Технические науки. Рубрика в журнале - Бюллетень науки и практики
Статья научная
Combined with domestic and foreign literature, the research progress, key parameters and existing problems of flat-panel solar collectors are analyzed. On this basis, the thermal efficiency of flat-panel solar collectors is studied by means of experiments and numerical simulations. This paper introduces and analyzes the structural characteristics of flat-panel solar collectors. Based on the structural characteristics of flat-panel solar energy and research at home and abroad, the influence of the structural parameters of each flat-panel solar collector on the collector performance was studied. According to the heat transfer process and structural characteristics of the collector, the heat energy equation of the collector is established, and the calculation process of the heat loss of the collector is simplified according to the existing research, and the calculation of the heat loss coefficient is an empirical formula. In order to facilitate the experimental study, an efficiency factor and a heat transfer factor are introduced, and the temperature of the fluid at the inlet of the collector is used to replace the surface temperature of the heat-absorbing plate, which is difficult to measure. The calculation program is used to obtain the influence data of each key parameter of the collector on the thermal efficiency and use Origin to process the data to visualize the influence of each parameter on the thermal efficiency. On this basis, a variance analysis method is proposed to optimize the collector. Based on the PYTHON software, the calculation program is written according to the variance analysis method, and the key parameters that will greatly affect the instantaneous efficiency of the collector are combined in pairs, and the optimal collector parameter combination corresponding to the maximum instantaneous efficiency is studied. This research has a certain guiding effect on the utilization of solar energy.
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Optimizing the time costs of passenger transport of people with disabilities
Статья научная
The paper dwells on a mathematical model of the logistical system of transport services for persons with disabilities, and there have been analyzed factors that affect the time spent on their transportation. When developing methodology for optimizing the time costs of passenger transport of persons with disabilities, the following two basic transportation services have been taken into account: “Social Taxi”, which will transport only people with special health; b) vehicle system in combination with urban passenger transport, which will transport representatives of the group of people with restricted mobility together with all other passengers. The study found that in the case of insufficient accessibility to the required environment, by the increase in the demand of disabled people for transportation by “social taxi”, travel costs are increased that results in increasing total costs of the carrier. When determining the expenses of passengers, it is necessary to take into account the additional time, which the disabled persons need for boarding and alighting in buses at the stopping points, on average 2-3.5 minutes.
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Ordering and density amorphous phase of carbon-fiber polymer-matrix PTFE-composites
Статья научная
We studied the application of a mathematical model for calculating the X-ray density of a pure amorphous-crystalline polymer, taking into account the degree of ordering, crystallinity and deformation of a crystalline cell in the amorphous phase, to carbon-fiber PTFE-composites. By comparing the theoretical densities (based on the developed software) of PTFE+CF-composites system with the results of experimental densities and X-ray structural parameters, it was shown that the degree of ordering and density of the amorphous phase of the polymer-matrix PTFE-composites linearly decrease as the content of the carbon-fiber increases. The change in the degree of ordering of the amorphous phase when filler application can be considered as one of the mechanisms of formation of supramolecular structure of composite materials on the basis of amorphous-crystalline polymers.
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Organization of pulsating air flow through a heat exchanger
Статья научная
In recent years, the enhancement of heat transfer by pulsating flow has become a research hotspot. A great deal of work has been done in the past, with remarkable results, to achieve better heat transfer rates. How to improve the efficiency of heat exchanger is always a research topic. In this paper, pulsating air flow is formed by standard ventilation grille and electric actuator, and the pulsating air flow is guided through two-stage heat exchanger to study the influence of pulsating air flow on heat transfer efficiency. The experimental results show that the heat transfer efficiency can be improved by pulsating flow and the heat recovery efficiency can be reduced by increasing the flow rate of the heating medium.
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Overview of research on heat transfer technology for reinforcement of shell and tube heat exchanger
Статья обзорная
The progress made in recent years in the field of reinforced heat transfer technology of shell and tube heat exchangers in China and abroad is reviewed. The energy-saving means and results of improving the heat transfer efficiency of shell and tube heat exchangers are introduced from the experimental research and numerical simulation respectively, and the future research of shell and tube heat exchangers to strengthen the heat transfer technology is also foreseen.
