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Results for “Porous Screen”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Investigation of an inverted meniscus heat pipe wick concept

A wicking concept is described for efficient evaporation of heat pipe working fluids under diverse conditions. It embodies the high heat transfer coefficient of the circumferential groove while retaining the circumferential fluid transport capability of a thick porous wick or screen. Experimental tests are described which substantiate the efficacy of the evaporation technique for a circumferentially-grooved heat pipe charged alternately with ammonia and R-ll (CCl3F). With ammonia, heat transfer coefficients in the range of 2 to 2.7 W/sq cm K were measured at heat flux densities up to 20 W/sq cm while, with R-ll, a heat transfer coefficient of l.0 W/sq cm K was measured with flux densities up to 5 W/sq cm. Heat transfer coefficients and flux densities were unusually high compared to literature data for other nonboiling evaporative surfaces.

Saaski, E. W.↗
NASA NTRS1982

Turbulent boundary layer over solid and porous surfaces with small roughness

Skin friction and profiles of mean velocity, axial and normal turbulence intensity, and Reynolds stress in the untripped boundary layer were measured directly on a large diameter, axisymmetric body with: (1) a smooth, solid surface; (2) a sandpaper-roughened, solid surface; (3) a sintered metal, porous surface; (4) a smooth, perforated titanium surface; (5) a rough solid surface made of fine, diffusion bonded screening, and (6) a rough, porous surface of the same screening. Results obtained for each of these surfaces are discussed. It is shown that a rough, porous wall simply does not influence the boundary layer in the same way as a rough solid wall. Therefore, turbulent transport models for boundary layers over porous surfaces either with or without injection or suction, must include both surface roughness and porosity effects.

Kong, F. Y.↗
NASA NTRS1982

Turbulent boundary layer over solid and porous surfaces with small roughness

The wind tunnel models and instrumentation used as well as data reduction and error analysis techniques employed are described for an experimental study conducted to measure directly skin friction and obtain profiles of mean velocity, axial and normal turbulence intensity, and Reynolds stress in the untripped boundary on a large diameter axisymmetric body. Results are given for such a body with a (1) smooth, solid surface; (2) a sandpaper roughened, solid surface; (3) a sintered metal, porous surface; (4) a ""smooth'' performated titanium surface; (5) a rough, solid surface made of fine diffusion bonded screening; and (6) a rough, porous surface made of the same screening. The roughness values were in low range (k+ 5 to 7) just above what is normally considered ""hydraulically smooth''. Measurements were taken at several axial locations and tow or normal stream freestream velocities, 45.1 m/sec and 53.5 m/sec.

Kong, F. Y.↗
NASA NTRS1981

An experimental investigation of a large delta P settling chamber for a supersonic pilot quiet tunnel

The mean streamwise flow distributions and turbulence levels across the chamber were measured with a hot wire anemometer downstream of a series of porous Rigimesh plates which were shown to be an effective means of reducing the chamber acoustic disturbance levels due to upstream pipe and valve systems. Tests made with various types of flow conditioners downstream of the porous plates showed that a series of screens was the most effective means of achieving the objective of a uniform mean flow distribution with reduced vorticity levels downstream of the porous components. Frequency spectra obtained across the series of screens show that they reduce vorticity over a wide frequency range for several different initial upstream vorticity conditions. Improvements in the mechanical installation of the porous plates and damping screens and the use of porous plates with more uniform porosity should reduce the freestream velocity fluctuations to the minimum acoustic levels of about 0.5 percent.

Piatt, M.↗
NASA NTRS1977

Development of a prototype regenerable carbon dioxide absorber for portable life support systems

The design and development of a prototype carbon dioxide absorber using potassium carbonate (K2CO3) is described. Absorbers are constructed of thin, porous sheets of supported K2CO3 that are spirally wound to form a cylindrical reactor. Axial gas passages are formed between the porous sheets by corrugated screen material. Carbon dioxide and water in an enclosed life support system atmosphere react with potassium carbonate to form potassium bicarbonate. The potassium carbonate is regenerated by heating the potassium bicarbonate to 150 C at ambient pressure. The extravehicular mission design conditions are for one man for 8 h. Results are shown for a subunit test module investigating the effects of heat release, length-to-diameter ratio, and active cooling upon performance. The most important effect upon carbon dioxide removal is the temperature of the potassium carbonate.

Onischak, M.↗
NASA NTRS1991

Capillary-Effect Root-Environment System

Capillary-effect root-environment system (CERES) is experimental apparatus for growing plants in nutrient solutions. Solution circulated at slight tension in cavity filled with plastic screen and covered by porous plastic membrane. By adsorptive attraction, root draws solution through membrane. Conceived for use in microgravity of space, also finds terrestrial application in germinating seedlings, because it protects them from extremes of temperature, moisture, and soil pH and from overexposure to fertilizers and herbicides.

