APPLICATIONS OF NANOMATERIALS IN HEAT EXCHANGE PROCESSES AND EQUIPMENT

RELEVANCE The article is devoted to the development of new designs of heat exchangers and evaluating the efficiency of their operation. According to the authors, currently of particular interest are conical heat exchangers of the "pipe-in-pipe" type, so the object of research in this paper is a heat exchanger in the form of a truncated cone based on a spring-twisted channel. The introduction of the proposed heat exchange elements and apparatuses into the industry requires additional research. To assess the effectiveness of the application of the considered TA, it is proposed to evaluate its performance in comparison with conical and cylindrical TA based on a smooth-walled pipe. Due to this, two hypotheses will be tested at once: the use of a conical coil heat exchanger is more efficient than a cylindrical one, and the replacement of a smooth-walled pipe with a spring-twisted channel increases the efficiency of the heat exchanger.OBJECT. The aim of the research is to develop a method for setting and solving the conjugate heat exchange problem for a heat exchanger in the form of a truncated cone with a heat exchange element in the form of a spring-twisted channel, analyze the results obtained and evaluate the efficiency in comparison with conical and cylindrical heat exchangers based on smooth-walled heat exchange elements. METHODS. For the numerical solution of the conjugate heat transfer problem, the FEM implemented by means of Ansys was used Fluent. RESULTS. The main results consist in the fact that the authors developed a model and algorithm for calculating conical coil heat exchangers of the pipe-in-pipe type, implemented in the Ansys program, and determined the thermal and hydrodynamic parameters of coil devices. A comparison of coil heat exchangers was also made: a conical one based on a spring-twisted channel with a conical one and a cylindrical one with a smooth-walled heat exchange element. The calculation results showed that replacing a smooth-walled pipe with a spring-wound channel significantly increases the efficiency of heat exchange equipment. CONCLUSION. The significance of the obtained results lies in the possibility of using modern, more efficient and compact heat exchange equipment for technological needs and in the justification of this choice. Thus, with equal initial data, conical heat exchangers are more efficient than cylindrical ones with a heat exchange element in the form of a smooth tube, since they need a smaller heat exchange surface to achieve the necessary thermal and hydrodynamic parameters. The results of calculations prove the prospects of using a conical TA based on a spring-twisted channel and show the need for further study of the influence of the geometric characteristics of both the coil itself and the heat exchange element on the thermal and hydrodynamic characteristics of the proposed HE.

Today, heat transfer processes are present in almost all technological processes of various industries. In heat exchange processes, shell-and-tube heat exchangers are quite effective and easy to manufacture, as the long-term practice of using these devices has shown. Therefore, intensification of heat transfer processes, improvement and development of appropriate equipment is a very urgent task. The object of research is a heat-exchange element with special finning on heat-exchange tubes. The subject of research is the heat transfer processes implemented in a heat exchange element with special finning. The aim of the study is to determine the efficiency of heat transfer of the finned surface of the heat exchange element under conditions of forced convection and to evaluate its efficiency by means of experimental and computer research. This article presents a computer simulation that allows to adequately assess the efficiency of using various designs of finning elements of heat exchange equipment. This is confirmed by the convergence of the experimental data and the results of computer simulation (the discrepancy between the results of the experiment and computer simulation does not exceed 5 %). Experimental and computer studies have shown that the proposed technical solution is more effective than standard ones and can be used in the design of new equipment or improvement of the existing one.

In industrial production and processing, the use of heat exchange equipment can realize the heat transfer between materials and achieve the goal of energy saving. At present, heat exchange equipment is used in many industrial production fields. In recent years, in China’s social production and life, the awareness of energy conservation and environmental protection has been continuously strengthened, which has also promoted the development and application of relevant energy-saving technologies. Relevant heat exchange equipment can effectively recycle high-temperature and low-temperature heat energy, with remarkable economic benefits. Shell and tube heat exchanger is the most widely used of all kinds of heat exchangers at present. This kind of heat exchanger has simple structure, good stability, wide practicability, low cost, convenient cleaning of heat exchange surface, and can meet the working environment of high strength and temperature. However, in the design of shell and tube heat exchanger, given the heat transfer temperature difference, some problems are easy to appear in the design of heat exchanger. Therefore, it is necessary to try to solve the problems through the idea of optimal design and improve the utilization efficiency of heat exchanger.

