Water source heat pump heat exchanger inner and outer wall surface temperature iterative calculation method and system

Abstract

The application provides a water source heat pump heat exchanger inner and outer wall surface temperature iterative calculation method and system, and belongs to the technical field of heat exchange measurement. According to the flow state type of the fluid in the pipe, the corresponding correlation formula is selected based on the basic data to calculate the pipe inner convection heat transfer Nusselt number; according to the heat exchange type of the pipe outer surface medium, the corresponding correlation formula is selected based on the basic data to calculate the pipe outer convection heat transfer Nusselt number; based on the pipe inner and outer Nusselt numbers, the pipe inner and outer wall convection heat transfer coefficients are respectively calculated; the heat balance equation is used to iteratively calculate the pipe inner and outer wall temperatures, and the property parameters and the convection heat transfer coefficients are recalculated according to the updated temperature values, and the calculation results of the inner and outer wall temperatures meet the preset target values. Through the condition subdivision according to the pipe inner flow state and the pipe outer heat exchange type, the Nusselt numbers and the convection heat transfer coefficients are respectively calculated, and the wall surface temperature is iteratively solved by using the heat balance equation, so that the accurate calculation of the water source heat pump heat exchanger inner and outer wall temperatures is realized.

Description

Technical Field

[0001] This invention relates to the field of heat exchange measurement technology, and in particular to an iterative calculation method and system for the inner and outer wall temperatures of a water source heat pump heat exchanger. Background Technology

[0002] Heat pump technology, as an important means of creating a comfortable environment using low-grade energy, can effectively alleviate the current energy crisis and has received widespread attention and rapid development in recent years. Among existing heat pumps, water source heat pump systems are widely used due to their high operating efficiency. For closed-loop surface water source heat pump systems, finding a front-end heat exchange system that can adapt to the surface water environment, has high heat exchange efficiency, and offers excellent cost-effectiveness has become a crucial issue in solving the problem of front-end heat extraction.

[0003] Current research on the heat exchange characteristics of various front-end heat exchangers typically involves arranging a certain number of temperature measuring points on the outer wall of the pipe to measure the outer wall temperature, and taking the average value of the measurement results as the average outer wall temperature of the pipe. For the inner wall temperature of the pipe, which is difficult to measure directly, it is calculated by using the outer wall temperature and the thermal resistance of the pipe, thereby studying the variation law of the inner and outer wall temperatures of the pipe.

[0004] However, placing temperature measuring points on the outer wall of the pipe is not only labor-intensive and resource-intensive, but also prone to errors. For example, there may be gaps between the temperature measuring point and the outer wall of the pipe, or the insulation layer outside the measuring point may be ineffective, causing the temperature measurement results to be affected by the medium on the outer surface of the pipe. These factors may interfere with the accuracy of the research results. Summary of the Invention

[0005] To address the aforementioned issues, this invention proposes an iterative calculation method and system for the inner and outer wall temperatures of a water source heat pump heat exchanger. By subdividing the operating conditions according to the flow regime inside the pipe and the heat transfer type outside the pipe, calculating the Nusselt number and the convective heat transfer coefficient separately, and using the heat balance equation to iteratively solve the wall temperature, the accurate calculation of the inner and outer wall temperatures of the water source heat pump heat exchanger is achieved.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides an iterative calculation method for the inner and outer wall temperatures of a water source heat pump heat exchanger, comprising:

[0008] Collect basic data of the heat exchanger under stable operating conditions;

[0009] Based on the flow regime of the fluid inside the pipe, the corresponding first-order correlation is selected to calculate the Nusselt number of convective heat transfer inside the pipe based on the aforementioned basic data; the flow regime includes laminar flow, transitional flow, and turbulent flow.

[0010] Based on the heat transfer type of the medium on the outer surface of the tube, the corresponding second-order correlation is selected to calculate the Nusselt number of the external convective heat transfer. The heat transfer type includes natural convection in a static state and forced convection in a flowing state.

[0011] Based on the Nusselt numbers inside and outside the pipe, the convective heat transfer coefficients of the inner and outer walls of the pipe are calculated respectively.

