Volume 51 Issue 4
Section 1. Refrigeration engineering
CARBON DIOXIDE UTILIZATION FEATURES AS VAPOR-COMPRESSION REFRIGERATING MACHINE WORKING SUBSTANCE. EFFECTIVE CYCLES AND EXPERIENCE OF INTRODUCTION IN THE NATIONAL ECONOMY
As working substances of the vapor-compression refrigerators (VCR) it is possible to use various substances. These are specially synthesized mixtures – freons, and natural coolants – ammonia, carbon dioxide, hydrocarbons. VCR cycles suitable for operation on carbon dioxide (R744) are analyzed in the paper. Subcritical, transcritical, throttle, detander and cascade cycles in which carbon dioxide is applied as a coolant of the low temperature contour are considered. Comparison of throttle cycles with various cooling temperature characteristics, one - and two-level compression is given. The short history of the refrigeration units working at CO2 introduction is presented, the list of the producers manufacturing the equipment taking into account features of the studied working substance is provided. Advantages of the cooling systems working at carbon dioxide on the basis of their operation experience in various European countries are shown.
Keywords: Refrigerator cycle; Natural refrigerants; Carbon dioxide; Refrigerating coefficient; Degree of thermodynamic perfection
SWIMMING POOLS AIR-CONDITIONING SYSTEMS CALCULATIONmethods
The paper describes the features of air conditioning systems design for indooryear-round operation pools. The features of humid heat load calculation and air consumption of air conditioning swimming poolsair consumption are shown. According to studies, a comprehensive model for calculating of swimming pool air conditioning, including the determination of optimal parameters definition of insulation thickness economic feasibility has been carried out. Selection of air conditioning system was made.
Key words: Model;Heat-humidity Loads; Condensation; Air conditioning; Swimming pool; Evaporation;Rate of airflow
A. V. Zimin
HOLD-OVER SYSTEMS WITH BINARY ICE UTILIZATION
This paper reviews different types of cold accumulation systems. The utilization of such systems due to the need of compensation of peak cooling loads by air conditioning of the large buildings or the technology requirements is considered.According to the type of storage media and the way a storage medium is used water (the aqueous solution) and ice. When using standard systems of cold accumulation to the consumer single phase coolant is served. System with binary ice can bring to the consumer a two-phase coolant. Application of two-phase coolant when cooling improves energy and performance characteristics of the refrigeration system with accumulation of cold.It justifies the reasons for using binary ice as a coolant. Examples of large industrial facilities using cold accumulation with binary ice are given.
Keywords: Hold-over systems; Binary ice; Peak load.
fluids bulk viscosity: CURRENT physical and analytical CONCEPTIONS and prospects of their development
Taking note of bulk viscosity is especially important at the description of high-intensity processes, such as explosion, a flow with high speeds, the acoustic phenomena, and also in characteristic points of a condition of substance. Bulk viscosity characterizes ability of substance to transformation of mechanical energy in thermal at nonequilibrium volume deformation. In the work the main theoretical directions of bulk viscosity influence studying are considered: physical acoustics, hydrodynamics, molecular and kinetic theory of gases and liquids. It is established that the molecular mechanism of the bulk viscosity emergence described in Landau's Enskog, Kramer works allows more deep understanding of the physical processes which are taking place at change of volume in the compressed liquid. Special interest is submitted to the theory of relaxation proposed by Mandelstam and Leontovich where the equation of a state includes the parameter defining internal structure of liquid that allows to consider effects of acoustic waves distribution. Expediency of Green-Kubo formula application which connects bulk viscosity with autocorrelation function of pressure microscopic fluctuations is noted. The existing methods of bulk viscosity coefficient experimental determination such as acoustic spectroscopy and Brillouin-Mandelstam scattering are analyzed. Problems of bulk viscosity near a critical point liquid-gas determination are considered.
Keywords: Bulk viscosity; Stress tensor; Relaxation; Sound waves; Molecular simulation; Acoustic spectroscopy; Optical methods.
V.A.Smyk, M.A. Kozminykh, Yu.V. Baidak
SIMULATION OF AIR DISTRIBUTION RATE IN REFRIGERATINGCONTAINER REFRIGERATION UNIT EVAPORATOR COMPARTMENT
Thestudyis aimed at solving the problem of convective heat transfer calculatingin thetubular evaporatorunit of refrigeratingcontainer, which is equipped with fan forced convection. The mathematical model of the problem as a differential equation that establishes the energy conservation law in the air cells through the surface of whichits movementis carried out is given. Inthe process ofthe convective heat transfer around the evaporatorproblemcalculatingthelink betweenthe basicphysical quantities in the air − temperature fields and velocityofitsmovement wasconsidered. Close relationshipofobtained temperature values and air velocity at the outletfrom evaporator unit as boundary conditions for further calculationoftemperature field in the refrigerator compartmentofrefrigeratingcontainerwas proved. Statement of the problem and itssimulation wereperformed in a two-dimensional coordinate system, and software environment COMSOL Multiphysics, Femlab 3.0, Fluid Dynamics - Incompressible Navier-Stokes - Convection and Conductionwasappliedforits solution. Theaccomplishedcalculations have shown that the integral temperaturevalue at the outlet of the evaporator unit,wascalculated taking into account air velocity, which islower than its valuesobtained without air movement consideration. The resultsof the studyshould be usefulduring the research of theconvective heat transfer phenomenon inthe differentrefrigeratingdevices,allow tochoose evaporatorand fan capacitymorereasonably under conditions ofobtainingthe desired cooling modeforperishable productsas well asin the learning process.
