Heat Exchange Equipment Research Articles

PARAMETRIC OPTIMIZATION OF HYDRODYNAMIC AND THERMAL PARAMETERS OF HEAT EXCHANGE EQUIPMENT BASED ON SIMILARITY THEORY AND DIMENSIONAL ANALYSIS

The technique of optimization of hydrodynamic and thermophysical parameters of countercurrent heat exchanger is given in the article. The presented technique is based on the usage of computational fluid dynamics (CFD) application SolidWorks Flow Simulation with subsequent approximation of the obtained data by the criterion equation based on similarity theory and dimensional analysis. It is known that the course of processes occurring in the heat exchange equipment is influenced by a large number of parameters, in particular geometric sizes, thermophysical properties of heat carriers etc. Therefore, the optimization problem is multifactorial and in order to simplify the mathematical model, it was decided to use the methods of similarity and dimension theory. As an optimization criterion was chosen the efficiency of the heat exchanger that is an integrated characteristic of the optimal operation of heat exchangers. The proposed methods of parametric optimization of geometric and mode parameters of the shell-and-tube heat exchanger, although the proposed technique can be extended to other types of heat exchange equipment. The database containing information about all the parameters of the studied models allows for multifactor analysis in MathCAD 15 application in order to establish the unknown constants of the criterion equation. The obtained criterion equation allows to quickly find the appropriate modes of operation of the heat exchanger that satisfy the conditions of the objective function.

Deposit thickness control of the heat exchange equipment by hardware and software complex

The deposits formation on heat exchange surfaces is an important problem in the thermal power industry. Since the thermal conductivity coefficient of deposits has low values, even a small layer of them creates a large thermal resistance. Deposits on the heat exchange equipment surfaces reduce the heat transfer coefficient, heat transfer efficiency, and lead to significant energy losses. To restore the operation design mode, such heat exchangers must be decommissioned and contaminated surfaces must be cleaned. Energy losses can be reduced if deposits on heat exchange surfaces are detected in a timely manner. The paper discusses a method for controlling deposits thickness on heat exchange surfaces. The method is based on the damping parameters analysis of the controlled product free vibrations. The research was carried out on models of the heat exchange equipment surfaces-steel plates 400x160x2 mm, with different deposits thickness 1 During studying of the acoustic characteristics, the natural vibrations frequencies were determined tenfold with each type of plate. Signal processing occurs in a program that allows you to receive and record data from an audio device, calculate the signal amplitude spectrum in the time domain, and return it as a value and phase (receiving the frequency spectrum). The Wilcoxon rank sum was used to determine the spectrum changes dynamics. The researches have shown that the free vibrations method allows us to determine not only the presence of deposits on the heat exchange surfaces, but also their thickness.

АКТУАЛЬНОСТЬ МОДЕЛЕЙ ЗАГРЯЗНЕНИЯ ДЛЯ ДИАГНОСТИКИ СОСТОЯНИЯ ПЛАСТИНЧАТЫХ ТЕПЛООБМЕННИКОВ

The article analyzes various theoretical approaches to describing the processes of formation of scale layers on the working surfaces of heat exchangers. The main tasks include analyzing existing models of contamination of heat exchange channels, determining the main mechanism of salt deposition on the heating surface of plate heat exchangers of heat supply systems, determining the main factors that determine the intensity of salt deposition on the working plate in accordance with the dynamics of heat and hydraulic processes in heat exchange channels formed by corrugated plates, as well as forming trends for further research. The article presents the main results of research devoted to the study of contamination processes on heating surfaces. Inaccuracies in the proposed approaches to describing the nature of the formation of salt deposition layers are identified. By generalizing existing approaches to the mathematical description of pollution processes, the main assumptions are revealed when describing the processes of salt deposition on working plates. A hypothesis is proposed about the influence of the location of channels relative to the inlet pipe on the uniformity of the flow distribution between parallel channels in the device. There is a fairly large gap between the existing computational methods for modeling pollution processes and the actual distribution of scale layers during the operation of heat exchange equipment of heat supply systems

The assessment of stressed-deformed state of tube bundle of the heat-exchange apparatus with the fixed pipe grids