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PLC controlled substation standby power form the input system
Статья научная
This paper introduces the application of Siemens S7-200 PLC in standby power supply. PLC collects the normal running state signal of the primary equipment, which is used as the starting condition and locking condition of the standby power supply automatically input. It realizes different functions through programming to adapt to different running modes. Through PLC and king view in the laboratory, I verified the operation mode. It is also increases the obstacles, enriches the content of the standby self-casting system, and realizes the simulation of the joint adjustment with PLC. It is more obvious to watch the practical application of the stand auto-casting and the diversification of its functions.
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Passive methods analysis of heat transfer intensification of high viscosity fluids
Статья научная
The article analyzes the methods of passive intensification of heat exchange processes. The dependence of hydraulic resistance for fluid flow through the heat exchanger on the value of the temperature head on it is considered. The most effective ways of improvement of heat exchange processes are defined.
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Peculiarities of customs logistics in the case of transportation in the limited space and time
Статья научная
In modern conditions, transport processes encompass not only the movement of goods from suppliers to consumers, but also a large amount of forwarding, information, customs and transactional processing operations on insurance, storage of transported goods. Transport process faces special difficulties, if it is restricted by the scope of border and customs procedures of several countries in the limited space and time. Implementation of modern principles of customs logistics in the practice of customs clearance of transport and goods in the limited space and time will allow us for improving significantly the organizational and economic sustainability of transport processes. The paper examines the trends in the use of customs logistics to simplify customs clearance of vehicles and goods in the case of transportation in the limited space and time.
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Programmable controller based piercing machine system design
Статья научная
The former mainly consists of solenoid valve actuators, sensors, programmable controllers, etc. The core of the hardware design is PLC and related wiring design; the latter is mainly through Protherm V14 to complete the programming, based on the overall architecture of the system to complete the ladder design of subroutines, program flow analysis is the software design is the focus of the final successful design of the electrical control system of the piercing machine. After system debugging and testing, the system has successfully achieved the expected goal and can meet the user's control requirements with simple and clear control logic, which can meet the mechanical piercing process requirements.
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Статья научная
As a representative intrinsic type P inorganic semiconductor material, copper (I) oxide Cu2O has been widely used in photovoltaic, catalysis, chemical industries and other fields, and has an extremely important position. For a long time, the literature on the preparation method and preparation technology of Cu2O is relatively scattered and independent, resulting in a certain degree of obstacles and difficulty in obtaining relevant technical knowledge and understanding its internal principles. Aiming at the progress and innovation of Cu2O preparation methods and technology in recent years, combined with the team’s long-term experience accumulation and research results, this article focuses on the classification, principles and characteristics of Cu2O preparation methods, and the optimization methods and development directions of Cu2O preparation technology. The outlook was carried out. This review aims to provide reference and guidance for the preparation and research of Cu2O and other related inorganic oxide semiconductors.
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Project of building: solar hot water
Статья научная
The rapid development of urbanization in China has led to an increase in high-rise residential buildings, leading to a surge in the construction industry. However, this prosperity has brought about a significant increase in energy consumption, prompting people's demand for alternative energy. As a solution to this problem, solar hot water systems are becoming increasingly popular in China. The following contents need to be considered in the design of solar hot water systems. The general solar hot water system consists of solar collectors, solar water distribution pipes and water storage tanks. The arrangement of the water storage tank and the water distribution pipe is matched with the design of the building, which has great influence on the operation of the solar energy in the building. With the rapid increase in building height and the increase in residents, the roof area has not changed. The architectural layout will have an impact on the absorption performance of solar radiation. Therefore, in order to optimize the use of solar energy, regional planning should be considered. Different solar radiant intensity and different locations of solar collectors will lead to different collection efficiency and hot water supply conditions of solar water heating systems. Throughout the entire process of architectural design, the application of solar energy technology in buildings also requires consideration of the operating area conditions and architectural style, in harmony with the architectural style.
