Experiment and Numerical Study of Annular Flow Entrainment Mechanism in Oil-Air Lubrication Pipe

2011 ◽  
Vol 189-193 ◽  
pp. 1782-1785
Author(s):  
Lin Cai ◽  
Jin Li Wang ◽  
Hong Tao Zheng
Keyword(s):  
Annular Flow ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Air Flow ◽  
Air Flow Rate ◽  
Air Velocity ◽  
Two Phase ◽  
Vof Model ◽  
Air Lubrication ◽  
Delivery Pipe

Annular flow is a based flow pattern of two-phase in the pipe, and oil air flow in delivery pipe of Oil-Air lubrication (OAL) system is one of them. In order to learn the entrainment mechanism of annular flow in OAL pipe, both experiment adopted observational method and numerical simulation used Computational Fluid Dynamic (CFD) were carried out. The pipe diameter is 4mm and Volume of Fluid (VOF) model was used for two phase flow in simulation. The results shows that: it is a wave-annular flow in OAL pipe, and the oil wave in pipe is affected by air, when air velocity is low, the wave is clearly and regularly, but when air velocity increases, the wave become turbulent. When oil or air flow rate increases, the shear stress of pipe wall will be increased, the wave height will be increased as air velocity increases.

scholarly journals Model of thermal buoyancy in cavity-ventilated roof constructions

2021 ◽  
pp. 174425912098418
Author(s):  
Toivo Säwén ◽  
Martina Stockhaus ◽  
Carl-Eric Hagentoft ◽  
Nora Schjøth Bunkholt ◽  
Paula Wahlgren
Keyword(s):  
Analytical Model ◽  
Flow Rate ◽  
Numerical Study ◽  
Air Flow ◽  
Wind Pressure ◽  
Air Flow Rate ◽  
Test Set ◽  
Air Cavity ◽  
Thermal Buoyancy ◽  
The Impact

Timber roof constructions are commonly ventilated through an air cavity beneath the roof sheathing in order to remove heat and moisture from the construction. The driving forces for this ventilation are wind pressure and thermal buoyancy. The wind driven ventilation has been studied extensively, while models for predicting buoyant flow are less developed. In the present study, a novel analytical model is presented to predict the air flow caused by thermal buoyancy in a ventilated roof construction. The model provides means to calculate the cavity Rayleigh number for the roof construction, which is then correlated with the air flow rate. The model predictions are compared to the results of an experimental and a numerical study examining the effect of different cavity designs and inclinations on the air flow rate in a ventilated roof subjected to varying heat loads. Over 80 different test set-ups, the analytical model was found to replicate both experimental and numerical results within an acceptable margin. The effect of an increased total roof height, air cavity height and solar heat load for a given construction is an increased air flow rate through the air cavity. On average, the analytical model predicts a 3% higher air flow rate than found in the numerical study, and a 20% lower air flow rate than found in the experimental study, for comparable test set-ups. The model provided can be used to predict the air flow rate in cavities of varying design, and to quantify the impact of suggested roof design changes. The result can be used as a basis for estimating the moisture safety of a roof construction.

scholarly journals Contribution to the Sustainability of Agricultural Production in Greenhouses Built on Slope Soils: A Numerical Study of the Microclimatic Behavior of a Typical Colombian Structure

2021 ◽  
Vol 13 (9) ◽  
pp. 4748
Author(s):  
Edwin Villagran ◽  
Carlos Bojacá ◽  
Mohammad Akrami
Keyword(s):  
Latin American ◽  
Crop Yields ◽  
Numerical Study ◽  
Air Flow ◽  
Research Work ◽  
Flow Patterns ◽  
Soil Conditions ◽  
Air Velocity ◽  
The Hours ◽  
Microclimatic Conditions

