Elliptical Insertion Research Articles

Experimental Assessment of Thermal Performance and Fluid Flow Characteristics of Perforated Hollow Elliptical Insert in a Tube Heat Exchanger

Experimental Assessment of Thermal Performance and Fluid Flow Characteristics of Perforated Hollow Elliptical Insert in a Tube Heat Exchanger

Performance of parabolic trough collector having rotating receiver: Effect of elliptical insert and hybrid nanofluid

This study considers three parabolic trough collector models with rotating receiver tubes and elliptical inserts of two orientations and one with a smooth receiver tube. Hybrid nanofluid is considered as a working medium by mixing copper oxide and aluminum oxide nanoparticles in water. Computational experiments are performed with a 1% concentration in terms of vol. of hybrid nanofluids by considering a mixture of copper oxide and aluminum oxide nanoparticles in water (aluminum oxide 25%- copper oxide 75%, aluminum oxide 50%- copper oxide 50%, and aluminum oxide 75%- copper oxide 25%). Rate of flow for the simulation is considered to vary from 0.016 to 0.033 kg/s. Again, this study focuses on utilizing rotating receiver tubes with a varying velocity of 0-15 rad/s to overcome the stratification of high temperature at the surface. Results show that enhanced values for the temperature at outlet, heat transfer coefficient, and thermal efficiency are noted for a model with elliptical inserts of major diameter 28 mm (longitudinal orientation) at 15 rad/s receivers speed for nanofluid-1 (aluminum oxide 75%- copper oxide 25%) at 0.033 kg/s. The highest increment in heat transfer coefficient, as well as thermal efficiency for the model with a 28 mm major diameter elliptical insert (longitudinal orientation), is 44.21% and 29.21% respectively. Highlights Use of a spinning receiver reduces the problem of uneven temperature distribution at receiver surface. Maximum 375 K outlet temperature is noted at 15 rad/s for elliptical insert of diameter 28 mm (longitudinal orientation) at 0.016 kg/s. The elliptical insert received the maximum thermal efficiency rating of 82.03%. An elliptical insert in receiver increases pump work by 18.13% than smooth receiver.

Augmentation of thermal performance of heat exchanger using elliptical and circular insert with vertical twisted tape

ABSTRACT Present work deals with the experimental and computational investigation of thermal properties and fluid flow characteristics on circular tube with elliptical inserts. The major axis is taken equal to hydraulic diameter i.e. 6.81cm. A new parameter, height ratio (γ = b/D) has been defined with three values – 0.45, 0.66, and 0.74. The test section is 1.5 m long which is provided with a constant heat flux of 1000 W/m2 along with air as working fluid at Reynolds number ranging from 3,000 to 21,000. The results show that the augmentation in heat transfer was six times for case γ = 0.74 and the maximum thermal performance factor (TPF) obtained is 2.43 for insert with γ = 0.45 at Re = 3000 over the smooth tube. Computational fluid dynamics (CFD) investigation is also carried out for elliptical inserts, and the results are in good agreement with the experimental results where the maximum deviations in Nusselt number, friction factor, and TPF are ±9.39, ±8.68, and ±8.58%, respectively. CFD investigation for tube having circular inserts with vertical twisted tapes (CVTT) and elliptical inserts with vertical twisted tapes (EVTT) is also presented where the augmentation in heat transfer ranges 3–8 times for CVTT placed in full length and TPF is ranging 1.19–2.63 times for CVTT placed in TL length over to smooth tube.

Consideration of residual stress fields in stiffening ribs welding

The article gives information on the technique for determining the fields of residual welding stresses in the area of the welded stiffening rib. The rib is modeled by an elliptical insert. Methods of the mathematical theory of elasticity, in particular, complex potentials, are used. It is assumed that in the plate, in the absence of a reinforcing rib, a homogeneous stress state is created. The rib welding induces perturbation of the homogeneous stress field. The boundary condition on the reinforcing rib, corresponding to the absence of displacements on its boundary, can be written with complex potentials. An example of a decrease in the stress concentration factor in a plate with a circular hole under conditions of uniform tensile during the welding of the rectilinear stiffening rib is given.

Trade space visualization applied to Lambert׳s Problem for elliptical insertion orbits

This paper investigates the solution of Lambert׳s Problem for targets in elliptical orbits. A mission design software framework to determine the optimal interplanetary trajectory and final capture orbit based on mission constraints and requirements between a departure and arrival body has been developed. Integration of a trade space visualization tool, such as the Applied Research Laboratory Trade Space Visualizer software permits a mission designer to visually inspect the multi-dimensional trade space and investigate regions of feasible trajectories. This analysis process can provide a mission designer with the capability to reduce the amount of time needed to design interplanetary trajectories by reducing the number of feasible solutions that would need to be investigated.

