External Energy Flows Research Articles

MODEL OF MULTICOMPONENT LIQUID POOL EVAPORATION FORMED DUE ACCIDENTAL SPILLS

Quantitative analysis and assessment of technogenic risk imply a thorough study of the emergency process at the level of phenomenology. In the process of such a study, mathematical models of the physical and chemical processes of the formation of a hazardous substance in the surrounding space, the occurrence and influence of damaging factors on recipients, which are people, the environment, buildings and equipment, are involved. One of the most common scenarios for the formation of a hazardous substance in the environment is the spillage of a liquid phase, often of a multicomponent composition, onto the earth's surface. The subsequent evaporation of a hazardous substance is a key factor in the formation of an explosive, flammable or toxic cloud. Therefore, it is extremely important to correctly assess the intensity of the release of a hazardous substance into the environment. This study presents a mathematical model for the evaporation of a multicomponent liquid from the surface of an emergency spill, taking into account external energy flows that affect the evaporation process (heat flow from atmospheric air, heat flow from the underlying surface, radiation flow from the sun). The effect of cooling due to evaporation is taken into account. The developed model takes into account the mutual influence of the component composition of the liquid phase and the evaporation process. A comparative analysis of the simulation results was made with the published experimental data on the processes of evaporation of a cryogenic liquid (nitrogen) and liquids under non-boiling conditions such as ethanol and cyclohexane. The results of the comparison showed the applicability of the model in the field of quantitative risk analysis and assessment, and also revealed ways to improve the mathematical model of the multicomponent liquid pool evaporation.

Novel circularity and sustainability assessment of symbiosis networks through the Energy Quality Pinch concept

Circular Economy is a well-known concept to mitigate global resource depletion issues. The sustainability of a system is closely related to its environmental performance, which is directly linked to energy consumption. This work provides a circularity assessment tool by determining the minimum system energy requirements, according to the Energy Quality Factor, as it indicates the useful energy that can be extracted from material and energy flows. The proposed tool is Energy Quality Pinch Analysis which identifies the minimum energy requirements for a circular system and shows the system's sustainability. The analysis considers cascades of the energy used and released by recycling and symbiosis processes, evaluating the minimal external energy flows: high-quality energy input and waste energy output. The method is applied to case studies, including Total Site Heat and Power Integration, chemical energy reuse in wastewater systems, and Municipal Solid Waste management. Practical energy conversion technologies in each study are proposed as well. The results of the case studies indicate that the degree of energy recovery rate can be as high as 60% for the case of the utility system and higher for the cases of wastewater and municipal waste treatment, providing potentially valuable guidance to system designers.

Термодинамічна система ґрунту, його гомеостаз і вірогідний механізм утворення структури

Goal. To substantiate the dynamic functional model of the thermodynamic system of the soil in interaction with cyclic environmental factors, to disclose internal homeostatic processes, the result of which is the reproduction of the soil structure. Methods. System analysis, theoretical — to generalize the specifics of soil structure and create its physical model; experimental — for laboratory research. Results. Laboratory hydrophysical tests of soil samples of the intact structure revealed the occurrence of hysteresis of water holding capacity of the soil, the value of which can reach 10-20%. The main reason for this phenomenon is the compression of air by liquid membranes in the pore space. The results of the influence of heating the soil sample of constant moisture saturation are presented, which fix the self-oscillating character of the dynamics of capillary potential in the soil. That testifies to the intra-porous redistribution of moisture and the local transport mechanism of convective transport of the matter. Conclusions. The interaction of soil with thermodynamic environmental factors transforms it into a micro gradient dissipative structure with the emergence of many subordinate processes. The main results of their action are the periodic increase of local thermodynamic availability of nutrition for plants and the formation of non-uniform in space cementation of dispersed particles, which become the nuclei of structural units. The concept of soil homeostasis, combining subordination processes, characterizes the level of energy consumption of the external energy flow, due to which the basic properties and structural organization of the soil are reproduced.

