Volume 51 Issue 6
Section 1. Refrigeration engineering
V. M. Arsenyev, V. V. Miroshnichenko, N. A. Borisov
Exergetic efficiency of technogenic cyclic air cooling of the gas turbine unit
The deterioration of the fuel efficiency of the gas turbine unit is especially severe when the temperature of the intake air is 30°C and above. A significant increase in the thermodynamic efficiency of the gas turbine unit can be provided by the anthropogenic impact on the temperature and humidity of the intake air, which leads to a proportional reduction of the energy consumption for the compressor drive. Maintenance of lower temperatures of the intake air is especially important for the climatic conditions of gas producing countries in North Africa and the Middle East. Gas turbine plant has a large discharge energy potential, which can be utilized for the production of cold with a clear choice of the cooling method by using absorption refrigeration machines. To compare different combinations of gas turbine unit and waste heat recovery refrigeration machines it is advisable to use exergy method of thermodynamic analysis. During the exergy analysis of gas turbine units by using of absorption refrigerating machines it is necessary to take into consideration that the reset of thermo transformed heat flows requires a supply of electricity to drive pumps and fans in the recycling water supply system and to drive the pumps, the hot coolant and pumps in the intermediate circulation loops of heating the coolant and cooling water to the air cooler in the evaporator. Exergetic evaluation of the degree of excellence of gas turbine unit with absorption refrigeration machine was made based on the methodology set out in the work of the scientific school J. Tsatsaronis. This work presents an exergy analysis of cooling efficiency of cyclic air suction in the gas turbine unit by using of lithium bromide absorption refrigerating machine with taking into account of the flow resistance of the air cooler. The results of exergetic efficiency of technical complex of gas-turbine unit with an absorption refrigeration machine were compared with the gas turbine unit without cooling air to the compressor suction. It is also shown that when you increase the flow resistance of the air cooler the growth of efficient cooling power and exergy efficiency of the gas turbine unit stops.
Keywords: gas turbine unit; cooling of air; exergetic efficiency.
R. Gryshchenko, A. Forsiuk, Ya. Zasiadko, O. Pylypenko
The advisability of cold accumulators utilization in industry
The advisability of thermal energy accumulators’ utilization in food industry is presented and substantiated in the article. The time graphs of energy consumption for some plants along with the plots of electrical energy payments within a single- triple-zones tariffs as characteristic for the “Danone” diary plant in the city of Kherson have been analyzed. The results obtained have proved that the effectiveness of cold accumulators application is greatly determined not only by the available time of ice accumulation, but also by the achievable speed of the ice melting, which, eventually, determines the amount of ice which is necessary to generate during the accumulator “charge” period. The proposed considerations will be used at the developing of an ice accumulator design calculations methodology.
Keywords: heat transfer; heat flux; ice accumulator; cold accumulator; water ice; melting ice water.
N. V. Zhikhareva
Calculating features of heat gain in an air conditioning room
The paper deals with the calculation of heat gains especially in the design of air conditioning systems for buildings. The features of calculating the heat and humidity loads: calculation of heat gains through the fence taking into account the direct and scattered radiation in view of the delay and heat gains from various sources. According to research data, a comprehensive model for calculating air conditioning has been carried out including the determination of the optimum parameters; defining cost-effective insulation thickness; selection of the air conditioning system.
Keywords: heat and humidity loads; lag; solar radiation; air conditioning; air flow.
V. E. Kogut, I. D. Butovskyi, V. M. Bushmanov, M. G. Khmelniuk
Life cycle of light hydrocarbons catching system on the ejector heat exchanger base
In a paper the mode and a procedure of lifecycle calculation for systems of hydrocarbon light fractions catching on the ejector heat exchangers basis are given. The details of calculations for different systems that are necessary to take into consideration in the process of devices design. The introduced methodology of lifecycle makes it possible to evaluate the object qualitatively at on the stage of design and maintenance.
Keywords: lifecycle; light cuts of a hydrocarbon; ejector heat interchangers; Monte-Carlo method; Parreto-diagrams.
V.G. Rifert, P.A.Barabash, V.V. Gorin, V.V. Sereda
Condensation heat transfer inside a horizontal smooth tubes. Improvement of heat transfer calculating method
This paper proposes a method for heat transfer calculation during condensation inside horizontal tubes based on the theory of film condensation with substantiation of the basic defining the process systems and the improvement of the dependencies for friction coefficient calculation at the interface between the phases.
