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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Estimating monthly averaged air-sea transfers of heat and momentum using the bulk aerodynamic method

Air-sea transfers of sensible heat, latent heat and momentum are computed from 25 years of middle-latitude and subtropical ocean weather ship data in the North Atlantic and North Pacific using the bulk aerodynamic method. The results show that monthly averaged wind speeds, temperatures and humidities can be used to estimate the monthly averaged sensible and latent heat fluxes from the bulk aerodynamic equations to within a relative error of approximately 10%. The estimates of monthly averaged wind stress under the assumption of neutral stability are shown to be within approximately 5% of the monthly averaged nonneutral values.

Esbensen, S. K.↗
NASA NTRS1982

Comparison of advanced thermal and electrical storage for parabolic dish solar thermal power systems

Parabolic dish solar concentrator cluster concepts are explored, with attention given to thermal storage systems coupled to Stirling and Brayton cycle power conversion devices. Sensible heat storage involving molten salt (NaOH), liquid sodium, and solid cordierite bricks are considered for 1500 F thermal storage systems. Latent heat storage with NaF-MgF2 phase change materials are explored in terms of passive, active, and direct contact designs. Comparisons are made of the effectiveness of thermal storage relative to redox, Na-S, Zn-Cl, and Zn-Br battery storage systems. Molten lead trickling down through a phase change eutectic, the NaF-MgF2, formed the direct contact system. Heat transport in all systems is effected through Inconel pipes. Using a cost goal of 120-150 mills/kWh as the controlling parameter, sensible heat systems with molten salts transport with either Stirling or Brayton engines, or latent heat systems with Stirling engines, and latent heat-Brayton engine with direct contact were favored in the analyses. Battery storage systems, however, offered the most flexibility of applications.

Fujita, T.↗
NASA NTRS1984

Ocean fluxes simulated by the GLAS GCM

A two year run with the GLAS climate model with prescribed but seasonally varying boundary conditions provided mean monthly fluxes of sensible heat, latent heat, and radiative energy. These fluxes were analyzed to examine the energy exchange processes between the atmosphere and the ice-free ocean. A mean annual plot of monthly zonal fuxes of sensible heat, latent heat, and net radiation was produced. From these, northward transport of heat flux that would follow if the GCM simulated fluxes were consistent with oceanic circulation were produced. These results are compared with observations.

Sud, Y. C.↗
NASA NTRS1984

An Investigation of the Marine Boundary Layer During Cold Air Outbreak

Various aspects of the marine atmospheric boundary layer (MABL) during cold air outbreak using data from the Mesoscale Air Sea Interaction Experiment (MASEX) and using a model for the MABL developed by Stage and Businger (1981,b) were studied. Several areas were identified for emphasis in this project: (1) determination of the momentum budget and divergence of the MABL; (2) development and testing of techniques for the remote determination of ocean surface sensible and latent heat fluxes by use of satellite data; (3) use of MASEX data to evaluate various techniques for parameterizing layer turbulence, to determine the typical magnitudes of such parameters and to improve the MABL model; and (4) use of the resulting MABL model and understanding of layer parameters to develop and evaluate more sophisticated schemes for remotely sensing layer evolution and sea surface sensible and latent heat fluxes.

Stage, S. A.↗
NASA NTRS1984

Observational-numerical Study of Maritime Extratropical Cyclones Using FGGE Data

The accomplishments, current research, and future plans of a study investigating the development, maturation, and decay of maritime extratropical cyclones are reported. Three cases of explosive cyclogenesis during the first GARP global experiment (FGGE) DOP-1 were studied diagnostically using storm-following budgets derived from the ECMWF and GLAS level III-b analyses. Mass, vorticity and angular momentum budgets for the moving storm environment were computed for each case. Key results from these studies include: (1) demonstration that the FGGE analyses can be used to explore oceanic circulations; (2) isolation of the role of upper level jet streaks in the initiation of the explosive period in all three cases; and (3) illustration of the lower tropospheric destabilization during each rapid deepening period, which is primarily due to sensible heating of the cold air by the warmer ocean surface. The physics package of the Navy global forecast model was successfully utilized in a semi-prognostic mode to estimate diabatic components of oceanic cyclone systems. Fields of sensible and latent heat fluxes, radiational heating and inferred cloud structures were also computed.

