Volume 51 Issue 1
Section 1. Refrigeration engineering
V.L. Bondarenko, T.V. Diachenko, E.G. Korzh, O.V. Diachenko
HEAT EXCHANGERS PERSPECTIVE FOR USE IN THE UNITS FOR KRYPTON-XENON MIXTURE ENRICHMENT
The shell-and-tube heat exchangers that are used in the new generation plants for the enrichment of the Kr/Xe mixture have been researched. The two types of heat exchangers (twisted and straight-through tube) have been researched in regard to the surface of the heat transfer, resistance in the annular space and metal intensity. The design characteristics of the capacitors at the various types of the tube beam: checkerboard, corridor and ring-type have been researched. The calculations results of the specific char- acteristics: heat exchange surface and metal intensity of the device have been shown. The results of the researches for a pole-type capacitor included in the design of the Chromium-3 plant have been given.
Key words: Krypton-xenon mixture – Shell and tube heat exchanger – Heat exchanger-recuperator – Condenser-evaporator – Heat exchange surface – Pressure losses – Metal intensity.
A.N. Gorin, A.B. Kudrin, M.V. Domin, O.N. Burdiyan
ABOUT TEMPERATURE FIELD VISUALIZATION OF THE REFRIGERATING CHAMBER EVAPORATOR OF THE HOUSEHOLD REFRIGERATOR
Experimental researches of temperature distribution on the evaporator surface of the household DH-239 refrigerating appliance working at isobutane depending on a charge dose of refrigerating system are conducted. The received results can be used for microleaks diagnosing methods development during household refrigerating appliances operation.
Key words: Household refrigerator – Evaporator – Isobutane – Thermographic shooting
V. Kogut, I. Butovskyi, N. Zhikhareva, M. Khmelniuk
APPLICATION OF EJECTOR-HEAT EXCHANGER IN THE INDUSTRIAL AIR COOLING INSTALLATIONS
The paper presents air cooling method in extreme conditions and fine-tuning to the desired parame- ters. Treatment processes in central air-conditioner with ejector heat exchanger closers in warm and cold periods of the year are shown. In modern industry, it is necessary to maintain a comforta- ble temperature of air in the workplace. There are many different methods of maintaining the tem- perature of the air (forced-air ventilation, air conditioning and refrigeration). However, all these methods are poorly effective in hot shops. The solution of this problem is possible with the use of in- stallation with ejector - heat exchanger. Cooling air is carried out by injection of fine water droplets in the air stream overclocked ejector - heat exchanger. The developed device can be used for cool- ing the workplace in metallurgical production and cooling the internal volume of military equipment in the hot season. Air-conditioning system with ejector heat exchangers allows maintaining in sepa- rate rooms set parameters of air through the heat treatment of air, except for the air conditioner, and even in-closers distributors.
Key words: Air cooling -Thermoperceptibility - Hydrothermal treatment
А.Е. Lagytin, P.F. Stoianov
THERMAL EFFICIENCY ANALYSIS OF CROSS-FINNED TUBES
Finned heat exchangers are the basic type of heat exchanger employed in many industrial applica- tions such as refrigeration, air conditioning and other thermal processes. This paper presents experi- mental research of air-side heat transfer of finned surfaces. Seven types of finned surfaces are em- ployed in this study. Investigation describes temperature fields and temperature cooling air-flow changing in the inter-fin duct without taking into account tube section. Temperature difference in- between local real air temperature data and fin surfaces are determined. The air-side heat transfer coefficients of finned tubes were evaluated at various air flow rate. Experimental setup was designed to simulate a single passage in a fin-tube heat exchanger. The heat transfer improvement of finned surfaces is a problem which includes several factors. Among the main factors are the fin form and its material. A series of tests presented in this paper reveal visual and quantitative details of local fin- surface temperature distributions for steel and aluminum fins. The air-side thermal performance data of finned surfaces were analyzed using conditional coefficient of heat transfer. Tube displacement in regard to fin on its thermal characteristics is evaluated. Experimental results have also shown that edge type of the inter-fin duct is not influenced on heat exchange performance. The results of research indicate that conditional coefficient of heat transfer can be used for performance comparison of finned heat exchange surfaces. This method is very useful for simple heat transfer estimation of finned surfaces for a wide range of practical applications.