This article presents the results of modeling an automatic control system for heat supply of a greenhouse complex with a geothermal heat source, conducted in order to study the possibility of geothermal heat supply automation. For the implementation of modeling, a mathematical application package Scilab (version 6.0.1) is used. Reagentless treatment of geothermal water in the heat supply system with an acoustic-magnetic device can significantly reduce the intensity of scale formation in the heat exchanger and heat exchange equipment. It provides conditions for the automation of geothermal heat supply of greenhouses with a surface heat exchanger. Based on the results of the simulation, the optimal mode of operation of the heat exchanger automation system was developed. Using an automation system allow with greater accuracy and reliability to maintain the required temperature regime in the greenhouse, reduce the frequency of system shutdown for unplanned cleaning of the heat exchanger, reduce the complexity of manual operations of heat exchange equipment maintenance (removal of sludge, scale) and reduce the economic costs of transportation and heat consumption.

The indexes for evaluating the thermal performance of the spray chamber at home and abroad are introduced and analyzed. Due to the high relative humidity of the exhaust air in the mine, the air-water heat and humidity exchange process is usually carried out along the saturation line, and it is found that the general heat exchange efficiency is basically 1 through testing of different heat and humidity treatment processes, therefore, this indicator has been unable to accurately evaluate the performance of the heat and humidity exchange unit. An index for evaluating the heat and humidity exchange performance of the heat and humidity exchange unit is proposed, defining the heating efficiency and cooling efficiency by used water as the treatment medium in the heat and humidity exchange unit, taking the cooling and dehumidification process of counter-flow air-water heat and mass transfer as an example, the formulas for theoretical calculation include overall heat exchange efficiency, heat transfer efficiency and heating efficiency are derived, furthermore, three dimensionless efficiencies are obtained, and their relationship with the dimensionless mass transfer unit number and water-air ratio is analyzed. It provides a theoretical basis for thermal calculation and performance analysis of counter-flow heat and humidity exchange equipment.

Процес промерзання ґрунтового шару завжди супроводжується формуванням додаткових полів напружень
\nдеформацій в ґрунті і контактуючих з ним об’єктах (борти та уступи кар’єра, трубопроводи, дороги та
\nавтомагістралі, фундаменти, стіни, тощо). При промерзанні приповерхневий шар ґрунту різко змінює
\nшвидкість проходження сейсмічних хвиль, свою міцність та здатність до поглинання сейсмічної енергії.
\nОчевидно, що достовірна оцінка пружно-деформаційного стану в масиві ґрунту і взаємодіючих з ним
\nконструкцій багато в чому залежить від точності прогонозу температурних полів в масиві гірских порід.
\nПружні властивості гірських порід характеризуються модулем нормальної пружності, модулем зсуву
\nта коефіцієнтом Пуассона. Модуль нормальної пружності (модуль Юнга) є показником здатності масивів
\nчинити опір розтягу та стисненню при пружній деформації. Його величина залежить від мінералогічного
\nскладу, пористості породи, температури, вологості а також від виду деформації і величини прикладеного
\nнавантаження. Модуль нормальної пружності для мерзлих порід знаходиться в діапазоні 300 – 30 000 МПа,
\nщо в десятки і сотні разів більше модуля нормальної пружності немерзлих ґрунтів. При дослідженні фізикомеханічних властивостей мерзлих ґрунтів важливо правильно охарактеризувати їх фізичний стан,
\nвизначити фазовий склад води, установити характеристики основних фізичних властивостей мерзлих
\nґрунтів і їх вплив на фізико – хімічні і фізичні процеси.
\nДля встановлення залежності зміни модуля нормальної пружності від температури використані
\nекспериментальні дослідження для вологонасиченних мілкозернистого (d = 0.1/0.25 мм) та гравійового (d = 1/0.5
\nмм) пісків. Характер приведених в статті експериментальних залежностей наштовхує на думку, що існує єдина
\nзакономірність залежності модуля нормальної пружності від температури, яка може бути описана аналітично.
\nОпираючись на дослідження енергетичних переходів параметрів гірських порід при промерзанні, проведений
\nаналіз показав, що залежність такого типу може бути представлена математичною моделлю, яка представлена
\nв даній роботі. Як результат в даній статті встановлена закономірність зміни модуля нормальної пружності
\nдля водонасичених пісків при промерзанні ґрунтів з урахуванням їх температури яка описується подвійною
\nекспоненціальною залежністю і підтверджується експериментально.
\nВ статті підтверджено, що на зміну модуля нормальної пружності суттєвим чином впливає
\nтемпература гірського масиву. При зниженні температури модуль нормальної пружності для
\nводонасичених гравієвих та мілкодисперсних пісків зростає приблизно в 7 – 10 разів. Це явище зумовлене
\nзбільшенням міцності породи за рахунок утворення цементуючих полікристалічних льодових структур. При
\nпідвищенні негативної температури і при переході від грубодисперсних порід до тонкодисперсних і до льоду
\nодна і та ж величина відносної деформації досягається при все більш малому напружені.
\nАналіз закономірності впливу температури гірського масиву на модуль нормальної пружності Е (модуль
\nЮнга) показав існування значного стрибкоподібного підвищення модуля при зниженні температури. При
\nтемпературі приблизно нижче -10 C значення модуля нормальної пружності Е незмінні, тому що фазові
\nпереходи вже не є суттєвими. При переході породи з мерзлого стану в талий величина Е є незміною і для
\nбільшості гірських порід знаходиться в інтервалі приблизно 0,1/10 ГПа.
\nПрактичне значення результатів дослідження в даній роботі визначається можливістю в польових умовах
\n(на кар’єрі) виходячи з фактичних замірів температури ґрунту за допомогою отриманої аналітичної закономірності
\nвизначити модуль нормальної пружності та оцінити механічні, міцнісні та пружно-деформаційні властивості масиву
\nгірських порід кар’єрного поля. В подальших дослідженнях для підвищення точності знаходження модуля Юнга та
\nотримання ширшого розуміння міцнісних, механічних та пружно-деформаційних параметрів масиву гірських порід та
\nмерзлих ґрунтів необхідно дослідити також вплив вологості, мінералізації та тріщинуватості на модуль нормальної
\nпружності, а також включити їх як параметри аналітичної закономірності.

