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At least 1,477 records · Page 82
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Preliminary Results from Numerical Experiments on the Summer 1980 Heat Wave and Drought

During the summer of 1980, a prolonged heat wave and drought affected the United States. A preliminary set of experiments has been conducted to study the effect of varying boundary conditions on the GLA model simulation of the heat wave. Five 10-day numerical integrations with three different specifications of boundary conditions were carried out: a control experiment which utilized climatological boundary conditions, an SST experiment which utilized summer 1980 sea-surface temperatures in the North Pacific, but climatological values elsewhere, and a Soil Moisture experiment which utilized the values of Mintz-Serafini for the summer, 1980. The starting dates for the five forecasts were 11 June, 7 July, 21 July, 22 August, and 6 September of 1980. These dates were specifically chosen as days when a heat wave was already established in order to investigate the effect of soil moistures or North Pacific sea-surface temperatures on the model's ability to maintain the heat wave pattern. The experiments were evaluated in terms of the heat wave index for the South Plains, North Plains, Great Plains and the entire U.S. In addition a subjective comparison of map patterns has been performed.

Wolfson, N.↗
NASA NTRS1985

Heat transfer in aeropropulsion systems

Aeropropulsion heat transfer is reviewed. A research methodology based on a growing synergism between computations and experiments is examined. The aeropropulsion heat transfer arena is identified as high Reynolds number forced convection in a highly disturbed environment subject to strong gradients, body forces, abrupt geometry changes and high three dimensionality - all in an unsteady flow field. Numerous examples based on heat transfer to the aircraft gas turbine blade are presented to illustrate the types of heat transfer problems which are generic to aeropropulsion systems. The research focus of the near future in aeropropulsion heat transfer is projected.

Simoneau, R. J.↗
NASA NTRS1985

Local heat-transfer measurements on a large, scale-model turbine blade airfoil using a composite of a heater element and liquid crystals

Local heat transfer coefficients were experimentally mapped along the midchord of a five-time-size turbine blade airfoil in a static cascade operated at room temperature over a range of Reynolds numbers. The test surface consisted of a composite of commercially available materials: a mylar sheet with a layer of cholesteric liquid crystals, that change color with temperature, and a heater sheet made of a carbon-impregnated paper, that produces uniform heat flux. After the initial selection and calibration of the composite sheet, accurate, quantitative, and continuous heat transfer coefficients were mapped over the airfoil surface. The local heat transfer coefficients are presented for Reynolds numbers from 2.8 x 10 to the 5th power to 7.6 x 10 to the 5th power. Comparisons are made with analytical values of heat transfer coefficients obtained from the STAN5 boundary layer code. Also, a leading edge separation bubble was revealed by thermal and flow visualization.

Hippensteele, S. A.↗
NASA NTRS1985

Application of axisymmetric analogue for calculating heating in three-dimensional flows

A rapid, approximate method has been developed for calculating the heating rates on three-dimensional vehicles such as the Space Shuttle Orbiter and other advanced reentry configurations. The method is based on the axisymmetric analogue for three-dimensional boundary layers. It uses information obtained from a three-dimensional inviscid flowfield solution, such as HALIS, to calculate inviscid surface streamlines along which approximate heating rates are calculated independent of what happens along other streamlines. Three-dimensional effects are included through the metric coefficient that describes the divergence or convergence of streamlines. Boundary-layer edge properties are obtained from the inviscid flowfield solution by interpolating in the inviscid flowfield at a distance equal to the boundary-layer thickness away from the wall. This accounts, approximately, for the variable boundary-layer edge entropy. Using this method, heating calculations can be made along a typical streamline in a few seconds. This method has been used to accurately predict heating rates for simple shapes such as a spherically blunted cone and more complex shapes such as the Shuttle Orbiter for a variety of wind-tunnel and flight conditions. A unique feature of the method is its ability to accurately predict heating rates on the Shuttle Orbiter wing.

Hamilton, H. H.↗
NASA NTRS1984

Large scale surface heat fluxes

The heat flux through the ocean surface, Q, is the sum of the net radiation at the surface, the latent heat flux into the atmosphere, and the sensible heat flux into the atmosphere (all fluxes positive upwards). A review is presented of the geographical distribution of Q and its constituents, and the current accuracy of measuring Q by ground based measurements (both directly and by 'bulk formulae') is assessed. The relation of Q to changes of oceanic heat content, heat flux, and SST is examined and for each of these processes, the accuracy needed for Q is discussed. The needed accuracy for Q varies from process to process, varies geographically, and varies with the time and space scale considered.