Wash, C. H.↗
NASA NTRS1985

The effect of water temperature and synoptic winds on the development of surface flows over narrow, elongated water bodies

Simulations of the thermally induced breeze involved with a relatively narrow, elongated water body is presented in conjunction with evaluations of sensible heat fluxes in a stable marine atmospheric surface layer. The effect of the water surface temperature and of the large-scale synoptic winds on the development of surface flows over the water is examined. As implied by the sensible heat flux patterns, the simulation results reveal the following trends: (1) when the synoptic flow is absent or light, the induced surface breeze is not affected noticeably by a reduction of the water surface temperature; and (2) for stronger synoptic flow, the resultant surface flow may be significantly affected by the water surface temperature.

Segal, M.↗
NASA NTRS1985

Mesoscale generation of available potential energy in the warm sector of an extratropical cyclone

The generation of available potential energy (APE) was evaluated in the warm sector of an extratropical cyclone containing intense convective activity. Mesoscale rawinsonde data from AVE-SESAME '79 was employed. Parametrization techniques were used for latent and sensible heating components, and variations for the Kuo scheme provided convective latent heat release. Radiative transfer models were used to obtain estimates of infrared and solar processes. The results indicated that solar heating was greater than IR cooling near midday. An extensive low-level cloud deck was the most radiatively active area. Negative generation of APE occurred during most of the period for the SESAME domain as a whole. The leading contributor was convective latent heating located primarily in regions of negative efficiency. Infrared cooling was the only component to consistently produce positive generation. Sensible heating provided an important sink of APE in the low levels during the afternoon.

Fuelberg, H. E.↗
NASA NTRS1987

A GCM study on the maintenance of the June 1982 blocking in the Southern Hemisphere

GCM experiments are used to study several possible mechanisms associated with the maintenance of the June 1982 blocking in the Southern Hemisphere. The mechanisms considered include changed orography, sea surface temperature anomalies, tropical heating, regional heating in the Pacific area, land-sea contrast, and sensible heating in the Antarctic area. It is concluded that asymmetric heating due to land-sea contrast was the most important boundary forcing associated with maintenance of the block. A 'no Australia' experiment confirms this result and suggests that local land-sea contrast kept the block stationary. High-latitude sensible heating associated with cold air outbreaks from Antarctica was also important in maintaining the block.

Mo, Kingtse C.↗
NASA NTRS1987

Dynamic aspects of the Southern-Hemisphere medium-scale waves during the southern summer season

The role of medium-scale waves on three dynamic aspects of the Southern-Hemisphere general circulation is examined using data generated by the FGGE analyses of the ECMWF. The momentum and sensible heat transports by the medium-scale waves are discussed. The effects of medium-scale waves on atmospheric circulation of the Southern Hemisphere during the summer, in particular the vacillation of atmospheric energetics, are investigated. The horizontal and vertical structures and the transport properties of this wave regime and their relation to downstream development in the Southern Hemisphere are analyzed. It is observed that medium-scale waves supply about a half of the total eddy transport of sensible heat and momentum; the wave regime contributes to the time average of various energy contents and energetic components of atmospheric motion during the southern summer; and the wave regime is amplified during the developing stages of downstream development.

Chen, Tsing-Chang↗
NASA NTRS1987

Transient radiative cooling of a layer filled with solidifying drops

An analysis is carried out for radiative cooling of a plane layer initially filled with liquid drops that solidify and then continue to cool by loss of sensible heat. This is in connection with a proposed lightweight radiator system for heat dissipation in space. Hot liquid drops would be ejected and then cooled by direct exposure in space; they would then pass into a collector for reuse. The cooling analysis contains three transient zones. In the first, the drops cool by losing latent heat until the outermost drops become solid. Then the cooling continues by loss of both latent and sensible heat. A similarity behavior is eventually achieved in which the transient emittance of the layer depends only on the optical thickness.

