CN110666126A - System and method for stabilizing convection heat exchange coefficient of crystallizer copper plate cooling water - Google Patents
System and method for stabilizing convection heat exchange coefficient of crystallizer copper plate cooling water Download PDFInfo
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- CN110666126A CN110666126A CN201910952155.8A CN201910952155A CN110666126A CN 110666126 A CN110666126 A CN 110666126A CN 201910952155 A CN201910952155 A CN 201910952155A CN 110666126 A CN110666126 A CN 110666126A
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- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 title claims abstract description 233
- 229910052802 copper Inorganic materials 0.000 title claims abstract description 232
- 239000010949 copper Substances 0.000 title claims abstract description 232
- 239000000498 cooling water Substances 0.000 title claims abstract description 185
- 238000000034 method Methods 0.000 title claims abstract description 28
- 230000000087 stabilizing effect Effects 0.000 title claims abstract description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 216
- 230000001105 regulatory effect Effects 0.000 claims abstract description 9
- 238000001816 cooling Methods 0.000 claims abstract description 8
- 239000013078 crystal Substances 0.000 claims description 3
- PTVDYARBVCBHSL-UHFFFAOYSA-N copper;hydrate Chemical compound O.[Cu] PTVDYARBVCBHSL-UHFFFAOYSA-N 0.000 claims description 2
- 230000005611 electricity Effects 0.000 claims description 2
- 238000005259 measurement Methods 0.000 claims description 2
- 238000005266 casting Methods 0.000 abstract description 10
- 229910000831 Steel Inorganic materials 0.000 abstract description 8
- 239000010959 steel Substances 0.000 abstract description 8
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 230000000704 physical effect Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
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Abstract
The invention provides a system and a method for stabilizing the convective heat exchange coefficient of crystallizer copper plate cooling watermeanThe system comprises a processing module, a water quantity control module, a water inlet temperature sensor, a water outlet temperature sensor, an electromagnetic flowmeter and a pneumatic regulating valve. In the production of the slab caster, according to the change of the produced steel grade and the drawing speed, the method dynamically adjusts the water quantity of the cooling water of the copper plate of the crystallizer to ensure that the heat convection coefficient of the cooling water in the water gap of the copper plate of the crystallizer reaches and keeps a preset target value, balances and eliminates the influence caused by the change of the temperature of the cooling water in real time, and avoids the phenomenon that the cooling strength of the crystallizer deviates from the preset value due to the change of the water supply temperature of the cooling water of the copper plate of the crystallizer; the probability of surface cracks of the steel grade sensitive to the hot cracks is reduced, and the surface quality of the casting blank is further improved.
Description
Technical Field
The invention belongs to the technical field of metallurgical continuous casting equipment, and particularly relates to a system and a method for stabilizing the convection heat exchange coefficient of cooling water of a crystallizer copper plate.
Background
In the production of the slab caster, the cooling water flow of the copper plate of the crystallizer needs to be reasonably adjusted according to the change of the produced steel grade and the pulling speed, and the heat convection coefficient of the copper plate in a water gap of the copper plate is changed, so that the aim of adjusting the cooling strength of the crystallizer is fulfilled. The rationality and scientificity of the convective heat transfer coefficient of cooling water in the water gap of the copper plate of the crystallizer are the key points for ensuring good surface quality of the casting blank.
Generally, when the flow rate variation rule of the cooling water of the copper plate of the crystallizer is determined, the temperature of the cooling water is regarded as a constant value (generally 35 ℃), and the influence caused by the variation of the water supply temperature of the cooling water of the copper plate of the crystallizer is not considered; in fact, the water supply temperature of the crystallizer copper plate cooling water can be greatly changed due to the influence of various factors such as weather, environment, different stages of production and the like; in the process, as the physical property of water changes along with the change of temperature, even under the condition of the same cooling water flow, the heat convection coefficient of the cooling water in the water gap of the copper plate of the crystallizer is different due to the difference of water supply temperature, so that the cooling intensity of the crystallizer deviates from a preset value; particularly, when steel grade sensitive to hot cracks is produced, if the water supply temperature of the cooling water of the copper plate of the crystallizer is changed greatly, the probability of cracks on the surface of a casting blank is obviously increased, and more hidden troubles are buried in the subsequent process.
Disclosure of Invention
The invention aims to provide a system for stabilizing the convection heat exchange coefficient of cooling water of a copper plate of a crystallizer, which overcomes the technical problems in the prior art.
The invention also aims to provide a method for stabilizing the convection heat exchange coefficient of the cooling water of the copper plate of the crystallizer, which avoids the phenomenon that the cooling strength of the crystallizer deviates from a preset value due to the change of the water supply temperature of the cooling water of the copper plate of the crystallizer; the probability of surface cracks of the steel grade sensitive to the hot cracks is reduced, and the surface quality of the casting blank is further improved.
