Average Energy Conservation Research Articles

Computational Fluid Dynamics Analysis of the Influence of Diameter at Inlet 2 on Heat Transfer and Fluid Flow in the Mixing Elbow

This study presents the CFD (Computational Fluid Dynamics) analysis of the mixing elbow by determining the influence of the variation in the diameter of the inlet 2 section, Diameter 2 with the use of the ANSYS FLUENT software. The flow of our problem being turbulent, was described by the Reynolds Averaged Navier-Stokes Equations (RANSE), the k-ε closure model and for the temperature field, the averaged energy conservation equation. To solve them numerically, the finite volume method and the SIMPLE scheme for Pressure-velocity coupling were chosen. The larger the Diameter 2, the more effective mixing areas, the more uniform the temperature and velocity at the outlet and the better the mixing. At the outlet, not only do the velocities and temperatures increase but their gradient also increases with an increase in Diameter 2 up to 0.025m, the presence of turbulence and the rate of heat transfer increase. For Diameter 2 equal to 0.030m, the curves are symmetrical, the temperature and velocity values ​​vary slightly over the entire outlet section, we have a better mixture but with a low heat transfer rate.

A transfer-learning-based energy-conservation model for adaptive guided routes in autonomous vehicles

Autonomous vehicles (AV) are expected to improve road safety and reduce traffic congestion by optimizing routes and reducing human errors. AVs have the potential to increase accessibility for people with disabilities and reduce the environmental impact of transportation. AVs require radio transmitters to communicate with other vehicles and infrastructure, external charging to power their electric motors, and communication equipment to receive real-time data about traffic and road conditions. Additionally, these requirements must be met for AVs to operate efficiently and conserve energy. Therefore, this work introduces a novel technique called energy-conservation guided route adaptation (EC-GRA) that aims to enhance the energy efficiency of connected vehicles. With the balance in energy adaptation for distinct purposes, the utilization rate is adjusted for communication and navigation. The complex decisions are confined to the energy availability and conservation factors required in an adaptive driving condition. This technique employs transfer learning to update the available and adaptable energy ratios under displacement-based route adaptations. In the learning process, the transfer and update states for displacement-aware decisions under varying scenarios are modeled. This study validates the state transitions involved in recommending energy utilization during both autonomous and guided driving scenarios. The results show that the proposed methodology exhibits superior performance compared to the currently available techniques. The EC-GRA under consideration has demonstrated an average energy conservation ratio of 45.58. The decision rate for this method is 0.63/navigation, while its energy utilization is 126.37 Joules. The number of failures observed in the proposed EC-GRA is 6/navigation, which represents an improvement over the existing approach.

Derivation and stability analysis of two-fluid model equations for bubbly flow with bubble oscillations and thermal damping

The two-fluid model with bubble oscillations, proposed by Egashira et al. (2004), can explain the properties of cavitating bubbly flow and pressure wave propagation in the bubbly liquid. However, the viscous effect as well as energy conservation leading to temperature changes inside the bubble with bubble oscillations have not yet been considered. Hence, this study aimed to incorporate the viscous (bulk viscosity and drag) and thermal effects to the previously proposed two-fluid model with bubble oscillations. Bulk viscosity was considered by averaging the shear stress term in the single-phase momentum conservation for a Newtonian fluid, and the drag was introduced by transforming the interfacial shear stress. We derived the averaged energy conservation for a general two-phase flow with a thermal conduction inside bubbles and heat transfer between the two phases, and limited this equation to that for a bubbly flow by closing the interfacial temperature gradient term via constitutive equations for a single bubble. Furthermore, we investigated the stability of our proposed one-dimensional model equations using the dispersion analysis. This analysis provided the following insight: (i) The difference in the temperature gradient models had a slight effect on the stability of the proposed model equations; (ii) the thermal conduction inside the bubbles was dominant in the thermal damping in bubbly flows rather than the heat transfer between the two phases; (iii) incorporating both the bulk viscosity and drag stabilized the proposed model equations. Our results provide insights into the development of mathematical models to investigate the thermal effects in bubbly flow with bubble oscillations, such as cavitating bubbly flow and wave propagation in bubbly liquids.

