Methods for adjusting the uniformity of airflow in air outlet ducts

Abstract

This application relates to a ventilation and heat dissipation method, providing an air outlet duct for installation in a factory building. The air outlet duct is divided into several gradually narrowing sections from upstream to downstream, and each section has at least one air outlet to provide several downward airflows. The method for adjusting the air outlet uniformity of the air outlet duct mainly includes: a geometric design step for the height of at least one air outlet duct and the air outlet, a geometric design step for at least one air outlet duct, and a design step for the location configuration of at least one air outlet duct in the factory building, so as to reduce the temperature and pollutant concentration in the factory building.

Description

Technical Field

[0001] This application relates to an air outlet duct and a method for adjusting the uniformity of the air outlet, and more particularly to an air outlet duct and a method for adjusting the uniformity of the air outlet that can effectively reduce the temperature and pollutant concentration in a factory. Background Technology

[0002] In typical factory workshops, if there are many workers and the machines generate heat that cannot be removed outside, the temperature inside the workshop will rise. When the workshop needs to maintain low dust levels, using ordinary ventilation methods will allow dust to be easily drawn into the room through open windows and doors.

[0003] For example, in a factory manufacturing plastic bags, which contains heating machines, all windows are closed to prevent dust from adhering to the bags. Only louvered vents on the walls remain open. This results in high temperatures inside the factory, making it difficult to separate individual plastic bags, and dust is unavoidable. Similarly, in a factory manufacturing sneakers and belts, which also contains heating machines and requires low dust levels to prevent dust from adhering to the shoes and belts during the "gluing and pressing" process, all windows on the left and right walls are closed. However, to improve ventilation and prevent overheating, multiple exhaust fans are installed in the rear windows, and the doors and windows on the front walls are left open. But apart from the area near the front windows, most areas of the factory are almost windless. Therefore, many "intermediate fans" are installed above the doors and windows, presumably to allow smooth airflow from the front windows to the exhaust fans at the rear. However, this results in a large amount of dust being drawn into the factory through the front windows, keeping the factory still hot. Installing filters on windows and doors to filter dust would significantly reduce the airflow of axial fans and increase energy consumption due to pressure loss caused by filter blockage. Cleaning and maintaining the filters would be time-consuming and labor-intensive, and it wouldn't be very effective in preventing dust from entering the factory. Therefore, installing filters in every open window and door presents practical difficulties.

[0004] To address the aforementioned issues of heat and dust, a common practice is the "dilution and pressurization method." This involves supplying filtered, clean air ("cool," "warm," or "normal temperature") into the factory using fans, mixing it with the existing indoor air (dilution). Adjusting the opening of windows creates sufficient pressure loss (resistance) as the airflow overflows, preventing dust from entering the factory and reducing both the temperature and pollutant concentration. However, the basic principle of dilution in traditional ventilation textbooks and manuals is based on the assumption that the spatial distribution of pollutant concentration in a room is "uniform" at any given moment. This approach is not applicable to the complex conditions of actual factories. Summary of the Invention

[0005] In view of this, in order to provide a structure that is different from the prior art and to improve the above-mentioned shortcomings, the inventors of this application have accumulated many years of experience and continuous research and development, resulting in this application.

[0006] One objective of this application is to address the problem that existing ventilation and heat dissipation technologies are still unable to effectively reduce the temperature and pollutant concentration inside the factory in practical applications, and to provide an air outlet duct and a method for adjusting the uniformity of the air outlet to reduce the temperature and pollutant concentration inside the factory.

[0007] To achieve the above objectives, the air outlet duct of this application is designed for installation in a factory building. The air outlet duct has an upstream end and a downstream end. The air outlet duct is divided into several gradually narrowing sections from the upstream end to the downstream end. Each of the several sections has at least one air outlet for outputting downward airflow.

