Development method of nucleate boiling heat transfer calculation model
By dividing nucleoboiling heat transfer into two stages—partially underheated and fully developed—and determining the heating surface wall temperature for each stage, the problem of inaccurate models in existing technologies is solved, and accurate calculation of nucleoboiling heat transfer is achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-18
- Publication Date
- 2026-03-27
AI Technical Summary
In the existing technology, the nucleation boiling heat transfer calculation model fails to accurately distinguish between the partially underheated nucleation boiling stage and the fully developed nucleation boiling stage, resulting in inaccurate fitting functions and discontinuities between stages, making it impossible to achieve a smooth transition.
The nucleosurfing heat transfer is divided into two stages: partially underheated nucleosurfing and fully developed nucleosurfing. The heating surface temperature of each stage is considered separately, and the nucleosurfing heat transfer calculation model is determined through linear and unidirectional convective heat transfer relationships.
It enables accurate prediction of wall temperature distribution during different stages of heat transfer, avoids discontinuities in the fitted curve, and improves the accuracy and consistency of the calculation model.
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Figure CN121744982A_ABST
Abstract
Description
Technical Field
[0001] Embodiments of this application relate to the field of computer-aided design using fluid dynamics, and more specifically to a method for developing a nucleate boiling heat transfer calculation model. Background Technology
[0002] The statements herein are provided merely as background information in connection with this application and do not necessarily constitute prior art.
[0003] Boiling is a common phenomenon. The convective heat transfer process in which heat is transferred from the wall to the liquid, causing it to boil and vaporize, is called boiling heat transfer.
[0004] Nucleus boiling is a stage that a liquid goes through when heated to boiling. It has wide applications in energy, power, petrochemical and other fields. A deeper understanding of the nucleus boiling heat transfer process can help improve energy utilization efficiency. Summary of the Invention
[0005] A brief overview of this application is provided below to offer a basic understanding of certain aspects thereof. It should be understood that this overview is not an exhaustive summary of the application. It is not intended to identify key or essential parts of the application, nor is it intended to limit its scope. Its purpose is merely to present certain concepts in a simplified form as a prelude to the more detailed description that follows.
[0006] An embodiment of this application provides a method for developing a nucleus boiling heat transfer calculation model, comprising the following steps: S10: obtaining heat transfer data, including the heat flux density of the heating surface, the wall temperature distribution of the heating surface, the mainstream temperature distribution of the fluid, the pressure of the fluid, and the mass flow density of the fluid; S20: under the condition that the heat flux density, the pressure of the fluid, and the mass flow density of the fluid are constant, determining the fully developed nucleus boiling heat transfer stage, and calculating the wall temperature of the heating surface in this stage; S30: changing the heat flux density, the pressure of the fluid, and the mass flow density of the fluid, determining the wall temperature T of the heating surface in multiple fully developed nucleus boiling heat transfer stages. Wq S40: Under the condition that the fluid pressure and the fluid mass flow density are constant, determine the heat flux density and the wall temperature T determined in step S30. Wq The relationship between the two states; S50: Based on the relationship determined in step S40 and the relationship of unidirectional convective heat transfer, determine the wall temperature of the heating surface in the partially underheated nucleate boiling heat transfer stage; S60: Based on the wall temperature of the heating surface determined in step S20 and the wall temperature determined in step S50, determine the nucleate boiling heat transfer calculation model.
[0007] The method provided in this application divides nucleoboiling into two stages: partially underheated nucleoboiling and fully developed nucleoboiling. By considering the wall temperature of the heating surface in partially underheated nucleoboiling and fully developed nucleoboiling respectively, the heat transfer calculation model of nucleoboiling is determined to accurately predict the complete wall temperature distribution of heat transfer in different stages. Attached Figure Description
[0008] Other objects and advantages of this application will become apparent from the following description of embodiments of this application with reference to the accompanying drawings, and will help to provide a comprehensive understanding of this application.
[0009] Figure 1 This is a flowchart illustrating the development method of the nucleus boiling heat transfer calculation model provided in the embodiments of this application.
[0010] Figure 2 This is a schematic diagram illustrating the heat transfer characteristic stages of the development method for the nucleus boiling heat transfer calculation model provided in this application embodiment.
[0011] Figure 3 This is a schematic diagram of the fitting of the relationship between nucleostatic boiling heat transfer heat flux and wall temperature, which is a fully developed development method of the nucleostatic boiling heat transfer calculation model provided in the embodiments of this application.
[0012] Figure 4 This is a schematic diagram showing the comparison between the calculated and measured values of the boiling heat transfer wall temperature distribution obtained by the development method of the nucleostatic boiling heat transfer calculation model provided in the embodiments of this application.
