Refrigeration engineering and technology

11-16

Authors: V. О. Bedrosov, M. G. Khmelniuk, O. Yu. Yakovleva

Nowadays energy efficiency improvement and global warming are issues of current interest because of the natural resources depletion and extreme climate change. Thus, the problem of formation of strict regulations regarding emissions into the air arises. This paper presents the study of cascade refrigeration system for re-condensing of associated petroleum gas during sea transportation for LPG carrier. The structural optimization has been performed. LPG gas carriers with 266 000 m3 ethane capacity require 15 MW cascade refrigeration system for re-condensing if the temperature in the coastal LPG storage is -70°C, and the temperature for transported Ethan is maintained at -75°C. For current storage conditions the required system cooling capacity is only 1,078 MW intended for the heat gain rejection from the environment during Ethane transportation. The replacement of ozone-depleting refrigerant R22 to alternative agents: R407C, R404A, R402A, R717, R290, R1270 was estimated. The results of analysis have shown that the proposed improvements can be used to optimize the LPG carrier cascade refrigeration system.

21-26

Authors: V. V. Gorin

The paper provides the works review that includes the results of theoretical and experimental studies of condensation inside horizontal tubes. The comparison of theoretical (semi-empirical) solutions and ex-perimental data is given.

37-43

Authors: D. I. Harasym, V. Y. Labay

In modern technologies, which are related to energy transformation, namely in air conditioning systems, important places are occupied by equipment and processes, the objective estimation of value of its energy perfection can be defined only on the basis of analysis of its exergy effectiveness. Innovation mathematical research model, created by the authors, of the implemented central straight flow air conditioning system for operating cleanrooms was used, which gave opportunity to make computer estimation of its energy effectiveness by the virtue of exergetic output-input ratio depending on different factors, which have influence on its work, in particular on parameters of outdoor air ( , ). The dependence of exergetic output-input ratio of implemented central straight flow air conditioning system with recuperative air cooler and air productivity that is 4300 kg/hr for operating cleanrooms on parameters of outdoor ( , ) air by different indoor parameters ( , ) and on temperature difference between indoor and supplied air was presented. This dependence showed that the exergetic output-input ratio of the system gains its maximum by lower temperatures of outdoor air. It was shown that for providing the microclimate in operating cleanrooms the implemented central air conditioning system, with the aim of energy saving, should be used by temperature of outdoor air ≤ 35°С and by higher (as much as possible) temperature difference between indoor and supplied air ≥ 6,0°С. This will give the opportunity to get a high exergetic output-input ratio ≥ 1,93, which means to get the most economical variant of exploitation of the implemented air conditioning system. It is worth to mention that moisture content of outdoor air has no influence on exergetic output-input ratio of this air conditioning system.

48-53

Authors: D. A. Ivchenko, V. P. Zhelezny, I. V. Motovoy, K. O. Shestopalov

New experimental data for isochoric heat capacity from the two-phase region of dimethyl ether for DME (dimethyl ether), TEG (triethylene glycol) and DME/TEG solutions at weight fractions of DME 20.8%, 74.7% in temperature range from 152 to 324 К have been reported in the paper. The mean uncertainty of the experimental data does not exceed 0.45%.

58-64

Authors: V. Matukhno, Yu. Baidak, P. Tomlein

Improving of the technical level of modern distribution transformers (DT) by reducing of their weight and dimen-sions, increasing of specific power are inevitably associated with the development of method which takes into ac-count the thermal processes and technical means of intensifying the existing and new systems of their cooling. Par-ticularly important rises the question of effective cooling of small and medium power distribution transformers, which constitute the bulk of the complete switchgear in power supply systems.The result of the study is the substan-tiation of expediency for simulation results implementation of heat balance equations drawn up for the active part of the voltage distribution transformer, at the stage of its final and qualifying design. The active part is located in the transformer oil environment, and heat emission is carried out by heat transfer and convection. The heat balance mathematical model corresponds to the equivalent thermal equivalent circuit, consisting of two adjacent units with heat sinks - generalized coils and ferromagnetic core and of the third node adjacent to them - moving matter from the oil, which additionally contact with the infinite heat capacity environment. The solution of equations obtained for the mean temperatures of the winding, magnetic conductor rod and oil in function of time, allows setting of their expected values during transformer operation and especially with the uneven schedule of its loading, and to exercise grounded choice of magnetic induction in the magnetic rod and the current density in the windings according to the parameters of allowable for them heating temperatures

