A method for calculating pressure loss of diverter tee based on vortex energy and its application

Abstract

The present invention discloses a method and application for calculating the pressure loss of a diverter tee based on vortex energy, which belongs to the field of construction and energy loss measurement technology. For a rectangular floor structure with a hollow interior, ventilation holes are respectively opened on the three adjacent sides of the floor, thereby forming a diverter tee hollow floor cavity or a right-angle diverter tee hollow floor cavity in the hollow floor, one air outlet is at a right angle to the air inlet, and the other air outlet is at a 180° right angle to the air inlet, which is a right-angle diverter tee cavity; by calculating the total pressure loss caused by the vortex in the cavity and correcting it with a coefficient, the pressure losses of each inlet and outlet of the right-angle diverter tee cavity and the right-angle diverter tee cavity can be respectively obtained. The direct relationship between the parameters can be directly reflected by the formula, thereby avoiding time-consuming numerical simulations and tedious and complicated experiments. It has good innovative ideas and is suitable for simple calculations in engineering design.

Description

Technical Field

[0001] The present invention belongs to the technical field of construction and energy loss measurement, and in particular relates to a method for calculating the pressure loss of a diverter tee based on eddy energy and its application. Background Art

[0002] In actual engineering, diverter tee cavities are widely used in other fire protection engineering and fluid engineering fields, such as cavity floor smoke exhaust and cavity floor ventilation. During operation, fluid flows into the cavity from the inlet end and, after complex fluid movement within the cavity, flows out through two outlets. If the adjacent hollow floor slabs have one air inlet and two air outlets, and both air outlets are at right angles to the air inlet, it is a right-angle converging tee cavity. If one air outlet is at right angles to the air inlet and the other is at a 180° right angle to the air inlet, it is a right-angle converging tee cavity.

[0003] Currently, a common method for determining energy loss in a diverter tee cavity is to couple fluid mechanics with calculus. However, analysis of energy loss in diverter tees has been limited to numerical software simulations and experimental measurements, with no theoretical research conducted. Furthermore, due to the cumbersome numerical simulation steps and complex experimental design, distortion in numerical experiments, and inaccurate measurement instruments, these two methods are highly unstable and have significant drawbacks. Summary of the Invention

[0004] The purpose of the present invention is to propose a method and application for calculating the pressure loss of a diverter tee based on vortex energy, so as to fill the theoretical gap in the pressure loss calculation results of the cavities of straight-angle and right-angle diverter tees, thereby taking relevant measures to accurately design the inlet and outlet pressure differences and facilitate construction.

[0005] To achieve the above-mentioned purpose, the present invention provides a method for calculating the pressure loss of a diverter tee based on vortex energy. For a rectangular floor structure with a hollow interior, ventilation holes are respectively opened on the three adjacent sides of the floor, thereby forming a diverter tee hollow floor in the hollow floor, wherein one of the three ventilation holes is an air inlet and the other two are air outlets. When the two air outlets are at right angles to the air inlet, it is a right-angle diverter tee cavity. If one air outlet is at right angles to the air inlet and the other air outlet is at a 180° right angle to the air inlet, it is a right-angle diverter tee cavity. By calculating the total pressure loss caused by the vortex in the cavity and correcting it with the coefficient, the pressure losses of each inlet and outlet of the right-angle diverter tee cavity and the right-angle diverter tee cavity can be respectively obtained.

[0006] The specific steps are as follows:

[0007] As the airflow enters from an air inlet of the hollow floor slab with a diverter tee and is subsequently discharged from two air outlets, four vortex areas are formed near the four corners in the cavity of the hollow floor slab. The cylindrical vortices in the four vortex areas fill the entire vortex area. The four vortices are cylindrical vortex A, cylindrical vortex A', cylindrical vortex B, and cylindrical vortex B'. Cylindrical vortex A and cylindrical vortex A' are respectively arranged on both sides of the air inlet, while cylindrical vortex B and cylindrical vortex B' are located on the other two sides of the hollow floor slab, symmetrical to cylindrical vortex A and cylindrical vortex A'.

[0008] Assuming that the pressure loss in the cavity is caused by cylindrical vortices, the pressure loss in a single cylindrical vortex is first derived, and then the pressure loss in four cylindrical vortices is derived. The cylindrical vortex only rotates in the plane direction and does not rotate in the axial direction. The energy loss calculation method in the infinitesimal arc inside the cylindrical vortex of the fluid is determined using Newton's law of internal friction in fluid mechanics.

[0009] A method for calculating the total pressure loss of a fluid cylindrical vortex based on calculus.

[0010] The viscous energy loss in the cylindrical vortex A and cylindrical vortex A' regions is calculated based on the inlet velocity of the hollow slab cavity, the outlet velocity of the air outlet, and the cavity size.

[0011] The viscous energy loss in the cylindrical vortex B and cylindrical vortex B' regions is calculated based on the initial boundary value conditions;

[0012] Introduce the correction factor and calculate the total pressure loss in the cavity and the pressure loss at each outlet;

[0013] The straight-angle-to-right-angle pressure conversion coefficient is introduced into the straight-angle converging tee to calculate the total pressure loss in the cavity of the right-angle diverging tee and the pressure loss at each outlet.

[0014] Furthermore, a calculation method for determining the energy loss in the micro-arc within the fluid vortex based on Newton's law of internal friction in fluid mechanics includes:

[0015] Assume that the cylindrical vortex generated in the four vortex regions rotates only in the plane direction and does not rotate in the direction perpendicular to the plane. The thickness is H and the opening angle is dθ. In this micro-arc, the viscous energy loss is generated between the flow layers due to the relative motion of the flow layers, that is, the energy loss of the i-th micro-arc W 涡i , combined with Newton's law of internal friction, we know that W 涡i for:

[0016] W 涡i =F 摩擦i ·r·dθ

[0017] F 摩擦i =S i ·τ i

[0018] S i =dr·H

[0019] Among them, W 涡i represents the energy loss of the i-th micro-arc, F 摩擦i is the viscous force between the micro-arc fluid layers, r is the distance between the micro-arc and the vortex center, dθ is the micro-arc angle, S i is the area of ​​the infinitesimal arc subjected to viscous force, τ i is the viscous shear stress between flow layers, H is the thickness of the cylindrical vortex;

[0020] The Newton internal friction formula in the circular coordinate system is:

[0021]

[0022] v r =ω·r

[0023] Where: μ is the dynamic viscosity of the fluid, v r is the fluid velocity along the annular tangent direction, ω is the vortex angular velocity;

[0024] So we can get the energy loss of the infinitesimal arc W 涡i for:

[0025] W 涡i =Hμω·dr·r·dθ

[0026] Furthermore, the total pressure loss calculation method of the fluid vortex based on calculus is:

[0027] In the cavity cross-sectional flow field diagram, there is an obvious large vortex in each area. Due to the consistency of the cavity in height, the vortex formed is set as a cylindrical vortex. Only four large cylindrical vortices need to be calculated in the four areas: cylindrical vortex A, cylindrical vortex A', cylindrical vortex B, and cylindrical vortex B', and then correction coefficients are used for correction.

