bluuebunny/crossref_metadata_2025 huggingface dataset:
A Simple Computer Program to Model Three-Dimensional Underground Heat Flow With Realistic Boundary Conditions
Authors: Metz P. D.
Published: January 2010

A FORTRAN computer program called GROCS (Ground Coupled Systems) has been developed to study three-dimensional underground heat flow. Features include the use of up to 30 finite elements or “blocks” of earth which interact via finite difference heat flow equations and a subprogram which sets realistic time and depth-dependent boundary conditions. No explicit consideration of moisture movement or freezing is given. GROCS has been used to model the thermal behavior of buried solar heat storage tanks (with and without insulation) and serpentine pipe fields for solar heat pump space conditioning systems. The program is available independently or in a form compatible with specially written TRNSYS component TYPE subroutines. This paper first describes the approach taken in the design of GROCS, the mathematics contained and the program architecture. Then, the operation of the stand-alone version is explained. Finally, the validity of GROCS is discussed. A companion paper serves as a user’s guide to the TRNSYS-compatible subroutine version.
Ceramic Technology for Solar Thermal Receivers
Authors: Kudirka A. A. , Smoak R. H.
Published: January 2010

Development of ceramic receiver technology for advanced solar thermal energy applications is being pursued in order to achieve significant reductions in energy cost and increase the potential application of solar thermal energy. Basically, structural ceramics are being seriously considered for solar applications because of their high temperature capability, their nonstrategic nature, and their potential for low cost. In this paper, candidate ceramic materials for solar receivers and their characteristics are described, potentially applicable fabrication and processing methods are discussed, and their applicability and promise for solar receivers is assessed. Receiver design requirements as well as system requirements for solar applications are reviewed. Promising areas of application of ceramic receivers in the near future are also discussed. Current ceramic receiver development status and plans are described, including one receiver which has been successfully tested at gas exit temperatures of up to 1425°C.
Three Experimental Techniques to Duplicate the Net Thermal Output of an Irradiated Collector Array
Authors: Fanney A. H. , Thomas W. C.
Published: January 2010

A relevant and repeatable test method is required to provide a means for rating solar domestic hot water systems. The test method should be independent of the geographical location of the laboratory and the prevailing outdoor environment. Three experimental techniques which reproduce the net thermal output of a normally irradiated solar collector without the use of a solar simulator are investigated. These techniques include the use of an in-line electrical heat source only, use of a nonirradiated collector array in series with a heat source, and the use of electrical strip heaters attached to the back of nonirradiated absorber plates. Two single-tank direct solar domestic hot water systems have been fabricated at the National Bureau of Standards to validate each experimental technique. The solar collector array of one system is subjected to outdoor meteorological conditions. The second system, used to validate the experimental techniques, is located entirely indoors. Daily tests of the solar domestic hot water system with the irradiated collector array were subsequently repeated for the laboratory system using the three experimental techniques. Based on results from several nearly clear and intermittently cloudy days, all three simulation techniques reproduce the net thermal output of the normally irradiated collector array within 4 percent. Pump controller operation can be closely reproduced using two of the techniques. Advantages and limitations of each method are discussed.
A Graphical Method for Passive Building Energy Analysis
Authors: Subbarao K. , Anderson J. V.
Published: January 2010

A new graphical approach which establishes the groundwork for a simplified building design method is presented. The admittances of each of the building elements to the major driving functions (principally outdoor temperature and solar radiation) are represented in the form of a two-dimensional vector, and the overall dynamic response of the building is obtained by vector addition. The interaction among components is shown to be naturally accounted for by a modification of the admittance of the component. Emphasis is placed on diagrammatic vector addition to quickly give the user an idea of the relative size of the dynamic contribution made by each component of the building. This is analogous to the addition of the steady-state heat loss coefficients through various elements of the building to form the overall heat loss coefficient. From the results of this addition and from a simple analysis of the weather, one can easily obtain (i) the elevation of the average indoor temperature above the average outdoor temperature, and (ii) the amplitude and phase of the diurnal (or any other frequency) fluctuation of the indoor air temperature. The former is a measure of the solar gain that actually reaches the indoor air, and the latter describe the various thermal masses in the building and their coupling to the indoor air and solar radiation. Thus, these values represent in a succinct yet thorough manner the interaction of the building and its environment.
Buoyancy Effects in the Entrance Region of an Inclined Multirectangular-Channel Solar Collector
Authors: Morcos S. M. , Abou-Ellail M. M. M.
Published: January 2010

