CN113008067B - A Prediction Method for Tube Bundle Vibration Induced by Two-Phase Flow in Submerged State - Google Patents

Abstract

The invention discloses a method for predicting the vibration of two-phase flow-induced tube bundles in a submerged state. By calculating the total time from generation to rising of bubbles in the i-th row of heat exchange tubes in the submerged state, the gas volume in the coverage area of the i-th row of heat exchange tubes is calculated. , effective liquid volume, total gas fraction, effective vapor fraction, total liquid fraction, effective liquid fraction, average density of two-phase flow, cross-flow velocity and critical fluidity of two-phase flow in the i-th row of heat exchange tube gaps , and the periodic vortex amplitude and turbulent buffeting amplitude of the i-th row of heat exchange tubes, and then determine whether the i-th row of heat exchange tubes is damaged by vibration. The prediction method of the present invention can be applied to the tube bundle vibration prediction of equipment such as reboilers, condensers, evaporators, nuclear reactors, etc., which work in the submerged state, and can guide the design of anti-vibration structures, and have a great impact on the design of equipment structures. It has great practical and reference significance for safe operation.

Description

A Prediction Method for Tube Bundle Vibration Induced by Two-Phase Flow in Submerged State

technical field

The invention relates to the technical field of tube bundle vibration prediction, in particular to a method for predicting tube bundle vibration induced by two-phase flow in a submerged state.

Background technique

With the continuous development of large-scale heat exchange equipment, the problems of fluid-induced tube bundle vibration have emerged one after another, which have seriously affected the reliable operation of heat exchange equipment. For the vibration induced by the single-phase fluid flowing laterally through the straight tube bundle, both GB151 and TEMA standards have given complete and feasible calculation methods. However, for shell-and-tube heat exchangers such as reboilers, condensers, and nuclear reactors Due to the complexity of the actual working conditions, there are too many factors affecting the vibration of the two-phase flow-induced tube bundle, the flow parameters at specific positions are different, and the influence of the immersion medium on the vibration of the two-phase flow-induced tube bundle is not clear. Aiming at the problem of tube bundle vibration induced by two-phase flow in such submerged heat exchangers, there is no systematic and feasible vibration prediction method, which seriously affects the anti-vibration structure design of such equipment.

Contents of the invention

In order to overcome the above-mentioned defects in the prior art, the present invention provides a method for predicting the vibration of the tube bundle induced by two-phase flow in the submerged state, which can be applied to shell-and-tube heat exchangers working under the submerged state, such as reboilers and condensers The vibration prediction of tube bundles of equipment such as evaporators, nuclear reactors, etc. can guide the design of anti-vibration structures, and has great practical and reference significance for equipment structure design and safe operation.

To achieve the above object, the present invention adopts the following technical solutions, including:

A method for predicting tube bundle vibration induced by two-phase flow in an immersed state, comprising the following steps:

S1. Calculate the characteristic factor of the vibration of the two-phase flow induced tube bundle, that is, the i-th row of heat exchange tubes in the submerged state, including:

S11, the total time t from the bubble generation to the rising of the i-th row of heat exchange tubes, the calculation method is as follows:

t=1/f;

In the formula, D _b represents the diameter of the bubble shedding; θ represents the contact angle between the bubble and the wall; σ represents the surface tension of the shell-side liquid; ρ _L represents the liquid density; ρ _g represents the gas density; f represents the frequency; g represents the acceleration of gravity;

S12, the gas volume V _gi within the coverage of the i-th row of heat exchange tubes in the submerged state, the calculation method is as follows:

Gas volume flow rate within the coverage area of the first row of heat exchange tubes

Gas volume flow rate within the coverage area of the second row of heat exchange tubes

The gas volume flow rate within the coverage area of the i-th row of heat exchange tubes

The gas volume V _gi =Q _gi t within the coverage of the i-th row of heat exchange tubes;

In the formula, Q _g represents the total volume flow rate of gas; n ₁ represents the number of heat exchange tubes in the first row; n _i represents the number of heat exchange tubes in the i-th row; n represents the total number of heat exchange tubes in the heat exchange equipment, n= n ₁ +n ₂ +n ₃ +…+n _i +…;

S13, the effective liquid volume V _Li within the coverage of the i-th row of heat exchange tubes in the submerged state, the calculation method is as follows:

V _Li =Q _Li t;

Q _Li =Q _gi ρ _g /ρ _L ;

In the formula: Q _Li represents the effective liquid volume flow within the coverage of the i-th row of heat exchange tubes;

S14, the total gas content ε _gii and the effective gas content ε _gi within the coverage of the i-th row of heat exchange tubes in the submerged state are calculated as follows:

ε _gi =V _gi /(V _gi +V _Li );

In the formula, V _i represents the shell side volume within the coverage of the i-th row of heat exchange tubes;

S15, the total liquid content ε _Lii and the effective liquid content ε _Li within the coverage of the i-th row of heat exchange tubes in the submerged state, the calculation method is as follows:

ε _Li =V _Li /(V _gi +V _Li );

S16, the average density _ρTPi of the two-phase flow within the coverage of the i-th row of heat exchange tubes in the submerged state, the calculation method is as follows:

ρ _TPi = ρ _L ε _Li + ρ _g ε _gi ;

S17, the cross flow velocity v _TPi of the two-phase flow in the tube gap of the i-th row of heat exchange tubes in the submerged state, the calculation method is as follows:

In the formula, F _si represents the total cross-sectional area of the i-th row of heat exchange tube shell-side fluid flow; F _si (ε _gii +ε _Lii ) represents the effective cross-sectional area of the i-th row of heat exchange tube two-phase flow;

S18, the critical fluidity v _C in the tube gap of the i-th row of heat exchange tubes in the submerged state, the calculation method is as follows:

In the formula, K represents the instability coefficient; a represents the index; d represents the outer diameter of the heat exchange tube; δ ₁ represents the logarithmic decay rate; f ₁ represents the first-order natural frequency of the heat exchange tube; total mass;

S19, the periodic vortex amplitude y _s and the turbulent buffeting amplitude y _t of the i-th row of heat exchange tubes in the submerged state, the calculation method is as follows:

In the formula, C _L represents the lift coefficient;

normalized power spectral density

The mass flow rate of the two-phase flow of the i-th row of heat exchange tubes: W _Gi = ρ _TP v _TPi ;

Power spectral density S _F =NPSD(W _Gi d) ² ;

In the formula, C ₁ represents the coefficient, and the value of C ₁ is 0.4213;

S2. According to the characteristic factor of the vibration of the i-th row of heat exchange tubes induced by the two-phase flow in the submerged state, it is judged whether the i-th row of heat exchange tubes will be damaged by vibration; the types of vibration include: vibration induced by periodic vortex shedding, Vibration induced by turbulent buffeting, elastic vibration.

In step S2, it is judged whether vibration induced by periodic vortex shedding, vibration induced by turbulent buffeting, and elastic vibration will occur in the i-th row of heat exchange tubes, the specific method is as follows:

S21, the judgment about the vibration induced by periodic vortex shedding is as follows:

Determine whether the total gas content ε _gii of the i-th row of heat exchange tubes in the submerged state is greater than or equal to 15%, if yes, the vibration induced by periodic vortex shedding will not occur; if not, the vibration induced by periodic vortex shedding may occur , further judgment is required to determine whether the periodic vortex amplitude y _s of the i-th row of heat exchange tubes in the submerged state is less than or equal to 0.02 times the outer diameter of the heat exchange tubes. If so, the vibration induced by periodic vortex shedding will not occur. If If not, vibrations induced by periodic vortex shedding will occur;

S22, the judgment on the vibration induced by turbulent buffeting is as follows:

Determine whether the turbulent buffeting amplitude y _t of the i-th row of heat exchange tubes in the submerged state is less than or equal to 0.02 times the outer diameter d of the heat exchange tubes, if yes, the vibration induced by turbulent buffeting will not occur; if not, turbulent flow will occur buffeting-induced vibration;

S23, the judgment on elastic vibration is as follows:

Determine whether the two-phase flow cross flow velocity v _TPi in the tube gap of the i-th row of heat exchange tubes is less than or equal to the critical flow velocity v _C in the submerged state. If yes, elastic vibration will not occur; if not, elastic vibration will occur.