Wright, Bruce D.↗
NASA NTRS2014

Analytical Model for Steady Flow through a Finite Channel with One Porous Wall with Arbitrary Variable Suction or Injection

This paper presents an exact solution of two-dimensional laminar flow through a finite length channel with one porous wall. It improves upon previous solutions by (1) satisfying the no-slip boundary condition at the channel dead end, (2) adding a turbulent term to the porous wall boundary condition, (3) allowing for arbitrary variable suction or injection across the porous wall, and (4) model validation against new cryogenic liquid hydrogen and oxygen experimental data. Of particular interest in the current work is the modeling of cryogenic propellant flow through a porous liquid acquisition device (LAD) screen and channel inside a propellant tank. First, a detailed review of the literature is presented for previously attempted solutions to channel flow with one porous wall. Next, the governing equations, boundary conditions, and model assumptions are used to derive the analytical flow solution and present general model results for pressure and velocity fields within the channel. Then, the model solution is compared with horizontal LAD channel flow data in liquid oxygen as well as vertical LAD channel flow data in an inverted outflow configuration in liquid hydrogen. Model results are used to update the static cryogenic bubble point pressure model with a dynamic bubble point term which factors in enhanced convection and cooling at the screen during propellant outflow. Convective heat transfer at the LAD screen during outflow is also quantified by comparing model and data. The new analytical flow solution with the dynamic bubble point model is shown to compare well with available cryogenic experimental data

Navier Stokes Equations↗
NASA NTRSDate not supplied

Experimental and CFD Investigation of the Titled Jet Behavior in the Zero Boil-Off Tank (ZBOT) Experiment

Screens are used in cryogenic storage tanks to diffuse the incoming gas or liquid injection/flow into the tank. Meshed screens were also used in the jet mixing pressure control tests of the Zero Boil-Off Tank (ZBOT) Experiment which was recently performed aboard the International Space Station (ISS). The ZBOT pressure control studies used a liquid jet that was intended to be aligned with the longitudinal axis of the tank. A cartridge consisting of a honeycomb flow straightener and two screen diffusers, one upstream of the honeycomb, and one downstream, were designed to obtain the desired velocity profile in a manner that would be consistent in all the tests and could also be used as an input to the CFD simulations. Unfortunately, during the flight operations, the Digital Particle Image Velocimetry (DPIV) measurements indicated that the jet actually exited the nozzle at an angle to the main axis. This unexpected tilt affected the motion and deformation of the ullage during the pressure control tests, influencing the initial pressure drops. Upon disassembling the experiment hardware, it was discovered that the screen diffuser upstream of the honeycomb was clogged with debris. Since this behavior is important, not only to the follow-on ZBOT-NC experiment, but also to the operation of cryogenics storage tanks in general, a series of ground-based experiments and parametric CFD model simulations were performed to understand and characterize the tilted flow in terms of the clogged area of the upstream screen and the jet velocity. The experimental and CFD results surprisingly and non-intuitively showed that although the modification of the flow originated from the clogging of the upstream screen, the presence of the downstream unclogged screen was also necessary to produce the tilted jet. Two different CFD models were used for the numerical simulations, and only the one using a porous media formulation to capture the screen pressure drop was able to produce the correct tilting behavior. Parametric runs with the porous media CFD model were used to characterize the jet tilt in terms of the blockage area and jet velocity for both the future ZBOT-NC Experiment and other propellant tank applications. Supported by NASA Biological & Physical Sciences (BPS) Division, Physical Sciences Research Program, NASA HQ, USA.

Cryogenic Fluid Management↗
DOE OSTI2023

Identifying High-Performance Metal–Organic Frameworks for Low-Temperature Oxygen Recovery from Helium by Computational Screening

Metal–organic frameworks (MOFs) are an important class of porous crystalline materials for applications ranging from gas adsorption and separation to catalysis. There are thousands of potential MOFs available for separation applications. Here, we developed a computational approach to screen MOFs for the separation of oxygen–helium mixtures at low temperatures (100–200 K), conditions that were motivated by issues associated with propulsion in space-based settings. We used detailed molecular simulations for a small number of MOFs to develop screening methods that were then used to estimate the optimum temperatures for separations using pressure swing adsorption for 2932 MOFs from the CoRE MOF database and the swing capacity and oxygen–helium selectivity at these temperatures. We used the stability of the best-performing structures in the presence of moisture as a means to provide a short list of high-performance materials. In addition to identifying specific materials for oxygen–helium separations, this approach could prove useful for selecting adsorbents for other gas separations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1971

Oxidation-resistant silicide coating applied to columbium alloy screen

Coated screens withstand temperature cycling in special transpiration-cooling systems and provide porous surface that is effective at temperatures well above those limiting superalloy screen efficiency. Thickness of coating depends on time, temperature and activator concentration. Coatings are uniform and resistant to thermal cycling.

