Method for predicting dynamic distribution of indoor air flow field and temperature field of building

Abstract

The invention discloses a method for predicting dynamic distribution of an indoor air flow field and a temperature field of a building. The method comprises the steps of performing grid division on a target space to obtain three-dimensional grid units, setting boundary attributes of the target space and initial values of air field parameters, and then obtaining vector velocities of the three-dimensional grid units according to an air transfer velocity between two three-dimensional grid units, then, according to the pressure intensity, the temperature and the air transfer speed of the three-dimensional grid units at the current moment, the pressure intensity, the temperature and the air transfer speed of the three-dimensional grid units at the next moment are obtained, and finally, the air flowing moment of the target space is continuously updated and iterated. And the distribution result of the air flow field and the temperature field in the target space in the air flowing process is obtained. The method is beneficial to improving the directivity of heating and ventilation design or air conditioning system adjustment, so that the efficiency of indoor environment quality optimization is improved, and effective assistance is provided for improving the comfort of a user and reducing energy consumption.

Description

Technical Field

[0001] The invention belongs to the field of flow field and temperature field measurement, and in particular relates to a method for predicting the dynamic distribution of indoor air flow field and temperature field in a building. Background Art

[0002] In building interiors, air infiltration through doors and windows has a significant impact on the indoor thermal environment. This is especially true in cold winter climates, where the temperature difference between indoors and outdoors is large. Air infiltration becomes the primary pathway for heat loss, leading to extremely uneven indoor temperature distribution, significantly impacting user comfort and potentially leading to energy waste. Therefore, effectively understanding the dynamic distribution of the building's internal temperature field in the presence of air infiltration through doors and windows is an important means of improving the indoor environment and increasing energy efficiency.

[0003] However, in the HVAC design process of traditional building projects, it is usually assumed that the indoor air has a stable and uniform temperature field to estimate the air conditioning load, and the local uneven dynamic air temperature distribution caused by air infiltration is ignored, resulting in widespread uncomfortable environmental feedback for users in the actual built environment. To improve this problem, many HVAC designers have begun to use computational fluid dynamics (CFD) simulation to assist in design, but this first places higher demands on the technical level of relevant practitioners, and a single simulation calculation will consume a lot of time and computing power. It is difficult to meet the short-cycle and high-frequency design modification requirements by optimizing the design through repeated simulation trial and error. Therefore, in order to more accurately and conveniently describe the temperature distribution in the interior space of a building under air infiltration, a more dynamic and adaptive temperature flow field calculation method is urgently needed. Summary of the Invention

[0004] In order to solve the problems existing in the background technology, the purpose of the present invention is to provide a prediction method for the dynamic distribution of the indoor air flow field and temperature field of a building, so as to solve the problems of long simulation calculation cycle and high computing power requirement of the air flow field and temperature field in the existing technology.

[0005] The technical solution adopted by the present invention comprises the following steps:

[0006] Step S1: first, mesh the target space to obtain a number of three-dimensional mesh units;

[0007] Step S2: Next, the boundary attributes of the target space and the initial values ​​of the air field parameters are set; the air field parameters include the temperature and pressure of each three-dimensional grid cell, and the air transfer speed between two three-dimensional grid cells;

[0008] Step S3: then obtaining the vector velocity of each three-dimensional grid unit at the current moment according to the air transfer velocity between the two three-dimensional grid units at the current moment;

[0009] Step S4: obtaining the pressure, temperature, and air transfer speed of the three-dimensional grid unit at the next moment based on the pressure, temperature, and air transfer speed of the three-dimensional grid unit at the current moment;

[0010] Step S5 and step S3 to step S4 constitute a complete air flow field temperature field prediction process at a moment, continuously updating the air flow moment n of the target space, and repeating steps S3 to step S4 multiple times to obtain the air flow field temperature field at different moments, and then obtain the distribution results of the air flow field temperature field in the target space during the air flow process.

[0011] In step S1, the target space is divided into grids, and the specific steps are as follows:

[0012] Step S1.1, define the target space coordinate system: In the target space coordinate system, define the direction parallel to the width of the target space as the X-axis, the direction parallel to the length of the target space as the Y-axis, and the direction parallel to the height of the target space as the Z-axis. The Z-axis of the target space is perpendicular to the XY plane.

[0013] Step S1.2: Then, the target space is grid-divided at intervals of a preset grid division size, and each of the divided three-dimensional space grids is used as a three-dimensional grid unit.

[0014] The step S2 is specifically as follows:

[0015] Step S2.1, define the boundary properties of the target space: define the openings that generate air infiltration in the target space as air infiltration openings with constant flow rate and constant temperature, and define the cooling and heating sources as cooling and heating sources with constant flow rate, constant flow rate, and constant temperature;

[0016] Step S2.2: define the initial value of the temperature of the three-dimensional grid unit, define the initial value of the pressure of the three-dimensional grid unit, and define the initial value of the air transfer speed between two three-dimensional grid units.

