Single-hole Orifice Research Articles

Recycled fiber from straw waste: effect of take-up speed and spinneret diameter to linear density and tenacity

Recycled fiber has a great potential as a solution to meet overgrowing synthetic fiber demand and reduce plastic waste in the same time. In the previous research, bottle cap waste is used as the material of the recycled fiber. The result shows that fiber tenacity of recyled fiber from bottle cap waste has low tenacity, different polymer. This phenomena may have been caused by the present of pigment molecule. This research focused on producing recycled fiber from straw waste which has low pigment content. Straw waste was washed and cleaned before the cutting process. Then, the waste was processed in the experiment melt spinning machine with plunger system and single hole orifice in various diameter, 4 mm, 10 mm and 15 mm. The processing temperature was 140° C temperature in three take-up speed, 3.00 m/minutes, 10.30 m/ minutes and 19.16 m/ minutes. The diameter and cross section shape of recycled polyethylene fiber were obtained by using electric microscope with software assistance. The linear density of the recycled fiber was analysed by calculating it with denier and the mechanical strength of the fiber was measured in accordance with the ASTM D 3379-75 standard. High take-up speed leads to higher linear density and take-up speed value is proportionally linear with the tenacity of fiber produced. Moreover, the spinneret diameter is proportionally linear with linear density but it is inversely linear with the tenacity of the fiber produced.

Behavior and pressure drop of an upwardly two-phase flow through multi-hole orifices

Experimental results on hydrodynamic behavior and pressure drop of two-phase mixture flowing upwardly in a pipe containing single- and/or multi-hole orifice plate are presented. It was found from the measurement of the void fraction upstream and downstream the orifices that the flow behavior is significantly affected by the layout of the orifice plate used and the flow starts to recover after approximately 7 D downstream the orifice. Furthermore, increasing orifice holes number results in decreasing the slip ratio. The standard deviation of the void fraction was used to identify the flow pattern before and after the orifices and found that the critical threshold transition occurred at a standard deviation of 0.2. The flow homogenization necessitates a minimum value of the liquid superficial velocity to occur, and the position where it takes place depends on this velocity and on the orifice holes number. It was also inferred from the two-phase pressure drop data across the orifices that three different flow regimes, where the transition between bubbly-to-slug and slug-to-churn flow, can be identified. An assessment of the predicted two-phase flow multiplier using some previous models dedicated to single-hole orifice was achieved; and found that the model proposed by Simpson et al. is the most reliable one. Single-phase pressure drop was also measured and compared with correlations from literature.

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.

Study on the effect of alumina nano-fluid on sharp-edge orifice flow characteristics in both cavitations and non-cavitations turbulent flow regimes

In the present study, the effects of alumina nano-fluid concentration on sharp-edge orifice flow characteristics in both cavitations and non-cavitations turbulent flow regimes are numerically investigated. At different concentration of AL2O3 nonmetallic particles (2%, 4%, 6%, 8%, and 10%) volume fractions in pure liquid water as a base fluid. A single-hole orifice pipe is with a small diameter ratio 0.297 and the orifice plate thickness 14mm. The effects of alumina nano-fluid concentration on sharp-edge orifice flow characteristics have been investigated based on the turbulent kinetic energy, turbulent intensity, turbulent viscosity, and volume fraction of vapor. The results show that for increasing the nonmetallic particle volume fraction from 0.0 to 10%, the turbulent kinetic energy decreases by 20.87% in average downstream the orifice in the whole region, the turbulent intensity decreases by 11.11% in average downstream the orifice in the whole region, the turbulent intensity decreases by 11% in average in the whole region, and the volume fraction of vapor increases by 16.9%. Also, in the separation region downstream the orifice the turbulent kinetic energy increases by 160% in average and the turbulent intensity increases by 74% in average for increasing the nano-fluid concentration from 0.0% to 2%. These are mainly because for using the alumina nano-fluid the separation phenomena decrease due to the increase of the viscosity of the nano-fluid, the total losses in the sharp-edge orifice increase for the increase of the viscosity of the nano-fluid and this causes the increase of the rate of vaporization. In the orifice pipe the total-stress criterion predicts larger cavitating regions in the flow field. However using the nano-fluid with high concentration accelerates the cavitations at the orifice pipe.