A numerical procedure is presented for the entrance region of an inclined multirectangular-channel solar collector with significant buoyancy effects. The upper wall heat flux is taken to be uniform, while the lower wall is assumed to be insulated. The heat flux distribution on the side wall of the rectangular channel is obtained by coupling a heat-conduction numerical procedure in the metallic region surrounding the channel to the main numerical procedure which solves the hydrodynamic and energy equations of the flow inside the channel. Numerical results are presented for water flowing in a multirectangular-channel solar collector with an aspect ratio AR = 4 inclined at an angle α = 30 deg to the horizontal. The resulting variable heat flux distribution on the side wall enhances the intensity of the secondary flow. The effects of the nonuniform heat flux distribution and the spacing between the rectangular channels on the variation of Nusselt number in the entrance region are presented for different values of Rayleigh number. At a value of Ra = 5 × 105, Nusselt number is more than 300 percent above the constant property prediction.
Fluid Mechanical Design of a Dry-Cooling System Thermal Storage Reservoir, or Stratification Minimization in Horizontal Channel Flow
Authors: Guyer E. C. , Golay M. W.
Published: January 2010

The use of a capacitive Thermal Storage Reservoir (TSR) initially filled with cold water as part of a dry cooling system for a central power station is attractive economically if the reservoir can be designed to operate in an approximate “plug-flow” mode—discharging cold water to the condenser and filling with hot water from the cooling tower. Such a system would avoid the loss of station capacity associated with dry cooling at high dry-bulb temperatures, and the economic penalties due to such losses when they are coincident with electrical demand peaks (as is common in the United States). The initial employment of this concept is most likely to occur in solar-powered thermal electric power stations in arid climates in view of the likely low thermal efficiency and limited cooling water access of such plants. Buoyant flow stratification hinders attaining this goal since it can cause “short circuiting” of the TSR. For adequate flow control, a long narrow reservoir configuration is desirable. In investigating the behavior of such a TSR experimentally, it was found over the range of cases examined that injection of water into a long narrow reservoir which is initially at a different temperature always results in a stratified flow superimposed upon the gross plug flow of the TSR, and it was found that acceptable performance could be obtained inexpensively by placing flow-constricting barriers at regular intervals along the reservoir length. Experimental investigation of barrier design and spacing has permitted definition of a practical prototype TSR design which provides approximately 87 percent of the thermal capacity of a plug flow TSR.
Temperature Control of Line-Focus Solar Collectors
Authors: Wright J. D. , Masterson M.
Published: January 2010

Solar thermal electric power and industrial process heat systems may require a constant outlet temperature from the collector. This temperature may be efficiently maintained by adjusting the circulating fluid flow rate. Using frequency response techniques, simple relations are developed which relate controller tuning constants to collector construction and field layout. Successful controller tuning is shown to be a compromise between good response at high flow rates and stability at low flow rates. The rules of thumb are then tested by performing dynamic numerical simulations of a collector row with flow rate control.
Operational Characterization of the Solar-Thermal Power System Near Willard, New Mexico
Authors: Krivokapich G. A. , Fenton D. L. , Abernathy G. H. , Otts J. V.
Published: January 2010

The output capacity of the solar-thermal power system located near Willard, New Mexico was 19 kw (25 hp), with a primary application for irrigation pumping. Solar radiation was collected with north-south axis, east-west tracking, parabolic trough collectors having a total aperture area of 1275 m2 (13,720 ft2). Thermal storage was adequate for 20 hr. of power system operation utilizing a reaction-type turbine in conjunction with an organic Rankine-cycle heat engine. Operating efficiencies for the turbine component, heat engine, and the complete power system were 65–80 percent, 10–16 percent, and 1–3 percent, respectively. With the Willard system fully operational and near-term hardware improvement, an annual performance of 22 kw hr/m2 of collector aperature area could be expected. Examples of component operation under variable environmental conditions are presented for the winter and summer seasons. Maintenance experience with the Willard system is also given.
Antireflection Pyrex Envelopes for Parabolic Solar Collectors
Authors: McCollister H. L. , Pettit R. B.
Published: January 2010

Parabolic trough solar collectors utilize glass envelopes around the receiver tube in order to reduce thermal losses. Antireflective (AR) coatings applied to the envelope can potentially increase the solar transmittance by 7 percent. An excellent AR surface can be formed on Pyrex (Corning Code 7740 glass) by first heat treating the glass to cause a compositional phase separation. After heat treating, a surface layer is removed using a pre-etch solution of aqueous ammonium bifluoride. Finally, the AR layer is formed by etching in a solution containing hydrofluorosilic and ammonium bifluoride acid. Processing parameters studied included the phase separation temperature and heat treatment time, the pre-etch time, and the etching bath temperature and time. AR-coated samples with solar transmittance values > 0.97, as compared to a value of 0.91 in untreated samples, were obtained for a range of heat treatment temperatures from 560–630°C. The phase separation time and temperature interact so that at 630°C short times are required (3 hrs) while at 560°C longer times are necessary (24 hrs). Optimum values for the other processing parameters are 12–18 min in the pre-etching bath, and 5–10 min in the film forming bath when maintained between 35–45°C. Application of this process to full scale 3-m-long × 6-cm dia Pyrex envelopes was successful in producing solar transmittance values ≥ 0.97.
A Rating Procedure for Solar Domestic Water Heating Systems
Authors: Klein S. A. , Fanney A. H.
Published: January 2010

