AN INSTABILITY EFFECT ON TWO-PHASE HEAT TRANSFER FOR SUBCOOLED WATER FLOWING UNDER CONDITIONS OF ZERO GRAVITY
Instabilities in two-phase heat transfer for subcooled water flowing under conditions of zero gravity
HEAT TRANSFER↗
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Flow Boiling and Condensation Experiment (FBCE): Summary of Findings for Flow Boiling based on Completed ISS Experiments
Since 2011, researchers from Purdue University and NASA Glenn Research Center (GRC) have been collaborating to investigate the effects of gravity on several aspects of flow boiling and flow condensation. This massive research endeavor, termed the Flow Boiling and Condensation Experiment (FBCE), has culminated in development of NASA’s largest and most complex facility for investigation of two-phase fluid physics onboard the ISS. FBCE consists of two separate studies: flow boiling, using the Flow Boiling Module (FBM), and flow condensation, using the Condensation Module for Heat Transfer Measurements (CM-HT); this presentation concerns the FBM portion of FBCE. Fitted with FBM, FBCE was launched to the ISS in August 2021 and experiments were successfully performed starting in February 2022 to amass a large microgravity-flow-boiling database supported by extensive visualization of interfacial behavior using high-speed video. Based on FBCE experiments performed previously in Earth gravity and parabolic flight, along with the new ISS data, several empirical correlations, theoretical models, and CFD models have been developed, enabling the prediction of crucial flow boiling parameters, including heat transfer coefficient and critical heat flux (CHF). These predictive tools, which will be summarized in this presentation, are expected to serve as foundation for design of future space systems involving flow boiling.
Two-phase flow and phase transition↗
Detailed Studies on the Structure and Dynamics of Reacting Dusty Flows at Normal and Microgravity
Two-phase reacting flows are substantially less understood compared to gas phase flows. While extensive work has been done on sprays, less attention has been given to the details of dusty reacting flows. Dusty flows are of particular interest for a wide range of applications. Particles can be present in a gas intentionally or unintentionally, and they can be inert or reacting. Inert particles can be also present in an otherwise reacting gas flow, and that can lead to flame cooling and modification of the extinction limits of a combustible mixture. Reacting solid particles can release substantial amounts of heat upon oxidation, and can be used either for propulsion (e.g. Al, B, Mg) or power generation (coal). Furthermore, accidents can occur when a reacting dust accumulates in air and which, in the presence of an ignition source, can cause explosion. Such explosions can occur during lumber milling, in grain elevators, and in mine galleries.
Egolfopoulos, Fokion N.↗
Flow Boiling and Condensation Experiment Overview
A brief overview of the Flow Boiling and Condensation Experiment will be presented at the Technical Interchange Meeting between NASA-GRC Scientists and Engineers and the Korea Aerospace Research Institute (KARI). The presentation describes the development of the FBCE, its constraints, and the on-going testing that had been and continues to be executed onboard of the International Space Station (ISS).
International Space Station↗
Case Study of Using Flocad to Model a Ground Test Station Ln2 Heat Exchanger
This paper presents a case study of using FLOCAD to model the heat transfer and boiling flow behavior of a Liquid Nitrogen (LN2) ground station equipment heat exchanger. The unique aspect of this work is that is one of very few studies documenting the use of FLOCAD in the spacecraft thermal control community. The results of the simulations described herein were used to guide and plan the execution of thermal vacuum testing spacecraft hardware using a ground test heat exchanger such as the one modeled herein. The paper will review the theory of two-phase boiling flow and correlations used by SINDA/FLUINT as well as the terminology and nomenclature used within Thermal Desktop / FLOCAD regarding two-phase boiling flow heat transfer modeling and simulation. Results for using the ground station heat exchanger as a heat sink in a thermal vacuum test set up are shown in order to demonstrate the set-up and execution of a typical FLOCAD model. Results indicate that properly modeling of the two-phase behavior is critical in order to ascertain the time constant associated with the heat exchanger, as well as understanding the temperature distribution across the test equipment and prediction of required LN2 flowrates to be used during testing. The paper is meant to augment the FLOCAD user’s manual and serve as a tutorial for thermal engineers and analysts wishing to learn and apply FLOCAD to industrial problems.