Key words: Experiment – Fin- Tube - Temperature field - Heat transfer.
A.N. Radchenko, A.V. Grich, B.S. Portnoy
STAGE COOLING OF INTAKE AIR FOR INTEGRATED ELECTRICAL STATION ENGINE ROOM
Cooling of intake air for integrated electrical station engine room traditionally – by directing to air coolers of a coolant (water) from absorption lithium-bromide chiller and also deep cooling of the air by using a coolant with lower temperature received in combined two-stage chiller has been analyzed. The parameters of the air being cooled in the air coolers with various approaches of heat humidity treatment were determined.
Key words: Cooling – Heat humidity treatment air parameters – Air cooler.
Section 2. Power engineering and energy saving
А.V. Doroshenko, V.А. Goncharenko
ENGINEERING DEVELOPMENT OF MULTIFUNCTIONAL SOLAR SYSTEMS BASED ON THE HEAT-ABSORPTION CYCLE AND HEAT AND MASS TRANSFER DEVICES WITH A MOBILE NOZZLE
Scheme solutions of heat-cold supply and air conditioning combined solar systems, based on the open absorption cycle with an absorbent indirect regeneration and new types of heat-mass exchange appa- ratus with “gas- liquid- solid body" movable nozzle utilization were developed. For the first time evapo- rative air and water coolers of indirect type with regular structure nozzle and mobile-three-phase layer placed between the nozzle heat transfer elements, which increases the homogeneity of the moving layer processes and growth of the of heat-mass-transfer processes efficiency were developed. On the basis of theoretical and experimental research practical recommendations for determining solar systems opti- mal mode parameters and geometric parameters of the main elements of heat-mass-transfer equipment have been worked out.
Key words: Heat and Mass transfer device – Fluidized bed – Absorber – Desorber Cooling tower – So- lar system – Cooling system – Air conditioning
V.B. Rogankov, N.P. Suprun, M.V. Shvets, A.V. Shchutska
ABOUT CORRELATION BETWEEN THE PERCOLATION RATE OF MOISTURE THROUGH THE SEMI-PERMEABLE MEMBRANES AND THE STANDARD MEASURE- MENTS OF THEIR PERMEABILITY OR EVAPORATIVE RESISTANCE
A variety of test methods to estimate the water vapour transmission (WVT)-rate of thin membranes do not provide, unfortunately, the reliable basis to compare the permeability of different fabrics. Their results are cru- cially dependent on the details and construction of experimental methodologies as well as on the accepted by the different authors conditions of measurement. In this work, we propose the universal approach and demonstrate its adequate realization to compare the transport properties of any semi-permeable membranes measured by the conventional test-methods. The purpose is to avoid any confusion in such procedure of comparison. We have analysed below the WVT-rates measured by six alternative test-methods, which have been applied step-by-step to six different fabrics. In opposite to the widespread search for a pair correlation between the above results ob- tained by any two methods we treat them, in total, for each fabric in terms of the reduced variables. This ap- proach is based on the novel concept of the moisture percolation (MP)-rate which combines the diffusion and convective contributions in a transport process. It leads to the well-established general estimates of the normal- ized WVT-rates measured by the standard test-methods. Another advantage of the developed approach is its thermodynamic consistency, which offers the appropriate fluctuation model to take into account the porosity of any semi-permeable membranes.