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Статья научная
Among the alternative energy sources, of particular importance is hydrogen energy, which is likely to address the acute environmental problem of large cities in the near future, in terms of pollution of the environment, first of all, of air pollution from vehicles. Among hydrogen-containing raw materials, which can be used in a fuel component, hydrogen sulphide is of particular importance. It is well-known that the Black Sea the largest basin on the planet by the amounts of hydrogen sulphide dissolved in water. In that regard, the Black Sea is the object of the attention of scientists, since its deep waters contain hydrogen sulphide, hydrosuphide and suphide ions in large quantities. The sources of their origin are gases erupted from the volcanic and geological splits existing at the bottom of the sea, as well as organic substances and products of decomposition of microorganisms brought down by the rivers. In this regard, the Black sea may become a potential source of hydrogen energy, and simultaneously that may improve environmental situation in the Black Sea. The paper analyzes the challenges existing in the use of hydrogen obtained from hydrogen sulphide of the Black Sea, as an alternative fuel in the internal combustion engines of vehicles, as well as the prospects for addressing these challenges.
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Prospects of soft fresh cheese production in Kazakhstan
Статья научная
In this article, the relevance of increasing the production of cheeses on the domestic market of the Republic of Kazakhstan is shown. In accordance with changes in the structure of the population’s nutrition and protein deficit, increasing attention is being paid to increasing the use of protein resources for food purposes, including the creation of new products. According to the Food and Agriculture Organization of the United Nations, the volume of world cheese production is constantly increasing. When polling the population in recent years it became clear that the cheese-curd market is waiting for the local producer. Therefore, the concept of development of low-cost cheeses remains to be topical - with high yield and accelerated maturation periods, which will be analogues of import-brand brands. The advantages of organizing the production of soft fresh cream cheese and cheese products of this type for domestic cheesemakers lie on the surface: this is a relatively new product for our market, soft cheeses have an extremely high yield, which makes their products very cost-effective, and this kind of cheese now has steady and constantly growing demand. The difference between fresh soft cheeses is that they are not pressed in production, the dairy raw material is gentle heat treatment, thanks to which useful substances remain intact in cheese. Proceeding from this, it can be concluded that the innovations and increase in the production of soft fresh cheese are real and possible and necessary.
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Pulsating enhanced heat transfer
Статья научная
The paper mainly introduces the mechanism of turbulent fluid heat transfer enhancement and the factors affecting heat transfer. The physical parameters of pulsating fluid mainly include pulsation frequency and amplitude. The factors affecting heat transfer are the physical properties of the pulsating fluid and the installation of a pulsation generator. The position, the type of pulsation occurrence, the natural frequency of the heat exchange system, etc.; the methods for strengthening the pulsating heat transfer characteristics mainly include disturbing flow elements, changing the size of the flow channel structure, compound heat transfer enhancement, and setting the induction vibration device in the flow channel.
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Research of acoustically improved Helmholtz resonator
Статья научная
The three-dimensional acoustic finite element method is used to predict the transmission loss of the Helmholtz resonance muffler. The results are in good agreement with the experimental results, indicating the applicability and accuracy of the numerical method used in this paper. On the one hand, in order to reduce the resonance frequency without changing the shape of the resonator, the connecting tube is extended to the inside of the resonator, and the influence of the extension length and the cross section shape of the extension tube on the acoustic characteristics of the resonator is discussed in detail. On the other hand, in order to broaden the muffled frequency band of the traditional Helmholtz resonators, the resonators are combined in series and parallel, and the influence of the combined structure on the acoustic characteristics is discussed in detail.
