Round pipeline laminar flow calculation method, calculation system and water supply and heat supply measuring device

Abstract

The invention provides a circular pipeline laminar flow calculation method and system and a water supply and heat supply measuring device.The method comprises the steps that cylindrical fluid infinitesimal elements which are coaxial with a circular pipeline and equal to the circular pipeline in length are taken from the circular pipeline, and stress analysis is conducted on the cylindrical fluid infinitesimal elements to obtain a shear stress expression on the side wall of the cylindrical fluid infinitesimal elements; obtaining a differential relation between the speed and the radius according to a shear stress expression and a Newton internal friction law; integrating the differential relation according to the inner radius of the circular pipeline and the velocity of the fluid mass point on the inner wall of the circular pipeline to obtain velocity distribution; and calculating the flow based on the speed distribution according to the inner radius and the length of the circular pipeline, the pressure on the two end surfaces and the viscosity and the density of the fluid. According to the technical scheme, the technical problems that in the prior art, due to the fact that a large number of flow meters are additionally connected in long-distance pipeline transportation, the load of a transportation power source is increased, and measurement of water meters and heat meters in the water supply and heating field is inaccurate are solved.

Description

Technical Field

[0001] The invention relates to the technical field of liquid pipeline transportation and water meter and heat meter measurement, and in particular to a circular pipeline laminar flow calculation method, a calculation system and a water supply and heating measurement device. Background Art

[0002] In the field of liquid pipeline transportation, it is often necessary to measure the flow rate of each transportation section to determine whether there is liquid leakage or loss in a certain section; or to measure the flow rate of a certain transportation branch to determine the liquid transportation volume. The conventional flow measurement method is to use instruments and equipment such as turbine flowmeters and Coriolis flowmeters. However, turbine flowmeters or Coriolis flowmeters inevitably require additional equipment to be connected to the pipeline. If the liquid pipeline transportation distance is long, the number of measuring devices connected to the transportation system increases, which increases the complexity of the transportation system, increases the total flow resistance of liquid transportation, and increases the load requirements of the transportation power source, causing many adverse effects on pipeline transportation work. If the pipeline flow can be obtained without installing a flowmeter, it will greatly increase the convenience of pipeline transportation work. The patent of this invention provides a feasible method for the above needs.

[0003] In addition, in the field of water supply and heating, ultrasonic water meters or heat meters are widely used to measure the flow of water supply and heating pipelines or the flow into the district and households. As the system and mechanism of water supply and heating metering supervision are gradually improved, the measurement accuracy requirements for water meters and heat meters are getting higher and higher. The common technical problem faced by current water meters and heat meters is that the measurement data of water meters and heat meters under laminar flow conditions are inaccurate. This is because the water flow rate under laminar flow is small, so small that it is close to the minimum resolution unit of the measuring instrument. The percentage error caused by the measurement under this low-speed laminar flow state can determine the accuracy level of the water meter or heat meter. In the field of water meters and heat meters, how to obtain accurate flow data under low-speed laminar flow conditions is an urgent problem to be solved. The patent of this invention provides a feasible method for the above problem. Summary of the invention

[0004] The present invention provides a circular pipe laminar flow calculation method, a calculation system and a water supply and heating measurement device, which can solve the technical problems in the prior art that a large number of additional flow meters connected in long-distance pipeline transportation lead to an increase in the load of the transmission power source and inaccurate measurement of water meters and heat meters in the water supply and heating field.

[0005] According to one aspect of the present invention, a method for calculating laminar flow in a circular pipe is provided, the method comprising:

[0006] Obtain the length of the circular pipe, the pressure on both end surfaces of the circular pipe, the inner radius of the circular pipe, and the viscosity and density of the fluid in the circular pipe;

[0007] Take a cylindrical fluid microelement coaxial with the circular pipe and equal to the length of the circular pipe from the circular pipe, and perform force analysis on the fluid microelement to obtain the shear stress expression on the side wall of the fluid microelement;

[0008] The differential relationship between velocity and radius is obtained based on the shear stress expression and Newton's law of internal friction;

[0009] Integrate the differential relationship between the velocity and the radius obtained above according to the inner radius of the circular pipe and the velocity of the fluid particles on the inner wall of the circular pipe to obtain the velocity distribution of the laminar flow of the fluid in the circular pipe;

[0010] Based on the velocity distribution, the flow rate of the fluid is calculated according to the inner radius of the circular pipe, the length of the circular pipe, the pressure on the two end surfaces of the circular pipe, and the viscosity and density of the fluid in the circular pipe.

