Effects of Liquid Viscosity on Bubble Growth From Submerged Orifice Plates

2017 ◽  
Author(s):  
Sanjivan Manoharan ◽  
Milind A. Jog ◽  
Raj M. Manglik
Keyword(s):  
Bubble Growth ◽  
High Speed ◽  
Bubble Dynamics ◽  
Pure Water ◽  
Air Flow ◽  
Low Flow ◽  
Glycerol Solution ◽  
Stainless Steel Capillary ◽  
Flow Rates ◽  
Water Glycerol

Experimental investigation of bubble growth from orifice plates submerged in pools of viscous liquids has been carried out using high speed videography. Conflicting effects of viscosity on ebullience have been reported in the literature. These are addressed in the present study and their range of applicability has been identified. Furthermore, the effects of chamber volume on bubble dynamics in viscous media are examined. Orifice plates made of Acrylic glass (a hydrophilic surface) with varying orifice diameters from 0.813 mm to 1.500 mm, have been utilized. Additionally, bubble dynamics from a stainless steel capillary nozzle was captured and compared with that from orifice plates. The six different liquid pools were used, viz., pure distilled water, ethylene glycol, propylene glycol, and three different aqueous glycerol solutions. The aqueous glycerol solutions varied in viscosity from 48 cP to 128 cP. The flow rate was regulated such that the isolated bubble regime was encountered. For the smaller orifices, viscosity effects were present at all flow rates and the bubbles in water-glycerol solutions were much larger than those in pure water. However, for the larger orifice sizes, water-glycerol solutions produced bubbles that were larger than those in water only at high air flow rates. For larger orifice sizes, at low flow rates, there was no increase in bubble size in highly viscous water-glycerol solutions compared to pure water. In fact, with 1.5 mm diameter plate orifice, the bubbles for 128 cP water-glycerol solution were smaller than those in pure water at low air flow rates. When chamber effects were present, the bubbles in the more viscous medium differed in shape and size from those in pure water.

A Photographic Study on the Effects of Hydrophobic-Spot Size and Subcooling on Local Film Boiling

2013 ◽  
Author(s):  
Bambang Joko Suroto ◽  
Masahiro Tashiro ◽  
Sana Hirabayashi ◽  
Sumitomo Hidaka ◽  
Masamichi Kohno ◽  
...  
Keyword(s):  
Heat Flux ◽  
High Speed ◽  
Bubble Dynamics ◽  
Pure Water ◽  
Nucleate Boiling ◽  
Spot Size ◽  
Copper Surface ◽  
Film Boiling ◽  
Working Fluid ◽  
Boiling Regime

The effects of hydrophobic circle spot size and subcooling on local film boiling phenomenon from the copper surface with single PTFE (Polytetrafluoroethylene) hydrophobic circle spot at low heat flux has been investigated. The experiments were performed using pure water as the working fluid and subcooling ranging from 0 and 10K. The heat transfer surfaces are used polished copper block with single PTFE hydrophobic circle spot of diameters 2, 4 and 6 mm, respectively. A high-speed camera was used to capture bubble dynamics and disclosed the sequence of the process leading to local film boiling. The result shows that local films boiling occurs on the PTFE circle spot at low heat flux and was triggered by the merging of neighboring bubbles. The study also showed that transition time required for change from nucleate boiling regime to local film boiling regime depends on the diameter of the hydrophobic circle spot and the subcooling. A stable local film boiling occurs at the smallest diameter of hydrophobic spot. Subcooling cause the local film boiling occur at negative superheat and oscillation of bubble dome.

Characteristics of Nucleation and Bubble Growth During Microscale Boiling

2005 ◽  
Author(s):  
Yong Tian ◽  
Jiang-Tao Liu ◽  
Xiao-Feng Peng
Keyword(s):  
Bubble Growth ◽  
High Speed ◽  
Bubble Dynamics ◽  
Ccd Camera ◽  
Initial Position ◽  
Length Scale ◽  
Formation Theory ◽  
Nucleus Formation ◽  
Microlayer Evaporation ◽  
Parallel Microchannels

In this paper, both nucleus formation and bubble growth during boiling in microchannels were investigated. A series of visualized experiments were conducted to observe the boiling nucleation and bubble dynamics restricted within parallel microchannels on a silicon wafer. The channels were rectangular and had selected length scale ranging from 50 to 100 microns. A high-speed CCD camera was employed together with a microscope to dynamically record the boiling images. The rates of bubble growth were measured in the channels. The phase change nucleus formation theory was used to determine the initial position of the bubble. The bubble growth rate was described by two ordinary differential equations deduced from the microlayer evaporation theory. The calculation and experimental results were reasonably coincided.

