CN113536515A - Equivalent conversion method and system for thermal design parameters of high altitude - Google Patents
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Abstract
The invention provides a thermal design parameter equivalent conversion method and a thermal design parameter equivalent conversion system aiming at high altitude, the method firstly obtains the thermal design parameters of a forced air cooling system of a power electronic device under the condition of plain altitude as reference thermal design parameters, then adopts corresponding equivalent conversion schemes to respectively analyze and calculate based on the reference thermal design parameters, and determines the target thermal design parameters of the forced air cooling system under the condition of high altitude, wherein the target thermal design parameters comprise at least one of the following parameters: the fan pressure loss, the fan power, the fan air volume and the table top temperature rise of the forced air cooling system of the power electronic device. By adopting the calculation scheme, aiming at the working characteristics of the forced air cooling system of the power electronic device, a corresponding analysis calculation model is established based on the basic principle of thermodynamics, and the reliable thermal design parameters of the system under the influence of altitude height are determined through concise calculation, so that a reference basis is provided for the heat dissipation design and reliability evaluation of the power electronic device under the high altitude environment.
Description
Technical Field
The invention relates to the technical field of thermal design parameter calculation, in particular to a thermal design parameter equivalent conversion method and system for high altitude.
Background
The heat dissipation of forced air cooling systems for power electronics devices includes conduction, convection and radiation, wherein the effect of radiation is usually neglected because it is a rather small proportion. The forced air cooling system of the power electronic device mainly comprises a fan, an air duct, a radiator and an air filter, the structural schematic diagram is shown in figure 1, cooling air enters from the air filter, and hot air is discharged to the outside of a system cabinet body by the fan after flowing through the radiator and the air duct. The main heat source in the system is a power device (such as a semiconductor power device), the heat of the power electronic power device is transferred to the surface of a radiator fin in a heat conduction mode, then heat energy is transferred to cooling air through convective heat transfer, the heat is dissipated to the surrounding environment through a fan, the performance of the fan, the flow resistance of the system and the heat exchange efficiency of the cooling air can be influenced by the change of the altitude, and therefore the heat dissipation performance of the system is influenced.
The following methods are generally used for thermal design of high-altitude power electronic devices: 1. neglecting the influence of altitude height on heat dissipation, and adopting a conventional zero altitude thermal design method; 2. considering that the altitude and the heat design are in a linear relation, and introducing a simple linear relation to realize the heat design and operation of the high altitude; 3. reference is made to relevant national or industry standards. The method 1 and the method 2 will have a great error in the calculation result, and the related national standard is set earlier, so that the design requirements of low cost, high stability and strong heat dissipation capability of the existing power electronic device cannot be well met.
Disclosure of Invention
To solve the above problems, the present invention provides a thermal design parameter equivalent conversion method for high altitude, which in one embodiment comprises:
step S1, obtaining thermal design parameters of the power electronic device forced air cooling system under plain altitude conditions as reference thermal design parameters, wherein the reference thermal design parameters comprise: the environmental air density, the table temperature rise, the fan pressure loss and the fan power of the forced air cooling system of the power electronic device;
step S2, analyzing and calculating the reference thermal design parameters respectively by adopting corresponding equivalent conversion schemes, and further determining target thermal design parameters of the power electronic device forced air cooling system under the high altitude condition, wherein the target thermal design parameters comprise at least one of the following parameters: the fan pressure loss, the fan power, the fan air volume and the table top temperature rise of the forced air cooling system of the power electronic device.
In one embodiment, in the step S2, the fan pressure loss of the power electronic device forced air cooling system under the high altitude condition is determined by:
according to the thermodynamic principle, the fan pressure loss of the forced air cooling system of the power electronic device under the plain altitude condition and the correlation between the ambient air density and the altitude parameter are analyzed and calculated to determine the fan pressure loss of the system under the high altitude condition.
In one embodiment, the following mathematical model is further constructed according to the fan pressure loss of the system under plain altitude conditions and the ambient air density to calculate the fan pressure loss of the system under high altitude conditions:
in the formula, paltThe pressure loss, rho, of the fan under high altitude conditionsaltAmbient air density at high altitude; p is a radical of0The pressure loss of the fan under plain elevation is obtained; rho0Is the air density at plain altitude; n isaltIs the fan speed n under the condition of high altitude0The rotating speed of the fan under plain elevation.
