CFD Modelling of Hydrodynamics and Heat Transfer in Channels of a PHE

Plate Heat Exchangers (PHEs) are one of the most efficient types of contemporary heat exchangers with intensified heat transfer. They are commonly used in process industries due to their compactness, lower weight and cost, smaller space for installation and servicing compared to conventional shell-and-tube heat exchangers. Heat transfer in PHEs takes place in channels of complex geometry formed by corrugated plates placed abutting. The flow in such channels can be very complicated due to breakup and reattachment of the boundary layer, secondary flows and the small hydraulic diameter of the flow passages. The aim of this work is to compare a well-established and validated CFD code both with results obtained from an experimental PHE model using a corrugated plate commonly used in industrial applications and with existing correlations. The results show that CFD simulation can predict heat transfer rate and fluid flow behaviour in a range of Re numbers (8,900 to 27,650), with discrepancies up to 1 % and 6 % in terms of outlet temperature and pressure drop respectively. Modelling of the flow inside a single corrugation also allows for computation of the wall shear stress distribution which can be very useful in PHE applications where fouling is of particular importance

The Mathematical Modelling of Fouling Formation Along PHE Heat Transfer Surface

The phenomena of fouling can significantly deteriorate the intensity of heat transfer process and influence heat exchanger performance. The correct account for fouling is especially important in PHE with much higher heat transfer coefficients than in tubular heat exchangers. The mathematical model of heat transfer in PHE subjected to fouling is proposed. The model is represented by the system of partial differential equations which integration permit to estimate local parameters of heat exchanging streams and developing in time local values of fouling depositions layer thickness. The fouling rate is determined with the use of fouling deposition model proposed earlier. The model is validated by comparison with the data obtained for PHE working in industry and can be used for more accurate calculation of PHE heat transfer area in conditions of fouling formation than methods relying on averaged process haracteristics. The model application is illustrated by two case studies for PHE application in sugar industry and in District Heating system

Eco-Friendly Synergetic Processes of Municipal Solid Waste Polymer Utilization

The synergetic approach for eco-friendly efficient utilization of Polymer Solid Waste is presented. It is accounting for chemical processes in polymers during the use of the original product and at the stage of its waste recycling. The study of the polymer photoconductive degradation based on analysis of chemical reactions in the polymer film is presented. It is discussed how to predict the properties of the polymer after its use and to develop the efficient technique for its recycling. The recycling technique is demonstrated on examples of recycling polyethylene film by chemical foaming and injection moulding methods. The results of factorial experiments on the influence of different process parameters on process intensity and secondary product quality are presented. The results are used for developing modern technologies for the processing of polymer solid wastes into useful secondary products

The Development of Heat Substation for Drying Waste Heat Utilisation

The problem solution of waste heat utilization at the tobacco factory is considered in this work. The analysis of the possibility of waste heat utilization and appropriate calculations of plate heat exchangers were carried out. The method for multi component mixture condensation calculation is used. This allows obtaining optimal parameters for the working conditions of the heat exchangers according to the energy efficiency retrofit of industrial enterprises. The design of heat substation for waste heat utilisation was developed

Heat integration of ammonia refrigeration cycle into buildings heating systems in buildings

The possibility of utilizing the low potential heat of the ammonia refrigeration cycle has been shown. The design of an energy saving heat exchangers network to heat water and air in municipal buildings has been proposed. The possibility of increasing the pressure of ammonia with the purpose of improving the heat recovery in the system and reducing the load of the heating and cooling systems was considered. The minimum temperature difference in the heat exchangers network was selected. The economic efficiency of the retrofit project was estimated

Ammonia Refrigeration Cycle Integration in Buildings Heating System

This work investigates the possibility of ammonia low potential heat utilisation with use of Process Integration methodology. The two operation modes are considered. The first one is the use of ammonia gas super-heating and partly ammonia condensation. The low condensation temperature of ammonia is limiting the low potential heat usage. The second option is introduction of ammonia additional compression to increase the temperature of ammonia condensation. The low potential heat consumers are the hot water supply system, air pre-heating system and air heating for the fans

Investigation of Fouling in Plate Heat Exchangers at Sugar Factory

The fouling formation in heat transfer equipment is the complex process, which is determined by the physical properties of the heat carrier, material of the unit and hydraulic characteristics of the flow. The mathematical model based on the asymptotic behaviour of water fouling is examined. The fouling process supposes the net rate of fouling accumulation as the difference between the fouling deposition rate and the fouling removal rate. The relation for predicting the fouling resistance dynamics during the time is proposed. The investigation of precipitation and particulate deposition in purified juice heating PHE for the first stage evaporation, which operates in sugar plant, was examined. In this position М15М plate heat exchanger produced by Alfa Laval is used. The analysis and mathematical simulation of the experimental data are presented. For the juice heaters the content of fouling deposition is mostly the calcium salts as calcium carbonates and sulphates. The parameters of the equation for deposition term estimation were determined for the regarded heat carrier. It allows to determine the deposition term and to simulate the fouling formation in time. The comparison of the experimental data and mathematical calculations showed a good agreement. The proposed mathematical model enables to predict the fouling formation behaviour in PHE as purified juice heater and to determine the operation term for the cleaning of this unit. Basing on the observed model, the software, which enables to determine the periods of PHE cleaning during the operation was developed. The comparison of the industrial measurement data with calculation results is presented