Therefore, the technical scheme provided by the invention is as follows:
a system for stabilizing the convection heat exchange coefficient of cooling water of a crystallizer copper plate comprises a crystallizer copper plate cooling water quantity calculation module and a TmeanProcessing module, water quantity control module, inlet water temperature sensor and outlet water temperatureA sensor, an electromagnetic flowmeter, a pneumatic regulating valve;
the inlet water temperature sensor and the outlet water temperature sensor are both connected with TmeanProcess module electrical connection, said TmeanThe processing module is used for receiving signals of the water inlet temperature sensor and the water outlet temperature sensor in real time and calculating the average temperature T of the water inlet and the water outlet of the cooling water of the copper plate of the crystallizermeanThe electromagnetic flow meter, the crystallizer copper plate cooling water volume calculation module and the pneumatic regulating valve are all electrically connected with the water volume control module, the water volume control module is used for receiving water volume information sent by the crystallizer copper plate cooling water volume calculation module and water volume information actually measured by the electromagnetic flow meter in real time and sending an adjusting control signal to the pneumatic regulating valve according to the difference between the two, TmeanThe processing module is electrically connected with the crystallizer copper plate cooling water amount calculating module.
Pneumatic governing valve, electromagnetic flowmeter, the temperature sensor of intaking locate in proper order on the pipeline between crystallizer copper cooling water tank's the delivery port and crystallizer copper water inlet, go out on water temperature sensor locates the pipeline between crystallizer copper delivery port and the water inlet of crystallizer copper cooling water tank.
The crystallizer copper plate cooling water amount calculation module is used for acquiring T in real timemeanAccording to the cross section area A of a single water seam of the copper plate of the crystallizerwsThe perimeter P of the cross section of a single water seam of the copper plate of the crystallizerwsThe number n of the water gaps of the crystallizer copper plate and the target value h of the convective heat transfer coefficient of the cooling water of the crystallizer copper plateaimAnd calculating the water quantity of the cooling water which is required to be supplied to the copper plate of the crystallizer currently, and sending the water quantity information to a water quantity control module.
And a pump is arranged between the pneumatic regulating valve and the crystallizer copper plate cooling water tank.
And a water outlet temperature sensor and a crystallizer copper plate cooling water radiator are sequentially arranged on a pipeline between the water outlet of the crystallizer copper plate and the water inlet of the crystallizer copper plate cooling water tank.
A method for stabilizing the convection heat exchange coefficient of crystallizer copper plate cooling water is a system for stabilizing the convection heat exchange coefficient of crystallizer copper plate cooling water, and comprises the following steps:
step 1) TmeanThe processing module respectively acquires the water inlet temperature T of the current cooling water for the crystal copper plate through the water inlet temperature sensor and the water outlet temperature sensorinAnd the temperature T of the outlet wateroutAnd calculating the average temperature T of the cooling water inlet and outlet of the copper plate of the crystallizermean；
Step 2) a module for calculating the cooling water quantity of the copper plate of the crystallizer passes through TmeanProcessing module real-time acquisition of TmeanAccording to the cross section area A of a single water seam of the copper plate of the crystallizerwsThe perimeter P of the cross section of a single water seam of the copper plate of the crystallizerwsThe number n of the water gaps of the crystallizer copper plate and the target value h of the convective heat transfer coefficient of the cooling water of the crystallizer copper plateaimCalculating the water quantity Q of cooling water which is required to be supplied to the copper plate of the crystallizer currently, and sending the water quantity information to a water quantity control module;
step 3) the water quantity control module receives water quantity information Q sent by the crystallizer copper plate cooling water quantity calculation module and water quantity information actually measured by the electromagnetic flowmeter in real time, sends an adjusting control signal to the pneumatic adjusting valve according to the difference between the water quantity information Q and the water quantity information, and controls the convective heat exchange coefficient of the crystallizer copper plate cooling water to be stabilized to a target value h by adjusting the cooling water quantity supplied to the crystallizer copper plateaim。
The process of calculating the cooling water quantity Q which should be supplied to the crystallizer copper plate currently by the crystallizer copper plate cooling water quantity calculation module in the step 2) is as follows:
