Energy Balance Approach Research Articles

Uplift capacity of the helical anchor installed in cohesionless soil using energy balance approach

Uplift capacity of the helical anchor installed in cohesionless soil using energy balance approach

Quantifying the probability of rupture arrest at restraining and releasing bends using earthquake sequence simulations

Fault bends are known to act as barriers to rupture propagation in many earthquakes. A recent compilation of the surface rupture traces of paleo earthquakes quantifies the probability of rupture termination as a function of the bend angle. To understand the physical basis of these unique statistics, we carry out 2D quasi-dynamic earthquake sequence simulations on a fault with either a restraining or releasing (double-) bend. The fault is loaded by steady sliding from an adjacent creeping region, rather than with backslip, together with a stress relaxation method to avoid unphysical stress buildup due to the curvature of faults. This relaxation is a proxy for unmodeled off-fault secondary faulting. This ensures the existence of a long-term steady earthquake cycle and stress field, the latter of which is determined by the balance between the slip-induced stress changes and relaxation terms. We quantify the influence of the bend on rupture propagation by computing passing ratio (i.e., the fraction of ruptures that propagate through the bend). Our simulations approximately reproduce the Biasi-Wesnousky empirical law for a wide range of parameters (e.g., bend width, stress relaxation time, background stress). Also, we reproduce geologic observations that the long-term slip rate of a fault has local minima at restraining bends, without assuming spatially varying loading rates using the backslip approach. Additionally, we find that restraining and releasing bends have different earthquake cycles. For restraining bends, many ruptures are arrested before reaching the center of the bend, and the passing ratio decreases with increasing the bend angle. For releasing bends, ruptures stop after passing the center of the bend, and the passing ratio abruptly drops from near unity to zero at around 20∘. This difference can be qualitatively explained by an energy balance approach. Our model has a potential to understand the seismogenesis of nonplanar faults and we can readily extend our model into 3D specific fault systems for hazard assessment.

Effect of gravity on the spreading of a droplet deposited by liquid needle deposition technique

This study represents an experimental investigation, complemented with a mathematical model, to decipher the effect of gravity on the spreading dynamics of a water droplet. For the theoretical discussion, an overall energy balance approach is adopted to explain the droplet spreading under both microgravity (μg) and terrestrial gravity condition. Besides explaining the mechanism of the droplet spreading under microgravity condition achieved during the parabolic flight, a technique with a detailed experimental set-up has also been developed for the successful deposition of droplet. A rational understanding is formulated through experimental investigation and theoretical analysis, which allows us to distinguish the transient variation of the spreading of a droplet, between microgravity and terrestrial gravity condition. The spreading of the droplet is predicted by the non-linear overall energy balance equation, which accounts for the operating parameters in the form of non-dimensional groups like Reynolds number ({{{rm{Re}}}}), Weber number (We) and Bond number (Bo). To distinctly identify the difference in the drop spreading at terrestrial and microgravity conditions, the Bo with transient gravitational field obtained through the on-board accelerometer is considered. The obtained theoretical results are further corroborated by experimental results which are obtained from the parabolic flight.

Mathematical Model of Shear Stress Transfer at Fiber-Matrix Interface of Composite Material

This paper shows a mathematical model of shear stress transfer at the interface between fiber and matrix composite. The stress transfer is a key parameter determining the quality of fiber-matrix interface, which directly correlates with the composite performance as load-bearing structures. The model is derived from the energy balance approach in prior and post fiber cracking. The debonding process is included in the model by implementing traction-separation law. The results show the developed model can predict the shear stress along with the interface. There are significant differences in shear stress by considering the debonding process compared with conventional models. The debonding process must be regarded to assure an accurate evaluation of the interface quality.

Droplet temperature measurement in GMAW

This work presents measurements of the droplet temperature for the Gas Metal Arc Welding process. Four different aluminium electrodes were used for experiments performed under the same conditions. The approach used yielded higher droplet temperatures than were obtained in previous experiments with the same raw data because the energy balance approach differed. However, trends were similar, with a minimum value close to the transition current and a tendency to increase with the current. Anode fall voltages behaved similarly, increasing with the current. Differences in temperature were found between the four electrodes. This can be explained by the different alloying elements present on the electrodes, which evaporate and take energy out of the droplet.

