bluuebunny/crossref_metadata_2025 huggingface dataset:
Configurations of Robot’s Manipulators and Their Identification, and the Execution of Prescribed Trajectories. Part 2: Investigations of Manipulators Having Five, Seven, and Eight Degrees of Freedom
Authors: Litvin F. L. , Costopoulos T. , Parenti Castelli V. , Shaheen M. , Yukishige Y.
Published: January 2010

The methods discussed in Part 1 of this paper are applied for the determination of all potential configurations of manipulator links and the execution of prescribed trajectories. The research is performed for manipulators having five, seven, and eight degrees of freedom.
Workspace Analysis of Mechanical Manipulators Using Polynomial Discriminants
Authors: Kohli D. , Spanos J.
Published: January 2010

A new method, for the investigation of manipulator workspace, based on polynomial displacement equations and their discriminants is proposed in this paper. The approach followed enables one to obtain (a) analytical expressions describing the workspace boundary surfaces in Cartesian coordinates, (b) the distribution of the number of ways to position the hand inside the workspace, and (c) the conditions on kinematic parameters when the motion of the hand degenerates. Joint limitations are incorporated in the method. In the present paper and a companion paper [17], the method is rigorously applied to eight types of manipulators with various combinations of revolute and prismatic pairs having the last three revolute axes intersect orthogonally at at point. A numerical example is presented for illustration.
Optimal Design and Simulation of Vibrational Isolation Systems
Authors: Spiekermann C. E. , Radcliffe C. J. , Goodman E. D.
Published: January 2010

Vibration isolation of a rigid body on compliant mounts has many engineering applications. An analysis for solving these problems using a rigid body simulation and a penalty function optimization is discussed. The simulation is used to calculate natural frequencies and mode shapes, which are a function of the mount design parameters. Laboratory testing results are presented which verify the accuracy of the simulation. The optimization procedure penalizes natural frequencies in an undesirable frequency range and also large design changes. This penalty function is minimized by changing the mount design paramters consisting of the location, stiffness, and/or orientation. The result is a set of design parameters defining a vibration isolation system with natural frequencies moved away from the center of the undesirable frequency range. An interactive computer program was written which allows the engineer to use this technique as a design tool.
A Production System for Use of Global Optimization Knowledge
Authors: Li H. L. , Papalambros P.
Published: January 2010

A method employing ideas from applied artificial intelligence is proposed for use in design optimization. Knowledge of global information is incorporated in several rule types concerning constraint activity, redundancy, and dominance. The rules are organized in a production system that makes deductions about possible (globally) active sets. Two design examples demonstrate the strategy. Similar ideas may be used in other areas of the optimization process, particularly in design applications.
Evaluation of Forced and Self-Excited Vibrations at the Design Stage of Machine-Tool Structures
Authors: Yoshimura M.
Published: January 2010

This paper proposes a method for evaluating forced and self-excited vibrations at the design stage of machine-tool structural systems. Cross modal flexibilities between the forced excited and the displacement pick-up points are analyzed. The relationships between the highest allowable values of receptance and vibrational displacement, and the static compliance and modal flexibility are clarified. Then the algorithms of the evaluative methods which use those analyses are given. Using the proposed method, natural modes which must be disregarded in the evaluation of the characteristics can be determined, (1) even when directional orientations of the excited force at points in regard change greatly as a result of states of operations or cannot be definitely determined, and (2) even if damping properties are not clearly known. Designers can judge whether or not a given structural design has vibrational defects. The procedures of the evaluative method are exemplified with numerical examples.
An Analytical Method to Predict Efficiency of Aircraft Gearboxes
Authors: Anderson N. E. , Loewenthal S. H. , Black J. D.
Published: January 2010

A spur gear efficiency prediction method previously developed by the authors was extended to include power loss of planetary gearsets. A friction coefficient model was developed for MIL-L-7808 oill based on disk machine data. This, combined with the recent capability of predicting losses in spur gears of nonstandard proportions, allows the calculation of power loss for complete aircraft gearboxes that utilize spur gears. The method was applied to the T56/501 turboprop gearbox and compared with measured test data. Bearing losses were calculated with large-scale computer programs. Breakdowns of the gearbox losses point out areas for possible improvement.
Dynamic Stability of the Flexible Connecting Rod of a Slider Crank Mechanism
Authors: Tadjbakhsh Iradj G. , Younis Christos J.
Published: January 2010

The partial differential equation of motion of the flexible connecting rod of a slider crank is derived, under the assumption of small deflections. Application of the Galerkin procedure, leads to a system of linear ordinary differential equations, with respect to the modal coordinates of vibration of the rod. For periodic solutions, the foregoing system reduces to a system of coupled Hill equations. Application of Floquet theory, determines those values of the parameters: speed, input torque, geometry, and material properties that constitute the boundaries between the regions of stability and instability.
Five-Bar Grashof Criteria
Authors: Ting Kwun-Lon
Published: January 2010