Ensuring reliable operation of heat exchange equipment is the key to continuous and efficient operation of the entire technological unit or assembly as a whole. During installation, repair or operation, various deviations of the construction elements of the heat exchangers from the values specified by the project are possible. One of the possible scenarios of such deviations is the deviation of the transverse baffles of the tube bundle from the vertical design position during installation. Since the transverse baffles in the tube bundle play the role of supporting constructions, when they deviate from the vertical design position and at the same time are exposed to operational loads, it is possible to form zones of concentration of increased stresses in the heat transfer pipes, and then the occurrence of defects in these zones. Currently, the work on modeling heat-exchange equipment using specialized software systems for assessing the stress-deformed state taking into account the influencing factors and identifying the most unfavorable zones with maximum effective stresses is relevant. This paper investigates the interconnection between the magnitude and direction of deviation of the transverse baffles from the vertical design position on the stress-deformed state of the tube bundle of the heat exchanger with fixed tube grids along the rows of heat transfer tubes.

Theoretical Calculation and Numerical Simulation Based on Radial Fin of Triangular Profile

In most heat exchange equipment, in order to increase heat dissipation between solid surface and external fluid, the heat transfer surface is often made into finned form. This is because the method of increasing the surface area of the fin wall is used to reduce the heat resistance of the convective heat transfer and enhance the heat transfer. There are various types of fin wall, including straight fin, radial fin and needle fin. The radial fin of triangular profile belongs to the radial fin with variable thickness profile. Based on the theoretical calculation and numerical simulation of the excess temperature distribution and fin efficiency of the radial fin with triangular profile, the excess temperature distribution equation and the calculation formula of fin efficiency on the wall of the radial fin with triangular profile are derived, and the curve of excess temperature distribution and fin efficiency is fitted and output by MATLAB, the theoretical basis for the design and application of this kind of radial fin is provided.

Types of heat exchangers in industry, their advantages and disadvantages, and the study of their parameters

Annotation The heat exchanger as the main element in various types of energy complex is widely studied in technological and production processes. Heat exchangers are classified according to their application. Therefore, in this article we will consider the main types of heat exchange equipment, the choice of a specific type, depending on temperature, flow, pressure drop, and so on. The paper also provides a brief description of software for calculating, modeling and designing CFD, the advantages of each of the methods used to study heat transfer and its efficiency.

A review of drag reduction and heat transfer enhancement by riblet surfaces in closed and open channel flow

Turbulence and heat transfer are two critical factors in the chain of world energy consumption. Hence, development of more efficient energy transfer techniques in engineering applications through control and optimization of the thermal turbulent boundary layer and turbulence continues to be a subject of intense interest. This is why reviewing a passive flow control technique with a focus on unique characteristics of heat transfer in devices called riblets is beneficial as technology pushes to revolutionize design and manufacturing of heat exchanger equipment. Riblet surfaces are considered beneficial to many commercial applications as they reduce forces between surface and fluid, and in some cases can enhance heat transfer in the turbulent flow regime. As there is no literature study that focuses on heat transfer and riblets, the current study reports experimental and numerical investigations reviewing both drag reduction and heat transfer using riblets in closed and open channels. Drag reduction studies are limited to water and oil flow studies, and heat transfer studies are expanded to air flow studies as there are none on water or oil flow. In addition, physical mechanisms of fluid drag and convective heat transfer are discussed. This paper outlines the challenges of fabricating riblets and provides a design summary for optimal drag reduction and heat transfer. This review also looks at applied numerical methods and their accuracy in evaluating drag reduction and heat transfer over riblet surfaces. The important findings and a possible future optimization approach on riblet surfaces are highlighted as well.

The importance of thermodynamic insight in Work and Heat Exchange Network Design

Work and Heat Exchange Network (WHEN) design has been an emerging topic in the area of Process Synthesis and has attracted increasing research interest in the past few years. Not only temperature changes but also pressure changes of process streams have been taken into consideration in WHEN design. As a result, pressure changing equipment such as compressors, expanders, pumps, valves, etc., as well as traditional heat exchange equipment is included in WHEN design. Similar to HEN design problems, both graphical and mathematical optimization approaches have been under development for WHEN design. The graphical approaches utilize fundamental thermodynamic insight while mathematical optimization approaches enable dealing with large size problems. This paper focuses on a comparison between the graphical and mathematical optimization approaches for WHEN design. A case study is used to illustrate the importance of thermodynamic insight in WHEN design even in the case of using mathematical optimization approaches.

