Issue 2 (148)
Section 1. Refrigeration engineering
V.P. Zhelezny, А.V. Melnik
THE LOCAL HEAT TRANSFER COEFFICIENT AT THE BOILING OF THE ISOBUTANE/ MINERAL OIL SOLUTION FLOW IN THE PIPE
Experimental data for refrigerant R600a mixed with the compressor mineral naphthenic oil ISO VG 15 boiling in the smooth small-diameter (5.4 mm) tube are reported. The tests were conducted at the inlet pressure psuc in the range from 62.3 to 82.2 kPa, heat flux from 2754 to 4105 W/m2, mass velocity varied between 11.90 to 18.54 kg/(m2∙s) and oil concentrations at the inlet to the evaporator from 0.25 to 0.5 % by mass. The results of the research of the local heat transfer coefficient at the boiling of the isobutane/compressor oil solution flow are given in the paper. It is shown that the substantial reduction of heat transfer coefficient was observed at high concentrations of oil. In addition, during the boiling of the refrigerant/oil solution the heat transfer coefficient in the lower part of the pipe is decreasing with mass velocity increasing.
Key words: Heat transfer coefficient – Real work fluid –Boiling – Isobutan – Refrigerant/oil solution – Concentration.
MATHEMATICAL ASPECTS OF FRUIT-AND VEGETABLE STOREHOUSE REFRIGERATING UNIT THERMOECONOMIC ANALYSIS
Mathematical aspects of fruit-and vegetable storehouse refrigerating unit operating mode thermoeconomic analysis are considered in the study. The values of exergy flow еnd exergetic losses on the example of direct cooling refrigerating unit are determined.
Key words: optimization – operating modes – refrigerating unit – thermoeconomic model – exergy – exergetic losses.
DESIGN-THEORETICAL STUDY OF CASCADE CO2 SUB-CRITICAL MECHANICAL COMPRESSION / AMMONIA EJECTOR COOLING MACHINE
In this paper an innovative micro-trigeneration system composed of a cogeneration system and a cascade refrigeration cycle is presented. The cogeneration system is a combined heat and power (CHP) system for electricity generation and heat production. The cascade refrigeration cycle is the combination of a CO2 sub-critical mechanical compression refrigeration machine (MCRM), powered by generated electricity, and an ejector cooling machine (ECM), driven by waste heat and using refrigerant R717. Refrigerant R717 as the working fluid for ejector cooling cycle is selected in the present study. Effect of the cycle operating conditions on ejector and ejector cycle performances is studied. Optimal geometry of the ejector and performance characteristics of ECM are determined at wide range of the operating conditions. The paper also describes the theoretical analysis of the CO2 sub-critical cycle and shows the effect of the MCRM evaporating temperature on the cascade system performance. The obtained data provide necessary information to design a pilot small-scale cascade CO2 sub-critical mechanical compression / ammonia ejector refrigerating unit with cooling capacity of 10 kW for application in micro-trigeneration systems incorporating reciprocating internal combustion engines and gas micro-turbines.
Key words: Ejector – Ejector refrigerating machine – Entrainment ratio – Coefficient of performance – Design characteristics – Performance characteristics – Micro-trigeneration system.
O.A. Lisohurska, A.V. Doroshenko
PROBLEM OF RECONDENSATION IN EVAPORATIVE COOLERS OF GASES AND LIQUIDS
The problem of gases and liquids evaporative coolers practical use area widening is associated with the reduction of the evaporative cooling limit from wet-bulb temperature to the dew point temperature of the outside air. This entails a risk of water vapor recondensation when approaching the equilibrium curve. The application of the "enthalpy potential" method to the availability of the water film thermal resistance, which is neglected in traditional calculations of the evaporative coolers is considered in the paper. The developed method allows to analyze the change of air flow state when it is in the directly contact with the liquid film, which is essential for deep cooling of a liquid (when the limit is the dew point temperature and the line of air state changes is coming directly to φ = 100 %). An equation expressing the additive phase resistance was received, and it is shown that the value of the thermal resistance of the liquid is up to 50 % of the total thermal resistance, that is nonnegligible, as assumed in the traditional evaporative coolers calculations. On the basis of experimental data the authors analyzed the influence of the contacting gas and liquid flows ratio and their initial parameters (temperature and moisture) on the danger of recondensation and recommendations to mitigate such threats were made.