In this paper, the five-bar Grashof criterion is proposed and proved. A five-bar linkage is a Class I linkage if lmax + lmin 1 + lmin 1 ≤ m + n is satisfied, otherwise it is a Class II linkage. Depending on the location of the two input links, a Class I linkage may be classified as (1) a triple-crank or a double-crank linkage if its two shortest links are either the input or fixed links; (2) a conditional double-crank or single-crank linkage if its shortest link is the fixed or an input link and the next shortest link is neither the fixed nor an input link; (3) a zero-crank linkage if none of the foregoing conditions is satisfied. A Class II linkage is neither a triple-crank nor a double-crank linkage. However, it may be a conditional double-crank, single-crank or zero-crank linkage. The proposed five-bar mobility criterion includes the four-bar Grashof criterion as a special case.
Linkage Synthesis Using Algebraic Curves
Authors: Blechschmidt J. L. , Uicker J. J.
Published: January 2010

A method to snythesize four-bar linkages using the algebraic curve of the motion of the coupler point on the coupler link of the four-bar linkage is developed. This method is a departure from modern synthesis methods, most of which are based upon Burmester theory. This curve, which is a planar algebraic polynomial in two variables for the four-bar linkage, is a trinodal tricircular sextic (sixth order). These properties are used to determine the coefficients of the curve given a set of points that the coupler point of the coupler link is to pass through. The coefficients of this curve are nonlinear functions of the linkage parameters. The resulting set of nonlinear equations are solved using iterative/optimization techniques for the linkage parameters.
Offset Surface Generation and Contouring in Computer-Aided Design
Authors: Chen Y. J. , Ravani B.
Published: January 2010

Two computational techniques are presented for Computer-Aided Design (CAD) and Machining (CAM) of parametrically defined surfaces. One technique deals with construction of offset surfaces. An algorithm is presented that would allow detection and removal of the closed loop on the offset surface due to its self-intersection. The second computational technique presented deals with contouring of parametric surfaces. The technique presented allows for optimal generation of planar contour lines. The results are applied to Numerical Control (NC) machining of surfaces.
Robot Kinematics—A Compact Analytic Inverse Solution for Velocities
Authors: Hunt K. H.
Published: January 2010

There are, it seems, several notions, widely but not universally accepted, that hamper the full velocity determination of serial robot arms: (a) that certain generally based rules must be rigorously followed to establish a configuration pattern for any particular robot; (b) that, when things get difficult, there is no alternative to numerical methods; (c) that little can be gained from carefully examining the relevance of certain fundamentals of kinematic geometry. The more usual serial arms can, however, be analyzed elegantly, but only when elementary screw theory is recognized as being both essential and ubiquitous. Then, with the aid of the coordinate transformation for screws, the inverse velocity problem can be simply formulated analytically. Certain other matters, such as closure determination and proximity to special configurations, are touched upon.
Development of Knowledge Base for Designing Linkage-Type Dwell Mechanisms: Part 2—Application
Authors: Kota Sridhar , Erdman Arthur G. , Riley Donald R.
Published: January 2010

Knowledge acquisition is a big bottleneck in any expert system development. Several “rules-of-thumb” are developed for designing linkage-type dwell mechanisms. These rules of thumb are based on path curvature theory (Part 1 of this paper) and systematic synthesis, analysis and classification of straight-line, circular-arc and symmetrical coupler-curve generating linkages. The methods of representing the domain-specific knowledge in an expert system are discussed here. “Frames” for structural representation of knowledge and “production rules” to control the reasoning during the design process are proposed here. Frames and rules, in the light of dwell-mechanism synthesis are presented. Finally, a conceptual design example illustrates the various stages that the actual expert system goes through in the design process when these concepts are fully developed and programs are written out in LISP. These concepts are developed with an eye toward future development of a general expert system for type and dimensional synthesis of mechanisms.
Application of Timoshenko Beam Theory to the Dynamics of Flexible Legged Locomotion
Authors: Bakr E. M. , Shabana A. A.
Published: January 2010

A method for the dynamic analysis of flexible legged locomotion systems that accounts for the rotary inertia and shear deformation effects is presented. The motion of the flexible components in the legged vehicle is described using a set of inertia-variant Timoshenko beams that undergo large rotations. A shape function that accounts for the combined effect of rotary inertia and shear is employed to describe the deformation relative to a selected component reference and the rigid-body modes of the shape function are eliminated using a set of reference conditions. Kinetic and strain energies are derived for each Timoshenko beam, thus identifying the beam mass and stiffness matrices which account for the rotary inertia and shear deformation effects. A new set of time-invariant matrices that describe the nonlinear inertia coupling between the reference motion and elastic deformation and account for the rotary inertia and shear is developed and it is shown that the form of these matrices as well as the mass and stiffness matrices are significantly affected by the inclusion of rotary inertia and shear. Numerical experimentations indicate that shear and rotary inertia can have a significant effect on the dynamics of flexible legged locomotion.
The Optimum Kinematic Design of a Planar Three-Degree-of-Freedom Parallel Manipulator
Authors: Gosselin C. , Angeles J.
Published: January 2010