step (1) obtaining the average temperature T of inlet water and outlet water of cooling water of a crystallizer copper plate in real timemean；
Step (2) according to the number n of the water gaps of the crystallizer copper plate and the cross section area A of a single water gap of the crystallizer copper platewsThe perimeter P of the cross section of a single water seam of the copper plate of the crystallizerwsCalculating the hydraulic diameter D of the water gap of the copper plate of the single crystallizerh；
Setting three variables Qup、QdownAnd QcurLet Qup＝Qmax、Qdown＝0、Qcur＝0.5(Qup+Qdown) (ii) a Wherein Q ismaxSetting the maximum water quantity m for the cooling water of the copper plate of the crystallizer3/s；
Step (4) according to the average temperature T of the cooling water inlet and outlet of the crystallizer copper platemeanBy QcurCalculating the flow velocity V of cooling water in a water gap of the copper plate of the crystallizer and the corresponding Reynolds number Re of the cooling water of the copper plate of the crystallizerD(TmeanV) Nu corresponding to cooling water of copper plate of crystallizerD(TmeanV) and the convection heat transfer coefficient h of cooling water of the copper plate of the crystallizercur(Tmean,V)；
Step (5) carrying out convection heat exchange coefficient h on cooling water of the copper plate of the crystallizercur(TmeanV) coefficient of heat transfer by convection with cooling water of copper plate of crystallizeraimMaking a comparison if hcur(Tmean,V)＜haimThen, set Qdown＝Qcur，Qcur＝0.5(Qup+Qdown) If h iscur(Tmean,V)＞haimThen, set Qup＝Qcur，Qcur＝0.5(Qup+Qdown) Repeating the step (4) until haim-Δhdown≤h(Tmean,V)≤haim+ΔhupOr (Q)up-Qdown) < Δ Q, then let Q ═ Qcur；
Wherein,. DELTA.hdownThe deviation of the convection heat transfer coefficient target of the cooling water of the copper plate of the crystallizer is W.m-2·K-1；ΔhupThe target deviation of the convection heat transfer coefficient of the cooling water of the copper plate of the crystallizer is W.m-2·K-1；
Step (6) obtaining the average temperature T of the inlet water and the outlet water of the cooling water of the copper plate of the current crystallizermeanIf T this timemeanRelative to last time TmeanThe change exceeds the allowable deviation delta T of the average temperature of the cooling water inlet and outlet of the copper plate of the crystallizermeanAnd (4) repeating the step (3), the step (4) and the step (5), otherwise, not adjusting the water quantity.
Hydraulic diameter D of copper plate water gaphThe calculation formula is as follows:
the calculation formula of the flow velocity V of the cooling water in the water gap of the copper plate of the crystallizer is as follows:
reynolds number Re corresponding to cooling water of crystallizer copper plateD(TmeanV) the calculation formula is as follows:
in the formula, v (T)mean) M is a function of the kinematic viscosity of water with respect to temperature2·s-1；
Nu of Nu corresponding to cooling water of crystallizer copper plateD(TmeanV) the calculation formula is as follows:
in the formula, f is a friction factor of a crystallizer copper plate water seam and is dimensionless; pr (Pr) ofD(Tmean) Is a function of the prandtl number of water with respect to temperature, dimensionless.
Convective heat transfer coefficient h of cooling water of crystallizer copper platecur(TmeanV) the calculation formula is as follows:
in the formula, k (T)mean) W.m as a function of the thermal conductivity of water with respect to temperature-1·K-1。
The friction factor f of the water seam of the copper plate of the crystallizer is calculated by the following formula:
f(Tmean,V)＝(0.790lnReD(Tmean,V)-1.64)-2
function Pr of the Plantt number of water with respect to the temperatureD(Tmean) The following formula:
in the formula, ρ (T)mean) Kg/m as a function of the density of the water with respect to the temperature-3；cp(Tmean) J.kg as a function of the specific heat capacity of water with respect to temperature-1·K-1；ν(Tmean) As a function m of the kinematic viscosity of water with respect to temperature2/s。
The invention has the beneficial effects that:
the invention balances and eliminates the influence caused by the change of the cooling water temperature in real time by dynamically adjusting the water quantity of the cooling water of the copper plate of the crystallizer, and avoids the phenomenon that the cooling strength of the crystallizer deviates from a preset value due to the change of the water supply temperature of the cooling water of the copper plate of the crystallizer; the probability of surface cracks of the steel grade sensitive to the hot cracks is reduced, and the surface quality of the casting blank is further improved.
In order to make the aforementioned and other objects of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
FIG. 1 is a schematic diagram of the system of the present invention;
FIG. 2 thermal conductivity of water versus temperature;
FIG. 3 is a graph of water density versus temperature;
FIG. 4 is a relationship of specific heat of water to temperature;
FIG. 5 is the kinematic viscosity of water versus temperature;
FIG. 6 is a plot of the prandtl number of water versus temperature;
FIG. 7 shows the convection heat transfer coefficient and T of the cooling water of the copper plate of the crystallizermeanThe relationship of (1);
FIG. 8 is a schematic cross-sectional view of the relationship between the inner and outer copper plates of the mold and the cast slab.
