CN112800607B - Discretization test method and device for impact jet enhanced heat exchange characteristics - Google Patents
Discretization test method and device for impact jet enhanced heat exchange characteristics Download PDFInfo
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Abstract
The invention provides a discretization test method for enhancing heat exchange characteristics of impact jet flow, which comprises the following steps: designing a testing device, arranging a testing cylinder below different positions of a heat exchange surface, dispersing a testing object into each testing point, and performing impact jet reinforced heat exchange experiments: the upper supporting plate of the testing device is moved upwards together with the testing cylinder, so that all parts of the testing cylinder are higher than the heat insulation material and are in direct contact with the heating environment, and a baffle is arranged between the upper supporting plate and the supporting sleeve, so that the upper supporting plate does not slide off in the heating process; the whole testing device is placed in a heating furnace to be heated to a preset temperature; opening a furnace door, resetting the upper supporting plate and the test cylinder in the furnace, rapidly covering a heat preservation cover in the furnace, removing the upper heat preservation cover after the test device is arranged at a corresponding position, rapidly opening a jet valve, and recording the surface temperature; and calculating a heat convection coefficient. The method is suitable for discretization research of the heat exchange characteristics of impact jet flow with large temperature difference and intense heat exchange.
Description
Technical Field
The invention relates to the technical field of impact jet heat and mass transfer research, in particular to a discretization test method and device for enhancing heat exchange characteristics of impact jet.
Background
The impact jet enhanced heat exchange means that a nozzle is used for jetting fluid (gas, liquid, water mist and the like) with certain pressure to a heat exchange surface vertically or at a certain angle so as to realize enhanced heating or cooling of the impact surface. The impact jet generally has larger impact pressure, the fluid at the heat exchange surface has high flow speed and thin boundary layer, and can obtain great heat exchange capacity, thus being an extremely effective heat transfer enhancement method. In addition, the impact jet enhanced heat exchange has the characteristic of good heat exchange intensity controllability (the cooling intensity can be effectively controlled by adjusting parameters such as jet pressure, jet distance, jet angle, jet layout mode and the like). Therefore, the impact jet enhanced heat transfer is widely applied to the fields of electronic component cooling, such as paper drying, glass heat treatment, continuous casting two-cooling jet cooling, ultra-fast cooling technology, rail head air cooling quenching, water mist quenching and the like.
The research on heat exchange characteristics of impact jet reinforced heat exchange is a precondition for better application to production practice. Whereas impingement jet enhanced heat transfer characteristics are related to many factors such as nozzle shape, spray surface roughness, spray distance, spray pressure, spray media, nozzle spacing, interference between multiple jets, and the like. In addition, the pressure, speed and direction of jet flow after impacting the heat exchange surface are changed drastically, so that the heat exchange strength of different positions of the heat exchange surface is also different. Therefore, the research on the law and the characteristics of the impact jet enhanced heat exchange is always a research hotspot in the field of heat and mass transfer.
The strong intensity of heat exchange at a certain position of the impact jet reinforced heat exchange interface is generally characterized by Nu number (abbreviated as Nu)Is a dimensionless number in fluid mechanics and heat transfer science, and has the calculation formula ofWherein L is the geometric characteristic length of the heat transfer surface; k is the thermal conductivity of the stationary fluid; h is the surface convection heat transfer coefficient of the fluid and represents the heat transfer capability between the fluid and the solid surface. The physical meaning of h is that the temperature difference between the surface of an object and the nearby air is 1 ℃, the heat exchanged with the nearby air through convection in unit time (1 second) and unit area is an indispensable parameter with larger acquisition difficulty in the research of the enhanced heat exchange characteristics of impact jet flow, and the calculation formula is that>Where q is the heat exchanged between the solid surface per unit area and the fluid per unit time, called heat flux density; t is t w 、t ∞ The temperature of the solid surface and the fluid, respectively.
The prior art research impact jet heat exchange characteristic direct measurement method mainly comprises a steady-state experimental method and a transient experimental method.
1) Steady state experimental method: the method is characterized in that a heat exchange workpiece is electrified and heated or a heat source with known heat is continuously added at the bottom, and the surface continuously impacts jet flow heat exchange, namely, heat is continuously provided for the workpiece while the surface jet flow heat exchange is performed, so that the provided heat and the heat taken away by the jet flow reach a stable balance state, and further, the convection heat exchange coefficient can be calculated through the known input heat quantity value q and the measured temperature value of a heat exchange interface. The steady-state method has the defects of harsh requirements on experimental conditions such as boundary conditions, external environments and the like, long experimental period and large error, is only suitable for working conditions with small temperature difference and not severe heat exchange, can reach a steady state, and can not realize the steady state of the experimental process by adopting the steady-state method, such as supersonic wind jet impact jet, ultra-fast cold impact jet heat exchange, high temperature difference impact jet heat exchange (the temperature difference is more than 400 ℃), and the like, and can only be realized by adopting a transient method.