[0028] The pressure loss of the entire cylindrical vortex is regarded as the combination of the pressure losses of several micro-arcs. The total energy loss W can be obtained by integrating the energy loss of the micro-arcs through calculus method. 涡 for:

[0029]

[0030] Pressure loss ΔP caused by vortex 涡 and energy loss W 涡 The relationship between them is as follows:

[0031]

[0032] In the above formula, R is the average radius of the vortex, ρ is the fluid density, and g is the acceleration due to gravity;

[0033] By changing different cylindrical vortex radius parameters and angular velocities, the pressure losses of cylindrical vortex A, cylindrical vortex A', cylindrical vortex B, and cylindrical vortex B' can be calculated. Among them, cylindrical vortex A and cylindrical vortex A' are symmetrical, with consistent angular velocity and radius. The same is true for cylindrical vortex B and cylindrical vortex B'.

[0034] Furthermore, the basic arrangement pattern of the diverter tee cavity is determined and the four vortex areas to be analyzed, where the cylindrical vortex A, cylindrical vortex A', cylindrical vortex B, and cylindrical vortex B' are located, are divided into:

[0035] The energy loss caused by vortex is studied by taking the symmetrical right-angle diverter tee as the object. x1, x2, y1, y2 are respectively the distance from the left side of the air inlet to the left side of the cavity, the distance from the right side of the air inlet to the right side of the cavity, the distance from the lower side of the air outlet to the lower side of the cavity, and the distance from the upper side of the air inlet to the upper side of the cavity. Due to the symmetry of the cavity of the right-angle diverter tee, the relationship between the parameters is as follows:

[0036] x1=x2

[0037] y1=y2

[0038] Define the cylindrical vortex A, cylindrical vortex A', cylindrical vortex B, and cylindrical vortex B' generated in the internal vortex distribution of the flat-angle splitter tee cavity. The vortex radius R of cylindrical vortex A is A Expressed as Cylindrical vortex B vortex radius R B for Due to the symmetry of the diverter tee, the radii of cylindrical vortex A' and cylindrical vortex B' are:

[0039] Furthermore, the viscous energy loss of cylindrical vortex A and cylindrical vortex A' is determined based on the initial boundary value conditions, including:

[0040] The total viscous energy loss W of the cylindrical vortex A 涡A for:

[0041]

[0042] Here, the angular velocity ω of the cylindrical vortex A is A for:

[0043]

[0044] Where v0 is the inlet fluid velocity of the cavity, k A is the velocity conversion coefficient of the cylindrical vortex A, which is measured through previous experiments. Due to the symmetry of the cavity, the total viscous energy loss W of the cylindrical vortex A' can be obtained by the same logic. 涡A' for:

[0045]

[0046] Where, ω A' is the angular velocity of the cylindrical vortex A'.

[0047] Furthermore, based on the initial boundary value conditions, the viscous energy loss in the cylindrical vortex B and cylindrical vortex B' regions is determined as:

[0048] The total viscous energy loss W of the cylindrical vortex B 涡B for:

[0049]

[0050] Here, the angular velocity ω of the cylindrical vortex B is B for:

[0051]

[0052] Among them, k B is the velocity conversion coefficient of cylindrical vortex B, which is measured by experiment;

[0053] Due to the symmetry of the cavity, the total viscous energy loss W of the cylindrical vortex B' is similarly 涡B' for:

[0054]

[0055]

[0056] Where, ω B' is the angular velocity of the cylindrical vortex B'.

[0057] Furthermore, in the hollow floor slab with a right-angle diversion tee, the correction coefficient is used to calculate the total pressure loss in the cavity, and the pressure loss at each outlet of the cavity floor slab is calculated as follows:

[0058] The airflow enters the internal cavity from the air inlet of the hollow floor slab with a right angle diversion tee. Due to the thickness of the material of the hollow floor slab, a concealed pipe is provided between the air inlet and outlet of the floor slab and the cavity. The concealed pipe can be a rectangular structure or a multi-circular pipe structure. Since the size of the concealed pipe is significantly smaller than the size of the internal cavity of the floor slab, a significant sudden expansion phenomenon of the structure will occur. The pressure loss caused by the sudden expansion is W. e It indicates that when the air flows out of the cavity and into the blind pipe at the outlet, due to the difference in size between the outlet blind pipe and the cavity, an obvious sudden shrinkage phenomenon will occur. The total pressure loss caused by the sudden shrinkage at the two outlets of the cavity is W. r express;

[0059] In the cavity of the hollow floor, there is not only viscous energy loss caused by vortex, sudden expansion and contraction pressure loss, but also energy loss caused by fluid-wall friction. However, in the diverter tee cavity, the pressure loss caused by the latter is much smaller than the energy loss caused by vortex viscosity. Therefore, the total energy loss W in the diverter tee cavity is calculated by 平 The correction coefficient is introduced to make corrections as follows:

[0060] W 平 =K(W 涡A +W 涡A’ +W 涡B +W 涡B’ +W e +W r )

[0061] Among them, K is the energy loss correction coefficient, which needs to be measured through experiments;

[0062] The total pressure loss ΔP in the cavity of the right-angle diverter tee 平 for:

[0063]

[0064] Where ρ is the fluid density and g is the acceleration due to gravity.

[0065] Since the right-angle confluence tee cavity is bilaterally symmetrical, the energy losses from the inlet to the two outlets are W 平出1 、W 平出2 , pressure loss from inlet to outlet ΔP 平出1 , ΔP 平出2 as follows:

[0066]

[0067] Furthermore, when calculating the pressure loss of the right-angle split tee cavity, the right-angle split tee cavity is converted into a straight-angle split tee cavity under the same working conditions, and the pressure loss from the inlet to each outlet is calculated. Then, the straight-angle-right-angle correction coefficient is introduced to calculate the total pressure loss in the right-angle split tee cavity and the pressure loss at each outlet:

[0068] For the right-angle split tee cavity, the above complicated pressure loss calculation process is no longer repeated. Instead, the pressure loss of the right-angle split tee cavity under the same working condition is calculated by borrowing it. Then, the right-angle-to-right-angle coefficient conversion is performed to obtain the desired right-angle split tee cavity pressure loss; that is, the outlet concealed pipe parallel to the inlet concealed pipe is rotated 90 degrees to convert the original right-angle split tee cavity into a right-angle split tee cavity, which is called the right-angle split tee cavity under the same working condition.