Key words: Simulation; Refrigerating container; Refrigeration unit; Evaporator; Forced convection; Rate vector
Section 2. Power engineering and energy saving
V. P. Zaykov, V. I. Mescheryakov, Yu. I. Zhuravlev
COMPARATIVE ANALYSIS OF THE MAIN PARAMETERS AND RELIABILITY INDICATORS OF SINGLE-STAGE THERMOELECTRIC COOLING DEVICES WHILE USING DIFFERENT COMBINATIONS OF INITIAL MATERIALS SETTINGS OF A SIMILAR EFFICIENCY
A comparative analysis of the basic parameters and reliability indicators of the single-stage thermoelectric cooling devices while using different combinations of settings compared to traditional initial materials of a similar efficiency for changes in temperature from 0 to 60 K and operation modes from maximum cooling capacity to the minimum failure rate is presented. It is shown that the use of initial materials with higher conductivity compared to the traditional means to increase the cooling capacity or to reduce the number of elements, to increase the thermoelectric cooling power, to reduce the failure rate and thereby to increase the probability of thermoelectric cooling device failure-free operation. It was obtained the simple ratios of interrelation of parameters and indicators of reliability for a variety of combinations of initial materials depending on the thermoelectric cooling power and temperature differential. It is shown that under the condition of a constant heat load and temperature difference parametric constants of thermocouples amount on the thermoelectric cooling capacity production. Analysis of the traditional version failure rate and other combinations of failure rate had helped to identify that the failure rate production on the maximum thermoelectric power is a constant for any combinations of the parameters of the source material, for any operation mode and temperature difference. The possible application of the superposition principle when building a single-stage thermoelectric cooling devices of a high reliability by combining of a constructive method (mode selection of thermoelectric cooling devices) and parametric method (selected combinations of the initial material) were discussed. It’s shows the application of the principle of superposition of structural and parametric methods of construction of thermoelectric cooling devices could significantly increase the reliability of thermoelectric cooling devices.
Keywords: thermoelectric device; reliability; failure rate; efficiency; temperature; operating current.
V. E. Kogut, I. D. Butovskyi , V. M. Bushmanov, M. G. Khmelniuk
ENVIRONMENTAL PROTECTION AGAINST CARCINOGENS RESIN AT IGNITION OF HEATING SYSTEMS
During the design and reconstruction of boiler systems measures that ensure cleaning of flue gases from the ash should be provided. Selecting a dust collector may be used depending on the desired degree of purification possible solutions layout. The degree of purification of flue gas from the ash should not be less than 90%. One known method for flue gas cleaning contains a bag filter and flue gas condensation. The composition of flue gas depends on the type of fuel or combustion mode includes thousands of compounds. The greatest threat to human health and other living organisms are substances cause cancer. An effective method of purification of flue gas is introduced into the stream of gases of different chemical substances, thereby altering the properties or any flue gases for increasing the degree of purification. This method of treatment is very promising. Condensation ejection filter is designed to condense the cancer-causing tar, which are formed in the ignition, a mixture of low-quality coal fuels, as well as transient. The use of this method of flue gas treatment will allow almost completely purifying the flow of flue gases from pollutants carcinogens.
Keywords: flue gases; carcinogenic resins; condensation filter; baghouse.