A rating procedure for solar domestic hot water systems is described which combines the advantages of short-term system tests and correlations of long-term thermal performance. The testing procedure consists of two indoor tests which are in accordance with ASHRAE Standard 95-1981, except for one additional measurement needed only for systems employing a heat exchanger between the collector fluid and the potable water. The test results are plotted in a manner in which they can be used to estimate the long-term performance of the solar water heating system for any location where site-specific, monthly-average meterological data are available. The annual solar function obtained in this manner provides the recommended rating indicator. The validity of this rating procedure is first demonstrated by simulations. Further support is provided by experiments conducted at the National Bureau of Standards.
An Analysis of a Flat-Plate Solar Collector With Internal Boiling
Authors: Abramzon B. , Yaron I. , Borde I.
Published: January 2010

The extended mathematical model of a flat-plate solar collector-evaporator permits prediction of the effects of boiling of the working fluid in the collector tubes on the efficiency of the collector. The efficiency increases sharply and approaches the ideal on transition from single phase flow to the subcooled and saturated boiling regimes, regardless of the nature of the working fluid.
Data-Dependent Systems Approach to Solar Energy Simulation Inputs
Authors: Pandit S. M. , Rajurkar K. P.
Published: January 2010

The paper proposes and illustrates an application of a recently developed methodology called Data Dependent Systems (DDS) to modeling and analysis of solar insolation data. Such an approach is shown to be capable of combining the advantages of deterministic as well as stochastic models. Major dynamic patterns are successfully reproduced by the models. The model characteristics reveal the relation of these patterns to direct and diffuse insolation as well as to constant and variable weather dynamics. The relation of the dynamic patterns with a physical model is developed to show that a more realistic estimate of the extinction coefficient is obtained from the DDS models.
A Variational Principle for the Linear Coupled Thermoelastodynamic Analysis of Mechanism Systems
Authors: Sung C. K. , Thompson B. S. , McGrath J. J.
Published: January 2010

A variational principle is presented which provides the basis for developing the equations governing the coupled thermoelastic response of planar flexible mechanism systems subjected to both mechanical and thermal loading. These systems are modeled as chains of continua with anisotropic elastic constitutive equations. By permitting arbitrary independent variations of the system parameters for each link, approximate equations of motion and boundary conditions may be systematically constructed. As an illustrative example, the derivation of the problem definition of a flexible connecting rod of a slider crank mechanism subjected to thermal shock is presented.
On the Elimination of the Branching Problem in the Synthesis of Spatial Motion Generators With Spheric Joints. Part 1: Theory
Authors: Sandor G. N. , Zhuang Xirong
Published: January 2010

A theory is proposed for elimination of the branching problem in the synthesis of spatial motion generators with at least one spheric joint. The theory is also applicable to planar linkages as a special case of spatial mechanisms. Applications of the theory are presented in Part 2 of the paper.
Symbolic Notation and Kinematic Equations of Motion of the Twenty-Two Basic Spur Planetary Gear Trains
Authors: Gibson D. , Kramer S.
Published: January 2010

This paper introduces a symbolic notation for describing two degree-of-freedom spur planetary gear trains with the configuration of two central gears, one carrier or arm, and at least one planet gear. This simple notation is then used to write the kinematic equation of motion for this type of planetary gear train without the need to develop any intermediate equations. It is also shown that, there are exactly 22 basic spur planetary gear trains with this configuration and not 34 as Levai [1] previously found. These 22 planetary gear trains are illustrated along with their symbolic notation and kinematic equation of motion.
Optimal Synthesis of Function Generators Without the Branch Defect
Authors: Tinubu S. O. , Gupta K. C.
Published: January 2010

A new method is proposed for the optimum (mini-max structural error) synthesis of function-generating mechanisms with unlimited number of design specifications, and which are free from the branch defect. This method does not require the use of explicit branching constraints. It is developed and illustrated with numerical examples for the planar four-bar and the spatial R-S-S-R mechanisms.
The Image Curve of the Planet in a Spherical Epicyclic Gear Train
Authors: Ge Q. , McCarthy J. M.
Published: January 2010

This paper uses the Euler parameters of the motion of the planet of a spherical epicyclic gear train to obtain a curve on the surface of a hypersphere in four dimensions. This curve, called the image curve, represents the rotational motion of the planet as it rolls without slipping on the fixed gear. Two image curves are obtained for two different choices of moving and fixed reference frames and it is shown that they are related by an orthogonal transformation in four dimensional space. The differential properties of the image curve are computed and it is found that the curvature and torsion are constant. A reference position is chosen and the canonical frame and instantaneous invariants of the motion are determined in terms of the dimensions of the gear train.
An AI-Based Approach for the Integration of Multiple Sources of Knowledge to Aid Engineering Design
Authors: Mayer A. K. , Lu S. C.-Y.
Published: January 2010