The use of covered structures is an alternative increasingly used by farmers to increase crop yields per unit area compared to open field production. In Latin American countries such as Colombia, productive areas are located in with predominantly hillside soil conditions. In the last two decades, farmers have introduced cover structures adapted to these soil conditions, structures for which the behavior of factors that directly affect plant growth and development, such as microclimate, are still unknown. Therefore, in this research work, a CFD-3D model successfully validated with experimental data of temperature and air velocity was implemented. The numerical model was used to determine the behavior of air flow patterns and temperature distribution inside a Colombian passive greenhouse during daytime hours. The results showed that the slope of the terrain affects the behavior of the air flow patterns, generating thermal gradients inside the greenhouse with values between 1.26 and 16.93 °C for the hours evaluated. It was also found that the highest indoor temperature values at the same time were located in the highest region of the terrain. Based on the results of this study, future researches on how to optimize the microclimatic conditions of this type of sustainable productive system can be carried out.

scholarly journals Automobile Radiator’s Engineering and Analysation

2020 ◽  
Vol 9 (5) ◽  
pp. 554-558
Keyword(s):  
Flow Rate ◽  
Heat Dissipation ◽  
Cooling System ◽  
Volume Flow Rate ◽  
Air Flow ◽  
Temperature Drop ◽  
Inlet Temperature ◽  
Air Flow Rate ◽  
Air Velocity ◽  
Cooling Fan

The shape of a radiator cover is crucial either in determining the pattern of air flow or in increasing the same through the radiator core thereby increasing the thermal efficiency, thus making it a necessity to understand it. Moreover the parts circumjacent to the core namely the upper tank, lower tank, cooling fan, fins, tubes, etc promote the air flow rate. Also it is to note that the air flow rate of discharge gases from radiator core is one of the prime factors in determining the automobile cooling system. Initially factors such as temperature, pressure, air flow rate that affect the performance are obtained in order to derive out the entities of operation. One of the observations that can be made through this paper is that as the volume of the coolant increases, the rate of heat dissipation increases, also parameters like inlet temperature and volume flow rate of coolant, air velocity, temperature drop and drop in pressure of coolant are factors that contribute in radiator performance evidently.

Numerical Simulation of Black Liquor Spray Characteristics

2002 ◽  
Author(s):  
Thomas D. Foust ◽  
Kurt D. Hamman ◽  
Brent A. Detering
Keyword(s):  
Droplet Size ◽  
Volume Fraction ◽  
Numerical Study ◽  
Black Liquor ◽  
Flow Distribution ◽  
Physical Models ◽  
Spray Characteristics ◽  
Two Phase ◽  
Vof Model ◽  
Sheet Breakup

The performance and capacity of Kraft recovery boilers is sensitive to black liquor velocity, droplet size and flow distribution in the furnace. Studies have shown that controlling droplet size and flow distribution improves boiler efficiency while allowing increased flight drying and devolatilization, and decreased carryover. The purpose of this study is to develop a robust two-phase numerical model to predict black liquor splashplate nozzle spray characteristics. A three-dimensional time dependent numerical study of black liquor sheet formation and sheet breakup is described. The volume of fluid (VOF) model is used to simulate flow through the splashplate nozzle up to initial sheet breakup and droplet formation. The VOF model solves the conservation equations of volume fraction and momentum utilizing the finite volume technique. Black liquor velocity, droplet size and flow distribution over a range of operating parameters are simulated using scaled physical models of splashplate nozzles. The VOF model is compared to results from a flow visualization experiment and experimental data found in the literature. The details of the simulation and experimental results are presented.

Particles Capturing and Correlation with Head Loss in a Pilot-Scale Biological Aerated Filter

2013 ◽  
Vol 409-410 ◽  
pp. 279-286
Author(s):  
Ting Li ◽  
Wen Yi Dong ◽  
Hong Jie Wang ◽  
Jin Nan Lin ◽  
Feng Ouyang ◽  
...  
Keyword(s):  
Flow Rate ◽  
Air Flow ◽  
Pilot Scale ◽  
Head Loss ◽  
Biological Aerated Filter ◽  
Air Flow Rate ◽  
Air Velocity ◽  
Lower Velocity ◽  
Aerated Filter ◽  
Filter Bed

Experimental observations of particle capturing through the biological aerated filter bed indicated that air flow rate plays an important role in head loss development by influencing the suspended solids distribution along the depth of the bed as well as the morphology of the deposits. The active height for the SS removal prolonged with the increasing of the air velocity based on the mechanism of first-order kinetics. With the increasing of the superficial air velocity, the effluent SS concentration and the time need to reach the stead-states after backwash both increased. The value of the SS spike in the effluent after backwash at superficial air velocity of 27 m/hr was nearly twice as much as that of 5.4m/hr. Distribution of the deposits at higher air velocity was more uniform. Deposits at lower velocity with air flow rate produced higher head loss gradient. The headloss increased with the increasing of deposits and the increase rate was faster when the deposits exceeded higher value.