[0069] The pressure losses at the two outlets of the right-angle diverter tee cavity under the same working conditions are related to the pressure losses at the outlets of the right-angle diverter tee cavity as follows:

[0070] ξ 下 ΔP 平出1 ≤ΔP 直出180° ≤ΔP 直出90° ≤ξ 上 ΔP 平出1 Among them, ξ 下 ,ξ 上 are the upper and lower critical conversion coefficients of straight angle to right angle, ΔP 直出180° is the pressure loss between the 180° outlet blind pipe and the inlet blind pipe, ΔP 直出90° The pressure loss between the 90° outlet blind pipe and the inlet blind pipe;

[0071] Furthermore, for a concrete right-angle diversion tee cavity floor slab with an absolute roughness of 0.7 mm, the upper and lower critical correction coefficients for the right angle to right angle are:

[0072] ξ 下 =0.93

[0073] ξ 上 =1.08

[0074] For diversion cavities made of different materials, the corresponding correction coefficients should be measured according to actual experiments.

[0075] An application of a vortex energy-based method for calculating the pressure loss of a diverter tee, and calculation of the equivalent energy loss length of the ventilation cavity floor according to different commonly used cavity structures for concealed pipe ventilation;

[0076] Cavity floor slabs often use various forms of cavities, including diversion tee cavities, when realizing ventilation and air-conditioning channel functions, including full straight cavities, right-angle turn cavities, converging tee cavities, right-angle diversion tee cavities, right-angle diversion tee cavities, and cavities at vents;

[0077] The pressure loss inside the cavity can be divided into the pressure loss along the way ΔP λ and local pressure loss ΔP η , where the pressure loss along the way is ΔP λ The occurrence of the viscous effect is due to the shear stress caused by the friction between the fluid and the wall, and the local pressure loss ΔP η It is mostly caused by a large curvature change in the shape of the fluid wall. The two methods for calculating pressure loss in fluid mechanics are as follows:

[0078]

[0079] Where λ is the drag coefficient along the path, l is the length along the path between the fluid and the wall, d is the flow velocity equivalent diameter of the fluid section, v is the flow velocity, and η is the local drag coefficient;

[0080] The main reasons for various forms of cavity internal pressure loss include: fluid sudden expansion pressure loss ΔP ηk , Fluid sudden contraction pressure loss ΔP ηs , pressure loss along the way ΔP λ , right-angle turn pressure loss ΔP ηz , converging tee pressure loss ΔP ηh , diversion tee pressure loss ΔP ηf Combining the above six pressure loss calculation methods, the total pressure loss of any cavity in different designs can be obtained as follows:

[0081]

[0082] Where n ηk is the number of sudden expansion pressure losses in the system, n ηs is the number of sudden pressure losses in the system, n ηz is the number of right-angle turns in the system, n ηh is the number of pressure losses in the converging tee in the system, n ηf is the number of pressure losses in the diversion tee in the system, n λ is the number of pressure losses along the system;

[0083] All local pressure losses are converted into pressure losses along the way, and the calculation method of the equivalent energy loss length of the ventilated cavity floor is proposed as follows.

[0084]

[0085] Where, l ηk (equivalent), l ηs (equivalent), l ηz (equivalent), l ηh (equivalent), l ηf (Equivalent) are the equivalent lengths of the fluid sudden expansion pressure loss, fluid sudden contraction pressure loss, right-angle turn pressure loss, converging tee pressure loss, and diverting tee pressure loss inside the floor cavity excluding the concealed pipe part, η k ,η s ,η z ,η h ,η f They are the local resistance coefficients of the fluid sudden expansion pressure loss, fluid sudden contraction pressure loss, right-angle turn pressure loss, converging tee pressure loss, and diverting tee pressure loss inside the floor cavity excluding the concealed pipe part, d 腔 is the constant flow equivalent diameter of the cavity, λ腔 is the longitudinal resistance coefficient in the cavity;

[0086] From the above, we can get the equivalent length l of the total local pressure loss in the floor cavity excluding the concealed pipe part η for:

[0087]

[0088] The equivalent length l of the pressure loss along the floor cavity excluding the concealed pipe part λ Equivalent to the cavity length l 腔 , so the equivalent length l of the total pressure loss in the floor cavity excluding the concealed pipe part 腔 (equivalent) to:

[0089] l 腔 (equivalent) = l η +l 腔

[0090] In addition, since there is no local pressure loss in the blind pipe and only pressure loss along the way, the equivalent length of the total pressure loss of the system composed of the blind pipe and the cavity is:

[0091] l 总 (equivalent) = l η +l 腔 +l 管

[0092] Beneficial effects: This method determines the energy loss calculation method in the infinitesimal arc within the fluid vortex based on Newton's law of internal friction in fluid mechanics; determines the total pressure loss calculation method of the fluid vortex based on the idea of ​​calculus; determines the basic arrangement pattern of the diversion tee cavity and divides the cavity into four vortex areas to be analyzed, namely cylindrical vortex A, cylindrical vortex A', cylindrical vortex B, and cylindrical vortex B'; determines the viscous energy loss of the cylindrical vortex A and cylindrical vortex A' based on the initial and boundary conditions; determines the viscous energy loss of the cylindrical vortex B and cylindrical vortex B' based on the initial and boundary conditions; introduces a correction coefficient and calculates the total pressure loss in the right-angle diversion tee cavity and the pressure loss at each outlet; introduces a right-angle-right-angle correction coefficient and calculates the total pressure loss in the right-angle diversion tee cavity and the pressure loss at each outlet. Compared with the limitations of traditional calculation methods, whose analysis approaches only include numerical software simulation and experiments, the present invention can predict and analyze the pressure loss of the diversion tee cavity under different boundary conditions at the theoretical level, and can directly reflect the direct relationship between various parameters through formulas, thereby avoiding time-consuming numerical simulation and tedious and complicated experiments. It has good innovative ideas and is suitable for simple calculations in engineering design. BRIEF DESCRIPTION OF THE DRAWINGS

[0093] Figure 1Schematic diagrams of a cylindrical vortex according to an embodiment of the present invention, wherein (a) is a plan view of the cylindrical vortex, and (b) is a three-dimensional view of the cylindrical vortex;