[0012] The temperature of the inner and outer walls of the pipe is calculated iteratively using the heat balance equation, and the physical properties and convective heat transfer coefficient are recalculated based on the updated temperature values ​​until the calculated results of the inner and outer wall temperatures meet the preset target values.

[0013] Secondly, the present invention provides an iterative calculation system for the inner and outer wall temperatures of a water source heat pump heat exchanger, comprising:

[0014] The data acquisition module is configured to collect basic data of the heat exchanger under stable operating conditions.

[0015] The pipe data calculation module is configured to select the corresponding first-order correlation to calculate the Nusselt number of convective heat transfer in the pipe based on the basic data according to the flow regime type of the fluid in the pipe; the flow regime type includes laminar flow, transitional flow, and turbulent flow;

[0016] The external data calculation module is configured to select the corresponding second-order correlation to calculate the Nusselt number of external convective heat transfer based on the basic data according to the heat transfer type of the medium on the external surface of the pipe; the heat transfer type includes natural convection in a static state and forced convection in a flowing state;

[0017] The heat transfer coefficient calculation module is configured to calculate the convective heat transfer coefficients of the inner and outer walls of the pipe based on the Nusselt numbers inside and outside the pipe, respectively.

[0018] The iterative calculation module is configured to iteratively calculate the inner and outer wall temperatures of the pipe using the heat balance equation, and recalculate the physical properties and convective heat transfer coefficients based on the updated temperature values ​​until the calculated inner and outer wall temperatures meet the preset target values.

[0019] Thirdly, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the iterative calculation method for the inner and outer wall temperatures of a water source heat pump heat exchanger as described in the first aspect.

[0020] Fourthly, the present invention provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps in the iterative calculation method for the inner and outer wall temperatures of a water source heat pump heat exchanger as described in the first aspect.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] This invention matches specific correlation equations to three flow regimes (laminar, transitional, and turbulent) inside the pipe and two heat transfer types (natural and forced convection) outside the pipe, avoiding the adaptation bias of a single formula to complex operating conditions and accurately depicting the heat transfer laws under different scenarios. Simultaneously, an iterative mechanism is constructed around the heat balance equation, combining dynamic correction of physical property parameters and convective heat transfer coefficients with updated temperatures, solving the problem of the disconnect between wall temperature and heat transfer characteristics in static calculations, ensuring that the results closely match the actual heat transfer process. The obtained accurate wall temperature provides reliable data support for the structural design, performance optimization, and operational energy efficiency assessment of water source heat pump heat exchangers, reducing design defects caused by parameter errors and lowering equipment operating energy consumption and maintenance costs.

[0023] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute a limitation thereof.

[0025] Figure 1 A flowchart illustrating the main steps of an iterative calculation method for the inner and outer wall temperatures of a water source heat pump heat exchanger, as provided in this embodiment of the invention.

[0026] Figure 2 A detailed flowchart of an iterative calculation method for the inner and outer wall temperatures of a water source heat pump heat exchanger, provided in an embodiment of the present invention. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] Example 1

[0029] like Figure 1 As shown in the figure, this embodiment discloses an iterative calculation method for the inner and outer wall temperatures of a water source heat pump heat exchanger, including the following steps:

[0030] S1: Collect basic data of the heat exchanger under stable operating conditions;

[0031] S2: Based on the flow regime of the fluid inside the pipe, select the corresponding first-order correlation to calculate the Nusselt number of convective heat transfer inside the pipe based on the basic data; the flow regime includes laminar flow, transitional flow, and turbulent flow;

[0032] S3: Based on the heat transfer type of the medium on the outer surface of the pipe, select the corresponding second-order correlation to calculate the Nusselt number of the external convective heat transfer according to the basic data; the heat transfer type includes natural convection in a static state and forced convection in a flowing state;

[0033] S4: Calculate the convective heat transfer coefficients of the inner and outer walls of the pipe based on the Nusselt numbers inside and outside the pipe, respectively;

[0034] S5: Iteratively calculate the temperature of the inner and outer walls of the pipe using the heat balance equation, and recalculate the physical properties and convective heat transfer coefficient based on the updated temperature values ​​until the calculated results of the inner and outer wall temperatures meet the preset target values.