In this paper, the design of a planar three-degree-of-freedom parallel manipulator is considered from a kinematic viewpoint. Four different design criteria are established and used to produce designs having optimum characteristics. These criteria are (a) symmetry (b) the existence of a nonvanishing workspace for every orientation of the gripper (c) the maximization of the global workspace, and (d) the isotropy of the Jacobian of the manipulator. The four associated problems are formulated and their solutions are derived. Two of these require to resort to numerical methods for nonlinear algebraic systems. Results of optimum designs are also included.
Dynamic Analysis of Hybrid Serial Manipulator Systems Containing Parallel Modules
Authors: Sklar M. , Tesar D.
Published: January 2010

Alternatives to serial manipulator design incorporating parallel structure have been suggested in the literature. However, generic dynamic analysis techniques for these novel designs are not available. This paper presents a general method for the dynamic and kinematic analysis of hybrid systems which combine serial links with parallel structured modular devices. All necessary influence coefficients are derived for the general hybrid system. These influence coefficients allow the controlling and kinematic equations to be written such that the geometric parameters and the input dynamics are explicitly separated. A number of parallel modules are presented here. The use of parallel actuation in present industrial manipulators is reviewed.
Synthesis of Planar Mechanisms for Coupler Tangent-Line Envelope Generation: An Alternative to Coupler Point-Path Generation
Authors: Sathyadev Dev P. , Soni A. H.
Published: January 2010

A synthesis procedure is developed to envelope a given plane curve by a tangent line carried by the coupler plane of a planar four-bar linkage. The synthesis procedure is based on a modification of the planar rigid-body displacement matrix developed by Suh [1]. The approach is based on considering a given curve as the envelope of a moving tangent line and synthesizing mechanisms to envelope the given curve. This is a novel approach in mechanism design and adds a new dimension to the path-generation problem of mechanism synthesis. The foregoing procedure is also extended to synthesize eight-link mechanisms to simultaneously coordinate the motion of two tangent lines. In addition to finite position synthesis, both infinitesimal and mixed position synthesis are considered.
On Dynamic Loads in Parallel Shaft Transmissions: Part I—Modelling and Analysis
Authors: Lin H.-H. , Huston R. L. , Coy J. J.
Published: January 2010

A model of a simple parallel-shaft, spur-gear transmission is presented. The model is developed to simulate dynamic loads in power transmissions. Factors affecting these loads are identified. Included are shaft stiffness and inertia, load and power source inertia, tooth geometry, tooth stiffness, local compliance due to contact stress, load sharing, and friction. Governing differential equations are developed and a solution procedure is outlined. A parameter study of the solutions is presented in Part 2.
Determination of Settings of a Tilted Head Cutter for Generation of Hypoid and Spiral Bevel Gears
Authors: Litvin F. L. , Zhang Y. , Lundy M. , Heine C.
Published: January 2010

Kinematics of mechanisms of hypoid and spiral bevel cutting machines is considered. These mechanisms are designated to install the position and tilt of the head cutter. The tilt of the head cutter with standard blades provides the required pressure angle. The authors have developed the matrix presentation of kinematics of these mechanisms and basic equations for the required settings. An example is presented based on the developed computation procedure.
Characteristic Surfaces for Three-Position Function Generation With Planar Four-Bar Mechanisms
Authors: Barker C. R. , Tso P.-L.
Published: January 2010

This paper considers the relationship between the three-position function-generation problem and the solution space for planar four-bar mechanisms. The two infinities of solutions possible are mapped in a plane to determine the locations where particular types of mechanisms occur. It is possible to generate a contour in the mapping plane which joins together all solutions which possess a common characteristic in regard to their link lengths. This same contour can be displayed in the solution space to ascertain the overall characteristics of potential solutions to the design problem. A numerical example is used for illustrative purposes, but the results can be applied to any three-position function-generation problem.
Dimensionless Solution to the Optimal Design of Spur Gear Sets
Authors: Carroll R. K. , Johnson G. E.
Published: January 2010

In some earlier papers (Savage, Coy, and Townsend, 1982; Carroll and Johnson, 1984), the design of spur gear sets based on minimum size has been addressed considering the interaction of bending and contact stress constraints. In this paper, we present a new approach to the spur gear problem. The new method makes use of some newly defined dimensionless parameters. In the resulting design space, the optimal dimensionless design (which defines the optimal tooth geometry) is independent of load and speed requirements of the gear set. However the optimum is dependent on the physical properties of the materials used. We introduce a new quantity called the Material Properties Relationship Factor, CMP. In the problem formulation presented here, we show that the optimum will always be constraint bound and it will occur at one of three possible constraint intersections. CMP is used to identify which of three possible constraint intersections is the correct one. After the dimensionless optimum is found, we present an example which shows how to transform the solution back into the real design space considering the load and speed requirements of the gear set along with discrete value constraints on the number of teeth and the diametral pitch. Tabulated optimal dimensionless designs are included for some standard sets of tooth proportions.
Penalty Formulations for the Dynamic Analysis of Elastic Mechanisms
Authors: Bayo E. , Serna M. A.
Published: January 2010

