Use of new similarities Bl and Blturb. to optimize the calculation and selection of heat exchange equipment for working with nanofluid coolants

The problem of correct, exact calculation and selection of the optimal heat exchange equipment at use in it of nanoliquid heat carriers was investigated in the work. Classical numerical equations, which are widely used in the calculation and selection of heat exchangers with nanofluids, especially at temperatures above 50 °C, give an error of (15–20) % or more. This leads to the fact that the selected heat exchange equipment may not work efficiently with excessive consumption of thermal energy. A new approach to heat transfer processes is considered, taking into account the theory of J. Businesque, which gives an idea of turbulent viscosity and thermal conductivity, as well as comparing the resistance of the coolant flow to the nanoparticle with surface forces and considering turbulent fluid as Newtonian. It is shown that the consideration of the behavior of a nanoparticle in a turbulent liquid coolant without taking into account surface forces is inaccurate and erroneous. The physical content of the previously obtained new numbers of similarity Bl and Blturb is considered and the possibility of their effective application in the new numerical equation obtained by us for the calculation of heat exchangers using nanofluid coolants is shown. The existing express method of estimating the efficiency of nanorluids use in heat exchangers on the basis of classical numerical equations is analyzed and a new express method on the basis of a new numerical equation and new numbers of similarity Bl and Blturb is proposed. The proposed express calculation method shows that a mixture of H2O + EG (60:40) improves the heat transfer properties of water by + 12.86 %, and a mixture of (H2O + EG (60:40) + 1.5 % TiO2) and (milk) + 0.5 % pumpkin seed oil) – by +16.75 %, which corresponds to the experiments and our calculations, and the known express method based on classical numerical equations shows a deterioration of – 4.5 % and, accordingly, by – 1.2 %. An example of calculating the optimal shell-and-tube heat exchanger according to the new algorithm when heating milk with hot water with the addition of mixtures (H2O + EG (60:40) + 1.5 % TiO2) and accordingly (milk + 0.5 % pumpkin seed oil) fully confirms the correctness of the new express –method.

Analysis of the Issue of Recovery of Low-Potential Energy at Small-Scale Energy Facilities

Studying the issues of recovery of low-potential energy at smallscale energy facilities allowed to show the promising character of the organic Rankine cycle (ORC) technology as a technology for recovery or conversion of low-potential energy.The most promising developments in the field of the use and recovery of waste heat are described regarding application of ORC, which is widely used in geothermal sources, hot water boilers, gas turbine plants. Due to the constantly growing diversity of working fluids, ORC can be used within a wide temperature range from 100°C to over 350°C. Also, developments are underway in the design of ORC generators to increase reliability of its individual system units, such as turbines and expanders. Based on the above factors, it can be concluded that with a deeper study of the problems of adopting ORC technologies, they can become a very promising direction in development of heat power engineering.It has been determined that the main factor hindering the widespread adoption of the ORC technology is associated with high cost of heat exchange equipment due to increased heat exchange surfaces. It is shown that design of mini power plants and energy centres based on the use of low-potential energy requires improvement of mathematical modelling methods to reliably determine operating modes and characteristics of each of the units. Methods for modelling evaporation and condensation systems, including turbines and expanders using organic low-boiling working fluids, should be considered among the methods that are highly sought after. The methods for selecting a working fluid for ORC devices also have a significant impact on characteristics of the installation determining the range of cycle operating temperatures and pressures. The solution of the above problems can lead to a reduction in the cost of heat exchange equipment, and, consequently, to a decrease in costs for design of ORC generators.

Experimental efficiency evaluation of the of various geometry twisted bands for heat transfer intensification in the heat-exchange channels of a nuclear power unit equipment

The paper is devoted to experimental study of heat exchange and pressure drop of channel with various geometry twisted bands. The studies were carried out in the range of operating modes parameters of the nuclear power units’ heat exchange equipment. The three different designs of intensifiers are presented in the paper. The values of heat transfer coefficient and pressure drop are obtained. The dependences of the Nusselt number (Nu) on the Reynolds number (Re) were calculated. The comparative analysis of intensifiers is made. The efficiency factor was also calculated on experimental data. The most optimal geometry form of intensifier was selected.