Description of reference numerals:
1. a cooling water tank of the crystallizer copper plate; 2. a pump; 3. a pneumatic regulating valve; 4. an electromagnetic flow meter; 5. water (W)A quantity control module; 6. a water quantity calculating module for crystallizer copper plate cooling water; 7. t ismeanA processing module; 8. an inlet water temperature sensor; 9. an effluent temperature sensor; 10. a crystallizer copper plate; 11. a crystallizer copper plate cooling water radiator; 12. casting blanks; 13. an outer arc copper plate of the crystallizer; 14. an inner arc copper plate of the crystallizer; 15. and (5) water gaps of a crystallizer copper plate.
Detailed Description
The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.
The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for complete and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, the same units/elements are denoted by the same reference numerals.
Unless otherwise defined, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Further, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.
Example 1:
the embodiment provides a system for stabilizing convection heat exchange coefficient of cooling water of a crystallizer copper plate, which comprises a pneumatic regulating valve 3, an electromagnetic flowmeter 4, a water quantity control module 5, a water quantity calculation module 6 of the cooling water of the crystallizer copper plate, and a TmeanThe system comprises a processing module 7, a water inlet temperature sensor 8 and a water outlet temperature sensor 9;
the inlet water temperature sensor 8 and the outlet water temperature sensor 9 are both connected with TmeanThe processing module 7 is electrically connected, TmeanThe processing module 7 is used for receiving the inlet water temperature sensor 8 and the outlet water temperature in real timeThe signal of the sensor 9 calculates the average temperature T of the cooling water inlet and outlet of the crystallizer copper platemeanElectromagnetic flowmeter 4, crystallizer copper plate cooling water volume calculation module 6 and pneumatic control valve 3 all are connected with water volume control module 5 electricity, water volume control module 5 is used for receiving water volume information and the water volume information of 4 actual measurements of electromagnetic flowmeter that crystallizer copper plate cooling water volume calculation module 6 sent in real time to send the regulation control signal to pneumatic control valve 3 according to the difference between the two, TmeanThe processing module 7 is electrically connected with the crystallizer copper plate cooling water amount calculating module 6.
Example 2:
on the basis of embodiment 1, this embodiment provides a system for stabilizing crystallizer copper plate cooling water convection heat transfer coefficient, pneumatic control valve 3, electromagnetic flowmeter 4, temperature sensor 8 of intaking locate in proper order on the pipeline between the delivery port of crystallizer copper plate cooling water tank 1 and the crystallizer copper plate water inlet, go out on temperature sensor 9 locates the pipeline between the water outlet of crystallizer copper plate 10 and the water inlet of crystallizer copper plate cooling water tank 1.
As shown in fig. 1, a pump 2 is arranged between the pneumatic control valve 3 and the crystallizer copper plate cooling water tank 1.
And a water outlet temperature sensor 9 and a crystallizer copper plate cooling water radiator 11 are sequentially arranged on a pipeline between the water outlet of the crystallizer copper plate 10 and the water inlet of the crystallizer copper plate cooling water tank 1.
Wherein, the crystallizer copper plate cooling water quantity calculation module 6 is used for acquiring T in real timemeanAccording to the cross section area A of a single water seam of the copper plate of the crystallizerwsThe perimeter P of the cross section of a single water seam of the copper plate of the crystallizerwsThe number n of the water gaps 15 of the crystallizer copper plate and the target value h of the convective heat transfer coefficient of the cooling water of the crystallizer copper plateaimThe amount of cooling water to be supplied to the copper plate of the mold at present is calculated, and the information of the amount of cooling water is sent to the water amount control module 5.