The advantages of the present invention are:

(1) The present invention combines the basic principles of bubble dynamics and fluid-induced tube bundle vibration, analyzes the fluid flow conditions near each row of heat exchange tubes, and then analyzes the fluid-induced vibration conditions of each row of heat exchange tubes, and finally proposes a A method for predicting the vibration of tube bundles induced by two-phase flow in the submerged state. By calculating the total time from the bubble generation to the rise of the i-th row of heat exchange tubes in the submerged state, the gas volume, effective liquid volume, and Total gas content, effective gas content, total liquid content, effective liquid content, average density of two-phase flow, cross-flow velocity and critical fluidity of the two-phase flow in the i-th row of heat exchange tubes, and i-th row Periodic vortex amplitude and turbulent buffeting amplitude of the heat exchange tubes, and then determine whether the i-th row of heat exchange tubes will have vibrations induced by periodic vortex shedding, vibrations induced by turbulent buffeting, and elastic vibrations. The prediction method of the present invention can be applied to the tube bundle vibration prediction of equipment such as reboilers, condensers, evaporators, nuclear reactors, etc., which work in the submerged state, and can guide the design of anti-vibration structures, and have a great impact on the design of equipment structures. It has great practical and reference significance for safe operation.

Description of drawings

Fig. 1 is a flow chart of a method for predicting tube bundle vibration induced by two-phase flow in a submerged state according to the present invention.

Fig. 2 is a schematic diagram of the shell-side medium two-phase flow working state.

Fig. 3 is a schematic diagram of the coverage of the i-th row of heat exchange tubes.

Fig. 4 is a schematic diagram of the tube gap of the i-th row of heat exchange tubes.

Fig. 5 is an overall schematic diagram of the steam generator of the first embodiment.

Fig. 6 is a schematic diagram of the pipe layout of the steam generator of the first embodiment.

Fig. 7 is a schematic diagram of arrangement of heat exchange tubes of the steam generator of the first embodiment.

Fig. 8 is a schematic diagram of the first row of heat exchange tubes of the steam generator of the first embodiment.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

As shown in Figure 1, a method for predicting the vibration of a two-phase flow-induced tube bundle in the submerged state of the present invention comprises the following steps:

S1. Calculate the eigenfactors of the vibration of the tube bundle induced by the two-phase flow in the submerged state; among them, the eigenfactors of the vibration induced by the two-phase flow in the i-th row of heat exchange tubes in the submerged state include: the generation of air bubbles in the i-th row of heat exchange tubes in the submerged state The total time to rise t; the gas volume V _gi within the coverage area of the i-th row of heat exchange tubes in the submerged state; the effective liquid volume V _Li within the coverage area of the i-th row of heat exchange tubes in the submerged state; The total gas content ε _gii and the effective gas content ε _gi within the coverage of the heat exchange tubes; the total liquid content ε _Lii and the effective liquid content ε _Li within the coverage of the i-th row of heat exchange tubes in the submerged state; the submerged state The average density ρ _TPi of the two-phase flow within the coverage area of the i-th row of heat exchange tubes; the cross-flow velocity v _TPi of the two-phase flow in the gap between the i-th row of heat exchange tubes in the submerged state; the i-th row of heat exchange tubes in the submerged state critical fluidity v _C in the gap; periodic vortex amplitude y _s and turbulent buffeting amplitude y _t of heat exchange tube i in the submerged state;

Among them, the working state of the two-phase flow of the shell-side medium is shown in Figure 2; the two-phase flow refers to the gas phase and the liquid phase; the shell-side refers to the passage outside the heat exchange tube and the part connected with it; The medium that circulates in the process, such as water, steam, etc.;

S11, the calculation of the total time t from the bubble generation to the rise of the i-th row of heat exchange tubes in the submerged state is as follows:

t=1/f;

In the formula, D _b represents the diameter of the bubble shedding; θ represents the contact angle between the bubble and the wall; σ represents the surface tension of the shell-side liquid; ρ _L represents the liquid density; ρ _g represents the gas density; f represents the frequency; g represents the acceleration of gravity;

S12, the calculation of the gas volume V _gi within the coverage of the i-th row of heat exchange tubes in the submerged state is as follows:

Gas volume flow rate within the coverage area of the first row of heat exchange tubes

Gas volume flow rate within the coverage area of the second row of heat exchange tubes

The gas volume flow rate within the coverage area of the i-th row of heat exchange tubes

The gas volume V _gi =Q _gi t within the coverage of the i-th row of heat exchange tubes;