A series of penalty methods are presented for the dynamic analysis of flexible mechanisms. The proposed methods formulate the equations of motion with respect to a floating frame that follows the rigid body motion of the links. The constraint conditions are not appended to the Lagrange’s equations in the form of algebraic or differential constraints, but inserted in them by means of a penalty formulation, and therefore the number of equations of the system does not increase. Furthermore, the discretization of the equations using the finite element method leads to a system of ordinary differential equations that can be solved using standard numerical algorithms. The proposed methods are valid for three dimensional analysis and can be very easily implemented in existing codes. Furthermore, they can be used to model any type of constraint conditions, either holonomic or nonholonomic, and with any degree of redundancy. A series of mechanisms composed of elastic members are analyzed. The results demonstrate the capabilities of the proposed methods for simulation analysis.
Life Prediction of V-Belts Related to Fatigue Mechanisms
Authors: Fritzson D.
Published: January 2010

Next to gear transmissions, belt transmissions are the most important mechanical transmissions. Today, belt design and development is based on extensive application tests of belts in the product development process. There is a need for theory development and design support systems. This would enable simulation for prediction and optimization of fatigue life. The aim of this work is to study certain parts of the belt in detail when the belt is running under loaded conditions. The areas of special interest are those which can be related to failure mechanisms. Thus the model can be used for calculations to predict service life. Here, the attention is focused on V-belts. Several different failure modes can be identified in V-belt fatigue. Here it is shown that the failure modes thus defined occur for such test conditions that long life can be associated with radial cracks, medium life with separation, and cord break with short life. In order to monitor the stress-strain state at any location in the belt, while simulating a running belt, “the parametric belt segment model” has been developed. Correlation with V-belt fatigue data for 11 different load cases have been made. The conclusion is that both failure mode and fatigue life can be predicted using computer simulations.
Three-Dimensional Balancing of the Stiller-Smith Mechanism for Application to an Eight-Cylinder IC Engine
Authors: Smith J. E. , McKisic A. D. , Craven R. , Prucz J.
Published: January 2010

The Stiller-Smith Mechanism employs a double cross-slider to convert linear reciprocating motion into rotational motion. It has previously been shown that a four-cylinder configuration utilizing this motion conversion device can be balanced in two dimensions. The inherent planar nature of this mechanism makes it possible to produce a compact, eight-cylinder configuration for use as an internal combustion engine which is balanced in three dimensions. This paper develops and presents the necessary requirements for such a balanced engine. Relative merits of various configurations are discussed and analytical results of different balancing schemes are presented.
Allocation of Dimensional Tolerances for Multiple Loop Planar Mechanisms
Authors: Fenton R. G. , Cleghorn W. L. , Fu Jing-fan
Published: January 2010

A method is presented to determine tolerance bands for the dimensions of multiple loop planar mechanisms such that output motions will be kept within specified allowable limits. The kinematic equations of mechanisms are generated by combining various link groups. A preliminary set of estimated tolerance bands is calculated using an analytical technique. An optimization and checking routine is then employed to determine the set of input parameters which satisfies the prescribed output motion requirements. Examples have been included to illustrate the method.
Mobility Criteria of Single-Loop N-Bar Linkages
Authors: Ting Kwun-Lon
Published: January 2010

Single-closed-loop N-bar mobility criteria are presented. These criteria provide a simple and effective method (1) to determine the full rotatability of any single closed-loop linkages, (2) to predict the revolvability between two adjacent links, (3) to explain and identify the existence of singular positions, (4) to classify linkages, and (5) to identify the difference of singular positions between linkages of different types. These criteria are fundamental tools toward a better understanding on the mobility of more complicated linkages.
A Unified Outline of Nonlinear Programming Algorithms
Authors: Schittkowski K.
Published: January 2010

The four most successful approaches for solving the constrained nonlinear programming problem are the penalty, multiplier, sequential quadratic programming, and generalized reduced gradient methods. A general algorithmic frame will be presented, which realizes any of these methods only by specifying a search direction for the variables, a multiplier estimate, and some penalty parameters in each iteration. This approach allows one to illustrate common mathematical features and, on the other hand, serves to explain the different numerical performance results we observe in practice.
A Linkage Design for Direct-Drive Robot Arms
Authors: Asada Haruhiko , Ro Il Hwan
Published: January 2010