[0008] The method for adjusting the airflow uniformity of the exhaust duct in this application is provided in a factory building. The factory building includes a roof and several side walls arranged sequentially below the roof. The roof and the side walls together enclose an interior space. At least one exhaust duct is provided above the interior space to provide several downward airflows. At least one window for air supply and exhaust is provided on at least one side wall. The method for adjusting the airflow uniformity of the exhaust duct includes the following steps: A. A step of designing the height and geometry of the exhaust duct and the outlet, which involves selecting and adjusting the minimum installation height h and the outlet length d of the at least one exhaust duct using a database. j Width w j Spacing ratio s j / d j Number of air outlets N j Average wind speed at the air outlet, u j B. At least one outlet duct geometry design step, which first performs a preliminary design based on the basic principles of fluid mechanics, and then uses a CFD computer program to calculate and design the geometry (length Lduct, width Wduct, height Hduct) of at least one outlet duct to ensure that the maximum wind speed or flow rate non-uniformity of several outlets reaches a satisfactory low value; and C. At least one outlet duct location configuration design step in the plant, which uses a CFD computer program to estimate and adjust the flow field, temperature field, and concentration field in the plant to adjust the horizontal position and height of at least one outlet duct and the height of at least one window so that the wind speed, temperature, and concentration in the plant reach the required values.

[0009] In practice, the side walls include a first side wall, a third side wall, a second side wall, and a fourth side wall that are arranged sequentially, with the first side wall parallel to the second side wall.

[0010] During implementation, the first side wall and the second side wall each have at least one window for ventilation.

[0011] In practice, at least one end of an air outlet duct is connected to the first side wall, and the other end of at least one air outlet duct is connected to the second side wall, so that at least one air outlet duct is perpendicular to the first side wall and the second side wall respectively.

[0012] In practice, this application further provides at least one baffle, which is located at the same horizontal level as at least one pipe.

[0013] In practice, at least one partition is a flat plate with a high thermal insulation coefficient to block radiant heat emanating downwards from the roof.

[0014] To further understand this application, preferred embodiments are described below, along with drawings and reference numerals, to explain in detail the specific composition and effects achieved by this application. Attached Figure Description

[0015] Figure 1 This is a three-dimensional view of the preferred embodiment of the air outlet duct of this application installed in a factory building.

[0016] Figure 2 for Figure 1 Side view.

[0017] Figure 3 This is a flowchart illustrating the overall parameter design of the plant for this application.

[0018] Figure 4 This is a schematic diagram of the design parameters for the height of the air outlet duct and the geometry and configuration of the air outlet in step A of this application.

[0019] Figures 5-7 This is a flowchart illustrating the design process of the factory's air outlet duct height and outlet geometry for step A of this application.

[0020] Figure 8 This is a diagram defining the 50% non-uniformity of step A in this application.

[0021] Figure 9 , Figure 10 This is part of the database for step A of this application.

[0022] Figure 11 This is a schematic diagram of the blowing pipe with jet direction control for step B of this application.

[0023] Figure 12 This is a flowchart of the air outlet duct design for method (A) in step B of this application.

[0024] Figure 13 This is a side view of step B of this application, which divides the air outlet duct into several sections from upstream to downstream.

[0025] Figure 14 This is the original design drawing of an air outlet duct in step B of this application.

[0026] Figure 15 This is a velocity field diagram of the inside of the adjusted air outlet duct and the outside of the air outlet for step B of this application.

[0027] Figure 16 This is a static pressure distribution diagram inside the adjusted air outlet duct in step B of this application.

[0028] Figure 17 The maximum wind speed u at each air outlet before and after adjustment in step B of this application. jm,i Statistical table.

[0029] Figure 18 For step B of this application, the airflow Q at each outlet before and after adjustment j,i Statistical table.

[0030] Figure 19 The percentage improvement in the overall non-uniformity t of the maximum air velocity at the air outlet before and after the adjustment in step B of this application.

[0031] Figure 20 For step B of this application, the cross-sectional area A of each section of the air outlet duct before and after adjustment is... duct,i Statistical table.

[0032] Figure 21 This is the original air outlet duct design parameter table before adjustment in step B of this application.