A model for integrating multiple sources of knowledge within engineering expert systems is presented. It allows possible conflicts between multiple knowledge sources to be logically resolved at run-time rather than during the knowledge acquisition stage. Unlike the traditional approach in which the knowledge engineer is responsible for resolving conflicting views, resolutions are dynamically accomplished by the knowledge sources themselves and/or by system users. The system user is included as a problem-solving colleague to select a proper strategy from those offered by different experts. Both qualitative and quantitative constraints are traced during problem solving and can be retracted if necessary. The model has been successfully implemented in an engineering design domain to demonstrate the basic ideas. This research is our first step in a long-term effort to develop a cooperative problem-solving paradigm for knowledge-based engineering systems.
The Second Law Efficiency of Solar Energy Conversion
Authors: Gribik J. A. , Osterle J. F.
Published: January 2010

The controversy over the proper expression for the theoretical maximum conversion efficiency of solar devices is resolved. The correct expression, ηmax = 1 −4/3 (To/Ts), relates to the maximum work that can be done by a device which accepts blackbody radiation at Ts and rejects heat to the ambient at To. A general bilinear dissipation equation for solar devices is derived. The effect of back-radiation is considered, and the efficiency decrease due to atmospheric scattering is determined.
Flow and Heat Transfer of a Stably Stratified Fluid Through an Enclosure
Authors: Chaney S. R. , Humphrey J. A. C. , Month L. , Shah A.
Published: January 2010

The flow of a stably stratified fluid, or thermocline, through a cubical enclosure with: (a) strongly conducting; and (b) weakly conducting side-walls, was investigated experimentally. The flow Peclet number and enclosure aspect ratio were varied in the experiment. Flow visualization revealed buoyancy-affected motions in both side-wall configurations. During the charging period of an energy storage cycle, for the strongly conducting side-wall case, axial heat conduction along the side-wall induced an upward-directed buoyant force on the fluid adjacent to the wall in the lower (colder) part of the enclosure. This was in contrast to a downward-directed force on near-wall fluid in the weakly conducting side-wall case. However, the motions induced by the forces were relatively weak compared to the main flow, and in the weakly conducting wall case appeared to be confined to thin fluid layers adjacent to the enclosure side-walls. The cumulative influence of buoyant forces was most noticeable for long times, in flows with small Peclet number and conducting side-walls. Measurements of temperature and of the energy storage performance characteristics of the thermocline were made as a function of time. Predictions of these quantities based on the analytical solution of the transient, one-dimensional, energy conservation equation are in good agreement with the measurements.
Solar Tests of Aperture Plate Materials for Solar Thermal Dish Collectors
Authors: Jaffe L. D.
Published: January 2010

In parabolic dish solar collectors, walk-off of the spot of concentrated sunlight can be a hazard if a malfunction causes the concentrator to stop following the sun. A test program, therefore, was carried out to evaluate the behavior of various ceramics, metals, and polymers under solar irradiation of about 7000 kW/m2 (peak) for 15 min. The only materials that did not slump or shatter were two grades of medium-grained extruded graphite. High-purity slip-cast silica might be satisfactory at somewhat lower flux. Oxidation of the graphite appeared acceptable during tests simulating walk-off, acquisition (2000 cycles on/off sun), and spillage (continuous exposure of a receiver aperture lip).
Aerodynamic Tower Shake Force Analysis for VAWT
Authors: Loth J. L.
Published: January 2010

Vertical axis wind turbines (VAWT) are subjected to blade lift forces which vary continuously in both magnitude and direction. These blade lift forces are transmitted via the blade support arms to the tower. The resulting tower force vector is a composite of: a downwind and a crosswind average force component, rotating force vectors, and force vectors oscillating in the crosswind direction. The frequency of the rotating and oscillating forces are multiples of the product of Bω, where B is the number of blades used and ω is the rotor angular velocity. The magnitude of the largest tower shake force vector is of the same order as the average downwind force component, and may represent a serious design constraint in the calculation of the required tower stiffness. A closed-form solution for the tower force vectors has been derived, by introducing a suitable wind interference model. It shows that the magnitude of the largest tower shake force vector, using a three-bladed rotor, is four times smaller than with a two-bladed rotor. The Betz limit and the optimum tip speed ratio as a function of solidity has been derived by comparison with two semicylindrical actuators in series.
Observations on the Decay of a Thermocline in a Rock Bed With No Net Fluid Flow
Authors: Beasley D. E. , Clark J. A. , Holstege M. J.
Published: January 2010

The transient thermal response of a rock bed with no net fluid flow is examined following all-day charging under clear sky conditions. The experimental system consists of 1.86 m2 (20 ft2) of flat-plate solar collectors using air as the working fluid, a flow control system, and a 0.357 m3 (12.6 ft3) rock bed for thermal energy storage. A thermocline is established in the bed during charging due to the time-varying nature of the collector outlet temperature. Experimental measurements of the temperature distribution in the bed for a 13-hour stagnation period allow a preliminary estimate of the loss of available energy in the storage medium. The net loss in thermodynamic availability is 30 percent. Since the temperatures in the upper regions of the bed are lower than those in the central regions at the end of charging under clear sky conditions, the possibility of natural convection motion of the fluid in the bed exists. An “apparent” local thermal diffusivity is calculated and from comparison with stagnant bed values indicates that natural convection motion may occur in the upper regions of the bed.
A Fourier Transform Approach to Building Simulations With Thermostatic Controls
Authors: Subbarao K. , Anderson J. V.
Published: January 2010