Hybridizing solar dish Stirling power system with single-effect desalination for sustainable electricity and freshwater co-generation: Mathematical modeling and performance evaluation

At present, poly-generation sustainable systems are highly promising pathways that could produce several beneficial energy outputs, such as electricity, heat, and freshwater, that have the potential to fulfill financial competitiveness and higher efficiencies. Considering the great advantages of the solar dish/Stirling cycle, this study introduces comprehensive theoretical modeling and performance analysis of a solar dish/Stirling-powered single effect distillation system (SDSPSEDS) for combined electricity, heat, and freshwater tri-production. A detailed mathematical model executed in MATLAB software based on energy balance and opt-geometric approaches was established to simulate the SDSPSEDS operation dynamically. In order to analyze its performance under real weather conditions of Tabuk, KSA, for four seasonal scenarios. The energetic performance of the hybrid SDSPSEDS is comprehensively evaluated in terms of net electric power, solar-to-electricity conversion efficiency, Stirling engine rejected heat, distilled freshwater productivity, and overall co-generation efficiency of the hybrid system. The simulation results show that the daily electrical energy produced by the SDSPSEDS is 234.7, 194.6, 159.8, and 190.0 kWh/day. In contrast, the daily freshwater production is obtained as 787.4, 657.3, 545.0, and 650.0 kg/day in June, September, January, and March, respectively. Moreover, it is also found that the overall daily co-generation efficiency of the hybrid SDSPSEDS is increased to 62.60%, 53.50%, 47.40%, and 52.96% compared to only daily average electrical efficiencies of 20.92%, 17.82%, 15.50%, and 17.60% attained; in the same examined seasonal days, respectively when utilizing only standalone solar dish/Stirling power system. Thus, the findings of this study proved that the hybrid SDSPSEDS is an efficient system to produce power and water in rural areas with no water piping network or electrical grid.

An energy balance and multicriterial approach for the sizing of a hybrid renewable energy system with hydrogen storage

As the clamour for a Net Zero carbon energy economy increases, it is necessary to harness the potential of renewable energies in powering buildings to lower fossil power plants' contributions to the overall energy mix. This paper aims to present an energy balance load sensitivity analysis and multi-criteria method for sizing a green energy system for powering two office complexes that house space research laboratories. The energy component considered includes battery storage (BAT), captive diesel generator (DG), fuel cell (FC), hydrogen storage (H2T), solar photovoltaic (PV), and wind turbine. Using HOMER, the techno-economic features and the hourly operational details of the energy components were obtained. The efficacy of Entropy- Additive Ratio Assessment was deployed on the outputs from HOMER to obtain the most preferred energy system based on more than one criterion. The result of the study indicates that the most preferred energy system for Abuja is a PV, WD, FC, DG, and BAT, having a total net present cost (TNPC) of $220,930. In contrast, the most suitable energy system for the energy in the Anyigba office consists of PV, FC, and BAT, with its TNPC at $106,955.

Implementation of optimal oil flushing methodology for nuclear steam turbo generator oil circuits

The first turning gear operation is regarded as a significant milestone in the overall activities of Turbine Generator system commissioning. To accomplish this critical goal, the lube oil circuit must be clean and free of all type of contaminants. The purpose of this paper is to elaborate on the various flushing tactics used in the Prototype Fast Breeder Reactor 500 MW Turbo Generator (TG) oil systems, to understand the factors that influence oil circuit flushing, the difficulties encountered during flushing, and to optimise the flushing process of TG oil circuits. Also A simple method was used in this paper to determine the minimum amount of oil required to begin flushing and the make-up requirements of lube oil at various stages of flushing. The percentage of oil passing through the cooler and cooler bypass line during the thermal shocking process was also determined using an energy balance approach. Based on TG oil circuit commissioning experience, an optimised methodology for completing the TG oil circuits flushing exercise is also proposed. This study demonstrates that the cooling and heating times of lube oil can be controlled during oil flushing, resulting in an increase in the number of thermal shocks per day and a significant reduction in flushing time.Article HighlightsThis paper is the result of flushing experiences with oil circuits of a 500 MW Nuclear power plant. This can be used to minimize oil quantity and the time flushing thereby lot of man hours and cost of flushing could be saved during flushing of turbine oil circuits.The minimum oil required for turbine oil circuit flushing is not readily available. The method outlined here can be used to determine the minimum amount of oil required for each stage of oil circuit flushing.This paper describes an energy balance methodology that can be used to increase the number of thermal shocks per day during flushing, thereby significantly reducing flushing time.