In the formula, Q _g represents the total volume flow rate of gas; n ₁ represents the number of heat exchange tubes in the first row; n _i represents the number of heat exchange tubes in the i-th row; n represents the total number of heat exchange tubes in the heat exchange equipment, n= n ₁ +n ₂ +n ₃ +…+n _i +…;

Among them, the i-th row of heat exchange tube coverage is shown in Figure 3;

S13, the calculation of the effective liquid volume V _Li within the coverage of the i-th row of heat exchange tubes in the submerged state is as follows:

V _Li =Q _Li t;

Q _Li =Q _gi ρ _g /ρ _L ;

In the formula: Q _Li represents the effective liquid volume flow within the coverage of the i-th row of heat exchange tubes;

S14, the calculation of the total gas content ε _gii and the effective gas content ε _gi within the coverage of the i-th row of heat exchange tubes in the submerged state is as follows:

ε _gi =V _gi /(V _gi +V _Li );

In the formula, V _i represents the shell side volume within the coverage of the i-th row of heat exchange tubes;

S15, the calculation of the total liquid content ε _Lii and the effective liquid content ε _Li within the coverage of the i-th row of heat exchange tubes in the submerged state is as follows:

ε _Li =V _Li /(V _gi +V _Li );

S16, the calculation of the average density _ρTPi of the two-phase flow within the coverage of the i-th row of heat exchange tubes in the submerged state is as follows:

ρ _TPi = ρ _L ε _Li + ρ _g ε _gi ;

S17, the calculation of the two-phase flow cross-flow velocity v _TPi in the i-th row of heat exchange tube gaps in the submerged state is as follows:

In the formula, F _si represents the total cross-sectional area of the i-th row of heat exchange tube shell-side fluid flow; F _si (ε _gii +ε _Lii ) represents the effective cross-sectional area of the i-th row of heat exchange tube two-phase flow;

Among them, the gap between the i-th row of heat exchange tubes is shown in Figure 4;

S18, the calculation of the critical flow rate v _C in the tube gap of the i-th row of heat exchange tubes in the submerged state is as follows:

In the formula, K represents the instability coefficient; a represents the index; d represents the outer diameter of the heat exchange tube; δ ₁ represents the logarithmic decay rate; f ₁ represents the first-order natural frequency of the heat exchange tube; total mass;

S19, the calculation of the periodic vortex amplitude y _s and the turbulent buffeting amplitude y _t of the i-th row of heat exchange tubes in the submerged state is as follows:

In the formula, C _L represents the lift coefficient;

normalized power spectral density

The mass flow rate of the two-phase flow of the i-th row of heat exchange tubes: W _Gi = ρ _TP v _TPi ;

Power spectral density S _F =NPSD(W _Gi d) ² ;

In the formula, C ₁ represents the coefficient, and the value of C ₁ is 0.4213;

S2. According to the characteristic factor of the vibration of the i-th row of heat exchange tubes induced by the two-phase flow in the submerged state, predict whether the i-th row of heat exchange tubes will be damaged by vibration; the types of vibration include: vibration induced by periodic vortex shedding, Vibration and elastic vibration induced by turbulent buffeting;

S21, the judgment about the vibration induced by periodic vortex shedding is as follows:

Determine whether the total gas content of the i-th row of heat exchange tubes is greater than or equal to 15% in the submerged state. If yes, the vibration induced by periodic vortex shedding will not occur; if not, the vibration induced by periodic vortex shedding may occur. Further judgment is made to determine whether the periodic vortex amplitude of the i-th row of heat exchange tubes in the submerged state is less than or equal to 0.02 times the outer diameter of the heat exchange tubes. If yes, the vibration induced by periodic vortex shedding will not occur; if not, it will Periodic vortex shedding-induced vibration occurs;

S22, the judgment on the vibration induced by turbulent buffeting is as follows:

Determine whether the turbulent buffeting amplitude of the i-th row of heat exchange tubes in the submerged state is less than or equal to 0.02 times the outer diameter of the heat exchange tubes, if yes, no vibration induced by turbulent buffeting will occur; if not, turbulent buffeting will occur vibration;

S23, the judgment on elastic vibration is as follows:

Determine whether the cross-flow velocity of the two-phase flow in the tube gap of the i-th row of heat exchange tubes in the submerged state is less than or equal to the critical flow velocity, if yes, elastic vibration will not occur; if not, elastic vibration will occur;

Embodiment one,

The steam generator in a certain device is shown in Figure 5, the pipe layout and heat exchange tube arrangement are shown in Figure 6 and Figure 7, and the operating conditions of the tube side and shell side are shown in Table 1 below. Under the operating conditions of the evaporator, due to the vibration induced by the two-phase flow tube bundle, leakage occurs at the connection between the heat exchange tube and the tube sheet, and three heat exchange tubes are blocked in the first row, as shown in Figure 8.

