Magnitude Of Energy Dissipation Research Articles

Performance improvement of a rotating gas separator for electrical submersible pump considering entropy generation method

The utilization of Electrical Submersible Pumps (ESPs) stands as one of the foremost methods in artificially extracting oil, primarily within the oil industry. Under typical conditions, the pump encounters a two-phase flow of oil and gas. Should the gas phase within this mixture surpass an acceptable threshold, it can lead to a significant decline in performance and inflict detrimental damage upon the pump. To address this issue, the incorporation of a gas separator unit, one of the pivotal components within ESPs, is imperative at the pump's inlet section. Enhancing the gas separator unit holds paramount importance for ensuring pump safety and optimizing performance, particularly in wells with elevated gas contents.The conventional approach to calculating hydraulic losses in turbomachinery, relying on pressure drop calculations, often falls short in pinpointing the precise locations of losses. This paper delves into enhancing gas separator performance by augmenting gas separation efficiency through the application of the entropy generation method and leveraging the second law of thermodynamics. To achieve this, pivotal entropy-generating geometrical parameters of the gas separator were identified as the design variables necessary for forming the Taguchi sample space. Numerical simulations were conducted utilizing steady three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations for incompressible fluid flow, coupled with a turbulence model. Results indicate that the gas separation efficiency (GSE) of the initial model surged from 45.6% to 88% in the improved sample, albeit with a concurrent rise in entropy generation rate (EGR) from 209 W/K to 243.1 W/K. To establish a more comprehensive criterion for analysis, the ratio of GSE to EGR was employed as an objective function. This ratio quantifies the efficiency of gas separation per unit of energy loss, and it escalated from 0.218 in the primary sample to 0.362 in the improved sample, representing a 66% increase. This signifies that despite simultaneous increases in EGR and GSE, the rate of energy loss per unit of gas separation has diminished. Furthermore, the heightened EGR in the improved sample can be attributed to an increase in total volume, leading to an expanded contact surface area and consequently an elevation in total entropy. This investigation underscores the advantages of the entropy generation method, particularly in delineating the precise location and magnitude of energy dissipation within the rotating gas separator.

A Novel Single Tube Semi-Active Tuned Liquid Gas Damper for Suppressing Horizontal Vibrations of Tower-like Structures

The purpose of this paper is to present a novel single tube semi-active tuned liquid gas damper (SA-TLGD) for suppressing horizontal vibrations of tower-like structures and to study its damping effectiveness. The main difference to the well-known state-of-the-art tuned liquid column damper (TLCD) is the special geometric shape of the developed SA-TLGD. Contrary to the TLCD, the presented SA-TLGD only consists of a single horizontal tube that is partially filled with water. A large deformable elastic membrane with neglectable stiffness is used as the interface between the liquid and the air. Both ends of the horizontal tube are sealed and the resulting gas spring is used as the restoring force and frequency tuning parameter, respectively. The developed SA-TLGD is a semi-active vibration damping device, where its natural frequency and magnitude of energy dissipation can be re-adjusted during operation. Due to the lack of any vertical tube parts, this new type of vibration absorber requires significantly less installation space compared to the classical TLCDs. The equations of motion of the SA-TLGD and the coupled main system are derived by the application of conservation of momentum. The procedure of optimal tuning of the SA-TLGD is presented, and computational numerical studies are performed to demonstrate the damper effectiveness. It is shown that the application of the developed SA-TLGD provides a large reduction in the maximum horizontal forced vibration amplitudes of tower like-structures and that its semi-active functionality enables the possibility of re-adjustment any time during the operation life of the structure.