[0013] It should be noted that the accompanying drawings are not necessarily drawn to scale, but are shown only in a schematic manner without affecting the reader's understanding. Detailed Implementation
[0014] Exemplary embodiments of this application will be described below with reference to the accompanying drawings. For clarity and brevity, not all features of actual implementations are described in the specification. However, it should be understood that many implementation-specific decisions must be made in the development of any such actual embodiment to achieve the developer's specific goals, such as complying with constraints related to the system and business, and these constraints may vary depending on the implementation. Furthermore, it should be understood that while development work can be very complex and time-consuming, such development work is merely a routine task for those skilled in the art who benefit from the content of this application.
[0015] It should also be noted that, in order to avoid obscuring this application with unnecessary details, only the equipment structure and / or processing steps closely related to the solution according to this application are shown in the accompanying drawings, while other details that are not closely related to this application are omitted.
[0016] Nucleus boiling heat transfer comprises two stages: partially underheated nucleus boiling and fully developed nucleus boiling heat transfer, each with distinct characteristics. Current nucleus boiling heat transfer calculation models often fail to differentiate between these stages, directly fitting the data as an exponential function of heat flux density and superheat. However, the exponents of different models vary considerably, resulting in inaccurate fitted functions.
[0017] For calculations specifically targeting partially underheated nucleate boiling heat transfer, the superposition method is mostly used, which divides the total heat transfer flux into a single-phase convective component and a boiling heat transfer component, and calculates them using their respective formulas. However, using this method will cause the fitted curve to be discontinuous at the bubble point and the fully developed nucleate boiling initiation point, and the transition between different stages cannot be smooth.
[0018] Embodiments of this application provide a method for developing a nucleate boiling heat transfer calculation model, such as... Figure 1 As shown, Figure 1 This is a flowchart illustrating the development method of the nucleus boiling heat transfer calculation model provided in the embodiments of this application. The method provided in the embodiments of this application includes the following steps: S10: Obtain heat transfer data, including the heat flux density of the heating surface, the wall temperature distribution of the heating surface, the mainstream temperature distribution of the fluid, the pressure of the fluid, and the mass flow density of the fluid; S20: Under the condition that the heat flux density, the pressure of the fluid, and the mass flow density of the fluid are constant, determine the fully developed nucleus boiling heat transfer stage, and calculate the wall temperature of the heating surface in this stage; S30: Change the heat flux density, the pressure of the fluid, and the mass flow density of the fluid to determine the wall temperature T of the heating surface in multiple fully developed nucleus boiling heat transfer stages. Wq S40: Under the condition that the fluid pressure and the fluid mass flow density are constant, determine the heat flux density and the wall temperature T determined in step S30. Wq The relationship between the two states; S50: Based on the relationship determined in step S40 and the relationship of unidirectional convective heat transfer, determine the wall temperature of the heating surface in the partially underheated nucleate boiling heat transfer stage; S60: Based on the wall temperature of the heating surface determined in step S20 and the wall temperature determined in step S50, determine the nucleate boiling heat transfer calculation model.
[0019] See Figure 2 , Figure 2 This is a schematic diagram illustrating the heat transfer characteristic stages of the development method for the nucleus boiling heat transfer calculation model provided in this application embodiment. Figure 2 This illustrates the changes in measured wall temperature at different stages of nucleate boiling as the mainstream temperature increases during the transition from single-phase liquid forced convection to nucleate boiling. Figure 2It is known that in the partially underheated nucleoboiling stage, the wall temperature gradually transitions from the unidirectional relative heat transfer trend line to the fully developed nucleoboiling heat transfer wall temperature; in the fully developed nucleoboiling heat transfer stage, the wall temperature does not change with the increase of the mainstream temperature, but remains basically constant. The method provided in this application divides nucleoboiling into two stages: partially underheated nucleoboiling and fully developed nucleoboiling. By considering the wall temperature of the heating surface in the partially underheated nucleoboiling stage and the fully developed nucleoboiling stage respectively, the nucleoboiling heat transfer calculation model is determined to accurately predict the complete wall temperature distribution of heat transfer in different stages.
[0020] In some embodiments, step S20 further includes: S21: determining the trend of change between the mainstream temperature and the wall temperature of the heating surface; S22: determining the fully developed nucleate boiling heat transfer stage; S23: calculating the average value of multiple wall temperatures in the fully developed nucleate boiling heat transfer stage, the average value being the wall temperature of the heating surface in the fully developed nucleate boiling heat transfer stage.
