EXPERIMENTAL STUDY OF INFLUENCE OF FINE DROP MOISTURE AND CONTAMINANTS IN HEAT CARRIER ON COEFFICIENT OF HEAT REMOVAL OF VORTEX HEAT EXCHANGER OF GAS CONTROL STATION HEATING SYSTEM

Ekaterina Gennadievna Pakhomova Southwest State University, Faculty of Construction and Architecture, Department of Industrial and Civil Construction, Kursk, Russian Federation Grigorova Natalia Pavlovna Southwest State University, Faculty of Construction and Architecture, Department of Heat, Gas and Water Supply, Kursk, Russian Federation Monastyrev Pavel Vladislavovich Tambov State Technical University, Institute of Architecture, Construction and Transport, Department of Urban Construction and Motorways, Tambov, Russian Federation


INTRODUCTION
The relevance of energy saving and environmental safety issues in the construction and operation of buildings for various purposes is no doubt [1,2,3,4,5]. This also applies to small production buildings. For example, a feature of gas control station operation is gas pressure control which is coming from the line to consumers. It is necessary to install pressure regulators for this purpose. These regulators should operate at a suffi ciently high difference of input and output pressure values (from 3.5 and more times) with unclaimed repayment of excess energy. The use of a signifi cant potential of pressure drop energy between natural gas pipelines [6,7] is possible when using a vortex heat exchanger, which can be used as an element of the heating system of gas distribution room.
Such heating method of this room heating makes it possible to avoid installation of autonomous sources of heat energy, which allows to reduce fuel costs, reduce emissions of pollutants into the environment, as well as to provide more comfortable operating conditions of pressure regulator due to difference reduction of controlled gas pressure supplied to the consumer. The process of heat exchange in vortex heat exchange apparatus at the fl ow of twisted gas fl ow is characterized by two sections (at the inlet and outlet of the swirler in heat exchange apparatus). At swirler inlet fl ow structure and patterns of heat and mass exchange are determined depending on method and intensity of initial swirling of heat carrier. The process of heat exchange during swirling of gas fl ow in the form of ideal gas in the swirler is studied in details [8,9,10,11,12]. However, under real conditions, swirling gas is always saturated with moisture and contaminants. As heat carrier moves from inlet to outlet sections of swirler made in the form of converging nozzle, concentration of phase particles of moisture and contaminants is redistributed to periphery of twisted fl ow of natural gas. This leads to an increase in adhesion frequency of the separate liquid particles and contaminants, their consolidation, as well as to a sharp activation of both impact and sliding contacts with narrowing surface. As a result, there is a random distribution of evaporation heat on the heat exchange surface. This makes it diffi cult to form mathematical model to determine the amount of increase in heat transfer coeffi cient characterizing the degree of heat transfer intensity. This issue can only be solved using experimental studies of changes in evaporation temperature at different fl ow parameters of heat carrier, as well as change in heat transfer coeffi cient on swirler blades in vortex heat exchanger when there is fi ne drop moisture and specifi c contaminants in heat carrier.

MATERIALS AND METHODS
Experimental study of heat exchange process on swirler blades in vortex heat exchange apparatus under the infl uence of fi ne drop moisture and contaminants was carried out in two stages. At the fi rst stage, analysis of experimental values of coolant temperature decrease was carried out due to heat extraction for liquid evaporation on the surface of swirling blade of swirler and coeffi cient of heat removal in vortex heat exchange apparatus. This study was conducted under idealized conditions where no contamination was present in natural gas in contact with water. Such an experiment was necessary to determine heat transfer At the second stage, heat transfer coeffi cient was studied under conditions close to actual operating conditions of vortex heat exchange element, when fi ne moisture and specifi c contaminants are present in natural gas in contact with water. This experiment makes it possible to simulate real conditions of vortex heat exchanger operation in work room of gas control station.
Experimental research was carried out at a laboratory plant simulating heating element of heating system of an industrial building -gas control station. Figure 1 shows schematic diagram of the experimental installation.

