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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Laser probe for measuring 2-D wave slope spectra of ocean capillary waves

A laser-optical instrument for use in determining the two-dimensional wave-slope spectrum of ocean capillary waves is described. The instrument measures up to a 35-deg tip angle of the surface normal by measuring the position of a refracted laser beam directed vertically upward through a water surface. A telescope, a continuous two-dimensional Schottky barrier photodiode, and a pair of analog dividers render the signals independent of water height and insensitive to laser-beam intensity fluctuations. Calibration is performed entirely in the laboratory before field use. Sample records and wave-slope spectra are shown for one-dimensional wave-tank tests and for two-dimensional ocean tests. These are presented along with comparison spectra for calm and choppy water conditions. A mechanical wave follower was used to adjust the instrument position in the presence of large ocean swell and tides.

Palm, C. S.↗
NASA NTRS1980

An improved capillary rheometer

Capillary rheometer incorporates cone-tipped preheated piston to compress plastized coal sample through narrow tube. Applied force is proportional to viscosity and is recorded on separate instrument. Samples are heated rapidly due to large area of cone surface. Device, primarily applied in designing efficient equipment for feeding coal into combustion chamber, may be readily used in other viscosity studies.

Feinstein, S. P.↗
NASA NTRS1977

Application of an electron beam facility for heat transfer measurements in capillary tubes

A unique method was developed for the determination of heat transfer coefficients for water flowing through capillary tubes using a rastered electron beam heater. Heat flux levels of 150 and 500 watts/sq cm were provided on the top surface of four square tubes. Temperature gradient along the tube length and mass flow rates versus pressure drop were measured.

Lunde, A. R.↗
NASA NTRS1980

An investigation of the modulation of capillary and short gravity waves in the open ocean

A preliminary investigation of the modulation of capillary and gravity waves by long ocean waves is described. A pressure transducer is used to obtain water surface displacements, and a high-response laser-optical system is used to detect short-wave slopes. Analytical techniques are developed to account for the orbital motion of long waves. The local mean squared wave slope is found to be maximum leeward of the long-wave crests. For the long waves studied here and for short waves from 1 cm to 1 m, the longer a short-wave component is, the more leeward its maximum tends to occur. Also, the shortest waves tend to modulate least. The modulation of short waves is found to be strong enough to be an important component of the synthetic aperture radar image formation mechanism for long ocean waves.

Evans, D. D.↗
NASA NTRS1982

Development of and fabrication of high resolution gas chromatographic capillary columns

Gas chromatographic columns which are used in the trace gas analyzer (TGA) for the space shuttle are coated with a polyoxyethylene lauryl ether. This stationary phase is of medium polarity and has a temperature limit of 160 C. A polymer for this application which has an improved thermal stability is investigated. The use of fused silica capillary columns with specially bonded phases as well as an introduction system (on column) was also studied.

Zlatkis, A.↗
NASA NTRS1982

Capillary priming characteristics of a high capacity dual passage heat pipe

A parametric study of the forces governing the liquid-vapor interface was performed for the purpose of determining the capillary priming characteristics of Grumman's dual passage monogroove heat pipe when subjected to low-g or zero-g conditions. The static liquid-vapor interface configuration was determined through minimization of the free surface energies and a mathematical model and computer program which describe the time to prime was developed. Modeling predictions confirmed expectations of proper priming action and established the criteria for sizing of the liquid and vapor channels.

Peterson, G. P.↗
NASA NTRS1984

Design, development and test of a capillary pump loop heat pipe

The development of a capillary pump loop (CPL) heat pipe, including computer modeling and breadboard testing, is presented. The computer model is a SINDA-type thermal analyzer, combined with a pressure analyzer, which predicts the transients of the CPL heat pipe during operation. The breadboard is an aluminum/ammonia transport system which contains multiple parallel evaporator and condenser zones within a single loop. Test results have demonstrated the practicality and reliability of such a design, including heat load sharing among evaporators, liquid inventory/temperature control feature, and priming under load. Transport capability for this system is 65 KW-M with individual evaporator pumps managing up to 1.7 KW at a heat flux of 15 W/sq cm. The prediction of the computer model for heat transport capabilities is in good agreement with experimental results.