[0035] Next, combined Figure 2 This embodiment provides a detailed description of an iterative calculation method for the inner and outer wall temperatures of a water source heat pump heat exchanger. Figure 2 middle This indicates the Nusselt number for convective heat transfer inside the pipe. This represents the Nusselt number for external convective heat transfer.

[0036] In S1, the basic operating condition data of the heat exchanger is collected first.

[0037] Measuring the inlet and outlet temperatures of the circulating medium inside the pipe under stable operating conditions. , Total flow rate of circulating medium Temperature of the medium on the outer surface of the pipe Flow rate of medium on the outer surface of the pipe And based on the cross-sectional area of ​​the circulating medium flow. and surface medium flow cross-sectional area Calculate the flow rate of the circulating medium. and the flow rate of the surface medium .

[0038] Assume the initial average temperature of the inner wall of the pipe is The initial average temperature of the outer wall of the pipe is .

[0039] Calculate the intrinsic temperature inside the heat exchanger tubes and external qualitative temperature ,in This represents the average temperature of the outer wall of the pipe.

[0040] In S2, the fluid flow within the pipe exhibits different flow regimes, including laminar, turbulent, and transitional flows. Due to significant differences in momentum transfer and heat exchange mechanisms across these flow regimes, conventional techniques do not provide a universal correlation that can accurately describe the convective heat transfer characteristics of all flow regimes simultaneously. Therefore, this embodiment employs different Nusselt number correlations for laminar, turbulent, and transitional flows. By setting different coefficients and parameters (such as Reynolds number, Prandtl number, pipe geometry parameters, and temperature correction terms), the unique flow and heat transfer patterns under each flow regime are matched, thereby ensuring the accuracy of the Nusselt number calculation.

[0041] Specifically, at the qualitative temperature, based on different flow regimes of the fluid inside the pipe, the corresponding first-order correlation is selected to calculate the Nusselt number of convective heat transfer inside the pipe:

[0042] (1) If the fluid inside the pipe is laminar;

[0043] Corresponding to laminar convection heat transfer type, i.e., Reynolds number inside the tube. When the convective heat transfer Nusselt number inside the pipe is calculated, Equation (1) is used. .

[0044] (1)

[0045] in, The Reynolds number of the circulating medium; The Prandtl number of the circulating medium; This refers to the inner diameter of the pipe, in units of... m ; The length of the pipe is expressed in units of 1. m ; The dynamic viscosity of the circulating medium is expressed in units of... Pa·s ; The dynamic viscosity of the circulating medium at the inner wall of the pipe, in units of... Pa·s .

[0046] (2) If the fluid inside the pipe is turbulent;

[0047] Corresponding to the turbulent convection heat transfer type, i.e., the Reynolds number inside the tube. When the tube is in the convective heat transfer Nusselt number is calculated using equation (2) or equation (3), the following formulas are used:

[0048] (2)

[0049] (3)

[0050] Specifically, when the constant temperature inside the heat exchanger tubes... greater than the temperature of the medium on the outer surface of the pipe When the convective heat transfer Nusselt number inside the tube is calculated using equation (2), when the definite temperature inside the tube of the heat exchanger is... Less than the temperature of the medium on the outer surface of the pipe When the convective heat transfer Nusselt number inside the tube is calculated, Equation (3) is used.

[0051] Since temperature differences can affect fluid properties and heat transfer patterns, this embodiment selects corresponding formulas for two different situations. This makes the calculation of the Nusselt number more consistent with the actual heat transfer process, improves the calculation accuracy of key parameters such as the convective heat transfer coefficient, provides a more reliable basis for subsequent heat exchanger design and performance analysis, and reduces errors caused by not considering temperature differences.

[0052] (3) If the fluid inside the pipe is in a transitional flow state between laminar and turbulent flow;

[0053] The corresponding transitional flow state convective heat transfer type, i.e. When the convective heat transfer Nusselt number inside the tube is calculated, Equation (4) is used.

[0054] (4)

[0055] in, The Prandt number is the medium at the inner wall of the pipe.

