Gennadii Khavin - Academia.edu (original) (raw)

Papers by Gennadii Khavin

Chemical Engineering Transactions, 2011

The paper concerns with analysis of the influence of corrugation form of PHE plates on hydraulic ... more The paper concerns with analysis of the influence of corrugation form of PHE plates on hydraulic resistance in the formed channels. The data for models of the main corrugated field of the inter-plate channel considered. It enables to exclude the influence of entrance and exit distribution zones. The specific type of generalizing formula is used, which correlates the data in a wider range of Reynolds numbers, compare to conventional ones. The equation for hydraulic performance of inter-plate channels with sinusoidal and triangular corrugations shapes is obtained, which generalizes experimental data of different authors available in literature. It accounts for the influence of the corrugation inclination angle to the plate vertical axis and corrugations pitch to height ratio.

Chemical engineering transactions, 2016

The fouling formation in heat transfer equipment is the complex process, which is determined by t... more 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.

Computer Aided Chemical Engineering, 2010

The computer aided design of plate heat exchanger with mixed grouping of plates is considered. It... more The computer aided design of plate heat exchanger with mixed grouping of plates is considered. It is formulated as the mathematical problem of finding the minimal value for implicit nonlinear discrete/continues objective function with inequality constraints. The optimizing variables include the number of passes for both streams, the numbers of plates with different corrugation geometries in each pass, the plate type and its size. To estimate the value of objective function in a space of optimizing variables the mathematical model of plate heat exchanger is developed. To account for thermal and hydraulic performance of channels between plates with different geometrical forms of corrugations, the exponents and coefficients in formulas for heat transfer coefficients and friction factors calculation are used as model parameters. The procedure and software for numerical experiment to identify model parameters by comparing the calculation results with those obtained with free available in web computer programs of plate manufacturers is developed. The sets of such parameters are obtained for a number of industrially manufactured plates. The described approach is implemented as software for plate heat exchangers calculation.

Lecture notes in networks and systems, Aug 26, 2022

The most difficult problem during the machining of polymer composite materials is the intensive w... more The most difficult problem during the machining of polymer composite materials is the intensive wear of the tool, which leads not only to a decrease in its working capacity, but also sharply worsens the quality of the operations performed. In this paper, we consider the process of wear of the cutting edge of a tool as a change in its microgeometry with respect to the initial state. The physical nature of abrasive wear as a process of contact interaction of the flank surface of a tool with a destroyed filler and intense heat due to friction is considered. Based on the laws obtained experimentally, we can conclude that the initial geometry of the cutting edge of the tool already sharply changes during the running-in period and by the beginning of stationary wear takes on some form, which later changes only quantitatively without distortion of the stable worked-in shape. In fact, we can say that the initial geometry of the cutting edge, selected for some rational reasons or as a result...

Bulletin of the National technical university "Kharkiv Polytechnic Institute" Series: Techniques in a machine industry

The relative angle between the direction of the reinforcing fibers and the cutting speed vector, ... more The relative angle between the direction of the reinforcing fibers and the cutting speed vector, defined as the angle of the reinforcing elements orientation, has a significant impact on the chip formation mode, cutting forces and the final surface quality. During machining of polymer composite materials, high-intensity wear occurs along the flank surface. This paper presents an analysis of the problem of the orientation fibers angle influence in a polymer composite on the cutting tool wear rate. For the previously proposed hereditary-aging model of tool weight loss due to wear, it is proposed to take into account the influence of the reinforcement angle through the dependence of the contact pressure and friction coefficient on this parameter. The article develops a generalizing model for practical consideration of the known in advance angle of reinforcement to predict tool wear and tool life during of polymer composite materials machining.

Plate heat exchangers are now widely used in different industrial installations due to their uniq... more Plate heat exchangers are now widely used in different industrial installations due to their unique characteristics important for process engineering. In recent years the use of plate heat exchangers for heat pumps has significantly increased, including the cases with natural refrigerants such as hydrocarbons, ammonia and carbon dioxide. The typical duties of plate heat exchangers in heat pumps with natural refrigerants are defined and acceptable types of plate heat exchangers for each duty discussed. The advantages of plate heat exchangers are very useful in units coupled with evaporators and condensers. In this case the proper selection of the plate materials taking into account the nature of the source of low potential heat for units coupled with evaporators is required. Proper prediction of fouling factor is also important for units coupled with condenser.

A method of using a different height of the corrugation along the side of the heating and incales... more A method of using a different height of the corrugation along the side of the heating and incalescent heat carriers to intensify the heat transfer process in the channels of heat exchangers with a circular plate is proposed. The use of such construction leads to equalization of the flow rates in the channels, a reduction in the number of channels, and an increase in the shear stress on the heat transfer surface of the plates. The search for the solution is based on the determination of the velocity of the heat carriers in the channels of the heat exchanger, when the pressure drop in the channels is complete satisfaction. The algorithm for solving the problem of finding the best solution is combinatorial. The problem of finding the optimal integer value (number of plates) is solved on a limited set of possible combinations of continuous design parameters – the height and angle of corrugation. The influence of the geometric parameters of the corrugation on its heat transfer capacity i...

New requirements and trends for the design and retrofit of heat substations of the central heatin... more New requirements and trends for the design and retrofit of heat substations of the central heating system are formulated. The main differences in the design of the central and individual heat substations are considered. The classification of heat substations for heating and hot water supply depending on the equipment included is given. The strategy of computer-aided design of the central heat substations under conditions of a new tariff policy is presented. The basis of the design is the simulation of the equipment selection that has not only technical compliance but also ensures the economic efficiency of implementation, which guarantees the reliability and operability of the substation during its operation. A model of operation of the substation in various conditions (time of year, the day of the week, day time) is presented. Mathematical models are implemented as a computer-aided design system, which allows us to calculate new heat substations and to make a high-efficiency retrof...

