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  • 1
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    A Review of Convective Loss Data From Solar Central Receivers (1987)
    American Society of Mechanical Engineers
    Details
    Publication Date: 1987-05-01
    Description: A summary of previous experimental evaluations to determine convective losses from solar central receivers is given. In this review studies performed directly on actual central receivers or simulations that closely approximate central receiver geometries are considered. Because of the diversity of the previous studies, there are a number of classifications of the studies that can be made. From one perspective, two types of evaluations have been carried out: either those using performance data (often called efficiency tests), or those configuring the receiver so that losses can be more directly inferred (loss tests). In addition to classifying the experimental configurations according to geometry type (either external or cavity forms), it is also beneficial to distinguish between evaluations that take place when normal solar flux levels are incident upon the receiver (flux-on tests) and those made with no flux present (flux-off evaluations). Previous tests are categorized according to the method of testing used. Special attention is given to the range of the physical parameters represented by the experiments, particularly the Grashof number. Too often sufficient information to characterize forced convection contributions is not available, but it is shown that the total convective loss sometimes is lower than the predictions for natural convection alone. It is shown that performance-based data does not correspond well with loss-based data. The effects of directional effects of forced convection and general aspects of mixed (natural and forced) convection are not well established in the existing data. There have been some flux-on techniques recommended recently that may overcome some of the previously established concerns about the accuracy of flux-on data.
    Print ISSN: 0199-6231
    Electronic ISSN: 1528-8986
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by American Society of Mechanical Engineers
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  • 2
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    Heat Transfer Modeling of the IEA/SSPS Volumetric Receiver (1989)
    American Society of Mechanical Engineers
    Details
    Publication Date: 1989-05-01
    Description: During the summer and fall of 1987 in Almeria, Spain, a wire-pack receiver was tested by the International Energy Agency/Small Solar Power Systems (IEA/SSPS). The basic operation of the receiver is that: air is drawn through several layers of stainless steel wire screen; concentrated solar flux is directed on the face of the screen pack; the oxidized wires absorb the solar energy; and heat is transferred to the air flowing through the screen. Although the experiment goal was strictly proof-of-concept and was not receiver characterization, modeling efforts were initiated to help understand the experimental results. The steady-state performance of the receiver is modeled using the fact that the net solar and infrared radiative energy absorbed by each screen layer must be transferred to the air by convection. Basic performance trends and typical calculations of receiver efficiency are given. Model predictions and experimentally measured temperatures and flow rates are compared. Model predictions of receiver power and efficiency are generally higher than the test results (operational modifications of the receiver absorber as tested are believed to have produced nonideal conditions), but trends are consistent with experimental data.
    Print ISSN: 0199-6231
    Electronic ISSN: 1528-8986
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by American Society of Mechanical Engineers
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  • 3
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    Computer Simulation Results for Planar Reflectors and Flat Plate Solar Collectors (1980)
    American Society of Mechanical Engineers
    Details
    Publication Date: 1980-05-01
    Description: The benefits attributed to reflectors for increasing performance of flat plate collectors vary quite widely in the literature. In the present study, a detailed computer simulation is carried out to investigate the increase in performance. The results show that: Collectors should be placed at a higher tilt angle than usual; reflectors placed in front of the collectors can be tilted up 5 or 10 deg; and performance has a broad peak with respect to tilt angle. The system performance enhancement in Salt Lake City, Utah ranges from 1.16 for domestic hot water to 1.28 for space heating for equal reflector-collector areas, and the break even ratio of per area reflector to collector cost is from 16 to 28 percent for these systems.
    Print ISSN: 0199-6231
    Electronic ISSN: 1528-8986
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by American Society of Mechanical Engineers
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  • 4
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    Gradient Zone Constraints in a Salt-Stratified Solar Pond (1982)
    American Society of Mechanical Engineers
    Details
    Publication Date: 1982-11-01
    Description: An operational condition is defined for a salt-stratified solar pond. A criterion based on empirical evidence is formulated which shows a limit is approached as steady operating conditions are attained. For sodium chloride ponds, the criterion indicates a dependence between salt and temperature gradients during steady-state conditions. At the present time, appropriate data for explaining the physical basis of this relationship are not available. Significant results are found as a result of the gradient zone criterion. First, the gradient zone criterion leads to an explanation for the formation of an upper convecting zone. Results obtained with the gradient zone criterion relate to salt maintenance in a pond. Depending on the temperature operating conditions of a pond, a specific amount of salt must be in the pond. Also, salt concentration levels maintained in the upper and lower convecting zones are shown to significantly affect a pond’s thermal energy performance.