Modelling and optimal control of growth, energy, and resource dynamics of Hermetia illucens in mass production environment

Mass production of Hermetia illucens insect larvae is now being adopted in many countries and is taking an industrial production approach. Despite abundant literature on factors that affect larvae growth and the optimal static parameters identified in laboratory setup, for an industrial production process it is necessary to identify the trajectories such that the growth as well as the production process is optimal. To achieve this in this work, some of the important requirements and challenges involved thereof are identified and objectives of the automation process are formulated within a model based optimal control setup. Mechanistic models necessary for the optimization framework are derived as differential equations that describe the dynamic variation of resources (feed, water, O2 etc.), energy, and larval biomass. In addition, the elevated metabolic activity of larvae corresponding to the final instar development is identified and also modelled based on the observation from experiments. The mass and energy balance approach used in modelling enables the quantification and distinction of the mass and energy flux components in various levels (e.g. larvae body, growing medium, production environment, and external environment) while holding its applicability for both open and closed/reactor based production setups. Finally, the trajectories generated using the synthesized optimal controller are tested under different scenarios showcasing significant reduction in resource consumption compared to a constant set-point operation of the production setup. Results presented in this work not only showcase the potential of the mechanistic models and their application in identifying the relevant process parameters (e.g. reactor properties such as volume, thermal conductivity, actuator capacities), but most importantly in optimizing the process dynamically and tuning the process objectives as desired (e.g. maximize larvae mass, reduce energy).

Estimating degree-day factors of snow based on energy flux components

Abstract. Meltwater from mountainous catchments dominated by snow and ice is a valuable source of fresh water in many regions. At mid-latitudes, seasonal snow cover and glaciers act like a natural reservoir by storing precipitation during winter and releasing it in spring and summer. Snowmelt is usually modelled either by energy balance or by temperature-index approaches. The energy balance approach is process-based and more sophisticated but requires extensive input data, while the temperature-index approach uses the degree-day factor (DDF) as a key parameter to estimate melt of snow and ice merely from air temperature. Despite its simplicity, the temperature-index approach has proved to be a powerful tool for simulating the melt process especially in large and data-scarce catchments. The present study attempts to quantify the effects of spatial, temporal, and climatic conditions on the DDF of snow in order to gain a better understanding of which influencing factors are decisive under which conditions. The analysis is based on the individual energy flux components; however, formulas for estimating the DDF are presented to account for situations where observed data are limited. A detailed comparison between field-derived and estimated DDF values yields a fair agreement with bias = 0.14 mm ∘C−1 d−1 and root mean square error (RMSE) = 1.12 mm ∘C−1 d−1. The analysis of the energy balance processes controlling snowmelt indicates that cloud cover and snow albedo under clear sky are the most decisive factors for estimating the DDF of snow. The results of this study further underline that the DDF changes as the melt season progresses and thus also with altitude, since melting conditions arrive later at higher elevations. A brief analysis of the DDF under the influence of climate change shows that the DDFs are expected to decrease when comparing periods of similar degree days, as melt will occur earlier in the year when solar radiation is lower, and albedo is then likely to be higher. Therefore, the DDF cannot be treated as a constant parameter especially when using temperature-index models for forecasting present or predicting future water availability.

Review on Thermal Energy Audit of Pyro-Processing Unit of a Cement Plant

Energy consumption in cement factories is an important issue for the government as well as private organizations. The cement manufacturing industrial sector has become the worldwide energy consumer accounting for over 40% of overall energy consumption by the industrial sub-sector. Most of the thermal energy consumption by a cement manufacturing plant occurs in the Pyro-processing unit. Thus, the energy audit of the cement plant is an essential exercise to promote energy retrofitting measures. The aim of the energy audit is to reduce energy consumption in the plant, reduce energy costs and identify possible Energy Conservation and Management Opportunities (ECMOs). The aim of this study was to review the techniques of energy auditing which include Mass (Material) balance and Energy balance by considering energy conservation in the form of thermal energy that helps to fill the gap in energy efficiency improvement, policy development, and environmental analysis. Using the operational data of Kiln system of Messobo Cement obtained from the literature, the heat losses were quantified for major energy consuming components of the system using both the mass and thermal energy balance approach. The production line's capacity for clinker was 145.4 tons per hour, and both burners received a combined 25 tons of coal per hour. Energy balance tests were conducted in all areas of the pyro processing systems, and the findings revealed significant energy losses from the surface of the kiln systems, kiln exhaust, and cooler exhaust.

Prediction of cavitation dynamics and cavitation erosion around a three-dimensional twisted hydrofoil with an LES method

The Large Eddy Simulation (LES) method coupled with a Schnerr and Sauer cavitation model was adopted to simulate the unsteady cavitating flow around a Delft Twist 11 (Twist11) hydrofoil. We proposed a novel aggressiveness indicator to predict the risk of cavitation erosion on the hydrofoil surface by utilizing LES simulations as input. The proposed aggressiveness indicator introduces the time-averaged pressure, the hypotheses of Nohmi et al. and the concept of the power exponent into the energy balance approach. The results show that the current numerical method integrally reproduces the evolution of the cloud cavity observed in the cavitation tunnel. The cavitation erosion risk predicted by the aggressiveness indicator ⟨e1⟩n=5′ agrees well with the erosion pattern obtained from the paint test. The predicted erosion risk regions are located in the “hoof” positions (region 2 and region 3) of the horse-shoe-shaped cloudy cavity and the positions (region 1) near the cavity closure line.