[0017] In step S3, the three-dimensional grid cell vector velocity is obtained as follows:

[0018] In the R-axis direction, if the air in the three-dimensional grid unit j1 and the three-dimensional grid unit j2 flows into the three-dimensional grid unit i at the same time, then v R,i (n) = w R,i,j1 (n)-w R,i,j2 (n);

[0019] In the R-axis direction, if the air in the three-dimensional grid unit i flows out to the three-dimensional grid unit j1 and the three-dimensional grid unit j2 at the same time, then v R,i (n) = 0;

[0020] In the R-axis direction, if the air in the three-dimensional grid unit j1 flows into the three-dimensional grid unit i, and the air in the three-dimensional grid unit i flows into the three-dimensional grid unit j2, then v R,i (n) = w R,i,j2 (n);

[0021] In the R-axis direction, if the air in the three-dimensional grid unit j2 flows into the three-dimensional grid unit i, and the air in the three-dimensional grid unit i flows into the three-dimensional grid unit j1, then v R,i (n) = w R,i,j1 (n);

[0022] Among them, v R,i (n) represents the component of the vector velocity of the three-dimensional grid cell i in the R-axis direction at time n, R∈{X,Y,Z}; w R,i,j (n) represents the component of the air transfer velocity between the three-dimensional grid cell i and the three-dimensional grid cell j in the R-axis direction at time n, j∈{j1,j2}; the three-dimensional grid cell j1 represents the three-dimensional grid cell adjacent to the three-dimensional grid cell i along the negative direction of the R-axis; the three-dimensional grid cell j2 represents the three-dimensional grid cell adjacent to the three-dimensional grid cell i along the positive direction of the R-axis.

[0023] The step S4 is specifically as follows: according to the pressure, temperature and air transfer speed of the three-dimensional grid unit at the current moment, the pressure, temperature and air transfer speed of the three-dimensional grid unit at the next moment are obtained according to the following formula;

[0024] V i ·(ρ i (n+1)-ρ i (n)) / τ=Σ j m i,j (n)+Σ sou m i,sou

[0025] A i,j ·l R,i,j ·ρ i,j (n)·(w R,i,j (n+1)-w R,i,j (n)) / τ=F R,P,i,j (n)+F R,M,i,j (n)+F R,V,i,j (n)+F R,G,i,j (n)

[0026] ρ i (n) = P i (n) / (R0 / T i (n)),R∈{X,Y,Z}

[0027] Among them, V irepresents the volume of the i-th three-dimensional grid cell i; ρ i (n) represents the density of the three-dimensional grid cell i at time n; τ represents the time step of the constraint; m i,j (n) represents the mass flow between 3D grid unit i and 3D grid unit j at time n; m i,sou represents the mass flow between the cooling and heating source and the three-dimensional grid unit i, sou represents the cooling and heating source in the target space; A i,j represents the contact area between 3D mesh unit i and 3D mesh unit j; l R,i,j represents the component of the geometric center distance between three-dimensional grid cell i and three-dimensional grid cell j in the R-axis direction; ρ i,j (n) represents the average density of 3D grid cell i and 3D grid cell j at time n; w R,i,j (n) represents the component of the air transfer velocity between the three-dimensional grid unit i and the three-dimensional grid unit j in the R-axis direction at time n; F R,P,i,j (n) represents the component of the air pressure in the R-axis direction between the three-dimensional grid unit i and the three-dimensional grid unit j at time n; F R,M,i,j (n) represents the component of the momentum force between the three-dimensional grid unit i and the three-dimensional grid unit j in the R-axis direction at time n; F R,V,i,j (n) represents the component of the viscous force between the three-dimensional grid unit i and the three-dimensional grid unit j in the R-axis direction at time n; F R,G,i,j (n) represents the component of the gravity between the three-dimensional grid unit i and the three-dimensional grid unit j in the R-axis direction at time n; P i (n) represents the air pressure of the three-dimensional grid cell i at time n; R0 represents the gas constant of air; T i (n) represents the air temperature of three-dimensional grid cell i at time n.

[0028] In step S4, the temperature T of the three-dimensional grid unit at each moment i (n) The expression is as follows:

[0029] V i ·ρ i (n)·c p ·(T i (n+1)-T i (n)) / τ=

[0030] Σ j m i,j (n)·c p ·(T j (n)-T i (n))+C B ·A i,j ·(T j (n)-Ti (n))+Σ sou Q i,sou

[0031] Among them, c p represents the specific heat capacity of air; T i (n) represents the air temperature of the three-dimensional grid cell i at time n; j represents the three-dimensional grid cell j adjacent to the three-dimensional grid cell i; C B represents the temperature difference heat transfer coefficient; Q i,sou It represents the cold / heat flow intensity provided by the cooling and heating source sou to the three-dimensional grid unit i.

[0032] In step S4, the air pressure, momentum force, viscous force, and gravity between the three-dimensional grid unit i and the three-dimensional grid unit j are obtained by processing according to the following formulas:

[0033] F R,P,i,j (n) = A i,j ·(P i (n+1)-P j (n+1))

[0034] F R,M,i,j (n) = A i,j ·ρ i,j (n)·(v R,i (n)-v R,j (n))

[0035] F R,V,i,j (n)=(F R,V,i (n)+F R,V,j (n)) / 2

[0036] F R,G,i,j (n)=-ρ i,j (n)·g·A i,j ·l R,i,j ,R∈{X,Y,Z}

[0037] Among them, v R,i (n) represents the component of the vector velocity of the three-dimensional grid cell i in the R-axis direction at time n; v R,j (n) represents the component of the vector velocity of the three-dimensional grid unit j in the R-axis direction at time n; F R,V,i (n) represents the component of the viscous force of the three-dimensional grid element i in the R-axis direction at time n; F R,V,j (n) represents the component of the viscous force of the three-dimensional grid element j in the R-axis direction at time n; P i (n+1) represents the air pressure of the three-dimensional grid cell i at time n+1; g represents the acceleration due to gravity;

[0038] In step S4, the components of the viscous force of the three-dimensional grid unit i in the X, Y, and Z axis directions are obtained according to the vector velocity using the following formula:

[0039] F Z,V,i (n)=μ·(((△v Z,i,k1 / l X,i,k1 )-(△v Z,i,k2 / l X,i,k2 ))·A i,k1 +((△v Z,i,k3 / l Y,i,k3 )-(△v Z,i,k4 / l Y,i,k4 ))·A i,k3 )

[0040] F X,V,i (n)=μ·(((△v X,i,k3 / l Y,i,k3 )-(△v X,i,k4 / l Y,i,k4 ))·A i,k3 +((△v X,i,k5 / l Z,i,k5 )-(△v X,i,k6 / l Z,i,k6 ))·A i,k5 )

[0041] F Y,V,i (n)=μ·(((△v Y,i,k5 / l Z,i,k5 )-(△v Y,i,k6 / l Z,i,k6 ))·A i,k5 +((△v Y,i,k1 / l X,i,k1 )-(△v Y,i,k2 / l X,i,k2 ))·A i,k1 )

[0042] Where μ represents the apparent viscosity coefficient of turbulence and boundary layer; △v R,i,j Represents the vector velocity time difference, △v R,i,j =v R,i,j (n+1)-v R,i,j (n), v R,i,j(n) represents the component of the vector velocity difference between the three-dimensional grid cell i and the three-dimensional grid cell j in the R-axis direction at time n, j∈{k1, k2, k3, k4, k5, k6}, where subscript k1 represents the three-dimensional grid cell k1 adjacent to the three-dimensional grid cell i along the negative direction of the X-axis, subscript k2 represents the three-dimensional grid cell k2 adjacent to the three-dimensional grid cell i along the positive direction of the X-axis, subscript k3 represents the three-dimensional grid cell k3 adjacent to the three-dimensional grid cell i along the negative direction of the Y-axis, subscript k4 represents the three-dimensional grid cell k4 adjacent to the three-dimensional grid cell i along the positive direction of the Y-axis, subscript k5 represents the three-dimensional grid cell k5 adjacent to the three-dimensional grid cell i along the negative direction of the Z-axis, and subscript k6 represents the three-dimensional grid cell k6 adjacent to the three-dimensional grid cell i along the positive direction of the Z-axis; F Z,V,i (n), F X,V,i (n), F Y,V,i (n) represents the components of the viscous force of the three-dimensional grid element i in the X, Y, and Z axis directions at time n, respectively.

[0043] Under known basic building conditions, the method of the present invention can quickly generate the spatiotemporal dynamic distribution of indoor air temperature by inputting the flow rate and temperature of the air penetrating through doors, windows or other openings to meet actual design and operation optimization requirements.

[0044] The beneficial effects of the present invention are:

[0045] 1. The present invention is dynamic, convenient and adaptable. Unlike the steady-state algorithm that simply relies on the heat conservation formula, the method of the present invention can dynamically calculate the changing process of the air temperature field, which is closer to the uneven and unstable air temperature distribution characteristics of the actual environment.

[0046] 2. Compared with the computational fluid dynamics (CFD) simulation method, the method of the present invention is simple to operate, has lower requirements on the division accuracy of the number of calculation grids, does not require high computing power, and has a faster calculation speed, which is more suitable for the actual needs of rapid response.

[0047] 3. The method of the present invention comprehensively considers the effects of air gravity, viscosity, momentum and pressure on the airflow pattern during the calculation process. It is applicable to a variety of actual air infiltration scenarios from low to high flow rates, improving accuracy while ensuring the applicability of the method.

[0048] 4. The method of the present invention helps designers and operation managers to more accurately grasp the dynamic distribution of the indoor air temperature flow field of the building, which is conducive to improving the directionality of HVAC design or air-conditioning system adjustment, thereby improving the efficiency of indoor environmental quality optimization and providing effective assistance for improving user comfort and reducing energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 is a flow chart of the present invention;

[0050] Figure 2 Schematic diagram of the target space grid division and boundary condition setting using this method;

[0051] Figure 3 This is a schematic diagram of meshing and boundary condition setting of target space using existing computational fluid dynamics (CFD) method;

[0052] Figure 4 Schematic diagram of the conversion relationship between air transfer velocity and vector velocity;

[0053] Figure 5 The figure is a comparison chart of the calculation results of the target space flow field using the method of the present invention and the CFD method. DETAILED DESCRIPTION

[0054] The present invention is described in detail below with reference to specific implementation cases. The following implementation cases will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form.

[0055] The embodiment is a lobby space of a certain building. The target space is a rectangular space with a length of 24.0m, a width of 12.0m and a height of 6.0m. There is a 2 The velocity inlet represents the opening where air infiltration occurs. The other side is connected to the rest of the building space and is set as the outflow interface with an area of ​​72.0m 2 , the rest of the wall surfaces are set as adiabatic smooth interfaces. For the method of the present invention, a total of 30 computational grids (length 4.0m, width 4.0m, height 3.0m) are set. At the same time, the fluid simulation software Fluent is used to establish the same model for fluid mechanics CFD simulation for verification, and a total of 200,000 computational grids are divided, such as Figure 2 The calculation scenario is winter, with the outdoor temperature set to 0°C, the indoor temperature to 18°C, the air infiltration rate to 0.5m / s, and the time step used in the calculation set to 1s.

