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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Satellite temperature soundings: Microwave satellite observations

Tiros satellite microwave measurements together with radiosonde data are used to illustrate a method for deriving vertical temperature distributions in the atmosphere on the scale of 100 km. The method employs N equations in N unknowns. The unknowns are the N coefficients which are needed at each pressure level to multiply the measured N radiances in order to retrieve the vertical temperature distributions. As an example, the spatial variation of the tropopause characteristics is derived over a cyclone. Diurnal variations in the radiances and the consistency of radiosondes and satellite radiance data need further investigation.

Fritz, S.↗
NASA NTRS2014

Monitoring of Thermal Protection Systems and MMOD using Robust Self-Organizing Optical Fiber Sensing Networks

The general aim of this work is to develop and demonstrate a prototype structural health monitoring system for thermal protection systems that incorporates piezoelectric acoustic emission (AE) sensors to detect the occurrence and location of damaging impacts, such as those from Micrometeoroid Orbital Debris (MMOD). The approach uses an optical fiber Bragg grating (FBG) sensor network to evaluate the effect of detected damage on the thermal conductivity of the TPS material. Following detection of an impact, the TPS would be exposed to a heat source, possibly the sun, and the temperature distribution on the inner surface in the vicinity of the impact measured by the FBG network. A similar procedure could also be carried out as a screening test immediately prior to re-entry. The implications of any detected anomalies in the measured temperature distribution will be evaluated for their significance in relation to the performance of the TPS during reentry. Such a robust TPS health monitoring system would ensure overall crew safety throughout the mission, especially during reentry.

Fiber Optic Sensors↗
NASA NTRS2013

Monitoring of Thermal Protection Systems Using Robust Self-Organizing Optical Fiber Sensing Networks

The general aim of this work is to develop and demonstrate a prototype structural health monitoring system for thermal protection systems that incorporates piezoelectric acoustic emission (AE) sensors to detect the occurrence and location of damaging impacts, and an optical fiber Bragg grating (FBG) sensor network to evaluate the effect of detected damage on the thermal conductivity of the TPS material. Following detection of an impact, the TPS would be exposed to a heat source, possibly the sun, and the temperature distribution on the inner surface in the vicinity of the impact measured by the FBG network. A similar procedure could also be carried out as a screening test immediately prior to re-entry. The implications of any detected anomalies in the measured temperature distribution will be evaluated for their significance in relation to the performance of the TPS during re-entry. Such a robust TPS health monitoring system would ensure overall crew safety throughout the mission, especially during reentry

Structural Health Monitoring↗
NASA NTRS1977

Comparison of thermal analytic model with experimental test results for 30-sentimeter-diameter engineering model mercury ion thruster

A thermal analytic model for a 30-cm engineering model mercury-ion thruster was developed and calibrated using the experimental test results of tests of a pre-engineering model 30-cm thruster. A series of tests, performed later, simulated a wide range of thermal environments on an operating 30-cm engineering model thruster, which was instrumented to measure the temperature distribution within it. The modified analytic model is described and analytic and experimental results compared for various operating conditions. Based on the comparisons, it is concluded that the analytic model can be used as a preliminary design tool to predict thruster steady-state temperature distributions for stage and mission studies and to define the thermal interface bewteen the thruster and other elements of a spacecraft.

Oglebay, J. C.↗
NASA NTRS1979

Investigation of air stream from combustor-liner air entry holes, 3

Jets flowing from air entry holes of the combustor liner of a gas turbine were investigated. Cold air was supplied through the air entry holes into the primary hot gas flows. The mass flow of the primary hot gas and issuing jets was measured, and the behavior of the air jets was studied by the measurement of the temperature distribution of the gas mixture. The air jets flowing from three circular air entry holes, single streamwise long holes, and two opposing circular holes, parallel to the primary flow were studied along with the effects of jet and gas stream velocities, and of gas temperature. The discharge coefficient, the maximum penetration of the jets, the jet flow path, the mixing of the jets, and temperature distribution across the jets were investigated. Empirical expressions which describe the characteristics of the jets under the conditions of the experiments were formulated.

