Perfect Displacement Research Articles

Do renewable energy sources perfectly displace non-renewable energy sources? Evidence from Asia-Pacific economies.

The existing scholarly discourse surrounding the energy transition has long operated on the assumption of perfect displacement of non-renewable energy. However, an evolving set of studies highlights an intricate web of inefficiencies and complexities that prevent the perfect displacement of fossil fuel energy with renewable energy production. Since this could carry serious implications for the environmental targets of several economies, it is crucial to accurately and continuously measure the actual extent of fossil fuel displacement. Within this framework, this study empirically investigates the extent of non-renewable energy displacement by renewable energy for a balanced panel of seven Asia-Pacific (APAC) countries between 1989 and 2015. The outcome function also controls for globalisation, real GDP per capita, and crude oil prices. After implementing the necessary diagnostics, the panel cointegration establishes a significant long-run relationship among the selected variables. The PMG-ARDL estimation indicates that renewable energy production and globalisation significantly reduce the fossil fuel energy production, whereas real GDP per capita and crude oil prices induce it positively. However, the coefficient of renewable energy production is only - 0.39, indicating that more than 2.5 units of renewable electricity are necessary to displace a unit of non-renewable energy. As such, this study concludes that the current energy transition in Asia-Pacific region is not perfect. These results are robust to the usage of the FGLS estimation technique. The study suggests the adoption of a new energy transition that allows greater displacement of fossil fuel energy as well as gradual reduction in overall energy use.

Investigating the assumption of perfect displacement for global energy transition: panel evidence from 73 economies

Investigating the assumption of perfect displacement for global energy transition: panel evidence from 73 economies

Investigation of the scavenging process in two-stroke uniflow scavenging marine engines by a real-time multi-stage model

The increasing demand of digital twin marine engine requires real-time physical models for prediction. In two-stroke uniflow scavenging marine engines, a real-time physical model for the scavenging process is rarely found since it is difficult to describe the complex in-cylinder air motion. Without an accurate prediction of the fresh air loss and residual burned gas in the cylinder, the precision of combustion and emission simulation cannot be guaranteed as well. In a marine engine digital twin system, the scavenging ratio and fresh air skip are the vital for the further simulation of combustion and emission. To predict them in real-time, a novel zero-dimensional (0D) multi-stage scavenging model is proposed in this article. In the cylinder zone, the complex gas motion is ideally divided to four stages: exhaust gas blowdown, perfect displacement, displacement-mixing, and perfect mixing. The duration of each stage is determined by the engine design and control parameters. Then, the thermodynamic conditions at each stage are simulated to obtain the mass of residual burned gas, fresh air inlet, and outlet. The results of the 0D model agree well with the results of the CFD simulation, and the mean relative errors of temperature, pressure, and total mass do not exceed 3%, 4%, and 2%, respectively, which indicates the potential for the two-stroke marine engine digital twin system. It could also be applied in a control-oriental engine model or engine diagnostics in the future.

Environmental Benefits of Engine Remanufacture in China's Circular Economy Development.

China has recently implemented broad strategies aimed at achieving a circular economy by providing subsidies for the remanufacture industry and setting a target of 15% increase in energy efficiency in industrial production across sectors, among other strategies. Here, we examine the environmental implications of these policies in the context of engine remanufacture, using an environmental computable general equilibrium (CGE) model. Results indicate that both the subsidy policy and energy efficiency improvement target can contribute to economic growth and emission reductions, but the subsidy policy is estimated to have far greater impacts. The implementation of both can reinforce each other, generating higher economic and environmental benefits than the sum of each occurrence alone. Another major finding from our model is that an additional remanufactured engine only displaces 0.42 (90% confidence interval from 0.32 to 0.47) of a new engine (comprised of new parts), mainly because the lower prices of remanufactured engines lead to greater consumption. This ratio is much lower than the 1:1 perfect displacement commonly assumed in life cycle assessment (LCA) studies. Overall, our study suggests that the subsidizing of engine remanufacture in China can help promote the industry, improve overall economic welfare, and contribute to environmental targets. Our study also contributes to the estimation of more realistic product displacement ratios in LCA.