[0056] like Figure 1 As shown, the embodiment of the method of the present invention is as follows, comprising the following steps:

[0057] Step S1: First, the target space is divided into a grid to obtain a number of three-dimensional grid units;

[0058] Step S2: Next, the boundary attributes of the target space and the initial values ​​of the air field parameters are set; the air field parameters include the temperature and pressure of each three-dimensional grid cell, and the air transfer speed between two three-dimensional grid cells;

[0059] Step S3: then obtaining the vector velocity of each three-dimensional grid unit at the current moment according to the air transfer velocity between the two three-dimensional grid units at the current moment;

[0060] Step S4: obtaining the pressure, temperature, and air transfer speed of the three-dimensional grid unit at the next moment based on the pressure, temperature, and air transfer speed of the three-dimensional grid unit at the current moment;

[0061] Step S5 and step S3 to step S4 constitute a complete air flow field temperature field prediction process at a moment, continuously updating the air flow moment n of the target space, and repeating steps S3 to step S4 multiple times to obtain the air flow field temperature field at different moments, and then obtain the dynamic distribution results of the air flow field temperature field in the target space during the air flow process.

[0062] When the velocity residual, pressure residual, and temperature residual of the three-dimensional grid unit are small enough (≤10 -5 ), the iteration can be stopped and it is considered that the quasi-steady state is reached at this moment. The velocity residual is the difference between the vector velocity of the three-dimensional grid unit at time n+1 and the vector velocity at time n; the pressure residual is the difference between the pressure of the three-dimensional grid unit at time n+1 and the pressure at time n; the temperature residual is the difference between the temperature of the three-dimensional grid unit at time n+1 and the temperature at time n.

[0063] In the specific implementation step S1, the target space is gridded. The specific steps are as follows:

[0064] Step S1.1, define the target space coordinate system: In the target space coordinate system, define the direction parallel to the width of the target space as the X-axis, the direction parallel to the length of the target space as the Y-axis, and the direction parallel to the height of the target space as the Z-axis. The Z-axis of the target space is perpendicular to the XY plane.

[0065] Step S1.2: Then, the target space is grid-divided at intervals of a preset grid division size, and each of the divided three-dimensional space grids is used as a three-dimensional grid unit.

[0066] Taking the target space of the rectangle as an example, the grid size along the X-axis is recorded as l x0 , the grid size along the Y axis is recorded as l y0 , the grid size along the Z axis is recorded as l z0 , then the volume of each three-dimensional grid cell is V g , V g0 =l x0 ·l y0 ·l z0 The grid size can be reduced proportionally according to the calculation requirements, and the target space is divided into a calculation area consisting of N three-dimensional grid units, with a space volume VB =N·V g ;

[0067] Step S2 is specifically as follows:

[0068] Step S2.1, define the boundary attributes of the target space: the openings that generate air infiltration in the target space are regarded as air infiltration openings with constant flow rate and constant temperature, and the cooling and heating sources are regarded as cold and hot sources with constant flow rate, constant flow rate and constant temperature. The air infiltration openings are specifically the locations of doors and windows. The sth air infiltration opening A s The velocity of the flow is denoted as v in,s , cooling and heating sources include air conditioning, floor heating, etc. If the target space has an outflow interface, the initial outflow velocity is given, where the outflow interface refers to the space connected to the outside, such as the lobby; at the same time, the wall grid of the target space is regarded as a three-dimensional grid unit with zero volume, where the wall grid is specifically the two-dimensional grid unit at the location of the outer wall of the target space;

[0069] Since the air infiltration opening and the outflow interface are both located at the outer wall of the target space, the grid cells at the positions of the air infiltration opening and the outflow interface can be regarded as three-dimensional grid cells with zero volume; when a three-dimensional grid cell i is in contact with the outer wall / air infiltration opening / outflow interface, the two-dimensional grid cell at the position of the outer wall / air infiltration opening / outflow interface can be regarded as a three-dimensional grid cell j with zero volume, where j represents the three-dimensional grid cell adjacent to the three-dimensional grid cell i, and the flow velocity of the air infiltration opening / outflow interface is taken as the air transfer velocity between the three-dimensional grid cell i and the three-dimensional grid cell j.

[0070] Step S2.2: define the initial value of the temperature of the three-dimensional grid unit, define the initial value of the pressure of the three-dimensional grid unit, and define the initial value of the air transfer speed between two three-dimensional grid units.

[0071] The air in each three-dimensional grid cell i is considered to have a uniform temperature, and the air temperature in the i-th three-dimensional grid cell i is denoted as T i (n), the density of the three-dimensional grid cells ρ i (n) According to the ideal gas equation, the temperature T of the three-dimensional grid cell i (n) and the pressure P of the three-dimensional grid cell i (n) is converted to the velocity of the three-dimensional grid unit in the XYZ axis direction, which is represented by the vector velocity. The velocity of the three-dimensional grid unit i along the X axis is recorded as v X,i (n), the velocity along the Y axis is denoted as v Y,i (n), the velocity along the Z axis is denoted as v Z,i (n), the assignment method of the three-dimensional grid unit i on each axis is as follows Figure 4 As shown, Figure 4 (a) shows the situation where the air on both sides of the three-dimensional grid unit enters and exits in the same direction. Figure 4 (b) shows the situation where air enters both sides of the three-dimensional grid unit at the same time. Figure 4 (c) shows the situation where air flows out simultaneously on both sides of the three-dimensional grid unit.