Aiba, T.↗
NASA NTRS1994

Formation, early evolution, and gravitational stability of protoplanetary disks

The formation, viscous evolution, and gravitational stability of protoplanetary disks are investigated. The formation process is parameterized by the angular velocity of the molecular cloud core omega, while the viscous evolution is parameterized by the viscosity parameter alpha in the disk; in this study we consider a range of (0.4-6) x 10(exp -14)/s for omega and from 10(exp -5) to 10(exp -1) for alpha. The axisymmetric gravitational stabilities of the disks are checked using Toomre's criterion. The resulting disk surface temperature distribution, (d log T(sub s)/d log R) approximately = -0.6 (R is the cylindrical radius), can be attributed to two heating sources: the viscous heating dominant in the inner disk region, and the accretion shock heating dominant in the outer disk region. This surface temperature distribution matches that observed in many disks around young stellar objects. During the infall stage, disks with alpha less than 10(exp -1.5) become gravitationally unstable independent of omega. The gravitational instabilities occur at radii ranging from 5 to 40 AU. The ratio of the disk mass to the central star mass ranges from 0.2 to 0.5 at the times of instability, about 4 x 10(exp -5) x (omega/10(exp -14)/s)(exp -0.67) yr. Most disks with low alpha and high omega become gravitationally unstable during their formation phase.

Nakamoto, Taishi↗
NASA NTRS1993

Variable Refractive Index Effects on Radiation in Semitransparent Scattering Multilayered Regions

A simple set of equations is derived for predicting the temperature distribution and radiative energy flow in a semitransparent layer consisting of an arbitrary number of laminated sublayers that absorb, emit, and scatter radiation. Each sublayer can have a different refractive index and optical thickness. The plane composite region is heated on each exterior side by a different amount of incident radiation. The results are for the limiting case where heat conduction within the layers is very small relative to radiative transfer, and is neglected. The interfaces are assumed diffuse, and all interface reflections are included in the analysis. The thermal behavior is readily calculated from the analytical expressions that are obtained. By using many sublayers, expressions provide the temperature distribution and heat flow for a diffusing medium with a continually varying refractive index, including internal reflection effects caused by refractive index gradients. Temperature and heat flux results are given to show the effect of variations in refractive index and optical thickness through the multilayer laminate.

Siegel, R.↗
NASA NTRS2009

Thermal-Structural Analysis of PICA Tiles for Solar Tower Test

Thermal protection materials used in spacecraft heatshields are subjected to severe thermal and mechanical loading environments during re-entry into earth atmosphere. In order to investigate the reliability of PICA tiles in the presence of high thermal gradients as well as mechanical loads, the authors designed and conducted solar-tower tests. This paper presents the design and analysis work for this tests series. Coupled non-linear thermal-mechanical finite element analyses was conducted to estimate in-depth temperature distribution and stress contours for various cases. The first set of analyses performed on isolated PICA tile showed that stresses generated during the tests were below the PICA allowable limit and should not lead to any catastrophic failure during the test. The tests results were consistent with analytical predictions. The temperature distribution and magnitude of the measured strains were also consistent with predicted values. The second test series is designed to test the arrayed PICA tiles with various gap-filler materials. A nonlinear contact method is used to model the complex geometry with various tiles. The analyses for these coupons predict the stress contours in PICA and inside gap fillers. Suitable mechanical loads for this architecture will be predicted, which can be applied during the test to exceed the allowable limits and demonstrate failure modes. Thermocouple and strain-gauge data obtained from the solar tower tests will be used for subsequent analyses and validation of FEM models.

Agrawal, Parul↗
NASA NTRS1993

Variable Refractive Index Effects on Radiation in Semitransparent Scattering Multilayered Regions

A simple set of equations is derived for predicting the temperature distribution and radiative energy flow in a semitransparent layer consisting of an arbitrary number of laminated sublayers that absorb, emit, and scatter radiation. Each sublayer can have a different refractive index and optical thickness. The plane composite region is heated on each exterior side by a different amount of incident radiation. The results are for the limiting case where heat conduction within the layers is very small relative to radiative transfer, and is neglected. The interfaces are assumed diffuse, and all interface reflections are included in the analysis. The thermal behavior is readily calculated from the analytical expressions that are obtained. By using many sublayers, the analytical expressions provide the temperature distribution and heat flow for a diffusing medium with a continuously varying refractive index, including internal reflection effects caused by refractive index gradients. Temperature and heat flux results are given to show the effect of variations in refractive index and optical thickness through the multilayer laminate.