[0056] In this embodiment, by selecting the corresponding correlation formula to calculate the Nusselt number of convective heat transfer within the pipe based on different flow states (laminar, transitional, and turbulent), the calculation of the Nusselt number can better reflect actual heat transfer conditions. Qualitative temperature ensures accurate values ​​for water properties (such as dynamic viscosity and thermal conductivity), laying the foundation for the calculation. Selecting the correlation formula based on the flow state allows for targeted matching of heat transfer patterns under different flow states: laminar flow aligns with the heat transfer characteristics dominated by molecular diffusion, turbulent flow adapts to the strong heat transfer characteristics of fluid particle mixing, and transitional flow takes into account both characteristics, avoiding the bias of calculations using a single correlation formula. Ultimately, the Nusselt number can be accurately obtained, providing a reliable basis for subsequent calculations of the convective heat transfer coefficient and the temperature of the inner and outer walls of the pipe, improving the accuracy of the overall iterative calculation, and reducing errors caused by improper parameter or formula adaptation.

[0057] In S3, during the heat exchange process, the inside and outside of the tube form an interconnected overall heat exchange system, requiring separate analysis of the heat transfer characteristics on each side. The dominant heat transfer mechanisms differ significantly depending on whether the medium outside the tube is stationary or flowing:

[0058] When the medium is stationary, heat transfer mainly relies on natural convection (flow heat transfer caused by density difference due to temperature difference in the fluid), the flow velocity is extremely low, and the heat transfer intensity is weak.

[0059] When the medium flows, it is forced convection (flow heat transfer driven by external force), with high flow velocity, strong fluid disturbance, and more intense heat transfer.

[0060] This fundamental difference in flow state directly affects the calculation of the Nusselt number for convective heat transfer (the correlations and influencing factors for natural convection and forced convection are drastically different). Therefore, after clarifying the heat transfer inside the tubes, ignoring the differences in the external state will greatly affect the accuracy of the overall heat transfer calculation. Thus, this embodiment will next analyze the static and dynamic states outside the tubes, selecting the corresponding second-order correlations for calculation to completely and accurately characterize the entire heat transfer process inside and outside the heat exchanger tubes.

[0061] (1) When the surface medium outside the pipe is in a static state;

[0062] The natural convection Nusselt number between the outer wall of the pipe and the surface medium can be calculated using equations (5) and (6):

[0063] (5)

[0064] (6)

[0065] in, For external convection heat transfer, the Nusselt number is... The Rayleigh number represents the heat transfer rate of natural convection outside the tube. g This is the acceleration due to gravity, in units of 1. m / s 2 ; This is the coefficient of volumetric expansion, in units of... 1 / K ; Kinematic viscosity, unit: Pa·s ; This is the thermal diffusivity, in units of... m 2 / s , C o and n o It is a constant, and its value is determined according to Ra x The calculation results are determined; This represents the average temperature of the outer wall of the pipe. The temperature of the medium on the outer surface of the pipe; These are standard dimensions, in units of... m .

[0066] (2) When the medium on the surface outside the pipe is in a flowing state;

[0067] Nusselt number of forced convection outside the pipe between the outer wall and the surface medium:

[0068] (7)

[0069] (8)

[0070] in, Reo The Reynolds number for external convection heat transfer; Pr fo The Prandtl number of the surface medium; Pr wo,x The Prandt number is the surface medium at the outer wall of the pipe. Kinematic viscosity; The average flow velocity of the surface medium is expressed in units of 1000 m / s. m / s , d o Indicates the outer diameter of the pipe, in units of m ; C o and n o It is a constant, and its value is determined according to Re o The calculation results are determined.

[0071] In this embodiment, by distinguishing between the static and flowing states of the medium outside the tubes, the Nuschier number is calculated using correlation formulas for natural convection and forced convection, effectively characterizing the heat transfer characteristics outside the heat exchanger tubes. This avoids overall heat transfer calculation deviations caused by neglecting differences in the external state, and can completely and accurately reflect the entire heat transfer process inside and outside the heat exchanger tubes, thereby improving the accuracy of heat exchanger performance analysis.

