CN103971010A - Method for judging thermal stratification phenomenon of lead and bismuth fluid - Google Patents

Abstract

The invention discloses a method for judging the thermal stratification phenomenon of lead and bismuth fluid. The method includes the steps that firstly, a temperature measuring element is installed in a lead and bismuth pipeline, the temperature of the cold side fluid and the temperature of the hot side fluid are measured respectively through the temperature measuring element, and the temperature T1 of the cold side fluid and the temperature T2 of the cold side fluid are obtained respectively; secondly, a formula, T1 and T2 are fitted according to the density of the lead and bismuth fluid, and the density rho 1 and the density rho 2 of the lead and bismuth fluid under the temperature T1 and the temperature T2 are obtained; thirdly, fitting is conducted on an existing buoyancy formula, an inertia force formula and a cubic expansion coefficient formula, and a non-dimensional criterion numeral formula is obtained; fourthly, rho 1 and rho 2 are substituted into the non-dimensional criterion numeral formula, and a non-dimensional criterion numeral is calculated; fifthly, when the non-dimensional criterion numeral is smaller than 1, the thermal stratification phenomenon of the lead and bismuth fluid does not exist, when the non-dimensional criterion numeral is equal to 1, the thermal stratification phenomenon of the lead and bismuth fluid begins to happen, when the non-dimensional criterion numeral is larger than 1, the thermal stratification phenomenon of the lead and bismuth fluid exists, and as the non-dimensional criterion numeral increases, the thermal stratification phenomenon becomes more stable.

Description

A kind of method of judging plumbous bismuth fluid generation thermal stratification

Technical field

The invention belongs to nuclear safety and thermal-hydraulic and calculate field, be specifically related to plumbous bismuth fluid thermal lamination algorithm.

Background technology

The sub-critical reactor (ADS) of Accelerator driven is one of the most promising separation-transmuting technology, desirable long-lived radioactivity waste incinerator.The fusing point of lead bismuth alloy (LBE) is low, boiling point is high, has good neutronics performance, heat transfer property, contacts vigorous reaction etc. does not occur with water, has become in current ADS design the spallation target preferred material of cooling medium of holding concurrently.ADS is mainly made up of high current proton precessional magnetometer, external source Neutron generator, subcritical reactor and electric power output system.Design and the experimental study of plumbous bismuth experimental loop, lead bismuth alloy physicochemical property and hot-working hydraulic characteristic research, significant to ensureing the safe operation of whole ADS system.

But the difference of the fluid density that plumbous bismuth loop causes due to the difference of temperature on gravity direction causes cold fluid in below, hot fluid is called thermal stratification in the phenomenon of top.Thermal stratification is the main cause that causes heat fatigue, and plumbous bismuth thermal stratification produces material impact to ADS system thermal-hydraulic, follows the research and development of advanced heap of the 4th generation, and thermally stratified layer Study on Problems should be subject to enough attention.Localized heat stress produces cyclical variation meeting and causes heat fatigue damage etc. will have a strong impact on reactor safety.In nuclear energy field, open heap and shutdown at every turn, the heat fatigue phenomenon of equipment pipe all can directly have influence on the security of reactor.T.muramatsu points out, after fast reactor shutdown, in upper chamber, can produce thermal stratification, and reactor vessel and easy internals are caused to huge thermal stress.In order to prevent this phenomenon, countries in the world nuclear power station has all been taked corresponding measure, as the Japanese upper limit that has specified thermal stress according to " electric enterprise method ".The research of the thermal stratification thermally stratified layer to plumbous bismuth and heat fatigue phenomenon is both at home and abroad still in the starting stage, but the thermal stratification of water has been had to more research, wherein in the majority with Japan, France, the U.S. abroad.In Japan, the example that four respectful orders difficult to understand occur according to nuclear power station, when reason to temperature variation and fault occur, the state of equipment and the feature of example are adjusted, and have been divided into 7 kinds of forms and have answered one by one, and wherein form 1,3,4,5 is all thermal stratification.Form 1 is the inflow of main pipeline to branch pipe(tube), and the hot fluid of main pipeline can produce certain penetration to the cold water in arm, and at bottom generation thermal stratification.Form 3 is that high-temperature water mixes with water at low temperature, can produce a layer segregation phenomenon.The sealing infiltration of form 4 valves causes the infiltration of fluid, causes thermal stratification.When form 5 exists temperature difference valve to reveal for isolation, the leakage of valve seat causes thermal stratification; The expert of Japan PNC has also developed a kind of program AQUA, simulates and assess thermal stratification and the impact on structure.In France, French H.ohshima is by 4 kinds of problems of temperature fluctuation phenomenon collective analysis in metal fast breeder reactor: thermally stratified layer, heat fatigue, the rocking of the coupling of reactor core-cavity and free surface; Nubuo.nakamori has built test-bed, and the thermal stratification of the safety injection system straight tube to nuclear power plant is studied.American D.tenchine is studied the heat fatigue at some position of sodium-cooled fast reactor.At home, Chen Licheng, Lu Donghua has done flow field simulation to the thermally stratified layer of water, has improved traditional modeling method.But also there is following problem for the judgement of thermal stratification:

The first, at present the research of the thermal stratification to plumbous bismuth fluid is still in the junior stage both at home and abroad, for example: P.agostini etc. test the plumbous bismuth Natural Circulation of one dimension.Sehgal etc. have carried out the thermal-hydraulic experiment of plumbous bismuth for TALL experimental loop.W.Ambrosini etc. have carried out the experiment that argon gas injects the plumbous bismuth flow of impact in PIZZA loop.The Natural Circulation stable state of the counterweight metallic(return) circuits such as Weimin Ma is studied.The domestic KYLIN-I of utilization such as Wu Yican has carried out in loop " the corrosion military service performance that Accelerator Driven Subcritical heap (ADS) structured material (316L, TP91, CLAM steel etc.) flows in plumbous bismuth in liquid state " experimental study first, for ADS material military service performance study provides reliable experimental data.G.Coccoluto etc. to NAICE loop adopt experimental study injection argon gas strengthen plumbous bismuth natural circulation flow.A.V.Besnosov etc. have carried out experimental study in velocity field and the temperature field to the lead under high temperature and plumbous bismuth fluid, and experimental section is annular and circular;

The second, in prior art, the judgement of thermal stratification is only relied on and utilizes the empirical value of the cubic expansion coefficient to judge, but traditional determination methods need to be measured the volume of plumbous bismuth fluid, the volume of the plumbous bismuth fluid in circulation is to be difficult for measuring, and has increased the difficulty of measuring;

Due to the existence of the problems referred to above, the inventor studies and improves prior art, to can work out quick, efficient, convenient and not rely on a kind of method of judging plumbous bismuth fluid generation thermal stratification that the empirical value of traditional cubic expansion coefficient calculates.

Summary of the invention

In order to address the above problem, the inventor has carried out research with keen determination, found that: the plumbous bismuth fluid density to the matching of Chinese scholars institute has been carried out matching again, has reduced the error of plumbous bismuth fluid in a certain temperature lower density.By looking into the mode of figure, obtain the density of plumbous bismuth fluid at this temperature, recycling calculation procedure directly judges whether plumbous bismuth fluid thermal stratification occurs, simplify calculating, also can not utilize the empirical value of the cubic expansion coefficient, obtain the exact value of the cubic expansion coefficient, increase the precision of whole calculating.Thereby complete the present invention.