A new approach to manipulator link mechanism design is presented. Given torque-speed characterisics of actuators and an arm link mechanism, the resultant force-speed characteristics at the tip of the arm are analyzed. The link mechanism is optimized so that the end point speed and force are within appropriate ranges. This method is applied to a two-degree-of-freedom direct-drive arm. Direct-drive arms, in general, tend to have excessively fast operating ranges, whereas output forces are extremely small. A closed-loop five-bar-link mechanism is applied to the direct-drive arm, and the link dimensions are optimized in order to achieve appropriate force and speed ranges at the arm tip without using reducers.
Load Capacity of a New W-N Gear With Basic Rack of Combined Circular and Involute Profile
Authors: Ariga Y. , Nagata S.
Published: January 2010

A new W-N gear tooth profile is developed. The gear developed has an addendum of circular arc and a dedendum of involute curve. This particular tooth profile is believed to solve the problem of conventional W-N gear profile—that is, the profile is sensitive to center distance variations. No pitting on the gear was observed even after 1 × 107 revolutions cycle during the laboratory test using a pair of gear having specified values of Mn (normal module) = 4, β (helix angle) = 30 deg, and Lloyd’s K factor at 8 MPa.
Spin Analysis of Concentrated Traction Contacts
Authors: Loewenthal S. H.
Published: January 2010

Spin, the result of a mismatch in contact radii on either side of the point of rolling, has a detrimental effect on traction contact performance. It occurs in concentrated contacts having conical or contoured rolling elements, such as those in traction drives or angular contact bearings, and is responsible for an increase in contact heating and power loss. This investigation examines the kinematics of spin-producing contact geometries and the subsequent effect on traction and power loss. The influence of lubricant traction characteristics and contact geometries that minimize spin are also addressed.
Design of Machine-Tools: The Random Response Calculations of Machine Tools Subjected to Stochastic Excitations Using Dynamic Condensation Technique
Authors: Sharan A. M. , Reddy V. R.
Published: January 2010

The response spectral density is an important parameter which should be examined by a machine-tool analyst. A new approach for the calculation of response spectral density for a linear stationary random multi-degree-of-freedom system is presented. This method is based on condensing the system matrices and introducing a set of auxiliary variables. The response spectral density matrix obtained by using this new approach contains the spectral densities and the cross-spectral densities of the master degrees-of-freedom chosen. The new method requires significantly less computation time, as compared to conventional methods, for calculating response spectral densities associated with the selected number of degrees of freedom. To compare the computation time, three numerical examples are presented.
Dynamics of Multibody Systems With Variable Kinematic Structure
Authors: Khulief Y. A. , Shabana A. A.
Published: January 2010

The problem of predicting the dynamic behavior of a general multibody system subject to kinematic structure changes is addressed using a mixed set of Lagrangian coordinates. Changes in the kinematic structure may occur smoothly or accompanied by a change in the system momenta. The finite element method is employed to estimate the modal characteristics of flexible bodies. An automated pieced-interval computational scheme that accounts for the change in the dynamic characteristics due to the imposition of new sets of constraints on the boundaries of flexible components is developed. The resulting change in the deformation modes and the associated change in basis of the configuration space requires a new set of generalized coordinates for each subinterval of the analysis. A numerical example is used to demonstrate the analysis scheme developed in this paper.
A Hybrid Numerical Integration Method for Machine Dynamic Simulation
Authors: Park T. W. , Haug E. J.
Published: January 2010

An efficient and stable method for solving mixed-differential algebraic equations of constrained mechanical system dynamics is presented. The algorithm combines constraint stabilization and generalized coordinate partitioning methods, taking advantage of their attractive speed and error control characteristics, respectively. Three examples are studied to demonstrate efficiency and stability of the method.
A Heat Pump and Thermal Storage System for Solar Heating and Cooling Based on the Reaction of Calcium Chloride and Methanol Vapor
Authors: Offenhartz P. O’D. , Brown F. C. , Mar R. W. , Carling R. W.
Published: January 2010

Thermodynamic, kinetic, heat transfer and mass transfer data are presented on the reaction of CaCl2 and CH3OH vapor to form solid-phase CaCl2•2CH3OH. These data demonstrate the suitability of the reaction for storing solar energy, and for pumping heat, either for use in space heating (at a solar coefficient of performance > 1), air conditioning, or both. CaCl2 reacts with CH3OH to form CaCl2•2CH3OH with an enthalpy and entropy of reaction 51.7 kJ (mole CH3OH)−1 and 126 J deg−1 (mole CH3OH)−1, respectively. Reaction kinetics close to equilibrium are complex, although the reaction is first order when the temperature of the reacting salt is far from equilibrium. Heat transfer through the salt appears to follow the Russel equation, and reaction rates are not limited by mass transfer in a well-designed system. In the heating mode, a solar coefficient of performance (COP) of about 1.6 should be achievable if the entire heat of CH3OH condensation is used; this could permit a substantial reduction in solar collector area for a given amount of heat delivered to the load. In the cooling mode, the COP should be about 0.6. The system should be capable of pumping heat from an ambient source of 0°C to an indoor air duct temperature above 40°C, or from an indoor chiller at 5°C to an outdoor ambient air sink. The required solar collector temperature is below 140°C, and the energy storage density is about 4 × 105 kJ m−3.
Low Cost Solar Selective Chromate Conversion Coatings Applied to Stainless Steel Substrates
Authors: Culham J. R. , Niessen P.
Published: January 2010