[0072] In S4, it can be seen from the above correlation formula for calculating convective heat transfer inside and outside the pipe that after assuming the average temperature values ​​of the inner and outer walls of the pipe, the qualitative temperature and related physical property parameters of heat transfer at each stage can be determined by solving or looking up tables, and then the theoretical heat transfer can be calculated through the heat transfer correlation formula.

[0073] Although the Nusselt number was calculated in the initial stages S2-S3 based on the flow regime inside the pipe and the state of the medium outside the pipe, it only reflects the heat transfer correlation characteristics. It is necessary to convert the convective heat transfer coefficient into the actual heat transfer intensity (quantifying the heat flow per unit area and temperature difference) to provide key parameters for the subsequent heat balance equation. At the same time, the wall temperature and the heat transfer coefficient affect each other. It is necessary to calculate the initial heat transfer coefficient based on the initial wall temperature before the new wall temperature can be derived to form an iterative closed loop.

[0074] Therefore, the convective heat transfer coefficients of the inner and outer walls of the pipe are calculated according to equations (9) and (10), respectively.

[0075] (9)

[0076] in, h i,x The convective heat transfer coefficient of the inner wall of the pipe, in units of W / (m 2 ·K) ; The Nusselt number represents the heat transfer rate during convective heat transfer within the tube. λj Thermal conductivity of the circulating medium, in units of W / (m·K) , This refers to the inner diameter of the pipe.

[0077] The convective heat transfer coefficient between the outer wall of the tube and the surface medium can be calculated by equation (11):

[0078] (10)

[0079] in, h o,x The convective heat transfer coefficient of the outer wall of the pipe, in units of... W / (m 2 ·K) ; For external convection heat transfer, the Nusselt number is used. λ h Surface thermal conductivity, in units of W / (m 2 ·K) ; h These are standard dimensions, in units of... m .

[0080] In S5, the temperature of the inner and outer walls of the pipe is calculated iteratively.

[0081] Under stable heat exchange conditions, the heat exchange at each stage of a pipeline satisfies equation (12):

[0082] (11)

[0083] (12)

[0084] in, h i,x The convective heat transfer coefficient of the inner wall of the pipe. h o,x The convective heat transfer coefficient of the inner wall of the pipe. F i The inner wall area of ​​the pipe, in units of m 2 ; F o This refers to the outer wall area of ​​the pipe, in units of... m 2 ; t j The internal temperature of the tube; t h The temperature of the medium on the outer surface of the pipe; t i,x This refers to the temperature of the inner wall of the pipe. t o,x This refers to the temperature of the outer wall of the pipe. R tThe thermal resistance between the inner and outer walls of the tube, expressed in K / W. λ m Thermal conductivity of the pipe material, in units of W / (m·K) ; d o The outer diameter of the pipe. This refers to the inner diameter of the pipe, in units of... m .

[0085] According to equation (12), the iterative equations for the inner and outer wall temperatures of the pipe can be obtained as shown in equations (13) and (14), respectively:

[0086] (13)

[0087] (14)

[0088] When the temperature of the inner and outer walls of the tube changes, the heat transfer coefficients inside and outside the tube also change. Therefore, the relevant physical properties and convective heat transfer coefficients need to be recalculated.

[0089] Once the calculated temperatures of the inner and outer walls of the pipe meet the preset target values, i.e., the preset accuracy requirements are met, the final average temperature of the inner and outer walls of the pipe can be obtained; if the calculated results do not meet the accuracy requirements, the process returns to step three and iterates again.

[0090] As one implementation method, under a stable heat release condition, when using the correlation formula to calculate the convective heat transfer coefficient outside the pipe, if the heat transfer outside the pipe is natural convection, it can be seen from equations (6) and (7) that when the temperature of the outer wall of the pipe is too large, the volume expansion coefficient of the surface medium at the outer wall of the pipe is... Larger, kinematic viscosity and thermal diffusivity Smaller, thermal conductivity The number is too large, resulting in an excessively high Rayleigh number. Ra and Nushert number Nu o The result is too high; the external convective heat transfer coefficient is too large. h o It is also too large; if the heat transfer outside the pipe is forced convection, it can be seen from equations (8) and (9) that when the temperature of the outer wall of the pipe is too large, the kinematic viscosity of the medium on the surface of the outer wall of the pipe is also too large. And Prandtl Pr wo The Prandtl number is relatively small, especially for surfaces far from the wall. Pr f The unchanged result leads to the calculated Reynolds number Re o and Nushert number Nu o The result is too high; the external convective heat transfer coefficient is too large. h oThe values ​​are also too large, so the calculated heat transfer coefficient and heat transfer amount outside the tube must be greater than the theoretical value. That is, the heat release outside the tube calculated using the heat transfer correlation increases monotonically as the temperature of the outer wall of the tube increases.