INTENSIFIED PLATE HEAT EXCHANGE DEVICE IN HEAT SUPPLY SYSTEMS OF THE HOUSING AND COMMUNAL SERVICES OF THE RUSSIAN FEDERATION

Statement of the problem. The problem of intensification of heat exchange processes in a plate heat exchanger on the basis of the HH№ 02 heat exchanger of the Ridan company is discussed. It is essential to carry out an analysis of the existing methods of intensification of heat exchange processes in plate devices according to the results of the analysis to choose the most promising method of intensification of heat exchange process and based on it to develop a patent-protected design of a heat exchange plate. Laboratory tests of the intensified plate heat exchanger with increased turbulence of the coolant are performed. The results of thermal tests on a specialized laboratory installation of the resulting and the serial heat exchanger are presented.Results. The results of the comparison of experimental studies of the intensified plate heat exchanger with the increased turbulence of the heat carrier and the serial plate heat exchanger of identical heat power are shown. The graphs of dependence of the heat transfer coefficient, which is the major characteristic of the operation of heat exchange equipment, on the average temperature pressure are designed. Conclusions. As a result of the laboratory tests in the specialized laboratory of BSTU named after V. G. Shukhov and research at the Voronezh State Technical University established a rise in the heat transfer coefficient due to the increased turbulence of the coolant flow, which causes a decrease in metal consumption and reduces the cost of heat exchange equipment.

Intensified Plate Heat Exchange Device in Heat Supply Systems of the Housing and Communal Services of the Russian Federation

Постановка задачи. Рассматривается задача интенсификации теплообменных процессов в пластинчатом теплообменном аппарате на базе теплообменника НН№ 02 фирмы Ridan . Необходимо выполнить анализ существующих методов интенсификации теплообменных процессов в пластинчатых аппаратах, по результатам анализа выбрать наиболее перспективный метод интенсификации процесса теплообмена и на его основе разработать патентозащищенную конструкцию теплообменной пластины. Выполнить лабораторные испытания интенсифицированного пластинчатого теплообменного аппарата с повышенной турбулизацией теплоносителя. Сравнить результаты теплотехнических испытаний на специализированной лабораторной установке разработанного теплообменника и серийного. Результаты. Приведены результаты сравнения экспериментальных исследований интенсифицированного пластинчатого теплообменного аппарата с повышенной турбулизацией теплоносителя и серийного пластинчатого теплообменника одинаковой тепловой мощности. Построены графики зависимости коэффициента теплопередачи, являющегося основной характеристикой работы теплообменного оборудования, от среднего температурного напора. Выводы. В результате лабораторных испытаний в специализированной лаборатории БГТУ им. В. Г. Шухова и исследований в Воронежском государственном техническом университете установлен прирост коэффициента теплопередачи за счет повышенной турбулизации потока теплоносителя, что приводит к снижению металлоемкости и уменьшению стоимости теплообменного оборудования. Statement of the problem. The problem of intensification of heat exchange processes in a plate heat exchanger on the basis of the HH№ 02 heat exchanger of the Ridan company is discussed. It is essential to carry out an analysis of the existing methods of intensification of heat exchange processes in plate devices according to the results of the analysis to choose the most promising method of intensification of heat exchange process and based on it to develop a patent-protected design of a heat exchange plate. Laboratory tests of the intensified plate heat exchanger with increased turbulence of the coolant are performed. The results of thermal tests on a specialized laboratory installation of the resulting and the serial heat exchanger are presented. Results. The results of the comparison of experimental studies of the intensified plate heat exchanger with the increased turbulence of the heat carrier and the serial plate heat exchanger of identical heat power are shown. The graphs of dependence of the heat transfer coefficient, which is the major characteristic of the operation of heat exchange equipment, on the average temperature pressure are designed. Conclusions. As a result of the laboratory tests in the specialized laboratory of BSTU named after V. G. Shukhov and research at the Voronezh State Technical University established a rise in the heat transfer coefficient due to the increased turbulence of the coolant flow, which causes a decrease in metal consumption and reduces the cost of heat exchange equipment.