[0094] Figure 2 Schematic diagrams of the airflow in and out of a hollow floor slab with a diverter tee according to an embodiment of the present invention, wherein (a) is a schematic diagram of the airflow in and out of a hollow floor slab with a straight diverter tee, and (b) is a schematic diagram of the airflow in and out of a hollow floor slab with a right angle diverter tee;

[0095] Figure 3 Schematic diagrams of the airflow in and out of a hollow floor slab with a three-way splitter according to an embodiment of the present invention, wherein (a) is a schematic diagram of the airflow in and out of a hollow floor slab with a straight-angle splitter, and (b) is a schematic diagram of the airflow in and out of a hollow floor slab with a three-way splitter;

[0096] Figure 4 Schematic diagram of the distribution of cylindrical vortices in a cavity according to an embodiment of the present invention;

[0097] Figure 5 Schematic diagrams of the airflow in and out of the cavities of various hollow floor slabs with different inlets and outlets and three concealed pipes according to the present invention, wherein (a) is a schematic diagram of the airflow in and out of the vent cavity, (b) is a schematic diagram of the airflow in and out of the full vacuum cavity, (c) is a schematic diagram of the airflow in and out of the right-angle turn cavity, (d) is a schematic diagram of the airflow in and out of the cavity at the junction of the collecting pipe, (e) is a schematic diagram of the airflow in and out of the cavity of a right-angle split tee, and (f) is a schematic diagram of the airflow in and out of the cavity of a right-angle split tee.

[0098] Figure 6 Schematic diagram of the airflow in and out of the cavity of a three-way hollow floor slab matched with three concealed pipes according to an embodiment of the present invention, wherein (a) is a schematic diagram of the airflow in and out of a right-angle split tee; (b) is a schematic diagram of the airflow in and out of a flat-angle split tee under equal working conditions;

[0099] Figure 7 These are implementation steps of an embodiment of the present invention. DETAILED DESCRIPTION

[0100] The accompanying drawings, which constitute a part of this application, are used to provide a further understanding of the application:

[0101] like Figure 1 、 Figure 2 and Figure 3As shown, a method for calculating the pressure loss of a diverter tee based on vortex energy is provided. For a rectangular floor structure with a hollow interior, ventilation holes are respectively opened on the three adjacent sides of the floor, thereby forming a diverter tee hollow floor cavity in the hollow floor, wherein one of the three ventilation holes is an air inlet and the other two are air outlets. When both air outlets are at right angles to the air inlet, it is a right-angle diverter tee cavity. When one air outlet is at right angles to the air inlet and the other air outlet is at a 180° right angle to the air inlet, it is a right-angle diverter tee cavity. By calculating the total pressure loss caused by the vortex in the cavity and correcting it with the coefficient, the pressure losses at each inlet and outlet of the right-angle diverter tee cavity and the right-angle diverter tee cavity can be obtained respectively.

[0102] The specific steps are as follows:

[0103] like Figure 4 and Figure 7 As shown, since the air flow enters from an air inlet of the hollow floor slab of the diversion tee and is then discharged from the two air outlets, four vortex areas are formed in the cavity of the hollow floor slab near the four corners, and the cylindrical vortices in the four vortex areas fill the entire vortex area respectively. The four vortices are cylindrical vortex A, cylindrical vortex A', cylindrical vortex B, and cylindrical vortex B'; among them, cylindrical vortex A and cylindrical vortex A' are respectively arranged on both sides of the air inlet, and cylindrical vortex B and cylindrical vortex B' are located on the other two sides of the hollow floor slab, which are symmetrical to cylindrical vortex A and cylindrical vortex A'.

[0104] Assuming that the pressure loss in the cavity is caused by cylindrical vortices, the pressure loss in a single cylindrical vortex is first derived, and then the pressure loss in four cylindrical vortices is derived. The cylindrical vortex only rotates in the plane direction and does not rotate in the axial direction. The energy loss calculation method in the infinitesimal arc inside the cylindrical vortex of the fluid is determined using Newton's law of internal friction in fluid mechanics.

[0105] A method for calculating the total pressure loss of a fluid cylindrical vortex based on calculus.

[0106] The viscous energy loss in the cylindrical vortex A and cylindrical vortex A' regions is calculated based on the inlet velocity of the hollow slab cavity, the outlet velocity of the air outlet, and the cavity size.

[0107] The viscous energy loss in the cylindrical vortex B and cylindrical vortex B' regions is calculated based on the initial boundary value conditions;

[0108] Introduce the correction factor and calculate the total pressure loss in the cavity and the pressure loss at each outlet;

[0109] The straight-angle-to-right-angle pressure conversion coefficient is introduced into the straight-angle converging tee to calculate the total pressure loss in the cavity of the right-angle diverging tee and the pressure loss at each outlet.

[0110] The calculation method for determining the energy loss in the micro-arc within the fluid vortex based on Newton's law of internal friction in fluid mechanics includes:

[0111] Assume that the cylindrical vortex generated in the four vortex regions rotates only in the plane direction and does not rotate in the direction perpendicular to the plane. The thickness is H and the opening angle is dθ. In this micro-arc, the viscous energy loss is generated between the flow layers due to the relative motion of the flow layers, that is, the energy loss of the i-th micro-arc W 涡i , combined with Newton's law of internal friction, we know that W 涡i for:

[0112] W 涡i =F 摩擦i ·r·dθ

[0113] F 摩擦i =S i ·τ i

[0114] S i =dr·H

[0115] Among them, W 涡i represents the energy loss of the i-th micro-arc, F 摩擦i is the viscous force between the micro-arc fluid layers, r is the distance between the micro-arc and the vortex center, dθ is the micro-arc angle, S i is the area of ​​the infinitesimal arc subjected to viscous force, τ i is the viscous shear stress between flow layers, H is the thickness of the cylindrical vortex;

[0116] The Newton internal friction formula in the circular coordinate system is:

[0117]

[0118] v r =ω·r

[0119] Where: μ is the dynamic viscosity of the fluid, v r is the fluid velocity along the annular tangent direction, ω is the vortex angular velocity;

[0120] So we can get the energy loss of the infinitesimal arc W 涡i for:

[0121] W 涡i =Hμω·dr·r·dθ

[0122] The calculation method for determining the total pressure loss of a fluid vortex based on calculus is:

[0123] In the cavity cross-sectional flow field diagram, there is an obvious large vortex in each area. Due to the consistency of the cavity in height, the vortex formed is set as a cylindrical vortex. Only four large cylindrical vortices need to be calculated in the four areas: cylindrical vortex A, cylindrical vortex A', cylindrical vortex B, and cylindrical vortex B', and then correction coefficients are used for correction.