SMA bending bars as self-centering and damping devices

This study proposed a new type of the shape memory alloy (SMA) bending bars with a new clamping machine and investigated their bending and cyclic behavior subjected to pushing and pulling actions through experimental works. The aim was to characterize the self-centering and damping capacity of the SMA bending bars to develop self-centering and damping devices and evaluate their efficiency in seismic and dynamic applications. For this aim, two types of SMAs were considered: (1) superelastic SMA (SE SMA) and (2) martensite SMA (MA SMA). First, the bending tests were performed on single SE SMA and MA SMA bars and their corresponding bending behaviors were illustrated in the form of force–displacement curves. Results showed that the MA SMA bar provided higher energy dissipation capacity while the SE SMA could provide a better displacement recovery. Thereafter, the bending behaviors of multiple bars with various combinations of SMA bars, namely, double SE SMA (SS), SE SMA-MA SMA-SE SMA (SMS), and MA-SE-MA (MSM) were investigated. Results showed that MSM provided the highest energy dissipation capacity among all while the SMS showed a better structural performance considering a combination of damping and self-centering capacities. Then, to enhance the displacement recovery and energy dissipation capacity of SMA bars, the single SE SMA bar, and SMS were annealed. Results showed that the annealing enhanced the structural performance, but no perfect displacement recovery was still obtained.

Impact of the dogleg geometry on displacement efficiency during cementing; an integrated modelling approach

In the dogleg section of directional wells, casing strings bend to fit the borehole trajectory, which may lead to complicated contact areas with the borehole. The severity of dogleg in combination with casing properties may make the formed annulus space so complex that cement may not displace mud remnants very well. While current simulation methods only consider constant eccentricity, we propose a model for a more general geometry defined by the well trajectory and casing properties. We have developed a three-dimensional finite element model (FEM) to simulate large-deformations of the casing while running into the dogleg. The casing deformation determines the annulus geometry that is supposed to be filled with cements. We utilized a computational fluid dynamics (CFD) model to simulate cement-mud displacement in the resultant annulus space. The effects of density ratio and rheology on the displacement efficiency are analyzed here. The obtained numerical results show the complicated contact geometry of the casing and borehole at the dogleg, which may worsen in casing strings with small thickness and large curvature doglegs. Results show that the magnitude of the stress developed along the casing can considerably increase due to friction. Complicated geometry of the annulus induced by casing deformation makes mud displacement by cement in the dogleg difficult. Continuous drilling mud pockets are formed due to the cement reverse flow. However, increasing density difference helps development of a steady and shorter displacement interface. We also noticed the phenomenon of reverse flow occurred during the cementing, which prevents sweeping or perfect displacement of the cement in the annulus space. The outcome will help us to prevent any potential damage that might happen due to large pressure fluctuations during fracturing through casing by minimum costs and avoid such potential integrity problems by setting a packer and tubing or using more appropriate cement recipes.

On the use of different models for consequential life cycle assessment

Consequential life cycle assessment (CLCA) studies how a system responds to a decision in question. There has been a growing body of CLCA studies in the last decade, with different models being incorporated from other fields, partly to compensate for the limitations of the conventional linear models used in LCA. As much as we welcome the use of new models in (C)LCA, here we provide a cautionary note on this trend by highlighting the restrictiveness of assumptions underpinning different models. And we point to a path forward for future CLCA studies. We review the model setup of, and major assumptions behind, two classes of models used in CLCA studies. One is linear models such as process- or input-output-based LCA, which have been conventionally used in LCA. And the other is nonlinear optimization models such as computable general equilibrium (CGE), which are increasingly being applied in CLCA studies. While the linear models rest on several assumptions such as fixed coefficients and unlimited supply of inputs, so do the nonlinear optimization models. Among others, CGE models assume rationality, the limitations of which have been increasingly revealed by findings of experimental and behavioral economics. We also discuss some of the foundational questions. Are LCA estimates verifiable or falsifiable? If not, then is LCA science? And is the traditional definition of science based on falsifiability suited for LCA and other disciplines studying complex systems? Considering that (1) LCA studies the complex human environment system and model estimates or predictions are largely unverifiable and (2) different classes of models have different strengths and limitations, we make the following recommendations. For decision makers, particularly policy makers, we recommend evaluating estimates from different classes of models, as opposed to relying on a single class, for more robust decision support. Each model estimate or prediction can be taken as a point of evidence. If most estimates point to the same direction, the results would be considered strong evidence of what would happen. If, on the other hand, model estimates are scattered with no obvious patterns, the results would be considered inconclusive and thus more research is needed. For modelers, we recommend efforts be put into improving a model’s predictive capability by, e.g., relaxing some of the unrealistic assumptions such as fixed input/output coefficients, 1:1 perfect displacement, and systemic optimization. Our main message is that mathematical sophistication does not necessarily equal improvement in model accuracy. Given the complexity of the human - environment system, the uncertainties of predicting the future, and the limitations of different models, a multi-model approach is entailed for more robust decision-making, and continuous effort is needed to improve model predictability.