Kroliczek, E. J.↗
NASA NTRS1982

Capillary Pump Loop (CPL) heat pipe development status report

The capillary pump loop (CPL) was re-introduced as a potential candidate for the management of large heat loads. It is currently being evaluated for application in the thermal management of large space structures. Test efforts were conducted to establish the feasibility of the CPL heat pipe design.

Source record↗
NASA NTRS1985

Generation of capillary instabilities by external disturbances in a liquid jet

The receptivity problem in a circular liquid jet is considered. A time harmonic axial pressure gradient is imposed on the steady, parallel flow of a jet of liquid emerging from a circular duct. Using a technique developed in plasma physics a casual solution to the forced problem is obtained over certain ranges of Weber number for a number of mean velocity profiles. This solution contains a term which grows exponentially in the downstream direction and can be identified with a capillary instability wave. Hence, it is found that the externally imposed disturbances can indeed trigger instability waves in a liquid jet. The amplitude of the instability wave generated relative to the amplitude of the forcing is computed numerically for a number of cases.

Leib, S. J.↗
NASA NTRS1985

Thermal-capillary model for Czochralski growth of semiconductor materials

The success of efficiently calculating the temperature field, crystal radius, melt mensicus, and melt/solid interface in the Czochralski crystal growth system by full finite-element solution of the government thermal-capillary model is demonstrated. The model predicts realistic response to changes in pull rate, melt volume, and the thermal field. The experimentally observed phenomena of interface flipping, bumping, and the difficulty maintaining steady-state growth as the melt depth decreases are explained by model results. These calculations will form the basis for the first quantitative picture of Cz crystal growth. The accurate depiction of the melt meniscus is important in calculating the crystal radius and solidification interface. The sensitivity of the results to the equilibrium growth angle place doubt on less sophisticated attempts to model the process without inclusion of the meniscus. Quantitative comparison with experiments should be possible once more representation of the radiation and view factors in the thermal system and the crucible are included. Extensions of the model in these directions are underway.

Derby, J. J.↗
NASA NTRS1986

Functional and performance tests of two capillary pumped loop engineering models

This paper presents the results of the functional and performance tests for two capillary pumped loop (CPL) engineering models. Both CPL systems are aluminum/ammonia transport systems which contain eight parallel evaporators and six parallel condensers in a single loop. Tests conducted include the transport limit, heat load shearing between evaporators, liquid inventory/temperature control by the reservoir, pressure priming under heat load, diode function of condensers, and isolation of a single deprimed evaporator. Consistent performance results were obtained for both systems. Transport capabilities of up to 70 kw-m with individual evaporators managing up to 1.7 kw, with a corresponding input heat flux of 15w/sq cm, were demonstrated. These tests demonstrated the ability of a CPL system to operate over a wide range of conditions and thus established the viability of these systems for high power thermal management of large spacecraft, such as the NASA Space Station.

Ku, J.↗
NASA NTRS1986

Capillary pumped loop GAS and Hitchhiker flight experiments

Flight experiments of a capillary pumped loop (CPL) aboard the Space Shuttle on both the Get Away Special (GAS) and Hitchhiker-G (H/H-G) carriers are described. These tests have shown that a two-phase heat transfer loop utilizing a wicking material as the system pumping mechanism can operate successfully in a zero-g environment. The CPL operating modes demonstrated were start-up, heat load sharing/natural priming, liquid inventory and temperature control via the reservoir, dryout recovery, and isolation of a single pump deprime. Also investigated were high and low power limits, and inlet subcooling requirements. In these CPL flight experiments, successful system operation was demonstrated at input power levels up to 560 watts and inlet subcooling below 2 C.