Anderson, Kevin R.↗
Ground Based Studies of Gas-Liquid Flows in Microgravity Using Learjet Trajectories
A 1.27 cm diameter two phase gas-liquid flow experiment has been developed with the NASA Lewis Research Center to study two-phase flows in microgravity. The experiment allows for the measurement of void fraction, pressure drop, film thickness and bubble and wave velocities as well as for high speed photography. Three liquids were used to study the effects of liquid viscosity and surface tension, and flow pattern maps are presented for each. The experimental results are used to develop mechanistically based models to predict void fraction, bubble velocity, pressure drop and flow pattern transitions in microgravity.
Bousman, W. S.↗
Fluid spray simulation with two-fluid nozzles
Two-phase interacting flow inside a two-fluid fuel atomizer was investigated and a correction of aerodynamic and liquid-surface forces with characteristic drop diameter was obtained for liquid-jet breakup in Mach 1 gas flow. Nitrogen gas mass-flux was varied from 6 to 50 g/sq cm sec by using four differently sized two-fluid atomizers with nozzle diameters varyig from 0.32 to 0.56 cm. The correlation was derived by using the acoustic gas velocity, V sub c, as a basic parameter in defining and evaluating the dimensionless product of the Weber (We) and Reynolds (Re) numbers. By using the definition of WeRe, it was found that the ratio of orifice diameter to Sauter mean drop diameter could be correlated with the dimensionless ratio WeRe and the gas to liquid density ratio.
Ingebo, Robert D.↗
Fuel spray simulation with two-fluid nozzles
Two-phase interacting flow inside a two-fluid fuel atomizer was investigated and a correction of aerodynamic and liquid-surface forces with characteristic drop diameter was obtained for liquid-jet breakup in Mach 1 gas flow. Nitrogen gas mass-flux was varied from 6 to 50 g/sq cm sec by using four differently sized two-fluid atomizers with nozzle diameters varying from 0.32 to 0.56 cm. The correlation was derived by using the acoustic gas velocity, V sub c, as a basic parameter in defining and evaluating the dimensionless product of the Weber (We) and Reynolds (Re) numbers. By using the definition of WeRe, it was found that the ratio of orifice diameter to Sauter mean drop diameter could be correlated with the dimensionless ratio WeRe and the gas to liquid density ratio.
Ingebo, Robert D.↗
Inferential Framework for Autonomous Cryogenic Loading Operations
We address problem of autonomous cryogenic management of loading operations on the ground and in space. As a step towards solution of this problem we develop a probabilistic framework for inferring correlations parameters of two-fluid cryogenic flow. The simulation of two-phase cryogenic flow is performed using nearly-implicit scheme. A concise set of cryogenic correlations is introduced. The proposed approach is applied to an analysis of the cryogenic flow in experimental Propellant Loading System built at NASA KSC. An efficient simultaneous optimization of a large number of model parameters is demonstrated and a good agreement with the experimental data is obtained.
Luchinsky, Dmitry G.↗
Controlled 3D nanoparticle deposition by drying of colloidal suspension in designed thin micro-porous architectures
Nanoparticle deposition by drying of colloidal suspension in thin micro-porous architectures has attracted a lot of attention in scientific research as well as industrial applications. However, the underlying mechanisms of such three-dimensional (3D) deposition are not yet fully revealed due to the complexity of the co-occurring processes of two-phase fluid flows, phase change and mass transport. Consequently, the control of 3D nanoparticle deposition remains a challenge. We use a combined experimental and numerical approach to achieve controlled 3D nanoparticle deposition by drying of colloidal suspension in two pillar-based thin micro-porous architectures. By the design of pillar layout, rectangular-spiral and circular-spiral deposition configurations are obtained globally. By varying the surface wettability, vertically symmetric and sloped nanoparticle depositions can be achieved locally. While the numerical modeling reveals the mechanisms of liquid internal flow, as well as the impact of local drying rate on nanoparticle transport, accumulation and final deposition, the experimental results of deposition configurations validate the controlling strategies. This combined experimental and numerical work provides a framework to achieve desired 3D nanoparticle deposition in thin micro-porous architectures, with a thorough understanding of the underlying mechanisms of two-phase fluid flows, phase change and mass transport.
