Phenomenon of Fog Formation and Flow Characteristics of Droplet-Vapor-Gas Mixture in a Cooler-Condenser

2019 ◽  
Author(s):  
Hongfang Gu ◽  
Qiwei Guo ◽  
Changsong Li ◽  
Qing Zhou
Keyword(s):  
Experimental Data ◽  
Numerical Analysis ◽  
High Speed ◽  
Flow Characteristics ◽  
Saturation Temperature ◽  
Bulk Temperature ◽  
Dropwise Condensation ◽  
Operation Conditions ◽  
Droplet Transport ◽  
Wide Range

Abstract Fog formation occurs in the process of condensation in the presence of non-condensable gas if the bulk temperature is lower than its saturation temperature (supersaturated). The phenomena of fogging is the formation of small condensate particles mixing with the vapor/gas stream, which creates potential problems of the vapor/gas/condensate separation and environmental pollution. Therefore, understanding of fogging mechanism and prevention of fog droplet entrainment are one of technical concerns for design and operation of cooler-condensers in the process industry. This paper presents the experimental study and numerical simulation of shell-side condensation with fog formation using a mixture of steam/non-condensable gas. The experimental data were collected on the two tube bundles (modified plastic tubes and stainless steel tubes). Using a high-speed photograph technique, the phenomenon of fog formation and flow characteristics of vapor/droplet transport were recorded over a wide range of test conditions. The numerical analysis of film and dropwise condensation, fog formation and droplet particle transport were simulated using different tube geometry and material, and flow velocity of air/droplet mixture. Based on simulation results, a new droplet trapping parameter is proposed to assess the optimal parameters of heat exchanger structural and operation conditions. Comparisons show that the numerical analysis results have a good agreement with experimental data and observations. These findings provide fundamental approach to account for the effect of fog formation, film and dropwise condensation, and droplet transport crossflow in cooler-condensers.

Experimental Study of Shell-Side Fogging Condensation of a Mixture

2017 ◽  
Author(s):  
Hongfang Gu ◽  
Haiyang Guo ◽  
Haijun Wang ◽  
Yuqiang Gu
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Vapor Pressure ◽  
Gas Phase ◽  
High Speed ◽  
Saturated Vapor ◽  
Saturation Temperature ◽  
Bulk Temperature ◽  
Transfer Performance ◽  
Shell Side

Fog formation occurs if the vapor pressure in the gas-phase is higher than the saturated vapor pressure and the bulk temperature is lower than its saturation temperature (supersaturated) for condensation in the presence of non-condensable gases. Generally, fogging is formation of entrained small droplets mixing in the vapor-gas stream, and the vapor condenses at the mist-flow and share-controlled flow regime. The phenomenon and mechanism of fogging need to be considered for determining condensation rate and separation of the condensate from vapor-gas phase for the down-stream process. The experimental study of shell-side condensation using steam mixing with non-condensable air was conducted in a shell-side horizontal baffled tube bundle. Experimental data has been obtained including visualization findings using high-speed photograph. The characteristics of fog formation related to the heat and mas transfer performance are analyzed based on experimental data and observation. The general equation for determining fog formation (degree of supersaturation) is evaluated with experimental data. Results confirm that the transition band of fogging formation is in the range of S = 1.0 to 1.75. This paper presents experimental data and visualization findings on fogging characteristics and heat transfer performance for condensation in the presence of non-condensable gas.

Flow Characteristics of Rectangular Liquid Jets Injected Into Low Subsonic Crossflow

2019 ◽  
Author(s):  
M. Tadjfar ◽  
A. Jaberi ◽  
R. Shokri
Keyword(s):  
High Speed ◽  
Flow Characteristics ◽  
Combustion Efficiency ◽  
Liquid Jets ◽  
High Speed Photography ◽  
Aspect Ratios ◽  
Jet Trajectory ◽  
Wide Range ◽  
Circular Holes ◽  
Subsonic Crossflow

