Spiral‐wound heat exchanger is high‐efficiency, intensive, energy‐saving heat exchange equipment with compact structure and widely used in petrochemical, nuclear energy and LNG industries. Due to the complicated internal winding of the tubes, heat transfer in the shell side of spiral wound tube heat exchangers has not been sufficiently studied and typical correlations available in the literature are limited in practical applications. This study presents the results of a numerical model developed to analyze the fluid flow and heat transfer inside the spiral‐wound heat exchanger of nuclear power systems. The study covered a wide range of operating conditions and geometric parameters, allowing the sensitivity analysis of heat transfer and friction performance to structural parameters and the proposal of a new heat transfer correlation for spiral-wound heat exchangers, which is compared with other correlations adopted in the literature.
Non-availability of fresh water is one of the major problems faced by humanity. Major developments in water purification technologies are needed in the current scenario at an affordable price. Different types of treatment processes are available to supply fresh water to rural and urban areas at large and small scales. However, conventional fossil-fuel powered desalination techniques consume extensive amounts of resources and can have damaging impact on the environment. Abundant, cheap and clean renewable energy sources are a promising alternative for powering modern desalination processes. The present paper focuses on an experimental study of a dish type solar concentrator for water distillation. Different types of receivers (pressurized/non-pressurized & transparent/opaque) are being tested and analysis are being made for the optimization of receiver design and to obtain maximum yield. Tests are also being performed with transparent receiver in order to execute further tests with Activated Charcoal (AC), Graphene and metal Nanoparticles dispersed water. In water quality test TDS and pH values are measured before and after the experiments.
A real-time eco-driving strategy for electric vehicles is presented with the objectives of minimizing the travel time and energy consumption. The strategy is developed following a receding horizon approach such that it can take real-time traffic flow information in terms of speed limits into account when planning the vehicle’s speed profile. The problem is tackled by dividing it into two subproblems, a travel time minimization problem and an energy consumption minimization problem. Analytic solutions to the travel time minimization problem is provided to facilitate real-time application. Simulation is done over a 10 km road to demonstrate the strategy’s effectiveness.
An experimental study was conducted on Rapid Compression and Expansion Machine (RCEM) that have similar characteristic with Compression Ignition (CI) engine for gasoline-biodiesel (GB) blend 10% and 20% by volume with varying fuel injection pressure 800-1400bar. Particularly, the aim was to study the combustion phenomena of Gasoline Compression Ignition (GCI) engine. For the various fuel injection pressure and chosen GB blends fuel. The engine compression ratio was set at 16, 1000 μs of injection duration and 12.5oBTDC Before top dead center. The results show that GB 20 have shorter ignition delay than GB 10, and by increasing the injection pressure make the auto ignition occur faster. Injection pressure also effect on thermal efficiency. Increase injection pressure from 800-1000bar increase the thermal efficiency drastically. But increase injection pressure above 1000bar make thermal efficiency decrease due the constant air capacity.
The conventional methods for methane gas recovery from hydrate sediments require high investment but with low gas production efficiency and may cause potential environment and security problems. But the novel natural gas hydrate exploitation method by CO2/H2 replacement coupling methane reforming can improve the replacement effect and reduce the cost of gas separation. However, energy consumption and energy performance have not been investigated thoroughly. This work develops a detailed process simulation model and conducts an exergy analysis for producing hydrogen from the integrated natural hydrate gas exploitation with methane reforming via two different boundaries. Results show that the exergy ratio of the integrated process is 2.06, exergy efficiency of the hydrogen production process is 72.40 %, but exergy efficiency of the integrated process is much lower, which is 26.59 %.
