Abstract

The study of coal microstructure based on 3D reconstruction is of great practical significance for CBM extraction, thermal convection in situ pyrolysis, and oil and gas transport in coal seams. In this paper, oil-rich coal is scanned by CT, and then, 3D reconstruction is performed by using 3D visualization software AVIZO to establish a 3D pore structure model of oil-rich coal. Finally, COMSOL Multiphysics software is used to simulate the changes of seepage velocity and seepage path during the seepage of nitrogen in the pore space. The results show that Oil-rich coal has anisotropy; the permeability in X, Y, and Z directions is very low and shows a great difference, with the increase of N2 temperature, the effective permeability in all three directions increases; with the increase of pressure gradient, methane seepage velocity increases gradually, and the curve shows the obvious non-linear relationship.

Abstract

To study the effects of wet sludge amount on the coal-fired boiler parameters by blending flue gas dried sludge, a thermal calculation and analysis of 300 MW power plant are studied in this paper based on the energy conservation equation. Under the load of BMCR, 75%THA, 50%THA, and 30%THA, the influences on flue gas extraction ratio (extracted from low-temperature superheater outlet), thermal efficiency, and coal consumption are calculated and analyzed. The results show that blending sludge will cause the deterioration of the boiler’s main parameters. The variation increases as the boiler load and the amount of wet sludge decreases. For comprehensive consideration of engineering cost, boiler parameters and the influences on environmental facilities, the percentage of wet sludge and fuel should be controlled below 10% under different load conditions. The influence on the sludge-coal blending combustion with extracted flue gas under full load condition is revealed and a mathematical conclusion is obtained.

Abstract

Methane steam reforming is an important method of
hydrogen production. In this study, the performance of
methane steam reforming in internal spiral fin structure
reactors through the equivalent medium method has been
investigated. The efficiencies of different structure reactors
have been compared in same boundary conditions. It is found
that internal spiral fin structure reactors can improve the
efficiency of methane steam reforming. Methane conversion
rate of the structure S40 increased by up to 2% compared with
the structure Normal. Hydrogen production rate of the
structure S40 increased by up to 0.3% compared with the
structure Normal

Abstract

With the expansion of electricity spot market, there have been more factors affecting clearing prices considering renewable energy, carbon emissions trading, and others. Assessing the impact of key factors on price is beneficial to the controllability and stability of electricity prices in spot markets. Therefore, this paper proposes a method to analyze the key factors influencing price based on sensitivity analysis. Firstly, an index system is constructed to evaluate the influence on clearing price, including factors from unit cost, unit operation and system operation. To study the specific impact of various factors, a spot market clearing model considering carbon emissions trading is introduced in this paper. Finally, the sensitivity analysis method is used to compare the influence of each factor on clearing price in markets with different ratios of renewable energy. In the case study, a 39-node system is used to verify the effectiveness of the method and loads in valley-load period is proved to be the most critical factor in the market with high ratio renewable energy.

Abstract

In recent years, control of bistable flow of slit jet has attracted the interests of researchers due to its extensive applications in many fields. But there are still many problems in controlling jet flow by temperature. In order to further explore the influence of temperature on jet flow. This paper mainly carried out the numerical simulation on the control of bistable flow in a tube actuated by temperature. The slit jet was formed by two semi-circular tubes arranged side by side at different Re, different spacing ratios and different temperatures. It was found that, both spacing ratio and Re affect jet wall attachment. In case of temperature difference between the two semicircular tubes, the jet is inclined to the side at higher temperature. Higher temperature gradient corresponds to larger deflection angle and less arrival time of jet from the start point to the attached side. Setting the specific parameters, the split jet is stably attached to the side at higher temperature after running for a period of time. When the temperature of two walls is reversed, the split jet attached wall will also be conversed. This study lays a theoretical foundation for the further development of bistable characteristics of flow field and the application of dynamic thermal management devices.

