A heat dissipation calculation method for energy storage converter suitable for high altitude applications

Abstract

This invention belongs to the field of energy storage converters, and particularly relates to a heat dissipation calculation method for energy storage converters suitable for high-altitude applications. This method first calculates the air temperature at a certain altitude, then analyzes the impact of altitude on the heat exchange process, introduces an altitude density ratio, corrects the air density based on the altitude density ratio, then calculates the fluid velocity between the radiator fins based on the energy storage converter radiator model, calculates the Reynolds number and Nusselt number of the radiator channels based on the fluid velocity, calculates the radiator channel thermal conductivity and the maximum surface temperature of the radiator based on the Reynolds number and Nusselt number of the radiator channels, and finally quantitatively analyzes the derating of the PCS power module under high-altitude conditions based on the maximum surface temperature of the radiator. This invention comprehensively considers the changes in the thermophysical properties of the air and the flow resistance-thermal resistance relationship under high-altitude conditions, ensuring the heat dissipation efficiency of the PCS in high-altitude scenarios.

Description

Technical Field

[0001] This invention belongs to the field of energy storage converters, and in particular relates to a heat dissipation calculation method for energy storage converters suitable for high-altitude applications. Background Technology

[0002] In today's energy and power systems, energy storage is not only a crucial element in balancing electricity supply and demand and enhancing the absorption capacity of renewable energy, but also a core engine driving the green energy revolution and promoting global sustainable development. As the core energy conversion device in new energy storage technologies, the reliability, safety, and stability of power conversion systems (PCS) have been extensively studied.

[0003] Energy storage converters are used in diverse environments, ranging from desert photovoltaic power plants to distributed offshore wind and solar power stations. Harsh operating conditions such as high altitude, high humidity and heat, and high salt spray place more stringent demands on the electrical and structural design of energy storage converters. Currently, there is no effective calculation method for the heat dissipation design of forced air-cooled PCS in high-altitude environments. As altitude increases, air density decreases and atmospheric pressure drops. Changes in altitude affect fan performance, cooling system flow resistance, and cooling air heat exchange efficiency. Under the same heat dissipation design, conventional air-cooled energy storage converters experience varying degrees of reduction in airflow and air pressure, leading to decreased overall heat dissipation performance, increased temperature rise, and in severe cases, the risk of system overheating shutdown and damage. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a heat dissipation calculation method for energy storage converters suitable for high-altitude applications. It comprehensively considers the changes in the thermophysical properties of air and the flow resistance-thermal resistance relationship under high-altitude operating conditions, ensuring the heat dissipation efficiency of the PCS in high-altitude scenarios.

[0005] To solve the aforementioned technical problem, the technical solution adopted by the present invention is: a heat dissipation calculation method for energy storage converters suitable for high-altitude applications, comprising the following steps:

[0006] S01. Calculate the air temperature T(a) at altitude a;

[0007] S02. Analyze the influence of altitude on the heat exchange process, and introduce the altitude-density ratio η(a).

[0008] 'a' represents altitude;

[0009] S03. Air density correction based on altitude density ratio ,

[0010] This represents the corrected air density at altitude a. Let be the air density at altitude a, derived from the ideal gas law.

[0011] S04. Calculate the velocity U of the fluid between the radiator fins based on the energy storage converter radiator model, and calculate the Reynolds number of the radiator channels based on the velocity U of the fluid between the radiator fins. and the radiator channel Nusselt number ,

[0012] , , ,

[0013] Reynolds number of the radiator channel and the radiator channel Nusselt number Substitute into the formula Calculate the thermal conductivity coefficient of the radiator. ,

[0014] This indicates the volumetric flow rate through the radiator. For the mass of the gas, Here, H is the fin spacing of the radiator, μ is the dynamic viscosity, l is the radiator length, and Pr is the Prandtl number. Thermal conductivity;

[0015] S05, the thermal conductivity coefficient of the radiator Substitute into the formula The highest surface temperature T of the radiator was calculated. max ;

[0016] This indicates the average temperature at the radiator outlet. Let A be the average temperature at the radiator inlet, and let A be the effective heat dissipation area of ​​the radiator. For isobaric specific heat capacity, The density of the fluid flowing through the radiator. The velocity of the fluid flowing through the radiator. The area through which air flows from the radiator's air outlet;

[0017] S06. Based on the highest surface temperature T of the heat sink max Quantitative analysis of PCS power module derating under high-altitude operating conditions.