Process integration of sodium hypophosphite production

The case study of flexible integrated flowsheet development for sodium hypophosphite production is presented. It is based on phosphoric sludge utilization process. The weight concentration of phosphorous in raw materials is equal to 30e50%. The reaction and separation parts of the system were designed based on detailed analysis of production stages. After that the process equipment was selected. Process modelling is made for annual production of hypophosphite equal to 2500 t. It permitted to extract process streams for heat energy integration and to define their parameters. The operating pinch procedure was used to estimate the consumption of hot and cold utilities for non-integrated process. The influence of utilities cost on minimal temperature difference is investigated. Analysis of heat system topology modification depending on energy prices is conducted. Optimal structure of heat recovery system and minimal temperature difference are determined. It is shown that optimal integrated process consumes 45% of hot and 30% of cold utilities required by non-integrated process

Серопозитивный ювенильный ревматоидный артрит: анализ спектра клинических проявлений и терапии, по данным ретроспективного исследования

Seropositive juvenile rheumatoid arthritis (JRA) is the rarest subtype of juvenile idiopathic arthritis (JIA) that is the equivalent of RA in adults and is manifested mainly by a symmetric polyarticular lesion, rapid structural disease progression with the formation of intraarticular erosions, the presence of positive rheumatoid factor (RF), and/or anti-cyclic citrullinated peptide (CCP) antibodies.Objective: to analyze demographic, clinical, and laboratory features of seropositive JRA and drug therapy according to a retrospective 10-year study.Patients and methods. The retrospective study enrolled patients diagnosed with seropositive JRA confirmed according to the ILAR classification, who were treated at the Childhood Rheumatology Department, V.A. Nasonova Research Institute of Rheumatology, from 2010 to 2020. Demographic indicators, data from clinical, laboratory, and instrumental examinations, and performed therapy were assessed.Results and discussion. The investigation enrolled 70 patients, amounting to 6.5% of the total number of patients with all clinical types of JIA. Among them, there was a great preponderance of girls (88.6%); the ratio of boys to girls was 1:7.8. The median age of onset of JRA was 12.2 [7.0; 14.0] years; the median duration of disease at diagnosis verification was 6 [4; 12] months; the median number of active joints at diagnosis of JRA was 16.5 [10.75; 23.25]; oligoarthritis was identified in 11.2% of patients at disease onset (within the first 6 months). During the first year of the disease, radiographic Stages II, III, and IV were defined in 42.9, 50, and 7.1%, respectively. Positive RF was found in 94.3% of patients; there was positivity for anti-CCP antibodies in 78.6%, a combination of positivity for RF and anti-CCP antibodies in 72.9%; only positive anti-CCR antibodies were seen in 5.7%. The median ESR at diagnosis verification was 29 [19.75; 44.5] mm/h; that of CRP was 15.0 [6.9; 34.4] mg/l. The extra-articular manifestations of the disease were found in 18 patients (25.7% of the total number of patients): fever in 5 (7.2%); lymphadenopathy in 17 (24.3%); lung damage in 3 (4.3%); rheumatoid nodules in 2 (2.9%); pericarditis in 1 (1.4%) patient, and uveitis in 1 (1.4%). Sjögren's syndrome was diagnosed in 25.7% of patients; autoimmune thyroiditis in 8.6%. A family history of autoimmune diseases was recorded in 22.8%. Nonsteroidal anti-inflammatory drugs and glucocorticoids were used in 97.1 and 48.6% of patients; respectively; the patients received synthetic disease-modifying antirheumatic drugs (sDMARDs): only methotrexate (MTX) [n=55 (78.6%)], sequentially 2 sDMARDs [n=10 (14.3%)], 3 sDMARDs [n=5 (7.1%)]; biological agents (BAs) [n=66 (94.2%)]. During the first year of the disease, Biological therapy was initiated because of the rapid progression of the erosive process in 78.6% of patients. 64.3% of children took one BA, 18.6 and 7.1% received two and three BAs, respectively. Abatacept (ABC) as the first BA was used most often (45.7%). The reasons for revision of therapy were its secondary inefficiency in most cases and serious adverse reactions in 4 patients (ABC- and infliximab-related infusion reactions in 2 cases and conversion of tubercular tests in 2). The differences in the anti-CCP antibody detection rate were statistically insignificant in the group that used only one BA effectively long and in the group that needed to switch to another BA. When choosing a BA, preference was given to tocilizumab or rituximab (RTM) in patients with seropositive JRA in the presence of systemic manifestations, and high clinical and laboratory activities and to RTM or ABC in those with detected Sjögren's syndrome.Conclusion. Seropositive JRA is a rare subtype of JIA that has an initially unfavorable course. Most patients require early aggressive therapy, including MTX and a BA due to the rapid progression of erosive arthritis. The presence of systemic manifestations and/or Sjögren's syndrome plays a defining role in choosing a specific BA. The presence of anti-CCP antibodies does not affect the selection or change of a BA.