The process of machining composite materials, as the phenomenon of targeted destruction of the su... more The process of machining composite materials, as the phenomenon of targeted destruction of the surface layer, is accompanied by the release of a large amount of heat. That heat largely determines defines the picture of the stress-strain state in the tool-composite contact. The intensity and distribution of the temperature field mainly define the choice of the tool type and processing parameters which provide a given surface quality and productivity. A numerical-analytical model for determining the temperature field for orthogonal cutting of fiberglass with bundles reinforced is presented. The two-dimensional stationary problem of heat conduction of piecewise homogeneous bodies is solved by the boundary element method. An empirical relationship for average temperature and the heat source arising at the contact of the tool flank surface with the material being processed is used for as the boundary conditions in the model. The dependences of the maximum temperature on the feed, speed, ...

Eastern-European Journal of Enterprise Technologies, 2018

In the case when there is a difference in consumption on the side of the cold and hot heat carrie... more In the case when there is a difference in consumption on the side of the cold and hot heat carriers, the use of channels with the same corrugation height in one heat exchanger leads to a decrease in velocity of the heat carrier on the side with low consumption. Low velocity contributes to appearance of deposits on the heat transfer surface, which leads to disruption of operation mode of the apparatus and a forced clean-up stop. In case of using channels with a different corrugation height (cross-section area), velocities in the channels are aligned and intensity of emergence and growth of contamination falls sharply. It also allows us to reduce the heat transfer surface area of the apparatus and fully implement permissible pressure losses on the sides of the heat exchanger. For designing of heat exchangers of this structure, the authors developed the mathematical model that allows making calculations of heat exchangers for assigned operation conditions with the use of geometrical da...

Cutting & Tools in Technological System

Bulletin of the National Technical University "KhPI". Series: Chemistry, Chemical Technology and Ecology

У статті розглянуто модернізацію системи підігрівачів сиропу сорго перед концентруванням у випарн... more У статті розглянуто модернізацію системи підігрівачів сиропу сорго перед концентруванням у випарній установці. Процес випарювання є одним з найбільш енергоємних процесів хімічної технології, тому організація рекуперації тепла в цих процесах-це актуальна задача, особливо враховуючи високі ціни на зовнішні енергоносії. Для рішення задачі, що поставлена, було використано методи пінч-аналізу. На підставі розрахунків теплового та матеріального балансів було виділено теплові потоки для теплової інтеграції. За допомогою складених кривих і сіткової діаграми було проведено аналіз існуючого проекту і виявлено недоліки запропонованої системи рекуперації тепла, а саме, порушення мінімальної температурної різниці в теплообмінних апаратах та перенос тепла через пінч. Це тягне за собою як збільшення капітальних витрат, так і витрат на зовнішні енергоносії. На основі принципів пінч-аналізу було розроблено альтернативний проект інтеграції теплових потоків, що реалізує максимальну рекуперацію тепла для економічно та технологічно обґрунтованого значення мінімальної температурної різниці в мережі теплообмінників Tmin = 5 С. Для технічної реалізації модернізованої схеми було підібрано та розраховано додаткові пластинчаті теплообмінники. Пропозиції щодо покращення теплової схеми містять у собі забезпечення економії споживання гарячої утиліти (пари, що гріє), холодної утиліти (охолоджуючої води), підвищення загальної ефективності від використання модернізованої схеми. Техніко-економічний аналіз запропонованого проекту модернізації показав зниження споживання зовнішніх енергоносіїв в 1,43 рази в порівнянні з вихідним проектом. При практично однаковому терміні окупності альтернативний проект дозволяє отримати чистий річний прибуток на 42 % більше, ніж існуючий проект. Ключові слова: рекуперація енергії, пінч-аналіз, випарна установка, пластинчаті теплообмінники.

Journal of Sustainable Development of Energy, Water and Environment Systems, 2015

Hybridisation of district heating systems can contribute to more efficient heat generation throug... more Hybridisation of district heating systems can contribute to more efficient heat generation through cogeneration power plants or through an increase in the share of renewable energy sources in total energy consumption while reducing negative aspects of particular energy source utilisation. In this work, the performance of a hybrid district energy system for a small town in Croatia has been analysed. A mathematical model for process analysis and optimisation algorithm for optimal system configuration have been developed and described. The main goal of the system optimisation is to reduce heat production costs. Several energy sources for heat production have been considered in 8 different simulation cases. Simulation results show that the heat production costs could be reduced with introduction of different energy systems into an existing district heating system. Renewable energy based district heating systems could contribute to heat production costs decrease in district heating systems up to 30% in comparison with highly efficient heat production technologies based on conventional fuels.

High effective plate and spiral heat exchangers now are widely used in different industries inclu... more High effective plate and spiral heat exchangers now are widely used in different industries including production of mineral acids. The available information about their applications for heat treatment in conditions of such production lines is analyzed. Efficient and safe performance of heat exchanger determined mainly by its correct calculation and proper selection, especially of heat exchanger type and the material of heat transfer surface and gaskets. The analysis of existing industrial processes of phosphoric acid production wet method lets to define two significant problems in implementation of compact heat exchangers: aggressive nature of phosphoric acid and tendency of gypsum to precipitate on heat exchange surface. The approaches directed to solve these problems are discussed. The problem of implementation of plate heat exchangers in closed loop circuit systems around the barometric condenser are also discussed. For correct selection and modelling of heat exchangers in phosphoric acid production processes the interactive software is developed.