[0018] Furthermore, step S06 specifically involves: calculating the maximum allowable operating temperature of the PCS by combining the derating factor of the power module and the temperature rise caused by thermal resistance, and comparing it with the highest surface temperature T of the heatsink. max Compared to the maximum allowable operating temperature of the PCS, if the highest surface temperature of the heatsink is T... maxIf the temperature exceeds the maximum allowable temperature for actual PCS operation, the PCS power module will be derated; otherwise, the PCS power module will operate at full load.

[0019] Furthermore, in step S01, the air temperature T(a) at altitude a is:

[0020] T0 is the initial temperature, which is 288.15 K at standard atmospheric pressure at sea level. In this step, T0 is the actual operating temperature of the PCS, and L is the temperature gradient, which is 0.0065 K / m.

[0021] Furthermore, in step S03, , Let M be the air pressure at altitude a, and M be the molar mass of air. Let J be the gas constant, taken as 8.3144598 J / (mol·K).

[0022] , This is the standard atmospheric pressure at sea level.

[0023] Furthermore, in step S02, the calculation process for the altitude density ratio η(a) is as follows:

[0024] first ,

[0025] in Let be the air density at altitude 'a', derived from the ideal gas law. This represents the air density at altitude a, calculated after considering the converted values ​​of air temperature and atmospheric pressure at altitude a. Let be the air pressure at altitude a. To correct for the air humidity at altitude a, P, , , These are gas pressure, gas constant, absolute temperature of the gas, and air humidity under ideal gas conditions, respectively.

[0026] Water vapor actually constitutes a very small proportion of the air. In practical engineering applications, hot air is considered dry air, so the calculation of the altitude density ratio is simplified to:

[0027] .

[0028] Furthermore, the actual operating temperature of the PCS is obtained through temperature sensor detection.

[0029] The beneficial effects of this invention are as follows: Considering the strong coupling relationship between air thermal characteristic parameters that vary with altitude, this invention proposes a heat dissipation calculation method for energy storage converters suitable for high-altitude applications. This method can accurately correct the thermal parameters of the PCS power module according to different altitudes. On the one hand, it can significantly improve the accuracy of heat dissipation design calculations for energy storage converters, more accurately assess the heat dissipation and derating design margins of energy storage converters under high-altitude conditions, and improve the economic efficiency of energy storage converter applications. On the other hand, this calculation method can provide a reliable reference for optimizing the heat dissipation performance of conventional air-cooled energy storage converter products, ensuring the working performance and operational stability of the converter under high-altitude conditions. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the heat dissipation system of the energy storage converter described in this invention;

[0031] Figure 2 This is a dimensional drawing of the heat sink model of the energy storage converter described in this invention, wherein... Figure 2 (a) is a front view of the radiator. Figure 2 (b) is a top view of the radiator;

[0032] Figure 3 This is a flowchart of the heat dissipation calculation method for energy storage converters applicable to high-altitude applications as described in this invention.

[0033] In the diagram: 1. Energy storage converter, 2. Internal components, 3. Circuit board, 4. Power module, 5. Heat sink, 6. Cooling fan, 7. External components. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0035] Example 1

[0036] This embodiment discloses a heat dissipation calculation method for energy storage converters suitable for high-altitude applications. Figure 1 This is a schematic diagram of the heat dissipation system for an energy storage converter. The energy storage converter 1 contains internal components 2 and a circuit board 3. A power module 4, which is the main heat source, is mounted on the circuit board 3. To achieve heat dissipation, a heat sink 5 is also provided. Heat dissipation is achieved through a circulation system involving a cooling fan 6, the heat sink 5, and external components 7. Specifically, the heat emitted by the power module 4 is transferred to the heat dissipation fins through the surface of the heat sink 5. Low-temperature air is blown by the cooling fan 6 through the air duct, heat dissipation fins, and external components 7, and heated to high temperature before being discharged from the energy storage converter 1.