Analytic solution of biparameter axial dispersion model

A linear axial dispersion model involving two parameters, Peclet number (Pe) and retardation coefficient (Rd) has been presented. Model equations have been solved analytically, using Laplace transform. Solution has been obtained in terms of complementary error function. Two limiting cases of perfect mixing and perfect displacement have also been discussed. Verification of model is carried out by using the experimental data of a washing cell.

Solution of diffusion–dispersion models using a computationally efficient technique of orthogonal collocation on finite elements with cubic Hermite as basis

In this paper, linear and non linear diffusion–dispersion models involving fluid flow through porous cylindrical particles are solved using orthogonal collocation on finite elements with cubic Hermite as basis. The technique involves partitioning of axial domain into equal elements and then orthogonal collocation method with cubic Hermite as basis function is applied within each element. Exit concentration profiles are drawn for Peclet numbers ranging from 0 (perfect mixing) to ∞ (perfect displacement). Proposed technique is computationally efficient, stable and yields accurate solution, even for nonlinear stiff problem. Correlation with industrial parameters is also presented.

Modeling and Analysis of the Scavenging System for a Two-Stroke Cycle Hydraulic Free Piston Engine

A prototype of hydraulic free piston engine (HFPE) is being designed and constructed by Jilin University to achieve direct hydraulic wheel-drive and replace the current hydraulic drivers. This paper is aimed at modeling and analyzing the scavenging system for the HFPE. Based on the prototype engine E150, two stroke scavenging system for HFPE has been designed by analogy, the gas flow of HFPE during the scavenging process is simulated by using the commercial CFD software AVL FIRE. So some key scavenging parameters and flow field were obtained, the simulated results indicate that scavenging efficiency of loop scavenging system can meet the design requirement, it lies between perfect displacement and perfect mixing scavenging, and keeps decreasing while the operation frequency keeps increasing.

Understanding process intensification in cyclic distillation systems

The most effective separation possible in distillation columns takes place in the hydrodynamic regime where there is perfect displacement of the liquid and vapor streams. This can be achieved in distillation equipment with separate phase movement (SPM). Such an innovative route for process intensification in distillation is called cyclic distillation. The required process conditions are the lack of liquid outflow from the tray during vapor admission and the lack of liquid mixing in adjacent trays upon outflow of liquid. Remarkably, the throughput of such a column that operates in a controlled cycle mode is two or more times higher than the throughput reachable with conventional operation, at equivalent separation performance. In this study, a theoretical stage model with perfect displacement is proposed and the theory of the process working lines is developed. An adequate mass transfer model is also described along with the mode of calculation of tray columns operating in the cyclic operation mode. Sensitivity analysis was used to determine the effect of the key model parameters. The theoretical developments were implemented at industrial scale and subsequent testing showed an increase in the separation efficiency of 2–3 times as compared to the standard process.

Motive Forces in a Complex Model Involving a Direct Flow and Mixing of a Liquid

The influence of liquid mixing on mean logarithmic and arithmetic forces as well as the numbers of transfer units in direct flow has been studied. The extreme cases where liquid on the plate is entirely mixed and where it moves in a regime of perfect displacement are considered. The interrelationship between the mean arithmetic forces and numbers of transfer units in the case of complete liquid mixing and without it has been found. Dependences of the efficiency on the numbers of transfer units are determined.

Modelling ventilation by means of combined mixing and displacement flow

It is convenient to describe the ventilation of an occupied space solely by a single parameter, namely the air change rate, and to characterize air distribution as either mixing or displacement. In practice, distributions which are perfect mixing or displacement are rare, but to analyse air distribution patterns it is usually necessary to use a complex model (e.g., computational fluid dynamics), thus losing the conceptual simplicity of the mixing and displacement models. By combining the mixing and displacement models, a new two-parameter model is proposed which retains the conceptual simplicity of its parents. To the air change rate is added a displacement efficiency parameter which shows the closeness with which the air distribution approaches perfect displacement and gives an overall indication of air distribution sufficient for many applications.