Ku, J.↗
NASA NTRS1986

Thermal-capillary analysis of Czochralski and liquid encapsulated Czochralski crystal growth

Results are presented from finite element analysis of the Czochralski (CZ) and Liquid Encapsulated Czochralski (LEC) crystal growth processes based on a thermal-capillary model which governs the heat transfer in the system simultaneously with setting the shapes of the melt/solid interface, the melt and encapsulant menisci, and the radius of a steadily growing crystal. Calculations are performed for the small-scale growth of silicon (CZ) and gallium arsenide (LEC). The effects of melt volume and crucible position relative to the heater on the radius of the crystal and the shape of the melt/solid interface are predicted for the CZ system, and the importance of including an accurate representation of the melt meniscus for modeling the process is demonstrated. The additional effect of an encapsulant layer on heat transfer is treated for the LEC method for the cases of totally transparent and opaque encapsulant. The responses of these LEC prototype systems are examined for changes in pull rate and encapsulant volume.

Derby, J. J.↗
NASA NTRS1986

Thermal-capillary analysis of Czochralski and liquid encapsulated Czochralski crystal growth. II - Processing strategies

The pseudosteady-state heat transfer model developed in a previous paper is augmented with constraints for constant crystal radius and melt/solid interface deflection. Combinations of growth rate, and crucible and bottom-heater temperatures are tested as processing parameters for satisfying the constrained thermal-capillary problem over a range of melt volumes corresponding to the sequence occuring during the batchwise Czochralski growth of a small-diameter silicon crystal. The applicability of each processing strategy is judged by the range of existence of the solution, in terms of melt volume and the values of the axial and radial temperature gradients in the crystal.

Derby, J. J.↗
NASA NTRS1986

Thermal-capillary analysis of small-scale floating zones Steady-state calculations

Galerkin finite element analysis of a thermal-capillary model of the floating zone crystal growth process is used to predict the dependence of molten zone shape on operating conditions for the growth of small silicon boules. The model accounts for conduction-dominated heat transport in the melt, feed rod and growing crystal and for radiation between these phases, the ambient and a heater. Surface tension acting on the shape of the melt/gas meniscus counteracts gravity to set the shape of the molten zone. The maximum diameter of the growing crystal is set by the dewetting of the melt from the feed rod when the crystal radius is large. Calculations with small Bond number show the increased zone lengths possible for growth in a microgravity environment. The sensitivity of the method to the shape and intensity of the applied heating distribution is demonstrated. The calculations are compared with experimental observations.

Duranceau, J. L.↗
NASA NTRS1987

Investigation of thermal-fluid mechanical characteristics of the capillary pump and the pumped two-phase loop

This first semi-annual report summarized progress made on NASA Goddard Space Flight Center (GSFC) Grant NAG 5-834 during the period September 1, 1986 to February 28, 1987. The goal of the project is to gain a better understanding of the transient behavior of the Capillary Pump Loop (CPL) developed and tested by the GSFC. The investigation is directed toward development of analytical models to represent the transient thermal-fluid mechanic processes occurring in different parts of the CPL engineering model. Evaluation of the available test data has been the starting point for the investigation. Based on results of this evaluation, supplementary tests will be conducted by using a CPL test system already operational in the Heat Transfer laboratory of the university. Of particular interest is the oscillatory behavior of the CPL engineering model exhibited during some of the earlier test runs conducted at NASA-GSFC and Johnson Space Center (JSC).

Kiper, Ali M.↗
NASA NTRS1986

The generation of capillary instabilities on a liquid jet

The coupling between imposed disturbances and capillary instabilities on a liquid jet is examined. It is shown that in most physical situations the forcing produces neutral waves, which can then turn into growing waves as the profile relaxes or may be amplified nonlinearly by a mechanism of the type considered by Akylas and Benney (1980). The effectiveness of the coupling is expressed quantitatively by numerically computed values of the 'coupling coefficient'.

Leib, S. J.↗
NASA NTRS1987

Verification of an analytic modeler for capillary pump loop thermal control systems

A number of computer programs have been written to model two-phase heat transfer systems for space use. These programs support the design of thermal control systems and provide a method of predicting their performance in the wide range of thermal environments of space. Predicting the performance of one such system known as the capillary pump loop (CPL) is the intent of the CPL Modeler. By modeling two developed CPL systems and comparing the results with actual test data, the CPL Modeler has proven useful in simulating CPL operation. Results of the modeling effort are discussed, together with plans for refinements to the modeler.

Schweickart, R. B.↗