Siegel, R.↗
NASA NTRS1988

Comparison of measured and modeled radiation, heat and water vapor fluxes: FIFE pilot study

The primary objectives of the 1985 study were to test the feasibility of using radio frequency receivers to collect data from automated weather stations and to evaluate the use of the data collected by the automated weather stations for modeling the fluxes of latent heat, sensible heat, and radiation over wheat. The model Cupid was used to calculate these fluxes which were compared with fluxes of these entities measured using micrometeorological techniques. The primary objectives of the 1986 study were to measure and model reflected and emitted radiation streams at a few locations within the First International Satellite Land-Surface Climatology Project Field Experiment (FIFE) site and to compare modeled and measured latent heat and sensible heat fluxes from the prairie vegetation.

Blad, Blaine L.↗
NASA NTRS1989

Implementing the Simple Biosphere Model (SiB) in a general circulation model: Methodologies and results

The Simple Biosphere MOdel (SiB) of Sellers et al., (1986) was designed to simulate the interactions between the Earth's land surface and the atmosphere by treating the vegetation explicitly and relistically, thereby incorporating biophysical controls on the exchanges of radiation, momentum, sensible and latent heat between the two systems. The steps taken to implement SiB in a modified version of the National Meteorological Center's spectral GCM are described. The coupled model (SiB-GCM) was used with a conventional hydrological model (Ctl-GCM) to produce summer and winter simulations. The same GCM was used with a conventional hydrological model (Ctl-GCM) to produce comparable 'control' summer and winter variations. It was found that SiB-GCM produced a more realistic partitioning of energy at the land surface than Ctl-GCM. Generally, SiB-GCM produced more sensible heat flux and less latent heat flux over vegetated land than did Ctl-GCM and this resulted in the development of a much deeper daytime planetary boundary and reduced precipitation rates over the continents in SiB-GCM. In the summer simulation, the 200 mb jet stream and the wind speed at 850 mb were slightly weakened in the SiB-GCM relative to the Ctl-GCM results and equivalent analyses from observations.

Sato, N.↗
NASA NTRS1989

Effects of implementing the Simple Biosphere Model in a general circulation model

The Simple Biosphere Model (SiB) of Sellers et al., was designed to simulate the interactions between the earth's land surface and the atmosphere by treating the vegetation explicitly and realistically, thereby incorporating the biophysical controls on the exchanges of radiation, momentum, sensible and latent heat between the two systems. This paper describes the steps taken to implement SiB in a modified version of the National Meteorological Center's global spectral general circulation model (GCM) and explores the impact of the implementation on the simulated land surface fluxes and near-surface meteorological conditions. The coupled model (SiB-GCM) was used to produce summer and winter simulations. The same GCM was used with a conventional hydrological model (Ctl-GCM) to produce comparable 'control' summer and winter simulations for comparison. It was found that SiB-GCM produced a more realistic partitioning of energy at the land surface than Ctl-GCM. Generally, SiB-GCM, produced more sensible heat flux and less latent heat flux over vegetated land than did Ctl-GCM and this resulted in a much deeper daytime planetary boundary layer and reduced precipitation rates over the continents in SiB-GCM. In the summer simulation, the 200 mb jet stream was slightly weakened in the SiB-GCM relative to the Ctl-GCM results and analyses made from observations.

Sato, N.↗
NASA NTRS1989

Solidification by radiative cooling of a cylindrical region filled with drops

Transient cooling by radiation is analyzed for a cylindrical region filled with axially flowing streams of drops that are becoming solidified. This is of interest for the dissipation of waste heat from orbiting power system in space. The drops absorb, emit, and scatter radiation, and the surroundings are at a lower uniform temperature. The radiative properties are assumed gray, and the scattering is isotropic. The radiating region is a two-phase mixture that remains at the melting temperature of the drops. Its temperature uniformity maintains a high emissive power as energy is lost. This is an advantage over a sensible heat radiator in which the temperature decreases, thereby reducing the emissive power. The results provide the axial length that remains two-phase and the fraction of energy dissipated within this length in which the emissive power has not decreased because of sensible cooling. It is also shown how the radial distribution of the axial velocity of the drops can be modified to increase this energy fraction.