[0021] Depend on Figure 2 It is evident that during the fully developed nucleo-boiling heat transfer stage, the wall temperature of the heating surface does not change with the increase of the mainstream temperature. Therefore, by determining the trend between the mainstream temperature and the wall temperature of the heating surface, it is possible to determine whether the current boiling heat transfer is in the fully developed nucleo-boiling heat transfer stage. Furthermore, by using the average temperature of multiple wall surfaces, the wall temperature of the heating surface in the fully developed nucleo-boiling heat transfer stage can be determined, avoiding inaccurate data due to uneven heating in a single area.
[0022] In some embodiments, in step S22, a fully developed nucleate boiling heat transfer stage is determined based on the mainstream temperature and the temperature of the wall surface of the heating surface.
[0023] Since the wall temperature of the heating surface does not change with the increase of the mainstream temperature during the fully developed nucleo-boiling heat transfer stage, it is possible to determine whether the current stage is fully developed nucleo-boiling heat transfer based on the mainstream temperature and the wall temperature of the heating surface.
[0024] In some embodiments, the stage in which the mainstream temperature increases while the temperature of the wall surface of the heated surface remains constant, i.e., the temperature of the heated surface does not increase with the increase of the mainstream temperature, is defined as the stage of fully developing nucleo-boiling heat transfer.
[0025] Since the wall temperature of the heating surface does not change with the increase of the mainstream temperature during the fully developed nucleo-boiling heat transfer stage, it can be determined that the current stage is the fully developed nucleo-boiling heat transfer stage when the mainstream temperature increases while the wall temperature of the heating surface remains unchanged.
[0026] In some embodiments, in step S40, the heat flux density and the wall temperature T determined in step S30 are determined. WqThe relationship between them is linear; the heat flux density and the wall temperature T determined in step S30 are determined. Wq The linear relationship between them.
[0027] Under a given heat flux, the wall temperature does not change with the increase of the mainstream temperature; however, the wall temperature for fully developing nucleate boiling heat transfer differs under different heat fluxes. Fitting the two to a linear relationship helps to determine the relationship between the heat transfer flux and the wall temperature for fully developing nucleate boiling heat transfer, so as to further determine the wall temperature of the heating surface in the partially underheated nucleate boiling heat transfer stage.
[0028] In some embodiments, the heat flux density is related to the wall temperature T determined in step S30. Wq The linear relationship between them is: q b =h b (T Wq -T ONB ).
[0029] q b h represents the heat flux density of boiling heat transfer. b T represents the boiling heat transfer coefficient. Wq T represents the wall temperature of the heating surface during the fully developed nucleo-boiling heat transfer stage. ONB The wall temperature representing the boiling initiation point is used to determine the boiling heat transfer coefficient h through a fitting method. b and the wall temperature T at the boiling point ONB .
[0030] In this embodiment, the heat flux density and the average wall temperature of the heating surface in the fully developed nucleation boiling heat transfer stage are fitted into a definite relationship so that the wall temperature of the heating surface in the partially underheated nucleation boiling heat transfer stage can be determined more accurately.
[0031] In some embodiments, in step S50, the heat flux density, the wall temperature of the heating surface during the partially underheated nucleation boiling heat transfer stage, and the mainstream temperature conform to the following relationship: q c =A c h c (T W -T b ).
[0032] q c h represents the heat flux density for single-phase heat transfer. c The heat transfer coefficient for unidirectional convection is determined using existing models, T. W T represents the wall temperature of the heating surface during the partially underheated nucleation boiling heat transfer stage. b Indicates the prevailing temperature, A c This indicates the area share of convective heat transfer.
[0033] In this embodiment, by fitting the relationship between heat flux density, wall temperature of the heating surface in the partially underheated nucleo-boiling heat transfer stage, and mainstream temperature, the accurate wall temperature of the heating surface in the partially underheated nucleo-boiling heat transfer stage can be obtained.
[0034] In some embodiments, in step S60, the heat flux density, the wall temperature of the heating surface, the mainstream temperature, and the wall temperature at the boiling initiation point conform to the following relationship, which is the nucleus boiling heat transfer calculation model: q = A c h c (T W -T b )+ A b h b (T Wq -T ONB ).
[0035] Where q represents heat flux density, h c The heat transfer coefficient for single-phase flow is T, determined using an existing model. W T represents the wall temperature of the heating surface during the partially underheated nucleation boiling heat transfer stage. b Indicates the prevailing temperature, A c A represents the area share of convective heat transfer. b h represents the boiling heat transfer area share. b T represents the boiling heat transfer coefficient. Wq T represents the wall temperature of the heating surface during the fully developed nucleo-boiling heat transfer stage. ONB This indicates the wall temperature at the point where boiling begins.