Life cycle assessment and sustainable production evaluation of calcium carbide industry in China

With the rapid development of the calcium carbide (CaC2) industry in China, the growth in CaC2 demand is confronting an increasing pressure to reduce environmental emissions. However, the environmental impacts of CaC2 production remain poorly understood. Life cycle assessment is employed in this study to provide a comprehensive analysis of the environmental performance of CaC2 production in China. The results show that the environmental load of the semi-closed furnace process is higher than that of the closed furnace process. Electricity supported by thermal power is the most sensitive factor. A significant regional layout of CaC2 production, adjoining the coal-electricity-intensive areas, has been observed in China. The sustainable scenarios are developed to evaluate the environmental reduction potential in terms of technical progress and electric grid improvement. It is noted that increasing the proportion of renewable power in the electric grid has obvious environmental benefits for CaC2 production. The average energy conservation and emission reduction index of CaC2 production in the northwest China is 1.81–2.10 times higher than that in the southwest China. The findings of this study will give a reference for the decision-makers to take conducive emission reduction measures for the sustainable development of the CaC2 industry in China.

Epistemic Uncertainty from an Averaged Hamilton–Jacobi Formalism

In recent years, the non-relativistic quantum dynamics derived from three assumptions; (i) probability current conservation, (ii) average energy conservation, and (iii) an epistemic momentum uncertainty (Budiyono and Rohrlich in Nat Commun 8:1306, 2017). Here we show that, these assumptions can be derived from a natural extension of classical statistical mechanics.

Optimization analysis of waste heat recovery district cooling system on a remote island: Case study Green Island

The power supply of a remote island is mainly from the diesel generator due to nature and environmental constraints for developing renewable electrical power generation. Recovering waste heat from diesel generators can reduce cost and satisfy the concurrent need for electricity, district heating or cooling on a remote island. This study investigates the optimization design of a district cooling system (DCS) on a remote island by the dynamic programming method. In a case study on Green Island, the waste heat from the diesel power plant can be recovered to drive an absorption chiller that satisfies the peak cooling load of 756 kW. The objective function of the optimization design includes the capital cost and the running cost during the period of the life cycle. The dynamic programming method is adopted to minimize the objective function, and the constraint involves the conservation of energy between the chiller and the chilled water storage tank. The results showed that a 510 kW absorption chiller and a storage tank capacity of 1978 kW-h achieved the optimization of the DCS. The averaged energy conservation rate was about 75.7%. Moreover, the electricity consumption and CO2 emission were reduced by 955.8 MWh and 675 tons per year, respectively. Based on the difference in the electricity prices of electric utility companies, the investment in the DCS is expected to have a four-year payback period. These optimization results are based on an evaluation of energetic, economic and environmental effects, which are also suitable for any kind of regions without direct access to interconnected electrical networks.

Mathematical modeling and experimental study of heat transfer in a low-duty air-cooled heat exchanger

Many plate fin and tube heat exchangers operate under low loads when the flow rate of air and water is low. The flow regime in tubes can change from laminar through transitional to turbulent. In this paper, much attention was paid to determine a semi-empirical correlation for the Nusselt number on the water-side in the transitional and turbulent range when the Reynolds number Rew is higher than 2300. A new relationship for the friction factor in the transitional flow regime was proposed. The friction factor in the transitional flow range 2300⩽Rew⩽3000 was obtained by linear interpolation of the friction factor for Rew=2300, and Rew=3000. The influence of the formula for determining the water-side friction factor in the transitional flow regime on the Nusselt number was shown. Based on experimental data, heat transfer correlations were determined for the air and water-side Nusselt numbers for the low velocity of air and water. The semi-empirical correlation for the Nusselt number on the water-side derived by integrating the Reynolds averaged energy conservation equation for turbulent flow agrees well with the empirical correlation for the Nusselt number. The heat flow rate from hot water to cold air was calculated as a function of the water flow rate using a numerical model of the heat exchanger with the correlation for the water-side Nusselt number developed in the paper to compare it with the results of the measurements. The results of the numerical simulation agree very well with the results of the measurements.