2) Transient experimental method: the transient experiment generally refers to that a workpiece to be heat-exchanged is integrally kept at a certain temperature in advance before heat exchange, then forced heating or cooling heat exchange is carried out on the workpiece through jet flow, so that longitudinal temperature gradients (the longitudinal temperature gradients refer to temperature gradients generated by the vertically downward heat exchange surface) are generated on the surface and the inside of the workpiece, instantaneous heat transfer is calculated through measuring the temperature gradients, and then the convective heat exchange coefficient is calculated. Transient experiments have the advantages of short period and relatively small error, and are widely applied to the measurement of convective heat transfer coefficients in recent years. However, in transient experiments, in order to maintain the heat exchange process for a certain time and measure the longitudinal temperature gradient of the workpiece, a certain thickness of the workpiece needs to be measured, and the heat transfer process is essentially a conjugate heat transfer process comprising heat transfer between fluid and solid, heat transfer between different positions of fluid and heat transfer between different positions inside the solid. When the workpiece has a temperature gradient, the part with high heat temperature can transfer heat to the part with low temperature, so that the test result cannot completely reflect the heat exchange capability of the fluid, and is related to the material, the size and the like of a heat exchange object to a certain extent, and the results obtained by the workpiece with the same jet fluid working condition, different materials or workpieces with different thicknesses are different in the existing transient experimental study on the same jet fluid working condition. In addition, a thermocouple is generally required to be arranged in the workpiece for transient experiments to measure the transient temperature in the workpiece, and on one hand, the machining error of a buried hole of the thermocouple can influence the test result; on the other hand, the embedding of the thermocouple can also influence the heat transfer rule inside the material so as to influence the experimental result; in the third aspect, the calculation process of the whole workpiece in the transient experiment needs to be performed through a complex two-dimensional or three-dimensional calculation process (such as a reverse heat transfer method for obtaining a convection heat exchange coefficient), so that the calculation amount is large.
Disclosure of Invention
In order to solve the technical problems of the background technology, the invention provides a discretization test method and a discretization test device for enhancing heat exchange characteristics of impact jet flow, which are suitable for discretization research of heat exchange characteristics of impact jet flow with large temperature difference and intense heat exchange.
In order to achieve the above purpose, the invention is realized by adopting the following technical scheme:
a discretization test method for enhancing heat exchange characteristics of impact jet flow comprises the following steps:
step one, designing a testing device, wherein the testing device comprises an upper supporting plate, a testing cylinder, a heat insulation material, a guide column and a lower supporting plate, the upper supporting plate contacts a workpiece, the testing cylinder is arranged below different positions of the heat exchange surface of the upper supporting plate, a testing object is scattered into testing points, and the lower surface of each testing cylinder and the testing cylinder are separated by the heat insulation material so as to block heat transfer between each testing point and between the testing point and the outside;
fitting a physical property parameter equation;
step three, testing the emissivity of the material;
step four, impact jet reinforced heat exchange experiment:
1) Before heating, the workpiece is placed at a test position, and the relative positions of the workpiece, the nozzle and the thermal imager are adjusted;
2) The upper supporting plate of the testing device is moved upwards together with the testing cylinder, so that all parts of the testing cylinder are higher than the heat insulation material and are in direct contact with the heating environment, and a baffle is arranged between the upper supporting plate and the supporting sleeve, so that the upper supporting plate does not slide off in the heating process;
3) The whole testing device is placed in a heating furnace to be heated to a preset temperature;
4) The furnace door is opened, the upper supporting plate and the test cylinder are reset in the furnace, and a heat preservation cover is quickly covered in the furnace to prevent the heat dissipation in the transferring process from affecting the experimental precision;
5) After the testing device is placed at the corresponding position, the upper heat preservation cover is removed, the jet valve is quickly opened, and the surface temperature is recorded;
and fifthly, calculating the convection heat transfer coefficient.