Sarachik, E. S.↗
NASA NTRS1984

On the heating mechanism of magnetic flux loops in the solar atmosphere

An investigation is conducted of physical heating mechanisms due to the ponderomotive forces exerted by turbulent waves along the solar atmosphere's curved magnetic flux loops. Results indicate that the temperature difference between the inside and outside of the flux loop can be classified into three parts, two of which represent the cooling or heating effect exerted by the ponderomotive force, while the third is the heating effect due to turbulent energy conversion from the localized plasma. This heating mechanism is used to illustrate solar atmospheric heating by means of an example that leads to the formulation of plages.

Song, M. T.↗
NASA NTRS1985

Coronal heating by resonant (A.C.) and nonresonant (D.C.) mechanisms

The solar coronal heating studies of Ionson (1984) and Heyvaerts and Priest (1984) invoke categorically different mechanisms involving the generation of ac currents, in the case of resonant mechanisms, and dc currents, in the case of nonresonant ones. Attention is presently given to Heyvaerts and Priest's finding that dc heating mechanisms are represented by the m = 0 harmonic of Ionson's unified theory of coronal heating, which is here extended to include all excitation harmonics, including m = 0. The efficiency of dc mechanisms is severely limited by the constraint that the dissipation time be comparable to the correlation time of the convective driver and smaller than the magnetic flux leakage time, suggesting for the solar case that dc processes dominate heating in young, active region loops, while ac ones dominate heating in both active region and large scale loops.

Ionson, J. A.↗
NASA NTRS1985

Evidence for ion heat flux in the light ion polar wind

Cold flowing hydrogen and helium ions have been observed using the retarding ion mass spectrometer on board the Dynamics Explorer 1 spacecraft in the dayside magnetosphere at subauroral latitudes. The ions show a marked flux asymmetry with respect to the relative wind direction. The observed data are fitted by a model of drifting Maxwellian distributions perturbed by a first order-Spritzer-Haerm heat flux distribution function. It is shown that both ion species are supersonic just equatorward of the auroral zone at L = 14, and the shape of asymmetry and direction of the asymmetry are consistent with the presence of an upward heat flux. At L = 6, both species evolve smoothly into warmer subsonic upward flows with downward heat fluxes. In the case of subsonic flows the downward heat flux implies a significant heat source at higher altitudes. Spin curves of the spectrometer count rate versus the spin phase angle are provided.

Biddle, A. P.↗
NASA NTRS1986

Heat Pipe Precools and Reheats Dehumidified Air

Precooling and reheating by heat pipe reduces operating costs of air-conditioning. Warm air returned from air-conditioned space and cooled air supplied are precooled and reheated, respectively, by each other through a heat pipe. Heat-pipe technology brought to bear on problem of conserving airconditioning energy in hot, humid environments. Any increase in the cost of equipment due to installation of heat-pipe heat exchangers expected to be recovered in energy savings during service period of 2 years or less.

Koning, R. C.↗
NASA NTRS1983

Gas-side heat transfer with rotation

The primary basis for heat transfer analysis of turbine blades is experimental data obtained in linear cascades. These data have been very valuable in identifying the major heat transfer and fluid flow features of a turbine airfoil. The question of major interest is how well all of these data translate to the rotating turbine blade. It is known from the work of Lokay and Trushin that average heat transfer coefficients on the rotor may be as much as 40 percent above the values measured on the same blades nonrotating. Recent work by Dunn and Holt supports the Russian conclusion. What is lacking is a set of data from a rotating system which is of sufficient detail as to make careful local comparisons between static system in which there is sufficient documentation of the flow field to support the computer analyses being developed today. A second major question is the influence, if any, of the first stator row on the heat transfer of the second stator row after the flow has passed through the rotor. An objective of the present program, is to obtain a detailed set of heat transfer coefficients along the midspan of a blade in a rotating turbine.

Dring, R. P.↗
NASA NTRS1985

Heat transfer characteristics within an array of impinging jets. Effects of crossflow temperature relative to jet temperature

Spanwise average heat fluxes, resolved in the streamwise direction to one stream-wise hole spacing were measured for two-dimensional arrays of circular air jets impinging on a heat transfer surface parallel to the jet orifice plate. The jet flow, after impingement, was constrained to exit in a single direction along the channel formed by the jet orifice plate and heat transfer surface. The crossflow originated from the jets following impingement and an initial crossflow was present that approached the array through an upstream extension of the channel. The regional average heat fluxes are considered as a function of parameters associated with corresponding individual spanwise rows within the array. A linear superposition model was employed to formulate appropriate governing parameters for the individual row domain. The effects of flow history upstream of an individual row domain are also considered. The results are formulated in terms of individual spanwise row parameters. A corresponding set of streamwise resolved heat transfer characteristics formulated in terms of flow and geometric parameters characterizing the overall arrays is described.

Florschuetz, L. W.↗
NASA NTRS1985

The planetary distribution of heat sources and sinks during FGGE

Heating distributions from analysis of the National Meteorological Center and European Center for Medium Range Weather Forecasts data sets; methods used and problems involved in the inference of diabatic heating; the relationship between differential heating and energy transport; and recommendations on the inference of heat soruces and heat sinks for the planetary show are discussed.