In one embodiment, in step S2, the following mathematical model is constructed by referring to the fan power in the thermal design parameters according to the fan power similarity law to calculate the fan power of the power electronic device forced air cooling system under the high altitude condition:
in the formula, PaltIs the fan power, rho, at high altitudealtAir density at high altitude; p0The power of a fan under plain elevation; rho0Is the ambient air density at plain altitude; n isaltIs the fan speed n under the condition of high altitude0The rotating speed of the fan under plain elevation.
In one embodiment, in step S2, the fan volume of the power electronics forced air cooling system at high altitude is determined by:
acquiring the fan air volume of the forced air cooling system of the power electronic device under the high-altitude condition based on the obtained fan pressure loss according to the relevance of the fan pressure loss and the fan air volume;
or
And acquiring the fan air volume of the forced air cooling system of the power electronic device under the high-altitude condition based on the acquired fan power according to the relevance between the fan power and the fan air volume.
In one embodiment, in step S2, the table top temperature rise of the power electronics forced air cooling system at high altitude is determined by:
a table top temperature rise-Reynolds number curve of the radiator is obtained through a plain altitude temperature rise test, the Reynolds number under the high altitude condition is calculated, and the table top temperature rise under the high altitude condition is determined according to the Reynolds number obtained through calculation and the temperature rise-Reynolds number curve.
Further, the reynolds number under the high-altitude condition is calculated based on the acquired geometric dimension parameter of the radiator, the operation air volume and the air density corresponding to the altitude parameter.
In an optional embodiment, the method further comprises the operations of:
and designing a test tool, controlling the altitude in a high-altitude environment box to be a single environment variable, introducing the obtained target thermal design parameter to perform a simulation test, and evaluating the accuracy of the target thermal design parameter serving as an equivalent conversion result according to a test result.
In accordance with another aspect of any one or more of the embodiments described above, the present invention provides a system for equivalent scaling of thermal design parameters for high altitude, the system comprising:
the calculation parameter acquisition module is used for acquiring thermal design parameters of a forced air cooling system of the power electronic device under plain altitude conditions as reference thermal design parameters, wherein the reference thermal design parameters comprise: the environmental air density, the table temperature rise, the fan pressure loss and the fan power of the forced air cooling system of the power electronic device;
the equivalent conversion module is used for analyzing and calculating by adopting a corresponding equivalent conversion scheme based on each reference thermal design parameter, and further determining a target thermal design parameter of the forced air cooling system of the power electronic device under the high altitude condition, wherein the target thermal design parameter comprises at least one of the following parameters: the fan pressure loss, the fan power, the fan air volume and the table top temperature rise of the forced air cooling system of the power electronic device.
In one embodiment, the equivalence scaling module determines fan pressure loss for a power electronics forced air cooling system at high altitude conditions by:
according to the thermodynamic principle, the fan pressure loss of the power electronic device forced air cooling system under the plain altitude condition and the correlation between the ambient air density and the altitude parameter are analyzed, and the following mathematical model is constructed to calculate the fan pressure loss of the power electronic device forced air cooling system under the high altitude condition:
in the formula, paltThe pressure loss, rho, of the fan under high altitude conditionsaltAmbient air density at high altitude; p is a radical of0The pressure loss of the fan under plain elevation is obtained; rho0Is the air density at plain altitude; n isaltIs the fan speed n under the condition of high altitude0The rotating speed of the fan under plain elevation.
Compared with the closest prior art, the invention also has the following beneficial effects:
the invention provides a high-altitude thermal design parameter equivalent conversion method and system, which are used for respectively analyzing and calculating reference thermal design parameters based on altitude of each plateau by adopting a corresponding equivalent conversion scheme to determine target thermal design parameters of a forced air cooling system under a high-altitude condition. By adopting the calculation scheme, the altitude variable parameter is introduced based on the basic principle of thermodynamics aiming at the working characteristics of the forced air cooling system of the power electronic device, the corresponding analysis calculation model is established, the thermal design parameter of the system under the influence of the altitude is determined, the calculation process is simple and clear, the reliability of the calculation result of the thermal design parameter is guaranteed, a reference basis is provided for the heat dissipation design and reliability evaluation of the power electronic device under the high-altitude environment, and meanwhile, the stable operation of the power electronic device in the high-altitude area is greatly promoted.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
fig. 1 is a schematic structural diagram of a forced air cooling system of a power electronic device according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a thermal resistance network between a heat source from a semiconductor device chip to an external environment in a forced air cooling system of a power electronic device according to an embodiment of the present invention;
FIG. 3 is a flow chart illustrating an equivalent scaling method for thermal design parameters at high altitude according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a heat sink model commonly used in a power electronic device according to an embodiment of the invention;
FIG. 5 is a temperature rise-Re number relationship curve of a heat sink table for a high altitude thermal design parameter equivalent conversion method in an embodiment of the present invention;
FIG. 6 is a schematic diagram of the operating point of the forced air cooling system in the mixed fluid state according to the embodiment of the present invention;
FIG. 7 is a schematic flow chart of an equivalent scaling method for high altitude thermal design parameters according to another embodiment of the present invention;
FIG. 8 is a schematic structural diagram of an equivalent scaling system for high altitude thermal design parameters according to another embodiment of the present invention;
FIG. 9 is a flow chart of the operational principles of the thermal design parameter equivalent scaling system for high altitude in an embodiment of the present invention;
FIG. 10 is a schematic diagram of a user interface of an equivalent scaling system for thermal design parameters at high altitude in an embodiment of the present invention.
