Abstract

Plastic waste and organic waste in the form of biomass are possible to produce alternative energy to drive turbines in power plants by turning them on with coal in the co-firing process. This study has purpose analyzing the behavior of coal combustion with a mixture of EFB and plastic compared to the pure coal using the TGA-DSC method. Test were carried out under atmospheric conditions. Addition of biomass in mixture lower the ignition temperature (Tig) of coal. The sample with lowest Tig is C1 (Coal + EFB) with value of 257.8°C. Mixture with biomass decreasing the reactivity of coal with value Tmax is increase, C2 (Coal + EFB + PET bottle) has highest Tmax with value of 423.1°C. C2 also has highest Tbo with value of 622.5°C. From Tmax and Tbo, it showed that addition of biomass decreases the self-burning tendency and prolong the combustion

Abstract

The problem of urban waste is one of the most complicated problems in Indonesia’s big cities. Utilizing municipal waste into co-firing fuel is one way to reduce waste that accumulates and reduce global emissions. Before being used, the urban waste needs to be tested for characteristics to determine its content or its combustion characteristics. This study uses Indonesian low-rank and medium-rank coal and Solid Recovered Fuel (SRF) biomass. This observation aims to decide the effect of coal-SRF blended on slagging and fouling in co-firing using a drop tube furnace (DTF). The results obtained are SRF blending up to 15% there is no slag attached. There is slight slag attached at the blending ratio of 20% and 25%, and there is a corroded part of the plate. It can happen because SRF has a high chlorine content. Overall, it shows that co-firing coal with SRF up to 25% is still safe on slagging and fouling.

Abstract

A fast and elaborate simulation method is always essential to enhance the energy performance of a chilled water system. This study proposed a new zonal approach to divide a chilled water distribution system into different hydraulic zones. And an improved numerical solution is employed to shorten the simulation time through multi-thread parallel computation. A real chilled water system evaluated the performance of the proposed simulation method. Results indicate that the relative errors between the hourly actual data and simulation results on water pressure, flow rate, and temperature on a typical day are 2.99%, 1.89%, and 4.16%, respectively. Also, compared to the conventional solution, the average simulation time of the proposed solution is reduced to only 4.5 %.

Abstract

In this work, considering the differences of MMP in slim tube and RBA, an ANN-based technique has been developed to estimate MMP and identify the influence of different measurement methods to the predicted MMP for the compiled 193 sets of MMP data for CO2 and crude oil systems under various conditions. The 193 MMP datasets are collected from open literature, including 60 sets for slim tube and 134 sets for RBA. In addition to MMP, each group of the dataset mainly contains 12 influencing factors, which can be divided into the following five main categories, i.e., compositions of the injected gas (GCO2, GN2, GH2S, GCH4, and GHC), reservoir temperature (TR), molar fraction of each component in crude oil (LVOL, LINT, LC5-C6, and LC7+), molecular weight of C7+ oil components (MWC7+), and the method used to measure MMP (EM). The EM value of 0 indicates that the MMP is obtained through the slim tube experiment, and the MMP is measured by RBA when the value of EM is 1. To comprehensively improve the generalization ability of the model, the Bayesian optimization algorithm (BOA) was applied to optimize the model structure. Then, the developed ANN-BOA model was evaluated by comparing the prediction results with the measured MMPs and the predicted MMPs from the same model based on mixed MMP data, respectively. Compared to the existing model without taking the measurement method of MMP as input to generate the forecasting MMP data, the newly proposed model not only has the lowest overall MAPE of 6.84%, lowest overall MSE of 3.2062, and highest overall R2 of 0.9739 on the testing datasets for the three random runs, but also vividly reflect the interactive relationships of each influential factor and the MMP. Finally, the differences of MMP measured with the slim tube method and RBA method on the predicted MMP were analyzed. The results indicate that MMPs measured by RBA are generally higher than those measured by slim tube under the same reservoir conditions during pure and impure CO2 injection process, which explains why the prediction accuracy of the newly developed ANN-BOA model considering the influences of different measurement methods on MMP prediction is higher than that of the existing model.

Abstract

For the retrofit design of energy systems with mature and unchanged core components but limited test conditions, accurate flow field information for new or modified components is a fast and effective evaluation method. This article employs the gas turbine as the research object, proposing an automatic control method composed of the Newton-Raphson algorithm and the volume method to predict the 0D/3D multi-dimensional simulation performance and complete the ground test verification. The key innovation point of this article is to propose a high-efficiency, accurate, and universal multi-fidelity automatic control method that can realize the fast and low consumption modified performance evaluation of energy machinery. And it is conducive to the design and development of advanced energy machinery in the future when the component characteristics are lacking.