Keywords: Condensation inside horizontal tubes; Estimated dependencies justification; Heat transfer calculation method; Model of film condensation
Section 2. Power engineering and energy saving
G. Chen, A. Doroshenko, K. Shestopalov, I. Mladionov, P. Koltun
Comparative field experimental investigations of different flat plate solar collectors
Full-scale traditional metal solar collectors and solar collector specimens fabricated from polymeric materials were investigated in the present study. A polymeric collector is 67.8% lighter than a traditional metal solar collector, and a metal solar collector with transparent plastic covering is 40.3% lighter than a traditional metal solar collector. Honeycomb multichannel plates made from polycarbonate were chosen to create a polymeric solar collector. A test rig for the natural circulation of the working fluid in a solar collector was built for a comparative experimental investigation of various solar collectors operating at ambient conditions. It was shown experimentally that the efficiency of a polymeric collector is 8–15% lower than the efficiency of a traditional collector.
Keywords: Solar collector; Test rig; Hot water supply system; Polymeric materials.
E. Arsiriy, V. Smyrnona, D. Panich
Boiler output restrictions removal by adjusting the aerodynamics of blowing tract elements
Boilers KVGM type often used in heating systems of cities. Analysis of the operating parameters of the boiler showed that most KVGM operate with limited power, that is, the maximum boiler output by 15-30% lower than the nominal.During low-temperature district heating systems do not provide a comfortable environment in apartments because of the limitations of power boilers. One of the main reasons for the limitations of power boilers is insufficient capacity fans or smoke exhausts. The analysis of options to improve performance by increasing the fan speed of rotation of the impeller, or increase its diameter. These two options increase the performance of the fans based on the existing rules of design wind systems. Analysis of the results showed that the efficiency of the compressors in both cases keeps the predetermined high value, but significantly increases the unit cost of electric power. For KVGM-50 boilers developed and implemented energy-saving version of the lifting of restrictions boiler output without replacing the fan, but only by adjusting the aerodynamics flow paths. Increased productivity by reducing the fan flow resistances pieces of auxiliary equipment can increase the boiler output while reducing the cost of electric power to the fans.
Keywords: Boilers; Power Limitation; Fans; Flow visualization; Flow structure design.
S.K. Sosnovskii, V.P. Kravchenko
Thermodynamic cycles and control rules for water circulating systems with transpiration coolers
The analysis of existing regulatory designing documents on chimney-type and mechanical-draft water cooling towers is carried out. It is shown the documents are out of date and to be improved. The efficiency criteria for water circulating systems (WCS), such as the mass transfer coefficient, efficiency factor of fill packing and cooling curves are lost their applied significance and no condition to solve appropriate problems. To analyze WCS with different coolers, the thermodynamic cycles in the Temperature-Time plot are introduced. The thermodynamic efficiency of WCS, which is equal to temperature difference to cooled water temperature ratio is proved as the integral efficiency index. Diagrammatical thermodynamic cycles for WCS with a cooling tower, sprinkling basin or cooling pond are adduced and comprehensive analysis of their specific operation features is carried out. Three rules for WCS control are formulated: 1) When putting into operation and removal from service of a heat exchanging equipment, it is necessary to observe the equation of a resulting water temperatures drop in both heaters and coolers; 2) The cooler hydraulic load variation without its efficiency decrease, is allowed only within the operation range of its individual performance; 3) The WCS thermodynamic efficiency drop under production and ambient conditions is an evidence necessity to fulfill required maintenance or to repair proper equipment. On the basis of the suggested thermodynamic cycles and their analysis a comparative estimation of cooling towers, the sprinkling basin and cooling ponds is carried out. The transpiration coolers disrepairings which influence the WCS operation efficiency require their timely elimination are indicated.