Suppression of Cavitation in Inducers by J-Grooves

2006 ◽  
Vol 129 (1) ◽  
pp. 15-22 ◽  
Author(s):  
Young-Do Choi ◽  
Junichi Kurokawa ◽  
Hiroshi Imamura
Keyword(s):  
High Speed ◽  
Leading Edge ◽  
Design Flow ◽  
Low Flow ◽  
Axial Pressure ◽  
Flow Rates ◽  
New Device ◽  
Axial Pressure Gradient ◽  
Blade Tip ◽  
Suction Performance

Cavitation is a serious problem in the development of high-speed turbopumps, and an inducer is often used to avoid cavitation in the main impeller. Thus, the inducer often operates under the worst conditions of cavitation. If it could be possible to control and suppress cavitation in the inducer by some new device, it would also be possible to suppress cavitation occurring in all types of pumps. The purpose of our present study is to develop a new, effective method of controlling and suppressing cavitation in an inducer using shallow grooves, called “J-Grooves.” J-Grooves are installed on the casing wall near the blade tip to use the high axial pressure gradient that exists between the region just downstream of the inducer leading edge and the region immediately upstream of the inducer. The results show that the proper combination of backward-swept inducer with J-Grooves improves the suction performance of the turbopump remarkably, at both partial flow rates and the design flow rate. The rotating backflow cavitation occurring at low flow rates and the cavitation surge which occurs near the best efficiency point can be almost fully suppressed by installing J-Grooves.

Boiling Under Hele-Shaw Flow Conditions: The Occurrence of Viscous Fingering

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Felix Reinker ◽  
Marek Kapitz ◽  
Stefan aus der Wiesche
Keyword(s):  
High Speed ◽  
Bubble Dynamics ◽  
Pure Water ◽  
Phase Interface ◽  
Viscous Fingering ◽  
Working Fluid ◽  
Small Scale ◽  
Vapor Bubbles ◽  
Cell Parameters ◽  
Fingering Phenomena

Boiling and bubble dynamics were experimentally investigated in a Hele-Shaw flow cell using pure water at atmospheric pressure as the working fluid. The resulting vapor bubble shapes were recorded by means of a high-speed camera for several plate spacings and heating power levels. It was found that viscous fingering phenomena of vapor bubbles occurred only under very special boiling conditions and cell parameters. The evaporation front velocity was identified as a major parameter for the onset of viscous fingering. The observed basic viscous fingering dynamics was in reasonable agreement with theoretical analyses. In addition to that classical viscous large fingering, small-scale evaporation instability was observed leading to microscopic roughening of accelerating evaporation fronts. This instability might be explicitly related to evaporative heat and mass transfer effects across the fast-moving phase interface.

High-Speed Micro-Thermal Focusing Field-Flow Fractionation of Micron-Size Particles

2004 ◽  
Vol 69 (2) ◽  
pp. 322-329 ◽  
Author(s):  
Irina A. Ananieva ◽  
Anastasia Yu. Menshikova ◽  
Tatiana G. Evseeva ◽  
Josef Janča
Keyword(s):  
High Speed ◽  
Thermal Field ◽  
Low Flow ◽  
Field Flow Fractionation ◽  
High Field Strength ◽  
Flow Rates ◽  
Focusing Effect ◽  
Carrier Liquid ◽  
Micron Size ◽  
Flow Fractionation

Micron-size polystyrene-based latex particles were separated by using new micro-thermal field-flow fractionation (micro-TFFF). The order of retention from the largest to the smallest particles that appears at high field strength and high flow rate corresponds to the focusing mechanism which itself is a consequence of the lift forces acting on the particles. The mechanism of steric exclusion can only be effective at low flow rates of the carrier liquid. Whenever high-speed separation was performed, the focusing effect clearly dominated the FFF mechanism. This application of micro-TFFF in focusing mode to the separation of the particles is the first one published. As a result, micro-TFFF thus became a very universal technique for the separation of synthetic and natural macromolecules and of particles of various origin and size up to large (micron-size) diameter.