[0033] Figure 22 This is the adjusted air outlet duct design parameter table for step B of this application.

[0034] Figure 23 This is a table of design parameters for the air outlet adjuster before and after step B of this application.

[0035] Figure 24 This is a flowchart illustrating the design of step C in this application.

[0036] Figure 25 This is a tracking gas distribution diagram for step C of this application.

[0037] Figure 26 , Figure 27 This is a table of plant design parameters for step C of this application.

[0038] Figure 28 The diagram shows four different air outlet duct configurations for step C of this application.

[0039] Figure 29 This is a case study of step C of this application, using a CFD computer program to analyze and calculate the statistical table of speed, temperature, concentration, and pressure in the plant's operating area.

[0040] Figure 30 This is a schematic diagram of the exterior of a factory building, representing another example of a building with partitions in this application.

[0041] Figure 31 for Figure 30 Side view.

[0042] Figure 32 , Figure 33 This is a table of plant design parameters for another example of step C in this application.

[0043] Figure 34 This is another example of step C in this application, showing the velocity vector and streamline distribution in a cross section with y = 3m on the side elevation.

[0044] Figure 35 This is another example of step C in this application, showing the temperature field distribution in a section with y = 3m on the side facade.

[0045] Figure 36 This is a concentration field distribution diagram in a cross section with y = 3m on the side facade, representing another example of step C in this application.

[0046] Figure 37 This is another example of step C in this application, showing the velocity vector and streamline distribution in the section at y = 3m on the end view elevation.

[0047] Figure 38 This is another example of step C in this application, showing the temperature field distribution in a section at y = 3m on the end view elevation.

[0048] Figure 39 This is a concentration field distribution diagram in a section with y = 3m on the end view facade, representing another example of step C in this application.

[0049] Figure 40 This is another example of step C in this application, showing the velocity vector and streamline distribution in a cross-section at z = 1.8m on a top-down horizontal plane.

[0050] Figure 41 This is another example of step C in this application, showing the temperature field distribution in a cross-section at z = 1.8m on a horizontal plane viewed from above.

[0051] Figure 42 This is another example of step C in this application, showing the concentration field distribution in a cross-section at z = 1.8 m on a top-down horizontal plane.

[0052] Figure 43 This is a statistical table of speed, temperature, concentration, and pressure in the factory operation area, which is another example of step C in this application.

[0053] Figure 44 This is a comparison graph showing the average speed of two cases in step C of this application—one with and one without partitions—with the original plant.

[0054] Figure 45This is a comparison chart of the temperature in step C of this application, showing two cases: one with and one without partitions, compared to the original plant.

[0055] Figure 46 This is a comparison graph showing the concentration of two cases in step C of this application—one with and one without partitions—with the original plant.

[0056] Figure 47 This is a comparison diagram of the pressure of two cases, one with and one without partitions, in step C of this application, compared to the original plant.

[0057] in,

[0058] 10: Air outlet duct; 101: Upstream end;

[0059] 102: Downstream end; 103: Section;

[0060] 104: Air outlet; 1: Factory building;

[0061] 11: Roof; 12: First side wall;

[0062] 13: Third side wall; 14: Second side wall;

[0063] 15: Fourth side wall; 16: Interior space;

[0064] 17: Window; 18: Partition. Detailed Implementation

[0065] Please see Figure 1 , Figure 2 As shown, the air outlet duct 10 of this application is installed in a factory building 1. The factory building 1 mainly includes a roof 11 and a first side wall 12, a third side wall 13, a second side wall 14, and a fourth side wall 15 arranged sequentially and continuously around the roof 11. The first side wall 12 and the second side wall 14 are parallel to each other. The four side walls form a rectangle and together with the roof 11, they form an interior space 16. At least one air outlet duct 10 is located above the interior space 16. In this embodiment, the four air outlet ducts 10 are spaced apart and parallel to the third side wall 13 and the fourth side wall 15. Each air outlet duct 10 has an upstream end 101 and a downstream end 102 according to the air flow direction. Each air outlet duct 10 is divided into several gradually narrowing sections 103 from the upstream end 101 to the downstream end 102. The lower half of each section 103 of each air outlet duct 10 has at least one air outlet 104 arranged at intervals for outputting downward airflow. The first side wall 12 and the second side wall 14 each have several horizontally spaced windows 17 for exhausting air outwards.

