Visualization and quantification of separation of liquid-vapor two-phase flow in a vertical header at low inlet quality

2018 ◽  
Vol 85 ◽  
pp. 144-156 ◽  
Author(s):  
Jun Li ◽  
Pega Hrnjak
Keyword(s):  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Liquid Vapor

Heat Transfer for Annular Flow in Microchannel Bends: A Free Energy Minimization Model for Square Channels

2007 ◽  
Author(s):  
Sara Beaini ◽  
Van P. Carey
Keyword(s):  
Heat Transfer ◽  
Free Energy ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Centrifugal Acceleration ◽  
Two Phase ◽  
The Mean ◽  
Flow Morphology ◽  
Liquid Vapor

For annular liquid-vapor two-phase flow in straight microchannels, effects of gravity are generally small compared to viscous and/or inertia forces. In serpentine evaporator or condenser passages with semicircular return bends, the bend radius may be so small that large centrifugal body forces are generated as the fluid flows through the bend region of the passage. This paper summarizes a model analysis based on the premise that flow morphology in the bend is dictated by radial acceleration forces and the thermodynamic Second Law requirement that the established two-phase flow morphology minimizes the free energy at the local temperature and pressure. An analytical model is derived relating the dependence of the free energy on vapor core geometry, and the geometry that minimizes free energy is determined numerically. This provides a prediction of the mean thickness of the liquid surrounding the vapor core, and the mean heat transfer coefficient for annular flow vaporization or condensation, as a function of flow parameters and physical properties. When this relation is cast in dimensionless form, the effect of centrifugal acceleration is quantified in terms of a Weber number (We) that represents the ratio of centrifugal body force to surface tension force. The analysis indicates that centrifugal acceleration acts to displace the vapor towards the inside of the curved passage and distort the liquid-vapor interface. Displacement occurs at any level of acceleration. Significant distortion is found to occur only for We > 1. The effects of these morphology changes on heat transfer are analyzed and the implications of these predictions for designing microchannel evaporators and condensers are explored.

Analysis of Two-Phase Flow in Cryogenic Damper Seals—Part I: Theoretical Model

1998 ◽  
Vol 120 (2) ◽  
pp. 221-227 ◽  
Author(s):  
Grigory L. Arauz ◽  
Luis San Andre´s
Keyword(s):  
Two Phase Flow ◽  
Flow Region ◽  
Forced Response ◽  
Dynamic Force ◽  
Phase Flow ◽  
Two Phase ◽  
Fluid Damper ◽  
Theoretical Predictions ◽  
Saturated Mixture ◽  
Liquid Vapor

Cryogenic fluid damper seals operating close to the liquid-vapor region (near the critical point or slightly sub-cooled) are likely to develop a two-phase flow region which affects the seal performance and reliability. An all-liquid, liquid-vapor, and all-vapor, i.e., a “continuous vaporization” bulk flow model is presented for prediction of the seal dynamic forced response. Continuity, momentum, and energy (enthalpy) transport equations govern the two-phase flow of a homogeneous saturated mixture in thermodynamic equilibrium. Static and dynamic force performance characteristics for the seal are obtained from a perturbation analysis of the governing equations. Theoretical predictions and comparisons to experimental measurements in a liquid and gaseous nitrogen seal are presented in Part II. The effects of two-phase flow regimes on the dynamic force coefficients and stability of an oxygen damper seal are also discussed.

Analysis of two phase flow in liquid oxygen hybrid journal bearings for rocket engine turbopumps

2014 ◽  
Vol 66 (1) ◽  
pp. 31-37 ◽  
Author(s):  
Zhang Guoyuan ◽  
Yan Xiu-Tian
Keyword(s):  
Two Phase Flow ◽  
Rocket Engine ◽  
Dynamic Performance ◽  
Liquid Oxygen ◽  
Phase Flow ◽  
Vapor Mixture ◽  
Two Phase ◽  
Content Type ◽  
Hybrid Bearing ◽  
Liquid Vapor