[0072] In step S3, the three-dimensional grid cell vector velocity is obtained as follows;

[0073] In the R-axis direction, if the air in the three-dimensional grid unit j1 and the three-dimensional grid unit j2 flows into the three-dimensional grid unit i at the same time, then v R,i (n) = w R,i,j1 (n)-w R,i,j2 (n);

[0074] In the R-axis direction, if the air in the three-dimensional grid unit i flows out to the three-dimensional grid unit j1 and the three-dimensional grid unit j2 at the same time, then v R,i (n) = 0;

[0075] In the R-axis direction, if the air in the three-dimensional grid unit j1 flows into the three-dimensional grid unit i, and the air in the three-dimensional grid unit i flows into the three-dimensional grid unit j2, then v R,i (n) = w R,i,j2 (n);

[0076] In the R-axis direction, if the air in the three-dimensional grid unit j2 flows into the three-dimensional grid unit i, and the air in the three-dimensional grid unit i flows into the three-dimensional grid unit j1, then v R,i (n) = w R,i,j1 (n);

[0077] Among them, v R,i (n) represents the component of the vector velocity of the three-dimensional grid cell i in the R-axis direction at time n, R∈{X,Y,Z}; w R,i,j (n) represents the component of the air transfer velocity between the three-dimensional grid cell i and the three-dimensional grid cell j in the R-axis direction at time n, j∈{j1,j2}; the three-dimensional grid cell j1 represents the three-dimensional grid cell adjacent to the three-dimensional grid cell i along the negative direction of the R-axis; the three-dimensional grid cell j2 represents the three-dimensional grid cell adjacent to the three-dimensional grid cell i along the positive direction of the R-axis.

[0078] In a specific implementation, if the target space has an outflow interface at the outer wall, the initial value of the outflow velocity of the outflow interface is defined in step S2. The outflow interface is the boundary surface that is conductive with the external space, and the two-dimensional grid cell at the location of the outflow interface is used as a three-dimensional grid cell j' with a zero volume. The three-dimensional grid cell i' represents the three-dimensional grid cell adjacent to the three-dimensional grid cell j'. When the three-dimensional grid cell j' is the outflow interface, the air transfer velocity between the three-dimensional grid cell i' and the three-dimensional grid cell j' obtained in step S4 is corrected. The correction is as follows:

[0079] Step 1: First, the correction coefficient is obtained by processing the air transmission speed obtained in step S4 according to the following formula:

[0080] kc(n)=ΣMin / ΣMout(n)

[0081] ΣMout(n)=Σ(w R,i’,j’ (n)×A j’ )

[0082] Where kc(n) represents the correction coefficient of the outflow velocity at time n; ΣMin represents the sum of the air mass flow rate from all air infiltration openings into the target space; ΣMout(n) represents the sum of the air mass flow rate at the outflow interface at time n; w R,i’,j’ (n) represents the component of the air transfer velocity in the R-axis direction between the three-dimensional grid unit i' and the three-dimensional grid unit j' at time n obtained in step S4, and j' actually represents the three-dimensional grid unit where the flow interface is located; A j’ Represents the area of ​​the three-dimensional grid cell where the flow interface is located;

[0083] Step 2: Then, the air transfer velocity between the three-dimensional grid unit i' and the three-dimensional grid unit j' is corrected according to the correction coefficient kc(n) according to the following formula:

[0084] w c R,i’,j’ (n) = kc(n) × w R,i’,j’ (n)

[0085] Among them, w c R,i’,j’ (n) represents the component of the air transfer velocity in the R-axis direction between the three-dimensional grid unit i' and the three-dimensional grid unit j' at time n after correction;

[0086] Step 3: Finally, substitute the corrected air transfer velocity into step S3 to obtain the vector velocity of the three-dimensional grid unit i'.

[0087] Step S4 specifically comprises: obtaining the pressure, temperature, and air transfer speed of the three-dimensional grid unit at the next moment according to the following formula based on the pressure, temperature, and air transfer speed of the three-dimensional grid unit at the current moment;

[0088] V i ·(ρ i (n+1)-ρ i (n)) / τ=Σ j m i,j (n)+Σ sou m i,sou

[0089] A i,j ·l R,i,j ·ρ i,j (n)·(w R,i,j (n+1)-w R,i,j (n)) / τ=F R,P,i,j (n)+F R,M,i,j (n)+F R,V,i,j (n)+F R,G,i,j (n)

[0090] ρ i (n) = P i (n) / (R0 / T i (n)),R∈{X,Y,Z}

[0091] Among them, V i represents the volume of the i-th three-dimensional grid cell i; ρ i (n) represents the density of the three-dimensional grid cell i at time n; τ represents the time step of the constraint, that is, the difference between time n+1 and time n; m i,j (n) represents the mass flow between the three-dimensional grid unit i and the three-dimensional grid unit j at time n, where j represents the three-dimensional grid unit adjacent to the three-dimensional grid unit i; m i,sou represents the mass flow between the cooling and heating source and the three-dimensional grid unit i, sou represents the cooling and heating source in the target space; A i,j represents the contact area between 3D mesh unit i and 3D mesh unit j; l R,i,j represents the component of the geometric center distance between three-dimensional grid cell i and three-dimensional grid cell j in the R-axis direction; ρ i,j (n) represents the average density of 3D grid cell i and 3D grid cell j at time n; w R,i,j (n) represents the component of the air transfer velocity between the three-dimensional grid unit i and the three-dimensional grid unit j in the R-axis direction at time n; F R,P,i,j (n) represents the component of the air pressure in the R-axis direction between the three-dimensional grid unit i and the three-dimensional grid unit j at time n; F R,M,i,j(n) represents the component of the momentum force between the three-dimensional grid unit i and the three-dimensional grid unit j in the R-axis direction at time n; F R,V,i,j (n) represents the component of the viscous force between the three-dimensional grid unit i and the three-dimensional grid unit j in the R-axis direction at time n; F R,G,i,j (n) represents the component of the gravity between the three-dimensional grid unit i and the three-dimensional grid unit j in the R-axis direction at time n, where F R,G,i,j (n) exists only in the Z-axis direction, and the components of the gravity between two three-dimensional grid cells in the X-axis and Y-axis directions are both 0; P i (n) represents the air pressure of the three-dimensional grid cell i at time n; R0 represents the gas constant of air; T i (n) represents the air temperature of three-dimensional grid cell i at time n.