Example 3:
the embodiment provides a method for stabilizing the convection heat exchange coefficient of cooling water of a copper plate of a crystallizer, and a system for stabilizing the convection heat exchange coefficient of the cooling water of the copper plate of the crystallizer, which is provided by the embodiment 1, comprises the following steps:
step 1) TmeanThe processing module 7 respectively obtains the water inlet temperature T of the current cooling water for the crystal copper plate through the water inlet temperature sensor 8 and the water outlet temperature sensor 9inAnd the temperature T of the outlet wateroutAnd calculating the average temperature T of the cooling water inlet and outlet of the copper plate of the crystallizermean；
Step 2) a module for calculating the cooling water quantity of the copper plate of the crystallizer passes through TmeanProcessing module 7 obtains T in real timemeanAccording to the cross section area A of a single water seam of the copper plate of the crystallizerwsThe perimeter P of the cross section of a single water seam of the copper plate of the crystallizerwsThe number n of the water gaps 15 of the crystallizer copper plate and the target value h of the convective heat transfer coefficient of the cooling water of the crystallizer copper plateaimCalculating the water quantity Q of cooling water which is required to be supplied to the copper plate of the crystallizer currently, and sending the water quantity information to a water quantity control module 5;
step 3) the water quantity control module 5 receives the water quantity information Q sent by the crystallizer copper plate cooling water quantity calculation module 6 and the water quantity information actually measured by the electromagnetic flow meter 4 in real time, sends an adjusting control signal to the pneumatic adjusting valve 3 according to the difference between the water quantity information Q and the water quantity information, and controls the convective heat exchange coefficient of the crystallizer copper plate cooling water to be stable to a target value h by adjusting the cooling water quantity supplied to the crystallizer copper plateaim。
The invention balances and eliminates the influence caused by the change of the cooling water temperature in real time by dynamically adjusting the water quantity of the cooling water of the copper plate of the crystallizer, and avoids the phenomenon that the cooling strength of the crystallizer deviates from a preset value due to the change of the water supply temperature of the cooling water of the copper plate of the crystallizer; the probability of surface cracks of the steel grade sensitive to the hot cracks is reduced, and the surface quality of the casting blank is further improved.
Example 4:
on the basis of embodiment 3, this embodiment provides a method for stabilizing the convective heat transfer coefficient of the cooling water of the copper plate of the crystallizer, and the procedure of calculating the cooling water amount Q that should be currently supplied to the copper plate 10 of the crystallizer by the cooling water amount calculation module 6 in step 2) is as follows:
step (1) obtaining the average temperature T of inlet water and outlet water of cooling water of a crystallizer copper plate in real timemean；
Step (2) according to the number n of the water gaps 15 of the crystallizer copper plate and the cross section area A of a single water gap of the crystallizer copper platewsThe perimeter P of the cross section of a single water seam of the copper plate of the crystallizerwsCalculating the hydraulic diameter D of the water gap of the copper plate of the single crystallizerh；
Setting three variables Qup、QdownAnd QcurLet Qup＝Qmax、Qdown＝0、Qcur＝0.5(Qup+Qdown) (ii) a Wherein Q ismaxSetting the maximum water quantity m for the cooling water of the copper plate of the crystallizer3/s；
Step (4) according to the average temperature T of the cooling water inlet and outlet of the crystallizer copper platemeanBy QcurCalculating the flow velocity V of cooling water in a water gap of the copper plate of the crystallizer and the corresponding Reynolds number Re of the cooling water of the copper plate of the crystallizerD(TmeanV) Nu corresponding to cooling water of copper plate of crystallizerD(TmeanV) and the convection heat transfer coefficient h of cooling water of the copper plate of the crystallizercur(Tmean,V)；
Step (5) carrying out convection heat exchange coefficient h on cooling water of the copper plate of the crystallizercur(TmeanV) coefficient of heat transfer by convection with cooling water of copper plate of crystallizeraimMaking a comparison if hcur(Tmean,V)＜haimThen, set Qdown＝Qcur，Qcur＝0.5(Qup+Qdown) If h iscur(Tmean,V)＞haimThen, set Qup＝Qcur，Qcur＝0.5(Qup+Qdown) Repeating the step (4) until haim-Δhdown≤h(Tmean,V)≤haim+ΔhupOr (Q)up-Qdown) < Δ Q, then let Q ═ Qcur；
Wherein,. DELTA.hdownThe deviation of the convection heat transfer coefficient target of the cooling water of the copper plate of the crystallizer is W.m-2·K-1；ΔhupCooling water pair for crystallizer copper plateTarget deviation of heat transfer coefficient, W.m-2·K-1；
Step (6) obtaining the average temperature T of the inlet water and the outlet water of the cooling water of the copper plate of the current crystallizermeanIf T this timemeanRelative to last time TmeanThe change exceeds the allowable deviation delta T of the average temperature of the cooling water inlet and outlet of the copper plate of the crystallizermeanAnd (4) repeating the step (3), the step (4) and the step (5), otherwise, not adjusting the water quantity.
Example 5:
on the basis of embodiment 4, this embodiment provides a method for stabilizing the convective heat transfer coefficient of the cooling water of the copper plate of the crystallizer, and the hydraulic diameter D of the water gap of the copper platehThe calculation formula is as follows:
the calculation formula of the flow velocity V of the cooling water in the water gap of the copper plate of the crystallizer is as follows:
reynolds number Re corresponding to cooling water of crystallizer copper plateD(TmeanV) the calculation formula is as follows:
in the formula, v (T)mean) M is a function of the kinematic viscosity of water with respect to temperature2·s-1(ii) a As shown in fig. 5;
nu of Nu corresponding to cooling water of crystallizer copper plateD(TmeanV) the calculation formula is as follows:
in the formula, f is a friction factor of a crystallizer copper plate water seam and is dimensionless; pr (Pr) ofD(Tmean) Prandtl number for waterFunction of temperature, dimensionless.