[0011] Furthermore, the shear stress expression on the side wall of the fluid microelement is:

[0012]

[0013] In the above formula, τ represents the shear stress on the side wall of the fluid element, l represents the length of the fluid element, p1 and p2 represent the pressure on the two end surfaces of the fluid element, and r represents the cross-sectional radius of the fluid element.

[0014] Furthermore, the differential relationship between velocity and radius is:

[0015]

[0016] In the above formula, v represents the velocity of the fluid particle at the radius r on the cross section of the circular pipe, and μ represents the viscosity of the fluid in the circular pipe.

[0017] Furthermore, the velocity distribution of the laminar flow of the fluid in the circular pipe is:

[0018]

[0019] In the above formula, r max Indicates the inner radius of a circular pipe.

[0020] Furthermore, the flow rate of the fluid is calculated based on the velocity distribution according to the inner radius of the circular pipe, the length of the circular pipe, the pressure on both end surfaces of the circular pipe, and the viscosity and density of the fluid in the circular pipe by the following formula:

[0021]

[0022] In the above formula, Q represents the flow rate of the fluid, and ρ represents the density of the fluid in the circular pipe.

[0023] According to another aspect of the present invention, a circular pipe laminar flow calculation system is provided, the system comprising a data acquisition unit, a differential model building unit, a velocity distribution calculation unit and a flow calculation unit;

[0024] The data acquisition unit is used to acquire the length of the circular pipe, the pressure on both end surfaces of the circular pipe, the inner radius of the circular pipe, and the viscosity and density of the fluid in the circular pipe;

[0025] The differential model building unit is used to take a cylindrical fluid microelement coaxial with the circular pipe and having the same length as the circular pipe from the circular pipe, and perform force analysis on the fluid microelement to obtain the shear stress expression on the side wall of the fluid microelement; the differential relationship between the velocity and the radius is obtained according to the shear stress expression and Newton's law of internal friction;

[0026] The velocity distribution calculation unit is used to integrate the differential relationship between the velocity and the radius obtained above according to the inner radius of the circular pipe and the velocity of the fluid particles on the inner wall of the circular pipe to obtain the velocity distribution of the laminar flow of the fluid in the circular pipe;

[0027] The flow calculation unit is used to calculate the flow rate of the fluid based on the velocity distribution, the inner radius of the circular pipe, the length of the circular pipe, the pressure on the two end surfaces of the circular pipe, and the viscosity and density of the fluid in the circular pipe.

[0028] According to another aspect of the present invention, a water supply measuring device is provided, and the water supply measuring device includes the circular pipe laminar flow calculation system proposed in the present invention.

[0029] According to another aspect of the present invention, a heating measurement device is provided, and the heating measurement device includes the circular pipe laminar flow calculation system proposed in the present invention.

[0030] The technical scheme of the present invention is applied to provide a circular pipe laminar flow calculation method, calculation system and water supply and heating measurement device. The method extracts fluid microelement coaxial with the circular pipe and equal in length from the laminar fluid in the circular pipe, performs force analysis on the fluid microelement to obtain the shear force expression on the side wall of the fluid microelement, and then combines Newton's law of internal friction to obtain the differential relationship between velocity and radius. Based on this differential relationship, the velocity distribution and fluid flow of the laminar flow in the circular pipe can be obtained by integration. Using this method, only the length of the pipe and the pressure or pressure difference at the corresponding two ends need to be measured to calculate the precise value of the velocity distribution and flow. The method has high calculation accuracy for laminar fluids, and does not require additional flowmeters or other equipment that will increase the total flow resistance in the pipeline. The method is applied to long-distance pipeline transportation, which can increase the convenience of pipeline transportation and greatly reduce the load requirements on the power source of the transmission. The method is applied to the field of water supply and heating, which can correct and improve the speed and flow measurement algorithms of ultrasonic water meters and heat meters, and improve the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The included drawings are used to provide a further understanding of the embodiments of the present invention, which constitute a part of the specification, are used to illustrate the embodiments of the present invention, and together with the text description, explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0032] Figure 1 A schematic flow chart of a circular pipe laminar flow calculation method according to a specific embodiment of the present invention is shown;

[0033] Figure 2 A schematic diagram of the force of a microelement of a fluid in a laminar circular tube according to a specific embodiment of the present invention is shown;