One of the main challenges for the energy industry is to improve the reliability and efficiency of heat exchange equipment in heating plants. Phase-change heat exchangers with low boiling point fluid (LBPF) are widely used in both conventional and renewable energy. The main objectives of increasing the efficiency of heat exchange equipment are to reduce the weight and dimensions, to increase the amount of heat transferred and to reduce the electricity consumption spent on pumping the heat transfer agent. These objectives are achieved by implementing various methods of heat exchange intensification in heat exchange equipment. A key aspect concerning application of various types of heat exchange intensifiers in heat exchange equipment is evaluation of possibility to increase their design efficiency. The paper presents the results of a computational parametric study of changes in efficiency of some LBPF-based plants when intensifying heat exchange processes by modifying functional surfaces of heat exchangers by laser ablation.

In this paper, steady state sensible performance analysis on multi pass parallel cross flow exchanger was considered. The inputs to the heat exchanger were described through meaningful physically significant parameters such as number of transfer units, capacity rate ratio and dimensionless input temperature. The inputs to the heat exchager were varied systematically and a parametric study was conducted to determine the thermal performance at each individual pass of the heat exchanger. Heat exchanger’s thermal performance was described through the discharge temperatures that were expressed in a dimensionless form. The results from the study were presented in the form of performance tables. The performance tables employed meaningful and industry recognized dimensionless input parameters and the heat exchanger‘s performance was described through dimensionless discharge temperatures at every pass of the heat exchanger. The developed performance tables shall serve two critical aspects. First, it will help the heat exchanger designers to readily choose an optimum heat exchanger. An undersized heat exchanger shall not deliver the requirements and likewise an oversized heat exchanger shall add unnecessary weight and cost. This aspect was clearly observed in this study as indefinetly increasing the number of transfer units (or surface area) beyond a threshold value didn’t enhance the heat transfer. By employing the performance tables as a guide, the heat exchanger designers can quickly ascertain the performance of the heat exchanger without having to perform simulations and/or lengthy calculations. Second, during operational phase of the heat exchanger, the performance tables can be used to understand the performance variation of the heat exchanger with respect to mass flow rates and/or can help the engineers to choose appropriate mass flow rates for the required heat transfer. The highest heat exchanger performance was observed at the lowest capacity rate ratio and likewise the lowest heat exchanger performance was observed at the highest capacity rate ratio. In-addition, during the operational phase, the performance tables can help to detect an underperforming heat exchanger and can help the engineers to schedule maintenance activity on the heat exchanger equipment.

The subject of the research is the construction of ring nozzles (ring packing elements) of heat and mass exchange equipment and methods of their oriented placement. The purpose of the research is a critical analysis of technical means of increasing the efficiency of an oriented (regular, structured) ring nozzle and, first of all, Raschig ring, which have been successfully used in various industries for more than a century. One of the most common, constructively simple and universal contact elements of column heat exchangers is a ring nozzle, in particular the "Raschig ring" patented in 1914 in Germany and Great Britain, the advantages of which are their high manufacturability and versatility in terms of the nomenclature of the processed phases, and the disadvantages are a relatively low specific surface area and different hydrodynamic conditions of the processed phases from the inner and outer surfaces of the nozzle elements, which is especially noticeable when the annular nozzle is loaded into the column apparatus in bulk, and oriented in a vertical position. An oriented (regular, structured) nozzle has a lower hydraulic resistance and a higher allowable velocity of the light phase. At the same time, various methods of stacking the ring nozzle are possible both within a separate layer and in adjacent layers: the formation of an ordered dense or loose stacking along the vertices of regular triangles (in checkerboard order), an ordered dense-loose stacking along concentric circles, chaotic stacking, ordered free uneven laying, laying with the formation of straight or stepped channels, ordered dense-free uneven laying, as well as placing elements of the ring nozzle according to the nesting doll principle. Modern advances in materials science and technology, as well as artificial intelligence, can provide significant help in the development of innovative designs of ring nozzles, which allows ring nozzles to successfully compete with other types of contact devices of heat and mass exchange equipment designed for the separation of various liquid and gaseous systems. The above Review can be useful to designers and inventors in the search for innovative technical solutions in the field of contact elements of heat and mass exchange equipment.