Propeller Effect on 3D Flow at the Stern Hull of a LNG Carrier Using Finite Volume Method

2014 ◽  
Vol 554 ◽  
pp. 566-570
Author(s):  
Mehdi Nakisa ◽  
Adi Maimun Abdul Malik ◽  
Yasser M. Ahmed ◽  
Sverre Steen ◽  
Fatemeh Behrouzi ◽  
...  
Keyword(s):  
Viscous Flow ◽  
Finite Volume ◽  
Cfd Simulation ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Computational Domain ◽  
Two Phase ◽  
Sst Turbulence Model

Numerical study and RANS simulations have been applied to investigate the incompressible free surface flow around the stern hull of Liquefied Natural Gas (LNG) ship affected by working propeller behind of her. Experimental works are carried out using LNG ship model in Marine Teknologi Center (MTC) of Univrsiti Teknologi Malaysia (UTM) to verify the computational fluid dynamic (CFD) results. Ansys-CFX 14.0 based on viscous flow finite volume code using the two-phase Eulerian–Eulerian fluid approach and shear stress transport (SST) turbulence model have been used in this study. A tetrahedral unstructured combined with prism grid were used with the viscous flow code for meshing the computational domain of water surface around it. CFD simulation has been verified using available experimental results. Finally, the flow structure, streamlines, velocity and pressure distribution around stern hull and propeller zone are discussed and analysed.

scholarly journals Investigations of hydraulic operating conditions of air lift pump with three types of air-water mixers

2015 ◽  
Vol 47 (1) ◽  
pp. 69-85 ◽  
Author(s):  
Marek Kalenik
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
Air Flow ◽  
Operating Conditions ◽  
Water Delivery ◽  
Air Flow Rate ◽  
Analysis Of Results ◽  
Delivery Pipe ◽  
Air Lift

Abstract: Investigations of hydraulic operating conditions of air lift pump with three types of air-water mixers. The paper presents the analysis of results of the investigations concerning the influence of various constructive solutions of the air-water mixers on hydraulic operating conditions of the air lift pump. The scope of the investigations encompassed the determination of characteristics of delivery head and delivery rate for three types of air-water mixers applied in the constructed air lift pump. Using the obtained results, the efficiency of the three types of air-water mixers applied in this air lift pump was determined. The analysis was carried out and there was checked whether the improved analytical Stenning-Martin model can be used to design air lift pumps with the air-water mixers of these types. The highest capacity in the water transport was reached by the air lift pump with the 1st type air-water mixer, the lowest one – with the 3rd type air-water mixer. The water flow in the air lift pump increases along with the rise in the air flow. The lower are the hydraulic losses generated during flow of the air flux by the air-water mixer, the higher is the air lift pump capacity. Along with the rise in the water delivery head, the capacity of the air lift pump decreases. The highest efficiency is reached by the air lift pump with the 1st type air-water mixer, the lowest – with the 3st type air-water mixer. The efficiency of the air lift pump for the three investigated types of air-water mixers decreases along with the rise in air flow rate and water delivery head. The values of submergence ratio (h/L) of the delivery pipe, calculated with the use of the improved analytical Stenning-Martin model, coincide quite well with the values of h/L determined from the measurements.