The calculation formula of the friction factor f of the crystallizer copper plate water seam is as follows:
f(Tmean,V)＝(0.790lnReD(Tmean,V)-1.64)-2
function Pr of the Plantt number of water with respect to the temperatureD(Tmean) The following formula:
in the formula, ρ (T)mean) Kg/m as a function of the density of the water with respect to the temperature-3；cp(Tmean) J.kg as a function of the specific heat capacity of water with respect to temperature-1·K-1；ν(Tmean) As a function m of the kinematic viscosity of water with respect to temperature2And s. As shown in fig. 3, 4 and 5, respectively. The prandtl number of water as a function of temperature is shown in fig. 6.
Example 6:
on the basis of embodiment 4, this embodiment provides a method for stabilizing the convective heat transfer coefficient of the cooling water of the copper plate of the crystallizer, i.e., the convective heat transfer coefficient h of the cooling water of the copper plate of the crystallizercur(TmeanV) the calculation formula is as follows:
in the formula, k (T)mean) W.m as a function of the thermal conductivity of water with respect to temperature-1·K-1. As shown in fig. 2.
Example 7:
according to the specific working conditions on site, the method of the invention is adopted to stabilize the convective heat transfer coefficient of the crystallizer copper plate cooling water at the target value haim。
As shown in FIG. 7, h in this embodimentaim(15000W·m-2·K-1) The cooling water flow (2500L/min, 2750L/min and 3000L/min respectively) of different crystallizer copper plates is horizontal line and corresponds to different temperaturesThe convective heat transfer coefficients are a series of curves, and their respective convective heat transfer coefficients all increase with increasing temperature.
As shown in FIG. 7, the average temperature T of the inlet water and the outlet water of the cooling water of the copper plate of the crystallizer at present is assumedmeanAt the temperature of 41.5 ℃, when the cooling water flow of the crystallizer copper plate is 2750L/min, the corresponding convective heat transfer coefficient is a target value, namely haim＝15000W·m-2·K-1(ii) a If the average temperature T of the cooling water inlet and outlet of the crystallizer copper platemeanWhen the temperature is reduced to 33.5 ℃, if the cooling water flow rate is maintained at 2750L/min, the corresponding convective heat transfer coefficient is lower than the target value haimAt this time, the flow rate of the cooling water can be increased to 3000L/min, so that the corresponding convective heat transfer coefficient is stabilized at the target value haim(ii) a If the average temperature T of the cooling water inlet and outlet of the crystallizer copper platemeanWhen the temperature is increased to 52.5 ℃, if the cooling water flow rate is maintained at 2750L/min, the corresponding convective heat transfer coefficient is higher than the target value haimAt this time, the flow rate of the cooling water is reduced to 2500L/min, so that the corresponding convective heat transfer coefficient is stabilized at the target value haim。
The invention aims to solve the problem that the water supply temperature of the cooling water of the crystallizer copper plate of the slab caster is greatly changed under the influence of various factors such as weather, environment, different stages of production and the like, and the convection heat exchange coefficient of the cooling water in the water gap of the crystallizer copper plate is different due to different water supply temperatures even under the condition of the same cooling water flow because the physical properties (heat conductivity coefficient, dynamic viscosity, specific heat, density and the like) of the water are different at different temperatures, so that the cooling intensity of the crystallizer deviates from a preset value; particularly, when steel grade sensitive to hot cracks is produced, the probability of cracks appearing on the surface of a casting blank is obviously increased, and more hidden troubles are buried in the subsequent process.
As shown in fig. 8, the mold copper plate 10 provides support for the casting slab and cools the casting slab, and includes a mold outer arc copper plate 13 and a mold inner arc copper plate 14, and a plurality of mold copper plate water gaps 15 are formed on each of the mold outer arc copper plate 13 and the mold inner arc copper plate 14.
It will be understood by those of ordinary skill in the art that the foregoing embodiments are specific examples for carrying out the invention, and that various changes in form and details may be made therein without departing from the spirit and scope of the invention in practice. The components and structures of the present embodiments that are not described in detail are well known in the art and do not constitute essential structural elements or elements.