A multiperiod MINLP model for the synthesis of flexible heat and mass exchange networks

Heat exchangers are designed to carry out heat exchange processes when it is necessary to heat or cool the process medium in order to process it or recover heat. Heat exchange equipment constitutes a very significant part of technological equipment in the chemical and related industries. The share of heat exchange equipment at chemical industry enterprises is on average (15–18)%, in the petrochemical and oil refining industries about 50%. A significant amount of heat exchange equipment at chemical plants is explained by the fact that almost all the main processes of chemical technology (evaporation, rectification, drying, etc.) are associated with the need to supply or remove heat. In the chemical and especially petrochemical industry, most of the heat exchangers are condensers and refrigerators. The use of water coolers for these purposes, for example, shell-and-tube or irrigation units, is associated with significant water consumption and, therefore, with high operating costs. For these purposes, special heat exchangers are used—air coolers (AVO). Air coolers are mainly used where the use of other cooling systems is technically impossible or not economically feasible. Typically, air coolers are more expensive than water cooled heat exchangers. However, with air cooling, there are no corrosion and fouling problems associated with the use of cooling water, and there is no possibility of mixing water with the cooled process fluid.KeywordsAir coolerHeat exchangeAir flowDiffuser

Chapter 1 - Heat Exchange Equipment

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.

The environmental problem associated with the concentration of greenhouse gases and the consequent global warming of the climate should be addressed in an integrated manner. The authors propose the calculation of economic efficiency of a fundamentally new design of a heat exchanger based on intensification of processes of hydrodynamics and heat exchange. Switching to a new type of heat exchange equipment will save operating costs in residential apartment buildings, reducing CO2 concentration. When performing economic calculations, the methods of calculating the net present value of the project (NPV), discounted payback period (PBP), as well as the method of calculating the expected monetary result (EMV) for the risk insurance budget were used. Calculations were performed for two scenarios: basic and strategic. The discounted payback period from the replacement of one heat exchanger unit for the base scenario was 5.66 years, and for the strategic scenario – 2.73 years. The heat exchangers in question have a wide range of industrial applications, including: chemistry and petrochemicals, power engineering, household appliances, food and medical industries, shipbuilding and a number of related industries. Market analysis has shown that 4,000 units of new heat exchange equipment can be installed in the Republic of Tatarstan by 2033. At the same time, the reduction of greenhouse gas emissions in 2033 will amount to 81,160 tons of carbon dioxide equivalent.KeywordsHot water services tCarbon footprintEnergy consumptionEconomic efficiency

Modern microclimate systems for keeping poultry require new approaches. Air cooling and heating systems in the poultry house environment require significant water and energy resources. Therefore, the authors proposed an energy-efficient microclimate system in poultry houses using low-potential water energy from the use of shell and tube heat exchangers and soil heat exchangers. Among the included control parameters, the most important are the temperature in the room, the amount of harmful substances and air humidity. The amount of pollutants in the air is determined by the amount of air entering the room and the number of animals in it. When creating a mathematical model of the ventilation system in the poultry house, a material balance of harmful substances is created. One of the important factors is air consumption. Approximate functions of the required air exchange, as well as the required amount of water depending on the temperature of the outside air, were found. Depending on the required water consumption, the heat exchangers will be connected to work in autonomous mode using magnetic valves. One by one. At an outside air temperature of +23 ºС, it is necessary to use three heat exchangers with a water consumption of 2.5 m3/h. And in the temperature range from +35 ºС to +40 ºС, six heat exchangers with a water consumption of 57 to 108 m3/h are needed. A simulation model of heat and mass exchange in poultry houses in the summer period of the year was developed using heat exchange equipment in the MATLAB Simulink software complex. The indoor humidity change time constant will be equal to the time required to establish the indoor humidity set point once the humidity change rate is equal to the initial one. Model studies showed that the constant duration heating is 118.4 s. The productivity of the ventilation system is expressed as an approximate function and ranges from 36,000 to 170,000 m3/h. In fact, the simulation model system stabilizes in the summer period of the year in terms of temperature and humidity for up to 1000 seconds. Relative humidity is 60 %.