Detailed Description
The following detailed description will be provided for the embodiments of the present invention with reference to the accompanying drawings and examples, so that the practitioner of the present invention can fully understand how to apply the technical means to solve the technical problems, achieve the technical effects, and implement the present invention according to the implementation procedures. It should be noted that, unless otherwise conflicting, the embodiments and features of the embodiments of the present invention may be combined with each other, and the technical solutions formed are all within the scope of the present invention.
The following methods are generally used for thermal design of high-altitude power electronic devices: 1. neglecting the influence of altitude height on the heat dissipation of the wind turbine; 2. linear relationship to altitude is considered; 3. reference is made to relevant national standards, industry standards. The former two methods will make the calculation result have a great error, and the related national standard is set too early, so that the design requirements of low cost, high stability and strong heat dissipation capability of the current power electronic device cannot be met.
The heat dissipation of the forced air cooling system (hereinafter referred to as system) of the power electronic device mainly includes conduction, convection and radiation, wherein the proportion of radiation is small, and the influence thereof is generally ignored. The forced air cooling system of the power electronic device mainly comprises a fan, an air channel, a radiator, an air filter and the like, the structural schematic diagram of the forced air cooling system is shown in figure 1, cooling air enters from the air filter, and hot air is discharged out of a cabinet body by a fan of the fan after flowing through the radiator and the air channel. The main heat source in the system is a power device, the heat of the power electronic power device is transferred to the surface of the radiator fin in a heat conduction mode, then heat energy is transferred to cooling air through convection heat transfer, the heat is dissipated to the surrounding environment through a fan, the change of the altitude can affect the performance of the fan, the flow resistance of the system and the heat exchange efficiency of the cooling air, and therefore the heat dissipation performance of the system is affected.
In order to solve the problems, the invention provides an equivalent conversion method and system for thermal design parameters of a high altitude.
The technical scheme of the invention aims at the working characteristics of the forced air cooling system of the power electronic device, introduces altitude variable parameters based on the basic principle of thermodynamics, establishes a mathematical model of the forced air cooling system, and researches the influence of the altitude on the flow field and the heat transfer performance of the system during the operation of the forced air cooling system. Meanwhile, a test tool is designed, the altitude is controlled to be a single environment variable in a high-altitude environment box to carry out simulation test, and the accuracy of a mathematical modeling method and a conclusion of the forced air cooling system is verified through a test result.
In order to conveniently research a theoretical mathematical model of the altitude height to the heat resistance of the radiator, the following assumptions are made: (1) a uniform heat source is arranged on the radiator substrate, and the influence of heat source arrangement on the heat diffusion resistance of the radiator is ignored; (2) the temperature of the air environment is 20 ℃; (3) neglecting the influence of radiation heat exchange of the radiator; (4) the fins are straight ribs with equal sections. The thermal resistance network between the heat source from the semiconductor device chip to the external environment is shown in FIG. 2, where RjcRepresenting the thermal resistance between the semiconductor device chip and the package substrate housing; rchRepresenting the thermal resistance between the device package baseboard housing to the heat sink baseboard; rbRepresents the thermal resistance of the heat sink substrate in the thickness direction; rrRepresenting the thermal resistance from the root of the radiator substrate to the surrounding environment; rfRepresenting the thermal resistance of the radiator fins to the surrounding environment; t isjIndicating the temperature of the device; t iscIndicating the device case temperature; t ishRepresents the radiator floor temperature; t isbRepresenting the temperature after conduction through the heat sink substrate; t isaIndicating the outside air ambient temperature.
Various embodiments of the present invention will be described below with reference to the accompanying drawings.
Example one
Fig. 3 is a schematic flow chart of an equivalent conversion method for thermal design parameters at high altitude according to an embodiment of the present invention, and as can be seen from fig. 3, the method includes the following steps.