    Print ISSN: 0199-6231
    Electronic ISSN: 1528-8986
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by American Society of Mechanical Engineers
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  • 5
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    Simulation and Optimization of a Concentrated Photovoltaic System (2005)
    American Society of Mechanical Engineers
    Details
    Publication Date: 2005-12-06
    Description: Reported here is the development, using results of analysis and experiments, and optimization of a numerical model for a concentrated photovoltaic system. Models for the two major components of the system (cooling system and receiver) are developed separately from one another and then linked to simulate the performance for the entire system. The model is linked to yearly weather data and the optimization routines included in MATLAB are then used to select the input parameters (pump size, number of radiators, fan speed, etc.) which maximize the solar to electrical conversion efficiency of the system.
    Print ISSN: 0199-6231
    Electronic ISSN: 1528-8986
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by American Society of Mechanical Engineers
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  • 6
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    Solar Power Output Correlation With Utility Demand in Southern Nevada (1997)
    American Society of Mechanical Engineers
    Details
    Publication Date: 1997-05-01
    Description: Various solar electric system performance codes are used to predict the power generated by different solar power systems in the Southern Nevada area during 1990 by using the National Solar Radiation Data Base (NSRDB) for Las Vegas. The system types evaluated along with the prediction codes (shown in parenthesis) are as follows: a central receiver or a power tower system with various amounts of storage (SOLERGY), a Luz-type SEGS parabolic trough system without fossil fuel backup or storage (LUZERGY), a dish-Stirling system (DISH2, a conversion of direct beam radiation with constant collector/engine efficiency was used for this), and various arrangements of nonconcentrating photovoltaic devices (PVFORM). Comparisons of these results are made with the daily variations of load requirements of an electrical utility operating in the same geographical area. These comparisons are made for summer and winter periods. It is shown that several of the power generation schemes have summer peak outputs that occur at times very near to, but not coincident with, the peak utility load requirements. The power tower with a relatively small amount of thermal storage was the only scheme able to provide full power output at the times of summer peak demands. Winter peaks in this region occur during the night. Two comparisons are made that illuminate the summer load serving capability of solar generation in addition to simply showing time-variations of outputs. Included in these comparisons are the determination of the difference in time between the peak power output and the peak demand, as well as the normalized fraction of the peak power generated at the peak demand times.
    Print ISSN: 0199-6231
    Electronic ISSN: 1528-8986
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by American Society of Mechanical Engineers
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  • 7
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    Experimental investigation of radiative transfer between metallic surfaces at cryogenic temperatures (1969)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Radiative heat flux between two parallel copper disks at cryogenic temperature, showing dependence on emitter temperature and spacing
    Keywords: THERMODYNAMICS AND COMBUSTION
    Type: ASME PAPER 69-WA/HT-7 , AMERICAN SOCIETY OF MECHANICAL ENGINEERS, WINTER ANNUAL MEETING; Nov 16, 1969 - Nov 20, 1969; LOS ANGELES, CA
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    Predictions of the total emissivity of metals at cryogenic temperatures (1968)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Total emissivity predictions of metals at cryogenic temperatures
    Keywords: PHYSICS, SOLID-STATE
    Type: NASA-CR-73264 , TS-68-5 , 1968 CRYOG. ENG. CONF.; Jan 01, 1968
    Format: application/pdf
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  • 9
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    Predictions of the total emissivity of metals at cryogenic temperatures (1969)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Thermal radiation emissivity predictions for metal surfaces at cryogenic temperatures, comparing anomalous skin effect and Drude single electron theories
    Keywords: PHYSICS, GENERAL
    Format: text
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    NASA TECHNICAL REPORTS
  • 10
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    Small spacing analysis of radiative parallel metallic surfaces (1969)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Electromagnetic energy transmission factors for metal-dielectric-metal system, calculating net energy flux, noting effects of metal spacing, time, temperature level, etc
    Keywords: THERMODYNAMICS AND COMBUSTION
    Type: ASME PAPER 69-WA/HT-8 , AMERICAN SOCIETY OF MECHANICAL ENGINEERS, WINTER ANNUAL MEETING; Nov 16, 1969 - Nov 20, 1969; LOS ANGELES, CA
    Format: text
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