Серопозитивный ювенильный ревматоидный артрит (ЮРА) – самый редкий субтип ювенильного идиопатического артрита (ЮИА), являющийся эквивалентом РА у взрослых и проявляющийся преимущественно симметричным полиартикулярным поражением, быстрым структурным прогрессированием с формированием внутрисуставных эрозий, наличием положительного ревматоидного фактора (РФ) и/или антител к циклическому цитруллинированному пептиду (АЦЦП).Цель исследования – анализ демографических, клинических и лабораторных особенностей серопозитивного ЮРА и медикаментозной терапии по данным ретроспективного 10-летнего исследования.Пациенты и методы. В ретроспективное исследование были включены пациенты c диагнозом серопозитивного ЮРА, подтвержденным в соответствии с классификационными критериями ILAR, находившиеся на стационарном лечении в детском ревматологическое отделение ФГБНУ «Научно-исследовательский институт ревматологии им. В.А. Насоновой» с 2010 по 2020 г. Оценивались демографические показатели, данные клинического и лабораторно-инструментального обследования, проводимая терапия.Результаты и обсуждение. Всего было включено 70 пациентов, что составило 6,5% общего числа больных со всеми клиническими вариантами ЮИА. Среди них значительно преобладали девочки (88,6%), соотношение мальчиков и девочек – 1:7,8. Медиана возраста дебюта ЮРА – 12,2 [7,0; 14,0] года; медиана продолжительности заболевания на момент верификации диагноза – 6 мес [4; 12]; медиана числа активных суставов на момент установления диагноза ЮРА – 16,5 [10,75; 23,25], у 11,2% пациентов в дебюте (в первые 6 мес) заболевания был выявлен олигоартрит. В течение первого года болезни у 42,9% определялась II рентгенологическая стадия, у 50% – III стадия и у 7,1% – IV стадия. Положительный РФ был обнаружен у 94,3% пациентов, позитивность по АЦЦП – у 78,6%, сочетание позитивности по РФ и АЦЦП – у 72,9%, только положительные АЦЦП – у 5,7%. Медиана СОЭ на момент верификации диагноза составляла 29 [19,75; 44,5] мм/ч, СРБ – 15,0 [6,9; 34,4] мг/л. Внесуставные проявления заболевания обнаружены у 18 пациентов (25,7% общего числа больных): повышение температуры тела – у 5 (7,2%), лимфоаденопатия – у 17 (24,3%), поражение легких – у 3 (4,3%), ревматоидные узелки – у 2 (2,9%), перикардит и увеит – по 1 (по 1,4%) пациенту. Синдром Шёгрена диагностирован у 25,7% больных, аутоиммунный тиреоидит – у 8,6%. Семейный анамнез, отягощенный по аутоиммунной патологии, имели 22,8%. Нестероидные противовоспалительные препараты применяли 97,1% пациентов; глюкокортикоиды – 48,6%; синтетические базисные противовоспалительные препараты (сБПВП): только метотрексат (MT) – 55 (78,6%), последовательно 2 сБПВП – 10 (14,3%), 3 сБПВП – 5 (7,1%); генно-инженерные биологические препараты (ГИБП) – 66 (94,2%). В течение первого года заболевания генно-инженерная биологическая терапия инициирована у 78,6% пациентов из-за быстрого прогрессирования эрозивного процесса. Получили 1 ГИБП 64,3% детей, 2 и 3 ГИБП соответственно 18,6 и 7,1%. В качестве первого ГИБП чаще всего использовался абатацепт (AБЦ) – 45,7%. Причинами пересмотра терапии в большинстве наблюдений стали ее вторичная неэффективность, а также серьезные нежелательные реакции у 4 пациентов (инфузионные реакции на АБЦ и инфликсимаб – у 2, вираж туберкулиновых проб – у 2). Различия в частоте выявления АЦЦП в группе с эффективным длительным использованием только 1 ГИБП и в группе, в которой потребовалось переключение на другой ГИБП, были статистически незначимы. У пациентов с серопозитивным ЮРА при наличии системных проявлений, высокой клинической и лабораторной активности при выборе ГИБП предпочтение отдавалось тоцилизумабу или ритуксимабу (РTM), а в случаях выявленного синдрома Шёгрена – РTM или AБЦ.Заключение. Серопозитивный ЮРA является редким субтипом ЮИА, имеющим исходно неблагоприятное течение. Большинству пациентов требуется раннее назначение агрессивной терапии, включающей МТ и ГИБП, в связи с быстрым прогрессированием эрозивного артрита. Наличие системных проявлений и/или синдрома Шёгрена играет определяющую роль в выборе конкретного ГИБП. Наличие АЦЦП не влияет на выбор или смену ГИБП

The correlation of experimental results for condensation of steam from its mixture with air in channel of plate heat exchanger based on mathematical modelling

The process of steam condensation in the presence of air in channels of plate heat exchanger is investigated experimentall and with mathematical modelling. The equation accounting for transvers mass flux on heat and mass transfer is obtained. The results allow design of platecondenserss for steam containing noncodensable gas