Table 1 Operating Conditions

Taking the first row of heat exchange tubes as an example, according to a method for predicting the vibration of the tube bundle induced by two-phase flow in the submerged state of the present invention, analyzing the vibration of the tube bundle induced by the two-phase flow includes the following steps:

S1, calculating the characteristic factor of the vibration of the first row of heat exchange tubes induced by the two-phase flow in the submerged state;

S11, calculate the total time t from bubble generation to rising of the first row of heat exchange tubes in the submerged state:

t=1/f;

In the formula, θ＝48°; σ＝0.02618N/m; ρ _L ＝798.37kg/m ³ ; ρ _g ＝19.33kg/m ³ ; g＝9.8m/s ² ;

Calculated, t=0.0245s;

S12, calculate the gas volume V _g1 within the coverage of the first row of heat exchange tubes in the submerged state:

Gas volume flow rate within the coverage area of the first row of heat exchange tubes

The gas volume V _g1 = Q _g1 t within the coverage area of the first row of heat exchange tubes;

In the formula, Q _g =1862.39m ³ /h; n ₁ =6; this embodiment is a U-shaped tube, n=1510;

Calculated, V _g1 =5.04×10 ^-5 m ³ ;

S13, calculate the effective liquid volume V _L1 within the coverage of the first row of heat exchange tubes in the submerged state:

V _L1 =Q _L1 t;

Q _L1 = Q _g1 ρ _g /ρ _L ;

Calculated, V _L1 = 1.221×10 ^-6 m ³ ;

S14, respectively calculate the total gas content ε _g11 and the effective gas content ε _g1 within the coverage of the first row of heat exchange tubes in the submerged state:

ε _g1 =V _g1 /(V _g1 +V _L1 );

In the formula, V ₁ =0.0594m ³ ;

Calculated, ε _g11 = 0.08%; ε _g1 = 97.6%;

S15, respectively calculate the total liquid content ε _L11 and the effective liquid content ε _L1 within the coverage of the first row of heat exchange tubes in the submerged state:

ε _L1 =V _L1 /(V _g1 +V _L1 );

Calculated, ε _L11 = 0.0021%; ε _L1 = 2.4%;

S16, calculate the average density ρ _TP1 of the two-phase flow within the coverage of the first row of heat exchange tubes in the submerged state:

ρ _TP1 = ρ _L ε _L1 + ρ _g ε _g1 ;

Calculated, ρ _TP1 = 37.74kg/m ³ ;

S17, calculate the two-phase flow cross-flow velocity v _TP1 in the gap between the first row of heat exchange tubes in the submerged state:

In the formula, F _s1 = 2.56m ² ; F _s1 (ε _g11 +ε _L11 ) = 0.0022m ² ;

Calculated, v _TP1 =0.95m ² /s;

S18. Calculate the critical fluidity v _C in the gap between the first row of heat exchange tubes in the submerged state:

In the formula, K=3.2; a=0.5; d=25mm; δ ₁ =0.036; f ₁ =10.56Hz; m=1.18kg/m;

Calculate v _C =1.14m/s;

S19, calculate the periodic vortex amplitude y _s and turbulent buffeting amplitude y _t of the first row of heat exchange tubes in the submerged state:

In the formula, C _L =0.07;

Calculated, y _s =0.62mm;

normalized power spectral density

The mass flow rate of the two-phase flow of the first row of heat exchange tubes: W _Gi = ρ _TP v _TPi ;

Power spectral density S _F =NPSD(W _Gi d) ² ;

In the formula, C ₁ =0.4213;

Calculated, y _t = 0.028mm;

S2. According to the characteristic factors of the vibration of the first row of heat exchange tubes induced by the two-phase flow in the submerged state, predict whether the first row of heat exchange tubes will undergo periodic vortex shedding-induced vibration, turbulent buffeting-induced vibration, and elastic vibration ;

