Unique Experimental Method Research Articles

Single-Coil Twin-Fan Air-Conditioning and Air-Distribution System—Toward Development of a Mathematical Model of the Compartmented Coil

A new air-conditioning and air-distribution system, called the single-coil twin-fan system, that provides both energy efficiency and good indoor air quality was developed. It employs a unique compartmented cooling and dehumidifying coil that is fundamental in realizing the significant benefits of the system by being able to treat the outdoor air and the recirculated airstreams separately. In view of the distinctly different features of the compartmented coil, the performance prediction of such coils would have to be approached from first principles, which involves the determination of the fundamental heat and mass transfer coefficients. This paper establishes the need for a new mathematical model for the compartmented coil, outlines the underlying assumptions of classical models, and describes the formulation of an improved model. It presents a unique experimental method for determining the complex fin surface temperatures that constitute the major enhancements to the model development. Finally, the newly developed mathematical model is validated with experimental results.

Experiments with stored exotic nuclei at relativistic energies

A review and recent progress are presented from experiments on masses and lifetimes of bare and few-electron exotic nuclei at GSI. Relativistic rare isotopes produced via projectile fragmentation and fission were separated in flight by the fragment separator FRS and injected into the storage ring ESR. This worldwide unique experimental method gives access to all fragments with half-lives down to the microsecond range. The great research potential is demonstrated by the discovery of new isotopes along with simultaneous mass and lifetime measurements. Single particle decay measurements and the continuous recording of both stored mother and daughter nuclei open up a new era for nuclear spectroscopy. The study of bare and few-electron nuclei has also important astrophysical relevance with respect to the hot stellar conditions where reactions and decay are influenced by the degree of atomic ionization. The future international NUSTAR facility at FAIR consisting of a new large-acceptance in-flight separator (Super-FRS) and a dedicated storage ring system (CR–RESR–NESR) will be an ideal tool to study nuclei with new probes and to investigate the majority of relevant r- and rp-process nuclei which are not in reach with the present-day facilities.

Pulsed-Flow Microcalorimetric Study of the Template-Monolayer Region of Nonionic Surfactants Adsorbed at the Graphite/Water Interface

The formation of half-cylindrical surfactant aggregates at the graphite/aqueous solution interface is templated by an ordered monolayer of molecules disposed parallel to the graphite basal plane. Beyond a critical alkyl chain length, monolayer formation is effectively irreversible. Since enthalpic interactions in this template-monolayer region cannot be resolved with adequate accuracy by the traditional adsorption calorimetric methods, we applied a novel method, pulsed-flow calorimetry, for simultaneous measurement of the material balance and the enthalpy balance in this high-affinity region. For the three nonionic surfactants studied, n-octyl beta-D-glucoside (C(8)G(1)), dimethyl-n-decylamine oxide (C(10)DAO), and n-octyl tetraethylene glycol monoether (C(8)E(4)), the adsorption was found to be strongly exothermic and effectively irreversible at low adsorbate densities, and the differential heat of adsorption markedly decreased with increasing surface coverage in this region. This deviation from the ideal adsorption behavior was attributed to intermolecular interactions within the adsorption layer rather than to surface heterogeneity of the graphite basal planes. A thermodynamic consistency test clearly demonstrated that pulsed-flow calorimetry is a unique experimental method for the study of nonreversible adsorption phenomena at solid/solution interfaces, representing an excellent tool to complement traditional methods, e.g., frontal-flow and titration adsorption calorimetry. Studies by the frontal-flow method revealed that aggregation on top of the surfactant monolayer was endothermic and reversible.

Experimental Study of Aerodynamic and Structural Damping in a Full-Scale Rotating Turbine

Damping in turbomachinery blades has been an important parameter in the study of forced response and high-cycle fatigue, but because of its complexity the sources and physical nature of damping are still not fully understood. This is partly due to the lack of published experimental data and supporting analysis of real rotating components. This paper presents the results of a unique experimental method and data analysis study of multiple damping sources seen in actual turbine components operating at engine conditions. The contributions of both aerodynamic and structural damping for several different blade vibration modes, including bending and torsion, were determined. Results of the experiments indicated that aerodynamic damping was a large component of the total damping for all modes. A study of structural damping as a function of rotational speed was also included to show the effect of friction damping at the blade and disk attachment interface. To the best of the authors’ knowledge, the present paper is the first report of independent and simultaneous structural and aerodynamic damping measurement under engine-level rotational speeds.