Key words: Water vapour permeability – Standard test-methods – Moisture percolation rate
Section 3. Refrigerating and accompanying technologies
О. Pylypenko, А. Forsiuk, Ya. Zasiadko, V. Glushkov
DETERMINATION OF HEAT TRANSFER COEFFICIENTS OF BOILING REFRIGERANTS PERTINENT TO THE COLD ACCUMULATORS’ CONDITIONS
The use of correlations that would be capable to adequately account for the heat transfer between the surface and refrigerant are crucial for the accurate design calculations and proper heat transfer equipment sizing, including cold accumulators with ice generation on the heat transfer surface. A vast multitude of such correlations for the determination of overall heat transfer coefficient valid for different cross sections pipes and processes conditions are available now in the literature. The calculations of heat transfer pertinent to the conditions of cold accumulators, lead to the results drastically deviating from those obtained in the framework of the direct experimentation carried out at the Department of Power Engineering and Industrial Refrigeration of NUFT. In order to mark one or some of such correlations, that might have been used within the engineering calculations under condition of their proper correction, the critical comparative analysis of the literature sources has been carried out. The mathematical modeling of the heat transfer process in the condition of boiling refrigerant, with taking into account the valid limitations towards correlations, has been performed. The graphical comparison of the modeling results calculation with chosen correlations is performed. The results of the analysis allowed choosing the correlations, which could be recommended to be used within the engineering design calculations of cold accumulators with the ice accumulation on the heat transfer surface. The applications of such design correlations that adequately reflect the mechanism of heat transfer between the surface and refrigerant would be critical for the accurate design calculations of the transfer equipment of the refrigeration units, including cold accumulators with ice generation.
Key words: heat transfer coefficient – heat transfer – boiling – math flowrate – heat flax – ice accumulator – cold accumulator – refrigerant
Yu. M. Symonenko,V. Yu. Emelianov
THE PROTOTYPE OF SECONDARY DEVICE LEVEL METER OF CRYOGENIC LIQUIDS USED BY METAL OXIDE HIGH-TEMPERATURE SUPERCONDUCTORS
The aim was to create a cryogenic liquid the level gauge using thermoresistive effect in composite high- temperature superconductors (HTSC). The use of thin HTS provides reduced heat leakage to the small cry- oagent, makes potentially possible obtaining of good inertia, metrological and economic (payment for a single measurement) parameters. The paper discusses the results of heat transfer HTS conductor with liq- uid nitrogen simulation, experimental performances of HTS conductors are presented. In conclusion sec- ondary device-level meter of liquid nitrogen was designed and developed. Its testing on the laboratory Dewar flask with liquid nitrogen was carried out.
Key words: high-temperature superconductor, measuring the level of cryogen-liquids, thermoresistive level meter, the secondary device-level meter, level sensor HTS, Dewar flask, liquid nitrogen.
EQUATION OF STATE AND PROPERTIES OF FULLERITE С60
Crystalline molecular C60 (fullerite) in many respects is similar to solidified inert gases. This allows one to apply for the calculation of its thermodynamic properties theoretically based equation of state obtained previously for the molecular Lennard – Jones solid. Equation of state proposed by the author provides a simple analytical expression for the Helmholtz free energy and pressure and was used to calculate low temperature thermodynamic properties of fullerite. The results of the calculation of the thermodynamic properties: density, enthalpy, entropy, volume expansion coefficient and heat capacity of the solid polymeric nanocrystal C60 in a wide range of pressures presented are in good agreement with the available experimental data and can be used in practical applications. The calculated values of the second virial coefficient of fullerene C60 are also provided.
Key words: Fullerene -Nanostructures - Equation of State - Thermodynamic functions - Enthalpy - Entropy - Thermal expansion - Compressibility - Heat capacity
Section 4. Automatic, computer and telecommunication technologies
IMPROVEMENT OF MULTIMEDIA SERVICES QUALITY IN NEXT GENERATION NETWORKS USING FUZZY LOGIC METHODS
The paper presents a model for determining the degree of user satisfaction with quality of services, based on fuzzy inference on the basis of linguistic rules which are formulated based on user rat- ings. Proposed model is based on the fuzzy logic methods, because these methods allow evaluating user opinion most effectively. The model is a hierarchical structure that contains the main compo- nents of the service quality. For each of the components corresponding quality criteria are repre- sented. On the basis of the proposed model user perception for music streaming and download service was estimated. Simulation was performed in MATLAB using the instruments of Fuzzy Log- ic Toolbox. The simulation enabled to answer the question which components of the quality of ser- vice and which quality criteria cause the maximum effect on the degree of user satisfaction with the service. Moreover, proposed model enables to get in advance an idea of the variation of the degree of satisfaction of a user of a service depending on changes in the level achieved by a par- ticular quality criterion. The number of quality criteria that affect the final index can be easily changed if necessary. The proposed approach can be used to extrapolate and predict the degree of user satisfaction with quality of services on a limited statistical material.
Key words: Quality of services – Next generation networks – Fuzzy logic