[0037] like Figure 3 As shown, this method includes the following steps:

[0038] S01. Calculate the thermophysical properties of the air at altitude a, including air temperature T(a), air pressure P(a), and air density. First, calculate the air temperature T(a) at different altitudes; then, calculate the air pressure P(a) at different altitudes using the American Standard Atmosphere (USA) formula; finally, calculate the air density using the ideal gas law. ;

[0039] S02. Analyze the influence of altitude on the heat exchange process and introduce the altitude density ratio η(a);

[0040] S03. Air density correction based on altitude density ratio ;

[0041] S04. Calculate the Reynolds number Re based on the energy storage converter radiator model. b (a) Nusselt number of the radiator b (a) and the thermal conductivity h of the radiator b (a);

[0042] S05. Calculate the highest surface temperature T of the radiator. max .

[0043] In step S01, the air temperature T(a) at altitude a is calculated using formula 1:

[0044] (Formula 1),

[0045] Where a is the altitude, T0 is the initial temperature, which is 288.15K (15℃) at standard atmospheric pressure at sea level. The actual heat dissipation cavity temperature (obtained by a temperature sensor) is used in the thermal calculation of the energy storage converter. L is the temperature gradient, which is 0.0065K / m.

[0046] The American standard atmospheric pressure formula is:

[0047] (Formula 2),

[0048] In the formula, P(a) is the atmospheric pressure at altitude a; P0 is the standard atmospheric pressure at sea level, taken as 101325 Pa; g is the acceleration due to gravity, taken as 9.80665 m / s². 2 M is the molar mass of air, taken as 0.0289612 kg / mol; R is the gas constant, taken as 8.3144598 J / (mol·K).

[0049] Substituting the above values ​​into Formula 2, the air pressure is calculated as follows:

[0050] (Formula 3).

[0051] The ideal gas law is as follows:

[0052] PV = nRT (Formula 4)

[0053] In the formula, P is the gas pressure, V is the gas volume, n is the amount of substance of the gas, R is the ideal gas constant, and T is the absolute temperature of the gas. Converting the amount of substance n to mass form and introducing the molar mass of air M, n = m / M, we get PV = (m / M)RT, where m is the mass of the gas. Dividing both sides of the formula by V gives the formula for calculating air density.

[0054] (Formula 5).

[0055] in Let be the air density at altitude a, derived from the ideal gas law.

[0056] If we consider air as a mixture of dry air and water vapor, then the formulas for the relationship between air density, humidity, and altitude are derived as follows:

[0057] (Formula 6),

[0058] The air density at altitude a is calculated after considering the converted values ​​of air temperature and atmospheric pressure at altitude a. Let be the air humidity at altitude *a* derived from the ideal gas state, and w(a) be the corrected air humidity at altitude *a*. The gas constant is Let be the absolute temperature of the gas. This represents the pressure of the gas.

[0059] Combining formulas 5 and 6, we introduce the altitude density ratio η(a):

[0060] (Formula 7).

[0061] Since water vapor accounts for a very small percentage of the air, hot air is considered dry air in practical engineering applications, and the effect of air humidity is usually negligible. Equation 7 can be simplified to:

[0062] (Formula 8),

[0063] The corrected air density formulas for different altitudes are derived as follows:

[0064] (Formula 9),

[0065] This represents the corrected air density at altitude a.

[0066] Figure 2 This is a dimensional diagram of the heat sink model for an energy storage converter. The Reynolds number Re is calculated based on this model. b (a) Nusselt number of the radiator b (a) and the thermal conductivity h of the radiator b (a) is as follows: First, calculate the velocity U of the fluid between the fins based on the radiator parameters, and then substitute the velocity U of the fluid between the fins into Formula 11 to calculate the Reynolds number of the radiator channel. , the Reynolds number of the heat sink channel Substituting into Formula 12, the Nusselt number of heatsink channels can be calculated. Finally, the Reynolds number of the radiator channel is... and the radiator channel Nusselt number Substituting into Formula 13, the thermal conductivity coefficient of the radiator is calculated. The formulas are as follows:

[0067] (Formula 10),

[0068] (Formula 11),

[0069] (Formula 12),

[0070] (Formula 13).

[0071] in This indicates the volumetric flow rate through the radiator. For the mass of the gas, Here, H is the fin spacing of the radiator, μ is the dynamic viscosity, l is the radiator length, and Pr is the Prandtl number. is the thermal conductivity.