75-79

Authors: N. V. Zhіkhareva, M. G. Khmelniuk

The mathematical model of unsteady heat exchange space has been carried out. The heat balance of the object system is modeled by the system of ordinary inhomogeneous differential equations with nonlinear coefficients. In the developed model the transient nature of heat transfer through the structures enclosing surfaces, the intensity of solar radiation on people, equipment and lighting are taken into consideration. The climatic equipment was selected according to performed calculations which will: provide the necessary microclimate parameters in air-conditioned areas in terms of maximum heat leakage in summer and maximum heat loss in winter and ensure high power efficiency with a small thermal load in the offseason. The results of mathematical simulation allowed to determine required cooling or heat capacity on average temperatures and corresponding power consumption of the system and supplement the correct set of input data for calculating the full costs of the object microclimate, including design, equipment purchase, installation and maintenance costs over the service life of the system and allowed to estimate the system payback.

9-15

Authors: A. S. Titlov, Yu. A. Ocheretyanyi

The study is dedicated to the engineering principles development of absorption type household refrigeration sets creation. Research objects are absorption refrigerating devices placed on small ships with the cooling chamber volume from 35 to 40 dm3, that are extremely exposed to external dynamic effects (rolling, shake, roll and pitch). It is shown that at large amplitudes of wind waves on small ships special constructions in which are provided the elements to prevent the adverse effects of pitching on the hydrodynamics of the working fluid flows should be applied.

27-31

Authors: N. A. Kolesnychenko, N. V. Volgusheva, I. L. Boshkova

Modeling of high intensity heat propagation processes in which the possible violation of the linear relationship between heat flux and temperature gradient is particularly complex. In this case the heat flux density is determined by the generalized Fourier law which takes into account relaxation processes. To estimate the contribution of relaxation phenomena of the body excessive temperature for the first kind boundary conditions was calculated. The possibility of getting on the thermal state of the body of data for any arbitrarily small values of the Fourier numbers is determined. Utilization of analytical functions which are based on hyperbolic heat equation, enables more accurate calculation of the temperature field in view of the relaxation processes and define the boundaries of the thermal front. It is shown that at the Fourier numbers close to the relaxation of the Fourier numbers, coordinate of the thermal layer is almost identical with the body surface. Estimated body temperatures in the first stage taking into consideration relaxation phenomena and on the simplified procedure demonstrate a marked divergence, however at the end of the first stage and at the second stage the temperatures correlation is satisfactory. Good comparability is observed in close proximity to the surface, the nature of changes in temperature coincides within the same thermal layer.

36-40

Authors: D. О. Pupkov

Development of a parabola-cylindrical solar heater designed for heating and cooking food using solar energy is presented in the study. The design consists of a reflector, as parabola-cylindrical lens and re-ceiver as skewers for food. Reflector is made of flexible materials but also has an advantage - resistance to external influences. Simple mount design allows collecting the heater into the drawing tube, the weight of which doesn’t exceed three kilograms, making the device convenient for transportation and in use. This is a special device due to which it is possible to concentrate solar radiation in the desired point and to reach the necessary temperatures suitable for heating and cooking of foodstuffs. The heater comfortable design has been shown and calculation features of basic geometric parameters of the parabola-cylindrical solar heater are given. The comparison with existing prototypes is given.

47-51

Authors: V. Kogut, I. Butovskyi, V. Bushmanov, M. Khmelniuk

Despite development of atomic and alternate power engineering’s, combustion of organic combustibles are one of key sources of power generation. Usage of this radiant are conjugate with venting is of flue gases which one composition gone into different chemical joints. Making of efficient purification methods of flue gases a front are more their venting, despite a long experience of application in the industrial purposes, remained the actual task. Of the modern perspective purification methods application of the ejector screen are one. Authors had framed a hydra a dynamic model of the ejector screen. Computer probe of passing of gases through the ejector screen displayed availability of padding hydrodynamic Coanda effect who, presumptively, increased a level of settling-out of cooled easily condense builders of flue gases.

11-15

Authors: A. A. Vasserman, A. S. Boychuk

Equations describing viscosity and thermal conductivity experimental data of refrigerants R125/R134a mixture are compiled. Coefficients are determined by the least square technique. Equations represent refrigerants mixture viscosity and thermal conductivity dependence from temperature, density and composition. Providing possibility to calculate mixture viscosity at temperature ranging 298…423 К at a pressure up to 6,0 MPa at subcritical and 248…345 К up to 2,8 МPа at supercritical densities. Thermal conductivity is described at temperature ranging 298…423 К up to 6,0 MPa at subcritical and 232…323 К up to 20 МPа at supercritical densities. Standard and maximum deviations of the experimental values from calculated do not exceed 3,1% and 5,3% for viscosity and 2,2% and 5,0% for thermal conductivity.