Step S110, acquiring thermal design parameters of a forced air cooling system of the power electronic device under plain altitude conditions as reference thermal design parameters, wherein the reference thermal design parameters comprise: the environmental air density, the table temperature rise, the fan pressure loss and the fan power of the forced air cooling system of the power electronic device;
in this step, the process of obtaining parameters in actual application also obtains: the air quantity of the radiator, the pressure drop of the radiator, the geometric size parameters of the radiator and the like; the method is used for combining the Reynolds number corresponding to the radiator in the environment air density calculation system to provide data support for calculating the thermal design parameters of the forced air cooling system under the altitude condition.
Step S120, analyzing and calculating by adopting a corresponding equivalent conversion scheme based on each reference thermal design parameter, and determining a target thermal design parameter of the forced air cooling system of the power electronic device under the condition of high altitude, wherein the target thermal design parameter comprises at least one of the following parameters: the fan pressure loss, the fan power, the fan air volume and the table top temperature rise of the forced air cooling system of the power electronic device.
Further, in one embodiment, in the step S120, the fan pressure loss of the forced air cooling system of the power electronic device under the high altitude condition is determined by:
according to the thermodynamic principle, the fan pressure loss of the forced air cooling system of the power electronic device under the plain altitude condition and the correlation between the ambient air density and the altitude parameter are analyzed and calculated to determine the fan pressure loss of the system under the high altitude condition.
Combining with actual conditions, the thermophysical parameters of the air comprise: atmospheric pressure, air density, specific heat at constant pressure, thermal conductivity, dynamic viscosity, prandtl number, and the like. As the altitude increases, the thermophysical parameters of the air change accordingly, and in particular, as the altitude increases, the air density decreases.
Based on the above analysis, the fan pressure loss (also called full pressure) of the forced air cooling system is proportional to the air density and the square of the rotating speed, the air density decreases with the increase of the altitude, and the pressure of the cooling fan decreases, which can be known from the fan pressure similarity law, specifically, in practical application, the following mathematical model is constructed according to the fan pressure loss of the system under the plain altitude condition and the ambient air density, so as to calculate the fan pressure loss of the system under the high altitude condition:
in the formula, paltThe pressure loss, rho, of the fan under high altitude conditionsaltAmbient air density at high altitude; p is a radical of0The pressure loss of the fan under plain elevation is obtained; rho0Is the air density at plain altitude; n isaltIs the fan speed n under the condition of high altitude0The rotating speed of the fan under plain elevation.
Further, according to the fan power similarity law (or power similarity relation), the power of two similar fans is defined according to dimensionless performance parameters, and specifically, according to the fan power similarity law, the following mathematical model is constructed by using the fan power in the reference thermal design parameters to calculate the fan power of the power electronic device forced air cooling system under the condition of high altitude:
in the formula, PaltIs the fan power, rho, at high altitudealtAir density at high altitude; p0The power of a fan under plain elevation; rho0Is the ambient air density at plain altitude; n isaltIs the fan speed n under the condition of high altitude0The rotating speed of the fan under plain elevation.
In a fan of a forced air cooling system, the total pressure, i.e., the resistance, of the fan is the sum of the static pressure and the dynamic pressure, and the larger the resistance, the smaller the air volume. The power is power, and the larger the power is, the larger the air volume is. When the total pressure is constant, the larger the power is, the larger the air volume is. Based on the method, the fan air volume of the forced air cooling system of the power electronic device under the high altitude condition is determined through the following operations:
acquiring the fan air volume of the forced air cooling system of the power electronic device under the high-altitude condition based on the obtained fan pressure loss according to the relevance of the fan pressure loss and the fan air volume; or
And acquiring the fan air volume of the forced air cooling system of the power electronic device under the high-altitude condition based on the acquired fan power according to the relevance between the fan power and the fan air volume.
In general, the calculation of the fan power is performed by those skilled in the art according to the following principles: the pressure ratio is equal to the square of the air volume ratio, which is equal to the cube of the power ratio.
Further, the heat sink is one of the key components in the forced air cooling system, and the variation of the heat performance of the heat sink directly affects the working temperature saving of the high power semiconductor device, so it is necessary to study the quantitative influence relationship of the high altitude on the heat performance parameters of the heat sink. FIG. 4 is a typical heat sink model of the power electronic device, wherein W is the width of the heat sink, H is the total height of the heat sink, L is the length of the heat sink, HfThe height of the radiator fins is shown, t is the thickness of the radiator fins, d is the gaps among the radiator fins, the total number of the fins of the radiator is n, and the total air quantity flowing through the radiator is Q.