Further, the test cylinder of each test point should satisfy two conditions simultaneously:
1) The diameter of the test cylinder meets the condition of an infinitely long cylinder for engineering heat exchange, namelyWherein lambda is a cylinderThe thermal conductivity of the material; r is the diameter of the test cylinder; h is a preset value of a convection heat transfer coefficient of the heat transfer surface of the end part of the test cylinder, and the range of the value of h is as follows: the predicted value h is 20-200 when the gas jet is impacted at a constant speed, and the predicted value h is 200-800 when the gas jet is impacted at a sonic speed or supersonic speed; taking 500-1000 of the estimated value h during water mist quenching; taking 1000-15000 as a predicted value h in forced convection of water; the estimated value h is estimated according to the empirical value under the special working condition; units: />
2) The length of the test cylinder should be satisfied, and the temperature of the lower surface of the test cylinder does not change along with the temperature reduction of the upper surface in the whole test process.
Further, in the second step, the method for fitting the physical property parameter equation includes: inputting the following sentences in matlab, selecting the type and the precision of an equation according to requirements by using an automatically ejected cftool, and fitting to obtain a thermophysical parameter equation changing along with temperature:
clear；
Cftool；
x＝[A1,A2,···，An]；
y＝[C1,C2,···，Cn]；
wherein: A1-An and C1-Cn refer to different temperature values and corresponding thermophysical parameter values at the temperature values, respectively.
Furthermore, in the third step, the thermal imaging instrument or the infrared thermometer is required to measure the temperature of the heat exchange surface, and the emissivity of different materials in different environments, different roughness and different temperatures also causes different measurement results, so that the emissivity of the experimental materials is required to be obtained before the study; the testing method comprises the following steps:
1) Setting a calibrated thermocouple in the heating furnace, and heating the heating furnace to a set temperature;
2) Placing the test material in a furnace and sufficiently heating the test material; the thermal insulation cover is used in the furnace to prevent heat dissipation, the thermal insulation cover is taken out and positioned, the thermal imager to be used is used for shooting and recording instantaneous temperature pictures, the emissivity value of the thermal imager is adjusted, the temperature measured by the thermal imager is consistent with the thermocouple temperature in the furnace, and the emissivity is the emissivity of the material at the temperature.
Further, the calculating of the convective heat transfer coefficient in the fifth step includes the following steps:
1) Fitting the temperature values obtained from each test point along with the time to a polynomial equation to obtain the following form:
2) The temperature values of the nodes below the test cylinder over time were calculated using equation 2 as follows:
in the middle of
3) The following heat transfer coefficient of each test point with temperature is calculated by using the following equation 3:
4) When δτ and δx are selected, the following conditions are satisfied:
in the above calculation formulas 1 to 4, m denotes a polynomial order, i= … t denotes a time step, t denotes an end time of the measured temperature, n denotes a position node number,temperature value at time i for node with index n,/>Indicating the temperature of the upper surface of the test point,refers to the temperature of the lower end face of the test cylinder +.>Temperature of the previous position node of (c) at time i,/-, and (c)>For an unreal virtual point, δτ represents the time interval, δx represents the position interval of each node of the test cylinder, ρ is the density fitting equation with temperature, c p And lambda is a fitting equation of the heat conductivity coefficient of the material along with the change of temperature.
The testing device used in the discretization testing method for the impact jet reinforced heat exchange characteristic comprises an upper supporting plate, a testing cylinder, a heat insulation material, a guide post, a guide sleeve, a supporting sleeve, a lower supporting plate, a connecting sheet and a heat insulation ring. The upper supporting plate is provided with a round hole or a square hole at the test position. The connecting piece is a strap Kong Baopian, the thickness of the connecting piece is not more than 1mm, the appearance of the connecting piece is consistent with the shape and the size of holes at each testing position on the upper supporting plate, and the diameter of the inner hole is consistent with the diameter of the testing cylinder. The inside and outside of connection piece respectively with test cylinder and last backup pad welding, make the upper surface of connection piece be higher than test cylinder and last backup pad before the welding. And after welding, integrally processing the upper supporting plate, the test cylinder and the connecting sheet, so that the upper plane of the whole device is the same plane and the same roughness. The gap between the test cylinder and the upper support plate hole is filled with heat insulation material.
The heat insulating material is a heat insulating plate with certain machining performance, and holes are drilled at corresponding test positions to install the test cylinders. The diameter of the drilling hole is slightly larger than that of the test cylinder, so that the test cylinder can slide in the hole smoothly.