21-36

Authors: A. V. Doroshenko, V. Kh. Kirillov, A. R. Antonova, K. V. Lyudnitskij, V. V. Melekhin

The fundamental decisions of water and air evaporative coolers of direct and indirect type are developed with the lowered limit of cooling (in relation to the temperature of wet thermometer of entering to the cooler current of air). Heat-mass-transfer apparatus of film-type is executed on the basis of multichannel compositions from polymeric materials with the channels of intricate configuration. A mathematical model describing the common heat-mass-transfer processes in the evaporative coolers of indirect type (IECg and IEC-Rg) has been proposed, the comparative analysis of the developed evaporative coolers abilities has been carried out on the basis of the obtained experimental data on heat-mass-transfer processes efficiency. The initial parameters (temperature and humidity ratio) of air flow and contacting flows of gas and liquid correlation were varied in the experiment. The special attention has been spared to the features of heat-mass-transfer processes flowing at the low temperature water and air cooling.

42-48

Authors: N. V. Zhіkhareva

Using the basic principles of simulation the method for calculating of the annual consumption of cold by air-conditioning systems was developed. The initial data are: location of the building and the local weather conditions according to the long-term supervision; estimated barometric pressure; the number of working days, shifts; mass flow rates of the supply air G, outdoor air GH and recirculation Gp; coefficient of recirculation; constant or variable value of the enthalpy of recycling air hp and cooled air hoh; temperature (°C) and the enthalpy of the indoor air. On the basis of the database of the table monthly averages of temperatures tn.m (°C), outdoor air and water vapor partial pressure PH (kPa) the monthly average enthalpy hn.m. using the splines interpolation method, the total share of cold per unit of air conditioning systems air flow, the annual consumption of cold, taking into account the dimensionless factors are determined. The developed method allows to compare the alternative variants of air conditioning systems in the optimization problem.

52-60

Authors: Y. К. Коrnіenко, Y. S. Fеdchеnkо, F. А. Trіshyn

The article dwells upon the experience of implementation and application of support learning based on Moodle, which has been created and applied in the Odessa National Academy of Food Technologies since 2014. The role provided for the distance education programs is emphasized, the benefits of system based on Moodle are proved in a well-argued manner: the system is freely distributed, simple to install on any platform that supports PHP; it is spread among many institutions of higher education; it has a multilingual interface (including supported Ukrainian, English), designed to meet the advances of modern pedagogy (focus is on the interaction between the students, forum discussion); has a simple, "easy", efficient, compliant web-based interface. Besides, the system provides great possibilities to conduct assessment of knowledge. It is noted that at this stage of application of the system based on Moodle is used in the academy to support traditional education as intramural and extramural forms of study, including the organization of independent work of students. Distance Learning Center website was developed by e-mail: http://moodle.onaft.edu.ua/, requirements document, the Center operates by, were prepared and approved. Along with installing Moodle software environment it was made possible to design distance learning courses on server hosting registration. It is noted that the present system of distance learning of ONAFT contains 285 distance learning courses filled with the necessary teaching materials. In general, 190 teachers are recorded as well as more than 3,000 students of all faculties of the academy and this number is growing. The requirements that developers of distance learning courses must consider are described. Examples of already created distance learning courses, their composition and characteristics are given. Some of them are offered teachers as a model for creating your own courses. Special attention is paid to the test control of knowledge required for current control of students' knowledge. The main types of tests, such as Multiple choice, Matching, Numerical, Essay, due to their features and settings are considered. Hereafter the mechanism of creation of these types of tests is explained on examples. Considerable attention is paid to the Journal of levels, which contains test results. Quality of creation of tests is analyzed, quality parameters are provided, the means to improve this quality are offered. The latest can be done by the application of external resources in the system Moodle, for example, by applying of such online resource as LearningApps.org.

9 - 14

Authors: Y. Zasiadko, O. Pylypenko, A. Forsiuk, R. Gryshchenko

The use of cold accumulators based on the principle of ice build up on the cooled surfaces during off-peak periods and ice melting during on-peak periods is an effective method of electricity bills reduction. Within comparatively short periods of on-peak demand a noticeable amount of thermal energy related to ice melting is to be released, it becomes clear that not only sizing of ice accumulators based on balance calculations is actual, but also the determination of time periods of ice accumulation becomes critical. This work presents experimental unit for obtaining data on the ice build-up on the vertical cooled pipes and later on to continuously register data on the ice thickness diminishing at the regimes of ice melting when cooling of pipe stops. The data for ice build-up and melting for some regimes have been presented and analyzed. The data form the base for deriving semi-empirical correlations allowing to determine a time intervals necessary to generate of ice layers of a given thickness.