Fractal neutrons diffusion equation: Uniformization of heat and fuel burn-up in nuclear reactor

In this study, the fractal neutrons diffusion equation is constructed based on the concept of fractal anisotropy and product-like fractal measure introduced by Li and Ostoja-Starzewski using the method of dimensional regularization. In this approach, the global forms of dynamical equations are cast in forms involving integer-order integrals while the local forms are expressed by partial differential equations with derivatives of integer order. This theory is characterized by an effective buckling which varies with distance and a diffusion damping characterized by a spatially variable coefficient. These terms are major in nuclear reactor physics since the magnitude of energy dissipation in fission depends on the position and nature of interaction. We have discussed the cases of parallelepiped and finite cylinder reactors. In both geometrical types of reactors, it was observed that the ratio of the maximum flux to the average flux is too small since the uniformization of the heat fabrication and the fuel burn-up in the nuclear reactor is potential. This has important consequences on safety of the fuel operation and on the types of nuclear materials used in nuclear engineering reactors. Further details are discussed as well.

Tuning the Dissipation in Friction Dampers Excited by Depolarized Waves Across Patterned Surfaces

Recently, patterned surfaces (elastodynamic meta-surfaces) were shown to cause mechanical wave depolarization resulting in conversion of uniaxial waves to multiaxial vibrations. Frictional oscillators loaded in multiple directions provide more tailorable damping scheme when compared to uniaxially loaded equivalents. This paper utilizes wave depolarization properties of patterned surfaces in tuning frictional damping. In particular, two-dimensional (2D) motion achieved by anisotropic wave reflection and depolarization across patterned surfaces is exerted on a simple friction oscillator; and frictional energy dissipation is studied using the homogenization theory and mechanics of a simple friction oscillator under macro and microslip conditions. The degree of depolarization is shown to control the extent of frictional shakedown (no-dissipation) zones and magnitude of energy dissipation for different incident wave frequencies and amplitudes. Transmission of the depolarized waves from the patterned surface to the friction oscillator enables higher and more uniform frictional damping for broader loading conditions. Uniform damping facilitates predictive linear dynamic models, and tuning the magnitude of damping permits efficient and robust wave attenuation, and energy transfer and localization in dynamic applications. A discussion on modeling assumptions and practical utilization of this potential is also provided. The presented potential of tuning frictional dissipation from very low to high values by simple surface patterns suggests that more sophisticated surface patterns can be designed for spatially varying frequency-dependent wave attenuation.

Flexural response of polypropylene/E-glass fibre reinforced unidirectional composites

This paper presents a study of the flexural response of continuous E-glass fibre reinforced polypropylene composites. Experiments were designed to investigate monotonic and cyclic flexural response using three point bending test for laminates with different angle-ply and cross-ply arrangements. Results show that the monotonic and cyclic flexural response of the composites are influenced by the plastic deformation of the matrix. The study observed that increasing numbers of cyclic loads led to significant energy dissipation, stiffness reduction and micro-damage accumulation within the composite and especially at the matrix–fibre interface. Significant energy dissipation and damage were observed to dominate the first load-unload cycle. With subsequent cycles, the magnitude of energy dissipation and global damage reduces to a threshold value which is cycle independent. This study has also developed a phenomenological model to predict the dependence of energy dissipation with number of cycles. The experimental data generated here will be useful in the development of holistic macroscale constitutive models and finite element studies of the chosen test composite.

Effect of Roughness on Frictional Energy Dissipation in Presliding Contacts

A finite element model (FEM) is used to investigate the effect of roughness on the frictional energy dissipation for an elastic contact subjected to simultaneous normal and tangential oscillations. Frictional energy losses are correlated against the maximum tangential load as a power-law where the exponents show the degree of nonlinearity. Individual asperity is shown to undergo similar stick–slip cycles during a loading period. Taller asperities are found to contribute significantly to the total energy dissipation and dominate the trends in the total energy dissipation. The authors' observations for spherical contacts are extended to the rough surface contact, which shows that power-law exponent depends on stick durations individual asperity contacts experience. A theoretical model for energy dissipation is then validated with the FEM, for both spherical and rough surface contacts. The model is used to study the influence of roughness parameters (asperity density, height distribution, and fractal dimension) on magnitude of energy dissipation and power-law exponents. Roughness parameters do not influence the power-law exponents. For a phase difference of π/2 between normal and tangential oscillations, the frictional energy dissipation shows quadratic dependence on the tangential fluctuation amplitude, irrespective of the roughness parameters. The magnitude of energy dissipation is governed by the real area of contact and, hence, depends on the surface roughness parameters. Larger real area of contact results in more energy under similar loading conditions.