Key words: evaporative cooler – multichannel – joint heat and mass transfer.
Section 2. Power engineering and energy saving
A.V. Bondarenko, V.E. Volkov, M.V. Maksimov
FLARE FLAME INSTABILITY AND BURNER COMBUSTION CONTROL
Research of the flare instability development and the laminar-to-turbulent transition for the flares was executed. It was proved that the effects of viscosity and compressibility have the stabilizing influence on the gas flame. The study of the individual flare stability makes the theoretical basis of the fuel burning technology in combustion chambers and for the burner combustion control.
Key words: flare – flame – combustion – instability – control.
A.V. Doroshenko, K.A. Rzhesik, M.V. Gordienko
EVAPORATED COOLERS OF AIR FOR POWER AND REFRIGERATION SYSTEMS. NEW DECISIONS AND POSSIBILITIES
The authors note the increasing importance of the evaporative methods of cooling, in particular, air coolers. On the basis of the evaporative coolers of indirect type (Indirect evaporative cooling, IEC) new decisions are worked out for chillers Ch-Rg* and Ch-Rg, in that the preliminary cooling of ambient air comes true in a heat-exchanger before its entering the evaporative cooler of EC, that provides lowering of the cooling limit to the dew point temperature of the ambient air of tр. Also several decisions were offered by the authors for multistage EC (IECg mst.) and, on the basis of the own experimental data, preliminary analysis of their fundamental possibilities was executed. The multichannel surfaces from polymeric materials were used as the nozzles in all types of EC. Air coolers of direct type DEC and Ch-Rg* have as a cooling limit the temperature of ambient air wet thermometer. IEC indirect type coolers and chiller Ch-Rg allow to cool the air flow at unchanging dryness, that is promisingly for the construction of the climatization systems and for the EC different multi-stage decisions design and have as a cooling limit a temperature of ambient air dew point. The comparative analysis of new decisions potential showed that degree of approaching to the cooling limit t** = (t2г - tр1) for the multistage cooler of IECg mst. is t** = 3,50С, at t** = 5,50С for single-stage Ch-Rg. But for chiller Ch-Rg the cost and expenses of power on the organization process are significantly less.
Key words: Evaporative cooler – Polymeric materials – Combined heat and mass transfer – Recondensation
N.V. Kulikova, А.А. Red’ko
THERMODYNAMIC MODEL OF HEAT-UTILIZER ON HEAT-PIPES
The heat-utilizer thermodynamic model based on the account of heat- carriers entropy change has been presented. The rated dependences for thermotechnical calculation of devices using the criteria, taking into account heat-exchange process nonequilibrium have been obtained.
Key words: heat-utilizer – heat-pipes – nonequilibrium heat-exchange – entropy.
NECESSARY PATCHES OR AMEND THE CURRENT DBN B.2.6 -31:2006 «THERMAL INSULATION OF BUILDINGS»
A modern revision of the DBN B.2.6-31:2006 shown in the INTERNET last year (2013), should be comprehen- sive, providing not only the introduction of innovations, but also clearing errors before-released previously. Scientific and theoretical basis for the design of the IOC secured long experience in operating and it is not nec- essary to modify it fundamentally. The publication gives examples from the text of this provision requiring corrections and clarifications, or, even, revision and additions: - Invalidity of indications of underestimation of the modern engineering level; - violation of the principle of unity systems measurements, collected by the general document in the general for- mula (probably intentionally); - backwardness of the restrictions stipulated by DBC, stimulated by observing these requirements principle of the constancy of specific thermal resistance; - appropriateness of the use of fencing structures properties that are excluded from consideration in above- mentioned standards (for example - mobility of heat carrier environment)... These and more durable inaccuracies hinder the implementation of modern-governmental ways of regu- lation of power losses in fencing by compensation of revenues from external sources.
Key words: Specific thermal resistance – Rolling stock – Barking flows – Operating period – Intersecting flows.
Section 3. Refrigerating and accompanying technologies
M.M. Kologrivov, V.P. Buzovskiy
INDUSTRIAL CONTACT APPARATUSES OPERATION EFFICIENCY
The experimental research results of water cooling efficiency in various constructions ventilator cooling towers at relative expenditures of water and air in a wide range is presented in the article. The obtained data were compared with similar characteristics of the absorbers.