Analyzing the thermal behavior of a linear system, such as a building (with some commonly made approximations), is greatly simplified in the frequency domain because of the decoupling of different frequencies. Thermostatic controls, an important part of building systems, invalidate this decoupling since they respond only to the temperature at a particular time (i.e., to the sum of all frequencies). Nevertheless, it is shown that by suitably formulating the problem, buildings with thermostatic controls can be simulated in the frequency domain, even when the set-point is a function of time. An hour-by-hour profile of indoor temperature and auxiliary energy requirements are obtained without doing an hour-by-hour simulation. In the solution process, a function—the “temp-aux” function—is introduced which determines both the temperature and auxiliary energy profiles. This function is of general interest in building energy calculations.
Measured Average Wind Speeds in Western Kansas: A Comparison With NWS Data and the Effect of Small Terrain Differences
Authors: Thomann G. C. , Barfield M. J. , Myers G. A.
Published: January 2010

The average wind speed at 30 ft height was measured at 19 sites in the Western Kansas region during June 1980–July 1982. Two things were noted from the measurements. First, NWS measured average wind speeds in the region for the same period were about 1.1 mph higher than those measured at the 19 sites. A NWS model anemometer was calibrated, and when the calibration results were applied to the NWS data, the difference was largely removed. Second, there was considerable variation between the measured average wind speeds at the 19 sites, even though the sites were fairly close together, had similar surface cover near each site, and had only very small elevation changes around the towers. An attempt was made to reduce the difference between the measured average wind speeds by a correction based on the small elevation features in the 10-mile radius area surrounding each measurement tower. This measurement correction significantly reduced the differences in the measured wind speeds.
Use of Integrated Day-Long Stagnation Temperature for Measuring Changes in Solar Collector Materials Properties
Authors: Thomas W. C. , Dawson A. G. , Waksman D.
Published: January 2010

Measurements of the maximum temperatures reached by solar-energy-absorbing surfaces provide a useful method for detecting possible degradation in the optical and heat transfer properties of materials used in collectors. This investigation shows that a method based on integrating the absorber temperature rise over ambient and solar irradiation on a daily basis has advantages over alternative test methods based on steady-state measurements of either absorber stagnation temperature or collector thermal efficiency. A nonsteady-state analytical model is developed and used to evaluate the sensitivity of the proposed test method to material degradation and environmental effects. Outdoor data are presented to validate the analytical model and depict typical results that can be expected using the test procedure.
Stochastic Modeling of Transient Heat Flow Through Walls
Authors: Haghighat F. , Unny T. E. , Chandrashekar M.
Published: January 2010

Solar radiation and temperature vary during the day. These variations are also subject to “random” fluctuations caused by rapid changes in atmospheric conditions. In this paper a procedure has been developed to model the rate of heat flow through a building wall with consideration given to the stochastic character of the problem. The stochastic method generates outputs that reflect fluctuations in the input variables (and parameters). This enables the analyst to select or design components for specified confidence levels. The validity of the procedure is demonstrated through examples.
Method for Evaluating Wind Turbine Wake Effects on Wind Farm Performance
Authors: Neustadter H. E. , Spera D. A.
Published: January 2010

A method of testing the performance of a cluster of wind turbine units and data analysis equations are presented which together form a simple and direct procedure for determining the reduction in energy output caused by the wake of an upwind turbine. This method appears to solve the problems presented by data scatter and wind variability. Test data from the three-unit Mod-2 wind turbine cluster at Goldendale, Washington, are analyzed to illustrate the application of the proposed method. In this sample case the reduction in energy was found to be about 10 percent when the Mod-2 units were separated a distance equal to 7 dia and winds were below rated.
A Performance Prediction Methodology for Integral Collection-Storage Solar Domestic Hot Water Systems
Authors: Zollner A. , Klein S. A. , Beckman W. A.
Published: January 2010

A performance prediction methodology is developed which is applicable to most commercially available integral collection-storage passive solar domestic hot water systems. A computer model of a general ICS component was created to be compatible with the transient simulation program TRNSYS[3], and was used to develop and verify the simpler monthly performance prediction method. The method uses the system parameters from available test methods, monthly average climatic data, and load size to predict long term performance of ICS systems.
Description and Testing of a Non-Evacuated 1.5×CPC Collector Thermal Performance Comparison With Other Collector Types
Authors: Collares-Pereira M.
Published: January 2010