Solar selective surfaces have been produced on austenitic and ferritic stainless steels using an acidic chromate bath at 75°C. These surfaces have been shown to have high humidity resistance and good thermal stability. The conversion coatings can be applied uniformly over large surfaces, even surfaces of nonplanar topography. Complete sets of plating parameters for different grades of stainless steels are presented which may be used for the implementation of this process for the production of low grade heat collecting systems.
A Model for the Angular Distribution of Sky Radiance
Authors: Hooper F. C. , Brunger A. P.
Published: January 2010

A flexible mathematical model is introduced which describes the radiance of the dome of the sky under various conditions. This three-component continuous distribution (TCCD) model is compounded by the superposition of three separate terms, isotropic, circumsolar and horizon-brightening factors, each representing the contribution of a distinguishable sky characteristic. In use, a particular sky condition is characterized by the values of the coefficients of each of these three terms, defining the distribution of the total diffuse component. The TCCD model has been demonstrated to fit both the normalized clear sky data and the normalized overcast sky data with an RMS error of about ten percent of the mean overall sky radiance. By extension the model could describe variable or partly clouded sky conditions. The model will permit improvement in the prediction of the total solar radiation incident upon a surface of given tilt and orientation, such as that of a solar collector.
Effectiveness-NTU Charts for Heat Recovery From Latent Heat Storage Units
Authors: Shamsundar N. , Srinivasan R.
Published: January 2010

The shell-and-tube heat-exchanger with a phase change material on the shell side is the subject of many investigations concerning latent heat storage. Many design calculations have been based on formulae that apply to one-dimensional solidification. In these calculations, axial changes in fluid temperature and solidification rate were neglected, and the coolant temperature was assumed constant. In the present paper, these restrictions are removed. It is shown that complete three-dimensional results can be obtained from the numerical results of a two-dimensional analysis by performing simple calculations. The results are presented in the form of charts giving the effectiveness of a heat-exchanger in terms of its size, the layout of the tubes, and the Biot number. The use of the charts in design is illustrated by numerical examples.
Analysis and Design of Efficient Absorbers for Low-Temperature Desiccant Air Conditioners
Authors: Peng C. S. P. , Howell J. R.
Published: January 2010

Desiccant dehumidification and air-conditioning systems require careful design to minimize large parasitic power requirements for pumps and blowers. Each component depends to some extent on overall system characteristics, yet each component must be carefully modeled in itself. The most challenging part of optimizing a system is the absorber design. In order to increase the heat and mass transfer rate while minimizing the pressure loss in the absorber, a direct contact falling film fin-tube heat exchanger is analyzed with water flowing on the tube side and desiccant flowing as a falling film on the fin side. Air is cooled and dehumidified by the water and desiccant as it is circulated through the absorber. A model to analyze the heat and mass transfer in the absorber has been developed. An optimum design has been selected based on not only thermal performance but also practical and economic considerations. Application of the absorber design is then made to design of a complete desiccant system for use with low-temperature heat as an energy source.
Performance Characteristics of a Thermosyphon Solar Domestic Hot Water System
Authors: Young M. F. , Bergquam J. B.
Published: January 2010

Performance characteristics (i.e., system temperatures and mass flow rates) of a thermosyphon solar domestic hot water (SDHW) system that are representative of practical system configurations and sizes are presented. Experimental weather/radiation conditions, collector inlet/outlet temperatures, collector mass flow rates, and storage tank temperature profiles are presented for the same period. These form a consistent set of performance data to which numerical predictions are compared. An indirect method using the storage tank temperatures is used to experimentally determine the thermosyphon mass flow rate. The accuracy of this indirect method is verified by comparison to measurements taken with a turbine flow meter on a pumped SDHW system. System temperatures and mass flow rates are predicted using a general purpose transient SDHW computer program, SHOW (Solar Hot Water). This program contains models for the solar collector, storage tank, and the thermosyphon mass flow rate. The storage tank is modeled as a stratified liquid tank with internode convection and conduction, stored internal energy, heat losses from the tank exterior, and some mixing at the tank inlet/outlet boundaries. Comparisons of predicted collector inlet/outlet temperatures; storage tank temperature profiles, and mass flow rates show agreement with experiments.
An Investigation of Thermal Stratification in Horizontal Storage Tanks
Authors: Young M. F. , Baughn J. W.
Published: January 2010