Johnson, D. R.↗
NASA NTRS1985

Solar heated oil shale pyrolysis process

An improved system for recovery of a liquid hydrocarbon fuel from oil shale is presented. The oil shale pyrolysis system is composed of a retort reactor for receiving a bed of oil shale particules which are heated to pyrolyis temperature by means of a recycled solar heated gas stream. The gas stream is separated from the recovered shale oil and a portion of the gas stream is rapidly heated to pyrolysis temperature by passing it through an efficient solar heater. Steam, oxygen, air or other oxidizing gases can be injected into the recycle gas before or after the recycle gas is heated to pyrolysis temperature and thus raise the temperature before it enters the retort reactor. The use of solar thermal heat to preheat the recycle gas and optionally the steam before introducing it into the bed of shale, increases the yield of shale oil.

Qader, S. A.↗
NASA NTRS1985

Measurement of the heat produced internally during discharge by the 6V Eveready Energizer Battery, no. 528

When a 6V Eveready Energizer Battery, 528, is discharged, heat is produced internally within the battery itself. Detailed measurements of this battery heat were made for a five day discharge period using a load resistance of 20 ohms and an ambient temperature of 10 C. The battery heat produced per quarter day varied considerably, ranging from 1.08 watt-hrs to 2.63 watt-hrs. The total battery heat produced, using a 3.0 volt cutoff, is significant (37 watt-hrs) when compared to the total load heat produced (70 watt-hrs).

F. D. Hooker↗
NASA NTRS1985

Local heat-transfer measurements on a large scale-model turbine blade airfoil using a composite of a heater element and liquid crystals

Local heat transfer coefficients were experimentally mapped along the midchord of a five-time-size turbine blade airfoil in a static cascade operated at room temperature over a range of Reynolds numbers. The test surface consisted of a composite of commercially available materials: a mylar sheet with a layer of cholesteric liquid crystals, that change color with temperature, and a heater sheet made of a carbon-impregnated paper, that produces uniform heat flux. After the initial selection and calibration of the composite sheet, accurate, quantitative, and continuous heat transfer coefficients were mapped over the airfoil surface. The local heat transfer coefficients are presented for Reynolds numbers from 2.8 x 10 to the 5th power to 7.6 x 10 to the 5th power. Comparisons are made with analytical values of heat transfer coefficients obtained from the STANS boundary layer code. Also, a leading edge separation bubble was revealed by thermal and flow visualization.

Hippensteele, S. A.↗
NASA NTRS1986

Heat pipe radiator technology for space power systems

High-reliability high-performance deployable monogroove and dual-slot heat pipe radiator systems to meet the requirements for electric power in future space missions, such as the 300-kW(e) electric powder demand projected for NASA's Space Station, are discussed. Analytical model trade studies of various configurations show the advantages of the dual-slot heat pipe radiator for high temperature applications as well as its weight reduction potential over the 50-350 F temperature range. The ammonia-aluminum monogroove heat pipe, limited to below-180 F operating temperatures, is under development, and can employ methanol-stainless steel heat pipes to achieve operating temperatures in excess of 300 F. Dual-slot heat pipe configuration proof-of-concept testing was begun in 1985.

Carlson, A. W.↗
NASA NTRS1986

Calculation of convective heating on proposed aeroassist flight experiment vehicle

Convective heating calculations of a NASA aeroassist flight experiment (AFE) configuration consisting of a blunted, elliptic cone raked off at the base, and fitted with a skirt-type afterbody with a generous corner radius, are presented. The HALIS inviscid flowfield code is used to supply edge properties to an approximate three-dimensional boundary-layer method to calculate the surface heating. Calculations at Mach number 9.86 and approximate Reynolds number of 500,000, for angles of attack from -10 to 10 degrees, are in general good agreement with Langley 31-inch Mach 10 Tunnel experimental data. The results validate the application of the present overall AFE configuration heating pattern heating contours to aeroassist orbital transfer vehicle heating distribution determinations.

Hamilton, H. H., II↗
NASA NTRS1986

Experimental measurements of heat transfer from an iced surface during artificial and natural cloud icing conditions

The heat transfer behavior of accreting ice surfaces in natural (flight test) and simulated (wind tunnel) cloud icing conditions have been studied. Observations of wet and dry ice growth regimes as measured by ultrasonic pulse-echo techniques were made. Observed wet and dry ice growth regimes at the stagnation point of a cylinder were compared with those predicted using a quasi steady-state heat balance model. A series of heat transfer coefficients were employed by the model to infer the local heat transfer behavior of the actual ice surfaces. The heat transfer in the stagnation region was generally inferred to be higher in wind tunnel icing tests than in natural, flight, icing conditions.

Kirby, M. S.↗