Siegel, Robert↗
NASA NTRS1990

Free convection in the Matian atmosphere

The 'free convective' regime for the Martian atmospheric boundary layer (ABL) was investigated. This state occurs when the mean windspeed at the top of the ABL drops below some critical value U(sub c) and positive buoyant forces are present. Such forces can arise either from vertical temperature or water vapor gradients across the atmospheric surface layer. During free convection, buoyant forces drive narrow plumes that ascend to the inversion height with a return circulation consisting of broad slower-moving downdraughts. Horizontal pressure, temperature, windspeed, and water vapor fluctuations resulting form this circulation pattern can be quite large adjacent to the ground (within the surface layer). The local turbulent fluctuations cause non-zero mean surface stresses, sensible heat fluxes, and latent heat fluxes, even when the mean regional windspeed is zero. Although motions above the surface layer are insensitive to the nature of the surface, the sensible and latent heat fluxes are primarily controlled by processes within the interfacial sublayer immediately adjacent to the ground during free convection. Thus the distinction between aerodynamically smooth and rough airflow within the interfacial sublayer is more important than for the more typical situation where the mean regional windspeed is greater than U(sub c). Buoyant forces associated with water vapor gradients are particularly large on Mars at low pressures and high temperatures when the surface relative humidity is 100 percent, enhancing the likelihood of free convection under these conditions. On this basis, Ingersol postulated the evaporative heat losses from an icy surface on Mars at 237 K and current pressures would exceed the available net radiative flux at the surface, thus prohibiting ice from melting at low atmospheric pressures. Schumann has developed equations describing the horizontal fluctuations and mean vertical gradients occurring during free convection. Schumann's model was generalized to include convection driven by water vapor gradients and to include the effects of circulation above both aerodynamically smooth and rough surfaces.

Clow, G. D.↗
NASA NTRS1991

The AE-8 trapped electron model environment

The machine sensible version of the AE-8 electron model environment was completed in December 1983. It has been sent to users on the model environment distribution list and is made available to new users by the National Space Science Data Center (NSSDC). AE-8 is the last in a series of terrestrial trapped radiation models that includes eight proton and eight electron versions. With the exception of AE-8, all these models were documented in formal reports as well as being available in a machine sensible form. The purpose of this report is to complete the documentation, finally, for AE-8 so that users can understand its construction and see the comparison of the model with the new data used, as well as with the AE-4 model.

Vette, James I.↗
NASA NTRS1992

Intercomparison results for FIFE flux aircraft

Three atmospheric research aircraft were used to explore the atmospheric boundary layer during FIFE: the National Research Council of Canada Twin Otter, the National Center for Atmospheric Research (NCAR) King Air, and the University of Wyoming King Air. The aircraft were used to measure the mean and turbulent structure of the boundary layer and its variation with height, time, and space. These measurements are important to FIFE because they are being used to scale up point surface observations to landscape scales and because they can be used to relate satellite radiance measurements to boundary layer processes. Because the aircraft were used in coordinated flight patterns to investigate changes within and between intensive field campaigns, wing-to-wing intercomparisons were made so that measurements from one aircraft could be related to another. Intercomparisons were flown on 4 days in 1987 and 3 days in 1989. The eddy correlation measurements of the mixed layer fluxes of moisture and sensible heat were of particular interest to FIFE. Sensible heat fluxes agreed within 15 W/sq m and moisture fluxes agreed within 21 W/sq m. Mean wind component differences were within 1.0 m/s, air temperature within 0.3 C, and mixing ratio within 2 g/kg. Standard deviations showed similar good agreement, with mean differences generally less than 0.1 m/s for the wind components and 0.03 C for potential temperature. Intercomparisons between the NCAR King Air and the Twin Otter showed better agreement in 1989 than in 1987. Overall, the results suggest that data from the FIFE boundary layer aircraft will need little correction to account for instrument biases and spurious fluctuations.

Macpherson, J. I.↗
NASA NTRS1993

Parameterization of surface heat fluxes above forest with satellite thermal sensing and boundary-layer soundings

The paper is concerned with the feasibility of determining the surface flux of sensible heat from forest using surface temperatures measured by a satellite together with soundings of temperature aloft in the unstable atmospheric boundary layer. Consideration is also given to the effect of the spatial scale of the surface temperature measurement on the parameterization by means of the scalar roughness. The latent heat flux is derived from the sensible heat flux by means of the energy budget. The data used in the study have been obtained during the HAPEX-MOBILHY experiment of 1986. The approach is based on turbulence similarity for the unstable atmospheric boundary layer.

Brutsaert, Wilfried↗