Heat Exchange Equipment Research Articles

Improvement of Efficiency of Air Cooling Devices By Creation of Independent Modules with Evolvent Profile Composition of Finned Tubes


 
 
 An analysis of the composition of the heat-exchange equipment at the petrochemical plants reveals that nominally more than 30% (and by weight about 50% of the total equipment) is heat-exchange equipment, including air-cooled units requiring replacement and reconstruction as a result of the end of their service life or corrosion erosion wear. Therefore, work aimed at improving the effectiveness of ABO is relevant. The existing problem of reducing the efficiency of air cooling in hot calm weather is compounded by the need for short-term humidification using a humidifier mounted directly behind the fan wheel when the air enters the diffuser. This dramatically increases the processes of corrosion and the formation of deposits on the surface of finned tubes (scale, fluff and dust). We have carried out a set of computational and experimental studies to evaluate the thermal efficiency of small-sized ABOs of various designs using a universal experimental industrial bench. The results of studies have established that vertical-cylindrical ABO designs are more energy-efficient and less metal-intensive compared to typical horizontal ones and allow for the influx of cold atmospheric air to the ABO inlet during the hot season.
 
 
 
 Keywords: air cooler; heat transfer coefficient; thermal efficiency; design of a vertical cylindrical air-cooling apparatus; involute profile layout
 
 
 
 
 

Hydrophobic surface-assisted SiO2/DI-water nanofluids for enhancing heat transfer and reducing flow resistance

Nanofluids for heat transfer application suffer from inevitable pump power consumption and adhesion effect with interface during flow. The hydrophobic treatment for heat transfer surface may be one of the most prospective strategies to achieve heat transfer enhancement and flow resistance reduction. However, the limitations of hydrophobic treatment technique and process make it difficult to fabricate desirable large size and high curvature hydrophobic surface. Herein, a facile displacement reaction method is applied to prepare the lath-like silver crystals and micro-nano gaps in the inner surface of copper tube with assistance of benzoic acid dispersant. The result shows that the convective heat transfer coefficient increases to 18.1% and the Darcy friction factor decreases to 4.9% at the volume concentration of 2.0% when SiO2/DI-water (deionized water) nanofluids flow through the hydrophobic surface. The hydrophobic surface-assisted strategy may provide an effective scheme for wide applications of nanofluids in heat exchange equipment.

Optimal Plate Heat Exchangers of Power Generation Systems

Plate heat exchangers are an effective type of heat exchange equipment and can be used in many power plants. The article analyzes the use of corrugated plate heat exchangers in a number of installations. Their optimization was done according to the economic criterion of optimality, taking into account capital investments and operating costs. The analysis of the plate heat exchangers uses as oil coolers (a number of loads with oil mass flow rates 10….250 kg/s) and water heaters (heat power 100…2000 kW) of steam turbine plants. It has been established that plate oil coolers are more economical than shell-and-tube ones. Also, the anti-icing system plate air heaters of gas turbine plants with a power of 1 to 20 MW considered. The air for the anti-icing system was taken after the compressor and was additionally heated by exhaust gases. It has been established that it is necessary to install an additional flue gas smoke exhauster for using plate heat exchangers. Air must be extracted after the compressor, otherwise, low air density leads to high hydraulic losses, which makes it impossible to use plate heaters. Optimum air velocities are in the range of 0.4…0.6 m/s, flue gas velocities are 4…6 m/s. The use of standard plate heat exchangers with corrugated plates is impractical for GTU powers above 5 MW. Optimization of plate regenerators of supercritical CO2 cycles with recompression for powers from 1 to 15 MW has been done. Optimum velocities of hot CO2 are about 0.8 m/s, cold ones 0.3…0.5 m/s. The optimal sizes of plate heat exchangers are recommended for all of the above applications.

The concept of an effective NPP with a gas-cooled thermal neutron reactor

The paper shows the technical possibilities of increasing the efficiency of nuclear power plants by using the technology of a channel thermal neutrons reactor with a gas coolant and water moderator. The main characteristics of the core, fuel campaign and heat exchange equipment are considered. Developed new concept of NNP design based on promoted gas-cooled reactor.

Geometric characteristics of the pipe in pipe type device with a screw heat exchange element

To increase the thermal and hydrodynamic efficiency of tubular apparatuses, it is necessary to develop new designs of heat-exchange elements, which are distinguished by high thermal efficiency, manufacturability and low cost of production. In the work, it is proposed to use screw pipes as heat-exchange elements of tubular heat exchangers, since they have a higher degree of surface development compared to smooth-tube elements. The manufacturing technology of such pipes can be carried out in the cold state by the method of rotational forging (rotational compression), which is one of the varieties of the forging process and implemented on special rotary forging machines. To determine the heat transfer coefficients in the screw heat exchange elements mounted a special experimental setup. The main part of the installation is a pipe-in-pipe type heat exchanger, the heat exchange element of which is made in the form of a screw pipe. A experimental research technique has been developed, and the results of physical experiments on heat transfer, as is known, are generalized by criterion equations in which an equivalent diameter is used as a characteristic size. In this regard, the authors proposed a method for calculating the basic geometric characteristics of a screw heat-exchange element, and also obtained formulas for calculating the equivalent diameter of the pipe and annular space in a tube-in-pipe apparatus with a screw heat-exchange element. The results of this work can be used in the calculations and design of new promising heat exchange equipment.

Heat exchange at the boiling of ozone-safe refrigerants and their oil-freon mixtures

The object of research is the processes of heat and mass transfer during phase transitions of ozone-safe refrigerants and their oil-freon mixtures on smooth finned and capillary-porous heat-transfer surfaces of industrial heat exchange apparatuses.The purpose and objectives of the research was theoretical and experimental research of processes of heat transfer in developed bubble boiling of ozone friendly refrigerant and oil-refrigerant mixtures on smooth and developed surfaces of heat exchange by establishing relationships to determine the coeffi-cients of heat transfer and influence of the various factors that determine the intensity of heat transfer at phase transitions in devices of refrigeration, heat pump systems and air conditioning systems; the estab-lishment of the mechanism of heat transfer processes during evaporation of oil-refrigerant mixtures. De-velopment of practical recommendations for the calculation and design of high-efficiency heat exchange equipment, reducing the material consumption and weight and size indicators of heat exchangers. Development and implementation of improved performance vaporizers and condensers for refrigeration, heat pump installations and air conditioning systems.For the first time, experimental studies of heat exchange processes during the boiling of refriger-ants and their oil-freon mixtures on various surfaces in a wide range of thermal loads (2,9…100,8 kW / m2). Graphic dependences of the heat transfer intensity on the operating parameters of the boiling process and other characteristics are obtained.The results of the work are implemented in the technological process of VESA LLC and in the educational process of Sukhoi state technical University for lectures on the disciplines “heat and mass Transfer” and “Industrial heat and mass transfer processes and installations”.The results obtained can be used in the development and creation of highly efficient evaporative heat ex-changers.

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.