The thickness of the heat insulation material is larger than the length of the test cylinder, so that the lower surface of the test cylinder is ensured not to exchange heat with the environment in the experimental process. A supporting sleeve and a lower supporting plate with certain rigidity are respectively arranged outside and under the heat insulating material and are used for preventing the heat insulating material from being damaged in the transferring process. A guide post and a guide sleeve are arranged between the upper support plate and the lower support plate. The upper part of the guide post is fixed with the upper supporting plate, and the lower part of the guide sleeve is fixed with the lower supporting plate. And a through hole which is slightly smaller than the outer diameter of the guide sleeve and larger than the outer diameter of the guide post is processed on the lower support plate at the position of the guide post, so that the guide post can pass through the lower support plate through the hole. And processing a preformed hole at a position corresponding to the test cylinder on the lower supporting plate for installing a thermocouple.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the invention, after the whole test plane is discretized into the test cylinder under each test point, no heat is transferred between each test point and other test points, each test point can more truly reflect the instantaneous temperature value of the point, the influence of heat conduction in the material on a calculation result is prevented, and the calculated convective heat transfer coefficient can more truly reflect the heat transfer capability and the heat transfer rule of jet flow.
2. According to the invention, the heat exchange body is scattered into heat exchange points at different positions, and each test point after the heat exchange points are scattered can meet the calculation condition of the one-dimensional heat conduction problem, so that the accuracy can be improved, the complex two-dimensional or three-dimensional heat conduction problem can be simplified into a simple one-dimensional heat conduction problem, and the calculation amount is greatly reduced.
3. Compared with the most commonly used reverse heat transfer method at present, the discretization test method of the invention does not need to embed a thermocouple in the material, and eliminates calculation errors caused by machining errors of thermocouple mounting holes and the influence of the thermocouple mounting holes on the temperature field in the material. .
Drawings
FIG. 1 is a schematic diagram of a discretization test research method and device for enhancing heat exchange characteristics by impact jet flow;
FIG. 2 is a cross-sectional view of a discretized test study method and device for enhancing heat exchange characteristics by impact jet flow;
FIG. 3 is a partial enlarged view of a discretized test study method and device for enhancing heat exchange characteristics by impact jet flow;
FIG. 4 is a schematic diagram of a discretization test study method for enhancing heat exchange characteristics by impact jet and a lower support plate of the discretization test study method;
FIG. 5 is a node schematic diagram of a discretization test research method for enhancing heat exchange characteristics by impact jet.
Detailed Description
The following detailed description of the embodiments of the invention is provided with reference to the accompanying drawings.
A discretization test method for enhancing heat exchange characteristics of impact jet flow comprises the following steps:
3) Step one, designing a testing device, arranging a testing cylinder 2 below different positions of a heat exchange surface, and dispersing a testing object into each testing point; as shown in fig. 1-4, the testing device comprises an upper supporting plate 1, a testing cylinder 2, a heat insulation material 3, a guide post 4, a guide sleeve 5, a supporting sleeve 6, a lower supporting plate 7, a connecting sheet 8 and a heat insulation ring 9.
As shown in fig. 1 and 3, the upper support plate 1 is made of a material identical to that of the test cylinder, and is provided with a circular hole or a square hole at the test position, and the diameter of the hole (or the side length of the square hole) is larger than that of the test cylinder. The connecting piece 8 is a strap Kong Baopian, the thickness of the connecting piece is not more than 1mm, the connecting piece is used for connecting the test cylinder 2 and the upper supporting plate 1, the appearance of the connecting piece is consistent with the shape and the size of a hole at each test position on the upper supporting plate 1, the diameter of an inner hole is consistent with the diameter of the test cylinder 2, and the material is consistent with the test cylinder. The inside and outside of the connecting sheet 8 are respectively welded with the test cylinder 2 and the upper support plate 1, and the upper surface of the connecting sheet 8 is higher than the test cylinder 2 and the upper support plate 1 before welding. After welding, the upper support plate 1, the test cylinder 2 and the connecting sheet 8 are integrally processed, so that the upper plane of the whole device is the same plane and the same roughness. The gap between the test cylinder 2 and the hole of the upper support plate 2 is filled with a heat insulating material 9.
