Refrigeration engineering and technology

EXERGETIC EFFICIENCY OF TECHNOGENIC CYCLIC AIR COOLING OF THE GAS TURBINE UNIT

2015-12-28T22:21:25+02:00

The deterioration of the fuel efficiency of the gas turbine unit is especially severe when the temperature of the intake air 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 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.

THE ADVISABILITY OF COLD ACCUMULATOR USED IN INDUSTRY

2015-12-28T22:21:25+02:00

The advisability of thermal energy accumulators use 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 designe calculations methodology.

CALCULATING FEATURES OF HEAT GAIN IN A AIR CONDITIONING ROOM

2015-12-28T22:21:25+02:00

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, a comprehensive model for calculating air conditioning including the determination of the optimum parameters defining cost-effective insulation thickness; selection of the air conditioning system

LIFE CYCLE OF LIGHT HYDROCARBONS CATCHING SYSTEM BASED EJECTOR HEAT EXCHANGER

2015-12-28T22:21:25+02:00

In a paper the mode and a procedure of accounts of lifecycle for systems of catching of light fractions of a hydrocarbon on the basis of an ejector heat exchangers are reduce. Thinness of accounts for different systems that it is necessary to allow at projection of devices is display. The introduced procedure of lifecycle allowed evaluating qualitatively a plant at projection and maintenance.

CONDENSATION HEAT TRANSFER INSIDE A HORIZONTAL SMOOTH TUBES. IMPROVEMENT OF HEAT TRANSFER CALCULATING METHOD

2015-12-28T22:21:26+02:00

This paper proposes a method for calculating heat transfer 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 dependences for calculation of the coefficient of friction at the interface between the phases.

TRANSPORT PROPERTIES OF NANOFLUIDS (EXPERIMENT AND CALCULATION METHODS)

2015-12-28T22:21:26+02:00

A review and analysis of experimental studies and methods of calculation 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 – stady-state and transient hot wire methods. 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.

EXPERIMENTAL INVESTIGATION OF THE HEAVY METALS ACCUMULATION IN PLANTS AND PERSPECTIVES OF THESE PLANTS USE FOR PREVENTION OF ENVIRONMENT POLLUTION ON URBANIZATED TERRITORIES

2015-12-28T22:21:26+02:00

In this paper we studied the level of influence of technogenic pollution of soil and air with heavy metals on the condition of the grass cover urban agglomeration. On the example of the city of Nikolayev the ability of plants species Taraxacum officinale Wigg. absorb and accumulate heavy metals from technogenic-polluted environment were analyzed.

COMPARATIVE FIELD EXPERIMENTAL INVESTIGATIONS OF DIFFERENT FLAT PLATE SOLAR COLLECTORS

2015-12-28T22:21:26+02:00

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.

BOILER OUTPUT RESTRICTIONS REMOVAL BY ADJUSTING THE AERODYNAMICS OF BLOWING TRACT ELEMENTS

2015-12-28T22:21:26+02:00

The results of forced steam boiler stations research and modernization. Reconstruction of boilers to reduce pressure loss and increase the output power. Localization of dissipative zones in flow parts by the method of visual diagnostics flow patterns

THERMODYNAMIC CYCLES AND CONTROL RULES FOR WATER CIRCULATING SYSTEMS WITH TRANSPIRATION COOLERS

2015-12-28T22:21:26+02:00

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 analyse 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 fulfil 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.

EXPERIMENTAL WAY OF FIGURING OXYGEN EVAPORATION RATES IN ROCKET CYLINDRICAL TANK UNDER NATURAL CONDITIONS

2015-12-28T22:21:26+02:00

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 ~500K. The total avg-integral aerodynamic heat flow into oxygen ~16 KWt/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.

HEAT PUMP TECHNOLOGY – POTENTIAL IMPACT ON ENERGY EFFICIENCY PROBLEM AND CLIMATE ACTION GOALS WITHIN UKRAINIAN ENERGY SECTOR

2015-12-28T22:21:26+02:00

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.

MODELLING OF STATIC MODES FUNCTION OF THE REFRIGERATION CENTRIFUGAL COMPRESSOR

2015-12-28T22:21:26+02:00

The aim of our scientific work is to improve the accuracy of static modes simulation of the centrifugal compressors operation. To achieve this scientific aim we have carried out the models designing the centrifugal compressors characteristics. 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 is realized in MATLAB\Simulink program presented in this article. The modern achievements review in the field of centrifugal compressors modeling is presented. We have substantiated the necessity of the centrifugal compressor modeling in this paper. 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. We have also presented the alternative compressor model. This realized model is based of 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 characteristics set received as a result modeling is shown in this article. It is presented twelve characteristics in axes. The pressure ratio and the refrigerant flow denote 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. We have presented the simulation results comparison obtained in the various models. We have presented the conclusions about the optimal methods of the synthesis model.

MODERN TOOLS DATA ANALYSIS IMPLEMENTATION FOR PROCESSING PARAMETERS OBTAINED IN AIR CONDITIONING AND REFRIGERATION UNITS. PART 1

2015-12-28T22:21:26+02:00

The paper discusses the modern tools data analysis, their main types and properties, identify those which can be used in the processed data and indicators obtained from scientific and industrial experiments. The article is the first part, among a series of articles devoted to the theoretical basis of modern methods of data analysis and their possible application in the power engineering industry.

CRUDE OIL DISTILLATION COLUMN MULTIVARIABLE MODELS SET FOR ROBUST CONTROL SYSTEMS DESIGN

2015-12-28T22:21:26+02:00

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. The article describes the set of linear mathematical dynamical models of multi-component crude oil atmospheric distillation column K-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

FEATURES SWITCHING OF OPTICAL SIGNALS USING DIFFERENT MODES OF IN-FORMATION TRANSFER

2015-12-28T22:21:26+02:00

In work the analysis of switching optical signals with electrical and optical control and requirements for switching systems that provide increased bandwidth telecommunication network. The model is considered and methods of implementing all-optical switching, do not use electro-optical and optoelectronic conversion of the information signal and does not require buffering of optical signals in all-optical switching device. Evaluated the feasibility of using different modes of information transfer for switching optical signals. The advantages and disadvantages of the methods label and position multiplexing. Describes a model of optical network with all-optical switching blocks of information. Expediency is proved to use for the task of block mode transfer information.