[0124] The pressure loss of the entire cylindrical vortex is regarded as the combination of the pressure losses of several micro-arcs. The total energy loss W can be obtained by integrating the energy loss of the micro-arcs through calculus method. 涡 for:

[0125]

[0126] Pressure loss ΔP caused by vortex 涡 and energy loss W 涡 The relationship between them is as follows:

[0127]

[0128] In the above formula, R is the average radius of the vortex, ρ is the fluid density, and g is the acceleration due to gravity;

[0129] By changing different cylindrical vortex radius parameters and angular velocities, the pressure losses of cylindrical vortex A, cylindrical vortex A', cylindrical vortex B, and cylindrical vortex B' can be calculated. Among them, cylindrical vortex A and cylindrical vortex A' are symmetrical, with consistent angular velocity and radius. The same is true for cylindrical vortex B and cylindrical vortex B'.

[0130] Determine the basic arrangement pattern of the diverter tee cavity and divide the four vortex areas to be analyzed, including cylindrical vortex A, cylindrical vortex A', cylindrical vortex B, and cylindrical vortex B' in the cavity:

[0131] The energy loss caused by vortex is studied by taking the symmetrical right-angle diverter tee as the object. x1, x2, y1, y2 are respectively the distance from the left side of the air inlet to the left side of the cavity, the distance from the right side of the air inlet to the right side of the cavity, the distance from the lower side of the air outlet to the lower side of the cavity, and the distance from the upper side of the air inlet to the upper side of the cavity. Due to the symmetry of the cavity of the right-angle diverter tee, the relationship between the parameters is as follows:

[0132] x1=x2

[0133] y1=y2

[0134] Define the cylindrical vortex A, cylindrical vortex A', cylindrical vortex B, and cylindrical vortex B' generated in the internal vortex distribution of the flat-angle splitter tee cavity. The vortex radius R of cylindrical vortex A is A Expressed as Cylindrical vortex B vortex radius R B for Due to the symmetry of the diverter tee, the radii of cylindrical vortex A' and cylindrical vortex B' are:

[0135] The viscous energy loss of cylindrical vortex A and cylindrical vortex A' determined based on initial and boundary conditions includes:

[0136] The total viscous energy loss W of the cylindrical vortex A 涡A for:

[0137]

[0138] Here, the angular velocity ω of the cylindrical vortex A is A for:

[0139]

[0140] Where v0 is the inlet fluid velocity of the cavity, k A is the velocity conversion coefficient of cylindrical vortex A, which is measured through previous experiments;

[0141] Due to the symmetry of the cavity, the total viscous energy loss W of the cylindrical vortex A' can be obtained by the same logic. 涡A' for:

[0142]

[0143] Where, ω A' is the angular velocity of the cylindrical vortex A'.

[0144] Based on the initial boundary value conditions, the viscous energy loss in the cylindrical vortex B and cylindrical vortex B' regions is determined as:

[0145] The total viscous energy loss W of the cylindrical vortex B 涡B for:

[0146]

[0147] Here, the angular velocity ω of the cylindrical vortex B is B for:

[0148]

[0149] Among them, k B is the velocity conversion coefficient of cylindrical vortex B, which is measured by experiment;

[0150] Due to the symmetry of the cavity, the total viscous energy loss W of the cylindrical vortex B' is similarly 涡B' for:

[0151]

[0152] Where, ω B' is the angular velocity of the cylindrical vortex B'.

[0153] In the hollow slab with a straight-angle diverter tee, the correction coefficient is used to calculate the total pressure loss in the cavity, and the pressure loss at each outlet of the cavity slab is calculated as follows:

[0154] The airflow enters the internal cavity from the air inlet of the hollow floor slab with a right angle diversion tee. Due to the thickness of the material of the hollow floor slab, a concealed pipe is provided between the air inlet and outlet of the floor slab and the cavity. The concealed pipe can be a rectangular structure or a multi-circular pipe structure. Since the size of the concealed pipe is significantly smaller than the size of the internal cavity of the floor slab, a significant sudden expansion phenomenon of the structure will occur. The pressure loss caused by the sudden expansion is W. e It indicates that when the air flows out of the cavity and into the blind pipe at the outlet, due to the difference in size between the outlet blind pipe and the cavity, an obvious sudden shrinkage phenomenon will occur. The total pressure loss caused by the sudden shrinkage at the two outlets of the cavity is W. r express;

[0155] In the cavity of the hollow floor, there is not only viscous energy loss caused by vortex, sudden expansion and contraction pressure loss, but also energy loss caused by fluid-wall friction. However, in the diverter tee cavity, the pressure loss caused by the latter is much smaller than the energy loss caused by vortex viscosity. Therefore, the total energy loss W in the diverter tee cavity is calculated by 平 The correction coefficient is introduced to make corrections as follows:

[0156] W 平 =K(W 涡A +W 涡A’ +W 涡B +W 涡B’ +W e +W r )

[0157] Among them, K is the energy loss correction coefficient, which needs to be measured through experiments;

[0158] The total pressure loss ΔP in the cavity of the right-angle diverter tee 平 for:

[0159]

[0160] Where ρ is the fluid density and g is the acceleration due to gravity.

[0161] Since the right-angle confluence tee cavity is bilaterally symmetrical, the energy losses from the inlet to the two outlets are W 平出1 、W 平出2 , pressure loss from inlet to outlet ΔP 平出1 , ΔP 平出2 as follows:

[0162]

[0163] When calculating the pressure loss of the right-angle split tee cavity, convert the right-angle split tee cavity into a straight-angle split tee cavity with the same working conditions, calculate the pressure loss from the inlet to each outlet, and then introduce the straight-angle-right-angle correction coefficient to calculate the total pressure loss in the right-angle split tee cavity and the pressure loss at each outlet:

[0164] For the right-angle split tee cavity, the above complicated pressure loss calculation process is no longer repeated. Instead, the pressure loss of the right-angle split tee cavity under the same working condition is calculated by borrowing it. Then, the right-angle-to-right-angle coefficient conversion is performed to obtain the desired right-angle split tee cavity pressure loss; that is, the outlet concealed pipe parallel to the inlet concealed pipe is rotated 90 degrees to convert the original right-angle split tee cavity into a right-angle split tee cavity, which is called the right-angle split tee cavity under the same working condition.