Torgerson, R. T.↗
NASA NTRS2004

Direct Measurements of Eddy Transport and Thermal Dispersion in a High Porosity Matrix

Thermal losses from the hot end to the cold end of a Stirling cycle regenerator due to thermal dispersion through the regenerator matrix may significantly degrade the performance of the machine. Because of poor access to the void spaces within the porous medium, no direct measurements of thermal dispersion have been made and dispersion models have been derived indirectly. This is done by measuring the overall thermal performance of the regenerator and subtracting off the energy transfer caused by molecular conduction and advected enthalpy flows computed from volume-averaged fluid velocity and temperature. In the current program, a large-scale porous matrix consisting of stacked wire screens with a porosity of 90% is installed in a flow rig which is operated in a Reynolds number range that represents Stirling engine regenerator flow. Experiments are conducted to measure turbulent transport of momentum at the exit phase using hot-wires. The relationship of such turbulent transport terms to the thermal dispersion term in the volumetric-averaged energy equation for the regenerator matrix is developed and the measurements are used to determine cross-stream thermal dispersion. A dispersion model based upon the measurements is proposed and compared with models documented in the literature.

Niu, Yi↗
NASA NTRS1992

Oscillating-flow regenerator test rig: Woven screen and metal felt results

We present correlating expressions, in terms of Reynolds or Peclet numbers, for friction factors, Nusselt numbers, enhanced axial conduction ratios, and overall heat flux ratios in four porous regenerator samples representative of stirling cycle regenerators: two woven screen samples and two random wire samples. Error estimates and comparison of data with others suggest our correlations are reliable, but we need to test more samples over a range of porosities before our results will become generally useful.

Gedeon, D.↗
NASA NTRS1978

Quiet wind tunnel

Simple and inexpensive technique suppresses background noise generated by pores in wind tunnel wall lining and makes aerodynamic data more accurate and reliable. Porous walls are covered with wire-mesh screen. Screen offers smoother surface to airflow and damps vortexes and resonance caused by wall perforations; yet it provides enough open area for perforations to cancel shock waves generated by model.

Howard, P. W.↗
NASA NTRS1988

Integrated fountain effect pump device for fluid management at low gravity

A new device for fluid management at low gravity is described. The system is basically the same as the enclosed capillary device using screens, in which the screens along the gallery channels are replaced by porous plugs which are responsible for both the fluid retention and pumping of He II; in this device, no downstream pump is needed. The plugs in contact with liquid He on both sides act as a fountain-effect pumps (FEPs), while plugs exposed to vapor on one side behave as vapor-liquid phase separators (VLPSs). The total net rate of He II transfer into the receiving tank equals the mass flow rate through the FEP plugs minus the liquid loss from the VLPS plugs. The results of the performance analysis of this integrated FEP device are presented together with its schematic diagram.

Yuan, S. W. K.↗
NASA NTRS1985

A new approach to flow problems past a screen

A new method to simulate flows past a two-dimensional porous plate is proposed. The method is a simple application of a discrete vortex method which has been well established for flows past an inclined flat plate. In this method, a flow past a porous plate is described as superposition of the velocity potential of a uniform flow on that of a flow past a flat plate. The effect of porosity is replaced by that of a mass flow rate of the approaching freestream passing through the plate. Calculated flow features are compared with experiments. It is shown that the present method is effective in the simulation of the flow past a porous plate.

Inoue, O.↗
DOE OSTI2022

Quantifying the anion effect of gas solubility within ionic liquids using the solvation affinity index

The solubility of gas molecules within ionic liquids (ILs) is strongly dictated by the anion effect and the free volume effect, and of these two influences, the anion effect can be challenging to predict. We evaluate a wide range of different gas solutes (O 2 , NH 3 , CH 4 , H 2 S, SO 2 , Ar, H 2 , N 2 , CO 2 ) in different ILs, and we find that the solubility is strongly correlated to one of three different IL properties, which can be directly calculated from the anion electrostatic potential (ESP) surfaces. Thus, the solutes can be grouped into three fundamental types, leading to a general descriptor, the solvation affinity index (SAI), which can identify the affinity between a wide range of gas solutes and IL solvents. The SAI of nine common industrial gases with 47 common anions are generated. Furthermore, this can provide a fast approach for pre-screening IL solvents or even for ILs embedded within porous supports.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1999

High Reynolds Number Hybrid Laminar Flow Control (HLFC) Flight Experiment: Suction System Design and Manufacture - Report 4

This document describes the design of the leading edge suction system for flight demonstration of hybrid laminar flow control on the Boeing 757 airplane. The exterior pressures on the wing surface and the required suction quantity and distribution were determined in previous work. A system consisting of porous skin, sub-surface spanwise passages ("flutes"), pressure regulating screens and valves, collection fittings, ducts and a turbocompressor was defined to provide the required suction flow. Provisions were also made for flexible control of suction distribution and quantity for HLFC research purposes. Analysis methods for determining pressure drops and flow for transpiration heating for thermal anti-icing are defined. The control scheme used to observe and modulate suction distribution in flight is described.

Source record↗