[0034] Figure 3 A grid diagram of pressure distribution along the entire pipeline provided according to a specific embodiment of the present invention is shown;

[0035] Figure 4 Shows Figure 3 Schematic diagram of the relative position relationship between the upper section 1 and the section 2 of the middle pipe;

[0036] Figure 5 The structure block diagram of the circular pipe laminar flow calculation system provided according to a specific embodiment of the present invention is shown. DETAILED DESCRIPTION

[0037] It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0039] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0040] like Figure 1 As shown, according to a specific embodiment of the present invention, a method for calculating laminar flow rate in a circular pipe is provided, the method comprising:

[0041] S1, obtain the length of the circular pipe, the pressure on both end surfaces of the circular pipe, the inner radius of the circular pipe, and the viscosity and density of the fluid in the circular pipe;

[0042] S2, take a cylindrical fluid microelement coaxial with the circular pipe and equal to the length of the circular pipe from the circular pipe, and perform force analysis on the fluid microelement to obtain the shear stress expression on the side wall of the fluid microelement;

[0043] S3, the differential relationship between velocity and radius is obtained based on the shear stress expression and Newton's law of internal friction;

[0044] S4, integrating the differential relationship between the velocity and the radius obtained above according to the inner radius of the circular pipe and the velocity of the fluid particles on the inner wall of the circular pipe to obtain the velocity distribution of the laminar flow of the fluid in the circular pipe;

[0045] S5, based on the velocity distribution, the flow rate of the fluid is calculated according to the inner radius of the circular pipe, the length of the circular pipe, the pressure on the two end surfaces of the circular pipe, and the viscosity and density of the fluid in the circular pipe.

[0046] In the present invention, the length of the circular pipe and the pressure at both end faces are determined according to the flow calculation requirements. For example, if the flow of the entire circular pipe length is to be calculated, the length of the circular pipe refers to the length of the entire pipe, and accordingly, the pressure at both end faces refers to the pressure at both end faces of the entire pipe. If the flow of a certain distance in the entire circular pipe is to be calculated, the length of the circular pipe refers to the length of the distance in the pipe, and accordingly, the pressure at both end faces refers to the pressure at both end faces of the distance. In addition, since the cylindrical fluid microelement is coaxial with the circular pipe and has the same length as the circular pipe, the length of the cylindrical fluid microelement and the pressure at both end faces are equal to the length of the circular pipe and the pressure at both end faces, respectively.

[0047] By using this configuration, a circular pipe laminar flow calculation method is provided. The method extracts a fluid microelement coaxial with the circular pipe and of equal length from the laminar fluid in the circular pipe, performs a force analysis on the fluid microelement to obtain the shear force expression on the side wall of the fluid microelement, and then combines Newton's law of internal friction to obtain the differential relationship between velocity and radius. Based on this differential relationship, the velocity distribution and fluid flow rate of the laminar flow in the circular pipe can be obtained by integration. Using this method, only the length of the pipe and the pressure or pressure difference at the corresponding two ends need to be measured to calculate the precise value of the velocity distribution and flow rate. This method has high calculation accuracy for laminar fluids, and does not require additional flow meters or other equipment that will increase the total flow resistance in the pipeline. The method is applied to long-distance pipeline transportation, which can increase the convenience of pipeline transportation and greatly reduce the load requirements on the power source of the transmission. The method is applied to the field of water supply and heating, which can correct and improve the velocity and flow measurement algorithms of ultrasonic water meters and heat meters, and improve the measurement accuracy. Compared with the prior art, the technical solution of the present invention can solve the technical problems in the prior art that a large number of additional flow meters connected in long-distance pipeline transportation lead to an increase in the load of the transmission power source and inaccurate measurement of water meters and heat meters in the water supply and heating fields.

[0048] In the present invention, the shear stress on the side wall of the fluid microelement is the shear force per unit area on the side wall of the fluid microelement. Figure 2 In one embodiment of the present invention, in a circular pipe of equal cross-section filled with liquid, the radius of the circular pipe is r max A small fluid cylinder (cylindrical fluid microelement) is taken from the circular pipe for force analysis. The center line of the small cylinder coincides with the center line of the circular pipe. The cross-sectional radius of the small cylinder is r, and the length is equal to the length of the circular pipe, both of which are l.