As shown in fig. 1, 2 and 4, the heat insulating material 3 uses a heat insulating board (such as a high temperature resistant glass fiber heat insulating board, a high temperature resistant aluminum silicate ceramic fiber heat insulating board and the like) with certain machining performance, and holes are drilled at corresponding test positions, wherein the diameter of the drilled holes is slightly larger than that of the test cylinder 2, so that the test cylinder 2 can slide smoothly in the holes. The thickness of the insulating material 3 should be greater than the length of the test cylinder to ensure that the lower surface of the test cylinder 2 does not exchange heat with the environment during the experiment. A supporting sleeve 6 and a lower supporting plate 7 with a certain rigidity are respectively arranged at the outer part and the lower part of the heat insulation material 3 for preventing the heat insulation material 3 from being damaged in the transferring process. A guide post 4 and a guide sleeve 5 are arranged between the upper support plate 1 and the lower support plate 7, and an inner hole of the guide sleeve 5 is slightly larger than the outer diameter of the guide post 4, so that the guide post 4 can smoothly slide in the guide sleeve 5. The upper part of the guide post is fixed with the upper support plate 1, but not higher than the upper support plate 1. The lower part of the guide sleeve 5 is fixed with the lower support plate 7. Through holes 7-1 slightly smaller than the outer diameter of the guide sleeve 7 and larger than the outer diameter of the guide post 4 are formed in the lower support plate 7 at the position of the guide post 4, so that the guide post 4 can pass through the lower support plate 7 through the holes 7-1. The length of the guide sleeve 5 should be no greater than the length of the support sleeve. When the upper support plate 1 drives the test cylinder 2 to move upwards due to the length of the guide post 4, and the whole test cylinder 2 exposes the heat insulation material 3, part of the guide post 4 is still in the guide sleeve 4, so that the guide sleeve still has guiding and supporting functions. And a preformed hole 7-2 is processed on the lower supporting plate 7 at a position corresponding to the test cylinder and is used for installing a thermocouple, and the diameter of the preformed hole and the installation size of the thermocouple are required to be met.
The test cylinder of each test point should satisfy two conditions simultaneously:
1) The diameter of the test cylinder 2 meets the condition of an infinitely long cylinder for engineering heat exchange, namelyWherein lambda is the heat conductivity coefficient of the cylindrical material; r is the diameter of the test cylinder; h is a preset value of a convection heat transfer coefficient of the heat transfer surface at the end part of the test cylinder 2, and the range of the value of h is as follows: the predicted value h is 20-200 when the gas jet is impacted at a constant speed, and the predicted value h is 200-800 when the gas jet is impacted at a sonic speed or supersonic speed; taking 500-1000 of the estimated value h during water mist quenching; taking 1000-15000 as a predicted value h in forced convection of water; the estimated value h is estimated according to the empirical value under the special working condition; units: />
2) The length of the test cylinder 2 should be satisfied, and the temperature of the lower surface of the test cylinder 2 does not change with the temperature reduction of the upper surface during the whole test process.
Fitting a physical property parameter equation;
the method for fitting the physical property parameter equation comprises the following steps: inputting the following sentences in matlab, selecting the type and the precision of an equation according to requirements by using an automatically ejected cftool, and fitting to obtain a thermophysical parameter equation changing along with temperature:
clear；
Cftool；
x＝[A1,A2,···，An]；
y＝[C1,C2,···，Cn]；
wherein: A1-An and C1-Cn refer to different temperature values and corresponding thermophysical parameter values at the temperature values, respectively.
For example: the specific heat capacity of material 1cr18ni9ti as a function of temperature is shown in table 1, and the corresponding procedure is:
clear；
cftool；
x＝[300,400,500,600,700,800,900,1000,1100]；
y＝[481,509,529,546,561,576,591,605,619]；
selecting a polynominal fitting mode in a pop-up fitting tool box, wherein an equation obtained by fitting is
c p ＝-3.438 -10 t 4 +1.118 -6 t 3 -1.351 -3 t 2 +8.671 -1 t+315.2
Wherein t represents a temperature value
TABLE 1 specific heat capacity value of cr18ni9ti with temperature change
| Temperature (temperature) | 300 | 400 | 500 | 600 | 700 | 800 | 900 | 1000 | 1100 |
| c p (kg -1 K- 1 ) | 481 | 509 | 529 | 546 | 561 | 576 | 591 | 605 | 619 |
Step three, testing the emissivity of the material;
the temperature of the heat exchange surface is measured by using a thermal imager or an infrared thermometer, and the emissivity of different materials in different environments, different roughness and different temperatures also causes different measurement results, so that the emissivity of experimental materials is required to be obtained before research; the testing method comprises the following steps:
1) Setting a calibrated thermocouple in the heating furnace, and heating the heating furnace to a set temperature;
2) Placing the test material in a furnace and sufficiently heating the test material; the thermal insulation cover is used in the furnace to prevent heat dissipation, the thermal insulation cover is taken out and positioned, the thermal imager to be used is used for shooting and recording instantaneous temperature pictures, the emissivity value of the thermal imager is adjusted, the temperature measured by the thermal imager is consistent with the thermocouple temperature in the furnace, and the emissivity is the emissivity of the material at the temperature.