Acoustic concentration of particles in piezoelectric tubes: Theoretical modeling of the effect of cavity shape and symmetry breaking

A new class of simple, highly efficient, cylindrical acoustic concentration devices has been developed based upon cylindrical (or near cylindrical) geometries [Kaduchak et al., Rev. Sci. Instrum. 73, 1332–1336 (2002)] for aerosol concentration applications. The concentrators are constructed from single PZT tubes driven at or near the breathing mode resonance. Acoustic concentration of aerosols is performed within the tube cavity. It has been found that slight modifications to the cylindrical cavity geometry can significantly increase the collection efficiency and assist in precise particle positioning. This paper analyzes the theoretical framework for the acoustic concentration of particles in these devices for various geometrical perturbations. The cavity geometries studied are (1) hollow cylindrical piezoelectric tube, (2) hollow piezoelectric tube with an inner concentric solid cylinder insert, (3) a hollow piezoelectric tube with a concentric elliptic insert which breaks the circular-cylindrical symmetry, and (4) a hollow elliptic cylindrical piezoelectric tube. It is shown that breaking the circular symmetry within the cavity localizes the particles in small spatial regions within the cavity. This localization of particles may be very useful in applications requiring aerosol collection or particle stream positioning.

A beamline for time resolved photoelectron microscopy on magnetic materials at the Swiss light source

We describe the “Surface/Interface: Microscopy” beamline currently under construction at the Paul Scherrer Institut. This beamline will use a photoemission electron microscope to study the electronic and magnetic structure of materials. Its photon energy range will be 94–2000 eV. To allow time resolved measurements with millisecond resolution we use a new scheme allowing to switch the photon helicity optically without perturbing the electron orbit. Two identical elliptical insertion devices are placed behind each other in the same straight section. They can produce light with opposing helicities. These two sources are separated horizontally by introducing a small static parallel offset in the electron orbit. Switching between the two rays of opposite helicities is done mechanically at the horizontal focus behind the monochromator. The two sources are brought to overlap on the sample by slightly defocussing the refocussing mirror. A commercial microscope ( Δx∼20 nm resolution) is adapted to the synchrotron by various upgrades. These include a software combining microscope and beamline control, a computer controlled mechanical alignment system, a separate sample preparation chamber, and sample cooling using liquid nitrogen. The beamline will be available for user operation in 2002.

Line singularity inside an elliptic inhomogeneity

The problem of an elliptic insert with a point of elastic singularity and a perfectly adhering interface is solved using the complex variable method. In particular, it is found that the remote field is insensitive to the inhomogeneity shape and interface status. Unified formulae for the special cases of free elliptic disk and rigid matrix are written and discussed. A closed-form solution for an arbitrary line singularity inside a circular inhomogeneity is also derived as a special case.

Effects of an inhomogeneous elliptic insert on the elastic field of an edge dislocation

The problem of an edge dislocation in the vicinity of an elliptical inhomogeneity is solved analytically in the form of infinite series. The inhomogeneous inclusion is assumed to be either perfectly bonded or sliding along the interface with the surrounding matrix. The problem is formulated in terms of Papkovich-Neuber displacement potentials and the results for the perfectly bonded and sliding interface are compared. The effects of the inclusion/matrix shear moduli ratio, inclusion/dislocation relative distance and inclusion aspects ratio on the interface stresses and the dislocation force are evaluated.

Torsion of a Rigid Smooth Elliptic Insert in an Infinite Elastic Plane

A solution is presented for the non-Hertzian contact stress problem developed during torsion of a smooth rigid elliptic insert in an infinite, linearly elastic plane. The problem is reduced to a singular integro-differential equation which is solved numerically. Results are presented for the contact zones, and for the normal and tangential stresses at the plane-insert interface. The contact region is independent of the magnitude of the applied moment, but depends strongly on the shape of the ellipse, and is weakly dependent on Poisson’s ratio of the plane. Results are also given for the reduction in torsional stiffness between a fully bonded insert and the present solution, (i.e., a completely failed bond).

Torsion of a shaft with a hard elliptical insert

Torsion of a shaft with a hard elliptical insert

Note on rotating disc with an eccentric elliptic insert

Note on rotating disc with an eccentric elliptic insert

Approximate Determination of Contact Stresses in an Infinite Plate Containing a Smooth Rigid Elliptic Insert

Approximate Determination of Contact Stresses in an Infinite Plate Containing a Smooth Rigid Elliptic Insert

Elastic Stresses in Single Mitred Bends

Experimental results are presented for the stresses caused by internal pressure in thin pipes which are mitred and welded together to form a single mitred bend without any type of elliptical insert at the intersection. The frozen-stress photoelastic technique is used, the models being carefully machined and cemented to form a joint free from welding imperfections. The results are compared with the theoretical analysis for small-angle mitred bends, of Green and Emmerson (I)†. An alternative derivation of this theory is given in Appendix I. Good agreement with the theory is shown for small-angle bends for each of the two thicknesses of pipe used. For larger angles of bend, the agreement is less good. The results of a test carried out on a mitred joint subjected to an in-plane bending moment, are included.

Application of the Point-Matching Method to Shallow-Spherical-Shell Theory

Using Reissner’s [1] theory of the bending of shallow spherical shells, two unsymmetrical problems are investigated by the method of point-matching. The first is a uniformly loaded spherical shell clamped on a square base, numerical values of the moments and membrane forces being obtained and compared with the corresponding values for the case of a clamped circular base. The second problem is a spherical shell with a rigid elliptical insert, the latter carrying a central radial load. This gives information concerning the problem of a spherical shell which is pierced at an angle by a relatively rigid circular pipe.