RU2794711C1 - Method for intensifying convective heat transfer - Google Patents

Abstract

FIELD: intensifying convective heat transfer.

SUBSTANCE: specifically, a method is claimed for intensifying convective heat transfer by moving each heat-exchanging medium along axisymmetric confuser-diffuser channels of variable cross section formed by longitudinally wavy ribs with alternation in each channel of the two-sided suction of the boundary layer with the two-sided injection of the latter from the adjacent channel, due to alternating changes in pressure in the channels along the moving medium. The amount of blowing and suction is regulated by the opening angle of longitudinally wavy ribs in the range from 0° up to 5°, and pulsations are imposed on the flow of the heat-exchanging medium in form of harmonic oscillations by means of a resonator when the flow passes through the right and left channels with different diameters, formed by the location of the flow separator at the inlet of the confuser-diffuser channels.

EFFECT: increase of intensity and efficiency of heat transfer by increasing the efficiency of heat transfer from the channel walls to the heated medium while saving the heat used to heat the heated medium (air).

1 cl, 3 dwg

Description

The invention relates to a method for intensifying convective heat transfer.

The closest method of the same purpose to the claimed invention in terms of the totality of features is the method of intensifying convective heat transfer by moving each heat-exchange medium along axisymmetric channels of variable cross section formed by longitudinally wavy ribs with alternating bilateral suction of the boundary layer with double-sided blowing (see A.S. No. 285938, IPC F28f3 / 02, F28f13 / 02 Method for intensifying convective heat transfer. // Kirpikov V. A., Gutarev V. V., Leifman I. I. - Committee for Inventions and Discoveries under the Council of Ministers of the USSR. 1971) and adopted for the prototype.

The reasons preventing the achievement of the technical result indicated below when using the known method adopted as a prototype include a large consumption of heat used to heat the heated medium (air).

The essence of the invention lies in saving the heat used to heat the heated medium (air).

The technical result is an increase in the intensity and efficiency of heat transfer, an increase in the efficiency of heat transfer from the walls of the channels to the heated medium, as well as saving the heat used to heat the heated medium (air).

The specified technical result in the implementation of the invention is achieved by the fact that in the method of intensifying convective heat transfer, in which, by moving each heat-exchange medium along axisymmetric confuser-diffuser channels of variable cross section, formed by longitudinally wavy ribs with alternation in each channel of the two-sided suction of the boundary layer with the two-sided blowing of the latter from the adjacent channel, due to alternating pressure changes in the channels along the moving medium, the amount of blowing and suction is regulated by the opening angle of the longitudinally wavy ribs in the range from 0° to 5°, and pulsations are imposed on the flow of the heat-exchanging medium in the form of harmonic oscillations by means of a resonator during passage flow through the right and left channels with different diameters, formed by the location of the flow separator at the inlet of the confuser-diffuser channels.

,The law according to which the flow rate of the pulsating flow is changed is written as:

,

- расход, м³/с;

- площадь сечения, м²;

- начальная скорость м/c;

- амплитуда пульсаций, м;

- время, с;

- частота, Гц;

- число

3,14.

- consumption, m ³ / s;

- cross-sectional area, m ² ;

- initial speed m/s;

- pulsation amplitude, m;

- time, s;

- frequency Hz;

- number

3.14.

The drawings show:

in fig. 1 - heat exchange element illustrating the proposed method for intensifying convective heat transfer: 1 - confuser-diffuser channel, 2 - bottom plate, 3 - top plate, 4 - longitudinally wavy fin;

in fig. 2 - section of the heat exchange element: 1 - confuser-diffuser channel, 2 - bottom plate, 3 - top plate, 4 - longitudinally wavy rib, 5 - slot, 6 - pulsator, 7 - right semi-annular channel, 8 - left semi-annular channel, 9 - resonator, 10 - separator;

in fig. 3 - distribution of the heat transfer coefficient along the length of the channel: a - straight channel, b - confuser-diffuser channel, c - confuser-diffuser channel with superimposed pulsations (acceleration), d - confuser-diffuser channel with superimposed pulsations (deceleration).