A unique experimental method for monitoring aggregate settlement in concrete

A unique experimental method for monitoring the settlement of aggregate in fresh concrete is introduced and demonstrated. Using nuclear medicine techniques, real-time images of aggregate settlement due to vibration are obtained. These images are used to study the rheological properties of the vibrated concrete mix. The technique developed allows the experimental verification of a number of assumptions regarding the rheology of fresh concrete and the implications of the accepted rheological model of fresh concrete. Additionally, the effects of vibration on aggregate settlement are clearly shown, including effects resulting from the location of the vibrator and the size and density of the aggregate.

Influence of Mortar Rheology on Aggregate Settlement

This study examined the influence of the rheology of fresh concrete on the settlement of aggregate. Fresh concrete exhibits a yield stress that, under certain conditions, prevents the settlement of coarse aggregate, although its density is larger than that of the suspending mortar. Calculations, based on estimates of the yield stress obtained from slump tests, predict that aggregate normally used in concrete should not sink. To test this prediction, the settlement of a stone in fresh mortar is monitored. The stone does not sink in the undisturbed mortar (which has a high yield stress), but sinks when the mortar is vibrated, presumably because of a large reduction in its yield stress. This implies that during placement of concrete, the aggregate settles only while the concrete is being vibrated. A unique experimental method for measuring aggregate settlement is also introduced and demonstrated.

Vapor fraction measurements in a steam–water tube at up to 15 bar using neutron radiography techniques

Real-time neutron radiography has been used to study the dynamic behavior of two-phase flow and measure the time averaged vapor fraction in a heated metal tube containing boiling steam–water operating at up to 15 bar pressure. The neutron radiographic technique is non-intrusive and requires no special transparent window region. This is the first time this technique has been used in an electrically heated pressurized flow loop. This unique experimental method offers the opportunity to observe and record on videotape, flow patterns and transient behavior of two-phase flow inside opaque containers without disturbing the environment. In this study the test sections consisted of stainless steel tubes with a 1.27 cm outer diameter and wall thicknesses of 0.084 and 0.124 cm. The experiments were carried out at the Pennsylvania State University 1 MW TRIGA reactor facility utilizing a Precise Optics neutron radiography camera. The inlet water temperature to the test section was varied between 120°C and 170°C and the flow rate set to 2.3 l/min. T sat is 200°C at these conditions. The tube was resistively heated by passing high currents (∼1000 A) through the stainless steel wall. Scattering due to water in the ∼1 cm tube is significant and Monte Carlo calculations simulating the experiment were made to correct for this effect on the vapor fraction measurement. Details of the experimental technique, methods for analyzing the data and the results of the experiments are discussed.

Experimental analysis of intermaterial surfaces in the study of gaseous mixing characteristics

A unique experimental method for analysing mass transfer between gaseous flows has been presented. It consists of the measurement of Lagrangian quantities, linked to intermaterial surfaces evolution generated by means of a pulsed smoke wire technique. Stretch intensity, stretch rate, mixing-layer thickness, separation distance between neighbouring segments of the interface, for a purposely designed prototypical quasi-two-dimensional flow configuration, have been measured against time and presented in terms of their statistical distribution and averages. A peculiar regime named ‘isolated mixing-layer regime’ has been identified by means of comparison of the mixing-layer thickness with the interface separation distance. Further, the direct experimental evaluation of the stretch rate of the intermaterial surface allows the evaluation of the role of the kinematics on reactive mixing-layers, in particular in the case of the stretched diffusion flame.

Experimental identification of mixing regimes in the analysis of turbulent diffusion flames