Effect of landing height on frontal plane kinematics, kinetics and energy dissipation at lower extremity joints

Lack of the necessary magnitude of energy dissipation by lower extremity joint muscles may be implicated in elevated impact stresses present during landing from greater heights. These increased stresses are experienced by supporting tissues like cartilage, ligaments and bones, thus aggravating injury risk. This study sought to investigate frontal plane kinematics, kinetics and energetics of lower extremity joints during landing from different heights. Eighteen male recreational athletes were instructed to perform drop-landing tasks from 0.3- to 0.6-m heights. Force plates and motion-capture system were used to capture ground reaction force and kinematics data, respectively. Joint moment was calculated using inverse dynamics. Joint power was computed as a product of joint moment and angular velocity. Work was defined as joint power integrated over time. Hip and knee joints delivered significantly greater joint power and eccentric work ( p<0.05) than the ankle joint at both landing heights. Substantial increase ( p<0.05) in eccentric work was noted at the hip joint in response to increasing landing height. Knee and hip joints acted as key contributors to total energy dissipation in the frontal plane with increase in peak ground reaction force (GRF). The hip joint was the top contributor to energy absorption, which indicated a hip-dominant strategy in the frontal plane in response to peak GRF during landing. Future studies should investigate joint motions that can maximize energy dissipation or reduce the need for energy dissipation in the frontal plane at the various joints, and to evaluate their effects on the attenuation of lower extremity injury risk during landing.

Monte Carlo investigation of hysteresis properties in ferroelectric thin-films under the effect of uniaxial stresses

The uniaxial stress dependence of the hysteresis behavior of ferroelectric films was studied. The DIFFOUR model was modified to include the uniaxial stress effect. Both the uniaxial stress and the external electric field were applied on the out-of-plane direction of the films. The polarization was measured with varying the magnitude of the applied stress and the electric field frequency via the dynamics of the polarization reversal in terms of hysteresis. The study was taken by means of Monte Carlo simulations using the spin-flip Metropolis algorithm. From the results, the district dependence of hysteresis behavior on frequency between low frequency and high frequency was prominent. On the other hand, the remanent and the coercivity significantly decreased with increasing applied stresses. Moreover, the areas under the hysteresis loops also decreased indicating smaller magnitude of energy dissipation. The results agree well with related experiments where applicable.

Identification of a mechanism of photoprotective energy dissipation in higher plants

Under conditions of excess sunlight the efficient light-harvesting antenna found in the chloroplast membranes of plants is rapidly and reversibly switched into a photoprotected quenched state in which potentially harmful absorbed energy is dissipated as heat, a process measured as the non-photochemical quenching of chlorophyll fluorescence or qE. Although the biological significance of qE is established, the molecular mechanisms involved are not. LHCII, the main light-harvesting complex, has an inbuilt capability to undergo transformation into a dissipative state by conformational change and it was suggested that this provides a molecular basis for qE, but it is not known if such events occur in vivo or how energy is dissipated in this state. The transition into the dissipative state is associated with a twist in the configuration of the LHCII-bound carotenoid neoxanthin, identified using resonance Raman spectroscopy. Applying this technique to study isolated chloroplasts and whole leaves, we show here that the same change in neoxanthin configuration occurs in vivo, to an extent consistent with the magnitude of energy dissipation. Femtosecond transient absorption spectroscopy, performed on purified LHCII in the dissipative state, shows that energy is transferred from chlorophyll a to a low-lying carotenoid excited state, identified as one of the two luteins (lutein 1) in LHCII. Hence, it is experimentally demonstrated that a change in conformation of LHCII occurs in vivo, which opens a channel for energy dissipation by transfer to a bound carotenoid. We suggest that this is the principal mechanism of photoprotection.

