Effects Of Different Cross Sections Research Articles

Effects of different cross-sections of Body Centered Cubic cells on pressure drop and heat transfer of additively manufactured heat sinks

In many industrial applications, heat loads management requires the design and production of compact heat exchangers which are expected to handle high thermal loads with acceptable pressure losses, while assuring good mechanical performances. These challenging targets can be achieved by filling the cavities where the cool/hot fluid circulates with lattice structures promoting the heat exchange between the fluid and the cavity boundaries. Such lattice structures can be only produced through Additive Manufacturing due to their high geometric complexity. Recent experimental investigations proved the effectiveness of some kinds of lattice structures having a circular cross section. Here the aerothermal behaviour of Body-Centred Cubic (BCC) lattice stagger arrays in a rectangular channel was experimentally investigated by considerably extending the previous studies to higher Reynolds numbers (up to 30′000) and to new types of lattice structures. Specifically, three new BCC structures having a cam-like, drop-like and elliptical cross section were explored in this work and compared against those having circular cross section. All the samples were manufactured by means of Laser Powder Bed Fusion and made from AlSi10Mg. At first, the heat exchangers were comprehensively characterized by means of optical non-destructive methods. Successively they were tested in a dedicated rig by imposing constant heat flux boundary conditions. The characteristics of the transitional or fully turbulent approaching flow to the test section are also reported thanks to dedicated flow field measurements performed by Particle Image Velocimetry. According to the obtained results, the BCC structure with the circular cross section of larger diameter is the most effective in terms of heat transfer, although it is largely penalized by the pressure losses. Similar heat transfer performances were achieved by the tapered cross section of elliptical shape with the advantage of a considerably lower friction factor. Pressure losses resulted almost identical for all the tapered cross sections but lower than those of the circular one having an equal frontal dimension. When considering the thermal performance factor the circular shape becomes unfavourable for Re>20′000, while the elliptical cross section is the best choice to efficiently promote heat transfer up to Re=30′000.

Effect of different cross-sections and concrete types on the flexural behavior of CFSTs

The main goal of this research is to experimentally investigate the flexural response of concrete filled steel tubes (CFSTs) considering different cross-sections and concrete types. For this purpose, a total of 12 circular and 8 rectangular CFST beams with different Diameter (depth)-to-thickness ratios were cast using normal and recycled aggregate concrete mixes and were tested under four-point bending. Concrete compressive strengths of 30 and 50 MPa and recycled aggregate (RA) replacement percentages of 50 and 100% were used in the experimental investigation. The test results revealed promising outcomes on the feasibility of using RA in CFST systems under flexure. The flexural behavior of RACFSTs was found to be very similar to NACFSTs, and the change in the concrete compressive strength and RA percentages slightly affected the flexural behavior of RACFSTs. In addition, the experimental flexural capacity of RACFST beams were compared to the theoretical nominal moments predicted by well-known design codes and methods. The Architectural Institute of Japan design code was the most accurate to predict the flexural capacity of RACFSTs with an average of 5% difference only, while the British Standard significantly underestimated the flexural capacity of the tested RACFST beams by an average of 34%.

Numerical investigation and design rules for flexural capacities of H-section high-strength steel beams with and without web openings

This paper presents a finite-element (FE) investigation on the flexural capacities of H-section high-strength steel beams with web openings. A non-linear finite-element model (FEM) was developed for H-section high-strength steel beams with web openings, which included initial geometric imperfections. The FEMs were validated against the test results available in the literature for H-section high-strength steel beams with web openings. The validated FEMs were then used to conduct a parametric study comprising 180 FEMs to investigate the effects of different cross-sections, the opening diameter, the number of opening and the type of loadings on flexural capacities of H-section high-strength steel beams. The flexural capacities predicted from the finite-element analysis (FEA) were also used to study the performance of the current design guidelines for steel structures. A comparison of numerical strengths and design strengths found that the American National Standard (AISC) is over-conservative by as much as 61%, whereas the North American Specification (NAS) and Chinese Code (CC) are conservative by 34% on average, when predicting the flexural capacities of H-section high-strength steel beams with web openings. In addition, the Steel Design Guide Series 2 (SDGS-2) and Continuous Strength Method (CSM) for cold-formed steel (CFS) members with openings are generally appropriate for H-section high-strength steel beams with web openings subjected to flexural failure. Moreover, the design rules from Direct Strength Method (DSM) were found to be over-conservative by around 40%. Accordingly, this paper proposes modified design equations over the existing design rules of SDGS-2. The proposed design equations have predicted closely the flexural capacities of H-section high-strength steel beams with web openings, being only 1% conservative to the FEA strengths.