A statistical criterion for the classification of gaseous mixing regimes is presented. It is based on the evaluation of two quantities: the mixing layer thickness and the separation distance between two neighboring interface segments, which are preliminarily defined in a specific section along with other quantities (stretch ratio and stretch rate) relevant to the mixing analysis. A unique experimental method for a lagrangian measure of the aforementioned quantities as a function of the residence time is described. Measurements use a two-dimensional laser light scattering technique in a two-dimensional, transitional, isothermal flow which can be considered a prototypical condition of mixing. The probability density function of the stretch rate as well as average values of stretch ratio, mixing layer thickness and interface separation distance are also reported. The last two quantities are used in the determination of a single parameter named “saturation factor” ( C sat), that allows the identification of three regimes: (a) “Isolated mixing layer regime” ( C sat = 1) in which both the mixing and oxidative reactions occur in the neighborhood of the interface. This is a well recognized regime, to which many studies on the characterization of one-dimensional time-dependent stretched diffusion flames refer. (b) “Interacting mixing layer regime” (10 −2 < C sat < 1) in which the diffusion still occurs in the whole flow field, but more sophisticated models than those relative to the previous regime are needed for its characterization. (c) “Saturated mixing layer regime” ( C sat < 10 −2) in which the mixing process is no longer related to the intermaterial surface in its wholeness, but only to that part for which it is still far from other segments of the interface.

Effective thermionic work function measurements of zirconium carbide using a computer‐processed image of a thermionic projection microscope pattern

We report on a unique experimental method to determine thermionic work functions of major crystal planes of single crystal zirconium carbide. Applications for transition metal carbides could include cathodes for advanced thermionic energy conversion, radiation immune microcircuitry, β‐SiC substrates or high current density field emission cathodes. The primary emphasis of this paper is the analytical method used, that of computer processing a digitized image. ZrC single crystal specimens were prepared by floating zone arc refinement from sintered stock, yielding an average bulk stoichiometry of C/Zr=0.92. A 0.075 cm hemispherical cathode was prepared and mounted in a thermionic projection microscope (TPM) tube. The imaged patterns of thermally emitted electrons taken at various extraction voltages were digitized and computer analyzed to yield currents and corresponding emitting areas for major crystallographic planes. These data were taken at pyrometrically measured temperatures in the range 1700<T<2200 K. Schottky plots were then used to determine effective thermionic work functions as a function of crystallographic direction and temperature. Work function ordering for various crystal planes is reported through the TPM image processing method. Comparisons are made with effective thermionic and absolute (FERP) work function methods. To support the TPM image processing method, clean tungsten surfaces were examined and results are listed with accepted values.

Flow dynamic nuclear polarization, a novel method for enhancing NMR signals in flowing fluids

Experimental flow dynamic nuclear polarization (DNP) 1H NMR data are presented. The advantages of flow DNP in comparison with the more conventional static DNP experiments are discussed. The results suggest that flow DNP provides a unique experimental method of independent optimization of the “EPR” and ”NMR” portions of the DNP experiment. Potential applications are also discussed.

Optical Spectral Radiometric/Laser Reflectance Method For Noninvasive Measurement Of Weld Pool Surface Temperatures

A unique experimental method has been developed for measuring weld pool surface temperatures. An equation for determining temperature was developed based on Planck's blackbody spectral distribution of emissive power, the definition of spectral directional emissivity, Lambert's cosine law for diffuse emitters, and Kirchhoff's law for spectral directional reflectivity. The necessary measurements are the spectral directional emissive power and the spectral directional emissivity of the weld pool surface. Detailed pool surface temperature measurements were made of gas tungsten arc (GTA) welding of 1.5mm thick stainless steel (SS) 304 plates using an argon cover gas. Because argon plasma arc spectroscopy measurements over molten SS 304 revealed insufficient emission gaps, the spectral emissive power was measured by high speed film radiometry as the arc was shut off so as to obtain information at the instant the obscuring arc emissions disappear. Similar measurements were made of the spectral directional reflectivity (and thus the spectral directional emissivity) by reflecting a focused laser beam off the weld pool. Detailed weld pool surface temperature maps were generated.

Space-Charge Waves on Plasma Columns in a Weak Magnetic Field

Effects of the thermal motion on the space-charge waves propagating along plasma columns in a weak magnetic field is measured by using a unique experimental method. Good agreement is obtained between the experiment and the theory.

Longitudinal and lateral dispersion in an isotropic porous medium

Coefficients of longitudinal and lateral dispersion were measured for steady uniform laminar flow through an isotropic porous medium. A unique experimental method for measuring lateral dispersion is described. It is found that the ratio of the coefficient of longitudinal dispersion D1 to the coefficient of lateral dispersion D2 is given by where λ and n are dimensionless coefficients dependent upon the pore-system geometry, and [real ] is the Reynolds number based on the seepage velocity, the average grain diameter, and the kinematic viscosity.