The object of the present invention is to provide following aspect:

First aspect, a kind of method of judging plumbous bismuth fluid generation thermal stratification, is characterized in that: the method comprises the following steps:

(1) in plumbous bismuth pipeline, temperature element is installed, by temperature element, the temperature of cold-side fluid and hot side liquid is measured respectively, obtain respectively the temperature T of cold-side fluid ₁temperature T with hot side liquid ₂,

(2) according to plumbous bismuth fluid density fitting formula and T ₁and T ₂, draw respectively at T ₁and T ₂the corresponding cold-side fluid density p of plumbous bismuth fluid at temperature ₁with hot side liquid density p ₂; Wherein, described plumbous bismuth fluid density fitting formula is as follows:

ρ _LBE＝11113.6-1.34·T

Wherein, T is temperature, and its unit is K, ρ _lBEfor plumbous bismuth fluid density, its unit is kg/m ³;

(3) buoyancy lift formula, inertial force formula and cubic expansion coefficient formula are carried out to matching, obtain dimensionless criterion numeral formula, described dimensionless criterion numeral formula is

Wherein, R _ifor dimensionless criterion numeral, g is acceleration of gravity, the m/s of unit ²; L is internal diameter of the pipeline, the m of unit; ρ ₁for cold-side fluid density, ρ ₂for hot side liquid density, unit is kg/m ³; U is fluid velocity, the m/s of unit;

(4) by above-mentioned ρ ₁, ρ ₂bring dimensionless criterion numeral formula into, calculate dimensionless criterion numeral;

(5) according to dimensionless criterion numeral, the thermal stratification of plumbous bismuth fluid is judged, as dimensionless criterion numeral < 1, plumbous bismuth fluid thermal lamination does not exist, in the time of dimensionless criterion numeral=1, plumbous bismuth fluid starts to occur thermal stratification, and in the time of dimensionless criterion numeral > 1, plumbous bismuth fluid has thermal stratification, along with the increase of dimensionless criterion numeral, it is more obvious that thermal stratification becomes.

Second aspect, a kind of method of judging plumbous bismuth fluid generation thermal stratification as described in above-mentioned first aspect, is characterized in that:

In step (2), draw the density map that obtains plumbous bismuth fluid according to plumbous bismuth fluid density fitting formula, and according to this figure and T ₁and T ₂, draw respectively T ₁and T ₂the density p of plumbous bismuth fluid at temperature ₁and ρ ₂.

The third aspect, a kind of method of judging plumbous bismuth fluid generation thermal stratification as described in above-mentioned first aspect, is characterized in that: the temperature element in step (1) is thermopair.

Fourth aspect, a kind of method of judging plumbous bismuth fluid generation thermal stratification as described in above-mentioned first aspect, is characterized in that: in step (3), carry out matching obtain R by buoyancy lift formula and inertial force formula _icomposite formula, R _icomposite formula carries out matching with cubic expansion coefficient formula again, obtains above-mentioned dimensionless criterion numeral formula.

The 5th aspect, a kind of method of judging plumbous bismuth fluid generation thermal stratification as described in above-mentioned fourth aspect, is characterized in that: described buoyancy lift formula is

$\mathrm{Gr}=\frac{{\mathrm{g\&alpha;}}_V\mathrm{\&Delta;}{\mathrm{tl}}^3}{{\mathrm{\&nu;}}^2}$

Wherein, Gr is buoyancy lift, and g is acceleration of gravity, the m/s of unit ², α _vthat volume is the cubic expansion coefficient of the plumbous bismuth fluid of V, the 1/K of unit, Δ t is the temperature difference of cold fluid and hot fluid, unit K, Δ t=t ₂-t ₁; L is internal diameter of the pipeline, the m of unit, and ν refers to density viscosity, is defined as η represents fluid viscosity, and unit is pa.s, and ρ represents fluid density, and unit is kgm ³.

The 6th aspect, a kind of method of judging plumbous bismuth fluid generation thermal stratification as described in above-mentioned fourth aspect, is characterized in that: described inertial force formula is

$\mathrm{Re}=\frac{\mathrm{ul}}{\mathrm{\&nu;}}$

Wherein, Re is fluid inertia force, and l is internal diameter of the pipeline, the m of unit, and u is fluid velocity, the m/s of unit, ν refers to density viscosity, is defined as η represents fluid viscosity, and unit is pa.s, and ρ represents fluid density, and unit is kgm ³.