Abstract Perpendicular injection of liquid jets into gaseous crossflow is well-known as an effective way to obtain good mixing between liquid fuel and air crossflow. Mostly, injectors with circular holes were used as the standard method of fuel spraying. However, recently a great attention to injectors with non-circular holes has emerged that aims to improve the quality of fuel mixing and consequently combustion efficiency. In the present work, rectangular injectors with different aspect ratios varying from 1 to 4 were experimentally studied. Using a wind tunnel with maximum air velocity of 42 m/s, tests were performed for a wide range of flow conditions including liquid-to-air momentum ratios of 10, 20, 30 and 40. Backlight shadowgraphy and high speed photography were employed to capture the instantaneous physics of the liquid jets discharged into gaseous crossflow. The flow physics of the rectangular liquid jets were investigated by means of flow visualizations. Different regimes of flow breakup including capillary, arcade, bag and multimode were observed for rectangular jets. Moreover, a new technique was used to calculate the trajectory of the liquid jets. It was shown the nozzle’s shape has no significant effect on jet trajectory. Also, the momentum ratio was found to has a profound effect on jet trajectory.

Study of Flow Characteristics and Control Circuit on High-Speed Solenoid Valve

2012 ◽  
Vol 619 ◽  
pp. 107-110 ◽  
Author(s):  
Wen Hua Li ◽  
Wen Lin Shao
Keyword(s):  
High Speed ◽  
Flow Characteristics ◽  
Pulse Signal ◽  
Solenoid Valve ◽  
Control Circuit ◽  
Duty Ratio ◽  
Time Sharing ◽  
Small Current ◽  
Wide Range ◽  
And Control

Through the analysis of the flow characteristics of the high-speed solenoid valve, the conclusions that the PWM signal duty ratio is the main factor affecting the solenoid valve flow is obtained, a new available any PWM pulse signal and control circuit are proposed. Further, circuit schematic is simulated by means of SIMULINK tools in MATLAB environment and Verify its stability. A time-sharing drive circuit is design based on the PWM drive mode. The driver circuit have function which is high-current open, small current maintain. Open current and maintain current of Solenoid valve can be adjusted through this circuit. Therefore, the circuit can adapt to different parameters of the solenoid valve. A wide range of applications.

On the Water-Entry-Induced Cavity Closure for a Wide Range of Entry Speeds

2003 ◽  
Vol 125 (5) ◽  
pp. 927-930 ◽  
Author(s):  
M. Lee
Keyword(s):  
Experimental Data ◽  
High Speed ◽  
Water Entry ◽  
Ambient Atmosphere ◽  
Important Research ◽  
Atmosphere Pressure ◽  
Research Areas ◽  
Wide Range ◽  
Entry Speed ◽  
Cavity Closure

One of the important research areas in the water-entry problem is the cavity dynamics. A theoretical analysis is presented to predict the dynamics of water-entry cavity up to the first cavity closure, which is generated by a solid body entering a semi-inifinite free surface of water at a wide range of entry speed. Two types of cavity closure, which are surface closure and the deep closure, depending on the magnitude of ambient atmosphere pressure and entry speed are described by the proposed theory. The time of surface closure at the relatively low-speed entry regime is estimated and compared with published experimental data. Currently no experimental data are available for the high-speed entry case.

Condensate Drop Movement on Heat Transfer Surface With Bulk Temperature Gradient in Marangoni Dropwise Condensation

2010 ◽  
Author(s):  
Zhihao Chen ◽  
Yoshio Utaka
Keyword(s):  
Heat Transfer ◽  
Surface Tension ◽  
Temperature Gradient ◽  
Heat Transfer Surface ◽  
Surface Tension Gradient ◽  
Bulk Temperature ◽  
Dropwise Condensation ◽  
Wide Range ◽  
Initial Drop ◽  
Temperature Side

When a bulk temperature gradient was applied to a horizontal condensing surface in Marangoni dropwise condensation, the spontaneous movement of condensate drops occurred. The characteristics of the condensate drop movement in a condensate system of water and ethanol binary vapor mixture were experimentally investigated for a wide range of bulk temperature gradients and for various mass fractions. Drops moved from the low-temperature side to the high-temperature side of the heat transfer surface. When the initial drop distance was adopted as a parameter for the Marangoni force acting on the condensate drop together with the surface tension gradient corresponding to the surface temperature of the condensing surface, the drop moving velocity correlated well as a function of both the surface tension gradient and the initial drop distance. In the range of larger initial drop distances, the condensate drop velocity increases as the initial drop distance is reduced and it subsequently decreases after the velocity reaches its maximum value under an almost constant bulk surface tension gradient.