V.Y. Labay, D.I. Harasym
Investigations of exergy effectiveness and ways of energy saving of air conditioning system for operating cleanrooms
Nowadays for Ukraine the problem with saving energy resources is especially relevant in a conditions of market economy, where the main energy carriers, such as oil and gas, are limited. That’s why in the last decade with the aim of saving energy resources the fundamental researches of activity of different branches, manufactures and technologies from positions of exergy methodology are held abroad. Today cost estimates can’t be the only measure of effectiveness of energy equipment which recycles energy resources. Exergy is physical, not economical criterion and determines independence of this parameter from price fluctuations. The application of exergy allows to give objective assessment of energy resources of any type as it is the only measure of working capacity, applicability of energy resources. There are many examples of successful application of exergy methodology by technical and economical optimization in industry, especially in energy intensive branches. The minimum should be determined by exergy losses per unit of provided heat, not by financial costs. The analysis of exergy effectiveness of implemented central straight flow air conditioning system (ACS) for operating cleanrooms which was obtained on its innovative mathematical research model depending on different factors that have influence on its work was presented in this article, and ways of energy saving for this ACS was proposed. It was found that the biggest impact on exergy output-input ratio of its air conditioning system have the temperature difference between inside and supplied air in a room, temperature of inside air which is depends on temperature of outside air, and coefficient of transformation EER of chosen refrigeration machine of air conditioning system. It was shown that with the aim of energy saving the implemented air conditioning system should be preferably used at a higher temperature difference between inside and supplied air, for example, = 9,0°С (at any temperature of inside air) and at higher coefficient of transformation, for example = 4,0, which gives the opportunity to get the highest exergy output-input ratio , which means to get the most energy saving variant of exploitation of implemented air conditioning system.
Key words:Air conditioning systems;Cleanrooms;Exergy balance;Exergy effectiveness;Energy saving
Yu. Mitikov, M. Voloshin
STUDIES REFER TO LIQUID OXYGEN AREA OF LIQUID-BASED ROCKET ENGINE FUEL SYSTEMS
Hot helium temperature influence on liquid oxygen tank heating process during aero-dynamic heating has been investigated on practice. Tank diameter is 1.25 meters. Tank is made of aluminum alloy. Its upper and down bottoms are heat insulated, internal area is processed with chemical milling.The helium was input into tank center as stream. Aero-dynamic heating was simulated by nitrogen. It was input into annular gap between cylindrical wall and special cover. The value of specific thermal flow was controlled by amount of nitrogen. A time delay with opened drain valve was done after tank fill-up had been finished in order to stabilize fuel component temperature in tank, and tank structure. A tank was refilled to a needed level in case necessity had arisen. The tank pressurization using helium had been done to 3 bar value before oxygen sink. Some investigations were performed with some equal conditions with zero influence – when pressurization gas temperature was close to oxygen temperature inside tank. Oxygen temperatures were measured in different tank height, and in service manifold. A core with 23 temperature detectors was placed inside the tank. Sink time ~ 150 sec. High layer oxygen temperature detection maximum total error was no more than 0.5 K. The correlation absence between input helium temperature in 90-370 K range, and upper oxygen layer in tank heating using higher than 4 kw/m2outer heat flows to cylindrical tank part was detected. Upper oxygen layer top heat was less than 4 K in testing conditions, gas pressure inside tank – less than 1.9 bars. It is worth using simplified process models which are taking aero dynamical heating into account only, during oxygen heating process mathematical modeling.
Keywords:Upper oxygen layer heating; hot helium; aero dynamical heating; absence of correlation.
L.I.Morosuk, S.V. Gaiduk, B.G. Grudka
TRIGENERATION- SOURCE OF ENERGY SAVING IN LOW-POWER ENERGETICS FOR AGRICULTURAL PRODUCTION
Development of small agricultural production outside the settlements is constrained by the technical difficulties of implementation and cost of centralized power and heat supply. Low power energetics is capable for combined production of electricity and heat in a cogeneration system. Further energy efficiency increase of a small power plant is provided by trigeneration, wherein one kind of primary energy is transformed simultaneously in the three beneficial effects: electricity, heat and cold, which are equally needed to agricultural production. In the particular example of the farm, which has quarters, greenhouse and cold storages, the needs of recovered heat during the year were calculated, set a reserve and recommendations for its redistribution between the two beneficial effects: heat and cold, in accordance with the technological process of agricultural production were made. It is shown that the trigeneration system is capable of providing high energy efficiency of small autonomous power plant in the agricultural sector.
Keywords: energy saving; agricultural production; trigeneration.
A.S. Titlov, G.M. Redunov, D.P. Gozhelov, N.E. Ozolin
Mathematical SIMULATION of the energy efficient CONTROL modeS BY universal absorption cold chamber
The issues of reducing energy consumption in universal low-temperature absorption cells by improving the traditional mode of position control are considered. The mathematical model and the coefficients of transient low-temperature chamber with two absorption cooling units on the end walls, running under severe operating conditions at ambient temperature 31º C and cooling in the temperature range from minus 18 ºC to plus 12°C are given.
Keywords: low-temperature chamber; absorption cooling units; control modes; energy saving.