Numerical simulations for multi-hole orifice flow meter

The measurement of flow rate is important in many industrial applications including rocket propellant stages. The orifice flow meter has the advantages of compact size and weight. However, the conventional single-hole orifice flow meter suffers from higher pressure drop due to lower discharge coefficient (Cd). This can be overcome by the use of multi-hole orifice flow meter. Flow characteristics of multi-hole orifice flow meters are determined both numerically and experimentally over a wide range of Reynolds numbers. Computational fluid dynamics (CFD) is used to simulate the flow in the single- and multi-hole orifice flow meters. Experiments are carried out to validate the CFD predictions. The discharge coefficients for the different orifice configurations are determined from the CFD simulations. It is observed that the pressure loss in the multi-hole orifice flow meter is significantly lower than that of single-hole orifice flow meter of identical flow area due to the early reattachment of flow in the case of the multi-hole orifice meter. The influence of different geometrical and flow parameters on discharge coefficient is also determined.

Thermal cracking of methane in a liquid metal bubble column reactor: Experiments and kinetic analysis

This study is in the context of hydrogen production by thermal decomposition of methane for the purpose of reducing the CO2 footprint of hydrogen production processes. Experimental studies on methane conversion in a liquid tin bath were carried out and compared with existing kinetic data from other studies in order to identify a suitable reaction rate for the measured conversion. Experiments were conducted using a liquid tin bubble column stainless steel tube reactor with an inner diameter of 35.9 mm and a total length of 1150 mm, comprising a tin filling height of either 1000 mm or 600 mm. Methane gas was injected at flow rates in the range of 5–200 mln/min from the bottom of the reactor maintained at temperatures between 700 °C and 950 °C via a single hole orifice of diameter 1 mm. In general, methane conversion increased with increasing reactor temperatures and decreasing flow rates. The developed thermo-chemical model fitted well with the experimental data obtained during runs with the blank reactor. However, experimental data obtained at 900 °C at very low flow rates (≤25 mln/min – very high residence times and high conversion rates) appear to be much lower than predicted by the model. Further experiments and an improved model are required to understand the process and develop this technology further ahead.

Flow and heat transfer characteristics under synthetic jets impingement driven by piezoelectric actuator

Synthetic jet is a novel flow technique which synthesizes stagnant air to form a jet, and is potentially useful for cooling applications. An experimental measurement utilizing particle image velocimetry (PIV), hot-wire anemometer and infrared camera on the synthetic jet impingement cooling driven by piezoelectric actuator was carried out in the present investigation. The flow and heat transfer characteristics of impinging synthetic jets formed from a single cavity but with different orifices, such as single-slot, single-hole, three-slots and three-holes, were explored. The synthetic jet output from the piezoelectric actuator reaches a peak value when it is excited at its optimum frequency. The synthetic jet output from the piezoelectric actuator reaches a peak value when it is excited at its optimum frequency. For single-hole synthetic jet, the optimum frequency is nearly the same as that of single-slot orifice given the same orifice exit area. But the optimum frequency for the multi-orifices is lower than that of single-orifice synthetic jet. In general, the synthetic jet originated from the single-slot orifice introduces a stronger entrainment and more vigorous penetration in relative to that from the single-hole orifice, performing better than the single-hole synthetic jet orifice. And the multiple synthetic jets exhibit complex influence on the heat transfer by comparison to single synthetic jet for a given actuator cavity and a single actuator. Only when the multi-slots or multi-holes are arranged in their optical mode, the multiple synthetic jets could achieve competitive heat transfer capacity with the single synthetic jet.

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.