When the head-on wind speed of the radiator is fixed, the Re (Reynolds number) number of the radiator is in direct proportion to the air density, and the Nu number and the heat exchange coefficient are functions related to the Re number. Wherein Re represents a Reynolds number, a dimensionless constant characterizing the flow of a fluid; nu is Nussel number, a dimensionless constant, and represents the ratio of convective heat and conductive heat in the process of fluid heat transfer
In practical engineering application, under the influence of factors such as the size, the position, the number and the like of heat sources, the internal part of the radiator also has thermal diffusion resistance caused by heat conduction, and the thermal diffusion resistance is only related to the geometrical characteristics of the radiator. The total thermal resistance of the heat sink is therefore related only to its Re number, regardless of the placement of the heat source on the heat sink's mesa. According to the derivation process of the thermal resistance theory of the radiator, the temperature rise of the table top of the radiator with different altitudes is also a function related to the number of Re under the condition of certain power of a heat source, and on the basis of the temperature rise-Re number curve of the radiator, the temperature rise-Re number curve of the radiator with different altitudes is obtained through a plain altitude temperature rise test, then the Re number of the radiator with different altitudes is calculated, and the temperature rise condition of the high altitude is converted by using a temperature rise function relational expression, so that the calculation strategy is reliable. The Reynolds number of the radiator under the high-altitude condition is calculated according to the geometric dimension parameter of the radiator, the operation air quantity and the air density corresponding to the altitude parameter.
Therefore, the present invention has: the table top temperature rise of the forced air cooling system of the power electronic device under the high altitude condition is determined through the following operations:
a table top temperature rise-Reynolds number curve of the radiator is obtained through a plain altitude temperature rise test, the Reynolds number under the high altitude condition is calculated, and the table top temperature rise under the high altitude condition is determined according to the Reynolds number obtained through calculation and the temperature rise-Reynolds number curve. The relationship curve of temperature rise-Re number of the radiator is fitted according to experimental data, as shown in FIG. 5, in the figure, the abscissa is Reynolds number Re, and the ordinate is temperature rise (K).
Specifically, the reynolds number under the high-altitude condition is determined based on the obtained geometric size parameter of the radiator, the operation air volume and the air density calculation corresponding to the altitude parameter.
As the air density decreases with increasing altitude, the pressure of the cooling fan in the system decreases, but the volumetric flow at the same speed remains the same. The flow resistance changes of the air filter, the radiator, the air duct and the fan at each stage are comprehensively analyzed, and the change rule of the working point of the system under different flowing states can be obtained. The forced air cooling system of the high-power electronic device is not only a simple turbulent flow as the flow state of the system at plain altitude any more along with the rise of high altitude, but also belongs to a mixed flow state which is generally between a laminar flow and a turbulent flow and is more inclined to the turbulent flow under the condition of high altitude. Elevation causes the system operating point to move forward, the volume flow rate is slightly reduced, and turbulence system consideration is generally made in the engineering application process. The schematic diagram of the operating point of the forced air cooling system in the mixed fluid state is shown in fig. 6. When the cooling medium of the system is in a laminar flow state, the volume flow value corresponding to the system working point under the high-altitude condition is reduced; when the system cooling medium is in a turbulent flow state, the volume flow value corresponding to the system working point is unchanged under the condition of high altitude.
The technical scheme of the invention provides a thermal design parameter calculation method considering the influence of altitude factors, which is applied to a forced air cooling system of a power electronic device, and comprises physical quantities such as temperature rise of a table board of a radiator, air quantity of a fan, pressure loss of the fan, power of the fan and the like, the calculation efficiency is high, a reliable calculation result is obtained through simple calculation steps, and the efficient and stable operation of the power electronic device in a high-altitude area is facilitated.
Example two
The technical scheme of the invention aims at the working characteristics of the forced air cooling system of the power electronic device, introduces altitude variable parameters based on the basic principle of thermodynamics, establishes a mathematical model of the forced air cooling system, and researches the influence of the altitude on the flow field and the heat transfer performance of the system during the operation of the forced air cooling system.
The equivalent conversion method of the thermal design parameters aiming at the high altitude provided by the invention comprises the following steps:
step S110, acquiring thermal design parameters of a forced air cooling system of the power electronic device under plain altitude conditions as reference thermal design parameters, wherein the reference thermal design parameters comprise: the electric power electronic device forces the ambient air density, table top temperature rise, fan pressure loss and fan power of the air cooling system.