Step four, impact jet reinforced heat exchange experiment:
1) Before heating, the workpiece is placed at a test position, and the relative positions of the workpiece, the nozzle and the thermal imager are adjusted;
2) The upper supporting plate 1 and the testing cylinder 2 are moved upwards together, so that all parts of the testing cylinder 2 are higher than the heat insulation material 3 and are in direct contact with the heating environment, and a baffle is arranged between the upper supporting plate 1 and the supporting sleeve 6, so that the upper supporting plate does not slide down in the heating process;
3) The whole testing device is placed in a heating furnace to be heated to a preset temperature;
4) The furnace door is opened, the upper supporting plate 1 and the testing cylinder 2 are reset in the furnace, and a heat preservation cover is quickly covered in the furnace, so that the influence on experimental precision caused by heat dissipation in the transferring process is prevented;
5) After the testing device is placed at the corresponding position, the upper heat preservation cover is removed, the jet valve is quickly opened, and the surface temperature is recorded.
And fifthly, calculating the convection heat transfer coefficient.
Comprises the following steps:
1) Fitting the temperature values obtained from each test point along with the time to a polynomial equation to obtain the following form:
2) The temperature values of the nodes below the test cylinder over time were calculated using equation 2 as follows:
in the middle of
3) The following heat transfer coefficient of each test point with temperature is calculated by using the following equation 3:
4) When δτ and δx are selected, the following conditions are satisfied:
in the above calculation formulas 1 to 4, m denotes a polynomial order, i= … t denotes a time step, t denotes an end time of the measured temperature, n denotes a position node number,temperature value at time i for node with index n,/>Indicating the temperature of the upper surface of the test point,refers to the temperature of the lower end face of the test cylinder +.>Temperature of the previous position node of (c) at time i,/-, and (c)>For a virtual point that does not exist truly, δτ represents the time interval, δx represents the position interval of each node of the test cylinder, ρ is the temperature variationDensity fitting equation, c p And lambda is a fitting equation of the heat conductivity coefficient of the material along with the change of temperature. A node diagram of a discretization research method for enhancing heat exchange characteristics of impact jet is shown in FIG. 5.
The above examples are implemented on the premise of the technical scheme of the present invention, and detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the above examples. The methods used in the above examples are conventional methods unless otherwise specified.
Claims (6)
1. The discretization test method for the impact jet enhanced heat exchange characteristic is characterized by comprising the following steps of:
step one, designing a testing device, wherein the testing device comprises an upper supporting plate, a testing cylinder, a heat insulation material, a guide column and a lower supporting plate, the upper supporting plate contacts a workpiece, the testing cylinder is arranged below different positions of the heat exchange surface of the upper supporting plate, a testing object is scattered into testing points, and the lower surface of each testing cylinder and the testing cylinder are separated by the heat insulation material so as to block heat transfer between each testing point and between the testing point and the outside;
fitting a physical property parameter equation;
step three, testing the emissivity of the material;
step four, impact jet reinforced heat exchange experiment:
1) Before heating, the workpiece is placed at a test position, and the relative positions of the workpiece, the nozzle and the thermal imager are adjusted;
2) The upper supporting plate of the testing device is moved upwards together with the testing cylinder, so that all parts of the testing cylinder are higher than the heat insulation material and are in direct contact with the heating environment, and a baffle is arranged between the upper supporting plate and the supporting sleeve, so that the upper supporting plate does not slide off in the heating process;
3) The whole testing device is placed in a heating furnace to be heated to a preset temperature;
4) The furnace door is opened, the upper supporting plate and the test cylinder are reset in the furnace, and a heat preservation cover is quickly covered in the furnace to prevent the heat dissipation in the transferring process from affecting the experimental precision;
5) After the testing device is placed at the corresponding position, the upper heat preservation cover is removed, the jet valve is quickly opened, and the surface temperature is recorded;
step five, calculating a convection heat exchange coefficient;
the test cylinder of each test point should satisfy two conditions simultaneously:
1) The diameter of the test cylinder meets the condition of an infinitely long cylinder for engineering heat exchange, namelyWherein lambda is the heat conductivity coefficient of the cylindrical material; r is the diameter of the test cylinder; h is a preset value of a convection heat transfer coefficient of the heat transfer surface of the end part of the test cylinder, and the range of the value of h is as follows: the predicted value h is 20-200 when the gas jet is impacted at a constant speed, and the predicted value h is 200-800 when the gas jet is impacted at a sonic speed or supersonic speed; taking 500-1000 of the estimated value h during water mist quenching; taking 1000-15000 as a predicted value h in forced convection of water; the estimated value h is estimated according to the empirical value under the special working condition; units: />