Quantum mechanics as classical statistical mechanics with an ontic extension and an epistemic restriction

Where does quantum mechanics part ways with classical mechanics? How does quantum randomness differ fundamentally from classical randomness? We cannot fully explain how the theories differ until we can derive them within a single axiomatic framework, allowing an unambiguous account of how one theory is the limit of the other. Here we derive non-relativistic quantum mechanics and classical statistical mechanics within a common framework. The common axioms include conservation of average energy and conservation of probability current. But two axioms distinguish quantum mechanics from classical statistical mechanics: an “ontic extension” defines a nonseparable (global) random variable that generates physical correlations, and an “epistemic restriction” constrains allowed phase space distributions. The ontic extension and epistemic restriction, with strength on the order of Planck’s constant, imply quantum entanglement and uncertainty relations. This framework suggests that the wave function is epistemic, yet it does not provide an ontic dynamics for individual systems.

Analytical Model of Delayed Server System (DSS) for Energy Conservation

This paper proposes a delayed server system (DSS) which regulates the number of servers in ON-state, and corresponding OFF-state servers, on the basis of queue occupancy for the sake of energy conservation. Upon arrival of demand, server allocation is delayed if predefined servers are already busy and, thus, customer is going to wait in the queue before it gets service. Hence, DSS allows us to keep some servers at least OFF for fraction of total operational, time resulting in energy conservation. We have developed the Markov chain models for DSS and M/M/n-s systems. Using the Markov chain models, the numerical evaluation has been carried out for the key performance metrics such as blocking probability and average energy conservation. Furthermore, our study has investigated and figured out the optimal configurations of delayed server system in order to maximize the energy conservation.

Earth-to-air heat exchangers cooling evaluation for different climates of Iran

Earth-pipe-air heat exchangers (EPAHEs) are viable alternatives or supplements to conventional central heating or cooling systems. In present study, to reduce the cooling load of a sample residential building; usage and potential energy conservation of a four-pipe EPAHE were studied for different climates of Iran. The evaluation of the EPAHE was based on a three-dimensional transient computational model and validated by experimental data of another research. For this purpose four cities of Iran, by different climates (Temperate, Steppe, Desert, and Snow) were selected according to climate classification map of Wladimir Köppen, and the inlet/outlet temperature of working fluid (air) for each pipe, the monthly average energy conservation, and the maximum cooling load of the building with and without the EPAHE for these cities were compared in July.As a result, the average energy conservation by the EPAHE is significantly differentin selected cities with different climates. The energy conservation shows better when the city soil, is silt in comparison with loam and clay. Also in some cases, using of EPAHE shows a negative effect on the air-conditioning of buildings. The model was developed by the FLUENT simulation program.

Saturation of THz detection in InGaAs-based HEMTs: a numerical analysis

By numerical simulations, we investigate the large-signal photoresponse of InGaAs high electron mobility transistors submitted to THz radiations. The used pseudo-2D hydrodynamic model considers electron density and velocity conservations equations. A third equation is solved, in order to describe average energy conservation or to maintain it constantly equal to its thermal equilibrium value. In both cases, the calculated photoresponse increases with the incoming power density for its smallest values. For the higher values, a saturation of the photoresponse is observed, in agreement with experimental results, only when the energy conservation is accounted for. This allows to relate the limitation of the transistor detection features to electron heating phenomenon.

The effects of critical peak pricing for electricity demand management on home-based trip generation

This paper examines electricity critical peak pricing (CPP) as a measure for controlling electricity demand at critical peak times. This pricing scheme is designed to facilitate energy conservation not only inside but also outside the home. For this study, we surveyed consumer propensity to leave the home under CPP schemes and analyzed the impact of CPP on consumer cost. The results indicated that higher prices induce a higher rate of going out, while residential conditions such as population density and access to public transportation have a relatively small impact on leaving the home and average energy conservation. However, this is not always the case for aged households with limited mobility; residential conditions have a substantial effect on this segment of the population. Combined with a reduced ability to go out, electricity pricing has a greater negative impact on aged people. These results imply that improving accessibility through transportation development and urban compaction is an effective means of saving electricity alleviating the negative impact of CPP on the aged society of the future.

Time-Dependent Model of RF Energy Propagation in Coupled Reverberant Cavities

A simple time-dependent model for the analysis of RF energy propagation in coupled reverberant cavities is presented. The cumulative buildup and full exchange of radiated electromagnetic energy between coupled spaces are important issues for electronic systems compatibility in reverberant environments such as below-deck compartments in ships and aircraft cabins and bays. Based on conservation of average energy, the general model formulation is valid for both weak and strong couplings between the cavities caused by window materials, open apertures, closed and open hatches, seams, and cable/pipe penetrations through bulkheads. Application of the model is demonstrated using time-resolved received power measurements conducted in nested reverberation chambers.