[0066] The method for adjusting the air outlet uniformity of the air outlet duct in this application includes the following steps:

[0067] A. The geometric design steps for the height of at least one air outlet duct 10 and the air outlet 104 involve selecting and adjusting the minimum installation height h of at least one air outlet duct 10 and the length d of the air outlet 104 from the data bank. j Width w j Spacing ratio s j / d j Number of air outlets: 104 (N) j Average wind speed at the air outlet: 104 j .

[0068] B. At least one air outlet duct 10 geometric design steps, which first involves a preliminary design based on the basic principles of fluid dynamics, and then uses a Computational Fluid Dynamics (CFD) computer program to calculate and design the geometric dimensions (length L) of the air outlet duct 10. duct Width W duct High H duct) This is to ensure that the maximum wind speed or flow rate unevenness at each air outlet reaches a satisfactory low value.

[0069] C. The design steps for the location configuration of at least one air outlet duct 10 in the plant 1 are to use a CFD computer program to estimate and adjust the flow field, temperature field and concentration field in the plant 1, so as to adjust the horizontal position and height of the air outlet duct 10 and the height of the window 17, so that the wind speed, temperature and concentration in the plant 1 reach the required values.

[0070] Prior to step A, this embodiment further provides a process for designing the overall parameters of the plant, which is a method for initially estimating the required air volume based on thermodynamic principles and overall parameters; the flowchart of the overall parameter design for plant 1 is as follows. Figure 3 As shown. The overall design parameters aim to supply filtered air or cool air from the outside into Plant 1, diluting the high temperature and pollutant concentration inside Plant 1, and maintaining positive pressure inside Plant 1. This reduces and dilutes the temperature and pollutant concentration inside Plant 1, and also reduces the chance of dust from outside entering Plant 1 through doors, windows, openings, and gaps.

[0071] When designing the overall parameters of factory building 1, the impact of the "heat generation rate" of human beings and machines must be considered when designing the air intake volume. If the machine surface is properly insulated and the machine exhaust heat and pollutants are removed through "local ventilation facilities", then only the heat generation of human beings needs to be considered. However, the intake volume of the "local ventilation facilities" must be added to the "required air intake volume" calculated below.

[0072] Methods for estimating "demand air volumetric flow rate" include:

[0073] 1. Thermodynamic Estimation Method: If there is a "superheating" problem in the plant, assuming that the air in the plant maintains a homogeneous and equilibrium state during the gas supply process, the "theoretical required air volumetric flow rate" Q is estimated using the principles of "thermodynamics". theory If the total heat generation rate of people and machines in the factory is q, and the specific heat of air at room temperature is c. p The density is ρ, the temperature rise of air due to heat absorption inside the factory is ΔT, the "theoretical required air mass flow rate" is m, and the "theoretical required air volume flow rate" is Q. theory According to the principles of thermodynamics, the relationship between the above parameters can be written as:

[0074] q = mc p ΔT=(ρQ theory )c p ΔT,

[0075] Therefore Q theory =q / (ρc p ΔT)

[0076] If the "allowable temperature rise" ΔT is set, the "theoretical required air volumetric flow rate" Q can be calculated using the above formula. theory [Note: Set the allowable temperature rise of indoor air ΔT (e.g., 0.1℃, 0.2℃, or 0.3℃). If a "cooler" is installed upstream of the air supply fan, the temperature inside the plant can reach a lower temperature than the outside air; if no "cooler" is installed, the temperature inside the plant can only be approximately the same as the outside air temperature.] Typically, the "actual required air volumetric flow rate" Q... total The "theoretical required air volumetric flow rate" Q will be included. theory Multiply by a safety factor k (≥1):