Modern methods of intensification of heat exchange processes in plate apparatuses

The heat supply system of the Russian Federation is characterized by significant wear and tear of equipment: heating networks and boilers. At the same time, an important element of heat supply systems equipment is heat exchangers of various designs, which are used in boilers, IHP, thermal power plants, and nuclear power plants. Various heat exchange equipment used in modern heat power engineering is considered. It is established that the use of plate heat exchangers is a more appropriate engineering solution than shell-and-tube heat exchangers, due to economic factors and operational advantages. The method of intensification of heat transfer of the heated liquid by means of technological depressions of spherical shape located according to the linear law is considered.

Configuration Optimization of Ultrasonic Descaling Device for Condenser Based on Solidworks-Fluent

As a key component of the open circulation cooling system, the condenser of the power plant is very prone to fouling. After the condenser cooling pipe is scaled, the heat transfer resistance increases, which reduces the heat transfer coefficient and heat exchange efficiency of the heat exchange equipment, which is not conducive to improving the energy efficiency. Therefore, the research on condenser descaling technology has attracted widespread attention. Ultrasonic descaling is a new type of online descaling technology. Its application effect in descaling of condensers in power plants has been verified by actual engineering, but it lacks optimization of the arrangement and configuration of ultrasonic devices. In order to explore the influence of various ultrasonic parameters on the descaling effect, this paper builds a 3D geometric model of the condenser in Solidworks based on the relevant structural parameters of the N-20910 condenser, meshing the model reasonably and setting the boundary conditions. Then, in Fluent, the descaling effect is characterized by the pressure change curve of the specific position of the fluid in the condenser pipe. By setting three different ultrasonic inlet modes and different ultrasonic sound pressure functions, the effects of the quantity, power, frequency and distribution of ultrasonic descaler on the internal flow field and descaling effect of the condenser are compared and analyzed. The simulation results can provide effective help for the optimization and parameter setting of the ultrasonic descaling device of the power plant condenser.

Optimization of waste heat recovery in internal combustion engine using a dual-loop organic Rankine cycle: Thermo-economic and environmental footprint analysis

In this research, a waste heat recovery system based on a Dual-loop organic Rankine cycle (DORC) was optimized for a 2 MW natural gas engine. A thermo-economic and environmental assessment was carried out to study the energy, economic, and environmental performance of the system. A sensitivity analysis was developed to study the effects of the condenser and evaporator pinch point temperature, turbine efficiency, and high evaporation pressure on the payback period (PBP), the specific investment cost (SIC), the net power output (Wnet), and the levelized cost of energy (LCOE). Similarly, a multi-objectiveoptimization method from agenetic algorithm (GA) was conducted to determine the optimum Pareto frontier solution from the thermal and economical approach. Therefore, the net power output was maximized, as the thermo-economic indicators considered using toluene as the working fluid was minimized under constrains. The results of the thermo-economic study revealed that heat transfer equipment (ITC1, ITC2, ITC3, and ITC4) represent 86.34% of the total exergy destroyed in the system, followed by pumps (P1, P2, and P3) with 11.38%. Also, the ITC1 was the heat exchanger equipment with the greater saving potential due to the high investment costs. The study also shows that the heat exchanger ITC3 was the equipment with the highest exergy cost of the system, while the others showed slight variations in the evaluated range of the variables. Finally, the bi-objective optimization made it possible to establish the optimum operating point of the thermal system that maximized the net power output at 99.21 kW, minimizing the economic indicators (PBP and SIC), where the carbon footprint obtained was the lowest (54040 kg CO2 eq) at 67.2% engine load and the highest absolute decrease in the specific fuel consumption (6.2%) at 89.4% engine load. However, with the tri-objective optimization, better results were obtained for the net power output (100.07 kW), which represented an increase of 80% respect to the bi-objective method.

О ВЛИЯНИИ СОДЕРЖАНИЯ КИСЛОРОДА НА ТЕПЛООБМЕН ПРИ ПОПЕРЕЧНОМ ОБТЕКАНИИ ПАРОГЕНЕРИРУЮЩИХ ТРУБ В РЕЖИМАХ НОРМАЛЬНОГО ТЕПЛООБМЕНА И С ЗАМОРАЖИВАНИЕМ СВИНЦА

