Thermodynamic efficiency of swirling effect: ways of enhancement

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Article

Thermodynamic efficiency of swirling effect: ways of enhancement

Batenok Alina Vladimirovna

Bachelor degree

Far Eastern Federal University

Glushko Natalia Alexandrovna

Senior lecturer

Far Eastern Federal University

Abstract

The paper provides a description of techniques for increasing the efficiency of a triple-flow pipe with finning used under particular conditions. A new method, based on a significant value cutting and changing of Joule-Tompson temperature effect during gas reduction, was tested. Special attention is given to the functional dependence of a heat performance coefficient on a cooled flow. Properties of vortex flows with a temperature stream splitting are described as well. Quasi-isometric state of gas reduction, obtained by the experiment, allows to implement highly effective technological methods of gas expansion without applying expensive hydrate elimination procedures (flow heating or inhibitors).

Key words: swirling effect, gas expansion, triple-flow pipe with finning, flow heating, heat performance coefficient, cooled flow.

Introduction

At present, gas from the fields is transported to residential areas with excessive pressure. Thus, it is necessary to install additional facilities to lower the pressure to the consumer grade. The gas pressure is reduced by expansion (throttling). This method creates favorable conditions for the crystallohydrates formation, which build up at definite temperatures when natural gases are saturated with water vapors. Hydrate deposition leads to clogging of a pipe throat diameter and causes accidents. Hence, the solution of this problem is relevant today and the search of ways for increasing the swirling effect thermodynamic efficiency is important for the petrochemical industry [1, p.9]. Therefore, it was decided to conduct an experiment to evaluate a heat performance coefficient at various pressures of a hot stream depending on a fraction of a cooled flow м.

In accordance with the work objective, the task to conduct an experiment on a laboratory bench and to analyze its results was defined.

Main material

Theoretical basis

The swirling effect (Ranque effect) emerges in a vortex flow of a coercible gas and takes place in a special apparatus called a vortex tube (Figure 1).

Figure 1 - Scheme of a vortex tube [2, p.8]: 1 - bare cylindrical pipe; 2 - spin nozzle; 3 - inlet scroll; 4 - diaphragm; 5 - throttle (valve)

The physical meaning of this effect is the following: when the compressed gas is supplied into the pipe through as pin nozzle of the swirler, the gas is separated by the temperature into two flows. The first is an axial one with the temperature lower than the initial flow, and the second is a peripheral one with the temperature higher than the initial flow [1, p.3].

As the throttle is being closed, the pressure in the vortex tube is boosting. While the rate of the cooled flow is increasing, the rate of the hot one is decreasing respectively. In this case, the temperatures of the flows also change.

Experiment

The compressed air was supplied into a triple-flow vortex pipe TVT-15-1 by opening a valve on the pipeline. In this case, the air pressure at the pipe inlet was set at .

At the beginning, the throttle was put to a position when all the supplied air escaped through it, i.e. , where is the rate of the cooled flow and G1 is the rate of the feed compressed gas(all parameters were measured).

Further, the throttle was adjusted to a position that partially covered the exit area of the peripheral airflow. A part of the compressed air was absorbed by the atmosphere through the throttle. The rest of the air traveled to a smaller radius and went into the atmosphere through the diaphragm of the vortex pipe. The throttle position was not changed for 20-30 min to make the process of the airflow in the vortex tube steady. The indicators of temperature, pressure, and flow rate at the tested points were recorded by The Simp Light software package.

After the recording, the throttle was adjusted to a new position with the reduction of the flow area of the peripheral gas blankets. This mode worked for 30 min, and then the experimental variables were monitored. The vortex pipe operation had been changed until the throttle completely closed the outlet).

The initial analysis of the obtained experimental data showed points with the flow heated to its maximum. Negative temperature difference was recorded at these points: (so a repeated experiment is required).

During the experiment the vortex pipe characteristics were being fixed. The value of the total air pressure at the inlet was in the range of . The pressure of the hot flow varied from 0 to 2,65 atmosphere: The total temperature of the air at the entrance to the pipe was from 21,5 to 25,5°C.

Results

During the experiment, sixteen points were read under the hot flow different pressures, regulated by turning the valve. The relative proportion of the cooled flow varied from 0 to 1.