[0072] In step S05, the thermal conductivity coefficient of the heat sink is... Substitute into the formula:

[0073] (Formula 14),

[0074] The highest surface temperature T of the radiator was calculated. max , This indicates the average temperature at the radiator outlet. Let A be the average temperature at the radiator's air inlet, and let A be the effective heat dissipation area of ​​the radiator. For isobaric specific heat capacity, The density of the fluid flowing through the radiator. The velocity of the fluid flowing through the radiator. This refers to the area through which air flows from the radiator's outlet.

[0075] In this embodiment, the derivation process of formula 14 is as follows:

[0076] pass (Formula 15),

[0077] The logarithmic mean temperature difference was calculated. Therefore, it can be deduced that:

[0078] (Formula 16),

[0079] In the formula: T max T represents the highest surface temperature of the radiator. in T represents the average temperature at the radiator inlet. out This represents the average temperature at the radiator's air outlet.

[0080] According to the law of conservation of energy, the amount of heat exchanged between the air and the radiator is equal, that is:

[0081] (Formula 17),

[0082] (Formula 18),

[0083] In the formula: m is the mass of the flow, v is the air velocity, and h is the mass of the airflow. b (a) is the thermal conductivity coefficient of the radiator, A is the effective heat dissipation area of ​​the radiator, and A' is the area of ​​the air flowing through the radiator outlet.

[0084] The highest surface temperature T of the radiator can be obtained using formulas 17 and 18. max The calculation formula is as follows:

[0085] (Formula 14).

[0086] This embodiment uses Figure 2 Taking the dimensions of the heatsink model as an example, the total effective heat dissipation area is: P themal-total =0.055×0.078×6=25.74×10 -3 (m) 2 ), Heatsink area: S sink =0.55×0.25=137.5×10 -3 (m) 2 ).

[0087] The heat dissipation design and calculation are based on the datasheet of a certain model of PCS-based IGBT power module. Setting: Total loss P loss-total=685.009×6=4110 (W), air velocity between radiator fins v=13.645 (m / s), aerodynamic viscosity μ=17.9×10 -6 (Pa·s), specific heat capacity of air at constant pressure Cp = 1.005 × 10⁻⁶ 3 (J / kg·K), Prandtl number Pr=0.714, thermal conductivity of air λair=0.0267 (W / m·K); altitude a=0m, 4000m, PCS high temperature test temperature T0=318.15K (45℃) is the initial temperature.

[0088] Taking altitudes of 0 meters and 4000 meters as examples, the air temperature T(a) at different altitudes is: T(0) = 45°C, T(4000) = 19°C. The air pressure P(a) at different altitudes is: P(0) = 101.325, P(4000) = 64.7347. Air density... : , Correcting air density : , Based on the radiator model of the energy storage converter, the Reynolds number Re of the radiator at different altitudes is calculated. b Nusselt number b and the heat transfer coefficient h of the heat sink b (a) is:

[0089] Re b (0) = 13.53, Re b (4000) = 6.014.

[0090] Nu b (0) = 2.854, Nu b (4000) = 1.76.

[0091] h b (0) = 38.096, h b (4000) = 23.492.

[0092] Substituting the above calculation results, the maximum surface temperature Tmax of the radiator is calculated as follows: Tmax(0) = 79.007, Tmax(4000) = 100.549.

[0093] The above only provides the calculated results of the maximum radiator temperature at sea level (0 meters above sea level) and at an altitude of 4000 meters. Using the method proposed in this invention, the maximum radiator temperature (i.e., the actual maximum operating temperature of the PCS) can be calculated under different altitude conditions. Typical altitudes are 1000 meters, 2000 meters, and 3000 meters, which will not be listed here. The calculation results show that at an altitude of 4000 meters, the maximum surface temperature of the radiator is 100.549℃. Currently, most power modules used in PCS are IGBTs, whose maximum allowable temperature is 175℃. The IGBT design derating factor is 0.75. Considering the thermal resistance from the IGBT core to the module casing and from the module casing to the radiator surface, there are approximately 10℃ and 25℃ temperature rises respectively. Therefore, the actual maximum allowable operating temperature of the PCS is approximately 175℃. 0.75 - 10 - 25 = 96 (℃). Actual calculations show that the highest temperature of the radiator (IGBT contact surface) at an altitude of 4000 meters exceeds 100℃, surpassing the maximum allowable operating temperature of 96℃ for the PCS. Therefore, under these conditions, the PCS cannot operate at full load and must be derated; otherwise, there is a risk of thermal runaway and IGBT damage / explosion. Through actual calculations, the proposed radiator model and PCS loss conditions can guarantee no derating at an altitude of 3000 meters. It is evident that the proposed calculation method has practical guiding significance and reference value for product design in engineering applications.