In this step, the process of obtaining parameters in actual application also obtains: the air quantity of the radiator, the pressure drop of the radiator, the geometric size parameters of the radiator and the like; the method is used for combining the Reynolds number corresponding to the radiator in the environment air density calculation system to provide data support for calculating the thermal design parameters of the forced air cooling system under the altitude condition.
Step S120, analyzing and calculating by adopting a corresponding equivalent conversion scheme based on each reference thermal design parameter, and further determining a target thermal design parameter of the forced air cooling system of the power electronic device under the condition of high altitude, wherein the target thermal design parameter comprises at least one of the following parameters: the fan pressure loss, the fan power, the fan air volume and the table top temperature rise of the forced air cooling system of the power electronic device.
In order to ensure the reliability of the equivalent conversion method, the invention also designs a test tool, controls the altitude in the high-altitude environment box to be a single environment variable for simulation test, and the test result verifies the accuracy of the mathematical modeling method and the conclusion of the forced air cooling system, specifically, fig. 7 shows a flow schematic diagram of the equivalent conversion method for the thermal design parameters of the high altitude in another embodiment of the invention, as shown in fig. 7, the method further comprises the following operations:
and designing a test tool, controlling the altitude in a high-altitude environment box to be a single environment variable, introducing the obtained target thermal design parameter to perform a simulation test, and evaluating the accuracy of the target thermal design parameter serving as an equivalent conversion result according to a test result. The test result verifies the feasibility of mathematical modeling of the forced air cooling system and the accuracy of the conclusion of the equivalent conversion method of the thermal design parameters.
EXAMPLE III
Based on other aspects of one or more embodiments of the present invention, in order to facilitate a user to obtain a calculation result, the present invention further provides a thermal design parameter equivalent conversion system for high altitude, which is configured to perform the method and steps in any one or more embodiments of the present invention, and fig. 8 illustrates a schematic structural diagram of the thermal design parameter equivalent conversion system for high altitude in an embodiment of the present invention, as shown in fig. 8, where the system of the embodiment includes:
the calculation parameter acquisition module is used for acquiring thermal design parameters of a forced air cooling system of the power electronic device under plain altitude conditions as reference thermal design parameters, wherein the reference thermal design parameters comprise: the environmental air density, the table temperature rise, the fan pressure loss and the fan power of the forced air cooling system of the power electronic device;
in practical application, the calculation parameter obtaining module further obtains: the air quantity of the radiator, the pressure drop of the radiator, the geometric size parameters of the radiator and the like; the method is used for combining the Reynolds number corresponding to the radiator in the environment air density calculation system to provide data support for calculating the thermal design parameters of the forced air cooling system under the altitude condition.
The equivalent conversion module is used for analyzing and calculating by adopting a corresponding equivalent conversion scheme based on each reference thermal design parameter so as to determine a target thermal design parameter of the forced air cooling system of the power electronic device under the condition of high altitude, wherein the target thermal design parameter comprises at least one of the following parameters: the fan pressure loss, the fan power, the fan air volume and the table top temperature rise of the forced air cooling system of the power electronic device.
The equivalent conversion module determines the fan pressure loss of the forced air cooling system of the power electronic device under the high altitude condition through the following operations:
according to the thermodynamic principle, the fan pressure loss of the power electronic device forced air cooling system under the plain altitude condition is analyzed in combination with the correlation between the environmental air density and the altitude parameter, and the following mathematical model is constructed to calculate the fan pressure loss of the power electronic device forced air cooling system under the high altitude condition:
in the formula, paltThe pressure loss, rho, of the fan under high altitude conditionsaltAmbient air density at high altitude; p is a radical of0The pressure loss of the fan under plain elevation is obtained; rho0Is the air density at plain altitude; n isaltIs the fan speed n under the condition of high altitude0The rotating speed of the fan under plain elevation. In practical applications, the tool software designed by the system according to the embodiment of the present invention may be made by other computer languages, such as C, C #, C + +, etc., and the schematic operation diagram of the system is shown in fig. 9. Specifically, in the process of realizing calculation, a user opens an application program corresponding to the system, relevant parameters of zero altitude including environmental parameters under the zero altitude condition and thermal design parameters of the forced air cooling system are input according to calculation requirements, then fitting calculation is carried out on the basis of the input parameters by the application program, a fitting curve among the relevant parameters is obtained, further the environmental parameters of the high altitude condition to be calculated and other relevant intermediate calculation parameters are input, further the thermal design parameters corresponding to the high altitude environmental parameters are determined according to the parameters of the high altitude condition on the basis of the obtained fitting curve, the obtained thermal design parameters are displayed to the user, calculation is completed, and the user confirms that the application program is withdrawn.