Siegel, R.↗
NASA NTRS2006

Io: Loki Patera as a Magma Sea

We develop a physical model for Loki Patera as a magma sea. We calculate the total volume of magma moving through the Loki Patera volcanic system every resurfacing cycle (approx.540 days) and the resulting variation in thermal emission. The rate of magma solidification at times reaches 3 x 10(exp 6) kg per second, with a total solidified volume averaging 100 cu km per year. A simulation of gas physical chemistry evolution yields the crust porosity profile and the timescale when it will become dense enough to founder in a manner consistent with observations. The Loki Patera surface temperature distribution shows that different areas are at different life cycle stages. On a regional scale, however, there can be coordinated activity, indicated by the wave of thermal change which progresses from Loki Patera's SW quadrant toward the NE at a rate of approx.1 km per day. Using the observed surface temperature distribution, we test several mechanisms for resurfacing Loki Patera, finding that resurfacing with lava flows is not realistic. Only the crustal foundering process is consistent with observations. These tests also discovered that sinking crust has a 'heat deficit' which promotes the solidification of additional magma onto the sinking plate ("bulking up"). In the limiting case, the mass of sinking material can increase to a mass of approx.3 times that of the foundering plate. With all this solid matter sinking, there is a compensating upward motion in the liquid magma. This can be in excess of 2 m per year. In this manner, solid-liquid convection is occurring in the sea.

heat flow↗
NASA NTRS1953

An analysis of laminar free-convection flow and heat transfer about a flat plate paralled to the direction of the generating body force

The free-convection flow and heat transfer (generated by a body force) about a flat plate parallel to the direction of the body force are formally analyzed and the type of flow is found to be dependent on the Grashof number alone. For large Grashof numbers (which are of interest in aeronautics), the flow is of the boundary-layer type and the problem is reduced in a formal manner, which is analogous to Prandtl's forced-flow boundary-layer theory, to the simultaneous solution of two ordinary differential equations subject to the proper boundary conditions. Velocity and temperature distributions for Prandtl numbers of 0.01, 0.72, 0.733, 1, 1, 10, 100, and 1000 are computed, and it is shown that velocities and Nusselt numbers of the order of magnitude of those encountered in forced-convection flows may be obtained in free-convection flows. The theoretical and experimental velocity and temperature distributions are in good agreement. A flow and a heat-transfer parameter, from which the important physical quantities such as shear stress and heat-transfer rate can be computed, are derived as functions of Prandtl number alone.

Ostrach, Simon↗
NASA NTRS1989

Low-speed flowfield characterization by infrared measurements of surface temperatures

An experimental program was aimed at identifying areas in low speed aerodynamic research where infrared imaging systems can make significant contributions. Implementing a new technique, a long electrically heated wire was placed across a laminar jet. By measuring the temperature distribution along the wire with the IR imaging camera, the flow behavior was identified. Furthermore, using Nusselt number correlations, the velocity distribution could be deduced. The same approach was used to survey wakes behind cylinders in a wind-tunnel. This method is suited to investigate flows with position dependent velocities, e.g., boundary layers, confined flows, jets, wakes, and shear layers. It was found that the IR imaging camera cannot accurately track high gradient temperature fields. A correlation procedure was devised to account for this limitation. Other wind-tunnel experiments included tracking the development of the laminar boundary layer over a warmed flat plate by measuring the chordwise temperature distribution. This technique was applied also to the flow downstream from a rearward facing step. Finally, the IR imaging system was used to study boundary layer behavior over an airfoil at angles of attack from zero up to separation. The results were confirmed with tufts observable both visually and with the IR imaging camera.