Development of Air/Water Two-Phase Flow Centrifugal Pump and Its Operating Characteristics

2003 ◽  
Author(s):  
Akinori Furukawa ◽  
Satoshi Ohshita ◽  
Kusuo Okuma ◽  
Satoshi Watanabe
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
Two Phase Flow ◽  
Air Flow ◽  
Water Flow Rate ◽  
Phase Flow ◽  
Air Flow Rate ◽  
Operating Characteristics ◽  
Two Phase ◽  
Flow Pump

A centrifugal impeller, the pumping action of which could be highly kept even at an air-water two-phase flow condition of inlet void fraction more than 30% in the region of relatively high water flow rate, has been developed. In the present paper, the design concept of two-phase flow impeller is described, at first, with experimental results. The short bladed forward impeller with high outlet blade angle was decided to keep theoretical head higher even in two-phase flow condition and to disperse the air accumulating region on the suction blade surface by the water jet flow coming from the pressure side. Furthermore, the tandem arrangement of outer and inner rotating cascades with the same blade numbers was adopted to suppress the rotating stall phenomena appearing in the case of a single stage of outer cascade. It should be noted that these results were obtained with operating a boost pump installed upstream of mixing section of air and water, that is not an actual operation of two-phase flow pump. Secondly, the operating characteristics of this two-phase flow pump with change of air flow rate were investigated experimentally without operating the boost pump. As the trajectory of operating point with increasing air flow rate appears along the resistance curve of piping system, the impossibility of pumping occurs at lower air flow rate even though pump head takes a positive value at high air flow rate with increasing water flow rate. It is recognized that it is necessary to improve two-phase flow head characteristic curves in the region of low water flow rate to operate in wider two-phase flow conditions.

A Numerical Study of Concurrent Flame Propagation Over Methanol Pool Surface

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Seik Mansoor Ali ◽  
Vasudevan Raghavan ◽  
K. Velusamy ◽  
Shaligram Tiwari
Keyword(s):  
Flame Spread ◽  
Numerical Study ◽  
Leading Edge ◽  
Reacting Flow ◽  
Atmospheric Conditions ◽  
Air Velocity ◽  
Two Phase ◽  
Spread Velocity ◽  
Pool Surface ◽  
Initial Flame

Concurrent flame spread over methanol pool surface under atmospheric conditions and normal gravity has been numerically investigated using a transient, two-phase, reacting flow model. The average flame spread velocities for different concurrent air velocities predicted using the model are quite close to the experimental data available in the literature. As the air velocity is increased, the fuel consumption rate increases and aids in faster flame spread process. The flame initially anchors around the leading edge of the pool and the flame tip spreads over the pool surface. The rate of propagation of flame tip along the surface is seen to be steady without fluctuations. The flame spread velocity is found to be nonuniform as the flame spreads along the pool surface. The flame spread velocity is seen to be higher initially. It then decreases up to a point when the flame has propagated to around 40% to 50% of the pool length. At this position, a secondary flame anchoring point is observed, which propagates toward the trailing edge of the pool. As a result, there is an increasing trend observed in the flame spread velocity. As the air velocity is increased, the initial flame anchoring point moves downstream of the leading edge of the fuel pool. The variations of interface quantities depend on the initial flame anchoring location and the attainment of thermodynamic equilibrium between the liquid- and gas-phases.

Analysis for the Fluctuation Characteristics of Annular Flow in the Oil-Air Lubrication System

2014 ◽  
Vol 487 ◽  
pp. 408-412
Author(s):  
Qi Guo Sun ◽  
Ali Cai ◽  
Zheng Hui Zhou ◽  
Zhi Hong Li ◽  
Xiong Shi Wang
Keyword(s):  
Pressure Drop ◽  
Film Thickness ◽  
Liquid Film ◽  
Annular Flow ◽  
Lubrication System ◽  
Air Velocity ◽  
Film Distribution ◽  
Air Lubrication ◽  
Calculation Results ◽  
Simulation Results

Fluctuation characteristics of the pressure drop distribution and liquid film distribution along a pipe of the oil-air annular flow in oil-air lubrication system are calculated respectively introducing Chisholm constant c base on the Chisholm theory and simulated by Fluent in this paper. The results show that the theoretical calculation results of the pressure drop and liquid film agree qualitatively with the simulation results, and the fluctuation characteristics of the pressure drop and liquid film thickness are augmented respectively when the air velocity increases. These conclusions will do favors for predicting and controlling the lubricant in the oil-air lubrication system.

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