Leaching of soluble salt during infiltration and redistribution

The paper reports an experimental study of miscible displacement of soluble salts during infiltration and redistribution of water in vertical, homogeneous columns of sandy, sandy loam and clay soils with initially uniform salt and moisture contents. Calcium chloride, mixed uniformly in initially dry and moist soils, was leached with water under transient and steady infiltration conditions. The salt and water profiles were determined immediately following infiltration and after matching total infiltration and redistribution times. Irrespective of different flow conditions and soil types, the “centre of mass” of salt front coincided with the “piston front” that would exist given perfect displacement of water initially present in the soil by the water being infiltrated (piston-flow model). Furthermore the advance of “centre of mass” of salt front was independent of the water application rate and initial soil water content in all soils following both infiltration and redistribution.

Filtration with variable slurry concentration.

Filtration characteristics of slurries with varying concentration under constant applied pressure were studied. The problem was investigated by considering addition of feed slurry to a filtration chamber initially containing particulate free liquid. Theoretical analyses of two limiting cases of perfect displacement and complete mixing are presented. Constant pressure filtration experiments on Westex talc designed for variable slurry concentration under complete mixing conditions confirm theoretical predictions. Analyses of experimental data ignoring the variations in slurry concentration would be incorrect and would lead to erroneous results. Based on theoretical conclusions, a method of analysing experimental data under such conditions is presented.

The effect of changing viscosity on the transient response of a reaction vessel

The material presented in this paper demonstrates that small continuous flow vessels behave like perfect mixers when mechanical agitation is applied and behave very nearly like perfect mixers even without the use of an agitator. The agitation of the inlet stream seems to give sufficient agitation. The case of a high viscosity fluid replaced by one of lower viscosity follows quite different behavior. For extremely low flow rates the system seems to exhibit almost perfect displacement if there is no agitation but behaves as a perfect mixer if there is agitation. With moderate flow rates the behavior is similar with or without an agitator and shows characteristics of dead space, channeling and diffusion.

Paper 20: The Thermodynamics of Charging and Discharging Processes

A comprehensive analysis of charging and discharging processes is presented. The work is of particular relevance to gas exchange processes which occur in internal combustion engines. A rigorous treatment is given of discharge from and charge to a container. In the discharge process irreversibility in the container and the outlet passage are considered separately. A unique pressure-temperature relation is derived for a special case of the charging process and an equation giving the entropy change in the container is derived. It is shown that the mass trapped in the container is a linear function of the pressure in the container. The case of discharge from one container to another is considered, as is the problem of consecutive charging and discharging of one container. For simultaneous charging and discharging no entirely rigorous analysis can be derived. Two analyses—those of ‘filling and emptying’ and ‘perfect displacement’—are presented.

Oil-Water Displacements in Microscopic Capillaries

Abstract Methods previously developed for the study of liquid displacements in microscopic capillaries (inner diameters of 3 to 40 microns) have been used to investigate oil-water displacements in capillaries initially filled with water. Displacement calculations assuming perfect displacement and no capillary pressure hysteresis yielded oil effective viscosities smaller than the macroscopic viscosities. For a given liquid pair, the oil effective viscosity decreased both with decreasing capillary size and with increasing oil-water viscosity ratio. This behavior can be explained by the existence of an annular water film (20 Å to 260 Å thick) on the capillary wall. When the capillary was first filled with oil, the ratio of the oil effective viscosity to the normal oil viscosity was highest for the first water displacement and decreased with subsequent displacements. Sometimes the oil effective viscosity ratio during the initial water displacement was greater than unity. Introduction In a previous paper, a technique was described for studying air-liquid and liquid-liquid displacements in very small capillaries of uniform diameter, in the hope that such microscopic data would further the understanding of the nature of multiphase fluid flow through porous media. That paper contained comprehensive data for air-liquid displacements in Pyrex capillaries, with a few data for oil-water displacements in capillaries initially filled with water. The purpose of this paper is to present more complete results for oil-water displacements in capillaries initially filled with water, and to describe for the first time such observations in capillaries initially filled with oil. In this way the effect of the wetting history of the system upon the displacement process may be studied. Methods The basic techniques employed were described in the previous paper. The measuring procedure and the working equations will be briefly summarized here and a few modifications will be pointed out. For the present study, temperature control within 0.1 degrees C was obtained by placing the microscope and its immediate accessories in a thermostated air bath made of a steel frame covered with plexiglas.