The 7th aspect, a kind of method of judging plumbous bismuth fluid generation thermal stratification as described in above-mentioned fourth aspect, is characterized in that: described cubic expansion coefficient formula is

$\&PartialD;=\frac{V_{t_2}-V_{t_1}}{V_{t_1}(t_2-t_1)}$

Wherein, volume expansivity, that unit fluid is at t ₁dEG C time volume, that unit fluid is at t ₂dEG C time volume, wherein with unit be m ³, t ₁and t ₂unit be DEG C.

According to a kind of method of judging plumbous bismuth fluid generation thermal stratification provided by the invention, it has following beneficial effect:

The first, in the case of the empirical value that is unfavorable for the cubic expansion coefficient, the thermal stratification of plumbous bismuth fluid is judged, make this deterministic process easy, quick, and then improved whole work efficiency;

The second, the method is carried out matching to research formula both domestic and external, and the judgement precision of plumbous bismuth fluid generation thermal stratification is improved.

Brief description of the drawings

Fig. 1 illustrates a kind of according to the preferred embodiment of the present invention density map of plumbous bismuth fluid of the method for judging plumbous bismuth fluid generation thermal stratification;

Fig. 2 illustrates a kind of according to the preferred embodiment of the present invention plumbous bismuth fluid density fitting formula and deterministic process figure of the method for judging plumbous bismuth fluid generation thermal stratification.

Embodiment

Below by the present invention is described in detail, the features and advantages of the invention will become more clear, clear and definite along with these explanations.

Here special word " exemplary " means " as example, embodiment or illustrative ".Here needn't be interpreted as being better than or being better than other embodiment as " exemplary " illustrated any embodiment.Although the various aspects of embodiment shown in the drawings, unless otherwise indicated, needn't draw accompanying drawing in proportion.

According in a preferred embodiment of the present invention, as shown in Fig. 1-2, provide a kind of method of judging plumbous bismuth fluid generation thermal stratification, it is characterized in that: the method comprises the following steps:

(1) in plumbous bismuth pipeline, temperature element is installed, by temperature element, the temperature respectively of cold-side fluid and hot side liquid is measured, and measurement thermal signal is converted into electric signal, obtain respectively the temperature T of cold-side fluid ₁temperature T with hot side liquid ₂;

(2) be the density map that plumbous bismuth fluid density fitting formula is drawn plumbous bismuth fluid according to LEB density fitting formula, i.e. Fig. 1, and according to this figure and T ₁and T ₂, obtain respectively T ₁and T ₂the corresponding cold-side fluid density p of plumbous bismuth fluid at temperature ₁with hot side liquid density p ₂, described plumbous bismuth fluid density fitting formula is as follows:

ρ _LBE＝11113.6-1.34·T

Wherein, T is the time, and its unit is K, ρ _lBEfor plumbous bismuth fluid density, its unit is kg/m ³;

(3) existing buoyancy lift formula, inertial force formula and cubic expansion coefficient formula are carried out to matching, obtain dimensionless criterion numeral formula, be specially the fitting formula of Richardson number; The fitting formula of described dimensionless criterion numeral formula or Richardson number is

$R_i=\frac{\mathrm{gl}(\frac{{\mathrm{\&rho;}}_1}{{\mathrm{\&rho;}}_2}-1)}{u^2};$

Wherein, R _ifor dimensionless criterion numeral, g is acceleration of gravity, the m/s of unit ²; L is internal diameter of the pipeline, the m of unit; ρ ₁for cold-side fluid density, ρ ₂for hot side liquid density, unit is kg/m ³; U is fluid velocity, the m/s of unit;

(4) by above-mentioned ρ ₁, ρ ₂being brought into dimensionless criterion numeral formula is in the fitting formula of Richardson number, calculates dimensionless criterion numeral R _iconcrete numerical value.

