Heat Exchange and Hydrodynamic Characteristics of Unified Package of Cold Layer of RAH

Heating the air in the boiler air heater with the heat of fuel combustion products performs the functions of increasing the fuel combustion temperature, increasing the temperature level of gases in convective heating surfaces, improving ignition and fuel combustion conditions, increasing boiler efficiency by utilizing waste gas heat, improving fuel quality due to its preliminary supply, etc. However, the peculiarities of the process of heating the air in the air heaters do not allow to achieve a decrease in the temperature of the exhaust gases. This is due to the unfavorable ratio of heat capacities of flue gases and air, as well as corrosion and contamination of the heating surfaces of air heaters. The research of heat transfer processes and hydraulic resistance of unified package of cold layer of RAH is depicted at this work. The graphic dependence of the change in the coefficient of hydraulic resistance and Nu number for unified packages with single line of sheets and simplified profile with corrosion resistance enamel from the Reynolds number for different values of the length of the replaced areas was constructed. The unified packing of the simplified profile has increased by 1.17 times equivalent diameter and is characterized by good operational parameters and takes into account the risk of contamination of heating surfaces due to the enamel coating.

Investigating the hydraulic resistance in the flow part elements of pneumatic systems and heat exchangers

The article deals with the development of shell-and-tube heat exchangers for the needs of power engineering, based on additive technologies, in particular, selective laser sintering technology with new configurations of heat exchange surfaces. The role of heat exchangers in microturbines, the most common units of power plants of small distributed power generation, is considered. To intensify heat transfer and increase the efficiency of microturbines, it is proposed to use various configurations of flow channels of shell-and-tube heat exchangers made on the basis of additive technologies. Mathematical modeling and experimental study of a gas medium flow in the tubes of a heat exchanger are carried out. The dependences of the coefficient of hydraulic resistance between the surface of inlet and outlet of gas from tubes of various configurations on the Reynolds number are obtained. The results of the experiment allow us to conclude that the resistance of spiral-shaped tubes is slightly higher than the resistance of tubes with three ribs.

EMPIRICAL DEPENDENCE OF THE HYDRAULIC RESISTANCE OF THE WA-TER LAYER OF THE REGULAR PACKING ON THE RESISTANCE COEFFI-CIENT AND IRRIGATION DENSITY

A criterion equation for the coefficient of hydraulic resistance of a layer of regular packing was ob-tained, and a dependence was obtained that connects the hydraulic resistance of a dry and irrigated packing.

NUMERICAL MODELING TO PRESSURE DROP OF TANGENTIAL SWIRLS

The results of the study of numerical simulation of the hydraulic resistance of a vortex contact stage by the finite element method using k-ε turbulence models are presented. The dependence for calculating the coefficient of hydraulic resistance is obtained.

INVESTIGATION OF THE INFLUENCE OF THE FLOW STRUCTURE ON THE COEFFICIENT OF HYDRAULIC RESISTANCE

During the movement along a closed circuit, the working flow has to overcome a certain hydraulic resistance. Any pipeline communication has not only straight sections, but also turns, branches, for the creation of which various fittings are used. And shut-off valves are installed to regulate the flow of the working medium. All this creates resistance, so it is very important to perform a number of calculations before starting the installation of the pipeline, including determining the hydraulic resistance. This will allow to reduce heat loss in the future and, accordingly, avoid unnecessary energy consumption.

RESEARCH OF HYDRAULIC RESISTANCE OF VORTEX RECTIFICATION STAGES

The article deals with the issue of studying the hydraulic resistance of vortex contact stages for rectification equipment used for separation of alcohol-containing solutions obtained on the basis of hydrolysate of vegetable raw materials. Based on the conducted research, the dependences for determining the hydraulic resistance coefficient for axial and tangential swirlers are obtained. It is shown how the design parameters affect the change in the coefficient of hydraulic resistance. Hydraulic resistance is an important hydrodynamic characteristic of contact stages, which characterizes the energy consumption of the gas flow for the mass transfer process and determines the scope of its application in practice. Knowledge of the amount of hydraulic losses in the device is also necessary when calculating the schemes of technological strapping of the device. Currently, there are numerous data on the study of regularities in the domestic and foreign literature.