[0091] When the temperature of the outer wall of the pipe is taken as the temperature of the medium on the outer surface of the pipe, the heat transfer heat calculated by the heat transfer correlation is 0; when the temperature of the outer wall of the pipe is taken as the average temperature of the circulating medium inside the pipe, the heat transfer heat calculated by the heat transfer correlation is always greater than the theoretical value of the heat transfer heat outside the pipe. According to the medium value theorem and monotonicity, the calculated result of the pipe outer wall temperature is unique.

[0092] As can be seen from equations (5) and (12), the average temperature difference between the inner and outer walls of the pipe is only affected by the thermal conductivity of the pipe material. Therefore, under a stable working condition, the temperature difference between the inner and outer walls of the pipe is a definite value, and the calculation result of the inner wall temperature of the pipe is also unique.

[0093] Example 1

[0094] The heat exchanger is configured as a U-shaped capillary network with nine vertically arranged tubes, each 2m long, 20mm apart, and 60mm apart between adjacent capillary cores. The inlet temperature of the circulating medium inside the capillary is 35.87℃, the outlet temperature is 27.11℃, the average flow velocity is 0.05m / s, and the water outside the capillary is stagnant at 26.03℃.

[0095] To simplify calculations, this embodiment does not consider the changes in fluid properties caused by the variation in the average temperature of the inner and outer walls of the capillary during the iteration process. In this embodiment, the qualitative temperature at the inner wall of the pipe is taken as the average of the qualitative temperature of the medium and the temperature of the water outside the pipe, and this temperature is used to determine the dynamic viscosity of the medium at the inner wall of the pipe; the temperature of the water outside the pipe is taken as the qualitative temperature of convective heat transfer outside the pipe, and the relevant physical properties are calculated.

[0096] The initial average temperature of the inner wall of the pipe was set at 31℃, and the initial average temperature of the outer wall was set at 27℃. Ra After calculation, the correlation for natural convection heat transfer outside the pipe was determined. C o The value is 0.1. n o The value is 1 / 3.

[0097] The iterative calculation process values ​​of the relevant physical quantities are shown in Table 1.

[0098] Table 1. Iterative calculation values ​​of relevant physical quantities;

[0099]

[0100] It can be seen that after 11 iterations, the average temperatures of the inner and outer walls of the capillary are quite close in the two adjacent iterations, with the difference in temperature calculation results before and after the iteration being less than 0.01℃. In this embodiment, the average temperature of the inner wall of the capillary should be 29.80℃, and the average temperature of the outer wall of the capillary should be 27.97℃.

[0101] This specific embodiment subdivides the flow regime into laminar / transitional / turbulent flow inside the pipe and distinguishes the heat transfer type into natural / forced convection outside the pipe, matching a dedicated correlation to accurately capture the heat transfer characteristics under different operating conditions. At the same time, it constructs an iterative closed loop of temperature-physical property-heat transfer coefficient-temperature, dynamically corrects parameters based on the heat balance equation, solves the problem of disconnection in static calculation, and ultimately improves the accuracy of wall temperature calculation, providing reliable data support for heat exchanger design optimization and energy efficiency assessment.

[0102] Example 2

[0103] This embodiment provides an iterative calculation system for the inner and outer wall temperatures of a water source heat pump heat exchanger, including:

[0104] The data acquisition module is configured to collect basic data of the heat exchanger under stable operating conditions.

[0105] The pipe data calculation module is configured to select the corresponding correlation to calculate the Nusselt number of convective heat transfer in the pipe based on the basic data according to the flow regime type of the fluid in the pipe; the flow regime type includes laminar flow, transitional flow, and turbulent flow.