2) The length of the test cylinder is required to meet the requirement, and the temperature of the lower surface of the test cylinder does not change along with the temperature reduction of the upper surface in the whole test process;
the convective heat transfer coefficient calculation in the fifth step comprises the following steps:
1) Fitting the temperature values obtained from each test point along with the time to a polynomial equation to obtain the following form:
2) The temperature values of the nodes below the test cylinder over time were calculated using equation (2) as shown below:
in the middle of
3) The following heat exchange coefficient of each test point along with the temperature is calculated by using the following equation (3):
4) When δτ and δx are selected, the following conditions are satisfied:
in the above calculation formulas (1) to (4), m denotes a polynomial order, i= … t denotes a time step, t denotes an end time of the measured temperature, n denotes a position node number,temperature value at time i for node with index n,/>Indicating the temperature of the upper surface of the test point,refers to the temperature of the lower end face of the test cylinder +.>Temperature of the previous position node of (c) at time i,/-, and (c)>For a virtual point that does not exist truly, δτ represents the time interval and δx represents the testThe position interval of each node of the cylinder, ρ is a density fitting equation with temperature change, c p And lambda is a fitting equation of the heat conductivity coefficient of the material along with the change of temperature.
2. The discretization test method for enhancing heat exchange characteristics by using impact jet according to claim 1, wherein in the second step, the method for fitting the physical property parameter equation comprises the following steps: inputting the following sentences in matlab, selecting the type and the precision of an equation according to requirements by using an automatically ejected cftool, and fitting to obtain a thermophysical parameter equation changing along with temperature:
clear；
Cftool；
x＝[A1,A2,···，An]；
y＝[C1,C2,···，Cn]；
wherein: A1-An and C1-Cn refer to different temperature values and corresponding thermophysical parameter values at the temperature values, respectively.
3. The discretization test method for enhancing heat exchange characteristics by impact jet according to claim 1, wherein in the third step, the thermal imager or the infrared thermometer is required to be used for measuring the temperature of the heat exchange surface, and the emissivity of different materials in different environments, different roughness and different temperatures also causes different measurement results, so that the emissivity of the experimental materials is required to be obtained before the study; the testing method comprises the following steps:
1) Setting a calibrated thermocouple in the heating furnace, and heating the heating furnace to a set temperature;
2) Placing the test material in a furnace and sufficiently heating the test material; the thermal insulation cover is used in the furnace to prevent heat dissipation, the thermal insulation cover is taken out and positioned, the thermal imager to be used is used for shooting and recording instantaneous temperature pictures, the emissivity value of the thermal imager is adjusted, the temperature measured by the thermal imager is consistent with the thermocouple temperature in the furnace, and the emissivity is the emissivity of the material at the temperature.
4. The test device used in the discretization test method for enhancing heat exchange characteristics by impact jet flow according to claim 1, which is characterized by comprising an upper support plate, a test cylinder, a connecting sheet, a heat insulation material, a guide post, a guide sleeve and a lower support plate, wherein the material of the upper support plate is consistent with that of the test cylinder, and round holes or square holes are processed at the test position, and the diameter of the holes or the side length of the square holes is larger than that of the test cylinder; the connecting sheet is connected with the test cylinder and the upper supporting plate, the appearance of the connecting sheet is consistent with the shape and the size of the hole at each test position on the upper supporting plate, the diameter of the inner hole is consistent with the diameter of the test cylinder, and the material is consistent with the test cylinder; the inner and outer sides of the connecting sheet are respectively welded with the testing cylinder and the upper supporting plate, and the upper surface of the connecting sheet is higher than the testing cylinder and the upper supporting plate before welding; after welding, integrally processing the upper supporting plate, the test cylinder and the connecting sheet to ensure that the upper plane of the whole device is the same plane and the same roughness; the gap between the test cylinder and the upper support plate hole is filled with heat insulation materials;
set up guide post and uide bushing between upper supporting plate and the lower backup pad, the guide post upper portion is fixed with the upper supporting plate, and the lower part and the lower backup pad of uide bushing are fixed, process the through-hole that is slightly less than the uide bushing external diameter and is greater than the guide post external diameter in the position of guide post in the lower backup pad, make the guide post pass the lower backup pad through the hole, process the preformed hole in the position corresponding with the test cylinder in the lower backup pad for install the thermocouple.