[0092] In step S4, the temperature T of the three-dimensional grid unit at each moment i (n) The expression is as follows:

[0093] V i ·ρ i (n)·c p ·(T i (n+1)-T i (n)) / τ=

[0094] Σ j m i,j (n)·c p ·(T j (n)-T i (n))+C B ·A i,j ·(T j (n)-T i (n))+Σ sou Q i,sou

[0095] Among them, c p represents the specific heat capacity of air; T i (n) represents the air temperature of the three-dimensional grid cell i at time n; j represents the three-dimensional grid cell j adjacent to the three-dimensional grid cell i; C B represents the temperature difference heat transfer coefficient; Q i,sou It represents the cold / heat flow intensity provided by the cooling and heating source sou to the three-dimensional grid unit i, where the cooling and heating source includes a cooling source and a heat source, and the cooling source and the heat source provide cold flow and heat flow respectively.

[0096] In step S4, the air pressure, momentum force, viscous force, and gravity between the three-dimensional grid cell i and the three-dimensional grid cell j are obtained according to the following formulas:

[0097] F R,P,i,j(n) = A i,j ·(P i (n+1)-P j (n+1))

[0098] F R,M,i,j (n) = A i,j ·ρ i,j (n)·(v R,i (n)-v R,j (n))

[0099] F R,V,i,j (n)=(F R,V,i (n)+F R,V,j (n)) / 2

[0100] F R,G,i,j (n)=-ρ i,j (n)·g·A i,j ·l R,i,j ,R∈{X,Y,Z}

[0101] Among them, v R,i (n) represents the component of the vector velocity of the three-dimensional grid cell i in the R-axis direction at time n; v R,j (n) represents the component of the vector velocity of the three-dimensional grid unit j in the R-axis direction at time n; F R,V,i (n) represents the component of the viscous force of the three-dimensional grid element i in the R-axis direction at time n; F R,V,j (n) represents the component of the viscous force of the three-dimensional grid element j in the R-axis direction at time n; P i (n+1) represents the air pressure of the three-dimensional grid cell i at time n+1; g represents the acceleration due to gravity;

[0102] In step S4, the components of the viscous force of the three-dimensional grid unit i in the X, Y, and Z axis directions are obtained by processing the vector velocity according to the following formula:

[0103] F Z,V,i (n)=μ·(((△v Z,i,k1 / l X,i,k1 )-(△v Z,i,k2 / l X,i,k2 ))·A i,k1 +((△v Z,i,k3 / l Y,i,k3 )-(△v Z,i,k4 / l Y,i,k4 ))·A i,k3 )

[0104] F X,V,i (n)=μ·(((△v X,i,k3 / l Y,i,k3 )-(△v X,i,k4 / l Y,i,k4 ))·A i,k3 +((△v X,i,k5 / l Z,i,k5 )-(△v X,i,k6 / l Z,i,k6 ))·A i,k5 )

[0105] F Y,V,i (n)=μ·(((△v Y,i,k5 / l Z,i,k5 )-(△v Y,i,k6 / l Z,i,k6 ))·A i,k5 +((△v Y,i,k1 / l X,i,k1 )-(△v Y,i,k2 / l X,i,k2 ))·A i,k1 )

[0106] Where μ represents the apparent viscosity coefficient of turbulence and boundary layer; △v R,i,j Represents the vector velocity time difference, △v R,i,j =v R,i,j (n+1)-v R,i,j (n), v R,i,j (n) represents the component of the vector velocity difference between the three-dimensional grid cell i and the three-dimensional grid cell j in the R-axis direction at time n, j∈{k1, k2, k3, k4, k5, k6}, where subscript k1 represents the three-dimensional grid cell k1 adjacent to the three-dimensional grid cell i along the negative direction of the X-axis, subscript k2 represents the three-dimensional grid cell k2 adjacent to the three-dimensional grid cell i along the positive direction of the X-axis, subscript k3 represents the three-dimensional grid cell k3 adjacent to the three-dimensional grid cell i along the negative direction of the Y-axis, subscript k4 represents the three-dimensional grid cell k4 adjacent to the three-dimensional grid cell i along the positive direction of the Y-axis, subscript k5 represents the three-dimensional grid cell k5 adjacent to the three-dimensional grid cell i along the negative direction of the Z-axis, and subscript k6 represents the three-dimensional grid cell k6 adjacent to the three-dimensional grid cell i along the positive direction of the Z-axis; F Z,V,i (n), F X,V,i (n), F Y,V,i (n) represents the components of the viscous force of the three-dimensional grid element i in the X, Y, and Z axis directions at time n, respectively.