The thermal behavior of a horizontal storage tank has been investigated numerically and experimentally. The purpose of the present work is to compare a simple, one-dimensional model to the measured temperature stratification in this horizontal tank. For the test conditions used in these experiments, axial temperature gradients were found to be negligible compared to vertical temperature gradients. It was observed that significant mixing of the tank occurred when water was removed unless a diffuser manifold was placed on the makeup water inlet. The numerical model used was one-dimensional (vertical) with some degree of mixing at the inlet and outlet boundaries. The temperatures at the top of the tank were predicted fairly well, but the temperatures at the bottom deviated somewhat from the predictions. It appears that some additional interior mixing, not included in the present model, occurs.
Medicine Bow Wind Project
Authors: Nelson L. L.
Published: January 2010

The Bureau of Reclamation (Bureau) conducted studies for a wind turbine field of 100 MW at a site near Medicine Bow, Wyoming, one of the windiest areas in the United States. The wind turbine system would be electrically interconnected to the existing Federal power grid through the substation at Medicine Bow. Power output from the wind turbines would thus be integrated with the existing hydroelectric system, which serves as the energy storage system. An analysis based on “willingness to pay” was developed. Based on information from the Department of Energy’s Western Area Power Administration (Western), it was assumed that 90 mills per kWh would represent the “willingness to pay” for onpeak power, and 45 mills per kWh for offpeak power. The report concludes that a 100-MW wind field at Medicine Bow has economic and financial feasibility. The Bureau’s construction of the Medicine Bow wind field could demonstrate to the industry the feasibility of wind energy.
A Regional Comparison of Solar, Heat Pump, and Solar-Heat Pump Systems
Authors: Manton B. E. , Mitchell J. W.
Published: January 2010

A comparative study of the thermal and economic performance of the parallel and series solar-heat pump systems, stand-alone solar, and stand-alone heat pump systems for residential space and domestic hot water heating has been undertaken for the United States using FCHART 4.0 [1]. The results are useful for a regional assessment of the viability of the different systems, and for assessing policies that will encourage the implementation of the most energy efficient system. The magnitude of the potential energy savings was determined for each system on the basis of an equal total system cost in the case of the series, parallel, and solar systems. The cost was governed by current federal tax credits, and found to be 10,000 dollars. The size and cost of the heat pump are the same in the series, parallel, and stand-alone heat pump systems. A line can be drawn across the United States north of which the parallel heat pump system saves the most energy, and south of which the solar system saves the most. The better of either the solar or the parallel systems consistently used less energy than either stand-alone heat pump or series systems for all locations. The conventional oil or gas furnace seasonal efficiency which would be required to save as much primary energy as the better alternative system was identified regionally. In all but the northern portions of the United States, conventional furnaces would use more primary energy than the better alternative system. The price that the solar collector in the series heat pump system would have to be so that a larger collection system could be installed and the series system would match the energy savings of the preferred system, whether solar or parallel heat pump, was calculated. This price was one-half to two-thirds of current collector prices. The break-even electricity price was determined which is the price below which the life cycle savings of the alternative system are positive. The better alternative was found to be economic against oil furnaces in all regions of the U.S., but economic against gas furnaces only in the Southwest.
Comparative Productivity of Distillation and Reverse Osmosis Desalination Using Energy From Solar Ponds
Authors: Tleimat B. W. , Howe E. D.
Published: January 2010

This paper presents comparative analyses of two methods for producing desalted water using the heat collected by a solar pond—the first by distillation, and the second by reverse osmosis. The distillation scheme uses a multiple-effect distiller supplied with steam generated in a flash boiler using heat from a solar pond. Solar pond water passes through a heat exchanger in the water system ahead of the flash boiler. The second scheme uses a similar arrangement to generate hydrocarbon vapor which drives a Rankine cycle engine. This engine produces mechanical/electrical power for the RO plant. The analyses use two pond water temperatures—82.2°C (180°F) and 71.1°C (160°F)—which seem to cover the range expected from salt-gradient ponds. In each case, the pond water temperature drops by 5.56°C (10°F) while passing through the vapor generator system. Results of these analyses show that, based on the assumptions made, desalted water could be produced by distillation at productivity rates much greater than those estimated for the RO plant.
Modeling and Analysis of an All-Plastic Flat-Plate Solar Collector
Authors: Russell L. D. , Guven H. M.
Published: January 2010

The concept of an all-plastic liquid flat-plate solar collector was studied. Such a collector eliminates the need for coatings, metals, and all other materials except plastics. The concept appears to offer possibilities for the mass production of a low-cost, lightweight solar collector which is reasonably efficient. Material considerations for the concept are discussed, and thermal analysis is presented. Mathematical models were developed for study of this concept. Convection and nonlinear radiation between the covers was computed in all of the models. In addition absorptance and conduction in the cover(s) and the fluid cover plate were studied in order to determine their effects on the panel performance. A model panel was fabricated, and computer results were compared with test data for the efficiency of the panel.
Natural Convection in Collector Cavities With an Isoflux Absorber Plate
Authors: Schinkel W. M. M. , Hoogendoorn C. J.
Published: January 2010