On the pressure losses through perforated plates

Perforated plates are widely used in pipeline systems either to reduce flow nonuniformities or to attenuate the onset and the development of cavitation. This experimental work aims at investigating the dependence of the pressure losses through sharp-edged perforated plates with respect to the geometrical and flow key parameters. The data, collected in two large experimental campaigns carried out on different pilot plants, are reported and discussed. Several plates with different geometrical characteristics were tested. More precisely, perforated plates whose equivalent diameter ratio varies between 0.20 and 0.72; relative hole thickness between 0.20 and 1.44; and number of holes between 3 and 52. Experimental data from literature are also considered in order to ensure the reliability of the parametric investigation. The dependence of the pressure loss coefficient upon the Reynolds number, the equivalent diameter ratio, the relative thickness, and the number and disposition of the holes is studied. A comparison to different empirical equations, as available by the technical literature, and to the standard ISO 5167-2 single-hole orifice is also provided.

Whistling of an orifice in a reverberating duct at low Mach number

An experimental investigation of the parameters controlling the whistling frequency and amplitude of an orifice in a confined turbulent flow is undertaken. A circular single hole orifice with sharp edges, a hole diameter equal to 0.015 m and a thickness equal to 0.005 m, is arranged in an air test rig with an inner diameter equal to 0.03 m. The Mach number ranges around 0.02 and the Reynolds number around 10(4). Variable reflecting boundary conditions are arranged upstream and downstream, and several flow velocities are tested. It is found that the Bode-Nyquist criterion accurately predicts the conditions of self-sustained oscillation and the value of the whistling frequency. Furthermore, it is found that the acoustic velocity in whistling regime varies from 1% to 15% of the steady flow velocity, and that it depends on the overall acoustic reflection of the surrounding pipe and on the Strouhal number.

Noise generated by cavitating single-hole and multi-hole orifices in a water pipe

This paper presents an experimental study of the acoustical effects of cavitation caused by a water flow through an orifice. A circular-centered single-hole orifice and a multi-hole orifice are tested. Experiments are performed under industrial conditions: the pressure drop across the orifice varies from 3 to 30 bar, corresponding to cavitation numbers from 0.74 to 0.03. Two regimes of cavitation are discerned. In each regime, the broadband noise spectra obtained far downstream of the orifice are presented. A nondimensional representation is proposed: in the intermediate ‘developed cavitation’ regime, spectra collapse reasonably well; in the more intense ‘super cavitation’ regime, spectra depend strongly on the quantity of air remaining in the water downstream of the orifice, which is revealed by the measure of the speed of sound at the downstream transducers. In the ‘developed cavitation’ regime, whistling associated with periodic vortex shedding is observed. The corresponding Strouhal number agrees reasonably well with literature for single-phase flows. In the 'super cavitation’ regime, the whistling disappears.

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.

Correlation of volumetric mass transfer coefficient with gas holdup in the calming section in a bubble column with a single hole orifice.

We evaluated the value of K L a) C in the calming section using data of K L a) B (bubble bed) which more or less contained the end effects (Kawasaki et al., 1994, Kawasaki and Tanaka, 1995), correlated K L a) C as a function of Φ C again, and then discussed the results obtained

A Photographic Study of Flash-Boiling Atomization

To gain an insight into the mechanisms of flash-boiling atomization, heated water was injected from a single-hole orifice into heated air (steady injections, liquid pressure 697 kPa, air pressure ambient, test temperatures from 300 to 426 K, orifice diameter 0.34 mm, length 1.37 mm). The breakup regime of interest in the study was that where the spray divergence starts at the nozzle exit. Short-duration backlit photographs and laser diffraction dropsize measurements showed that these flashing jets comprise an inner intact core which is surrounded by the diverging fine spray. These details about the spray structure are not visible in conventional photographs of flashing sprays that use scattered light illumination. The present results cast doubt on a previously proposed theory of flash-boiling atomization that attributes the divergence of the spray cone to the expansion processes that occur in an underex-panded compressible flow, since that theory implies that the liquid is already atomized upon leaving th...

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...

各種渦巻噴射弁の微粒化特性比較実験 : 第2報, 単孔渦巻弁

各種渦巻噴射弁の微粒化特性比較実験 : 第2報, 単孔渦巻弁