Nowadays, natural gas is one of the most important energy resources around the world. The natural gas is always liquefied for distant transportation. Thus, the natural gas liquefaction technologies are of great importance. In this paper, a heat-driven thermoacoustic refrigerator is introduced for natural gas liquefaction application, which consists of a thermoacoustic Stirling heat engine, a thermoacoustic refrigerator and a linear alternator. The engine can convert heat from burning a small amount of natural gas to acoustic work, which drives the refrigerator to produce cooling power at desired temperature. The linear alternator provides a suitable working impedance of the refrigerator and convert the expansion acoustic work of the refrigerator to electricity. This electrical power can be used to power the pump, fan and other equipment to perform the liquefaction process. According to the simulation, a maximum cooling capacity of 340 W @ 110 K for one unit was obtained with 213 W electrical power. And the maximum exergy efficiency combined cooling and power of 21% could be achieved comparing that of 12.7% without electricity.
Increasing global population and consumption are drivers for energy consumption. As the major part of primary energy sources are still fossil, the accumulated Green House Gases continues to raise in the atmosphere. Embedded in the strategies to achieve the UN 2030 Sustainable Development Goasl are high urbanisation rates and high annual economic growth (7 %) in emerging economies. It seems more and more obvious that the transition to more energy- and resource-efficient cities will be gradual and take longer time than expected. It is also clear that transitions have to be anchored in a local context at the urban level where all key actors take part in the planning process. Urban systems are examples of very complex systems and the study of complex systems is about understanding indirect, sometimes unwanted effects. Sweden has very ambitious goals to reduce GHG emissions. However, the path towards the goals seems very winding. In 2018 the emissions increased even when using a production-based calculation. There are still uncertainties of the main goal in Sweden since two concepts are used in the debate. One is fossil fuel free energy mix and the other renewable energy mix. Both have a focus on minimizing GHG emissions but the fossil fuel free energy mix accepts nuclear energy as a part of the mix. One of the most difficult targets is to reduce GHG emissions in the transport sector. Here we can find clear examples of conflicting goals and short- and long-term targets. Biofuels can reduce the GHG emissions but will have negative effects of biodiversity and food production. Attempts to ban diesel cars will reduce the potentials for using biofuels in the traffic sector. This paper will analyse the efforts in Sweden for developing a more sustainable energy system and draw conclusions of barriers and generalisation to other countries and also to draw conclusions around research issues needed to be explored.
The generating unit contingency shutdown accidents in the power systems are increasing around the world, which can bring huge power generation shortage suddenly and result in severe system frequency fluctuations. In this scenario, the secure and stable operation of the power system cannot be guaranteed only by traditional generating units, due to the huge generating unit inertia and insufficient operating reserve capacities. Faced with this challenge, the progressed information and communication technologies make demand response (DR) become feasible to provide contingency reserve for the power system by controlling the power consumption of demand side resources (DSRs). This paper develops the power system model considering DR, where the closed-loop and open-loop transfer functions are obtained to analyze the dynamic performance of the power system under unit contingency shutdown accidents. On this basis, the stability margins of the power system are calculated by Bode plots to illustrate that the power system can become more stable as a result of DR. The proposed models and methods are verified by the numerical studies.
Energy management strategy is important for improving fuel economic of hybrid electric vehicles. We present a deep neuroevolution based energy management strategy for hybrid electric vehicles, which learns optimal energy split strategies through evolution of its deep neural networks structure. We define the optimization objective of the deep neural networks by the fuel consumption and properties of target HEV. The deep neural networks controller is learnt through a parallel and evolution way. The simulation results on a standard driving cycles show that the proposed deep neuroevolution method outperforms the DRL based model, and achieves comparative performance to global–‐optimal method–‐dynamic programming.
The subject addressed is the fault diagnosis of the circuit breaker based on the coil current in the operating circuit. The characteristics of the coil current in the operating circuit are analyzed at length by extracting eight features. The discretization of continuous variables based on the matrix decomposition is applied to change the eight continuous features into discrete variables. Followed by that, the Bayesian algorithm is used to achieve the fault diagnosis based on the discrete variables. Finally, the accuracy of the improved algorithm is verified by the simulation results.