Energy flow in thermostatted non-equilibrium molecular dynamics simulations

Energy transfers between internal kinetic and potential energy reservoirs in a simple liquid are studied by setting the temperature of one energy reservoir to a different value from that of the others and computing the resultant energy flows. In the first set of simulations, the x-directional kinetic temperature was artificially raised above the other five, and in the second, the x-directional configurational temperature was artificially raised above the other five. In both cases, external energy flows balanced, but unexpected energy flows between different directional components of the potential energy were observed. Additional simulations showed that these energy flows occurred regardless of the arrangement of thermostats imposed on the six degrees of freedom and the addition of shear. Heat flow between degrees of freedom that were ostensibly at the same temperature was anomalously observed. It was concluded that a different breakdown of the contributions to the configurational energy that is consistent with the definition of the directional configurational temperatures is required.

Design and analysis of energy recyclable bidirectional converter with digital controller for multichannel microstimulators

The power supply modulated microstimulator system can drive an expandable electrode array with reduced heat generation across the current drivers and high stimulation efficiency. Here, we present a comprehensive analytical modelling of the system to investigate internal and external energy flow during biphasic stimulation pulses spanning over varying loading configurations (e.g. number of electrodes, and stimulation current amplitude) that were not covered by existing works on the power supply modulated microstimulators. This paper fills the research gap by presenting the systematic tools for attaining insights of a stimulator system featuring a bidirectional DC---DC converter with an algorithmic digital controller. The models employed here are based on traditional analytical methods such as transfer functions and state-space dynamic models incorporating various circuit elements incurring power loss. With the models, the behaviour and power efficiency under a wide range of parameters associated with stimulator are attained. Numerical assessment reveals that the digital controller can track the output supply voltage at the phase transition boundaries just in tens of switching cycles. The system was also studied on a verification platform, where the internal signals of the digital controller were carefully examined. Measurement results show that the system behavior well matched to the simulation results, demonstrating the effectiveness of the analytical system model for obtaining key insights for generic large-scale micro-stimulator designs.

Solution of the Stefan problem in a conventional modified formulation for semitransparent media with consideration of isotropic radiation scattering

Numerical simulation of radiation-conductive heat transfer with a phase transition of the first kind in a semitransparent, isotropically scattering medium is carried out. A hypothesis of zero total external energy flow in the course of the phase transition is used in the formulation of the problem. The fields of temperature and the resulting radiation fluxes over a wide range of single scattering albedo and two values of the reflection coefficient of boundaries are obtained. It is shown that there is an increase in the reflection coefficient of boundaries, the effect of the scattering albedo decreases, and the melting process in general is delayed in time.

Open dissipative seismic systems and ensembles of strong earthquakes: energy balance and entropy funnels

A concept of seismic system (SS), which is responsible for the preparation of an ensemble of strong earthquakes, is considered as an open dissipative system exchanging energy and entropy with the environment. Open dissipative SS allow one to describe the equilibrium and non-equilibrium states of SS, and the lithosphere evolution under different plate tectonic settings on the basis of seismostatistics. Several new seismic parameters (‘seismic temperature’, ‘seismic time’, dissipation function, efficiency, inelastic energy, dynamical probability) are defined and proposed for better understanding and describing the dynamical processes. The Sakhalin SS is considered to illustrate the behaviour of proposed parameters. By analogy to Liouville's equation in thermodynamics, it is shown that there is no criterion of instability in the domain where the Gutenberg-Richter law is true. In the proposed approach, the instability origination and the formation of seismogenic structures in the lithosphere are based on the energy versus information entropy power law; the existence of ‘time arrow’ also proceeds from such a dependence. Application of energy and trajectory diagrams enables to describe the preparation of strong earthquakes within an ensemble in terms of slow and fast timescales. These diagrams help perform the spatiotemporal-energy monitoring of the instability origination in the lithosphere. It is shown that the information entropy parameter can serve as a measure of the unknown external energy flow into the system (this energy is supplied for the elastic radiation energy in the earthquake sources and for inelastic processes in the system volume). The property of the ensemble of strong earthquakes is periodically to restore the SS equilibrium state that enables to describe the SS energy balance. The results offer possibilities to estimate the fraction of inelastic energy released by the SS medium during the preparation and occurrence of seismic catastrophes. The construction of phase diagrams and ‘entropy funnels’ in the virtual space (with time, energy and entropy coordinates) can provide new opportunities for the visualization of undetectable processes leading to disastrous earthquakes.