Metallic inserts as a tool to alter the structural damping of joined structures

The dynamic response of joined structures, notably the amplification of vibrations, is strongly influenced by the characteristics of the joints. Bolted joints are non-linear both in stiffness and magnitude of energy dissipation, and structures assembled with bolted joints inherit these non-linearities. This largely experimental study shows how thin metallic inserts in the contact region may serve as a tool to alter the non-linear properties of the joint and in this way increase or decrease the level of equivalent viscous damping in the structure. Both quasi-static and dynamic measurements have been performed and a mathematical model trimmed to the static measurements has been shown to produce valid results also for dynamic simulations.

Cell damage of microcarrier cultures as a function of local energy dissipation created by a rapid extensional flow.

Microcarrier cultures of Chinese hamster ovary cells were subjected to a range of energy dissipations created by an abrupt contraction. These flow conditions can be characterized as a rapidly transient, extensional, and shear flow. Cell damage was measured using a lactate dehydrogenase assay. The laminar flow in the device was modeled using two commercial, computation fluid-dynamic codes: POLYFLOW and FLUENT. Cell damage was correlated to numerical values of energy dissipation. The magnitude of energy dissipation at which cell damage began to be detected, 10(4) ergs cm(-3) s(-1) (10(4) cm(2) s(-3)), is consistent with values of energy dissipation estimated in bioreactors operated under conditions which result in cell damage. This magnitude of energy dissipation is orders of magnitude lower than those values reported to cause damage to suspended animals cells which is also consistent with generally accepted experimental observations. Finally, an analysis and discussion of the presence and relative importance with re- spect to cell damage of shear vs. extensional flow is included.

Effect of viscoelastic dampers on hysteretic response of reinforced concrete elements

This paper presents the effect of viscoelastic (VE-) dampers on hysteretic response, ductility and energy dissipation of reinforced concrete elements. A parametric study is carried out on reinforced concrete (RC) elements of different design ductilities (strength levels) having different degradation and pinching characteristics. The study uses the fiber element of the DRAIN-2DX program to simulate stiffness degradation, strength decay and pinching effects of the reinforced concrete elements. The VE-damper behavior is simulated by using the writer's nonlinear element based on the fractional derivative approach. The element is made compatible with the nonlinear dynamic analysis program DRAIN-2DX. The study indicates that VE-dampers significantly decrease the curvature demand at the plastic hinges, thus reducing the effect of stiffness degradation, strength decay and pinching on the reinforced concrete element hysteresis. The energies dissipated through hysteresis of the reinforced concrete element and the VE-damper element are studied under increasing amounts of added VE-damping ratios of the systems. Systems having different periods, and designed for different ductility ratios (strength levels), are considered. Increase in the VE-damping ratio of the systems progressively reduces the energy dissipation demand on the reinforced concrete elements. The contribution of energy dissipation by the VE-damper, however, increases at the same time. The net effect, more often, is an overall and significant increase in the total energy dissipation of the system. The degradation characteristics of the RC element hinges do not seem to affect the energy dissipation capability of the system with the VE-damper. The study indicates that the magnitude of energy dissipation by the VE-damper increases with the increase in added VE-damping ratio, up to a certain point beyond which further increase in VE-damping is not beneficial. This limit on the VE-damping ratio seems to depend upon the period of the system, but may be rather independent of its design ductility (strength level). The study also indicates that a particular value of VE-damping ratio, which is typically less than the above indicated limit, and requires some inelastic behavior of the RC elements, would maximize the total energy dissipation of the system. This optimum VE-damping ratio seems to depend upon the period and the design ductility ratio (strength level) of the system.

Magnitude of energy dissipation in fission

It is shown that no definite conclusions can be drawn regarding the magnitude of energy dissipation in fission during the descent from the saddle point, by a comparison of the calculated deformation and interaction energies of fission fragments near scission, with the experimental fragment excitation and kinetic energies. This is contrary to the conclusions drawn by Schultheis and Schultheis on the basis of a similar analysis. The reasons for this discrepancy are also discussed.

Reply to "Magnitude of energy dissipation in fission"

We contend that the method of Ramamurthy et al. is based on a misconception of the energy release at scission. Low dissipation (of less than 10 MeV) in /sup 252/Cf(sf) follows from a proper evaluation.