[0077] Q total =kQ theory

[0078] If the "allowable temperature rise" ΔT is set, the "actual required air volumetric flow rate" Q can be calculated using the formula on the previous page. total And if Q total If the value of Q is too large and exceeds a reasonable range, the following three methods can be used to adjust it to reduce Q. total Demand:

[0079] (a) Increase ΔT to an acceptable value to reduce Q. total ;

[0080] (b) Install a "cooler" upstream of the air supply fan. If the "cooler" is air conditioning, a small amount of "cooled air" can be mixed into the supply air via a bypass. This only requires slightly lowering the temperature of the supply air to provide sufficient margin for adjusting Q within ΔT.total The same effect can be achieved if the "cooler" is of another type;

[0081] (c) Installing "local ventilation facilities" in heat-generating machines to reduce Q total Value (but remember to add the intake volume of the "local ventilation system" to the final calculated "required intake volume" Q). total middle).

[0082] 2. Estimation Method for Upper Limit of Pollutant Mass Concentration Demand: If there is a problem of "excessive pollutant concentration" in the plant, assuming that the air in the plant remains homogeneous and in equilibrium during the gas supply process, the upper limit of pollutant mass concentration [mass fraction] demand value f is used. p and the mass production rate m of pollutants p Estimate the "theoretical required air mass flow rate" m:

[0083] f p =m p / (m+m p ),

[0084] Therefore, m = m p (1-f p ) / f p

[0085] Dividing the theoretical demand air mass flow rate m by the density ρ of the supplied air yields the theoretical demand air volume flow rate Q. theory :

[0086] Q theory =m / ρ

[0087] Then use equation Q total =kQ theory Calculate the "actual demand air volumetric flow rate" Q total .

[0088] 3. Taking advantage of adjusting the "total area of ​​window openings" A in the factory building win To change the wind speed at which air flows out of the window. win And the "positive pressure" (the pressure inside the factory is higher than the outside air pressure) ΔP win Size. Air velocity V of the airflow exiting the factory building through the windows. win :

[0089] V win =Q total / A win

[0090] Positive pressure ΔP inside the factory winAssuming the window's pressure loss coefficient C0≈0.5~0.6,

[0091] ΔP win =C0(ρV win 2 ) / 2

[0092] 4. The total area A of the factory building's window openings needs to be calculated repeatedly. win Even adjust ΔT to make Q total With the positive pressure ΔP in the room win With wind speed V win To reach an appropriate and feasible value.

[0093] Steps A, B, and C involve techniques for guiding and distributing airflow, requiring details of "fluid dynamics." Step A specifically involves the design of at least one duct height and outlet geometry. The purpose of this design is to:

[0094] 1. After the airflow is ejected from multiple parallel air outlets in the air duct, it needs to travel a certain distance to diffuse before reaching a person's head, in order to reduce the average airflow velocity upon reaching the person's head. "and "spatial non-uniformity of airflow velocity distribution" "Only when the target value is reached will people not feel uncomfortable."

[0095] (1) When a person's head is exposed to high-speed airflow (especially cold air) for a long time, the average speed of the airflow at the height of the head should be kept as constant as possible.

[0096]

[0097] (2). If "the spatial distribution non-uniformity of airflow velocity" "If the airflow is too large, the jet velocity will be too high below the air outlet; in areas away from the air outlet, the airflow velocity will be too low. The airflow velocity distribution at head height should be made as uneven as possible." (Unevenness tolerance can also be customized).

[0098] 2. The average air velocity u at the outlet of at least one air outlet duct. j 1. Air outlet geometry (length d) j Width w j Spacing ratio s j / d j This will affect the magnitude of the "multi-jet evolution distance". Therefore, it is necessary to use CFD calculations and analysis to establish a data bank to design the desired average airflow velocity ratio at a selected head height. and acceptable spatial distribution non-uniformity Derivation distance (i.e., the minimum distance y* from the air outlet to the top of a person's head). At least one air outlet duct should be installed at a height h equal to or greater than a person's height h. p Add the minimum distance y* from the air outlet to the top of a person's head, that is: h≥h p +y*.