Keywords: roles for water circulating systems control; on chimney-type and mechanical-draft water cooling towers; thermodynamic cycle; thermodynamic efficiency
Yu. Mitikov, S. Kubanov
Experimental way of oxygen evaporation rates figuring in rocket cylindrical tank under natural conditions
Study relates to rocket engine liquid oxygen fuel systems. The evaporation of oxygen was determined in ~5 long cylindrical tank. Experiments were taken under natural conditions. The tank was fuelled with boiling oxygen. The tank pressurization during flight was done with hot helium. It was input into tank as centralized jet with ~180 m/sec speed and mass average temperature ~500 K. The total avg-integral aerodynamic heat flow into oxygen ~16 KW/sq.m. The inner tank surface is waffled (mechanical milling). The gas temperature in free tank volume was measured in 25 spots using rods. The amount of free volume in tank was determined using fuel usage control system. The oxygen upper layer temperature inside the tank reaches the saturated vapour temperature by the middle of the flight when the absolute gas pressure is 1.3-1.5 bar. Oxygen evaporation insignificant speed was determined during engine working time (less than 1kg/sec). The correlation between evaporation speed and the value of aerodynamic heat flow was not determined. The likely reason is tank inner waffled surface and the presence of the power cone. The highest evaporation speed was measured in the beginning of the pressurization system functioning. The hot helium flow interacts with oxygen surface at that time. The necessity to decrease helium input speed was shown.
Keywords: The mass average gas temperature, boiling oxygen, temperature rods, partial pressure, hot helium, aerodynamic heat, oxygen evaporation speed.
O. Ostapenko, P. Stoyanov, O. Yakovleva, M. Khmelniuk
Heat pump technology – potential impact on energy efficiency problem and climate action goals within Ukrainian energy sector
The increasing demand of energy sources for urban, household and industrial facilities requires strategies development for seeking new energy sources. In recent years an important problem is to have energy storage, energy production and energy consumption which fulfill the environment friendly expectations. A lot of attention is devoted to renewable energy sources. One of the most attracting among them is energy production form geothermal sources. At a few meters below the earth’s surface the underground maintains a constant temperature in an approximation through the year allowing to withdraw heat in winter for heating needs and to surrender heat during summer for air-conditioning purposes. Heat pump is a rapidly developing technology for heating and domestic hot water production. Using ground as a heat source, heat exchange is carried out with heat pumps compound to vertical ground heat exchanger tubes that allows the heating and cooling of the buildings utilizing a single unit installation. Heat pump unit provides a high degree of productivity with moderate electric power consumption.In this paper a theoretical performance study of a vapor compression heat pump system with various natural and synthetic refrigerants (HFCs) is presented. Operation mode of the heat pump unit was chosen according to European Standard EN14511-2:2007 and EN255-2. An influence of discharge temperature on system performance was evaluated at different boiling temperatures. The comparison of mass flow rate and coefficient of performance for considered refrigerants at constant cooling capacity and condensation temperature was performed.
Keywords: new energy sources, heat pump; natural refrigerant; discharge temperature; coefficient of performance; ground source heat pump.
Section 3. Refrigerating and accompanying technologies
V.Z. Geller, N. A. Shimchuk, S. N. Gubanov
Transport properties of nanofluids: experiment and calculation methods
A review and analysis of experimental studies and calculation methods of thermal conductivity and viscosity of nanofluids with Al2O3 particles are presented. Analysis of published data shows that the results are not consistent. The greatest influence on the thermal conductivity and viscosity of nanofluids make a concentration of the nanoparticles. In addition to concentration, a major factors influencing the transport properties are the following: a method of producing nanofluids and the methods of their preparation for the research; the size and shape of initial nanoparticles; the ability of the nanoparticles to form clusters with different size; temperature and pressure; surface–active substances (surfactants); type and properties of the base fluids; the methodology of the experiment and its adaptation to the specifics of nanofluids. The results of experimental research of thermal conductivity and viscosity for the model system isopropyl alcohol – Al2O3 nanoparticles at various nanoparticle concentrations and temperatures are given. Study of thermal conductivity was carried out by two independent methods – steady-state and transient hot wire ones. The viscosity was measured with the capillary viscometers. The influence of nanoparticles additives on the viscosity of refrigeration compressor oil is also studied. The results of the measurements are presented in the form of simple models.