Abstract

CO2 flooding can effectively enhance the recovery of low-permeability reservoirs and realize CO2 storage. However, the strong heterogeneity of low permeability reservoirs makes it difficult to accurately determine the miscible state of CO2 and oil. In this study, first, a PR-EOS is modified by considering the shifts of critical properties. Second, the parachor model is coupled with the modified PR-EOS to predict the minimum miscible pressure (MMP). Third, considering the multiple contact process between CO2 and oil, a MMP prediction model based on the microscopic heterogeneity is established. Afterwards, the model calculation results are compared with the prior experimental results of CO2 flooding to verify its applicability and superiority. Finally, the model is applied to the actual low-permeability reservoir to determine the miscible state of CO2 and oil.

Abstract

Economic development and the improvement in living standards have increased residential demand for water and energy. This research uses data of different water and energy consumption from 1978 to 2020, for analyzing the evolution of residential water and energy systems in Beijing. The results show that residential water consumption increased 140%, which from 58 L/(person day) to 139 L/(person day), energy consumption increased 540%, which from 0.06 KWh/(person day) to 3.30 KWh/(person day). It was found that mopping, dishwashing, laundry, and toilet flushing have changed from manual to automatic methods, even some households have changed to intelligent methods in Beijing households, following by the consumption of water and energy end-use. Although there is a high percentage of households who have used automated ways for water heating and drinking, still 5% use manual ways. As people gradually shift from manual ways to automated or intelligent ways, water and energy consumption have also changed dramatically. By calculating and comparing the utilization of water and energy in different ways, the systemic evolutionary trends were summarized, which including energy saving, the correlated growth of water and energy, and substitution of energy for water. Also the paper provides a theoretical contribution to the management of residential water and energy consumption.

Abstract

Nano thermal insulator is a promising material in heavy oil exploitation field. Three types of nano thermal insulating materials with different pore structures were obtained and characterized by DLS, SEM and thermal conductivity. Core flooding was conducted by nano thermal insulator injection followed by steam. The results showed that the nano thermal insulators with the unique high-continuous interwoven honeycomb structure and stable bonding structure inside the frame. The optimum recovery was using 0.2 PV of 0.3 wt% nano thermal insulators, and the heat loss reduced up to 49.3% and recovery get 18.14% increase, which can substantially reduce steam consumption to ensure economic effectiveness and improve oil recovery.

Abstract

The latent heat thermal energy storage (LHTES) unit with shell and tube type is widely considered to be one of the most competitive technologies to store and use solar energy thanks to its high thermal storage density, low cost and little temperature fluctuation. The phase change material (PCM) is filled in the annular space between the inner shell and outer tube, while the heat transfer fluid (HTF) flowing through the inner tube. However, the heat transfer process during the melting and solidification processes of PCM is complicated involving heat conduction, natural convection and solid-liquid phase change, which is closely related to the geometric parameters of LHTES unit. Thus, the main purpose of the current study is to explore the effect of geometric parameters on the charging and discharging performances of the LHTES unit. Firstly, a visual experiment was carried out to observe the evolution of the solid-liquid interface and monitor the temperature variation of PCM during the melting and solidification processes. Then, a two-dimensional numerical model was established and validated by the experimental data to investigate the effect of geometric parameters on the charging and discharging performances. Four kinds of geometric parameters with different shell heights were designed and studied under the same volume and heat transfer area of PCM. Results demonstrated that during the melting process, the complete melting time increases with an increase of the shell height, vice versa for the solidification process. When the height of shell increases from 100 mm to 400 mm under the same HTF inlet temperature and flow rate, the complete melting time can be increased by 20.14% and the complete solidification time is saved by 22.87%. This means that the geometric parameters of LHTES unit should be designed carefully to comprehensively consider the weightings of the charging and discharging processes in practical applications.

Abstract

The current intensity distribution of a fuel cell is an important factor that determines its performance. A contactless method that does not affect the fuel cell and can accurately and quickly assess internal cell conditions is required to measure the current distribution. Therefore, this study proposes a simplified method to measure current distribution based on four magnetic field measurements. The proposed method demonstrates that the purge control performed in flooding during constant-current operation results in non-uniform current distribution, despite effective voltage recovery. This study shows that the method is useful to eliminate the non-uniformity of current distribution for improving long-term operation of fuel cells.