In an optional embodiment, after determining the thermal design parameters corresponding to the high-altitude environment parameters, the system displays the correlation curves corresponding to the parameters in the calculation process, such as a reynolds number curve, a pressure loss curve, a reynolds number/temperature rise curve, and the like.
Further, fig. 10 shows a schematic display interface diagram of the equivalent conversion system for the thermal design parameters at high altitude in this embodiment, as shown in fig. 10, the software mainly divides the data import module and the calculation module, and the user implements the following calculation process according to the calculation requirement: 1. inputting relevant parameters of heat dissipation design of a forced air cooling system under plain altitude, wherein the relevant parameters comprise air quantity of a radiator, ambient temperature, table temperature rise, pressure drop of the radiator, geometric size parameters of the radiator and the like; 2. fitting and calculating the relationship between Reynolds number (Re number) and table temperature rise and the relationship between air density and blower pressure loss; 3. and calculating the Reynolds number of the radiator under corresponding conditions according to the geometric dimension and the operation air volume of the radiator in combination with the air density corresponding to the required altitude parameter, and obtaining each heat dissipation design parameter under high altitude based on the technical scheme of the invention. The computing software designed by the invention can effectively simplify the computing process of the user.
Specifically, the equivalent conversion module of the present invention is further configured to: according to the fan power similarity law, the following mathematical model is constructed by using the fan power in the reference thermal design parameters to calculate the fan power of the forced air cooling system of the power electronic device under the condition of high altitude:
in the formula, PaltIs the fan power, rho, at high altitudealtAir density at high altitude; p0The power of a fan under plain elevation; rho0Is the ambient air density at plain altitude; n isaltIs the fan speed n under the condition of high altitude0The rotating speed of the fan under plain elevation.
In one embodiment, the equivalent conversion module of the present invention determines the fan air volume of the forced air cooling system of the power electronic device under high altitude conditions by:
acquiring the fan air volume of the forced air cooling system of the power electronic device under the high-altitude condition based on the obtained fan pressure loss according to the relevance of the fan pressure loss and the fan air volume; or
And acquiring the fan air volume of the forced air cooling system of the power electronic device under the high-altitude condition based on the acquired fan power according to the relevance between the fan power and the fan air volume.
In one embodiment, the equivalent scaling module of the present invention determines the table temperature rise of a forced air cooling system of a power electronic device at high altitude by:
a table top temperature rise-Reynolds number curve of the radiator is obtained through a plain altitude temperature rise test, the Reynolds number under the high altitude condition is calculated, and the table top temperature rise under the high altitude condition is determined according to the Reynolds number obtained through calculation and the temperature rise-Reynolds number curve.
Wherein the Reynolds number under the high altitude condition is determined based on the air density under the high altitude condition according to a functional relationship between the Reynolds number and the air density.
In an optional embodiment, the equivalent conversion system for high-altitude thermal design parameters further includes a result verification module, which is used for designing a test fixture, controlling the altitude in the high-altitude environment box to be a single environment variable, introducing the obtained target thermal design parameters to perform a simulation test, and evaluating the accuracy of the target thermal design parameters as the equivalent conversion results according to the test results. The test result verifies the feasibility of mathematical modeling of the forced air cooling system and the accuracy of the conclusion of the equivalent conversion method of the thermal design parameters.
In the equivalent conversion system for the thermal design parameters of the high altitude provided by the embodiment of the invention, each module or unit structure can be independently operated or operated in a combined manner according to actual requirements, so as to realize corresponding technical effects.
It is to be understood that the disclosed embodiments of the invention are not limited to the particular structures, process steps, or materials disclosed herein but are extended to equivalents thereof as would be understood by those ordinarily skilled in the relevant arts. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.
Reference in the specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, appearances of the phrase "an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment.
Although the embodiments of the present invention have been described above, the above descriptions are only for the convenience of understanding the present invention, and are not intended to limit the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A method of equivalent scaling of thermal design parameters for high altitude, the method comprising:
step S1, obtaining thermal design parameters of the power electronic device forced air cooling system under plain altitude conditions as reference thermal design parameters, wherein the reference thermal design parameters comprise: the environmental air density, the table temperature rise, the fan pressure loss and the fan power of the forced air cooling system of the power electronic device;
step S2, analyzing and calculating the reference thermal design parameters respectively by adopting corresponding equivalent conversion schemes, and further determining target thermal design parameters of the power electronic device forced air cooling system under the high altitude condition, wherein the target thermal design parameters comprise at least one of the following parameters: the fan pressure loss, the fan power, the fan air volume and the table top temperature rise of the forced air cooling system of the power electronic device.