[0049] The two circular surfaces (end surfaces) at both ends of the fluid cylinder are squeezed by the surrounding fluid. Assuming that the pressure on the left circular surface is p1 (unit Pa) and the pressure on the right circular surface is p2 (unit Pa), the forces on the two circular surfaces on the left and right sides are p1πr 2(unit N), p2πr 2 (Unit: N). In addition, due to the velocity difference between the fluid layers, the side wall of the small fluid cylinder is subjected to the shear stress τ (unit: Pa) of the outer fluid, so the flow resistance caused by the shear stress is τ2πrl (unit: N). All the forces on the small fluid cylinder in the pipe flow have been listed. Since the fluid body is incompressible and the flow is steady, the fluid is in a state of force balance at this time, that is:

[0050] p1πr 2 -p2πr 2 -τ2πrl=0 (1)

[0051] After simplification, the shear stress expression on the side wall of the fluid microelement is obtained as follows:

[0052]

[0053] In the above formula, τ represents the shear stress on the side wall of the fluid element, l represents the length of the fluid element, p1 and p2 represent the pressure on the two end surfaces of the fluid element, and r represents the cross-sectional radius of the fluid element.

[0054] Furthermore, in the embodiment of the present invention, the laminar fluid in the circular pipe is a Newtonian fluid, including but not limited to water, which complies with Newton's friction law of the fluid. Based on this, in another embodiment of the present invention, the force analysis of the fluid in the circular pipe is performed according to Newton's friction law of the fluid. Specifically, the shear stress of the fluid in the circular pipe is directly determined by the velocity gradient between the fluid layers per unit distance, and thus it can be obtained:

[0055]

[0056] Among them, v represents the velocity of the fluid particle at the radius r on the cross section of the circular pipe, and μ represents the viscosity of the fluid in the circular pipe, which is related to the fluid temperature.

[0057] Combining equation (2) and equation (3) we can get:

[0058]

[0059] Multiplying both sides of the equal sign in equation (4) by dr and dividing the viscosity μ by the right side of the equal sign, we can get the differential relationship between velocity and radius as follows:

[0060]

[0061] Formula (5) is an integrable form. Based on this embodiment, in the embodiment of the present invention, the velocity v on the left side of the equal sign is integrated, and the radius r on the right side is integrated. Specifically, the velocity of the fluid particle on the inner wall of the circular pipe is 0, and the inner radius of the circular pipe is r. max, for equation (5), the radius of the current cross section of the cylindrical fluid element is from the wall of the circular pipe (with an inner radius of r max ), that is, integrate from the center of the cross section of the circular pipe to the wall, integrate the velocity from v to 0, and integrate the radius from r to the inner radius r of the pipe. max , we get the following formula:

[0062]

[0063] By directly calculating the definite integral of formula (6), we can obtain the velocity distribution of the laminar flow of the fluid in the circular pipe:

[0064]

[0065] Formula (7) is the velocity distribution of laminar flow, where the pressures p1 (unit Pa) and p2 (unit Pa) at both ends of the circular pipe can be measured by a pressure gauge, r max is the known inner radius of the circular pipe, μ is the viscosity of water at any temperature, which can be found in the NIST database or other engineering manuals, and l is the length of the circular pipe. It should be noted that the pressures p1 and p2 at both ends of the circular pipe are directly related to the selection of the pipe length l. Through formula (7), the velocity v at any radius r on the cross section of the circular pipe can be obtained.

[0066] Furthermore, the velocity distribution of formula (7) is integrated over the entire circular pipe cross section and then multiplied by the density to obtain a mass flow calculation formula. That is, in the embodiment of the present invention, the flow rate of the fluid is calculated based on the velocity distribution according to the inner radius of the circular pipe, the length of the circular pipe, the pressure on the two end surfaces of the circular pipe, and the viscosity and density of the fluid in the circular pipe by the following formula:

[0067]

[0068] In the above formula, Q represents the flow rate of the fluid, which is the mass flow rate, and ρ represents the density of the fluid in the circular pipe. According to this calculation formula, the density, the radius of the pipe cross section, the viscosity of the working fluid, etc. are all traceable or known quantities. It is only necessary to know the pressure difference p1-p2 at any circular pipe length l to accurately calculate the mass flow rate of the circular pipe laminar flow, without the need to use a mass flow meter for flow measurement.

[0069] In order to prove the rationality of the theoretical method of this patent, certain verification methods are needed. The verification occasion is to pass water inside a circular cross-section pipe with a diameter of 50mm and a length of 10m. At 25℃, the volume flow rate is 0.15m 3 / h (converted into mass flow rate: 0.04156333kg / s).