[0165] The pressure losses at the two outlets of the right-angle diverter tee cavity under the same working conditions are related to the pressure losses at the outlets of the right-angle diverter tee cavity as follows:

[0166] ξ 下 ΔP 平出1 ≤ΔP 直出180° ≤ΔP 直出90° ≤ξ 上 ΔP 平出1 Among them, ξ 下 ,ξ 上 are the upper and lower critical conversion coefficients of straight angle to right angle, ΔP 直出180° is the pressure loss between the 180° outlet blind pipe and the inlet blind pipe, ΔP 直出90° The pressure loss between the 90° outlet blind pipe and the inlet blind pipe;

[0167] For a concrete right-angle diversion tee cavity floor slab with an absolute roughness of 0.7 mm, the upper and lower critical correction coefficients for the right angle to right angle are:

[0168] ξ 下 =0.93

[0169] ξ 上 =1.08

[0170] For diversion cavities made of different materials, the corresponding correction coefficients should be measured according to actual experiments.

[0171] like Figure 5 and Figure 6 As shown in the figure, a method for calculating the pressure loss of a diverter tee based on vortex energy is applied to calculate the equivalent energy loss length of the ventilation cavity floor according to different commonly used cavity structures for concealed pipe ventilation.

[0172] Cavity floor slabs often use various forms of cavities, including diversion tee cavities, when realizing ventilation and air-conditioning channel functions, including full straight cavities, right-angle turn cavities, converging tee cavities, right-angle diversion tee cavities, right-angle diversion tee cavities, and cavities at vents;

[0173] The pressure loss inside the cavity can be divided into the pressure loss along the way ΔP λ and local pressure loss ΔP η , where the pressure loss along the way is ΔP λ The occurrence of the viscous effect is due to the shear stress caused by the friction between the fluid and the wall, and the local pressure loss ΔP η It is mostly caused by a large curvature change in the shape of the fluid wall. The two methods for calculating pressure loss in fluid mechanics are as follows:

[0174]

[0175] Where λ is the drag coefficient along the path, l is the length along the path between the fluid and the wall, d is the flow velocity equivalent diameter of the fluid section, v is the flow velocity, and η is the local drag coefficient;

[0176] The main reasons for various forms of cavity internal pressure loss include: fluid sudden expansion pressure loss ΔP ηk , Fluid sudden contraction pressure loss ΔP ηs , pressure loss along the way ΔP λ , right-angle turn pressure loss ΔP ηz , pressure loss of converging tee ΔP ηh , diversion tee pressure loss ΔP ηf Combining the above six pressure loss calculation methods, the total pressure loss of any cavity in different designs can be obtained as follows:

[0177]

[0178] Where n ηk is the number of sudden expansion pressure losses in the system, n ηs is the number of sudden pressure losses in the system, n ηz is the number of right-angle turns in the system, n ηh is the number of pressure losses in the converging tee in the system, n ηf is the number of pressure losses in the diversion tee in the system, n λ is the number of pressure losses along the system;

[0179] All local pressure losses are converted into pressure losses along the way, and the calculation method of the equivalent energy loss length of the ventilated cavity floor is proposed as follows.

[0180]

[0181] Where, l ηk (equivalent), l ηs (equivalent), l ηz (equivalent), l ηh (equivalent), l ηf (Equivalent) are the equivalent lengths of the fluid sudden expansion pressure loss, fluid sudden contraction pressure loss, right-angle turn pressure loss, converging tee pressure loss, and diverting tee pressure loss inside the floor cavity excluding the concealed pipe part, η k ,η s ,η z ,η h ,η f They are the local resistance coefficients of the fluid sudden expansion pressure loss, fluid sudden contraction pressure loss, right-angle turn pressure loss, converging tee pressure loss, and diverting tee pressure loss inside the floor cavity excluding the concealed pipe part, d 腔 is the constant flow equivalent diameter of the cavity, λ 腔 is the longitudinal resistance coefficient in the cavity;

[0182] From the above, we can get the equivalent length l of the total local pressure loss in the floor cavity excluding the concealed pipe part η for:

[0183]

[0184] The equivalent length l of the pressure loss along the floor cavity excluding the concealed pipe part λ Equivalent to the cavity length l 腔 , so the equivalent length l of the total pressure loss in the floor cavity excluding the concealed pipe part 腔 (equivalent) to:

[0185] l 腔 (equivalent) = l η +l 腔

[0186] In addition, since there is no local pressure loss in the blind pipe and only pressure loss along the way, the equivalent length of the total pressure loss of the system composed of the blind pipe and the cavity is:

[0187] l 总 (equivalent) = l η +l 腔 +l 管 .

Claims

1. A method for calculating pressure loss of a diverter tee based on vortex energy, characterized by: For a rectangular floor structure with a hollow interior, ventilation holes are respectively opened on the three adjacent sides of the floor, thereby forming a diverter tee hollow floor cavity in the hollow floor, wherein one of the three ventilation holes is an air inlet and the other two are air outlets. When both air outlets are at right angles to the air inlet, it is a right-angle diverter tee cavity. When one air outlet is at right angles to the air inlet and the other air outlet is at a 180° right angle to the air inlet, it is a right-angle diverter tee cavity. By calculating the total pressure loss caused by vortices in the cavity and correcting it with the coefficient, the pressure losses at each inlet and outlet of the right-angle diverter tee cavity and the right-angle diverter tee cavity can be obtained respectively. The specific steps are as follows: As the airflow enters from an air inlet of the hollow floor slab with a diverter tee and is subsequently discharged from two air outlets, four vortex areas are formed near the four corners in the cavity of the hollow floor slab. The cylindrical vortices in the four vortex areas fill the entire vortex area. The four vortices are cylindrical vortex A, cylindrical vortex A', cylindrical vortex B, and cylindrical vortex B'. Cylindrical vortex A and cylindrical vortex A' are respectively arranged on both sides of the air inlet, while cylindrical vortex B and cylindrical vortex B' are located on the other two sides of the hollow floor slab, symmetrical to cylindrical vortex A and cylindrical vortex A'. Assuming that the pressure loss in the cavity is caused by cylindrical vortices, the pressure loss in a single cylindrical vortex is first derived, and then the pressure loss in four cylindrical vortices is derived. The cylindrical vortex only rotates in the plane direction and does not rotate in the axial direction. The energy loss calculation method in the infinitesimal arc inside the cylindrical vortex of the fluid is determined using Newton's law of internal friction in fluid mechanics. A method for calculating the total pressure loss of a fluid cylindrical vortex based on calculus. The viscous energy loss in the cylindrical vortex A and cylindrical vortex A' regions is calculated based on the inlet velocity of the hollow slab cavity, the outlet velocity of the air outlet, and the cavity size. The viscous energy loss in the cylindrical vortex B and cylindrical vortex B' regions is calculated based on the initial boundary value conditions; Introduce the correction factor and calculate the total pressure loss in the cavity and the pressure loss at each outlet; The straight-angle-to-right-angle pressure conversion coefficient is introduced into the straight-angle converging tee to calculate the total pressure loss in the cavity of the right-angle diverging tee and the pressure loss at each outlet.