36 MATERIALS SCIENCE↗
A two phase Mach number description of the equilibrium flow of nitrogen in ducts
Some additional thermodynamic properties of the usual two-phase form which is linear in the moisture fraction are derived which are useful in the analysis of many kinds of duct flow. The method used is based on knowledge of the vapor pressure and Gibbs function as functions of temperature. With these, additional two-phase functions linear in moisture fraction are generated, which ultimately reveal that the squared ratio of mixture specific volume to mixture sound speed depends on liquid mass fraction and temperature in the same manner as do many weighted mean two-phase properties. This leads to a simple method of calculating two-phase Mach numbers for various duct flows. The matching of one- and two-phase flows at a saturated vapor point with discontinuous Mach number is also discussed.
Bursik, J. W.↗
Finite element analysis and computer graphics visualization of flow around pitching and plunging airfoils
A general computational method for analyzing unsteady flow around pitching and plunging airfoils was developed. The finite element method was applied in developing an efficient numerical procedure for the solution of equations describing the flow around airfoils. The numerical results were employed in conjunction with computer graphics techniques to produce visualization of the flow. The investigation involved mathematical model studies of flow in two phases: (1) analysis of a potential flow formulation and (2) analysis of an incompressible, unsteady, viscous flow from Navier-Stokes equations.
Bratanow, T.↗
Active Galactic Nucleus Obscuration from Winds: From Dusty Infrared-Driven to Warm and X-Ray Photoionized
We present calculations of active galactic nucleus winds at approx.parsec scales along with the associated obscuration. We take into account the pressure of infrared radiation on dust grains and the interaction of X-rays from a central black hole with hot and cold plasma. Infrared radiation (IR) is incorporated in radiation-hydrodynamic simulations adopting the flux-limited diffusion approximation. We find that in the range of X-ray luminosities L = 0.05-0.6 L(sub Edd), the Compton-thick part of the flow (aka torus) has an opening angle of approximately 72deg - 75deg regardless of the luminosity. At L > or approx. 0.1, the outflowing dusty wind provides the obscuration with IR pressure playing a major role. The global flow consists of two phases: the cold flow at inclinations (theta) > or approx.70deg and a hot, ionized wind of lower density at lower inclinations. The dynamical pressure of the hot wind is important in shaping the denser IR-supported flow. At luminosities < or = 0.1 L(sub Edd) episodes of outflow are followed by extended periods when the wind switches to slow accretion. Key words: acceleration of particles . galaxies: active . hydrodynamics . methods: numerical Online-only material: color figures
Dorodnitsyn, Anton V.↗
Rocket injector anomalies study. Volume 2: Results of parametric studies
The employment of a existing computer program to simulate three dimensional two phase gas spray flows in liquid propellant rocket engines. This was accomplished by modification of an existing three dimensional computer program (REFLAN3D) with Euler/Lagrange approach for simulating two phase spray flow, evaporation and combustion. The modified code is referred to as REFLAN3D-SPRAY. Computational studies of the model rocket engine combustion chamber are presented. The parametric studies of the two phase flow and combustion shows qualitatively correct response for variations in geometrical and physical parameters. The injection nonuniformity test with blocked central fuel injector holes shows significant changes in the central flame core and minor influence on the wall heat transfer fluxes.