Keywords: Thermal Conductivity; Viscosity; Nanofluid; Isopropyl alcohol; Al2O3; Compressor oil
А. L. Tsykalo, А. М. Коsmacheva, V. М. Smirnov
Experimental investigation of the heavy metals accumulation in plants and perspectives of these plants utilization for environment pollution on urbanizated territories prevention
The level of influence of technogenic pollution of soil and air with heavy metals on the condition of the grass cover urban agglomeration had been studied in this paper. On the example of the Nikolayev city the ability of Taraxacum officinale Wigg plants to absorb and accumulate heavy metals from technogenically polluted environment were analyzed.
Keywords: heavy metals, industrial pollution, soil contamination, dandelio
Section 4. Automatic, computer and telecommunication technologies
A. Gurskiy, V. Denisenko, A. Goncharenko
Modelling of refrigeration centrifugal compressor static modes operation
The aim of the scientific work is to improve the accuracy of static modes simulation of the centrifugal compressors operation. To achieve this scientific aim the models designing the centrifugal compressors characteristics have been carried out. These characteristics must be obtained at various speeds of rotation and the angles of the vanes of the diffuser. The model of the refrigeration centrifugal compressor presented in this article is realized in MATLAB\Simulink program. The modern achievements review in the field of centrifugal compressors modeling is presented. The necessity of the centrifugal compressor modeling has been substantiated. The tabular data describing static characteristics of the compressors is shown. These tabular data are determined in the Lookup Table blocks. The model is represented by these blocks in the MATLAB\Simulink program. The alternative compressor model has been also presented. This realized model is based on the interpolation spline functions. This alternative model is presented in the DC-Net program. DC-Net program is destined for modeling and research of the logical-dynamic systems. The centrifugal compressors model is presented in the DC-Net program as the logical-dynamic systems. The compressor static characteristic set received as a modeling result is shown. Twelve characteristics in axes are presented. The pressure ratio and the refrigerant flow are denoted on the axes. These static characteristics can be compared with experimental characteristics to assess the model adequacy. The assessment of the model adequacy is realized on the basis of the simulation results comparison. Simulation results comparison obtained in the various models is presented. The conclusions about the optimal methods of the model synthesis are given.
Keywords: Centrifugal compressor - Refrigerating machinery – Turbocompressor plant –Static characteristics of the compressor – Model of the compressor
O. Olshevska, A. Selivanova
Data analysis software tools for processing of parameters obtained in air conditioning and refrigerating unitsimplementation. Part 1
Current software tools for data analysis, their main types and properties are considered in the paper, those which can be used at the processing of data and parameters obtained as a result of scientific and industrial experiments are identified. This is the first part of the series of articles dedicated to the fundamentals of data analysis modern methods and their possible application in the power engineering industry.
Keywords: data mining; air conditioning systems; temperature, pressure; software tools
Crude oil distillation column multivariable models set for robust control systems design
Classical automatic control systems of crude oil distillation columns are used to stabilize indirect parameters (temperature, pressure, level) which are considered as independent. Such systems can be used in case of small disturbances and fluctuation of oil composition. Thearticledescribes thesetoflinearmathematicaldynamicalmodelsofmulti-componentcrude oilatmosphericdistillationcolumnK-2 which is based on direct parameters of material balance. For development of modern multivariable automatic control systems it’s preferable to use direct material balance parameters because change of products flow ratios leads to economical loses. Developed models shows that the plant is significantly multivariable with big lag, so effective automatic control system can be designed only with use of modern control theory. The developed set of models can be used for research of robustness and quality of multivariable automatic control systems (optimal, suboptimal, model-predictive, etc) of crude oil distillations columns which oriented on material balance parameters.
Keywords: mathematical model; crude oil; distillation column; robustness; material balance.
G. S. Gayvoronska, B. A. Rybalov
Features of optical signals switching at using different modes of information transfer
The analysis of optical signals switching with electrical and optical control and requirements for switching systems that provide increased bandwidth telecommunication network is presented in the paper. The model and methods of implementing all-optical switching, which do not use electro-optical and optoelectronic conversion of the information signal and do not require buffering of optical signals in all-optical switching device are considered. The feasibility of using different modes of information transfer for switching optical signals has been estimated. The benefits and limitations of the label and position multiplexing methods are shown. A model of optical network with all-optical switching blocks of information has been described. The block mode of information transfer usage expediency for theassigned task is proved.
Keywords: all-optical network; information transfer mode; multiplexing.