Experimental Study of Gas-Liquid Flow Through a Multi-Stage, Mixed-Flow Electric Submersible Pump

2018 ◽  
Author(s):  
Marine Dupoiron
Keyword(s):  
High Speed ◽  
Imaging Techniques ◽  
Flow Patterns ◽  
Low Flow ◽  
Submersible Pump ◽  
Mixed Flow ◽  
Flow Rates ◽  
Flow Through ◽  
Inlet Conditions ◽  
Electric Submersible Pump

Laser Doppler velocimetry (LDV) and high-speed imaging techniques were used in a transparent model of a fourstage, mixed-flow commercial electric submersible pump (ESP) to characterize the flow through a range of inlet gas volume fractions (GVF) from 0 to 30%. Measurements demonstrate the presence high turbulence levels in the wake of the impeller blades, and recirculation cells at low flow rates. In gas-liquid conditions, the bubble size varied within a pump stage, as break-up occurred at the impeller tip, and coalescence was dominant in the diffuser, especially at low flow rates because of recirculation. At moderate-to-high inlet GVF, the first impeller acted as a mixer and the flow patterns at the stage level alternated between bubbly and radially separated flows, as short gas slugs propagated through the stages. The flow patterns at the stage level did not depend on the pump inclination, but the inlet conditions did, with worse performance induced by slugging flows for the horizontal setup.

Computational and Experimental Characterization of Single Bubble Dynamics in Isothermal Liquid Pools

2007 ◽  
Author(s):  
A. Subramani ◽  
S. K. Kasimsetty ◽  
R. M. Manglik ◽  
M. A. Jog
Keyword(s):  
Surface Tension ◽  
Bubble Growth ◽  
High Speed ◽  
Bubble Dynamics ◽  
Great Influence ◽  
Growth Dynamics ◽  
Equivalent Diameter ◽  
Parametric Effects ◽  
Liquid Pools ◽  
Visualization Techniques

The process of bubble growth is of great influence on the bubble volume and bubble rise velocity. The overall behavior of bubbles at fluid interfaces depends strongly on bubble growth and the closely linked process of bubble detachment. In the present study, the dynamics of a single gas bubble emanating from an orifice submerged in isothermal liquid pools is investigated computationally and experimentally. The parametric effects of liquid properties, capillary diameters and air flow rates on the bubble shape, equivalent diameter, and growth times on the dynamic behavior (incipience, growth and necking) of air bubbles, in fluids of varying surface tension and viscosity, as it grows from a tip of a sub-millimeter-scale capillary orifice have been studied. Computational solutions have been obtained by solving the complete set of governing equations using Volume of Fluid (VOF) interface tracking method. The CFD model has been verified experimentally using optical high speed micro-scale flow visualization techniques. The results were analyzed in a theoretical stand point considering the various forces acting on the bubble such as forces due to buoyancy, viscosity, surface tension, liquid inertia, and gas momentum transport, and the consequent motion of the gas-liquid interface. The results obtained ascertain the role of liquid-gas interfacial forces as well as the fluid properties on the bubble growth dynamics.

A CFD Study on Cavitating Flow in High-Speed Centrifugal Pumps under Low Flow Rates

2014 ◽  
Vol 945-949 ◽  
pp. 914-923 ◽  
Author(s):  
Jian Ping Yuan ◽  
Yu Wen Zhu ◽  
Ai Xiang Ge
Keyword(s):  
Total Pressure ◽  
High Speed ◽  
Volume Fraction ◽  
Experimental Methods ◽  
Cavitation Number ◽  
Low Flow ◽  
Centrifugal Pumps ◽  
Flow Rates ◽  
Blade Passage ◽  
Critical Cavitation