Purpose – A hybrid bearing of advanced cryogenic rocket engine turbopump is designed. For cryogenic fluid propellants (such as liquid oxygen) as the lubrication of bearing, bearings operating close to liquid-vapor region (near the critical point or slightly sub-cooled) are likely to develop a two phase flow region. The paper aims to discuss these issues. Design/methodology/approach – In this paper, an all liquid, liquid-vapor mixture, and all vapor, i.e. a continuous vaporization bulk flow model of density and viscosity for mixture fluid, is presented, and the general Reynolds equation and energy equation with two phase flow as lubricants is solved. The static and dynamic performance of a 50-mm-radius hybrid bearing are obtained under 20,000 rpm speed and 10 MPa supply pressure. Findings – The results show that the variations of performance of bearing operating under cryogenic liquid oxygen are not bounded by the all liquid and all vapor cases in the liquid-vapor mixture range. There behaviours are attributed to the large change in the compressibility character of the flow. Research limitations/implications – For validating the correctness of analytical model, an experimental study on the liquid-vapor nitrogen mixture lubricated hybrid journal bearings is being carried out where low-viscosity nitrogen was selected as the lubricant for the sake of safety. Soon after, the authors will discuss the results and publish them in the new papers. Originality/value – An all liquid, liquid-vapor mixture, and all vapor, i.e. a continuous vaporization bulk flow model of density and viscosity for mixture fluid, is presented. The static and dynamic performance of hybrid bearings with two phase flow as lubricants are obtained.

Control of Adiabatic Liquid/Vapor Flow Utilizing EHD Conduction Pumping Mechanism

2004 ◽  
Author(s):  
Yinshan Feng ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Mass Flux ◽  
Two Phase Flow ◽  
Finite Thickness ◽  
Flow Distribution ◽  
Vapor Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Phase Liquid ◽  
Liquid Vapor

Unlike the electrohydrodynamic (EHD) induction and iondrag pumping, the conduction pumping is associated with the heterocharge layers of finite thickness in the vicinity of the electrodes which are based on the process of dissociation of the neutral electrolytic species and recombination of the generated ions. The conduction term here represents a mechanism for electric current flow in which charged carriers are produced not by injection from electrodes, but by dissociation of molecules within the fluid. This paper presents the control of adiabatic two-phase (liquid/vapor) flow distribution with EHD conduction pumping mechanism at two mass flux levels, Gtotal = 50 kg/m2s and Gtotal = 100 kg/m2s. The effects of the vapor quality, ranging from 0 to 26%, on the EHD conduction pumping have also been experimentally investigated. The measured pressure data show that the EHD conduction pumping can significantly decrease the pressure drop of the two-phase flow. It is also found that the performances of the EHD conduction pump are related to the mass flux and quality of two-phase flow.

Complete Condensation of Forced Convection Two-Phase Flow in a Miniature Tube

1999 ◽  
Vol 121 (4) ◽  
pp. 904-915 ◽  
Author(s):  
E. Begg ◽  
D. Khrustalev ◽  
A. Faghri
Keyword(s):  
Two Phase Flow ◽  
Film Condensation ◽  
Vapor Flow ◽  
Pressure Jump ◽  
Phase Flow ◽  
Two Phase ◽  
Vapor Interface ◽  
Complete Condensation ◽  
Annular Film ◽  
Liquid Vapor

A physical and mathematical model of annular film condensation in a miniature tube has been developed. In the model the liquid flow has been coupled with the vapor flow along the liquid-vapor interface through the interfacial temperature, heat flux, shear stress, and pressure jump conditions due to surface tension effects. The model predicts the shape of the liquid-vapor interface along the condenser and the length of the two-phase flow region. The numerical results show that complete condensation of the incoming vapor is possible at comparatively low heat loads. Observations from a flow visualization experiment of water vapor condensing in a horizontal glass tube confirm the existence and qualitative features of annular film condensation leading to the complete condensation phenomenon in small diameter (d < 3.5 mm) circular tubes.

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