2. The method for calculating pressure loss of a diverter tee based on eddy energy according to claim 1, characterized in that: The calculation method for determining the energy loss in the micro-arc within the fluid vortex based on Newton's law of internal friction in fluid mechanics includes: Assume that the cylindrical vortex generated in the four vortex regions rotates only in the plane direction and does not rotate in the direction perpendicular to the plane. The thickness is H and the opening angle is dθ. In this micro-arc, the viscous energy loss is generated between the flow layers due to the relative motion of the flow layers, that is, the energy loss of the i-th micro-arc W 涡i , combined with Newton's law of internal friction, we know that W 涡i for: W 涡i =F 摩擦i ·r·dθ F 摩擦i =S i ·t i S i =dr·H Among them, W 涡i represents the energy loss of the i-th micro-arc, F 摩擦i is the viscous force between the micro-arc fluid layers, r is the distance between the micro-arc and the vortex center, dθ is the micro-arc angle, S i is the area of ​​the infinitesimal arc subjected to viscous force, τ i is the viscous shear stress between flow layers, H is the thickness of the cylindrical vortex; The Newton internal friction formula in the circular coordinate system is: v r =ω·r Where: μ is the dynamic viscosity of the fluid, v r is the fluid velocity along the annular tangent direction, ω is the vortex angular velocity; So we can get the energy loss of the infinitesimal arc W 涡i for: W 涡i =Hμω·dr·r·dθ。 3. The method for calculating pressure loss of a diverter tee based on eddy energy according to claim 2, characterized in that: The calculation method for determining the total pressure loss of a fluid vortex based on calculus is: In the cavity cross-sectional flow field diagram, there is an obvious large vortex in each area. Due to the consistency of the cavity in height, the vortex formed is set as a cylindrical vortex. Only four large cylindrical vortices need to be calculated in the four areas: cylindrical vortex A, cylindrical vortex A', cylindrical vortex B, and cylindrical vortex B', and then correction coefficients are used for correction. The pressure loss of the entire cylindrical vortex is regarded as the combination of the pressure losses of several micro-arcs. The total energy loss W can be obtained by integrating the energy loss of the micro-arcs through calculus method. 涡 for: Pressure loss ΔP caused by vortex 涡 and energy loss W 涡 The relationship between them is as follows: In the above formula, R is the average radius of the vortex, ρ is the fluid density, and g is the acceleration due to gravity; By changing different cylindrical vortex radius parameters and angular velocities, the pressure losses of cylindrical vortex A, cylindrical vortex A', cylindrical vortex B, and cylindrical vortex B' can be calculated. Among them, cylindrical vortex A and cylindrical vortex A' are symmetrical, with consistent angular velocity and radius. The same is true for cylindrical vortex B and cylindrical vortex B'.

4. The method for calculating pressure loss of a diverter tee based on eddy energy according to claim 3, characterized in that: Determine the basic arrangement pattern of the diverter tee cavity and divide the four vortex areas to be analyzed, including cylindrical vortex A, cylindrical vortex A', cylindrical vortex B, and cylindrical vortex B' in the cavity: The energy loss caused by vortex is studied by taking the symmetrical right-angle diverter tee as the object. x1, x2, y1, y2 are respectively the distance from the left side of the air inlet to the left side of the cavity, the distance from the right side of the air inlet to the right side of the cavity, the distance from the lower side of the air outlet to the lower side of the cavity, and the distance from the upper side of the air inlet to the upper side of the cavity. Due to the symmetry of the cavity of the right-angle diverter tee, the relationship between the parameters is as follows: x1=x2 y1=y2 Define the cylindrical vortex A, cylindrical vortex A', cylindrical vortex B, and cylindrical vortex B' generated in the internal vortex distribution of the flat-angle splitter tee cavity. The vortex radius R of cylindrical vortex A is A Expressed as Cylindrical vortex B vortex radius R B for Due to the symmetry of the diverter tee, the radii of cylindrical vortex A' and cylindrical vortex B' are:

5. The method for calculating pressure loss of a diverter tee based on eddy energy according to claim 4, characterized in that: The viscous energy loss of cylindrical vortex A and cylindrical vortex A' determined based on initial and boundary conditions includes: The total viscous energy loss W of the cylindrical vortex A 涡A for: Here, the angular velocity ω of the cylindrical vortex A is A for: Where v0 is the inlet fluid velocity of the cavity, k A is the velocity conversion coefficient of cylindrical vortex A, which is measured through previous experiments; Due to the symmetry of the cavity, the total viscous energy loss W of the cylindrical vortex A' can be obtained by the same logic. 涡A' for: Where, ω A' is the angular velocity of the cylindrical vortex A'.

6. The method for calculating pressure loss of a diverter tee based on eddy energy according to claim 1, characterized in that: Based on the initial boundary value conditions, the viscous energy loss in the cylindrical vortex B and cylindrical vortex B' regions is determined as: The total viscous energy loss W of the cylindrical vortex B 涡B for: Here, the angular velocity ω of the cylindrical vortex B is B for: Among them, k B is the velocity conversion coefficient of cylindrical vortex B, which is measured by experiment; Due to the symmetry of the cavity, the total viscous energy loss W of the cylindrical vortex B' is similarly 涡B' for: Where, ω B' is the angular velocity of the cylindrical vortex B'.