Fig. 3 illustrates the results of a study of heat transfer in confuser-diffuser channels with and without pulsations (deceleration and acceleration of the flow) and in a straight channel without pulsations.

The heat exchange element for implementing the proposed method for intensifying convective heat transfer contains confuser-diffuser channels 1 formed by the bottom plate 2, the top plate 3 and longitudinally wavy ribs 4 having slots 5 through which the blowing (suction) of the air flow is carried out to intensify heat transfer. Pulsators 6 are installed at the inputs of the confuser-diffuser channels 1, formed from the right semi-annular channel 7, the left semi-annular channel 8, the separator 10 installed between them and the resonator 9, which is a thin plate fixed on the wall of the confuser-diffuser channel 1 behind the semi-annular channels.

Pulsators 6 can be made of metals, alloys or other corrosion-resistant materials.

The separator 10 is made of corrosion-resistant materials in the form of a triangular prism with rounded corners.

When implementing the proposed method for intensifying convective heat transfer, the heated medium (air) is supplied to the confuser-diffuser channels 1. The air enters the confuser-diffuser channels 1, passes through 6 pulsators, whose work is to create air flow pulsations. Pulsations of the air flow are created due to the resonator 9. The air enters the confuser-diffuser channel 1, passes through the semi-annular channels: the right semi-annular channel 7 and the left semi-annular channel 8, meets with the resonator 9 and under the action of the flows that have passed through the semi-annular channels and the separator 10, the resonator 9 starts to wobble. Oscillations of the resonator 9 occur due to the fact that the air flows passing through the right semi-annular channel 7 and the left semi-annular channel 8 have different speeds due to the different flow area of the channels. Since the confuser-diffuser channel 1 connected to the output of the pulsator 6 is made in the form of a confuser formed by longitudinally wavy ribs 4, the pressure behind the pulsator 6 will be higher than the pressure at the initial section of the confuser-diffuser channel 1. The air flow due to the pressure difference will go from the entrance of the pulsator 6 to the confuser-diffuser channel 1 through longitudinally wavy ribs 4. Under the action of pulsators 6, the air flow in the confuser-diffuser channel 1 acquires a pulsating character of movement. Thus, in the confuser-diffuser channels 1, a pulsating flow of the heated medium is realized, which leads to an intensification of heat transfer from the walls of the channels to the heated medium (air) and, accordingly, to a more efficient process of heat transfer. Pulsations of the flow of the heat-exchanging medium have the form of harmonic oscillations.

The opening angle of the longitudinal-wavy ribs 4 is from 0 to 5°, since according to studies [1, 2] at this opening angle, the heat transfer intensity is maximum.

The results of the study of the increase in the efficiency of heat transfer presented in figure 3 show that the intensity of heat transfer in confuser-diffuser channels is 1.8 times higher than in straight channels. In this case, the superimposed flow pulsations in the confuser-diffuser channels lead to an increase in heat transfer by 1.5 times.

Bibliography

1. Terekhov V.I., Bogatko T.V. Peculiarities of heat transfer in an axisymmetric diffuser after a sudden expansion of a pipe // Modern Science: Researches, Ideas, Results, Technologies. 2015. No. 1 (16) . pp. 95-100.

2. Petrova N.P., Tsynaeva A.A. Numerical study of heat transfer in the channel of a heat exchanger with a pressure gradient. Teplovye protsessy v tekhniki. 2019. V. 11, No. 12. S. 532–540.

Claims (1)

A method for intensifying convective heat transfer by moving each heat-exchanging medium along axisymmetric confusing-diffuser channels of variable cross section formed by longitudinally wavy ribs with alternation in each channel of the two-sided suction of the boundary layer with the two-sided blowing of the latter from the adjacent channel, due to alternating pressure changes in the channels along the moving medium , characterized in that the amount of blowing and suction is controlled by the opening angle of the longitudinally wavy ribs in the range from 0° to 5°, and pulsations are imposed on the flow of the heat-exchanging medium in the form of harmonious oscillations by means of a resonator when the flow passes through the right and left channels with different diameters, formed by the location of the flow separator at the inlet of the confuser-diffuser channels.

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