Dynamic behavior of conveying-fluid pipes with variable wall thickness through circumferential and axial directions

In addition to the traditional hollow circular sections used in marine structures, other hollow sections have attracted the attention of architects and design engineers due to their mechanical characteristics such as torsional rigidity and local strength against impact loading. The purpose of this study is to investigate dynamic response of pipes conveying fluid with variable wall thickness through both circumferential and axial directions. Pipes with variable wall thickness have different flexural rigidities about two different principal axes. This property allows these pipes to be oriented efficiently, meet various design requirements and resist the applied loads. The results of this investigation provide a better insight into the physics and dynamic behavior of non-circular pipes conveying fluid. Two different geometries are studied, (i) the pipe is assumed with a general non-circular cross section with variable wall thickness along the circumferential direction, (ii) both inner and outer boundaries of the pipe cross section are assumed to be circles whereas the wall thickness of the pipe along axial direction is varied with a specified function. The governing differential equations of the problem are derived using Timoshenko beam theory with the effect of shear deformation included in the formulation. The discretization of the problem domain is done using the finite element method. Consequently, a modal analysis is employed to calculate the critical flow velocities of the pipe with clamped-clamped end conditions. The effects of different cross sections on the critical flow velocity are investigated. The importance of Coriolis forces on the presence of coupled-mode flutter and re-stabilization point are also discussed for different values of mass ratio.

Numerical analysis of a microfluidic mixer and the effects of different cross-sections and various input angles on its mixing performance

Micromixers have better efficiency in terms of both the time-scale of chemical kinetics and diffusive transport compared to the conventional macro-mixers. The mixing efficiency in micromixers is an important performance indicator in mixers. This paper presents a numerical study of how the design of a micromixer along with the design of the mixing process affects the mixing efficiency. Specifically, two different types of cross-sections of the channel in micromixers, namely circular and rectangular cross-sections, together with the inlet angle of the channel, were studied. The process parameters, such as the inlet velocity of fluids and diffusion coefficient, were studied as well. The result shows that the circular cross-section can sustain a large pressure difference without undergoing any remarkable distortion and deformation, and it can achieve better performance. The result further indicates that the inlet velocity and diffusion coefficient have significant effects on mixing efficiency; specifically, the low inlet velocity and high diffusion coefficient value can lead to a better mixing performance. However, different input angles alone could not make the mixing efficiency change noticeably. In other words, the mixing performance of such micromixers relies more on the inlet velocity and diffusion coefficient than on the fluid flow angle in the inlet.

Designing and CFD Analysis of Table Top Refrigerator Hexagonal Coil Crossection

In the Present study CFD analysis has been performed on evaporator unit. Tabletop refrigerators are the common house hold unit used in almost all houses. Evaporator and Condenser unit is the main functioning unit of refrigerator system used for the cooling applications. With the increase of modernization use of refrigerator system has rapidly increases due to the reason a lot of researches are prevailing on refrigerator systems. With the updating in technologies almost all the refrigerators require performing with high efficiency and low power consumption. Most researches are going on to increase the heat transfer and heat dissipation in refrigerator systems. In the current study a table refrigerator is selected for the study purpose where effects of different cross sections of evaporator coil has been studied. In the design portion some changes have been made in the material of heating plate to have high transfer of heat from plate to evaporator coil. For the complete study CATIA V5 is used for the modelling purpose and Ansys Fluent is used for the CFD analysis Procedure where hexagonal cross section of evaporator coil shows the most efficient results.

The effects of different cross sections on the hydrodynamic behaviour of sandglass-type FPSOs exposed to regular waves

This paper presents a numerical investigation on the hydrodynamic performance of sandglass-type FPSOs with four different cross sections. In order to estimate the hydrodynamic performance and utilise the results in the design stage of FPSOs, a frequency-domain numerical simulation program, ANSYS/AQWA software package, has been used. Numerical results were compared with experimental data and good agreement has been achieved in small amplitude regular wave cases. Based on the simulation results, it is concluded that polyhedral cross sections (especially 10-sided cross section) provide similar hydrodynamic performance compared with circular cross section in heave and pitch motions for all ranges of wave frequency. Therefore, it is possible to use these types of cross sections for FPSOs because of manufacturing simplicity.

Effect of bar cross-section and female housing material on retention of mandibular implant bar overdentures: A comparative in vitro study.