Claims (10)
1. The utility model provides a system for stabilize crystallizer copper cooling water convection heat transfer coefficient which characterized in that: comprises a pneumatic regulating valve (3), an electromagnetic flowmeter (4), a water quantity control module (5), a crystallizer copper plate cooling water quantity calculation module (6) and a TmeanThe device comprises a processing module (7), an inlet water temperature sensor (8) and an outlet water temperature sensor (9);
the inlet water temperature sensor (8) and the outlet water temperature sensor (9) are both connected with TmeanThe processing module (7) is electrically connected, TmeanThe processing module (7) is used for receiving signals of the inlet water temperature sensor (8) and the outlet water temperature sensor (9) in real time and calculating the average temperature T of inlet water and outlet water of cooling water of the copper plate of the crystallizermeanElectromagnetic flowmeter (4), crystallizer copper plate cooling water volume calculation module (6) and pneumatic control valve (3) all are connected with water volume control module (5) electricity, water volume control module (5) are used for receiving water volume information and electromagnetic flowmeter (4) actual measurement's water volume information that crystallizer copper plate cooling water volume calculation module (6) sent in real time to send regulation control signal to pneumatic control valve (3) according to the difference between the two, TmeanThe processing module (7) is electrically connected with the crystallizer copper plate cooling water amount calculating module (6).
2. The system for stabilizing the convection heat exchange coefficient of the cooling water of the copper plate of the crystallizer as claimed in claim 1, wherein: pneumatic governing valve (3), electromagnetic flow meter (4), temperature sensor (8) of intaking locate in proper order on the pipeline between the delivery port of crystallizer copper cooling water tank (1) and crystallizer copper water inlet, go out on water temperature sensor (9) locate the pipeline between the water inlet of crystallizer copper (10) delivery port and crystallizer copper cooling water tank (1).
3. The system for stabilizing the convection heat exchange coefficient of the cooling water of the copper plate of the crystallizer as claimed in claim 1, wherein: the crystallizer copper plate cooling water amount calculation module (6) is used for acquiring T in real timemeanAccording to the cross section area A of a single water seam of the copper plate of the crystallizerwsThe perimeter P of the cross section of a single water seam of the copper plate of the crystallizerwsThe number n of the water gaps (15) of the crystallizer copper plate and a target value h of the convective heat transfer coefficient of the cooling water of the crystallizer copper plateaimThe amount Q of the cooling water to be supplied to the mold copper plate (10) at present is calculated, and the information of the amount of the cooling water is sent to a water amount control module (5).
4. The system for stabilizing the convection heat exchange coefficient of the cooling water of the copper plate of the crystallizer as claimed in claim 2, wherein: and a pump (2) is arranged between the pneumatic regulating valve (3) and the crystallizer copper plate cooling water tank (1).
5. The system for stabilizing the convection heat exchange coefficient of the cooling water of the copper plate of the crystallizer as claimed in claim 2, wherein: and an outlet water temperature sensor (9) and a crystallizer copper plate cooling water radiator (11) are sequentially arranged on a pipeline between a water outlet of the crystallizer copper plate (10) and a water inlet of the crystallizer copper plate cooling water tank (1).
6. A method for stabilizing the convection heat exchange coefficient of the cooling water of the copper plate of the crystallizer, which uses the system for stabilizing the convection heat exchange coefficient of the cooling water of the copper plate of the crystallizer of claim 1, and is characterized by comprising the following steps of:
step 1) TmeanThe processing module (7) respectively acquires the water inlet temperature T of the current cooling water of the crystal copper plate through the water inlet temperature sensor (8) and the water outlet temperature sensor (9)inAnd the temperature T of the outlet wateroutAnd calculating the average temperature T of the cooling water inlet and outlet of the copper plate of the crystallizermean；
Step 2), the water quantity calculation module (6) of the crystallizer copper plate cooling water passes through TmeanProcessing module (7) real-time acquisitionTmeanAccording to the cross section area A of a single water seam of the copper plate of the crystallizerwsThe perimeter P of the cross section of a single water seam of the copper plate of the crystallizerwsThe number n of the water gaps of the crystallizer copper plate and the target value h of the convective heat transfer coefficient of the cooling water of the crystallizer copper plateaimCalculating the water quantity Q of cooling water which is required to be supplied to the crystallizer copper plate (10) at present, and sending the water quantity information to a water quantity control module (5);