A 1.5 × non-evacuated CPC type concentrator is described and tested. The results obtained can be summarized by F′ηo = 0.673 ± 0.001 and F′U = (2.64 ± 0.041) W/m2 ° C. The early average performance of the concentrator is calculated and compared with the performance of two other collector types at constant operating temperature: a selectively coated regular flat plate and an evacuated tube type collector. It is shown that the concentrator performs better than both the flat plate and the evacuated tube collector for constant operating temperatures for 35° C to 100° C in a climate like the one in Lisbon. The three collectors are also compared operating in two systems: (1) DHW in which they all deliver comparable yearly average amounts of energy, and (2) IPH at 95° C (process return temperature = 65° C) in which the flat plate delivers ∼30 percent less yearly energy on the average in comparison with the other two which behave very much in the same way. The 1.5 × low cost is discussed in comparison with the other two collector types, establishing the concentrator as an excellent choice for hot water heating applications.
Performance of Series Solar-Assisted Heat Pump Systems in TECH House I
Authors: Reid R. L. , McGraw B. A. , Bedinger A. F. G.
Published: January 2010

Two configurations of series solar assisted heat pumps were experimentally evaluated in TECH House I on the University of Tennessee campus in Knoxville, Tenn. During the 1979–1980 heating season, a 4.2 m3 (1100 gal) insulated above ground storage tank was utilized. During the 1980–1981 heating season, the storage system consisted of an uninsulated 7.6 m3 (2000 gal) steel tank buried 2.1 m (7 ft) in the ground. For 1979–1980 the heating season system performance factor was 2.42 and the system’s maximum peak electric demand was 11.20 kW. For 1980–1981 the heating season performance factor increased to 3.16 while the maximum peak electric demand decreased to 4.33 kW.
Wind-Induced Heat Losses From Solar Collector Arrays on Flat-Roofed Buildings
Authors: Kind R. J. , Kitaljevich D.
Published: January 2010

This paper presents data for convective heat transfer coefficients on the front surface of a free-standing array of solar collectors mounted on the flat roof of a low warehouse-type building and exposed to the wind. The data were obtained by testing a 1:36 scale model in highly turbulent nonuniform flows which simulated the natural wind. For typical full scale conditions, the heat transfer coefficients are substantially lower than those given by a commonly used correlation. The coefficients are only mildly sensitive to wind direction, location of the array on the roof and characteristics of the wind.
Parametric Study of Salt Gradient Solar Ponds
Authors: Beniwal R. S. , Saxena N. S. , Bhandari R. C.
Published: January 2010

A mathematical model for efficiency of a salt gradient solar pond is described. Heat losses from the bottom of the pond have been calculated, and the results for the effective thermal conductivity with the thicknesses of various insulating materials have been presented. The effect of the ground thermal resistance on the efficiency of the pond for different values of ΔT/So have also been shown.
A TRNSYS/GROCS Simulation of a Horizontal Coil Ground-Coupled Heat Pump
Authors: Conlin F. , Johnson W. S. , Wix S.
Published: January 2010

The ground-coupled heat pump system in TECH House I at the University of Tennessee has been modelled using TRNSYS/GROCS and the results have been compared with actual performance data for both the 1982–83 heating season and the 1983 cooling season. Hourly measurements of various ground temperatures, conditioned space temperatures, power requirements and heat transferred to or from the ground and the conditioned space were made. Results indicate that the model prediction is within 5 percent of the measured seasonal performance factor for both the summer and winter season. Parametric studies were undertaken to examine the effect of ground coil length, soil thermal conductivity, and the heat pump performance rating on the overall seasonal performance of the system. Overall performance is shown to increase with improved performance and increased soil thermal conductivity while the coil length shows an optimum value due to the increase of pumping power with length.
Frequency-Response Matching to Optimize Wind-Turbine Test Data Correlation
Authors: Hansen A. C. , Hausfeld T. E.
Published: January 2010

Pre-averaging is often applied to wind turbine test data to improve correlation between wind speed and power output data. In the past, trial and error or intuition have been used in the selection of pre-averaging time and researchers and institutions have differed widely in their pre-averaging practice. In this paper a standardized method is proposed for selection of the optimum pre-averaging time. The method selects an averaging time such that the test data are low-pass-filtered at the same frequency as the response frequency of the test wind turbine/anemometer system. A theoretial method is provided for estimation of the wind system transfer function as a function of the anemometer location, rotor moment of inertia, the stiffness of the connection between the rotor and the electrical grid, hub height, rotor speed and wind speed. The method is based in proven theory, repeatable, easy to use and applicable to a wide range of wind turbines and test conditions. Results of the transfer function predictions are compared with the measured response of two wind systems. Agreement between the predicted and measured response is completely adequate for the purposes of the method. Example results of calculated averaging times are presented for several wind turbines. In addition, a case study is used to demonstrate the dramatic effects of test design and data analysis methods on the results of a power coefficient measurement.
“Deus-Ex-Machina” Mechanism Reconstruction in the Theater of Phlius, Corinthia
Authors: Papadogiannis Argyris S. , Tsakoumaki Marilena C. , Chondros Thomas G.
Published: December 2009