7. The method for calculating pressure loss of a diverter tee based on vortex energy according to claim 1, characterized in that: In the hollow slab with a straight-angle diverter tee, the correction coefficient is used to calculate the total pressure loss in the cavity, and the pressure loss at each outlet of the cavity slab is calculated as follows: The airflow enters the internal cavity from the air inlet of the hollow floor slab with a right angle diversion tee. Due to the thickness of the material of the hollow floor slab, a concealed pipe is installed between the air inlet and outlet of the floor slab and the cavity. The concealed pipe is a rectangular structure or a multi-circular pipe structure. Since the size of the concealed pipe is significantly smaller than the size of the internal cavity of the floor slab, a significant sudden expansion phenomenon of the structure will occur. The pressure loss caused by the sudden expansion is W. e It indicates that when the air flows out of the cavity and into the blind pipe at the outlet, due to the difference in size between the outlet blind pipe and the cavity, an obvious sudden shrinkage phenomenon will occur. The total pressure loss caused by the sudden shrinkage at the two outlets of the cavity is W. r express; In the cavity of the hollow floor, there is not only viscous energy loss caused by vortex, sudden expansion and contraction pressure loss, but also energy loss caused by fluid-wall friction. However, in the diverter tee cavity, the pressure loss caused by the latter is much smaller than the energy loss caused by vortex viscosity. Therefore, the total energy loss W in the diverter tee cavity is calculated by 平 The correction coefficient is introduced to make corrections as follows: W 平 =K(W 涡A +W 涡A’ +W 涡B +W 涡B’ +W e +W r ) Among them, K is the energy loss correction coefficient, which needs to be measured through experiments; The total pressure loss ΔP in the cavity of the right-angle diverter tee 平 for: Where ρ is the fluid density and g is the acceleration due to gravity; Since the right-angle confluence tee cavity is bilaterally symmetrical, the energy losses from the inlet to the two outlets are W 平出1 、W 平出2 , pressure loss from inlet to outlet ΔP 平出1 , ΔP 平出2 as follows:

8. The method for calculating pressure loss of a diverter tee based on eddy energy according to claim 7, characterized in that: When calculating the pressure loss of the right-angle split tee cavity, convert the right-angle split tee cavity into a straight-angle split tee cavity with the same working conditions, calculate the pressure loss from the inlet to each outlet, and then introduce the straight-angle-right-angle correction coefficient to calculate the total pressure loss in the right-angle split tee cavity and the pressure loss at each outlet: For the right-angle split tee cavity, the complicated pressure loss calculation process is no longer repeated. Instead, the pressure loss of the right-angle split tee cavity under the same working condition is calculated by borrowing it. Then, the right-angle-to-right-angle coefficient conversion is performed to obtain the desired right-angle split tee cavity pressure loss. That is, the outlet concealed pipe parallel to the inlet concealed pipe is rotated 90 degrees to convert the original right-angle split tee cavity into a right-angle split tee cavity, which is called the right-angle split tee cavity under the same working condition. The pressure losses at the two outlets of the right-angle diverter tee cavity under the same working conditions are related to the pressure losses at the outlets of the right-angle diverter tee cavity as follows: ξ 下 ΔP 平出1 ≤ΔP 直出180° ≤ΔP 直出90° ≤ξ 上 ΔP 平出1 Among them, ξ 下 ,ξ 上 are the upper and lower critical conversion coefficients of straight angle to right angle, ΔP 直出180° is the pressure loss between the 180° outlet blind pipe and the inlet blind pipe, ΔP 直出90° It is the pressure loss between the 90° outlet blind pipe and the inlet blind pipe.

9. The method for calculating pressure loss of a diverter tee based on eddy energy according to claim 8, characterized in that: For a concrete right-angle diversion tee cavity floor slab with an absolute roughness of 0.7 mm, the upper and lower critical correction coefficients for the right angle to right angle are: x 下 =0.93 x 上 =1.08 For diversion cavities made of different materials, the corresponding correction coefficients should be measured according to actual experiments.

10. A method for calculating the equivalent energy loss length of a ventilated cavity floor according to any one of claims 1 to 9, characterized in that: Calculate the equivalent energy loss length of the ventilation cavity floor according to different concealed pipe ventilation cavity structures; The cavity of the cavity floor when realizing the ventilation and air-conditioning channel function includes full straight cavity, right-angle turn cavity, converging tee cavity, right-angle diverting tee cavity, right-angle diverting tee cavity, and cavity at the vent; The pressure loss inside the cavity can be divided into the pressure loss along the way ΔP λ and local pressure loss ΔP η , where the pressure loss along the way is ΔP λ The occurrence of the viscous effect is due to the shear stress caused by the friction between the fluid and the wall, and the local pressure loss ΔP η It is mostly caused by a large curvature change in the shape of the fluid wall. The two methods for calculating pressure loss in fluid mechanics are as follows: Where λ is the resistance coefficient along the path, l is the length along the path between the fluid and the wall, d is the flow velocity equivalent diameter of the fluid section, v is the flow velocity, and η is the local resistance coefficient; The main reasons for various forms of cavity internal pressure loss include: fluid sudden expansion pressure loss ΔP ηk , Fluid sudden contraction pressure loss ΔP ηs , pressure loss along the way ΔP λ , right-angle turn pressure loss ΔP ηz , pressure loss of converging tee ΔP ηh , diversion tee pressure loss ΔP ηf Combining the above six pressure loss calculation methods, the total pressure loss of any cavity in different designs can be obtained as follows: Where n ηk is the number of sudden expansion pressure losses in the system, n ηs is the number of sudden pressure losses in the system, n ηz is the number of right-angle turns in the system, n ηh is the number of pressure losses in the converging tee in the system, n ηf is the number of pressure losses in the diversion tee in the system, n λ is the number of pressure losses along the system; All local pressure losses are converted into pressure losses along the way, and the calculation method of the equivalent energy loss length of the ventilated cavity floor is proposed as follows: Where, l ηk (equivalent), l ηs (equivalent), l ηz (equivalent), l ηh (equivalent), l ηf (Equivalent) are the equivalent lengths of the fluid sudden expansion pressure loss, fluid sudden contraction pressure loss, right-angle turn pressure loss, converging tee pressure loss, and diverting tee pressure loss inside the floor cavity excluding the concealed pipe part, η k ,η s ,η z ,η h ,η f They are the local resistance coefficients of the fluid sudden expansion pressure loss, fluid sudden contraction pressure loss, right-angle turn pressure loss, converging tee pressure loss, and diverting tee pressure loss inside the floor cavity excluding the concealed pipe part, d 腔 is the constant flow equivalent diameter of the cavity, λ 腔 is the longitudinal resistance coefficient in the cavity; From the above, we can get the equivalent length l of the total local pressure loss in the floor cavity excluding the concealed pipe part η for: The equivalent length l of the pressure loss along the floor cavity excluding the concealed pipe part λ Equivalent to the cavity length l 腔 , so the equivalent length l of the total pressure loss in the floor cavity excluding the concealed pipe part 腔 (equivalent) to: l 腔 (equivalent) = l η +l 腔 In addition, since there is no local pressure loss in the blind pipe and only pressure loss along the way, the equivalent length of the total pressure loss of the system composed of the blind pipe and the cavity is: l 总 (equivalent) = l η +l 腔 +l 管 .

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