The BREST-OD-300 steam generator project being developed at NIKIET is pioneering both in terms of the heat carrier used (lead) and in design implementation (coils of helical heat transfer tubes). The advantages of the designs of steam generators made in the form of helical coiled tubes, in comparison with straight tube designs are obvious. Helical coiled tubes are used in heat exchange equipment not only to increase the heat transfer surface, to solve the problem of thermal expansion, but also to increase the coefficient of heat transfer to the fluid flowing inside the tubes. In 2011-2017 years the thermohydraulic tests of various models of lead-heated steam generator were carried out at the IPPE SPRUT facility (IPPE). The test program was aimed to study the heat transfer and the thermal-hydraulic stability of the steam generating tubes. Throughout the entire range of changes in operating parameters, no pulsating modes were detected with overturn of circulation in the water circuit. The design temperatures of superheated steam were obtained in nominal operation. The results provide extensive information on water heat transfer in different zones of the steam generating channel under various operating conditions (nominal and partial modes, starting modes). However, to verify the computer codes, experimental data on the heat transfer of lead coolant around the bundles of heat transfer tubes are necessary. Due to the small twist angle of the tubes in a full-scale steam generator, it can be said that heat transfer is close to heat transfer during transverse flow. A model with a transverse flow of lead coolant around steam-generating tubes was developed at the SSC RF - IPPE. The main goal of the research was to obtain data on the effect of oxygen concentration in lead on heat transfer in normal heat transfer modes and with lead freezing. Throughout the entire range of changes in the initial temperature values of lead and water, blocking of the annular space by frozen lead was not recorded.

Новые материалы для энергосберегающих теплоизоляционных конструкций трубопроводов и теплообменного оборудования

Новые материалы для энергосберегающих теплоизоляционных конструкций трубопроводов и теплообменного оборудования

Suppressing SO3 formation in copper smelting flue gas by ejecting pyrite into flue.

SO3 in the copper smelting flue gas not only causes serious corrosion in heat exchange and dust collection equipment but also increases the amount of sewage acid (waste acid or polluted acid from copper smelting). In this study, we attempted to reduce the damage by ejecting pyrite into the flue to suppress SO3 formation in the flue. First, the Gibbs free energy for the chemical reactions between the substances was obtained after ejecting pyrite. Subsequently, the thermodynamic study of SO2-O2-H2O-N2-CO2-CO system was performed. Then, a kinetic study on the decomposition and oxidation behaviour of pyrite in the flue system was performed through thermogravimetric experiments. Results show that pyrite decomposition and oxidation in the flue system have a very strong oxygen consumption capacity. The SO3 formation in the copper smelting flue gas is suppressed by the consumption of oxygen in the flue to control the reaction direction of 2SO2 + O2 ⇋ 2SO3 and the partial pressure of SO3.

Application of porous materials in heat exchangers of heat supply system

Heat exchange capacity increase is one of the main concerns in the process of manufacturing modern heat exchange equipment. Constructing heat exchangers with porous metals is an advanced technique of heat exchange increase. A construction of heat exchangers with porous aluminum is described in this paper. The first heat transfer agent (hot water) flows through thin copper tubes installed within the porous aluminum. The second heat transfer agent (freon) flows through the pores of aluminum. Laboratory facility was created to study such a heat exchanger. Series of experiments were carried out. The purpose of the research presented here is to create a mathematical model of heat exchangers with porous metals, to perform analytical calculation of the heat exchangers and to confirm the results with the experimental data. In this case, one can`t use the standard methods of heat exchangers calculation because the pores inner surface area is indeterminate. The developed mathematical model is based on the equation describing the process of cooling the porous plate. A special mathematical technique is used to take into account the effect of tubes with water. The model is approximate but its solution is analytic. It is convenient. One can differentiate it or integrate it, which is very important. Comparison of calculated and experimental data is performed. Divergence of results is within the limits of experimental error. If freon volatilizes inside the heat exchanger, the heat of phase transition has to be taken into account alongside with heat capacity. The structure of the mathematical model makes it possible. The results presented in this paper prove the practicability of using porous materials in heat exchange equipment.