[0070] A circular pipe model with a length of 10 m and a diameter of 50 mm was established in Ansys. After the mesh was divided in ICEM, the following Figure 3 The flow process is simulated in Fluent, and the pressure distribution along the pipeline during the flow process is extracted from the calculation results as shown in Figure 3 As shown. A section of the 10m long pipeline was extracted for analysis, as shown Figure 4 As shown, the static pressure at section 2 is 500000Pa, the static pressure at the upstream section 1 one meter away from section 2 is 500000.25Pa, and the pressure loss along the way from section 1 to section 2 is 0.25Pa.

[0071] According to the method given in this patent, to obtain the flow rate of the pipeline, it is only necessary to know the pressure loss p1-p2 along the pipeline with a length of l. Therefore, according to formula (8), the following can be obtained:

[0072]

[0073] Compared with the actual given flow rate 0.15m 3 / h (converted into mass flow rate is 0.04156333kg / s), the error is less than one percent, which is higher than the measurement accuracy of ordinary mass flow instruments on the market. This result proves that the theoretical method proposed in this patent is reasonable and feasible.

[0074]

[0075] Please refer to Figure 5 , According to another aspect of the present invention, a circular pipe laminar flow calculation system is provided, the system comprising a data acquisition unit, a differential model building unit, a velocity distribution calculation unit and a flow calculation unit;

[0076] The data acquisition unit is used to acquire the length of the circular pipe, the pressure on both end surfaces of the circular pipe, the inner radius of the circular pipe, and the viscosity and density of the fluid in the circular pipe;

[0077] The differential model building unit is used to take a cylindrical fluid microelement coaxial with the circular pipe and having the same length as the circular pipe from the circular pipe, and perform force analysis on the fluid microelement to obtain the shear stress expression on the side wall of the fluid microelement; the differential relationship between the velocity and the radius is obtained according to the shear stress expression and Newton's law of internal friction;

[0078] The velocity distribution calculation unit is used to integrate the differential relationship between the velocity and the radius obtained above according to the inner radius of the circular pipe and the velocity of the fluid particles on the inner wall of the circular pipe to obtain the velocity distribution of the laminar flow of the fluid in the circular pipe;

[0079] The flow calculation unit is used to calculate the flow rate of the fluid based on the velocity distribution, the inner radius of the circular pipe, the length of the circular pipe, the pressure on the two end surfaces of the circular pipe, and the viscosity and density of the fluid in the circular pipe.

[0080] Using this system, it is only necessary to measure the length of the pipeline and the pressure or pressure difference at the corresponding two ends to calculate the precise values ​​of the velocity distribution and flow rate. This method has high calculation accuracy for laminar fluids and does not require additional flow meters or other equipment in the pipeline that will increase the total flow resistance. Applying this method to long-distance pipeline transportation can increase the convenience of pipeline transportation and significantly reduce the load requirements on the transmission power source. Applying this method to the water supply and heating field can correct and improve the velocity and flow measurement algorithms of ultrasonic water meters and heat meters, and improve measurement accuracy.

[0081] According to another aspect of the present invention, a water supply measuring device is provided, which includes the circular pipe laminar flow calculation system proposed in the present invention. Since the circular pipe laminar flow calculation system proposed in the present invention can accurately calculate the velocity distribution and flow of the laminar fluid, the system is applied to water supply measuring devices such as water meters, which can significantly improve the measurement accuracy.

[0082] According to another aspect of the present invention, a heating measurement device is provided, the heating measurement device comprising the circular pipe laminar flow calculation system proposed in the present invention. Since the circular pipe laminar flow calculation system proposed in the present invention can accurately calculate the velocity distribution and flow of the laminar fluid, the system is applied to heating measurement devices such as heat meters, which can significantly improve the measurement accuracy.