Aim:The aim of this study is to evaluate the effect of different cross-sections of bar connecting two implants on the retention of mandibular overdentures with Hader clip or lined with heat-cured resilient liner as a housing material. The retentive values after simulated 1.5 years of service were also recorded.Materials and Methods:Edentulous mandibular acrylic model was constructed with two dummy implants located in the canine region and connected with cast bar assembly. According to bar cross-section and anchoring method, four groups (n = 10) of identical overdentures were used as Hader bar/clip group (HCG), Hader bar/silicone liner female housing group (HSG), oval bar/silicone liner female housing group (OSG), and round bar/silicone liner female housing group (RSG). Each overdenture sample was subjected to simulated wear up to 2740 manual insertions/separations. The mean retentive forces were measured at the baseline and after every 500 insertions. The data were statistically analyzed using one-way analysis of variance.Results:The present study demonstrated that all bar cross-sections showed a significant difference at the baseline (P < 0.05), but HSG showed greater initial retention compared to HCG, OSG, and RSG. OSG showed a significant higher retention after 2740 insertions (simulated five insertions/day).Conclusions:Within the limitation of this in vitro study and for a similar period of service, heat-cured silicone female housing for Hader bar could maintain greater retention for two-implant-retained overdentures than provided by conventional plastic clip after 1.5 year. The oval bar recorded reasonable initial retention values and maintained these values for 1.5 years of service.

Computer Simulation Analysis of Microchannel for a Continuous-Flow PCR Chip

The purpose of this study is to analyze the model of a continuous-flow Polymerase Chain Reaction (PCR) chip with CoventorWare software. It offered the ability of fast heating and cooling rate when the DNA duplication process happened. The main idea was to compare the effects of different cross sections of channel and find out the better one for heat transfer.

Bending behavior of empty and foam-filled aluminum tubes with different cross-sections

In this paper, the energy absorption mechanism of empty and foam-filled aluminum tubes with different cross-sections (circular, square and elliptic) under bending load is investigated numerically. The load-displacement curves of the present simulations are in very good agreement with those of published experimental data. Here, the existing analytical formulations are reviewed and compared with experimental results. In addition, the effects of different cross-sections and wall thicknesses on the energy absorption capacity and specific energy absorption of these tubes are fully investigated. The results indicate that the energy absorption of an elliptic foam-filled tube with 1.5 mm and 2 mm thicknesses increases about 45% and 73% in comparison with a square one, respectively.

Probing the Effect of Different Cross Sections in Asymmetric Systems

We present a complete systematic theoretical study of the multifragmentation for asymmetric colliding nuclei in heavy-ion reactions in the energy range between 50 and 1000 MeV/nucleon by using the isospin-dependent quantum molecular dynamics (IQMD) model. We have observed an interesting outcome for asymmetric colliding nuclei. The comparison between the symmetric and asymmetric colliding nuclei for the isospin-independent and isospin-dependent cross sections has been performed. We have found the pronounced effect of different cross sections and mass asymmetry on the nuclear reaction dynamics.

Model ingredients and multifragmentation in symmetric and asymmetric heavy ion collisions

The relative role of the momentum-dependent interactions and larger nucleon-nucleon cross section is discussed in multifragmentation using quantum molecular dynamical model. We find that the sensitivity of the larger cross section towards multifragmentation reduces in the presence of momentum-dependent interactions which makes it difficult to extract the magnitude of nucleon-nucleon cross section from multifragmentation. However, a large effect of different cross sections can be seen if a simple static equation of state is used.

A Model for Unsaturated Flow in Woven Fiber Preforms during Mold Filling in Resin Transfer Molding

In this paper, the unsaturated flow encountered in the woven or stitched fiber mats used in RTM is studied for the case of constant rate injection into a 1-D mold. Such fiber mats are characterized as a dual scale porous medium and a two-layer model, based on the difference in the length scales of the intra-tow and inter-tow spaces, is proposed. The mass balance is derived from first principles for an idealized representation of such type of porous media and incorporation of a sink term in the macroscopic equation of continuity is established. First a simple sink function, the constant sink, is studied and the downwardly drooping profile of the injection pressure, reported in previous experiments, is shown to be a natural consequence of the absorption of resin by the tows. Next an On/Off type constant sink function is proposed; critical parameters of unsaturated flows such as pore volume ratio and sink strength are introduced. Then the two-layer model with rectangular cross section is extended to two other types of cylindrical cross sections encountered in woven mats. A numerical scheme to solve the governing equations of sink models is discussed and results of simple analytical models and the two-layer models are presented. These models classify the flow through such woven mats as either a developing or a developed flow depending upon whether all or some tows behind the resin front are unsaturated. Parametric studies to identify important parameters affecting the length of the partially saturated regions near the front are presented. The simple On/Off type sink model also predicts the slopes of the injection pressure generated by the two-layer models for developed flow with good accuracy. The inlet pressure curve of the two layer models reproduce the characteristic drooping trend. Finally, the effect of different cross sections of the two-layer model upon the inlet pressure history is studied.