(5) according to R _inumerical value the thermal stratification of plumbous bismuth fluid is judged, as dimensionless criterion numeral < 1, plumbous bismuth fluid thermal lamination does not exist, in the time of dimensionless criterion numeral=1, plumbous bismuth fluid starts to occur thermal stratification, and in the time of dimensionless criterion numeral > 1, plumbous bismuth fluid has thermal stratification, along with the increase of dimensionless criterion numeral, it is more obvious that thermal stratification becomes.The method does not need to calculate the empirical value of the cubic expansion coefficient, makes the judgement of the thermal stratification to plumbous bismuth fluid more convenient, has improved the efficiency of measuring, and is conveniently generalized to other liquid.

One preferred embodiment in, plumbous bismuth pipeline described in step (1) can be conventional Natural Circulation pipeline, described temperature element is thermopair.

One preferred embodiment in, described in step (2), LEB refers to plumbous bismuth fluid, LEB density is plumbous bismuth fluid density, LBE density fitting formula obtains by matching, concrete fit procedure comprises:

The temperature variant computing formula of LBE density is:

ρ _LBE＝11096-1.3236·T

The scholars' such as employing Lyon, Kutateladze, Kirillov experimental data, utilizes the principle of least square to carry out matching, obtains LBE density fitting formula and is:

ρ _LBE＝11113.6-1.34·T

The drawing process of concrete matching and Fig. 1 can list of references: perillaseed prestige, liquid lead bismuth alloy study on thermal property, nuclear technology, 2013,9:36 (9).

Draw the density map of plumbous bismuth fluid according to LBE density fitting formula, can draw this figure by conventional drawing practice, the density map difference of different liquids, needs to draw according to corresponding density fitting formula.

One preferred embodiment in, in step (2), pass through temperature T ₁and T ₂obtain respectively T ₁and T ₂the density p of plumbous bismuth fluid at temperature ₁and ρ ₂, i.e. plumbous bismuth fluid T ₁density p at temperature ₁with plumbous bismuth fluid T ₂density p at temperature ₂, and then make the method in the case of not by measuring the thermal stratification that also can judge plumbous bismuth fluid the volume of plumbous bismuth fluid, make deterministic process succinct.

One preferred embodiment in, the fitting formula of Richardson number is to carry out matching by existing buoyancy lift formula, inertial force formula and cubic expansion coefficient formula to form in step (3),

Wherein, no matter material is the variation of which kind of (solid, liquid or gas) form, is all referred to as measure expansion or volumetric expansion.In the time that object temperature changes 1 degree Celsius, the ratio of the variation of its volume and its volume in the time of 0 DEG C, is called " volume expansivity " or " coefficient of volumetric expansion ", passes through symbol represent.While being located at 0 DEG C, the volume of material is V ₀, the volume in the time of t DEG C is V _t, the definition of the cubic expansion coefficient is:

$\&PartialD;=\frac{V_t-V_0}{V_{0}t}$

Because the expansion coefficient of solid or liquid is very little, be convenience of calculation, for temperature from t ₁become t ₂fluid, the volume V when asking again 0 DEG C ₀, directly replace V with the volume under lower temperature ₀volume calculates, can directly calculate with following formula,

$\&PartialD;=\frac{V_{t_2}-V_{t_1}}{V_{t_1}(t_2-t_1)}$

In formula that unit fluid is at t ₁dEG C time volume, that unit fluid is at t ₂dEG C time volume, wherein with unit be m ³, t ₁and t ₂unit be DEG C that this formula is only applicable to solid or liquid, because the expansion coefficient value of gaseous matter is larger, can not use this formula.