Feeding of the Amphipod Gammarus aequicauda in the Presence of the Planktonic Cladoceran Moina salina and the Benthic Chironomid Larvae Baeotendipes noctivagus

The energy balance approach helps to understand the limits within which the ‘predator–prey’ relationship can form, but cannot explain the formation of trophic links in natural multispecies systems. A time balance approach to the study of feeding has been developed to complement it. In the hypersaline Lake Moynaki (Crimea) which has a simple food web, there is one omnivorous species, Gammarus aequicauda, and two abundant prey, planktonic Moina salina and benthic Baeotendipes noctivagus. The size of M. salina ranges from 1.0 to 1.2 mm, and the size of B. noctivagus larvae from 9.0 to 10.0 mm. In experiments, elements of time balance were evaluated during feeding of G. aequicauda in the presence of both prey species, i.e., the duration of time spent searching before capture, handling prey, and resting between attempts to eat a chironomid larva. In all experiments, G. aequicauda consumed both kinds of prey. The maximum predation rate of G. aequicauda on the smaller sized M. salina was limited by searching and handling time, but on the larger B. noctivagus it was limited by digestion time. Feeding solely on chironomid larvae may well satisfy the energy needs of G. aequicauda. However, the food ration of G. aequicauda may be 50% higher if it feeds in the presence of both prey species than if feeding only on chironomid larvae. The presence of chironomid larvae more than halved the consumption of M. salina, compared to when cladocerans were the only prey.

Parametric Study on Ammonia-Based Loop Heat Pipe

The loop heat pipe (LHP) is a two-phase heat transfer device used for thermal management in applications like space, mobile, laptop, electronic cooling. In the present study, modeling and parametric analysis of LHP was done by applying energy balance approach at different sections using Dev-C++ software. The effects of various parameters like sink temperature (5 °C, 10 °C, 22 °C), condenser effectiveness (0.4–0.9), vapor line diameter (0.0043 m, 0.0053 m, 0.0063 m), wick thickness (0.0073 m, 0.0048 m) and wick porosity (40%, 60%, 80%) were studied on the performance of LHP. The results obtained were validated with the results published in the literature. With increase in condenser effectiveness from 0.40 to 0.90, steady state operating temperature got decreased by 4.5 °C at a heat load of 600 W. The studies on wick porosity revealed that it has significant effect on the heat leak from evaporator to compensation chamber and the lower porosity leads to higher heat leak. From the analysis, an optimum performance of LHP was observed with 60% wick porosity, 0.0073 m wick thickness, 5 °C sink temperature, vapor line diameter of 0.0053 m and condenser effectiveness as 0.9 among the various parameters under investigations.

The effect of single and hybrid nanofluids in the performance of Solar Water Heating System

In the present study, the feasibility of using single particle Cu and hybrid Cu/Al2O3 nanofluids as heat transfer fluids in a coupled solar parabolic trough collector-heat water storage tank for domestic absorption cooling systems. A computer program based on one dimensional implicit finite difference method and energy balance approach has been developed to investigate the behavior of the studied system under the real climate conditions of a typical summer day in Adrar city, Algeria. The simulation findings reveal that solar parabolic trough collector with small area of 6m² and storage tank of 0.3m3 can ensure higher storage tank temperature able to drive an absorption cooling machine. Solar system with hybrid nanofluid shows superior performance compared to single nanofluid and pure water. Furthermore, the effect of nanoparticle's volume fraction is evaluated. The heat storage tank temperature can attain starting operating chiller temperature more rapidly with small volume fraction equal to 0.2% in the case of Cu-Al2O3/Water hybrid nanofluid.

Modeling of the cutting front profile in abrasive water jet machining based on the energy balance approach

High-speed abrasive water jet machining (AWJM) is a universal tool for manufacturing engineering materials. However, the application of AWJM is greatly limited due to the jet lag value caused by the cutting front profile. This paper proposes a new method to predict jet lag values at different cutting depths. The novelty is that a simplified mathematical model of the cutting front profile is developed based on the energy balance theory. Two groups of experiments were conducted to investigate the influences of process parameters on the jet lag value and the dissipated energy during cutting. The numerical regression method is adopted to obtain the energy dissipation function, which has taken the key parameters such as material property, cutting depth, traverse speed, and the initial water jet energy into consideration. The predicted curves are compared with experimental results under different operating situations with the least value of R2 = 0.9136 and the maximum deviation in percent of 16% at the jet exit point. The proposed method contributes to further research on product distortion in abrasive water jet cutting.