2. The method of claim 1, wherein in step S2, the fan pressure loss of the power electronics forced air cooling system under high altitude conditions is determined by:
according to the thermodynamic principle, the fan pressure loss of the forced air cooling system of the power electronic device under the plain altitude condition and the correlation between the ambient air density and the altitude parameter are analyzed and calculated to determine the fan pressure loss of the system under the high altitude condition.
3. The method of claim 2, wherein the following mathematical model is constructed from the fan pressure loss of the system at plain altitude and the ambient air density to calculate the fan pressure loss of the system at high altitude:
in the formula, paltThe pressure loss, rho, of the fan under high altitude conditionsaltAmbient air density at high altitude; p is a radical of0The pressure loss of the fan under plain elevation is obtained; rho0Is the air density at plain altitude; n isaltIs the fan speed n under the condition of high altitude0The rotating speed of the fan under plain elevation.
4. The method according to claim 1 or 2, wherein in step S2, the following mathematical model is constructed by using the fan power in the reference thermal design parameter according to the fan power similarity law to calculate the fan power of the power electronic device forced air cooling system under the high altitude condition:
in the formula, PaltIs the fan power, rho, at high altitudealtAir density at high altitude; p0The power of a fan under plain elevation; rho0Is the ambient air density at plain altitude; n isaltIs the fan speed n under the condition of high altitude0The rotating speed of the fan under plain elevation.
5. The method according to any one of claims 1 to 4, wherein in step S2, the fan volume of the forced air cooling system of the power electronic device under high altitude condition is determined by:
acquiring the fan air volume of the forced air cooling system of the power electronic device under the high-altitude condition based on the obtained fan pressure loss according to the relevance of the fan pressure loss and the fan air volume;
or
And acquiring the fan air volume of the forced air cooling system of the power electronic device under the high-altitude condition based on the acquired fan power according to the relevance between the fan power and the fan air volume.
6. The method according to any one of claims 1 to 5, wherein in step S2, the temperature rise of the table top of the power electronic device forced air cooling system under high altitude conditions is determined by:
a table top temperature rise-Reynolds number curve of the radiator is obtained through a plain altitude temperature rise test, the Reynolds number under the high altitude condition is calculated, and the table top temperature rise under the high altitude condition is determined according to the Reynolds number obtained through calculation and the temperature rise-Reynolds number curve.
7. The method of claim 6, wherein the Reynolds number under high altitude conditions is calculated based on the obtained geometric parameters of the heat sink, the operating air volume and the air density corresponding to the altitude parameters.
8. The method of any one of claims 1 to 7, further comprising the operations of:
and designing a test tool, controlling the altitude in a high-altitude environment box to be a single environment variable, introducing the obtained target thermal design parameter to perform a simulation test, and evaluating the accuracy of the target thermal design parameter serving as an equivalent conversion result according to a test result.
9. A thermal design parameter equivalent scaling system for high altitude, the system comprising:
the calculation parameter acquisition module is used for acquiring thermal design parameters of a forced air cooling system of the power electronic device under plain altitude conditions as reference thermal design parameters, wherein the reference thermal design parameters comprise: the environmental air density, the table temperature rise, the fan pressure loss and the fan power of the forced air cooling system of the power electronic device;
the equivalent conversion module is used for analyzing and calculating by adopting a corresponding equivalent conversion scheme based on each reference thermal design parameter, and further determining a target thermal design parameter of the forced air cooling system of the power electronic device under the high altitude condition, wherein the target thermal design parameter comprises at least one of the following parameters: the fan pressure loss, the fan power, the fan air volume and the table top temperature rise of the forced air cooling system of the power electronic device.
10. The system as recited in claim 9, wherein the equivalence scaling module determines fan pressure loss for a power electronics forced air cooling system at high altitude conditions by:
according to the thermodynamic principle, the fan pressure loss of the power electronic device forced air cooling system under the plain altitude condition and the correlation between the ambient air density and the altitude parameter are analyzed, and the following mathematical model is constructed to calculate the fan pressure loss of the power electronic device forced air cooling system under the high altitude condition:
in the formula, paltThe pressure loss, rho, of the fan under high altitude conditionsaltAmbient air density at high altitude; p is a radical of0The pressure loss of the fan under plain elevation is obtained; rho0Is the air density at plain altitude; n isaltIs the fan speed n under the condition of high altitude0The rotating speed of the fan under plain elevation.
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