5. The test device used in the discretization test method for enhancing heat exchange characteristics by impact jet according to claim 4, wherein the heat insulation material is a heat insulation board with mechanical processing property, and holes are drilled at corresponding test positions, and the diameter of the drilled holes is slightly larger than that of the test cylinders, so that the test cylinders can slide smoothly in the holes.
6. The test device for use in a discretized test method for enhanced heat transfer characteristics by impingement jet according to claim 4, wherein the thickness of the insulating material is greater than the length of the test cylinder to ensure that the lower surface of the test cylinder does not exchange heat with the environment during the test.
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Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101393150A (en) * | 2008-10-16 | 2009-03-25 | 大连理工大学 | Solid interface contact heat exchange coefficient measurement method and apparatus based on transient method |
| CN102507636A (en) * | 2011-09-30 | 2012-06-20 | 中国科学院金属研究所 | Method for measuring interfacial heat transfer coefficient of rapid cooling process of steel |
| CN104267070A (en) * | 2014-10-29 | 2015-01-07 | 哈尔滨工业大学 | Device for measuring heat conductivity coefficient of liquid on basis of transient plane source method |
| CN106226351A (en) * | 2016-09-23 | 2016-12-14 | 西安交通大学 | A kind of thin-wall circular tube material thermal conductivity computational methods |
| CN106383944A (en) * | 2016-09-12 | 2017-02-08 | 广东电网有限责任公司电力科学研究院 | Simulation method and device of combustion characteristic generation numerical value of utility boiler pulverized coal under variable over fire air volume |
| CN106442606A (en) * | 2016-09-28 | 2017-02-22 | 华中科技大学 | Method and device for recognizing mercury forms |
| CN106568802A (en) * | 2016-10-28 | 2017-04-19 | 北京航天长征飞行器研究所 | Free jet type supersonic flue gas flow enthalpy value steady state measurement apparatus |
| CN107271480A (en) * | 2017-07-04 | 2017-10-20 | 清华大学 | The experiment test system and control method of convection transfer rate under human motion state |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2441879A1 (en) * | 2001-03-22 | 2002-10-03 | University Of Maryland | Sensor probe for measuring temperature and liquid volumetric fraction of a liquid droplet laden hot gas and method of using same |
| US7010921B2 (en) * | 2004-06-01 | 2006-03-14 | General Electric Company | Method and apparatus for cooling combustor liner and transition piece of a gas turbine |
-
2021
- 2021-01-27 CN CN202110113420.0A patent/CN112800607B/en active Active
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101393150A (en) * | 2008-10-16 | 2009-03-25 | 大连理工大学 | Solid interface contact heat exchange coefficient measurement method and apparatus based on transient method |
| CN102507636A (en) * | 2011-09-30 | 2012-06-20 | 中国科学院金属研究所 | Method for measuring interfacial heat transfer coefficient of rapid cooling process of steel |
| CN104267070A (en) * | 2014-10-29 | 2015-01-07 | 哈尔滨工业大学 | Device for measuring heat conductivity coefficient of liquid on basis of transient plane source method |
| CN106383944A (en) * | 2016-09-12 | 2017-02-08 | 广东电网有限责任公司电力科学研究院 | Simulation method and device of combustion characteristic generation numerical value of utility boiler pulverized coal under variable over fire air volume |
| CN106226351A (en) * | 2016-09-23 | 2016-12-14 | 西安交通大学 | A kind of thin-wall circular tube material thermal conductivity computational methods |
| CN106442606A (en) * | 2016-09-28 | 2017-02-22 | 华中科技大学 | Method and device for recognizing mercury forms |
| CN106568802A (en) * | 2016-10-28 | 2017-04-19 | 北京航天长征飞行器研究所 | Free jet type supersonic flue gas flow enthalpy value steady state measurement apparatus |
| CN107271480A (en) * | 2017-07-04 | 2017-10-20 | 清华大学 | The experiment test system and control method of convection transfer rate under human motion state |
Non-Patent Citations (3)
| Title |
|---|
| Heat transfer characteristics of a rotating cylinder with a lateral air impinging jet;Tzer-Ming Jeng等;《ELSEVIER》;235-249 * |
| Investigation of the transient heat transfer to a supersonic air jet impinging on a high-temperature plate based on a discrimination-experiment method;Ming-Xin Gao等;《plos one》;1-27 * |
| 圆柱锂电池表面自然对流换热系数仿真估算;丁亚军 等;《电源技术》;1256-1259 * |
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