Thermal model of InSight solar panels in Martian conditions

InSight is a NASA mission designed to explore inner Mars and measure its seismology, heat flow, and reflexes. Apart from that, the thermal environment study is an essential mission objective. InSight landed on 26 November 2018 on Mars. As a power source, InSight has two solar panels and auxiliary sensors that monitor the solar panel temperature. A thermal model has been developed for InSight's solar panels. This model uses the energy balance approach to analyze the heat transfer processes, identify the heat transfer interactions, and determine the thermal effects of the solar panels in its Martian surroundings during a sol. In addition, the model uses Mars Climate Database (MCD) to complement input and in-situ data of the InSight solar panel to validate the results. The results show that the solar panel interacts with its Martian local surroundings, both the Martian air and the ground. Thus, these interactions might be a disturbing factor in temperature measurements. This fact should be studied more in-depth in future work.

Understanding model spread in sea ice volume by attribution of model differences in seasonal ice growth and melt

Abstract. Arctic sea ice is declining rapidly, but predictions of its future loss are made difficult by the large spread both in present-day and in future sea ice area and volume; hence, there is a need to better understand the drivers of model spread in sea ice state. Here we present a framework for understanding differences between modelled sea ice simulations based on attributing seasonal ice growth and melt differences. In the method presented, the net downward surface flux is treated as the principal driver of seasonal sea ice growth and melt. An energy balance approach is used to estimate the pointwise effect of model differences in key Arctic climate variables on this surface flux and hence on seasonal sea ice growth and melt. We compare three models with very different historical sea ice simulations: HadGEM2-ES, HadGEM3-GC3.1 and UKESM1.0. The largest driver of differences in ice growth and melt between these models is shown to be the ice area in summer (representing the surface albedo feedback) and the ice thickness distribution in winter (the thickness–growth feedback). Differences in snow and melt pond cover during the early summer exert a smaller effect on the seasonal growth and melt, hence representing the drivers of model differences in both this and in the sea ice volume. In particular, the direct impacts on sea ice growth and melt of differing model parameterisations of snow area and of melt ponds are shown to be small but non-negligible.

Diverse Soliton Structures of the ( 2 + 1 )-Dimensional Nonlinear Electrical Transmission Line Equation

In this work, the ( 2 + 1 )-dimensional nonlinear electrical transmission line equation (NETLE) is investigated by applying three recent technologies, namely, the variational approach, Hamiltonian approach, and energy balance approach. Diverse exact soliton solutions such as the bright, bright-like, kinky bright, bright-dark soliton, and periodic soliton solutions are successfully constructed. The outlines of the different solutions are shown in the form of the 3-D plot with the help of the Wolfram Mathematica. It reveals that the used methods are concise and effective and are expected to provide some inspiration for the study of travelling wave solutions of the PDEs in physics.

Surface design of superhydrophobic parallel grooves for controllable petal bouncing and contact time reduction

This study numerically investigates the bouncing characteristics of impacting droplets on superhydrophobic sub-millimeter parallel grooves by the level-set method. Once the Weber number (We) is increased to a critical value (Wec), a unique petal-like droplet bouncing off the parallel grooves without horizontal retraction is found, dramatically reducing the contact time (tc) by up to ∼75%. Such a bouncing mode is attributed to the rectification of capillary energy stored in the penetrated liquids into upward motion. To achieve controllable petal bouncing, the coupling effects of impact velocity and surface geometric characteristics on tc and Wec are elucidated from the perspective of timescale, momentum, and energy. The numerical results indicate that narrowing the center-to-center spacing contributes to shortening tc and slowing down the growth of tc with We. In contrast, the effect of ridge height is negligible. By establishing the model of emptying time, the relationships of tc with impact velocity and geometric parameters are quantitatively identified. Furthermore, along with the strengthened anisotropic property, a large center-to-center spacing promotes the conversion of horizontal momentum into vertical momentum and suppresses the increment of surface energy, thus inducing the reduction in Wec. Distinct from known anisotropic surfaces in the previous work, the anisotropic property of parallel-grooved surface plays an opposite role in shortening tc. Finally, incorporating the energy balance approach, a semi-empirical model is developed to predict Wec, exhibiting good agreement with present simulation. This work provides physical insights into petal bouncing and inspires the design of textured surfaces to reduce contact time.