S21, judging whether the vibration induced by periodic vortex shedding will occur in the first row of heat exchange tubes:

Determine whether the total gas content of the first row of heat exchange tubes in the submerged state is greater than or equal to 15%. If yes, the vibration induced by periodic vortex shedding will not occur; if not, the vibration induced by periodic vortex shedding may occur. Further judgment is made to determine whether the periodic vortex amplitude of the first row of heat exchange tubes in the submerged state is less than or equal to 0.02 times the outer diameter of the heat exchange tubes. If yes, the vibration induced by periodic vortex shedding will not occur; if not, it will Periodic vortex shedding-induced vibration occurs;

Since the total gas content of the first row of heat exchange tubes in the submerged state is ε _g11 = 0.08%, and ε _g11 <15%, vibrations induced by periodic vortex shedding may occur in the first row of heat exchange tubes, and further judgment is required;

Since the periodic vortex amplitude y s of the first row of heat exchange tubes in the submerged state is y _s =0.62mm, y _s >0.02d, that is, y _s >0.5mm, it is judged that the first row of heat exchange tubes will be induced by periodic vortex shedding vibration;

S22, judging whether the vibration induced by turbulent buffeting will occur in the first row of heat exchange tubes:

Determine whether the turbulent buffeting amplitude of the first row of heat exchange tubes in the submerged state is less than or equal to 0.02 times the outer diameter of the heat exchange tubes, if yes, the vibration induced by turbulent buffeting will not occur; if not, the vibration induced by turbulent buffeting will occur vibration;

Since the turbulent buffeting amplitude of the first row of heat exchange tubes in the submerged state is y _t = 0.028mm, y _t <0.02d, that is, y _t <0.5mm, it is judged that the first row of heat exchange tubes will not be induced by turbulent buffeting vibration;

S23, judging whether the first row of heat exchange tubes will undergo elastic vibration:

Determine whether the cross-flow velocity of the two-phase flow in the tube gap of the first row of heat exchange tubes in the submerged state is less than or equal to the critical flow velocity, if yes, elastic vibration will not occur; if not, elastic vibration will occur;

Due to the two-phase flow cross-flow velocity v _TP1 =0.95m ² /s in the tube gap of the first row of heat exchange tubes in the submerged state, the critical fluidity v C in the tube gap of the first row of heat exchange tubes in the submerged state v _C =1.14m /s, v _TP1 <v _C , so it is judged that the first row of heat exchange tubes will not vibrate elastically in the submerged state.

According to the above analysis, since the vibration induced by periodic vortex shedding occurs in the first row of heat exchange tubes, there is leakage between the first row of heat exchange tubes and the tube sheet, which is consistent with the actual situation.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the present invention. within the scope of protection.

Claims (1)

1. A prediction method of two-phase flow induced tube bundle vibration in a submerged state is characterized by comprising the following steps:

s1, calculating a characteristic factor of vibration of a two-phase flow induction tube bundle, namely an ith row of heat exchange tubes in an immersed state, and specifically comprising the following steps:

s11, the total time t from generation to rising of bubbles of the ith row of heat exchange tubes is calculated as follows:

t＝1/f；

in the formula, D _b Represents the bubble shedding diameter; θ represents a contact angle of the bubble with the wall surface; σ represents the surface tension of the shell-side liquid; rho _L Represents the liquid density; rho _g Represents the gas density; f represents a frequency; g represents the gravitational acceleration;

s12, gas volume V in the coverage range of the ith row of heat exchange tubes in the immersed state _gi The calculation is as follows:

gas volume flow within the coverage of the No. 1 heat exchange tube

Gas volume flow in the coverage range of the No. 2 heat exchange tube

Gas volume flow in the coverage range of the ith row of heat exchange tubes

Gas volume V within the coverage range of the ith row of heat exchange tubes _gi ＝Q _gi t；

In the formula, Q _g Represents the total gas volume flow; n is ₁ The number of the heat exchange tubes in the 1 st row is shown; n is _i The number of the ith row of heat exchange tubes is represented; n represents the total number of heat exchange tubes in the heat exchange equipment, and n = n ₁ +n ₂ +n ₃ +…+n _i +…；

S13, effective liquid volume V in the coverage range of the ith row of heat exchange tubes in the immersed state _Li The calculation is as follows:

V _Li ＝Q _Li t；

Q _Li ＝Q _gi ρ _g /ρ _L ；

in the formula: q _Li The effective liquid volume flow in the coverage range of the ith row of heat exchange tubes is represented;

s14, total gas content epsilon in the coverage range of the ith row of heat exchange tubes in the immersed state _gii And effective gas fraction epsilon _gi The calculation is as follows:

ε _gi ＝V _gi /(V _gi +V _Li )；

in the formula, V _i Showing the shell side volume in the coverage range of the ith row of heat exchange tubes;

s15, total liquid content rate epsilon in the coverage range of the ith row of heat exchange tubes in the immersed state _Lii And effective liquid content ε _Li The calculation is as follows:

ε _Li ＝V _Li /(V _gi +V _Li )；

s16, average density rho of two-phase flow in the coverage range of the ith row of heat exchange tubes in the immersed state _TPi The calculation is as follows:

ρ _TPi ＝ρ _L ε _Li +ρ _g ε _gi ；

s17, two-phase flow cross flow velocity v in the clearance of the ith row of heat exchange tubes in the immersed state _TPi The calculation is as follows:

in the formula, F _si Representing the total cross section area of the shell pass fluid flow of the ith row of heat exchange tubes; f _si (ε _gii +ε _Lii ) The effective cross section area of the two-phase flow circulation of the ith row of heat exchange tubes is shown;

s18, critical fluidity v in the clearance of the ith row of heat exchange tubes in the immersed state _C The calculation is as follows:

wherein K represents an instability coefficient; a represents an index; d represents the outer diameter of the heat exchange tube; delta. For the preparation of a coating ₁ Represents a logarithmic decay rate; f. of ₁ Representing a first-order natural frequency of the heat exchange tube; m represents the total mass of the heat exchange tube per unit length;

s19, periodic vortex amplitude y of the ith row of heat exchange tubes in the immersed state _s And turbulence buffeting amplitude y _t The calculation is as follows:

in the formula, C _L Represents a lift coefficient;

normalized power spectral density

Mass flow rate of two-phase flow of the ith row of heat exchange tubes: w is a group of _Gi ＝ρ _TPi v _TPi ；

Power spectral density S _F ＝NPSD(W _Gi d) ² ；

In the formula, C ₁ Represents coefficient, C ₁ Is 0.4213;

s2, judging whether the ith row of heat exchange tubes can be damaged by vibration or not according to the characteristic factor of the two-phase flow induced vibration of the ith row of heat exchange tubes in the immersed state; wherein the categories of vibration include: vibration induced by periodic vortex shedding, vibration induced by turbulent buffeting, and elastic vibration;

in step S2, it is determined whether the i-th row of heat exchange tubes will generate vibration induced by periodic vortex shedding, vibration induced by turbulent buffeting, and elastic vibration, specifically as follows:

s21, the judgment of the vibration induced by the periodic vortex shedding is as follows:

judging the total gas content epsilon of the ith row of heat exchange tubes in the immersed state _gii Whether the vortex shedding is larger than or equal to 15 percent or not, if so, the vibration induced by the periodic vortex shedding is avoided; if not, the vibration induced by the periodic vortex shedding is possible to occur, further judgment is needed, and the periodic vortex amplitude y of the ith row of heat exchange tubes in the immersed state is judged _s Whether the outer diameter of the heat exchange tube is less than or equal to 0.02 time, if so, vibration induced by periodic vortex shedding cannot occur, and if not, vibration induced by periodic vortex shedding can occur;

s22, the judgment of the vibration induced by the turbulent buffeting is as follows:

judging turbulence buffeting amplitude y of the ith row of heat exchange tubes in the immersed state _t Whether or not less thanThe external diameter d of the heat exchange tube is equal to 0.02 time, and if the external diameter d of the heat exchange tube is equal to 0.02 time, turbulence buffeting induced vibration cannot occur; if not, vibration induced by turbulence buffeting can occur;

s23, the determination of the elastic vibration is as follows:

judging the two-phase flow cross flow velocity v in the tube clearance of the ith row of heat exchange tubes in the immersed state _TPi Whether or not the critical flow velocity v is less than or equal to _C If so, elastic vibration cannot occur; if not, elastic vibration occurs.

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