[0107] Figure 3 Schematic diagram of meshing and boundary condition setting of target space using existing CFD methods. Figure 5The following figure compares the dynamic calculation results using the method of the present invention and the CFD method. The calculation period was 1000 seconds. Throughout the entire process, the deviation between the flow rate at each interface and the average indoor air temperature was within 4.0%. The calculations were performed on a desktop computer with an Intel i5 processor. The physical calculation time using the method of the present invention was approximately 10 seconds, while the physical calculation time using the CFD simulation method was 30 minutes. This shows that the method of the present invention is simple to operate and significantly shortens the calculation time for the dynamic distribution of the air flow and temperature fields in the target space.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for predicting the dynamic distribution of indoor air flow field and temperature field in a building, characterized in that: The following steps are involved: Step S1, firstly, gridding the target space to obtain a number of three-dimensional grid units; Step S2: Next, the boundary attributes of the target space and the initial values ​​of the air field parameters are set; the air field parameters include the temperature and pressure of each three-dimensional grid unit, and the air transfer speed between two three-dimensional grid units; Step S3, then obtaining the vector velocity of each three-dimensional grid unit at the current moment according to the air transfer velocity between the two three-dimensional grid units at the current moment; Step S4, obtaining the pressure, temperature and air transfer speed of the three-dimensional grid unit at the next moment according to the pressure, temperature and air transfer speed of the three-dimensional grid unit at the current moment; Step S5 and step S3 to step S4 constitute a complete air flow field temperature field prediction process at a moment, continuously updating the air flow moment n of the target space, and repeating steps S3 to step S4 multiple times to obtain the air flow field temperature field at different moments, and then obtain the distribution results of the air flow field temperature field in the target space during the air flow process.

2. The method for predicting the dynamic distribution of indoor air flow field and temperature field of a building according to claim 1, characterized in that: In step S1, the target space is divided into grids, and the specific steps are as follows: Step S1.1, define the target space coordinate system: in the target space coordinate system, define the direction parallel to the width of the target space as the X-axis, the direction parallel to the length of the target space as the Y-axis, and the direction parallel to the height of the target space as the Z-axis, and the Z-axis of the target space is perpendicular to the XY plane; Step S1.2: Then, the target space is grid-divided at intervals of a preset grid division size, and each of the divided three-dimensional space grids is used as a three-dimensional grid unit.

3. The method for predicting the dynamic distribution of indoor air flow field and temperature field of a building according to claim 1, characterized in that: The step S2 is specifically as follows: Step S2.1, define the boundary attributes of the target space: the openings that produce air infiltration in the target space are regarded as air infiltration openings with constant flow rate and constant temperature, and the cooling and heating sources are regarded as cold and hot sources with constant flow rate, constant flow rate and constant temperature; Step S2.2, define the initial value of the temperature of the three-dimensional grid unit, define the initial value of the pressure of the three-dimensional grid unit, and define the initial value of the air transfer speed between two three-dimensional grid units.

4. The method for predicting the dynamic distribution of indoor air flow field and temperature field of a building according to claim 1, characterized in that: In the step S3, the three-dimensional grid unit vector velocity is obtained as follows; In the R-axis direction, if the air in the three-dimensional grid unit j1 and the three-dimensional grid unit j2 flows into the three-dimensional grid unit i at the same time, then v R,i (n) = w R,i,j1 (n)-w R,i,j2 (n); In the R-axis direction, if the air in the three-dimensional grid unit i flows out to the three-dimensional grid unit j1 and the three-dimensional grid unit j2 at the same time, then v R,i (n) = 0; In the R-axis direction, if the air in the three-dimensional grid unit j1 flows into the three-dimensional grid unit i, and the air in the three-dimensional grid unit i flows into the three-dimensional grid unit j2, then v R,i (n) = w R,i,j2 (n); In the R-axis direction, if the air in the three-dimensional grid unit j2 flows into the three-dimensional grid unit i, and the air in the three-dimensional grid unit i flows into the three-dimensional grid unit j1, then v R,i (n) = w R,i,j1 (n); Among them, v R,i (n) represents the component of the vector velocity of the three-dimensional grid cell i in the R-axis direction at time n, R∈{X,Y,Z}; w R,i,j (n) represents the component of the air transfer velocity between the three-dimensional grid cell i and the three-dimensional grid cell j in the R-axis direction at time n, j∈{j1,j2}; the three-dimensional grid cell j1 represents the three-dimensional grid cell adjacent to the three-dimensional grid cell i along the negative direction of the R-axis; the three-dimensional grid cell j2 represents the three-dimensional grid cell adjacent to the three-dimensional grid cell i along the positive direction of the R-axis.

5. The method for predicting the dynamic distribution of indoor air flow field and temperature field of a building according to claim 1, characterized in that: The step S4 is specifically as follows: according to the pressure, temperature and air transfer speed of the three-dimensional grid unit at the current moment, the pressure, temperature and air transfer speed of the three-dimensional grid unit at the next moment are obtained according to the following formula; V i ·(r i (n+1)-p i (n)) / τ=Σ j m i,j (n)+Σ sou m i,sou A i,j ·l R,i,j ·ρ i,j (n)·(w R,i,j (n+1)-w R,i,j (n)) / τ=F R,P,i,j (n)+F R,M,i,j (n)+F R,V,i,j (n)+F R,G,i,j (n) ρ i (n)=P i (n) / (R0 / T i (n)),R∈{X,Y,Z} Among them, V i represents the volume of the i-th three-dimensional grid unit i; ρ i (n) represents the density of the three-dimensional grid cell i at time n; τ represents the time step of the constraint; m i,j (n) represents the mass flow between three-dimensional grid unit i and three-dimensional grid unit j at time n; m i,sou represents the mass flow between the cooling and heating source and the three-dimensional grid unit i, sou represents the cooling and heating source in the target space; A i,j represents the contact area between 3D mesh unit i and 3D mesh unit j; l R,i,j represents the component of the geometric center distance between the three-dimensional grid unit i and the three-dimensional grid unit j in the R-axis direction; ρ i,j (n) represents the average density of 3D grid unit i and 3D grid unit j at time n; w R,i,j (n) represents the component of the air transfer velocity between the three-dimensional grid unit i and the three-dimensional grid unit j in the R-axis direction at time n; F R,P,i,j (n) represents the component of the air pressure between the three-dimensional grid unit i and the three-dimensional grid unit j in the R-axis direction at time n; F R,M,i,j (n) represents the component of the momentum force between the three-dimensional grid unit i and the three-dimensional grid unit j in the R-axis direction at time n; F R,V,i,j (n) represents the component of the viscous force between the three-dimensional grid unit i and the three-dimensional grid unit j in the R-axis direction at time n; F R,G,i,j (n) represents the component of the gravity between the three-dimensional grid unit i and the three-dimensional grid unit j in the R-axis direction at time n; P i (n) represents the air pressure of the three-dimensional grid cell i at time n; R0 represents the gas constant of air; T i (n) represents the air temperature of the three-dimensional grid cell i at time n.