Key words: Cooling tower – Absorber – Efficiency of the process – Limit loads – Water viscosity
CRYOGENIC METHODS OF ATMOSPHERIC HELIUM PRODUCTION
If there was a "Red List" of endangered chemical elements of the world, helium would definitely go in the top ten of critical substances. Along with silver, zinc and germanium helium is going to practically run out by the end of the twenty-first century. Moreover, the solar gas is the only gaseous element on this list. At the same time, a lot of modern and perspective technologies are impossible without helium. Unique physical and chemical features make it irreplaceable in scientific research, medicine, power engineering, aerospace and defense industries. Helium can be truly considered as an indicator of high technology.
Key words: helium, helium field, thermonuclear reaction, gas field.
R.U. Turna, P.G. Gakal, E.P. Ganja
REVIEW OF HEAT TRANSFER MATHEMATICAL MODELS FOR STREAM COOLING LINES OF POULTRY CARCASSES
Mathematical models of heat transfer for stream cooling lines of poultry carcasses, as well as methods of cooling time prediction in such systems are presented in the paper. The main goal of paper is the review of existing models and methods to define advantages and disadvantages each of them. The review allows to choice more appropriating models and methods and requirements for them in frame of stream cooling lines designing on the base of system principles. The basic re- quirements are: the model should be universal and doesn’t depend on form of carcasses; the mod- els must take into account the non uniform heat transfer conditions on the product surface; the model should be experimentally approval and should be simplified enough to include it into the system model of stream cooling line.
Key words: Heat transfer in poultry carcasses – Cooling time – Cooling treatment – Rate of cooling.
Section 4. Automatic, computer and telecommunication technologies
G.S. Gayvoronskaya, P.P.Yatsuk, I.V. Gannitskiy, Yu.S. Kazak
CERTAIN TELECOMMUNICATIONS TECHNOLOGY FOR SPECIFIC COUNTRIES DEVELOPMENT LEVEL DETERMINATION RESULTS
This article discusses research development of ICT sector in the world. Determining the level of development of a particular technology for a particular country is carried out by evaluation of statistical data on its use by the method of cluster analysis [3,4]. If the value of the technology is known for a set of countries , we can talk about the possibility of classifying them in terms of development of this technology. For this analysis, we used the official data on the number of users of different types of communication in 53 countries for the period from 2000 to 2012 . Data were taken from the site of the International Telecommunication Union  Studied data on the number of connections using : fixed wired broadband connection (T1) , fixed telephony (T2) , mobile communications ( T3) Internet ( T4). The result of applying cluster analysis will be the formation of several groups (clusters) of objects that are "similar" on a few selected indicators or integrated indicator.
Key words: Telecommunications technology – Technical progress – Digital divide – Tendency of ICT development – Clustering.
Galina S. Gayvoronska, Maxim Y. Solomitsky
ESSAGES STREAMS’ FORMALIZATION AT THE CONVERGENCE OF TECHNOLOGIES IN THE TELECOMMUNICATION NETWORK
Some results of messages streams’ research at the convergence of technologies in the telecommunication net- work are given in the paper. Object of study is the convergent telecommunication network in the process of in- teraction with external information metastructure. Network-forming process of convergent telecommunication network is the process of information transforming, implemented by a set of information technologies, including: computational process of information transforming in the space (input, output, storage, data processing) and in- formation process of information transforming in time (collection, distribution, transmission, switching of the streams). Herewith streams, incoming and circulating in the convergent telecommunication network, are com- plex in nature and structure. In order to research quantitative aspects of information transformation’s network processes it seems appropriate to study a conception of the messages streams – the aggregate of any infor- mation, transformed into electromagnetic signals, which is have to be transported within the convergent tele- communication network. At the study of the network during its functioning, it is assumed that it already existed for quite a long time before the study in order to reach the stationary functioning mode and it would function so after the finish of the study. A hypothesis about the stochastic nature of the messages streams in the convergent telecommunication network is formulated. Distribution function of the messages number (or the sequence of messages’ arrival times, or the sequence of intervals between these times, or the sequence of messages number, received during time intervals), the distribution function of the information content in the messages stream, the distribution function of the delivery time of the entire sequence of messages, forming the flow under the study, the function of the information value are researched at the formalization of messages streams.
Key words: Convergent Telecommunication Network – Messages Stream – Formalization – Model – Function.