scholarly journals Internal flow characteristics in scaled pressure-swirl atomizer

2018 ◽  
Vol 180 ◽  
pp. 02059 ◽  
Author(s):  
Milan Malý ◽  
Marcel Sapík ◽  
Jan Jedelský ◽  
Lada Janáčková ◽  
Miroslav Jícha ◽  
...  
Keyword(s):  
High Speed ◽  
Laser Doppler Anemometry ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Liquid Sheet ◽  
Wide Range ◽  
Swirl Atomizer ◽  
Pressure Swirl ◽  
Pressure Swirl Atomizer ◽  
Working Liquid

Pressure-swirl atomizers are used in a wide range of industrial applications, e.g.: combustion, cooling, painting, food processing etc. Their spray characteristics are closely linked to the internal flow which predetermines the parameters of the liquid sheet formed at the discharge orifice. To achieve a better understanding of the spray formation process, the internal flow was characterised using Laser Doppler Anemometry (LDA) and high-speed imaging in a transparent model made of cast PMMA (Poly(methyl methacrylate)). The design of the transparent atomizer was derived from a pressure-swirl atomizer as used in a small gas turbine. Due to the small dimensions, it was manufactured in a scale of 10:1. It has modular concept and consists of three parts which were ground, polished and bolted together. The original kerosene-type jet A-1 fuel had to be replaced due to the necessity of a refractive index match. The new working liquid should also be colourless, non-aggressive to the PMMA and have the appropriate viscosity to achieve the same Reynolds number as in the original atomizer. Several liquids were chosen and tested to satisfy these requirements. P-Cymene was chosen as the suitable working liquid. The internal flow characteristics were consequently examined by LDA and high-speed camera using p-Cymene and Kerosene-type jet A-1 in comparative manner.

Laminar flow in rotating curved pipes

1996 ◽  
Vol 329 ◽  
pp. 373-388 ◽  
Author(s):  
Hiroshi Ishigaki
Keyword(s):  
Experimental Data ◽  
Laminar Flow ◽  
Friction Factor ◽  
Flow Structure ◽  
Flow Characteristics ◽  
Laminar Flows ◽  
Dean Number ◽  
Governing Parameter ◽  
Curved Pipes ◽  
Wide Range

When a curved pipe rotates about the centre of curvature, the fluid flowing in it is subjected to both Coriolis and centrifugal forces. Based on the analogy between laminar flows in stationary curved pipes and in orthogonally rotating pipes, the flow characteristics of fully developed laminar flow in rotating curved pipes are made clear and definite by similarity arguments, computational studies and using experimental data. Similarity arguments clarify that the flow characteristics in loosely coiled rotating pipes are governed by three parameters: the Dean number KLC, a body force ratio F and the Rossby number Ro. As the effect of Ro is negligible when Ro is large, computational results are presented for this case first, and then the effect of Ro is studied. Flow structure and friction factor are studied in detail. Variations of flow structure show secondary flow reversal at F ≈ −1, where the two body forces are of the same order but in opposite directions. It is also shown how the Taylor–Proudman effect dominates the flow structure when Ro is small. Computed curves of the friction factor for constant Dean number have their minimum at F ≈ −1. A composite parameter KL is introduced as a convenient governing parameter and used to correlate the characteristics. By applying KL to the analogy formula previously derived for two limiting flows, a semi-empirical formula for the friction factor is presented, which shows good agreement with the experimental data for a wide range of the parameters.

Numerical simulation of sharp-crested weir flows

2009 ◽  
Vol 36 (9) ◽  
pp. 1530-1534 ◽  
Author(s):  
J. Qu ◽  
A.S. Ramamurthy ◽  
R. Tadayon ◽  
Z. Chen
Keyword(s):  
Experimental Data ◽  
Turbulence Model ◽  
Open Channel ◽  
Flow Characteristics ◽  
Pressure Head ◽  
Flow Parameters ◽  
Weir Flow ◽  
Wide Range ◽  
And Control ◽  
Measurement And Control