[0106] The external data calculation module is configured to select the corresponding correlation to calculate the Nusselt number of external convective heat transfer based on the basic data according to the heat transfer type of the medium on the external surface of the pipe; the heat transfer type includes natural convection in a static state and forced convection in a flowing state;

[0107] The heat transfer coefficient calculation module is configured to calculate the convective heat transfer coefficients of the inner and outer walls of the pipe based on the Nusselt numbers inside and outside the pipe, respectively.

[0108] The iterative calculation module is configured to iteratively calculate the inner and outer wall temperatures of the pipe using the heat balance equation, and recalculate the physical properties and convective heat transfer coefficients based on the updated temperature values ​​until the calculated inner and outer wall temperatures meet the preset target values.

[0109] Example 3

[0110] This embodiment provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps in the iterative calculation method for the inner and outer wall temperatures of a water source heat pump heat exchanger as described in Embodiment 1 above.

[0111] Example 4

[0112] This embodiment provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the steps in the iterative calculation method for the inner and outer wall temperatures of a water source heat pump heat exchanger as described in Embodiment 1 above.

[0113] The steps or modules involved in Embodiments 2 to 4 above correspond to those in Embodiment 1. For specific implementation details, please refer to the relevant description section of Embodiment 1. The term "computer-readable storage medium" should be understood as a single medium or multiple media including one or more instruction sets; it should also be understood as including any medium capable of storing, encoding, or carrying an instruction set for execution by a processor and enabling the processor to perform any of the methods in this invention.

[0114] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. 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 method for iterative calculation of the inner and outer wall temperatures of a water source heat pump heat exchanger, characterized in that, include: Collect basic data of the heat exchanger under stable operating conditions; Based on the flow regime of the fluid inside the pipe, the corresponding first-order correlation is selected to calculate the Nusselt number of convective heat transfer inside the pipe based on the aforementioned basic data; the flow regime includes laminar flow, transitional flow, and turbulent flow. Based on the heat transfer type of the medium on the outer surface of the tube, the corresponding second-order correlation is selected to calculate the Nusselt number of the external convective heat transfer. The heat transfer type includes natural convection in a static state and forced convection in a flowing state. Based on the Nusselt numbers inside and outside the pipe, the convective heat transfer coefficients of the inner and outer walls of the pipe are calculated respectively. The temperature of the inner and outer walls of the pipe is calculated iteratively using the heat balance equation, and the physical properties and convective heat transfer coefficient are recalculated based on the updated temperature values ​​until the calculated inner and outer wall temperatures meet the preset target values; the iterative calculation of the inner and outer wall temperatures using the heat balance equation specifically involves: ； ； ； ； in, h i,x The convective heat transfer coefficient of the inner wall of the pipe. h o,x The convective heat transfer coefficient of the inner wall of the pipe. F i The inner wall area of ​​the pipe; l This refers to the length of the pipe. F o This refers to the outer wall area of ​​the pipe. t j The internal temperature of the tube; t h The temperature of the medium on the outer surface of the pipe; t i,x This refers to the temperature of the inner wall of the pipe. t o,x This refers to the temperature of the outer wall of the pipe. R t The thermal resistance between the inner and outer walls of the pipe; λ m Thermal conductivity of the pipe material; d o The outer diameter of the pipe; d i This refers to the inner diameter of the pipe.

2. The method for iterative calculation of the inner and outer wall temperatures of a water source heat pump heat exchanger as described in claim 1, characterized in that, The basic data of the heat exchanger under stable operating conditions include the temperature, flow rate and velocity of the circulating medium inside the pipe and the medium on the outer surface of the pipe, the preset initial value of the average temperature of the inner and outer walls of the pipe, and the qualitative temperature inside and outside the pipe.

3. The method for iterative calculation of the inner and outer wall temperatures of a water source heat pump heat exchanger as described in claim 1, characterized in that, If the flow pattern of the fluid inside the pipe is laminar, the corresponding first-order correlation is selected based on the aforementioned basic data to calculate the Nusselt number of convective heat transfer inside the pipe; specifically including: ； in, Re j The Reynolds number of the circulating medium; Pr j The Prandtl number of the circulating medium; d i l is the inner diameter of the pipe; l is the length of the pipe; μ j The dynamic viscosity of the circulating medium; μ i,x The dynamic viscosity of the circulating medium at the inner wall of the pipe.