[0094] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A heat dissipation calculation method for energy storage converters suitable for high-altitude applications, characterized in that: Includes the following steps: S01. Calculate the air temperature T(a) at altitude a; S02. Analyze the influence of altitude on the heat exchange process, and introduce the altitude-density ratio η(a). 'a' represents altitude; S03. Air density correction based on altitude density ratio , This represents the corrected air density at altitude a. Let be the air density at altitude a, derived from the ideal gas law. S04. Calculate the fluid velocity U between radiator fins and the Reynolds number of radiator channels based on the energy storage converter radiator model. and the radiator channel Nusselt number , ， ， ， Reynolds number of the radiator channel and the radiator channel Nusselt number Substitute into the formula Calculate the thermal conductivity coefficient of the radiator. , This indicates the volumetric flow rate through the radiator. For the mass of the gas, Here, H is the fin spacing of the radiator, μ is the dynamic viscosity, l is the radiator length, and Pr is the Prandtl number. Thermal conductivity; S05, the thermal conductivity coefficient of the radiator Substitute into the formula The highest surface temperature T of the radiator was calculated. max ; This indicates the average temperature at the radiator outlet. Let A be the average temperature at the radiator inlet, and let A be the effective heat dissipation area of ​​the radiator. For isobaric specific heat capacity, The density of the fluid flowing through the radiator. The velocity of the fluid flowing through the radiator. The area through which air flows from the radiator's air outlet; S06. Based on the highest surface temperature T of the heat sink max Analyze the derating of PCS power modules under high-altitude operating conditions.

2. The heat dissipation calculation method for energy storage converters suitable for high-altitude applications according to claim 1, characterized in that: Step S06 specifically involves: calculating the maximum allowable operating temperature of the PCS based on the derating factor of the power module and the temperature rise caused by thermal resistance, and comparing it with the highest surface temperature T of the heatsink. max Compared to the maximum allowable operating temperature of the PCS, if the highest surface temperature of the heatsink is T... max If the temperature exceeds the maximum allowable temperature for actual PCS operation, the PCS power module will be derated; otherwise, the PCS power module will operate at full load.

3. The heat dissipation calculation method for energy storage converters suitable for high-altitude applications according to claim 1, characterized in that: In step S01, the air temperature T(a) at altitude a is: T0 is the initial temperature, taken as 288.15K at standard atmospheric pressure at sea level. In this step, T0 is taken as the actual operating temperature of the PCS, and L is the temperature gradient.

4. The heat dissipation calculation method for energy storage converters suitable for high-altitude applications according to claim 1, characterized in that: In step S03, , Let M be the air pressure at altitude a, and M be the molar mass of air. The gas constant is , This is the standard atmospheric pressure at sea level.

5. The heat dissipation calculation method for energy storage converters suitable for high-altitude applications according to claim 1, characterized in that: In step S02, the calculation process for the altitude density ratio η(a) is as follows: first , in Let be the air density at altitude 'a', derived from the ideal gas law. This represents the air density at altitude a, calculated after considering the converted values ​​of air temperature and atmospheric pressure at altitude a. Let be the air pressure at altitude a. To correct for the air humidity at altitude a, P, , , These are gas pressure, gas constant, absolute temperature of the gas, and air humidity under ideal gas conditions, respectively. Water vapor actually constitutes a very small proportion of the air. In practical engineering applications, hot air is considered dry air, so the calculation of the altitude density ratio is simplified to: 。 6. The heat dissipation calculation method for energy storage converters suitable for high-altitude applications according to claim 3, characterized in that: The actual operating temperature of the PCS is obtained by detecting a temperature sensor.

7. The heat dissipation calculation method for energy storage converters suitable for high-altitude applications according to claim 3, characterized in that: The value of L is 0.0065 K / m.

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