K. V. Agyeyev, A. E. Denysova
JET-VORTEX RECUPERATORS FOR ENERGY SAVING TECHNOLOGIES
The paper considers the basic theoretical concepts of vortex motion in relation to the solution of technical problems. The issue of instability of spiral vortex spatial structures when doublet or triplet of vortex filaments occurs is considered on the basis of the vortex theory. The problem of current importance is investigation of existence parameters for swirl or spiral shape disturbances. The disturbances so called processes with precessing vortex core (spiral shape vortex). The assessment of heat engineering equipment, in particular, recuperative heat exchangers is conducted. It is displayed that heating engineering units – vortex devices such as vortex combustor, combustion chambers etc. – have considerable advantages due to the operation in the active hydro–gasdynamic modes, and efficiency of their work is mainly depends on the operating and design parameters. The vortex effect that occurs in these devices allows making them compact, with an increased energy efficiency ratio, which corresponds to the objectives set in the Energy Strategy of Ukraine 2030. A construction of the jet-vortex compact recuperative heat exchanger, the operation features of which are in good agreement with the theory of the concentrated vortices, is given. It is displayed that the work of the jet-vortex recuperative heat exchanger is not completely identical to the cyclone vortex heat exchangers by the nature of the processes occurring there. The process of making decisions on the design parameters of a physical model (a cold aerodynamic experimental unit), its aerodynamic calculations and the selection of parameters for CFD-simulation of jet-vortex recuperative heat exchanger is considered. A technique for research on a physical model and its design is represented. The operation of the experimental unit is described. According to the results of CFD-research for recuperator operation, the high adequacy of the numerical CFD-model developed on the basis of the physical and simulation modeling results is presented.
Keywords: jet-vortex heat exchanger; physical model; heat exchanger with hydro-active modes
Section 3. Refrigerating and accompanying technologies
V.P.Zhelezny, N.N. Lukianov, О.Ya. Khliyeva, А.S. Nikulina
Experimental and calculational studies of the nanoparticle Al2O3 additives ON THERMALphisical PROPERTIES OF rEFRIGERANT R600a-compressor oil SOLUTIONS
The results of experimental and theoretical studies of the effect of Al2O3 nanoparticle additives on the viscosity, saturation vapor pressure, surface tension of R600a/mineral oil solutions are presented in the article. The model SP-QSPR - Skaling Principles - Quantitative Structure-Property Relationship to describe the experimental data and predict nanofluid thermophysical properties at wide range of parameters of state has been applied for the first time. It has been shown, that viscosity increase, saturation vapor pressure and surface tension decrease for refrigerant / oil solutions with additives of nanoparticles. These effects should be considered at assessment of nanotechnology prospects in the refrigeration equipment.
Keywords: Nanofluids; Refrigerant / oil solutions; Viscosity; Saturation vapor pressure; Surface tension; Experiment; Calculation methods
J. Kozonova, N. Povarova
LEADING TRENDS IN THE EUROPEAN FUNCTIONAL FOOD MARKET
Functional foods market is changing rapidly. Now the market has the highest growth. In the European Union food producers try to fit virtually every product under the "functional" definition. In this article we will review major trends in the EU functional foods market and try to analyze them. It is well known that foods fortified with nutritional and disease-preventing qualities are invigorating the world food industry. Health-conscious consumers are driving the demand for products that aim to promote better health, increase longevity and prevent the onset of chronic diseases. With a fast-emerging middle class, more disposable income, and a greater number of working/more educated women in emerging markets, the worldwide potential for functional foods/beverages is unprecedented. Milk formula, energy drinks, probiotic yogurt, juice drinks, sports drinks, cereal, and biscuits were among the top-performing functional global health and wellness food categories in 2014. There is a breakout of the year's top trends driving the market for functional foods and beverages. A review of recent deal drivers, the fastest-growing products and innovation trends can help businesses identify the most promising entry points to this market.
Key words: functional food; EU food market; fortified products; healthy food; nutrients.
EXPERIMENTAL STUDY OF CARBON TETRACHLORIDEVAPORATION INTO A GASEOUS MEDIUM
The results of experimental studies of carbon tetrachloride evaporation in different gas atmospheres (nitrogen and carbon dioxide) are given in the paper. The studies were conducted at pressures from atmospheric to 0.2 bar, and temperatures from 15 to 30 ° C. The work contains a detailed description of the experimental stand and features of experiment conduction. The obtained results allow testing of mathematical model for calculating the heat and humidity processes that occur in the processing of the refrigeration products.
Key words:Evaporation;Experimental study;Carbon Tetrachloride; Wet bulb temperature; Heat and humidity process
Section 4. Automatic, computer and telecommunication technologies
N.A. Kniazieva, A.S. Kalchenko
QUALITY OF SERVICES MANAGEMENT IN THE NEXT GENERATION NETWORKS USING THE METHODS OF FUZZY LOGIC
The method of controlling the quality of services in next generation net-works using the theory of fuzzy sets is presented in the paper. The algorithm of the quality of services management system is given. The proposed method of service quality management can effectively monitor and maintain the degree of users satisfaction with the services at the required level.
Keywords: Quality of services management; Next Generation Networks; Fuzzy Logic; Algorithms