Gartenberg, E.↗
NASA NTRS2006

Solar Sail Topology Variations Due to On-Orbit Thermal Effects

The objective of this research was to predict the influence of non-uniform temperature distribution on solar sail topology and the effect of such topology variations on sail performance (thrust, torque). Specifically considered were the thermal effects due to on orbit attitude control maneuvers. Such maneuvers are expected to advance the sail to a position off-normal to the sun by as much as 35 degrees; a solar sail initially deformed by typical pre-tension and solar pressure loads may suffer significant thermally induced strains due to the non-uniform heating caused by these maneuvers. This on-orbit scenario was investigated through development of an automated analytical shape model that iterates many times between sail shape and sail temperature distribution before converging on a final coupled thermal structural affected sail topology. This model utilizes a validated geometrically non-linear finite element model and a thermal radiation subroutine. It was discovered that temperature gradients were deterministic for the off-normal solar angle cases as were thermally induced strains. Performance effects were found to be moderately significant but not as large as initially suspected. A roll torque was detected, and the sail center of pressure shifted by a distance that may influence on-orbit sail control stability.

Banik, Jeremy A.↗
NASA NTRS1951

Analytical investigation of fully developed laminar flow in tubes with heat transfer with fluid properties variable along the radius

Relations were analytically obtained for the prediction of radial distributions of velocity and temperature for fully developed laminar flow of gases and of liquid metals in tubes with fluid properties variable along the radius. The relations are applicable to both heating and cooling of the fluid. By use of the relations for velocity and temperature distributions, relations were obtained among Nusselt number, friction parameter, and ratio of wall to bulk temperature. The Nusselt number and friction parameter were found to be independent of Reynolds number and Prandtl number. The effects of ratio of wall to bulk temperature on Nusselt number and friction parameter could be eliminated by evaluating the fluid properties at specified temperatures in the fluid.

Deissler, Robert G↗
NASA NTRS1992

Effect of Index of Refraction on Radiation Characteristics in a Heated Absorbing, Emitting, and Scattering Layer

The effect of the index of refraction on the temperature distribution and radiative heat flux in semitransparent materials, such as some ceramics, is investigated analytically. In the case considered here, a plane layer of a ceramic material is subjected to external radiative heating incident on each of its surfaces; the material emits, absorbs, and isotropically scatters radiation. It is shown that, for radiative equilibrium in a gray layer with diffuse interfaces, the temperature distribution and radiative heat flux for any index of refraction can be obtained in a simple manner from the results for an index of refraction of unity.

Siegel, R.↗
NASA NTRS1992

Effects of the cooling system parameters on heat transfer and performance of the PAFC stack during transient operation

An experimental investigation for the effects of transient operation of a phosphoric acid fuel-cell stack on heat transfer and temperature distribution in the electrodes has been conducted. The proposed work utilized the experimental setup with modifications, which was designed and constructed under NASA Contract No. NCC-3-17(5). The experimental results obtained from this investigation and the mathematical model obtained under NASA Contract No. NCC3-17(4) after modifications, were utilized to develop mathematical models for transient heat transfer coefficient and temperature distribution in the electrode and to evaluate the performance of the cooling - system under unsteady state conditions. The empirical formulas developed were then implemented to modifying the developed computer code. Two incompressible coolants were used to study experimentally the effect of the thermophysical properties of the cool-ants on the transient heat transfer coefficient and the thermal contact resistance during start-up and shut-down processes. Coolant mass flow rates were verified from 16 to 88.2 Kg/hr during the transient process when the electrical power supply was gradually increased or decreased in the range (O to 3000 W/sq m). The effect of the thermal contact resistance with a range of stack pressure from O to 3500 KPa was studied.

Ridha, Rabi M. J.↗
NASA NTRS1982

Flight measurements of tile gap heating on the Space Shuttle

Data are presented from Space Shuttle flight measurements of the temperature distribution within the gaps of the reusable surface insulation tiles. This is the first of a series of flight measurements in which the gap width and tile surface edge radius will be systematically varied. The data show several interesting features including the time and effect of boundary-layer transition. The local heating rates into the gap surfaces are calculated from the measured temperature distribution down the gap at two locations.

Pitts, W. C.↗