Reverberant Microwave Propagation in Coupled Complex Cavities

A simple model for the analysis of microwave propagation in coupled complex cavities is presented. The cumulative build-up and full exchange of electromagnetic energy between coupled spaces are important issues for wireless systems in reverberant environments, such as below-deck compartments in ships and aircraft cabins and bays. Based on conservation of average energy in the steady state among multiple cavities, the general model formulation is valid for both strong and weak couplings between the cavities caused by window materials, open apertures, closed and open hatches, and cable/pipe penetrations through bulkheads. Application of the model is demonstrated in conjunction with measurements conducted in nested reverberation chambers in the laboratory and in the coupled main weapons bays of a fighter aircraft.

Wireless RF Energy Propagation in Multiply-Connected Reverberant Spaces

Electromagnetic compatibility of electronic systems in reverberant environments is an important issue in the deployment of wireless communications and sensor networks in below-deck compartments of ships and in aircraft cabins and bays. The cumulative buildup and full exchange of radiated electromagnetic energy between multiply-connected reverberant spaces are examined using a simple model adapted from the field of acoustics. Based on conservation of average energy in the diffuse fields, the general model formulation is valid for both weak and strong couplings between the cavities caused by window materials, open apertures, closed and open hatches, seams, and cable/pipe penetrations through bulkheads. Physical energy loss and coupling parameters in three connected chambers are determined from an overlay of model solutions to time-resolved received power measurements, and they can subsequently be used to assess wireless emission coverage and shielding of structures in the connected spaces.

The Existence Stability and Approximate Expressions of Periodic Solutions of Strongly Nonlinear Nonautonomous Systems with Multi-Degree-of-Freedom

Based upon the conservation of average energy a theorem about the periodic solutions of strongly nonlinear nonautomous systems with multi-degree-of freedom is proved. This theorem can not only decide the existence and stability of the periodic solutions, but at the same time can also give their first-order and second-order approximate expressions.

Energy Method for Computing Periodic Solutions of Strongly Nonlinear Autonomous Systems with Multi-Degree-of-Freedom

In this paper with the use of conservation of average energy, a newmethod for computing the periodic solutions of strongly nonlinearautonomous systems with multi-degree-of-freedom is suggested. Thismethod cannot only decide the existence, but also give the approximateexpressions of the periodic solutions.

Numerical Method for Simulation of Fluid Flow and Heat Transfer in Geometrically Disturbed Rod Bundles

This paper describes briefly the computational algorithm that includes procedures to obtain finite-difference form of governing convection-diffusion equations, to generate an orthogonal mesh system for complex regions and to solve the finite-difference equation system, and several results of numerical simulation in comparison with experiment. The Reynolds and energy conservation equations for steady-state fully developed turbulent incompressible flows are discretized by the Efficient Finite Difference (EFD) scheme. Here secondary flow components are neglected. In the averaged energy conservation equation, anisotropic turbulent conductivity coefficients are employed based on the axial velocity distribution. An orthogonal mesh generation system has been developed that allows us to model the rod bundle geometry by assembling elementary mesh components generated for every typical sub-domain inside the flow channels. This procedure has been made efficient with a help of object-oriented programming techniques. By solving the derived equations on the boundary-fitted coordinates, good comparisons between calculation and measurement are presented in general for detailed distributions of the local shear stress, axial velocity and wall temperature in a hexagonal rod bundle in the presence of a dislocated rod. Discussion is also made on a discrepancy of the calculated wall shear stress from the experimental data near the narrowest gap position in this “geometrically disturbed” region.

Energy Method for Approximate Periodic Solution of Strongly Nonlinear Nonautonomous Systems

In this paper, based upon the concept of the conservation of average energy, a theorem for the periodic solution of strongly nonlinear nonautonomous systems is proved. By using this theorem not only the necessary and sufficient conditions for the existence and stability of the periodic solutions can be obtained but, at the same time, the approximate expressions for those periodic solutions can also be obtained.