Influence of initial conditions on the large-scale dynamo growth rate

To investigate the effect of energy and helicity on the growth of magnetic field, helical kinetic forcing was applied to the magnetohydrodynamic(MHD) system that had a specific distribution of energy and helicity as initial conditions. Simulation results show the saturation of a system is not influenced by the initial conditions, but the growth rate of large scale magnetic field is proportionally dependent on the initial large scale magnetic energy and helicity. It is already known that the helical component of small scale magnetic field(i.e., current helicity $<{\bf j}\cdot {\bf b}>$) quenches the growth of large scale magnetic field. However, $<{\bf j}\cdot {\bf b}>$ can also boost the growth of large scale magnetic field by changing its sign and magnitude. In addition, simulation shows the nonhelical magnetic field can suppress the velocity field through Lorentz force. Comparison of the profiles of evolving magnetic and kinetic energy indicates that kinetic energy migrates backward when the external energy flows into the three dimensional MHD system, which means the velocity field may play a preceding role in the very early MHD dynamo stage.

Information in the Animate and Inanimate Worlds

Closed systems are governed by the second law of thermodynamics and cannot spontaneously become more ordered. In open physical systems exposed to external energy flows, additional macroscopic degrees of freedom (“memory cells”) emerge, their number increasing with an increase in the flow and orderliness of the external energy. Biological systems are characterized by molecular degrees of freedom, the density of which is more than twenty orders of magnitude higher than that of macroscopic degrees of freedom in any open physical system exposed to the same external energy flow. This indicates that the self-organization of physical systems in external energy flows and the self-organization and evolution of living systems are fundamentally different. Thus, although life is an open system, the energy (food) flows that it consumes and all other external factors affecting life are so poorly ordered, compared to life itself, that they cannot increase the degree of order in the latter. Therefore, living systems obey an analogue of the second law of thermodynamics: within periods of time considerably shorter than the duration of evolutionary changes, living systems can only lose the accumulated information (i.e., the entropy can only increase), even if the systems consume external energy–food flows.

Influence of active heat sinks on fabric thermal storage in building mass

There is an increasing drive towards low energy architecture and developing buildings that work with the climate rather than in spite of it. One technology in the area of low energy building design is that of utilising building thermal mass and/or active thermal storage systems. Essentially the mass acts as a thermal flywheel and can both attenuate external energy flows and suppress internal environmental energy swings. These active thermal storage systems can take differing configurations and in this paper the results and comparisons for a few differing geometries and configurations are presented. Relationships between slab surface temperature, cooling potential and active core temperature are also presented.

Computer modeling of the biotic cycle formation in a closed ecological system.

The process of biotic turnover in a closed ecological system (CES) with an external energy flow was analyzed by mathematical modeling of the biotic cycle formation. The formation of hierarchical structure in model CESs is governed by energy criteria. Energy flow through the ecosystem increases when a predator is introduced into a "producer-reducer" system at steady state. Analysis of the model shows that under certain conditions the presence of the primary predator with its high mineralization ability accelerates the biotic turnover measured by primary production. We, therefore, conclude that for every system it is possible to find a suitable predator able to provide the system with a higher biotic turnover rate and energy consumption. Grant numbers: 99-04-96017/2000.

Analysis of internal and external energy flows associated with projected process improvements in biomass ethanol production

Possible improvements in biomass ethanol production are decribed involving heat-pumped distillation, steam-cycle heat integration, elimination of seed fermenters, pretreatment heat integration, advanced pretreatment, thermophilic DMC, and incrased carbohydrate yield to 90% of theoretical. Although speculative, a futuristic process incorporating these improvements may be useful for anticipating some features of a technologically mature biomass ethanol process, as well as for comparing ethanol production to more technologically mature energy-conversion processes. Relative to the current state-of-the-art National Renewable Energy Laboratory process design, the futuristic process has 101% higher electricity revenue, 31% hgiher ethanol revenue, and 35–39% higher overall revenue depending on the assumed ethanol value. The overall first-law thermodynamic efficiency is 43% for the current NREL design and 59% for the futuristic process. A general consideration of the costs associated with the process improvements examined indicates that: 1. Elimination of seed reactors, advanced pretreatment, and thermophilic DMC all have large potential cost reductions independent of their benefits with respect to increased surplus electricity; 2. Steam cycle improvements and pretreatment heat integration are expected to have modest cost benefits that are dependent on increased electricity revenues; and 3. The relative cost of heat-pumped distillation depends on scale, capital recovery, and electricity value, but is generally similar to the already low cost of conventional distillation provided that the fermentation broth has a reasonably high ethanol concentration.