Abstract

In order to absorb urban solid waste on a large scale and reduce the damage to the urban ecological environment caused by the massive accumulation of waste cellular concrete (WCC). In this work, WCC was used as skeleton material, which was pretreated, and sodium carbonate was used as phase change material to prepare shape-stable phase change materials (SSPCMs). The results show that the calcinated WCC could load with 45 wt.% Na2CO3. The melting latent heat of the SSPCM loading with 40 wt.% Na2CO3 was 20.45 J/g measured by differential scanning calorimeter (DSC) and the maximum thermal conductivity of the SSPCM measured by Laser Flash Analysis (LFA) was 0.24 W/(m·K). X-Ray diffraction (XRD) and Fourier transform infrared (FT-IR) showed that there was good chemical compatibility between skeleton material and phase change material.

Abstract

A major problem in Solar Photovoltaic (PV) based systems is the need for storage, which increases the system’s cost and complexity. In many applications like water pumping, desalination, and heating/cooling, it is only necessary to use solar energy as available due to the inherent storage capacity of these applications. In such applications, the effectiveness can be improved with proper energy management, which involves estimating the intermittent source, monitoring the loads, and reducing losses. This paper provides a solar reserve power estimate (RPE) metric for Standalone Solar Photovoltaic systems without storage which is an estimate of the availability of solar output measured with only the sensor voltage and current operating at any point. Load monitoring is implemented by non-intrusive techniques with Energy Disaggregation. Once supply and demand in a standalone system are estimated, it is possible to make intelligent decisions for maximum utilization of the Solar PV resource. A boost converter interface with PV provides the DC link voltage for the inverter. The system operation is validated experimentally for a 1kW standalone PV system.

Abstract

Compared with traditional power source vehicles, there is still a gap in the durability of fuel cell vehicles. On fuel cell vehicles, gas starvation caused by start-stop and frequent load changes is one of the significant factors that cause the fuel cell lifetime decay. Gas starvation refers to the state in which the reactant gas of the fuel cell works under substoichiometric numbers. However, due to the complexity of the fuel cell structure and reaction mechanism, the existing researches have not reached a unified and accurate diagnosis method. It is difficult to establish a clear relationship between the gas starvation state of fuel cell and its external characteristic parameters. Therefore, this paper innovatively uses the adaptive network-based fuzzy inference system (ANFIS) method in gas starvation diagnosis. In this study, a proton exchange membrane fuel cell (PEMFC) is modelled and analyzed by ANFIS. Meanwhile, CFD simulation is used as an auxiliary tool to obtain 102 samples’ data. Experimental data are obtained to verify that the steady-state response of the PEMFC is consistent with the simulation data. This research finally achieves a 92% accuracy of gas starvation prediction, and the ANFIS model can predict the size of starvation area in PEMFC cells, providing a feasible technical route for the prediction of starvation in fuel cell systems and vehicles.

Abstract

This paper introduces the stacking scheme for the flat-chip solid oxide cells (FCSOCs). The FCSOCs are easy for manufacturing and stacking, combining the advantages of planar SOCs and tubular SOCs. The FCSOC stacks are sealed at the cold-ends (around 150℃) of single cells, enabling an easy, reliable, and flexible sealing with silicone sealants.
R&Ds reveal that, however, single cells in an FCSOC stack exhibit non-uniformity caused by the distribution of operating conditions. Fully-coupled 3D stack models validated with experiments are powerful tools for investigating the non-uniformity, which, however, require high computation costs, especially for large stacks with up to about 100 cells. Inspired by that the stack model’s focus is the stack-level non-uniformity but not the cell-level non-uniformity, it is possible to simplify the fully-coupled model by ignoring cell-level non-uniformity. Therefore, a data-driven method, called the adaptive polynomial approximation (APA), is used to build surrogate models of single cells. The cell-level surrogate models are then integrated into the stack-level model to form a hybrid model that avoids computing the current distribution and fuel-side mass distribution inside the single cells. The computational cost is reduced, making it possible to simulate the models of large stacks. The simplification error is analyzed. Based on the simplified stack models, the design and operation factors inducing the non-uniformity among single cells are investigated and optimized.

Abstract

Integrated energy system can effectively improve the efficiency and economy of energy utilization, and is an effective means of realizing carbon neutralization. The configuration optimization of CCHP system based on micro gas turbine is proposed to improve the overall performance of CCHP system in economy, energy saving and environmental protection. Three operation strategies are also proposed. The results show that the optimized CCHP system performs better than the traditional SP system, and is more suitable for users with low power load and big fluctuation.