In some ancient Greek drama plays, the stage machine used to bring the gods or the heroes of the tragedy on stage, known with the Latin term deus-ex-machina, was used for the solution of an apparently insoluble crisis. A twin-facing stone base was found in the theater of Phlius in Corinthia, Greece, behind the stage building. The existence of similar foundations in other ancient theaters indicates their use for specific purposes connected with the needs of the play. An attempt to reconstruct the mechanism is presented based on archeological evidence and literary descriptions. The reconstructed mechanism was designed for path generation and comprised a single beam with ropes controlling its planar motion and a sidle twin lifting system.
A General and Numerically Efficient Framework to Design Sector-Type and Cylindrical Counterweights for Balancing of Planar Linkages
Authors: Demeulenaere B. , Verschuure M. , Swevers J. , De Schutter J.
Published: December 2009

This paper extends previous work concerning convex reformulations of counterweight balancing by developing a general and numerically efficient design framework for counterweight balancing of arbitrarily complex planar linkages. At the numerical core of the framework is an iterative procedure, in which successively solving three convex optimization problems yields practical counterweight shapes in typically less than 1 CPU s. Several types of counterweights can be handled. The iterative procedure allows minimizing and/or constraining shaking force, shaking moment, driving torque, and bearing forces. Numerical experiments demonstrate the numerical superiority (in terms of computation time and balancing result) of the presented framework compared to existing approaches.
Design of Single, Multiple, and Scaled Nonlinear Springs for Prescribed Nonlinear Responses
Authors: Jutte Christine Vehar , Kota Sridhar
Published: December 2009

Nonlinear springs enhance the performance of many applications including prosthetics, microelectromechanical systems devices, and vibration absorption systems. This paper describes a comprehensive approach to developing compliant elements of prescribed nonlinear stiffness. It presents a generalized methodology for designing a single planar nonlinear spring for a prescribed load-displacement function. The spring’s load-range, displacement-range, and nonlinear behavior are matched using this methodology, while also addressing stress, material, stability, and space constraints. Scaling guidelines are included within the optimization to relax the constraints on the solution space. Given the nonlinear nature of the spring designs, this paper further investigates their function in new configurations. Compliant structures with customized elastic properties are constructed by exploiting symmetry and by arranging nonlinear springs in series and/or in parallel. Scaling guidelines are used to meet new design specifications. The guidelines allow adjustment of load-range, displacement-range, material, and the overall footprint while preserving the spring’s nonlinear behavior without violating stress constraints. Various examples are provided throughout the paper to demonstrate the implementation and merit of these design approaches.
Optimal Design Accounting for Reliability, Maintenance, and Warranty
Authors: Wang Zhonglai , Huang Hong-Zhong , Du Xiaoping
Published: December 2009

Reliability-based design (RBD) ensures high reliability with a reduced cost. Most of the RBD methodologies do not account for maintenance and warranty actions. As a result, the RBD result may not be truly optimal in terms of lifecycle reliability. This work attempts to integrate reliability, maintenance, and warranty during RBD. Three RBD models are built. The total cost of production, maintenance, and warranty are minimized. The computational procedures for solving the RBD models are developed. As demonstrated by two examples, the proposed RBD models meet not only the initial reliability requirement but also the maintenance and warranty requirements with reduced costs.
Module-Based Static Structural Design of a Modular Reconfigurable Robot
Authors: Mohamed Richard Phillip , Xi Fengfeng (Jeff) , Finistauri Allan Daniel
Published: December 2009

In this paper, the structural design of modular reconfigurable robots (MRRs) is studied. This problem is defined as the determination of proper module sizes according to the robot’s payload and end-effector deflection specifications. Because an MRR has multiple configurations, a simple design process is proposed in order to avoid performing the structural design stage at each configuration. The final structural design is only carried out at a single configuration that can guarantee the robot’s satisfactory performance for all remaining feasible configurations. It is shown that the module structural design stage can be performed at the local coordinate frame of each module. While the module local force requirement can be fully determined, the determination of the module local deformation requirement is redundant. Thus, there can exist multiple design solutions. To overcome this problem, a nonlinear approach using a genetic algorithm is used to search for an optimal solution. Finally, a design simulation is performed on an example MRR, and the results show the effectiveness of the proposed design method.
A Numerical Approach to Calculation of Load Sharing in Planetary Gear Drives
Authors: Montestruc Alfred N.
Published: December 2009

In AGMA 6123-B06 [2006, “Design Manual for Enclosed Epicyclic Gear Drives,” ANSI/AGMA Paper No. 6123-B06], a specific table is given for estimation of the planet load share factor Kγ, as it is termed in that publication; that table is vague as to the exact relationship of tolerance and load to the value of Kγ. Others have done significant works on the subject of load sharing among planets; a brief review of that work is presented. This work calculates a useful value of Kγ directly from design tolerance values and the torque applied to the carrier, and other factors showing how this can be done. This formulation is designed explicitly for nonfloating systems, but may be adaptable to floating systems. The use of flexible planet pins to improve load sharing is discussed. In addition, treating Kγ as a constant with respect to torque for a given planetary design is shown to be inaccurate.
An Ease-Off Based Optimization of the Loaded Transmission Error of Hypoid Gears
Authors: Artoni A. , Kolivand M. , Kahraman A.
Published: December 2009

