of BPA in the present study. The effects of operating parameters like inlet pressure, initial concentration of BPA, orifice geometry were investigated on BPA degradation. The degradation rates of BPA increased with inlet pressure up to 0.5 MPa and then showed a decreasing trend beyond 0.5 MPa. The initial concentration of BPA had an inverse relation with the degradation percentage. The multiple hole orifice plate showed better degradation of BPA compared to the single hole orifice plate. In the intensification studies, the addition of hydrogen peroxide to BPA in the cavitation reactor favored BPA degradation. A combination of HC + Fenton’s reagent (0.1 M H2O2 + 0.01 M FeSO4) significantly degraded BPA present in the aqueous streams.

Design and optimization of a cavitating device for Congo red decolorization: Experimental investigation and CFD simulation

The aim of this work is to perform design and optimization of a cavitating device based on CFD simulation. A set of operational and geometrical parameters such as convergence angle, divergence angle, length of throat, and inlet pressure that can affect the hydrodynamic cavitation phenomenon generating in a Venturi are evaluated through CFD simulation and experimental approaches. Response surface methodology (RSM) was employed to achieve the optimum geometrical configuration. The CFD results show that the maximum cavitation zone in the Venturi can be obtained when half angle of the convergence section, throat length and half angle of the divergence section are 22.7°, 4 mm, and 6.5°, respectively. A maximum decolorization of 38.8% has been obtained using the designed Venturi at cavitation number (Cv) of 0.12. Additionally, the results were compared to that of various orifice plates. A decolorization of 26.2% using 33 holes orifice plate and 11.55% in one hole orifice plate approved the superiority of the designed Venturi.

Low pressure hydrodynamic cavitating device for producing highly stable oil in water emulsion: Effect of geometry and cavitation number

In present work, the detailed geometrical analysis of hydrodynamic cavitating devices was carried out to investigate the effect of geometry (orifice and venturi of different shapes) and geometrical parameters on the formation and stability of mustard oil in water nanoemulsion. The optimization of geometrical parameters was carried out based on the lowest droplet size obtained and droplet size reduced per unit pass. It was observed that the single hole orifice plate of circular shape having lower perimeter and higher flow area than other orifice devices, was found to be an efficient device which produced emulsion of lowest droplet size i.e. 87nm at an optimum CV of 0.19 (10bar optimum operating pressure) in 90min of processing time. Moreover, it was found that the kinetic stability of the nanoemulsion assessed under centrifugal and thermal stress conditions remained unaffected by these forces. The prepared nanoemulsion using hydrodynamic cavitation (HC) was found to be physically stable up to 3 months indicating the potential of HC over high energy techniques for producing highly stable emulsion with droplet size below 100nm on a large scale. Furthermore HC was found to be 11 times energy efficient than acoustic cavitation/ultrasonication for the preparation of nanoemulsion.

Cavitation Inception and Head Loss Due to Liquid Flow Through Perforated Plates of Varying Thickness

This paper reports results of an experimental investigation of the loss coefficient and onset of cavitation caused by water flow through perforated plates of varying thickness and flow area to pipe area ratio at high speeds. The overall plate loss coefficient, point of cavitation inception, and point where critical cavitation occurs are functions of perforation hole size, number of holes, and plate thickness. Sixteen total plates were considered in the study with the total perforation hole area to pipe area ratio ranging from 0.11 and 0.6, the plate thickness to perforation hole diameter ranging from 0.25 to 3.3, and the number of perforation holes ranging from 4 to 1800. The plates were mounted in the test section of a closed water flow loop. The results reveal a complex dependency between the plate loss coefficient with total free-area ratio and the plate thickness to perforation hole diameter ratio. In general, the loss coefficient decreases with increasing free-area ratio and increasing thickness-to-hole diameter ratio. A model based on the data is presented that predicts the loss coefficient for multiholed perforated plates with nonrounded holes. Furthermore, the data show that the cavitation number at the points of cavitation inception and critical cavitation increases with increasing free-area ratio. However, with regard to the thickness-to-hole diameter ratio, the cavitation number at inception exhibits a local maximum at a ratio between 0.5 and 1.0. Empirical models to allow prediction of the point of cavitation inception and the point where critical cavitation begins are presented and compared to single hole orifice plate behavior.

Experimental evaluation of low head oxygenators

The overall mass transfer coefficient, G20, for a single hole orifice plate was evaluated in a series of experiments as affected by four geometric variables: orifice plate hole diameter (5, 10, 14, 19, and 22 mm), hydraulic head on the flooded plate (2.5, 5, and 13 cm), water fall height from the orifice to the receiving pool of water (30, 61, 91, and 122 cm), and the collection pool depth (2.5, 8, 13, 25, and 41 cm). This is, in essence, the simplest form of a low head oxygenator (LHO). A regression equation was developed to predict G20 as a function of these variables, their interactions, and squared terms. The hydraulic head above the flooded plate had no significant effect (P<0.10) on the overall mass transfer coefficient. It was determined that the contribution of the orifice hole solely to overall gas transfer was much less than previously assumed, suggesting that a much larger percentage of gas transfer is due to the splashing and subsequent entrainment as water droplets fall into the receiving pool of water. Practical implications of the results are discussed.

HYDRODYNAMIC STUDIES IN FISCHER-TROPSCH DERIVED WAXES IN A BUBBLE COLUMN

Gas hold-up and Sauter mean bubble diameter measurements were made in a 0.051 m diameter by 3 m long glass bubble column in the system, nitrogen-molten wax, with three different waxes (paraffin wax FT-300, Sasol's Arge wax and Mobil's reactor wax). Paraffin wax has a tendency to foam and gas hold-up is a strong function of gas distributor type, temperature and start-up procedure, whereas the reactor waxes do not foam and are much less affected by these variables, In experiments at 265°C with a 1.85 mm single hole orifice plate distributor the gas hold-ups were nearly the same for all three waxes. However, significant differences in Sauter mean bubble diameters were obtained in experiments with different waxes; FT-300 wax produced the smallest Sauter mean bubble diameters whereas Mobil's reactor wax produced the largest bubbles. Addition of 1-octadecanol and octadecanoic acid (up to 10wt%) to the FT-300 paraffin wax caused an increase in gas hold-up and a delay in the foam break-up in runs at 265°C with th...