Cavitation is one of the most important aspects that need to be considered while designing centrifugal pumps, since it is a major contributor to failure and inefficiency. In order to study the cavitating performance in high-speed centrifugal pumps under low flow rates, the pump named IN-32-32-100 with two different impellers was investigated based on numerical and experimental methods. The impeller case 1 is the impeller with six blades. The impeller case 2 is the impeller with four long and four splitter blades. The research results show that the cavities of two impellers occur at the impeller inlet. The region of developed cavities extends and the volume fraction in the blade passages gradually increases with the decrease of inlet total pressure at the flow rate of 0.5Qd. The cavities distribute asymmetrically in each blade passage and the vapor fraction of one blade passage is significantly larger compared with them of blade passages. The inner flow of the pump can be effectively improved with more uniform pressure distribution by applying splitter blades. The critical cavitation number of the impeller case 1 and impeller case 2 corresponding to the sudden head-drop point are 3.2m and 3.55m, respectively. Compared with impeller case 2, cavitating performance of the pump with impeller case 1 is better. The numerical results agree well with the experimental data, which shows that the numerical method in the present study can to some extent accurately predict the cavitating development inside the high-speed centrifugal pump.

Effects of Sand Ingestion Through an Axial Fan With Blade Staggering

2008 ◽  
Author(s):  
Adel Ghenaiet
Keyword(s):  
High Speed ◽  
Air Flow ◽  
Operating Conditions ◽  
Sand Particle ◽  
Computational Domain ◽  
Axial Fan ◽  
Complex Flow ◽  
Particle Trajectories ◽  
Flow Rates ◽  
The Impact

This paper presents the numerical results of sand particle trajectories and erosion patterns in a single stage axial fan used in industrial air ventilation, and the subsequent deterioration of the blade geometry. Attention is focused in particular on the effects of rotor blade staggering and the operating flow rates. By adopting the Lagrangian formulation to study the dynamics of particulate air-flow, the flow-field within the blade passage is solved separately. Particle trajectories computation is based on a stochastic tracking algorithm, which includes eddy-lifetime concept for turbulence, and accounts for the complex flow patterns near walls, random particle rebound factors, in addition to particle size, shape and fragmentation. The equations of motion are solved in a stepwise manner, whereas, particle tracking in different cells of the computational domain is based on the finite element method. The computation of the particle trajectories yields the impact locations along the blade surfaces, where the corresponding erosion patterns are calculated by using experimental correlations. The results of the numerical simulations carried out at low and high concentrations of MIL-E5007E sand particles, for different fan blade staggering and mass flow rates, revealed that the main impacted areas are found along the blade leading edge, over a strip of the blade suction side and a large area of the pressure side, in addition to the tip and casing, but with rare impacts on the hub. The rates of erosion in this axial fan are found to depend strongly on the air flow condition and the blade staggering. In all operating conditions of this axial fan, the rates of erosion are lower in comparison to high speed fans and compressors. Erosion analysis could be used in aerodynamic and mechanical design procedures to produce turbomachinery blading that would be less susceptible to erosion.

scholarly journals Effect of Heat Transfer on the Growing Bubble with the Nanoparticles/Water Nanofluids in Turbulent Flow

2021 ◽  
Vol 8 (1) ◽  
pp. 95-102
Author(s):  
Ahmed K. Abu-Nab ◽  
Ali F. Abu-Bakr
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Turbulent Flow ◽  
Bubble Growth ◽  
Bubble Dynamics ◽  
Pure Water ◽  
Theoretical Data ◽  
Superheated Liquid ◽  
Two Phase ◽  
The Mathematical Model

This paper is devoted to study the effect of heat transfer on the temperature distribution in a superheated liquid during the growth of vapour bubbles immersed in different types of nanoparticles/water nanofluids between two-phase turbulent flow. The mathematical model is formulated and solved analytically depending on Scriven's theory and using the modification of the method of the similarity parameters between two finite boundaries. The characteristics of vapour bubble growth and temperature distribution are obtained by using the thermo-physical properties of nanoparticles nanofluids. The results indicate that the nanoparticle volume concentration reduces the bubble growth process under the effect of heat transfer. The better agreements are achieved, for bubble dynamics in turbulent nanofluid using the appropriate numerical and theoretical data for the values of concentration rate of nanoparticles χ=0,0.2,0.4. The temperature distribution surrounding the regime of bubble growth in pure water is more intensive than in other cases of Al2O3/H2O, Fe3O4/H2O and CuO/H2O nanofluids in turbulent flow. A Comparison of the current solution with previous works is carried out and discussed.

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