The boundary condition at the hot absorber plate in a solar collector will influence the natural convection in the enclosure. For the isoflux boundary condition and an isothermal cold wall an experimental and numerical study has been made for Ra numbers from 105 to 107 and inclinations from 20 to 90 deg with the horizontal. For vertical enclosures the heat transfer by natural convection was about 19 percent above that for an isothermal hot plate. This decreases with angle of inclination, to 9 percent at 20 deg. For solar collectors it means that for cases where the absorber plate is not isothermal the convective losses can be about 10 percent above the usually expected values.
Heat Transfer Characteristics of a Back-Corrugated Absorber Surface for Solar Air Collectors
Authors: Shockey K. A. , Pearson J. T. , DeWitt D. P.
Published: January 2010

Current literature on solar air collectors emphasizes satisfactory heat transfer between the absorber and the flowing air as a major factor in overall performance. Heat transfer in the airflow passages, usually in or near the transitional flow range, is also influenced by entrance effects. The present study experimentally examines a back-corrugated absorber-convector composed of a rectangularly corrugated plate attached to the back side of a flat absorber plate with a high-temperature, high-strength adhesive. The upper surface is subjected to a heat flux from a blanket-type electric heater which simulates solar irradiation. The corrugated-plate configuration creates two parallel airflow channel types. The two channels have different geometries and, therefore, may have different heat transfer characteristics. An apparatus was designed to determine the local convective heat transfer coefficients along each of the channels. The results show that the back-corrugated absorber-convector has much better thermal performance than the simple flat-plate absorber-convector, primarily because of the increased convective heat transfer area.
Vapor/Droplet Coupling and the Mist Flow (OTEC) Cycle
Authors: Lee C. K. B. , Ridgway S. L.
Published: January 2010

The present experiments have demonstrated that water droplets (∼200-μm dia) can be lifted to substantial heights (∼50 m) by their own vapor produced in flashing over temperature differences typical of the tropical seas. The coupling between the vapor and droplets is found to be excellent. The efficiency for momentum coupling is over 90 percent, and that for energy coupling is shown to vary inversely with the slip ratio. For the conditions in the present experiments, it varies from 50 to 80 percent. The momentum transfer is correlated with an interaction parameter which is the product of the liquid fraction, the slip, and the amount of flashing. For the high vapor flow cases, the pressure difference across the lift column is found to be proportional to the interaction parameter. The relevance of the two-phase flow to a class of open-cycle ocean thermal energy conversion (OTEC) schemes is considered, and the implications of the observed strong vapor/droplet coupling to the feasibility of the mist-flow OTEC cycle are discussed.
Blade Configurations and Performance of the Savonius Rotor With Application to an Irrigation System in Indonesia
Authors: Modi V. J. , Roth N. J. , Pittalwala A.
Published: January 2010

This paper describes results of a systematic wind tunnel study aimed at development of the wind-operated irrigation system suitable for meeting needs of small farms in Indonesia. Using several models of the single-stage Savonius configuration, influence of the blade gapsize and overlap on the output is assessed and their favourable combination established for a given blade geometry. This is followed by the performance data on a larger, self-starting, two-stage model operating in conjunction with several different pumps. Results suggest that the two-stage configuration with a projected blade area of 1.12 m2 is capable of delivering 250 L/hr to a head of 4 m at a windspeed of around 16 km/hr using a gear pump. The performance appears quite promising, and a prototype is being designed to meet the objective. A preliminary study aimed at load matching through the generator field control is in progress.
Performance of Cross-Cooled Desiccant Dehumidifiers
Authors: Mei V. C. , Lavan Z.
Published: January 2010

A cross-cooled silica gel desiccant dehumidifier model was designed, built, and tested. The performance of the unit was studied as a function of the inlet process stream dew point, process stream and cooling stream flow rates, and regeneration stream temperature and dew point. The tests were also simulated by a computer program and were compared to the experimental results.
Force Reduction by Motion Design in Spring-Loaded Cam Mechanisms
Authors: Johnson R. C.
Published: January 2010

A strategy of motion synthesis is developed for reducing critical forces in relatively rigid high-speed spring-loaded cam mechanisms. A special motion is specifically presented to illustrate application of the developed strategy, for the dwell-rise-dwell displacement case. Critical force graphs are presented for a numerical industrial probelm in three examples, comparing the developed special motion with the commonly used cycloidal and modified trapezoidal motions. Maximum values of cam contact force, inertia force, and spring force are all appreciably reduced by the special motion.
Pivoted Brake-Shoe Force Analysis
Authors: Offner D.
Published: January 2010

Based on operating features that rigid and pivoted brake shoes have in common, a method is presented for aiding in the force analysis of pivoted brake-shoe systems. The method uses moment equilibrium about the shoe pivot for deriving an equation for locating the line of action of the resultant forces representing the effect of interface normal pressures and traction stresses. It is developed and illustrated in the context of a typical problem. This method of force analysis should provide a useful supplement to design texts in which only qualitative discussion of pivoted brake shoe systems is given.