Loaded transmission error (LTE) is one of the primary sources of gear noise and vibration. While ease-off topography has been shown to be powerful in improving the contact properties of a gear drive, its optimization to minimize LTEs has been an open problem in the gear literature. Through the formulation of an appropriate nonlinear optimization problem, this study proposes a novel methodology to systematically define optimal ease-off topography to simultaneously minimize LTEs and contact pressures, while concurrently confining the loaded contact pattern within a prescribed allowable region on the tooth surface to avoid any edge- or corner-contact condition. Effectiveness of this optimization is presented using a face-milled and a face-hobbed hypoid gear examples. These example analyses reveal particularly promising results that feature both a drastic reduction in LTE and an appreciable decrease in the maximum contact stress. Although the method is employed here for hypoid gears, its intrinsically systematic formulation enables straightforward applicability to any kind of gears. The methodology presented in this work can be a useful aid for gear engineers to determine optimal ease-off topographies without having to rely on time-consuming trial-and-error approaches or on a priori subjective judgments.
Synchronous Deglacial Overturning and Water Mass Source Changes
Authors: Roberts Natalie L. , Piotrowski Alexander M. , McManus Jerry F. , Keigwin Lloyd D.
Published: December 2009

The Depths of the Changes

Over the course of the past glacial cycle, there have been two major types of rapid, large climate warming events: shorter-lived warm intervals lasting on the order of 1000 years and the last glacial-interglacial transition. Although both involved dramatic changes in large-scale ocean circulation, the extent to which those changes were similar is unclear.

Roberts
et al.

(p.
75
) analyzed the neodymium isotopic composition of the Fe-Mn oxide coatings of planktonic foraminifera and reconstructed patterns of Atlantic Ocean circulation during Heinrich event 1, a rapid global climate fluctuation about 14,000 years ago involving the destruction of Northern Hemisphere ice shelves and the last deglaciation. While both the source of deep water and the whole-ocean overturning rate shifted rapidly and synchronously during the last deglacial transition, only upper ocean circulation strength was affected during Heinrich event 1.
O
-Mannosyl Phosphorylation of Alpha-Dystroglycan Is Required for Laminin Binding
Authors: Yoshida-Moriguchi Takako , Yu Liping , Stalnaker Stephanie H. , Davis Sarah , Kunz Stefan , Madson Michael , Oldstone Michael B. A. , Schachter Harry , Wells Lance , Campbell Kevin P.
Published: December 2009

Modifying Protein Modification

Alpha-dystroglycan (α-DG) is a cell-surface receptor that anchors the basal lamina to the sarcolemma by binding proteins containing laminin-G domains. This binding is essential for protecting muscle from contraction-induced injury, and defective binding is thought to cause a subclass of congenital muscular dystrophy (CMD) in humans. Mutations in six (putative) glycosyltransferase genes have been identified in patients with CMD, suggesting that glycosylation of α-DG may confer the ability to bind laminin. Despite extensive efforts for over 20 years, the actual laminin-binding moiety has remained unclear. Now,

Yoshida-Moriguchi
et al.

(p.
88
) have identified a phosphorylated
O
-mannosyl glycan on α-DG. This modification occurred in the Golgi via an unidentified kinase and was required for the maturation of α-DG into its laminin-binding form.
The Tasmanian Devil Transcriptome Reveals Schwann Cell Origins of a Clonally Transmissible Cancer
Authors: Murchison Elizabeth P. , Tovar Cesar , Hsu Arthur , Bender Hannah S. , Kheradpour Pouya , Rebbeck Clare A. , Obendorf David , Conlan Carly , Bahlo Melanie , Blizzard Catherine A. , Pyecroft Stephen , Kreiss Alexandre , Kellis Manolis , Stark Alexander , Harkins Timothy T. , Graves Jennifer A. Marshall , Woods Gregory M. , Hannon Gregory J. , Papenfuss Anthony T.
Published: December 2009

Be-Deviled Cancer

Recently, a deadly transmissible cancer has emerged in Tasmanian devils, the largest existing marsupial carnivore. This disease, devil facial tumor disease (DFTD), leads to the growth of large facial tumors that frequently metastasize to internal organs. DFTD is thought to be transmitted by biting, and leads to death of affected animals within months, usually by obstructing the animals' ability to feed. Consequently, in the last 10 years Tasmanian devil numbers have dropped by about 60%. There are no genetic tests, vaccines, or treatments available for this disease, and without intervention, models predict that DFTD could cause extinction of Tasmanian devils in the wild within 50 years. Several lines of evidence suggest that DFTD is transmitted as a clonal allograft, whereby the cancer cells themselves are the agents of tumor transmission.

Murchison
et al.

(p.
84
) examined this hypothesis in detail by genotyping 25 tumor-host pairs from around Tasmania at 14 microsatellite loci and at a variable mitochondrial polymorphism. DFTD tumors were indeed found to be genetically distinct from their hosts and almost completely genetically identical to one another, supporting the idea of transmission by allograft.