[0036] In this embodiment, the wall temperature of the heating surface, which simultaneously considers both partially underheated nucleoboiling and fully developed nucleoboiling, is used to determine nucleoboiling heat transfer. The total heat transfer flux is divided into two parts: convective heat transfer and boiling heat transfer. Based on the fact that the convective heat transfer component is proportional to the difference between the wall temperature and the mainstream temperature, and the boiling heat transfer component is proportional to the difference between the wall temperature and the foaming temperature, and that both heat transfer components are also proportional to their respective area proportions, the above-mentioned relationships are obtained to accurately obtain the nucleoboiling heat transfer calculation model.
[0037] In some embodiments, the convective heat transfer area share and the boiling heat transfer area share conform to the following relationship: A c =1-A b .
[0038] A c A represents the area share of convective heat transfer. b This indicates the area share of boiling heat transfer.
[0039] In this embodiment, based on the fact that during partially underheated nucleosurfing, the convective heat transfer area fraction decreases linearly with wall temperature, while the boiling heat transfer area fraction increases linearly with wall temperature, and the sum of the two remains 1, the above relationship is obtained. Furthermore, based on the total heat flux, the foaming temperature, and the wall temperature at which nucleosurfing heat transfer is fully developed under a certain heat flux, combined with the convective heat transfer area fraction and the boiling heat transfer area fraction, the wall temperature at a certain heat flux and different mainstream temperatures can be determined, thereby obtaining a nucleosurfing heat transfer calculation model.
[0040] In some embodiments, the boiling heat transfer area fraction is determined by the following relationship: A b =(T W -T ONB ) / (T Wq -T ONB ).
[0041] A b T represents the boiling heat transfer area share. W T represents the wall temperature of the heating surface during the partially underheated nucleation boiling heat transfer stage. Wq T represents the wall temperature of the heating surface during the fully developed nucleo-boiling heat transfer stage. ONB This indicates the wall temperature at the point where boiling begins.
[0042] In this embodiment, the boiling heat transfer area share increases linearly with the wall temperature. By obtaining the boiling heat transfer area share through the above relationship, it is possible to further determine the wall temperature at different mainstream temperatures under a certain heat flow based on the total heat transfer flux, foaming temperature, and wall temperature at which nucleation boiling heat transfer is fully developed under a certain heat flux, combined with the convective heat transfer area share and the boiling heat transfer area share, thereby obtaining the nucleation boiling heat transfer calculation model.
[0043] like Figure 3 As shown, Figure 3 This is a schematic diagram of the fitting of the relationship between nucleostatic boiling heat transfer heat flux and wall temperature, which is a fully developed development method of the nucleostatic boiling heat transfer calculation model provided in the embodiments of this application. Figure 3 The determination coefficient R in the working condition shown 2 The value is 0.9977, indicating a high accuracy in fitting the heat flow to the wall temperature. Based on the fitting formula, the boiling heat transfer coefficient is 0.4229 MW / m². 2 The foaming temperature is 269.5℃, which is 16.2℃ higher than the saturation temperature.
[0044] like Figure 4 As shown, Figure 4 This is a schematic diagram showing the comparison between calculated and measured values of the nucleus boiling heat transfer wall temperature distribution obtained from the development method of the nucleus boiling heat transfer calculation model provided in the embodiments of this application. Figure 4As shown in the figure, the measured and calculated values of wall temperature and mainstream temperature changes under two heat flows are presented. According to the legend, the red triangles and blue diamond-shaped dots represent the actual measured values under the two heat flows, and the dashed and solid lines represent the boiling curves fitted by the nucleus boiling heat transfer calculation model obtained by the method provided in the embodiments of this application under the two heat flows. The boiling curve accurately predicts the complete wall temperature distribution under the two heat flows, from single-phase relative heat transfer, through partially underheated nucleus boiling, to fully developed nucleus boiling heat transfer. The calculated results are in good agreement with the actual measured values, and the curves can smoothly transition between different heat transfer stages without any discontinuities.
[0045] Regarding the embodiments of this application, it should also be noted that, without conflict, the embodiments of this application and the features in the embodiments can be combined with each other to obtain new embodiments.
[0046] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. The scope of protection of this application shall be determined by the scope of the claims.