RESULTS
As a result of the fi rst stage of this experimental study, it was found that experimental values of coolant temperature decrease due to heat extraction for liquid evaporation on the surface of swirling swirler blade in vortex heat exchanger are slightly different from those proved theoretically. These values mainly decrease (Table 1). It was necessary to maintain initial temperature, relative humidity of heat carrier under study and to saturate it with fi ne moisture in order to measure heat transfer coeffi cient. This was done in climate chamber by a nozzle. Experimentally obtained heat transfer coeffi cient values were averaged (for four experiments). Table 2 shows these values. Analysis of heat transfer coeffi cient values, obtained  experimentally and calculated theoretically, shows their satisfactory convergence. This convergence is in measurement error and data calculation. This happens at idealization of wet coolant and "spot" of liquid without taking into account chemical and physical state of coolant in real conditions of gas supply to consumers. Theoretically expected (solid line curve) and experimentally obtained (dashed line curve) change of heat transfer coeffi cient under the "spot" of liquid on the surface of swirler blade was defi ned for specifi ed fl ow rate, measured coolant temperatures, coolant pressure and relative humidity ( Figure 2). As a result, it was revealed that fi ne moisture bombards the "spot" of liquid and as a result, due to those liquid particles that are ripped out when the fi ne moisture hits its "spot" on the surface of the swirler blade, there is a random distribution of evaporation heat in boundary layer above the "spot" of liquid. Therefore, the presence of fi ne moisture in the heat carrier stream intensifi es heat exchange of evaporation, which leads to pulsating change in the heat transfer coeffi cient, wherein the distribution of pulsations in boundary layer of the "spot" of liquid depends along with temperature and on saturation of the heat carrier with drip moisture. Note: mass fl ow of coolant G, kg/s; diameter of "spot" The research of fi ne moisture impact process on thermolysis coeffi cient in vortex heat exchanger at various temperature conditions showed that availability of disperse moisture up to 6 g/m 3 (match up the intake of natural gas from main gas pipelines into gas control point) increases thermolysis coeffi cient in 1,4÷1,9 times. Heat transfer coeffi cient also increases as temperature of heat carrier entering vortex heat exchanger increases. This happens due to the decrease in the surface tension of the "spot" of liquid.
Then experimental studies on intensifi cation of heat removal coeffi cient of heat carrier in contact with "spot" of liquid on the surface of swirler blade at its bombardment with dispersed contaminants were carried out. Heat transfer coeffi cient increases to the maximum value at d r = 3 g/m³ when there are contaminants. Then it falls a little and at a weight of 5 g/m 3 remains constant. This process is shown on Figure 3. This complexity of the change in heat transfer coeffi cient is explained by the following. Increasing mass of contaminants together with changing area increases time interval of evaporation process by volume of boundary layer. There is surface process of evaporation by diameter of "spot" of liquid and spectral process of evaporation by volume of boundary layer. This is a result of contact of "spot" of liquid with heat carrier. If contamination in the heat carrier is more than 4 g/m³, only a surface evaporation process is observed, because the thickness of the "spot" of the liquid is commensurate with a boundary layer on swirler blades. This minimizes the effect of volume evaporation, because part of the liquid is demolished by the heat carrier fl ow into the inside of vortex tube housing.
The following facts are defi ned during the experimental study of changes in heat-and mass exchange above the contact surface of the "spot" of the liquid in continuous fi xation of the evaporation temperature by the automatic potentiometer KSP-4-10.
The evaporation temperature increases with pulse bursts as the concentration of contaminants that bombard the mirror of liquids increases. This is due to probability-random ingress of evaporating drops of moisture on differential thermo steam. Therefore, there is confi rmation of theoretical prerequisites for intensifi cation of cooling process of heat carrier in contact with liquid during bombing of condensate spot mirror by specifi c contamination of pipelines.

CONCLUSIONS
Experimental study of fi ne drip moisture infl uence and specifi c contaminants in heat carrier on heat transfer coeffi cient on swirler blades in vortex heat exchange apparatus of heating system in gas control station was carried out. It is stated that availability of disperse moisture increases thermolysis coeffi cient in 1,4÷1,9 times. Heat transfer coeffi cient also increases as the temperature of the heat carrier entering the vortex heat exchanger increases. This happens due to the decrease in the surface tension of the "spot" of liquid. Evaporation temperature increases with pulse bursts as the concentration of contaminants bombarding the mirror of liquids increases. This is due to probability-random ingress of evaporating drops of moisture on differential thermo steam. Therefore, there is confi rmation of theoretical prerequisites for intensifi cation of cooling process of heat carrier in contact with liquid when bombing the condensate spot mirror by specifi c contaminations of pipelines. Analysis of laboratory-industrial study of thermodynamic stratifi cation of natural gas in elements of vortex heat exchange device confi rms legality of obtained scientifi c provisions of heat-moisture treatment of heat carrier in conditions of its pressure decrease before natural gas supply to consumers. It also confi rms possibility of using vortex heat exchange device in heating system of gas control stations. It can be stated that the use of vortex heat exchanger in heating system of gas control station will allow to save natural gas as fuel in heating system of gas control station, eliminating the need to install autonomous water heaters, in which water heating is carried out by gas combustion; provide more comfortable operating conditions of pressure regulator due to reduction of variable pressure difference of gas supplied to the consumer, as there is a signifi cant decrease in output pressure due to operation of vortex pipe as a heat exchanger of the heating system in buildings.