For plumbous bismuth fluid thermal lamination, buoyancy lift and inertial force are of paramount importance influence factors.Buoyancy lift is larger or inertial force is less, and thermal stratification just more easily occurs.The Richardson number that the present invention proposes is the dimensionless criterion numeral of buoyancy lift and inertial force ratio, is an important motivity index that judges thermally stratified layer, and wherein, buoyancy lift formula is as follows:

$\mathrm{Gr}=\frac{{\mathrm{g\&alpha;}}_V\mathrm{\&Delta;}{\mathrm{tl}}^3}{{\mathrm{\&nu;}}^2}$

Inertial force formula is as follows:

$\mathrm{Re}=\frac{\mathrm{ul}}{\mathrm{\&nu;}}$

Wherein, Gr is buoyancy lift; Re is fluid inertia force; G is acceleration of gravity, the m/s of unit ²; α _vthat volume is the cubic expansion coefficient of plumbous bismuth fluid of V and above-mentioned the implication of representative is identical, the 1/K of unit; Δ t is the temperature difference of cold fluid and hot fluid, unit K, Δ t=t ₂-t ₁; L is internal diameter of the pipeline, the m of unit; U is fluid velocity, the m/s of unit, and ν refers to density viscosity, is defined as η represents fluid viscosity, and unit is pa.s, and ρ represents fluid density, and unit is kgm ³.In the present invention, by buoyancy lift formula and inertial force formula, obtain R _icomposite formula, this process is as follows:

$\mathrm{Ri}=\frac{\mathrm{Gr}}{{\mathrm{Re}}^2}=\frac{{\mathrm{g\&alpha;}}_v\mathrm{\&Delta;tl}}{u^2}$

R _icomposite formula carries out matching with cubic expansion coefficient formula again, and its fit procedure is: will be brought into R _iin composite formula, can obtain the final expression formula of Richardson number (Ri), i.e. dimensionless criterion numeral formula, this process is as follows:

$R_i=\frac{\mathrm{gl}\left(\frac{V_{t_2}-V_{t_1}}{V_{t_1}}\right)}{u^2}=\frac{\mathrm{gl}(\frac{{\mathrm{\&rho;}}_1}{{\mathrm{\&rho;}}_2}-1)}{u^2}$

Wherein g is acceleration of gravity, the m/s of unit ²; L is internal diameter of the pipeline, the m of unit; ρ ₁for cold-side fluid density, ρ ₂for hot side liquid density, unit is kg/m ³; U is fluid velocity, the m/s of unit;

By ρ ₁and ρ ₂be brought in above-mentioned formula, try to achieve dimensionless criterion numeral, the judgement of recycling dimensionless criterion numeral has or not lamination.

According to a kind of method of judging plumbous bismuth fluid generation thermal stratification provided by the invention, it has following beneficial effect:

The first, obtain in situation the thermal stratification of plumbous bismuth fluid is judged at the empirical value that is unfavorable for the cubic expansion coefficient, this deterministic process that is is easy, quick, and then has improved whole work efficiency;

The second, the method is carried out matching to research formula both domestic and external, and the judgement precision of plumbous bismuth fluid generation thermal stratification is improved.

Describe the present invention in conjunction with specific embodiments above.But, these embodiments are only illustrative, and it is to protection scope of the present invention and do not constitute any limitation.It will be appreciated by those skilled in the art that, in the situation that not exceeding or departing from protection domain of the present invention, technical solutions and their implementation methods of the present invention have multiple modification, improvement or equivalent, these all should fall within the scope of protection of the present invention.

Claims (7)

1. a method of judging plumbous bismuth fluid generation thermal stratification, is characterized in that: the method comprises the following steps:

(1) in plumbous bismuth pipeline, temperature element is installed, by temperature element, the temperature of cold-side fluid and hot side liquid is measured respectively, obtain respectively the temperature T of cold-side fluid ₁temperature T with hot side liquid ₂,

(2) according to plumbous bismuth fluid density fitting formula and T ₁and T ₂, draw respectively at T ₁and T ₂the corresponding cold-side fluid density p of plumbous bismuth fluid at temperature ₁with hot side liquid density p ₂, wherein said plumbous bismuth fluid density fitting formula is as follows:

ρ _LBE＝11113.6-1.34·T

Wherein, T is temperature, and its unit is K, ρ _lBEfor plumbous bismuth fluid density, its unit is kg/m ³;