25 - 28

Authors: I. Butovskyi, V. Kogut, N. Zhikhareva, M. Khmelniuk

Loss control of oil products is the one of the relevant paths of saving of the fuel and energy resources play a crucial role in development of economics. Now a great many of different procedures of a choice of means of reduction of oil losses and petrol from evaporation are known. However the one part from them did not allow for value of these means and expenditures for them maintenance, another – did not allow for diversity of implementation of means of reduction of losses, third – uses outdated, now, the criterion. In the conditions of petroleum storage depots, as a rule, usage of ejector systems of trapping of light fraction are more preferential, than other hardware’s of reduction of losses. The positive effect from application of an ejector heat exchanger for preventing of losses of petroleum products are calculate.

36 - 41

Authors: V. Z. Geller, N. I. Lapardin

In this paper, solubility and low temperature miscibility of refrigerants R407C and R410A in four different commercial Polyolester (POE) lubricants, produced by the same company but with different ISO standard viscosity grade, are measured with the aim to evaluate the possible correlation of solubility and miscibility with standard viscosity of the lubricant. Vapor pressure (solubility) is measured using calibrated, constant volume cells at oil mass fractions 30, 50, 70, 80, and 90% over a temperature range from -20 to 100 °C, and pressures up to 5 MPa. The measurements of low temperature miscibility limit (lower critical solution temperature LCST) were made using high-pressure sapphire cell. LCST was directly obtained by visual observation of a «milky haze» followed by a phase separation. Miscibility data were obtained at oil mass fractions from 5 to 50% over a temperature range from -60 to 0 °C. A set of simple equations was derived to describe the experimental results. Analysis of the obtained results showed that the solubility of refrigerant/lubricant mixtures depends weakly on the viscosity grade of the oil. At the same time, the miscibility gap (LCST) differ much bigger for various refrigerant/lubricant mixtures. The lower viscosity grade of the oil, the lower LCST of the refrigerant/lubricant mixture. LCSTs for the mixtures of R407C with the lubricants with the viscosity grades 32 and 220 differ by 30-45 °С.

48 - 52

Authors: Olga V. Olshevska

Creating a computer program to calculate microchannel air condensers to reduce design time and carrying out variant calculations. Software packages for thermophysical properties of the working substance and the coolant, the correlation equation for calculating heat transfer, aerodynamics and hydrodynamics, the thermodynamic equations for the irreversible losses and their minimization in the heat exchanger were used in the process of creating. Borland Delphi 7 is used for creating software package.

12 - 22

Authors: L. I. Morosuk, S. V. Gaiduk, B. G. Grudka

Compression refrigeration machine driven by turbine (working fluid is the same as for refrigeration machine) is classified as heat-using compression refrigeration machine. The scientific development of the heat-using compression refrigeration machines associates with introducing R744 (carbon dioxide) as the working fluid. It leads to an expand in the opportunities of these machines through (a) utilization of heat with different temperature levels, (b) development of new schematics and corresponding thermodynamic cycles, (c) contribution to the energy saving, and (d) contribution to the ecological problems associated with refrigeration. A heat-using compression refrigeration machine consists of two thermodynamic cycles: direct (for generation of work) and inverse (for generation of cold). Efficiency of each cycle depends on the schematic. In this paper, the two possibilities for the direct cycle have been evaluated: simple and with heat regeneration. The energetic and exergetic methods of thermodynamic analysis have been applied. It is shown that the thermodynamic effectiveness (exergetic efficiency) depends on the combination of schematic and operation parameters within the gas heater, and the magnitude is the function of the temperature level of utilized heat. Results obtained from the exergetic analysis showed the irreversibilities within each system component and identified the components that have highest priority to be improved in order to contribute to the energy saving problem.