THERMAL INTEGRATION OF COMPRESSION REFRIGERATION UNITS IN DAIRY FACILITIES

The heat integration of an ammonia compression refrigeration unit, that is used in different dairy facilities, was carried out by the pinch analysis methods. The schematic diagram of such unit with a cooling capacity of 1000 kW was taken as a basis. The main cycle temperatures, refrigerant consumption and its specific heat capacity were calculated for a given refrigerating capacity. Based on these data, a stream table was formed, that included a hot stream of a refrigerant – ammonia – and also two cold streams: water for chemical water treatment and water for technology. The hot stream of ammonia was divided into three streams: cooling of ammonia vapors, condensation and subcooling. Heat capacities flowrates and heat loads (stream enthalpy change) of the streams were determined. The minimum temperature difference in heat exchangers DTmin = 8°С was determined on the basis of technical and economic calculations for this process. The composite curves were plotted for the minimum temperature difference. The pinch temperatures were determined by the problem table algorithm for the hot and cold streams. The minimum values of hot and cold utilities load (QHmin and QСmin) were determined. The heat recovery capacity was determined, which was 701.8 kW. A grid diagram was built and heat exchangers are arranged in accordance with CP and N rules. The retrofit of process flowsheet is proposed on the basis of the grid diagram that includes the installation of three heat exchangers, one cooler and two heaters to achieve the target temperatures and flow rates. The use of Alfa Laval plate heat exchangers is proposed as heat exchange equipment. The payback period of the design is about two years.

Matrix method to solve the inverse problem of heat transfer in heat exchangers

Along with verification calculations of known designs of heat exchangers, in design engineering and when we develop new technologies, design calculations are necessary to solve the inverse problems of choosing the optimal designs and operating modes of equipment. Previously, the formulation and solution of inverse problems of classification and unsteady heat conduction have been considered, while the inverse problems of heat transfer in the design of heat exchange equipment are poorly presented in the literature. The development of methods to solve inverse problems in the design of heat exchange equipment is an urgent task of power industry. Matrix models of heat transfer based on mass and energy balance equations are used to formulate and solve inverse problems of heat exchange systems. Methods of mathematical programming are applied to solve inverse and optimization problems. For design calculations, a matrix method to solve inverse problems for choosing the design of devices and parameters of heat carriers that ensure the effective operation of the system is proposed. The inverse problem is formulated for the case of the sliding boundary of the beginning of the phase transition with the countercurrent type of movement of heat carriers. The obtained results can be used in power energy, chemical and food industries to improve the efficiency of designing resource-and energy-saving technologies. The solutions obtained can be implemented when developing measures to improve resource and energy saving technologies.

Eddy Current Experience of Pipe NPP Heat Exchange Equipment Testing

The article describes the results of the application of the eddy current method for nondestructive testing of heat-exchange tubes at operating NPPs. Typically tubes are produced of copper-nickel alloys and stainless steel. For the purpose of examining tubes of different materials eddy current probes of different types were used in order to increase reliability and precision. In order to obtain information on real flaw dimensions tubes were cut and examined using metallography equipment.

Development of a methodological approach for the computational investigation of the coolant flow in the process of the sodium cooled reactor cooldown

A methodological approach has been developed for the computational investigation of the thermal-hydraulic processes taking place in a sodium cooled fast neutron reactor based on a Russian computational fluid dynamics code, FlowVision. The approach takes into account the integral layout of the reactor primary circuit equipment and the peculiarities of heat exchange in the liquid metal coolant, and makes it possible to model, using well-defined simplifications, the heat and mass exchange in the process of the coolant flowing through the reactor core, and the reactor heat-exchange equipment. Specifically, the methodological approach can be used for justification of safety during the reactor cooldown, as well as for other computational studies which require simulation of the integral reactor core and heat-exchange equipment. The paper presents a brief overview of the methodological approaches developed earlier to study the liquid metal cooled reactor cooldown processes. General principles of these approaches, as well as their advantages and drawbacks have been identified. A three-dimensional computational model of an advanced reactor has been developed, including one heat-exchange loop (a fourth part of the reactor). It has been demonstrated that the FlowVision gap model can be applied to model the space between the reactor core fuel assemblies (interwrapper space), and a porous skeleton model can be used to model the reactor’s heat-exchange equipment. It has been shown that the developed methodological approach is applicable to solving problems of the coolant flow in different operating modes of liquid metal cooled reactor facilities.