(3) buoyancy lift formula, inertial force formula and cubic expansion coefficient formula are carried out to matching, obtain dimensionless criterion numeral formula, described dimensionless criterion numeral formula is

Wherein, R _ifor dimensionless criterion numeral, g is acceleration of gravity, the m/s of unit ²; L is internal diameter of the pipeline, the m of unit; ρ ₁for cold-side fluid density, ρ ₂for hot side liquid density, unit is kg/m ³; U is fluid velocity, the m/s of unit;

(4) by above-mentioned ρ ₁, ρ ₂bring dimensionless criterion numeral formula into, calculate dimensionless criterion numeral;

(5) according to dimensionless criterion numeral, the thermal stratification of plumbous bismuth fluid is judged, as dimensionless criterion numeral < 1, plumbous bismuth fluid thermal lamination does not exist, in the time of dimensionless criterion numeral=1, plumbous bismuth fluid starts to occur thermal stratification, and in the time of dimensionless criterion numeral > 1, plumbous bismuth fluid has thermal stratification, along with the increase of dimensionless criterion numeral, it is more obvious that thermal stratification becomes.

2. a kind of method of judging plumbous bismuth fluid generation thermal stratification as claimed in claim 1, is characterized in that:

In step (2), draw the density map that obtains plumbous bismuth fluid according to plumbous bismuth fluid density fitting formula, and according to this figure and T ₁and T ₂, draw respectively at T ₁and T ₂the density p of plumbous bismuth fluid at temperature ₁and ρ ₂.

3. a kind of method of judging plumbous bismuth fluid generation thermal stratification as claimed in claim 1, is characterized in that: the temperature element in step (1) is thermopair.

4. a kind of method of judging plumbous bismuth fluid generation thermal stratification as claimed in claim 1, is characterized in that: in step (3), carry out matching obtain R by buoyancy lift formula and inertial force formula _icomposite formula, R _icomposite formula carries out matching with cubic expansion coefficient formula again, obtains above-mentioned dimensionless criterion numeral formula.

5. a kind of method of judging plumbous bismuth fluid generation thermal stratification as claimed in claim 4, is characterized in that: described buoyancy lift formula is

$\mathrm{Gr}=\frac{{\mathrm{g\&alpha;}}_V\mathrm{\&Delta;}{\mathrm{tl}}^3}{{\mathrm{\&nu;}}^2}$

Wherein, Gr is buoyancy lift, and g is acceleration of gravity, the m/s of unit ², α _vthat volume is the cubic expansion coefficient of the plumbous bismuth fluid of V, the 1/K of unit, Δ t is the temperature difference of cold fluid and hot fluid, unit K, Δ t=t ₂-t ₁; L is internal diameter of the pipeline, the m of unit; ν refers to density viscosity, and it is defined as wherein η represents fluid viscosity, and unit is pa.s, and ρ represents fluid density, and unit is kgm ³.

6. a kind of method of judging plumbous bismuth fluid generation thermal stratification as claimed in claim 4, is characterized in that: described inertial force formula is

$\mathrm{Re}=\frac{\mathrm{ul}}{\mathrm{\&nu;}}$

Wherein, Re is fluid inertia force, and l is internal diameter of the pipeline, the m of unit, and u is fluid velocity, the m/s of unit, ν refers to density viscosity, is defined as η represents fluid viscosity, and unit is pa.s, and ρ represents fluid density, and unit is kgm ³.

7. a kind of method of judging plumbous bismuth fluid generation thermal stratification as claimed in claim 4, is characterized in that: described cubic expansion coefficient formula is

$\&PartialD;=\frac{V_{t_2}-V_{t_1}}{V_{t_1}(t_2-t_1)}$

Wherein, volume expansivity, that unit fluid is at t ₁dEG C time volume, that unit fluid is at t ₂dEG C time volume, wherein with unit be m ³, t ₁and t ₂unit be DEG C.