step 3) the water quantity control module (5) receives the water quantity information Q sent by the crystallizer copper plate cooling water quantity calculation module (6) and the water quantity information actually measured by the electromagnetic flow meter (4) in real time, sends an adjusting control signal to the pneumatic adjusting valve (3) according to the difference between the water quantity information Q and the water quantity information, and controls the convective heat transfer coefficient of the crystallizer copper plate cooling water to be stabilized to a target value h by adjusting the cooling water quantity supplied to the crystallizer copper plateaim。
7. The method for stabilizing the convection heat exchange coefficient of the cooling water of the copper plate of the crystallizer as claimed in claim 6, wherein the method comprises the following steps: the process of calculating the cooling water quantity Q which should be supplied to the copper plate of the crystallizer currently by the crystallizer copper plate cooling water quantity calculation module (6) in the step 2) is as follows:
step (1) obtaining the average temperature T of inlet water and outlet water of cooling water of a crystallizer copper plate in real timemean；
Step (2) according to the number n of the water gaps (15) of the crystallizer copper plate and the cross section area A of a single water gap of the crystallizer copper platewsThe perimeter P of the cross section of a single water seam of the copper plate of the crystallizerwsCalculating the hydraulic diameter D of the water gap of the copper plate of the single crystallizerh；
Setting three variables Qup、QdownAnd QcurLet Qup＝Qmax、Qdown＝0、Qcur＝0.5(Qup+Qdown) (ii) a Wherein Q ismaxSetting the maximum water quantity m for the cooling water of the copper plate of the crystallizer3/s；
Step (4) according to the average temperature T of the cooling water inlet and outlet of the crystallizer copper platemeanBy QcurCalculating the flow velocity V of cooling water in a water gap of the crystallizer copper plate, and cooling the crystallizer copper plateReynolds number Re corresponding to waterD(TmeanV) Nu corresponding to cooling water of copper plate of crystallizerD(TmeanV) and the convection heat transfer coefficient h of cooling water of the copper plate of the crystallizercur(Tmean,V)；
Step (5) carrying out convection heat exchange coefficient h on cooling water of the copper plate of the crystallizercur(TmeanV) coefficient of heat transfer by convection with cooling water of copper plate of crystallizeraimMaking a comparison if hcur(Tmean,V)＜haimThen, set Qdown＝Qcur，Qcur＝0.5(Qup+Qdown) If h iscur(Tmean,V)＞haimThen, set Qup＝Qcur，Qcur＝0.5(Qup+Qdown) Repeating the step (4) until haim-Δhdown≤h(Tmean,V)≤haim+ΔhupOr (Q)up-Qdown) < Δ Q, then let Q ═ Qcur；
Wherein,. DELTA.hdownThe deviation of the convection heat transfer coefficient target of the cooling water of the copper plate of the crystallizer is W.m-2·K-1；ΔhupThe target deviation of the convection heat transfer coefficient of the cooling water of the copper plate of the crystallizer is W.m-2·K-1；
Step (6) obtaining the average temperature T of the inlet water and the outlet water of the cooling water of the copper plate of the current crystallizermeanIf T this timemeanRelative to last time TmeanThe change exceeds the allowable deviation delta T of the average temperature of the cooling water inlet and outlet of the copper plate of the crystallizermeanAnd (4) repeating the step (3), the step (4) and the step (5), otherwise, not adjusting the water quantity.
8. The method for stabilizing the convection heat exchange coefficient of the cooling water of the copper plate of the crystallizer as claimed in claim 7, wherein the method comprises the following steps: hydraulic diameter D of single crystallizer copper plate water seamhThe calculation formula is as follows:
the calculation formula of the flow velocity V of the cooling water in the water gap of the copper plate of the crystallizer is as follows:
reynolds number Re corresponding to cooling water of crystallizer copper plateD(TmeanV) the calculation formula is as follows:
in the formula, v (T)mean) M is a function of the kinematic viscosity of water with respect to temperature2·s-1；
Nu of Nu corresponding to cooling water of crystallizer copper plateD(TmeanV) the calculation formula is as follows:
in the formula, f is a friction factor of a crystallizer copper plate water seam and is dimensionless; pr (Pr) ofD(Tmean) Is a function of the prandtl number of water with respect to temperature, dimensionless.
9. The method for stabilizing the convection heat exchange coefficient of the cooling water of the copper plate of the crystallizer as claimed in claim 7, wherein the method comprises the following steps: convective heat transfer coefficient h of cooling water of crystallizer copper platecur(TmeanV) the calculation formula is as follows:
in the formula, k (T)mean) W.m as a function of the thermal conductivity of water with respect to temperature-1·K-1。
10. The method for stabilizing the convection heat exchange coefficient of the cooling water of the copper plate of the crystallizer as claimed in claim 8, wherein the method comprises the following steps: the friction factor f of the water seam of the copper plate of the crystallizer is calculated by the following formula:
f(Tmean,V)＝(0.790lnReD(Tmean,V)-1.64)-2
function Pr of the Plantt number of water with respect to the temperatureD(Tmean) The following formula:
in the formula, ρ (T)mean) Kg/m as a function of the density of the water with respect to the temperature-3；cp(Tmean) J.kg as a function of the specific heat capacity of water with respect to temperature-1·K-1；ν(Tmean) As a function m of the kinematic viscosity of water with respect to temperature2/s。
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