29 - 33

Authors: V. E. Kogut

During the last decades world industrial projects are characterized by increasing of power consumption. Considerable contribution to the power balance is deposited by manufacture of refrigeration machinery. It is the challenge for development of information technologies, revising of fuel strategies revision in favor of natural gas and other factors. Burning of petroleum hydrocarbons is associated with greenhouse gas emissions into the atmosphere, which is an environmental problem. Therefore, an intensive search for alternative compression refrigeration continues. Ejector refrigerating machines can be attributed to the best solutions. However, the wide practical application depends on many constraints - low energy efficiency (small thermal coefficients compared with absorption chillers). The author focuses on a series of relevant issues related to economic efficiency in the power industry sector. Economic efficiency of ejector heat exchangers utilization in the branch depends on the quality of heat application and investments to such heat exchangers, as well as on the operating costs. The utilization of heat exchangers is based on the qualitative usage of contact heat exchange. The classification of the ejector heat exchanger utilization in various industry branches directly related to workflow systems is given.

40 - 45

Authors: N. A. Borisov, V. V. Miroshnichenko, V. M. Arsenyev, O. G. Golubkov

Preheating fuel gas in the gas turbine can be carried out in recuperative heat exchangers installed in the lubricating system of gas-turbine engines, in which heat from the heated oil is passed to fuel gas. In such exchangers it is necessary to exclude the possibility of leakage and mixing of fluids and, in case of emergency, to provide emergency shutdown of the machine. To such heat exchangers belong gas-oil heat exchangers, which are made of bimetallic tubes with safe (signaling) channel. Secure channel provides automatic operation of the system in an emergency. The article describes a constructive solution of the gas-oil heat exchangers from bimetallic tubes with safe channel. Bimetallic tubes are used both smooth and finned, with different design of safe channel. Feasibility analysis of the use of smooth and finned bimetallic tubes in gas-oil heat exchangers was performed. It is shown that the bimetallic finned tubes allow increasing the compactness of the heat exchanger and reducing the weight and material cost of the tube bundle. The lack of methods of thermal calculation of heat exchangers with safe channel resulted in the setting of goals for further research, in particular the development of mathematical models, conduction of numerical studies and physical experiments.

62 - 65

Authors: N. V. Zhіkhareva, В. І. Реrеpека, M. G. Khmelniuk

The paper considers the method for calculating the branched air-supply systems, ventilation and air-conditioning. This paper presents a small segment of power saving tasks in the ventilation and a microscopic segment of the huge complex problems rational use of energy with the necessary reduction of harmful impact on the ecology of the system environment. The method of calculating the air supply ICU-ventilation and air conditioning is considered. The aero-dynamic calculation of fresh air system with fan was carried out according to this methodology and the "working" point was found. In a specific example, the technique evaluation of technical solutions made at the design stage in order to reduce the total cost of establishing and operating air supply system that supplies air to several pro-industrial premises and technological units. Quantitative techno-economic analysis of 3 variants of the air-supply system is given (with calculations of the payback period) for applying of a predetermined amount of air with over-pressure data in three rooms. Special recommendations on power saving during exploitation of ventilation and air conditioning systems are also given.

71 - 77

Authors: D. О. Pupkov

Development of a parabola-cylindrical solar heater designed for heating and cooking food using solar energy is presented in the study. The design consists of a reflector, as parabola-cylindrical lens and receiver as skewers for food. Reflector is made of flexible materials but also has an advantage - resistance to external influences. Simple mount design allows to collect the heater into the drawing tube, the weight of which doesn’t exceed three kilograms, making the device convenient for transportation and in use. This is a special device due to which it is possible to concentrate solar radiation in the desired point and to reach the necessary temperatures suitable for heating and cooking of foodstuffs. The heater comfortable design has been shown and calculation features of basic geometric parameters of the parabola-cylindrical solar heater are given. The comparison with existing prototypes is given.

87 - 92

Authors: S. O. Sharapov, V. M. Arsenyev

The article describes the mathematical model for calculating the geometric and power parameters of liquid-vapor ejector with a cylindrical mixing chamber and the results of numerical simulation of two-phase medium in a mixing chamber. Also the results of an experimental study of a plane-parallel liquid-vapor ejector with a cylindrical mixing chamber are submitted and compared with theoretical data. The analysis of the exergetic efficiency of the ejector with the mixing chamber is carried out.

97 - 105

Authors: S. G. Siromlia

The article discusses the features of technological preparation the company (TPC) in terms of a virtual enterprise (VE) energy machine manufacturer. The main way of the development of the TPC is complex automation on the basis of increasing the level of intelligence of the AS TPC. Integration of the system in terms of VE takes place on the basis of CALS-technologies, which provides a link for various business processes. As a basis for building such systems was selected multi-agent paradigm. To build as architecture AS TPC the most appropriate solution is to use agent-oriented architecture as a framework, divided into intelligent agents.