Przekwas, A. J.↗
Normal Gravity Testing of a Microchannel Phase Separator for In Situ Resource Utilization
A microchannel separator, with 2.7 millimeters as the smallest dimension, was tested, and a pore throat structure captured and removed liquid from a gas-liquid stream. The microchannel device was tested over a of gas and liquid flow rates ranging from 0.0005 up to 0. 14 volume fraction of liquid. Four liquids were tested with air. The biggest factor affecting the throughput is the capacity of liquid flow through the pore throat, which is dictated by permeability, liquid viscosity, flow area, pore throat thickness, and pressure difference across the pore throat. Typically, complete separation of gas and liquid fractions was lost when the liquid flow rate reached about 40 to 60% of the pore throat capacity. However, this could occur over a range of 10 to 90% utilization of pore throat capacity. Breakthrough occurs in the microchannel phase separator at conditions similar to the annular to plug flow transition of two-phase microgravity pipe flow implying that operating in the proper flow regime is crucial. Analysis indicates that the Bond number did not affect performance, supporting the premise that hydrodynamic, interfacial, and capillary forces are more important than gravity. However, the relative importance of gravity is better discerned through testing under reduced gravity conditions.
TeGrotenhuis, Ward E.↗
Preliminary experimental results for a cryogenic brush seal configuration
Preliminary fluid nitrogen flow data are reported for a five-brush, ceramic-coated-rub-runner brush seal system, where the brushes and the rub runner were placed at each end of a centrally pressurized multifunction tester ('back-to-back' set of brushes) and tested at rotor speeds of 0, 10, 18, and 22.5 krpm. After testing, both the brushes and the ceramic-coated rub runner appeared pristine. The coating withstood both the thermomechanical and dynamic loadings with minor wear track scarring. The bristle tips showed some indication of material shearing (smearing) wear. The Ergun (1952) porous flow equation was applied to the brush seal data. The Ergun relation fit the gaseous data but was in poor agreement with the fluid results. The brush seal exit conditions were two phase. Two-phase, choked-flow design charts were applied but required one data point at each rotor speed to define the flow and area coefficients. Reasonable agreement between prediction and data was found, but such methods are not to be construed as two-phase-flow brush seal analyses.
Carlile, J. A.↗
Two-phase pressure drop of ammonia in small diameter horizontal tubes
Data for pressure drop in adiabatic two-phase ammonia flows in small diameter horizontal tubes are presented. The data has direct application to the sizing of the flow-through radiator tubes in the Space Station Freedom heat rejection system. The data are compared to existing correlations for pressure drop and are found to be significantly lower than the most commonly used correlations. However, several of the less commonly used correlations predict the data accurately. Alternate pressure drop prediction methods are explored and a recommendation is made for a method to accurately predict the pressure drop in two-phase ammonia flows in small horizontal tubes.
Ungar, Eugene K.↗
Nonhysteretic Capillary Pressure in Two‐Fluid Porous Medium Systems: Definition, Evaluation, Validation, and Dynamics
Abstract A closure relation for capillary pressure plays an important role in the formulation of both traditional and evolving models of two‐fluid‐phase flow in porous medium systems. We review the traditional approaches to define capillary pressure, to describe it mathematically, to determine parameters for this relation, and to constrain the domain of applicability of this relation. In contrast to the traditional approach, we provide a rigorous, multiscale definition of capillary pressure, define the state domain of interest in practice, summarize computational and experimental approaches to investigate the system state, and apply the methods for two‐fluid states in a model ink bottle system, the classical Finney pack of spheres, and a synthetic sphere pack system. The results of these applications show that a state equation exists that describes capillary pressure without hysteresis. This state equation parameterizes a function that describes the nonwetting phase volume fraction in terms of the capillary pressure, the interfacial area, and the specific Euler characteristic of the nonwetting phase. Furthermore, this state equation applies over the complete range of conditions encountered in practice, and it applies under both equilibrium and dynamic conditions. This state equation involving capillary pressure forms an important foundation for the development of the next generation of macroscale two‐fluid‐phase flow models in porous medium systems.
Miller, C. T.↗