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Статья научная
The ship’s central cooling water system is one of the most important systems serving the main engine. With the progress of society, the design and construction of ships increasingly need to develop in the direction of environmental protection and energy-saving. Taking the 59,990 t bulk carrier as the research object , this paper proposes that based on the frequency conversion control of the seawater pump and supplemented by the energy-saving scheme of pulsation enhanced heat exchange, the frequency conversion control of the seawater pump is realized by adjusting the speed according to different working conditions. At this time, adding pulsation enhanced heat transfer technology can generate forced convection, increase the turbulence of the fluid in the tube, and introduce convection into the boundary layer, and at the same time produce cavitation, which can improve the heat transfer efficiency of the equipment. After using the seawater pump frequency conversion control and pulsation enhanced heat exchange program, the energy consumption is about 36% of that before the system was installed. The data shows that the program achieves the purpose of environmental protection and energy-saving and has a certain reference value for engineering research.
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Research on modeling and simulation of doubly fed induction wind turbine based on MATLAB/Simulink
Статья научная
This paper first introduces the structure of doubly fed wind power generation system and the working principle of doubly fed induction generator in detail and establishes the corresponding mathematical model of doubly fed wind power generation unit. The control part of wind power generation system based on doubly fed induction generator includes rotor side control and stator side control. The rotor side control adopts the vector control strategy based on stator flux orientation of the double-fed induction generator connected to the grid, and the working principle is analyzed in detail, and the main part of the simulation modeling is given. Stator side control adopts vector control strategy of grid-connected inverter control, and its working principle is analyzed in detail, and the main part of simulation modeling is also given. In order to verify the correctness and feasibility of the system, the simulation experiment platform of doubly fed wind turbine under this control strategy is built by using Matlab/Simulink simulation platform, and its simulation analysis is carried out in detail.
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Research on ventilation and heat dissipation performance of trailer power station
Статья научная
The results show that the use of CFD software to simulate the ventilation and heat dissipation of the trailer power station cabin, Get the flow field and temperature field in the cabin, The position of the highest temperature in the vehicle cabin can be determined quantitatively, which provides a useful reference for the design of the cabin structure of the trailer power station and the arrangement of the equipment in the vehicle. Moreover, the simulation results are in good agreement with the experimental results. It shows that the selected Realizable k-ε Turbulence Model can more accurately simulate the air flow field in the cabin of the trailer power station. It also shows that the model simplification method used in the calculation and the setting of analytical conditions are reasonable.
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Research progress of type P copper (I) oxide in the field of light energy utilization
Статья обзорная
Copper (I) oxide Cu2O, as a representative intrinsic P-type inorganic semiconductor material, has been widely used in the field of optical energy utilization, such as photovoltaic, photocatalysis, photodegradation and other fields, and has an extremely important position. For a long time, the literature on Cu2O’s application technology in the field of light energy utilization is relatively scattered and independent, resulting in a certain degree of obstacles and difficulties to obtain relevant technical knowledge and have a deep understanding of its internal principles. According to the application of Cu2O in the field of light energy utilization in recent years, it is mainly divided into three modules (photovoltaic, photocatalysis, photodegradation, photodegradation), and mainly summarizes the classification, principle and characteristics of Cu2O application in the field of light energy and prospects the optimization method and development direction of the application in the field of Cu2O light energy. This review aims to provide reference and guidance for the optical energy applications of Cu2O and other related inorganic oxide semiconductors.
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Review on nearest level modulation methods based on MMC
Статья научная
In view of the relevant situation of offshore wind power research, development and construction at home and abroad, as well as the energy crisis facing the world, we have ushered in a new opportunity and outbreak period for the development of new energy. Therefore, higher requirements are placed on the power supply, and the key technology for the design of offshore wind power flexible DC transmission high-power converters is proposed. The Modular Multi-level Converter (MMC) topology can only use a lower switching frequency to obtain higher power Waveform quality. The output voltage waveform can effectively reduce the switching loss and filter capacity and improve the efficiency and economy of the converter. Among them, the method based on Level Modulation (NLM) is usually the preferred method. This paper introduces the topology and working principle of the modular multilevel converter (MMC) in detail and describes the improved modulation method for NLM in detail. The advantages, disadvantages and application occasions of different improved modulation techniques are summarized, which provides a reference for the engineering application of MMC.
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