4. The method for iterative calculation of the inner and outer wall temperatures of a water source heat pump heat exchanger as described in claim 3, characterized in that, If the flow pattern of the fluid inside the pipe is turbulent, the corresponding first-order correlation is selected based on the aforementioned basic data to calculate the Nusselt number of convective heat transfer inside the pipe; specifically including: When the constant temperature inside the heat exchanger tubes greater than the temperature of the medium on the outer surface of the pipe hour: ； When the constant temperature inside the heat exchanger tubes Less than the temperature of the medium on the outer surface of the pipe hour: 。 5. The method for iterative calculation of the inner and outer wall temperatures of a water source heat pump heat exchanger as described in claim 3, characterized in that, If the flow pattern of the fluid inside the pipe is a transitional flow between laminar and turbulent flow, the corresponding first-order correlation is selected based on the aforementioned basic data to calculate the Nusselt number of convective heat transfer inside the pipe; specifically including: ； in, Pr wi The Prandt number is the medium at the inner wall of the pipe.

6. The method for iterative calculation of the inner and outer wall temperatures of a water source heat pump heat exchanger as described in claim 1, characterized in that, The step of calculating the Nusselt number of external convective heat transfer based on the heat transfer type of the medium on the outer surface of the pipe and the basic data by selecting the corresponding second-order correlation equation specifically includes: When the surface medium outside the pipe is stationary, the natural convection Nusselt number between the outer wall of the pipe and the surface medium is: ； ； in, Nu o,x For external convection heat transfer, the Nusselt number is... Ra x The Rayleigh number represents the heat transfer rate of natural convection outside the tube. g It is the acceleration due to gravity; ν is the coefficient of volumetric expansion. o Kinematic viscosity; α o Where is the thermal diffusivity, C o and n o It is a constant; This represents the average temperature of the outer wall of the pipe. The temperature of the medium on the outer surface of the pipe; For standard dimensions; When the surface medium outside the pipe is in a flowing state, the forced convection Nusselt number between the outer wall of the pipe and the surface medium is: ； ； in, Re o The Reynolds number for external convection heat transfer; Pr fo The Prandtl number of the surface medium; Pr wo,x The Prandt number is the surface medium at the outer wall of the pipe. d o Indicates the outer diameter of the pipe. u h This indicates the average flow velocity of the surface medium.

7. A system for iteratively calculating the inner and outer wall temperatures of a water source heat pump heat exchanger, based on the iterative calculation method for the inner and outer wall temperatures of a water source heat pump heat exchanger as described in claim 1, characterized in that... include: The data acquisition module is configured to collect basic data of the heat exchanger under stable operating conditions. The pipe data calculation module is configured to select the corresponding first-order correlation to calculate the Nusselt number of convective heat transfer in the pipe based on the basic data according to the flow regime type of the fluid in the pipe; the flow regime type includes laminar flow, transitional flow, and turbulent flow; The external data calculation module is configured to select the corresponding second-order correlation to calculate the Nusselt number of external convective heat transfer based on the basic data according to the heat transfer type of the medium on the external surface of the pipe; the heat transfer type includes natural convection in a static state and forced convection in a flowing state; The heat transfer coefficient calculation module is configured to calculate the convective heat transfer coefficients of the inner and outer walls of the pipe based on the Nusselt numbers inside and outside the pipe, respectively. The iterative calculation module is configured to iteratively calculate the inner and outer wall temperatures of the pipe using the heat balance equation, and recalculate the physical properties and convective heat transfer coefficients based on the updated temperature values ​​until the calculated inner and outer wall temperatures meet the preset target values.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps in the iterative calculation method for the inner and outer wall temperatures of a water source heat pump heat exchanger as described in any one of claims 1-6.

9. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps in the iterative calculation method for the inner and outer wall temperatures of a water source heat pump heat exchanger as described in any one of claims 1-6.

Images