The sharp-crested weir in a rectangular open channel can be used as a simple and accurate device for flow measurement and control in open channels. However, in the past, the solution to this problem was found mainly on the basis of experimental data or through the development of simplified theoretical expressions. In the present study, k-ε turbulence model is applied to obtain the flow parameters such as pressure head distributions, velocity distributions, and water surface profiles. The predictions of the proposed numerical model are validated using existing experimental data. The k-ε turbulence model developed is used to predict the characteristics of a sharp-crested weir in a rectangular open channel. The volume of fluid (VOF) scheme is used to find the shape of the free surface. A properly validated model permits one to obtain the flow characteristics of the sharp-crested weir for a wide range of weir and hydraulic parameters without recourse to expensive and more time consuming experimental methods. Further, the model permits one to incorporate small changes in the geometric parameters involving small changes in inlet and outlet conditions and study their impact on the weir flow characteristics.

scholarly journals Review and a Theoretical Approach on Pressure Drop Correlations of Flow through Open-Cell Metal Foam

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3153
Author(s):  
Huizhu Yang ◽  
Yongyao Li ◽  
Binjian Ma ◽  
Yonggang Zhu
Keyword(s):  
Experimental Data ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Metal Foam ◽  
Flow Characteristics ◽  
Metal Foams ◽  
High Porosity ◽  
Open Cell ◽  
Wide Range ◽  
Flow Through

Due to their high porosity, high stiffness, light weight, large surface area-to-volume ratio, and excellent thermal properties, open-cell metal foams have been applied in a wide range of sectors and industries, including the energy, transportation, aviation, biomedical, and defense industries. Understanding the flow characteristics and pressure drop of the fluid flow in open-cell metal foams is critical for applying such materials in these scenarios. However, the state-of-the-art pressure drop correlations for open-cell foams show large deviations from experimental data. In this paper, the fundamental governing equations of fluid flow through open-cell metal foams and the determination of different foam geometry structures are first presented. A variety of published models for predicting the pressure drop through open-cell metal foams are then summarized and validated against experimental data. Finally, two empirical correlations of permeability are developed and recommended based on the model of Calmidi. Moreover, Calmidi’s model is proposed to calculate the Forchheimer coefficient. These three equations together allow calculating the pressure drop through open-cell metal foam as a function of porosity and pore diameter (or strut diameter) in a wide range of porosities ε = 85.7–97.8% and pore densities of 10–100 PPI. The findings of this study greatly advance our understanding of the flow characteristics through open-cell metal foam and provide important guidance for the design of open-cell metal foam materials for different engineering applications.

Unified approach for conjugate heat-transfer analysis of high speed air flow through a water-cooled nozzle

2016 ◽  
Vol 120 (1224) ◽  
pp. 355-373
Author(s):  
F. I. Barbosa ◽  
E. L. Zaparoli ◽  
C. R. Andrade
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
High Speed ◽  
Conjugate Heat Transfer ◽  
Cold Water ◽  
Transfer Problem ◽  
Air Flow ◽  
Heat Transfer Analysis ◽  
Bulk Temperature ◽  
Unified Approach

ABSTRACTThis article presents a unified approach to solve steady-state conjugate heat-transfer problem including simultaneously gas, liquid and solid regions in just one 3D domain, distinguished by their particular properties. This approach reduces approximation errors and the time to solve the problem, which characterise iterative methods based on separated domains. The formulation employs RANS equations, realisablek-ε turbulence model and near-wall treatment model. A commercial CFD code solves the pressure-based segregated algorithm combined with spatial discretisation of second order upwind. The problem consists of a convergent-divergent metallic nozzle that contains cooling channels divided in two segments along the wall. The nozzle wall insulates the high-speed hot air flow, dealt as perfect gas, from the two low-speed cold water flows, dealt as compressed liquid, both influenced by transport properties dependent of the local temperature. The verification process uses three meshes with increasing resolutions to demonstrate the independence of the results. The validation process compares the simulation results with experimental data obtained in high-enthalpy wind tunnel, demonstrating good compliance between them. Results for the bulk temperature rise of the water in the second cooling segment of the nozzle showed good agreement with available experimental data. Numerical simulations also provided wall temperature and heat flux for the gas and liquid sides. Besides, distribution of temperature, pressure, density and Mach number were plotted along the nozzle centerline showing a little disturbance downstream the throat. This phenomenon has been better visualised by means of 2D maps of those variables. The analysis of results indicates that the unified approach herein presented can make easier the task of simulating the conjugate convection-conduction heat-transfer in a class of problems related to regeneratively cooled thrust chambers.

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