[0083] In summary, the present invention provides a circular pipe laminar flow calculation method, calculation system and water supply and heating measurement device. The method extracts fluid microelement coaxial with the circular pipe and equal in length from the laminar fluid in the circular pipe, performs force analysis on the fluid microelement to obtain the shear force expression on the side wall of the fluid microelement, and then combines Newton's law of internal friction to obtain the differential relationship between velocity and radius. Based on this differential relationship, the velocity distribution and fluid flow rate of the laminar flow in the circular pipe can be obtained by integration. Using this method, only the length of the pipe and the pressure or pressure difference at the corresponding two ends need to be measured to calculate the precise value of the velocity distribution and flow rate. The method has high calculation accuracy for laminar fluids, and does not require additional flowmeters or other equipment that will increase the total flow resistance in the pipeline. The method is applied to long-distance pipeline transportation, which can increase the convenience of pipeline transportation and greatly reduce the load requirements on the power source of the transmission. The method is applied to the field of water supply and heating, which can correct and improve the speed and flow measurement algorithms of ultrasonic water meters and heat meters, and improve the measurement accuracy. Compared with the prior art, the technical solution of the present invention can solve the technical problems in the prior art that a large number of additional flow meters connected in long-distance pipeline transportation lead to an increase in the load of the transmission power source and inaccurate measurement of water meters and heat meters in the water supply and heating fields.

[0084] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0085] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0086] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for calculating laminar flow in a circular pipe, characterized in that: The method comprises: Obtain the length of the circular pipe, the pressure on both end surfaces of the circular pipe, the inner radius of the circular pipe, and the viscosity and density of the fluid in the circular pipe; Take a cylindrical fluid microelement from the circular pipe that is coaxial with the circular pipe and has the same length as the circular pipe, and perform a force analysis on the fluid microelement to obtain a shear stress expression on the side wall of the fluid microelement; The differential relationship between velocity and radius is obtained according to the shear stress expression and Newton's law of internal friction; Integrating the differential relationship between the velocity and the radius obtained above according to the inner radius of the circular pipe and the velocity of the fluid particles on the inner wall of the circular pipe to obtain the velocity distribution of the laminar flow of the fluid in the circular pipe; The flow rate of the fluid is calculated based on the velocity distribution according to the inner radius of the circular pipe, the length of the circular pipe, the pressure on both end surfaces of the circular pipe, and the viscosity and density of the fluid in the circular pipe.

2. The method according to claim 1, characterized in that The shear stress expression on the side wall of the fluid microelement is: In the above formula, τ represents the shear stress on the side wall of the fluid element, l represents the length of the fluid element, p1 and p2 represent the pressure on the two end surfaces of the fluid element, and r represents the cross-sectional radius of the fluid element.

3. The method according to claim 2, characterized in that The differential relationship between speed and radius is: In the above formula, v represents the velocity of the fluid particle at the radius r on the cross section of the circular pipe, and μ represents the viscosity of the fluid in the circular pipe.

4. The method according to claim 3, characterized in that The velocity distribution of the laminar flow of the fluid in the circular pipe is: In the above formula, r max Indicates the inner radius of a circular pipe.

5. The method according to claim 4, characterized in that The flow rate of the fluid is calculated based on the velocity distribution according to the inner radius of the circular pipe, the length of the circular pipe, the pressure on both end surfaces of the circular pipe, and the viscosity and density of the fluid in the circular pipe by the following formula: In the above formula, Q represents the flow rate of the fluid, and ρ represents the density of the fluid in the circular pipe.

6. A circular pipe laminar flow calculation system, characterized in that: The system includes a data acquisition unit, a differential model building unit, a velocity distribution calculation unit and a flow calculation unit; The data acquisition unit is used to acquire the length of the circular pipe, the pressure on both end surfaces of the circular pipe, the inner radius of the circular pipe, and the viscosity and density of the fluid in the circular pipe; The differential model building unit is used to take a cylindrical fluid microelement coaxial with the circular pipe and having the same length as the circular pipe from the circular pipe, perform force analysis on the fluid microelement to obtain a shear stress expression on the side wall of the fluid microelement; and obtain a differential relationship between velocity and radius according to the shear stress expression and Newton's law of internal friction; The velocity distribution calculation unit is used to integrate the differential relationship between the velocity and the radius obtained above according to the inner radius of the circular pipe and the velocity of the fluid particles on the inner wall of the circular pipe to obtain the velocity distribution of the laminar flow of the fluid in the circular pipe; The flow calculation unit is used to calculate the flow rate of the fluid based on the velocity distribution according to the inner radius of the circular pipe, the length of the circular pipe, the pressure on both end surfaces of the circular pipe, and the viscosity and density of the fluid in the circular pipe.

7. A water supply measuring device, characterized in that: The water supply measuring device includes the circular pipe laminar flow calculation system according to claim 6.

8. A heating measurement device, characterized in that: The heating measurement device includes the circular pipe laminar flow calculation system described in claim 6.

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