Claims
1. A method for developing a nucleus boiling heat transfer calculation model, characterized in that, It includes the following steps: S10: Obtain heat transfer data, which includes the heat flux density of the heating surface, the wall temperature distribution of the heating surface, the mainstream temperature distribution of the fluid, the pressure of the fluid, and the mass flux density of the fluid. S20: Under the condition that the heat flux density, the pressure of the fluid, and the mass flux density of the fluid are constant, determine the fully developed nucleate boiling heat transfer stage, and calculate the wall temperature of the heating surface in the fully developed nucleate boiling heat transfer stage. S30: By changing the heat flux density, the fluid pressure, and the fluid mass flux density, determine the wall temperature T of the heating surface for multiple fully developed nucleate boiling heat transfer stages. Wq ; S40: Under the condition that the pressure of the fluid and the mass flow density of the fluid are constant, determine the heat flow density and the wall temperature T determined in step S30. Wq The relationship between them; S50: Based on the relationship determined in step S40 and the unidirectional convective heat transfer relationship, determine the wall temperature of the heating surface in the partially underheated nucleate boiling heat transfer stage. S60: Determine the nucleation boiling heat transfer calculation model based on the wall temperature of the heating surface determined in step S20 and the wall temperature determined in step S50.
2. The development method according to claim 1, characterized in that, Step S20 also includes: S21: Determine the trend of change between the mainstream temperature and the wall temperature of the heating surface; S22: Determine the stage of fully developed nucleo-boiling heat transfer; S23: Calculate the average value of multiple wall surface temperatures in the fully developed nucleate boiling heat transfer stage, wherein the average value is the wall temperature of the heating surface in the fully developed nucleate boiling heat transfer stage.
3. The development method according to claim 2, characterized in that, In step S22, The fully developed nucleate boiling heat transfer stage is determined based on the mainstream temperature and the temperature of the wall surface of the heating surface.
4. The development method according to claim 2, characterized in that, The stage in which the mainstream temperature increases while the temperature of the wall surface of the heating surface remains unchanged, i.e., the temperature of the heating surface does not increase with the increase of the mainstream temperature, is the stage of fully developed nucleate boiling heat transfer.
5. The development method according to claim 1, characterized in that, In step S40, the heat flux density is determined in relation to the wall temperature T determined in step S30. Wq The relationship between them is linear; The heat flux density is determined in step S30, and the wall temperature T is determined in step S30. Wq The linear relationship between them.
6. The development method according to claim 5, characterized in that, The linear relationship is as follows: q b =h b (T Wq -T ONB ), q b h represents the heat flux density of boiling heat transfer. b T represents the boiling heat transfer coefficient. Wq T represents the wall temperature of the heating surface during the fully developed nucleo-boiling heat transfer stage. ONB The wall temperature at the point where boiling begins. The boiling heat transfer coefficient h was determined by fitting the data. b and the wall temperature T at the boiling initiation point ONB .
7. The development method according to claim 1, characterized in that, In step S50, the heat flux density, the wall temperature of the heating surface, and the mainstream temperature conform to the following relationship: q c =A c h c (T W -T b ), q c h represents the heat flux density for single-phase heat transfer. c The heat transfer coefficient for unidirectional convection, T, is determined using existing techniques. W T represents the wall temperature of the heating surface during the partially underheated nucleation boiling heat transfer stage. b Indicates the prevailing temperature, A c This indicates the area share of convective heat transfer.
8. The development method according to claim 1, characterized in that, In step S60, the heat flux density, the wall temperature of the heating surface, the mainstream temperature, and the wall temperature at the boiling initiation point conform to the following relationship: q= A c h c (T W -T b )+ A b h b (T Wq -T ONB ), Where q represents the heat flux density, h c The heat transfer coefficient for single-phase flow, T, is determined using existing techniques. W T represents the wall temperature of the heating surface during the partially underheated nucleation boiling heat transfer stage. b Indicates the prevailing temperature, A c A represents the area share of convective heat transfer. b h represents the boiling heat transfer area share. b T represents the boiling heat transfer coefficient. Wq T represents the wall temperature of the heating surface during the fully developed nucleo-boiling heat transfer stage. ONB This indicates the wall temperature at the point where boiling begins.
9. The development method according to claim 8, characterized in that, The convective heat transfer area share and the boiling heat transfer area share conform to the following relationship: A c =1-A b , A c A represents the area share of convective heat transfer. b This indicates the area share of boiling heat transfer.
10. The development method according to claim 8, characterized in that, The proportion of boiling heat transfer area is determined by the following formula: A b =(T W -T ONB ) / (T Wq -T ONB ), A b T represents the boiling heat transfer area share. W T represents the wall temperature of the heating surface during the partially underheated nucleation boiling heat transfer stage. Wq T represents the wall temperature of the heating surface during the fully developed nucleo-boiling heat transfer stage. ONB This indicates the wall temperature at the point where boiling begins.