The experimental data were processed by statistical methods. The dependence curve (Figure 2) represents the reliance of the heat performance coefficient л on the portion of the cooled flow м.

The part of the cooled flow м for each of the sixteen pressure modes was calculated through the trend line, obtained by the graphical correlation of the expansion  (Formula 1) and the portion the cooled flow м.

(1)

where is the total pressure at the inlet to the spin nozzle inlet of the swirler, is the pressure of the substance the cooled flow is escaping into.

Table 1 shows the calculation of the cooled flow portion by a third-degree polynomial: , where , .

Table 1 - Calculation of the cooled flow portion

Source: author's calculation results

The heat performance coefficient л indicates the degree of the flow heating. Maximum heating is observed under the most negative value of the coefficient, calculated by the following formula:

(2)

where is the temperature difference between the inlet and the mixed flow, is the temperature difference of the gas flow at the inlet and after expansion.

(3)

(4)

After carrying more experiments on the maximum (peak) points, new values of the heat performance coefficient, deviated from the starting ones with a permissible error, were received. A graphical display of all experiments is shown on Figure 2. Mean square deviation of this coefficient is calculated in Table 2.

Figure 2 - Functional dependence of the heat performance coefficient on the portion of the cooled flow: 1 - first experiment (7.26.19), 2 - second experiment for 6, 8, 10 points (7.29.19), 3 - second experiment for 7 point (7.30.19), 4 - second experiment for 6, 8 points ( 7.31.19), 5 - second experiment for 6, 7, 8 points (8.01.19)

Table 2 - Heat performance coefficient (л) measurement error

Source: author's calculation results

The functional dependence of the heat performance coefficient on the proportion of the cooled flow is demonstrated in Figure 3 (the average values of the coefficients counted in the additional experiments are used).

Figure 3 - Dependence of the heat performance coefficient on the proportion of the cooled flow

flow heat performance pipe

The analysis of the experimental data results reveals that when changing the weight proportion of the cold flow from to with the temperature effect ascends and reaches its maximum at . The further increase in the weight proportion of the cold flow () causes a significant decrease in the heat flow from the periphery to the center. Consequently, the axial gas layers get cooled and the temperature effect at the diaphragm outlet goes down at [3, с.51]. The experiment substantiates that the pipe with finning warms the flow at a certain proportion of cooled gas (from to ).

References

flow heat performance pipe

1. Kuznetsov V.I. Optimization of vortex tube parameters and methods of its calculation. [Electronic resource]: - L. 1989. - 39 p. Access mode: http://tekhnosfera.com/view/514937/a#?page=1;

2. Piralishvili Sh.A. Vortex effect. Volume 1: Physical phenomenon, experiment, theoretical modeling. [Electronic resource]: - M. 2013. - 337 p. Access mode: https://www.rfbr.ru/rffi/ru/books/o_1916797;

3. Kuznetsov V.I., Makarov V.V. Vortex tube: experiment and theory: - M. - Omsk. 2016. - 240 p.

4. Zhornik M. N., Piralishvili Sh. A., Mogileva A. Experimental internal heat transfer studies in the vortex heating device // Bulletin of the Samara State Aerospace University. 2015. Vol.14, № 2. p. 78-87

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6. Akhmetov Yu.M., Zangirov E.I., Svistunov A.V., Yaminova E.M., Shutikhina K.P. Analysis of mixing parameters of stratified flows in a vortex gas pressure regulator // Bulletin USATU Ufa. 2015. Vol.19, № 4 (70). p. 8-15

7. Zangirov E.I., Mukhametov M.V., Svistunov A.V. , Chindina A.A. Identification of the temperature characteristics of a quasi-isometric vortex gas pressure regulator // Bulletin USATU Ufa. 2013. Vol.17, № 3 (56). p. 103-108

8. Bakirov F.G., Gurin S.V., Distanov R.Yu., Akhmetov Yu.M. Energy saving during the operation of gas transmission and distribution systems due to the use of vortex gas pressure regulators // Problems of collection, preparation and transport of oil and oil products. №1 (71). p. 56-65;

9. Parkhimovich A. Yu., Soloviev A. A. Research of experimental characteristics of the vortex about the regulator // Bulletin USATU Ufa. 2006. Vol.18, №1 (17).

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