OPTIMIZATION OF THE DESIGN OF HEAT EXCHANGERS

The intensification of heat transfer is always given great attention to any industry and technology. A promising direction is the use of heat transfer surfaces with a large area, that is, developed, which is achieved by fining the primary surface. When using pneumatic devices, one of the ways to reduce the flow of compressed air is to preheat it in a heat exchanger.The work has developed a methodology for determining the optimal design of a compressed air heater by such a parameter as the total length of the finned tubes. In order to rationally set up an experiment to study the process of constructing the optimal design of a heat exchanger using finned tubes and to determine the stationary area in the face of changing basic factors, a second-order central compositional plan was used.The obtained optimization equation in a rather simple form allows us to analyze the influence of the main parameters on finding the minimum value of the pipe length at a predetermined value of such factors as the number of rows of pipes transverse to the flow and the length of one pipe. According to the Fisher criterion equation of the model is adequate to the true dependence with a confidence probability of 95 %. Analyzing the obtained equation, it is determined that the greatest influence on the total length of the heat exchanger tubes has the number of their arrangement transverse to the heat carrier flow. The effect of the length of one tube across the air flow is of secondary importance. Achieving a reduction in the total length of the tubes used can be by decreasing their number transverse to the flow and reducing the length of one tube.The above technique can be used to optimize any type of heat exchange equipment using developed heat transfer surfaces.

Reducing labor input of monitoring condition of heat exchange equipment surfaces

Deposits on surfaces of heat exchange equipment reduce the heat transfer coefficient, heat exchange efficiency, and lead to significant energy losses. The paper considers a hardware-software complex for monitoring the state of heat exchange surfaces. Studies were carried out using models of surfaces of heat exchange equipment – 400×160×2 mm steel plates, by the method of free vibrations. The studies have shown the possibility of using the method of free vibrations for the detection of deposits on the heat exchange equipment, which reduces energy losses and labor input of monitoring the condition of the surfaces of heat exchange equipment.

Methods for Controlling Carbonate Deposits on Heat Exchange Equipment in Nuclear Power Industry

All heat exchange equipment of nuclear power plants is subject to carbonate deposits, and especially strongly the one in which water circulates from the cooling pond. The appearance of contamination on the surface of the heat exchange leads to various consequences from a slight deterioration of heat transfer to premature wear of equipment. Increasing the thickness of contamination in heat exchangers at nuclear power plants also leads to losses of electrical power, and this is a direct economic loss. As a result, the problem of controlling carbonate deposits is very urgent and does not have a universal solution at present. The paper shows how heat exchange worsens in one month if no measures are taken. However, existing cleaning methods do not give 100% results and have their own disadvantages. This paper highlights the methods used for cleaning deposits, considers ways to increase their efficiency, and presents new ideas that were not previously used at nuclear power plants (including the Rostov NPP). These include increasing the efficiency of the ball cleaning system, reducing the salt content of the cooling reservoir, ultrasonic cleaning, and last of all, water magnetization. Their advantages over the existing ones are that cleaning is carried out during operation, there is no large waste for disposal, there is no probability of damage to the tubes, and they can be performed by the personnel of the nuclear power plant, which is less time and financial costs. The proposed ways are completely different, but they work for the same end goal, that is, to reduce pollution, reduce energy underutilization and eliminate lost profits.

Tribological properties of structural alloys for the heat exchange equipment parts subjected to fretting

Trobological characteristics of sliding friction in stainless steel and titanium alloys in dry and water lubricated conditions have been determined. The character of the coefficient of friction variation with load and the duration of tests have confi rmed the prevailing wear mechanism in these materials to be frictional fatigue fracture that in the case of titanium alloys is accompanied with adhesive interaction and plastic plowing. The frictional fatigue curves built in a result of this investigation make possible to estimate the materials tribological longevity.

Thermohydraulics of Alkaline Liquid-Metal Coolant: A Retrospective-Perspective Look

Sixty years of experience in mastering alkaline liquid metals jointly with industry institutes, the Academy of Sciences, and engineering design agencies developing Nuclear Power Facilities (NPF) has culminated in the development of the scientific foundations for their use in nuclear power and the scientific substantiation of the hydraulic parameters and highly efficient technological processes ensuring successful operation of fundamentally new NPF. The primary directions of research were the hydrodynamics of and heat transfer in channels with complicated shapes and in nominal and deformed fuel-rod assemblies, including the blocking of flow sections, and the mechanisms of turbulent heat and mass transfer, interchannel mixing of the coolant, and the hydrodynamics of collector systems in reactors and heat-exchange equipment. Significant attention was devoted to heat exchange in intermediate heat-exchangers and steam generators of reactor facilities and the boiling and condensation of liquid metals. Questions concerning the generalization and experimental thermophysical databases, development of heat pipes, thermophysics of thermionic converters, high-temperature space NPF, and thermonuclear plants were examined. Future studies resulting from the need to improve the safety, cost-effectiveness, and reliability of developed nuclear power facilities are formulated.