6. The method for predicting the dynamic distribution of indoor air flow field and temperature field of a building according to claim 5, characterized in that: In step S4, the temperature T of the three-dimensional grid unit at each moment i (n) The expression is as follows: V i ·r i (n)·c p ·(T i (n+1)-T i (n)) / τ= Σ j m i,j (n)·c p ·(T j (n)-T i (n))+C B ·A i,j ·(T j (n)-T i (n))+Σ sou Q i,sou Among them, c p represents the specific heat capacity of air; T i (n) represents the air temperature of the three-dimensional grid cell i at time n; j represents the three-dimensional grid cell j adjacent to the three-dimensional grid cell i; C B represents the temperature difference heat transfer coefficient; Q i,sou It represents the cold / heat flow intensity provided by the cooling and heating source sou to the three-dimensional grid unit i.

7. The method for predicting the dynamic distribution of indoor air flow and temperature fields of a building according to claim 5, characterized in that: In step S4, the air pressure, momentum force, viscosity force and gravity between the three-dimensional grid unit i and the three-dimensional grid unit j are obtained by processing according to the following formulas: F R,P,i,j (n)=A i,j ·(P i (n+1)-P j (n+1)) F R,M,i,j (n)=A i,j ·ρ i,j (n)·(v R,i (n)-v R,j (n)) F R,V,i,j (n)=(F R,V,i (n)+F R,V,j (n)) / 2 F R,G,i,j (n)=-ρ i,j (n)·g·A i,j ·l R,i,j ,R∈{X,Y,Z} Among them, v R,i (n) represents the component of the vector velocity of the three-dimensional grid cell i in the R-axis direction at time n; v R,j (n) represents the component of the vector velocity of the three-dimensional grid unit j in the R-axis direction at time n; F R,V,i (n) represents the component of the viscosity force of the three-dimensional grid unit i in the R-axis direction at time n; F R,V,j (n) represents the component of the viscosity force of the three-dimensional grid unit j in the R-axis direction at time n; P i (n+1) represents the air pressure of three-dimensional grid unit i at time n+1; g represents the acceleration due to gravity.

8. The method for predicting the dynamic distribution of indoor air flow field and temperature field of a building according to claim 7, characterized in that: In step S4, the components of the viscosity of the three-dimensional grid unit i in the X, Y, and Z axis directions are obtained by processing the vector velocity according to the following formula: F Z,V,i (n)=μ·(((△v Z,i,k1 / L X,i,k1 )-(△v Z,i,k2 / L X,i,k2 ))·HAS i,k1 +((△v Z,i,k3 / L Y,i,k3 )-(△v Z,i,k4 / L Y,i,k4 ))·HAS i,k3 ) F X,V,i (n)=μ·(((△v X,i,k3 / L Y,i,k3 )-(△v X,i,k4 / L Y,i,k4 ))·HAS i,k3 +((△v X,i,k5 / L Z,i,k5 )-(△v X,i,k6 / L Z,i,k6 ))·HAS i,k5 ) F Y,V,i (n)=μ·(((△v Y,i,k5 / L Z,i,k5 )-(△v Y,i,k6 / L Z,i,k6 ))·HAS i,k5 +((△v Y,i,k1 / L X,i,k1 )-(△v Y,i,k2 / L X,i,k2 ))·HAS i,k1 ) Where μ represents the apparent viscosity coefficient of turbulence and boundary layer; △v R,i,j Represents the vector velocity time difference, △v R,i,j =v R,i,j (n+1)-v R,i,j (n), v R,i,j (n) represents the component of the vector velocity difference between the three-dimensional grid cell i and the three-dimensional grid cell j in the R-axis direction at time n, j∈{k1, k2, k3, k4, k5, k6}, wherein subscript k1 represents the three-dimensional grid cell k1 adjacent to the three-dimensional grid cell i along the negative direction of the X-axis, subscript k2 represents the three-dimensional grid cell k2 adjacent to the three-dimensional grid cell i along the positive direction of the X-axis, subscript k3 represents the three-dimensional grid cell k3 adjacent to the three-dimensional grid cell i along the negative direction of the Y-axis, subscript k4 represents the three-dimensional grid cell k4 adjacent to the three-dimensional grid cell i along the positive direction of the Y-axis, subscript k5 represents the three-dimensional grid cell k5 adjacent to the three-dimensional grid cell i along the negative direction of the Z-axis, and subscript k6 represents the three-dimensional grid cell k6 adjacent to the three-dimensional grid cell i along the positive direction of the Z-axis; F Z,V,i (n), F X,V,i (n), F Y,V,i (n) represents the components of the viscosity of the three-dimensional grid unit i in the X, Y, and Z axis directions at time n, respectively.

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