Computational and theoretical research of the injector block function

Работа посвящена расчетно-теоретическому исследованию работы блока инжекторов. Рассмотрен пароводяной струйный аппарат, который применяется в качестве средства циркуляции теплоносителя первого контура. Подвод дополнительного потока осуществляется на цилиндрическом участке с внезапным расширением сечения через перемычку. Для достижения поставленной цели разработана программа для ЭМВ, в которой смоделирована зависимость давления от нагрузки в контуре, а также проведено расчетно-теоретическое исследование влияние гидравлического сопротивления на расход перемычки. В данной работе рассмотрены только рабочие режимы, т.е. все инжекторы работают как насосы. В ходе работы было установлено, что при нагрузке в 30% увеличиваются коэффициенты инжекции пароводяного струйного аппарата, но характер работы перемычек не меняется. Так же было установлено, что расход через перемычку меняется не пропорционально коэффициенту гидравлического сопротивления перемычки. The paper is devoted to the computational and theoretical study of the injector block operation. A steam-water jet apparatus is considered, which is used as a means of circulating the primary circle coolant. The additional flow is supplied on the cylindrical section with a sudden expansion of the cross-section through the bridge. To achieve this goal, a computer program was developed that modeled the pressure dependence on the load in the circuit, and also a theoretical study of the influence of hydraulic resistance on the flow of the jumper was conducted. In this paper, only operating modes are considered, i.e. all the injectors function as pumps. In the process of the research, it was found that at a load of 30%, the injection coefficients of the steam-water jet apparatus increase, but the nature of the work of the jumpers does not change. It was also found out that the flow rate through the jumper does not change in proportion to the coefficient of hydraulic resistance of the jumper.

Substantiation of the Type of Air Switchgear of Pneumomechanical Seed Drills

Fulfillment of requirements of agrotechnics on uniformity of distribution of seeds on the area of feeding completely depends on the correct choice of a design of sowing system. Promising development of designs of row seeders is the use of pneumatic sowing systems, which is a prerequisite for increasing productivity and reducing direct costs during sowing. But, in some cases, such a technical solution leads to an increase in metal consumption of drills, complicates their maintenance. The costs of production and operation of such drills become unjustified. Various types of air switchgears are used to select air from sowing machines in vacuum pneumatic sowing systems and to distribute it over sowing machines in pneumatic sowing systems of excess pressure. Recently, in the designs of most pneumatic seeding systems of domestic and foreign drills used receiver, which has the form of a pipe, the inner cavity of which is connected to the fan. Air ducts of the same length connected to the sowing machines are adjacent to the outer side surface of the receiver. The use of the receiver simplifies the design of the pneumatic seeding system, eliminates the difference in the lengths of the air ducts and reduces their length, which eliminates their inflections in the process of the drill. The conducted researches allowed to establish the dependences, the analysis of which showed that with increasing the number of seeders the unevenness of the differences in the sowing machines increases, which leads to the unevenness of sowing the seeds. For drills with a collector, this is explained by the fact that with increasing uniformity, the variation of air duct lengths and pressure losses in them increases. In this case, an increase in the coefficient of variation of the non-uniformity of propagation is observed when the coefficient of hydraulic resistance of the sowing machine decreases, since its value becomes comparable with the coefficient of hydraulic resistance and the non-uniformity of lengths. As the coefficient increases, the effect of the unevenness of the air duct lengths weakens due to the decrease in the fraction of air duct resistance in the total resistance of the pneumatic system. For drills with a receiver, the variation in the level of rarefaction in the receiver increases with increasing uniformity, which leads to uneven distribution in the sowing machines. At the same time, a decrease in the coefficient of variation is observed with an increase in the diameter of the receiver and an increase in the coefficient of hydraulic resistance of the sowing machine. The revealed dependence finds its physical explanation in the fact that the increase in the cross-sectional area of the receiver and the reduction of air flow in the seeder leads to a decrease in air flow rate in the receiver, providing a decrease in the amount of air connected to the. Therefore, the static pressure along the entire length of the receiver is equalized. The analysis of dependences also shows that seeders with a receiver with a diameter of more than 70-80 mm have advantages over seeders with a collector in terms of air selection from seed drills. As the previous diameter of the receiver increases, this advantage becomes even more noticeable.

Optimal Shape Selection of Heat Exchangers Surfaces during Convective Heat Transfer

The article contains the results of a research in constructing of modern heat exchangers form of heat exchanging surfaces and modes of heat media flux, providing minimum area (size) of heat exchanging apparatus. Decreasing of heat-transferring area is achieved by using different techniques of intensification of convective heat exchange. Intensification of the heat exchange is accompanied by increasing of energy consumption for pumping the coolant. It is concluded that under the conditions of turbulent flow, the transport mechanism does not strongly depend on the shape of the perturbations introduced into the flow, while the tendency to approach the dependences is common to the curves for the considered surfaces, and the experimental data obtained on pipes with a periodic section of the flow cross-section along the length. Using surfaces creating channels with a greater coefficient of hydraulic resistance when creating a compact heat exchangers, which corresponds to surfaces for which the principle of trans-verse flow is realized.