[0099] 3. Obtain the number N of air outlet ducts according to [Step A]. duct Minimum installation height h of air outlet duct, length d of air outlet j Width w j Spacing ratio s j / d j Average velocity u at the air outlet j Next, proceed to [Step B] to design the geometry of the air duct (L) duct W duct H duct This is to ensure that the air velocity uniformity at the air outlet meets the requirements.

[0100] like Figure 4 As shown, it is a schematic diagram of the design parameters for the height of at least one air outlet duct and the geometry and configuration of the air outlet in the factory building.

[0101] Figures 5-7 A flowchart for the design of the height of the air outlet duct and the geometry of the air outlet in the factory.

[0102] Figure 8 The diagram defines the 50% non-uniformity.

[0103] Figure 9 , Figure 10 This is a partial data bank.

[0104] Example of at least one exhaust duct height and exhaust outlet geometry design in a factory: In the design example of step A, the required Q for a plastic bag factory with (length L × width W × height H) = (15m, 12m, 15m) to achieve ΔT = 0.2℃ has been obtained. total =1536 CMM. Using the [Step A] design method of the dilution and pressurization approach, design: minimum installation height h of the outlet duct and length d of the outlet. j Width w j Spacing ratio s j / d j Number of air outlets N j Total area of ​​air outlet A j Average wind speed at the air outlet, u j To achieve the average airflow speed at head height Spatial non-uniformity of airflow velocity distribution

[0105] The calculation procedure is as follows:

[0106] 1. Based on the estimated air volume Q in [Step A] total Select a suitable number of air outlet ducts N duct Calculate the flow rate Q of a single outlet duct. duct =Q total / N duct :

[0107] Q is obtained from [Step A] total =1536CMM, assuming the "number of air outlet ducts" is N duct =4, thus obtaining

[0108] Q duct =1536 / 4=384CMM.

[0109] 2. Select the height h of the human head. p =1.8m:

[0110] If the minimum height of the planned exhaust duct is h = 7m, then y* = hh p =7-1.8=5.2m.

[0111] 3. Select "Exhaust vent length" d j =0.3m, calculate y* / d j :

[0112] y* / d j =5.2 / 0.3=17.33.

[0113] 4. Using the 50% non-uniformity boundary chart, find s j / d j Available range:

[0114] s j / d j ≤5.84.

[0115] 5. Choose an s j / d j Value, based on d j y* / d j h / d j The values ​​were used to confirm the spatial non-uniformity of airflow velocity distribution in Data Bank A.

[0116] Select "Outlet Spacing Ratio" j / d j =5, based on d j y* / d j s j / d j The numerical value was used to confirm the spatial non-uniformity of airflow velocity distribution in database A. This is acceptable.

[0117] 6. Calculate s j :

[0118] s j =(s j / d j )×d j =5 × 0.3 = 1.5m.

[0119] 7. Calculate the number N of air outlets in the air duct. j :

[0120] Length L of the air outlet duct duct =15m (same as the factory building length), set the air outlets near the walls on both sides of the air duct to be 2m away from the walls. Calculate N. j =[(15-2×2-0.3) / 1.5]+1=8.13. Choose N. j =9 → Acceptable.

[0121] 8. Using the selected N j Recalculate s j :

[0122] With N j =9 calculations s j =[(15-2×2-0.3) / (9-1)]=1.338m, so s j / d j =1.338 / 0.3 = 4.46. (d) j y* / d j s j / d j The corresponding spatial distribution non-uniformity of airflow velocity was confirmed again in the data bank. Acceptable.

[0123] 9. Based on s j / d j d j y* / d j h / d j The value is found in Data Bank B, which contains the corresponding average airflow velocity ratio. get

[0124] 10. Set the desired reward at the head of the target. calculate

[0125] Set the desired average airflow velocity at the head position. calculate

[0126]

[0127] Take w j =0.5m → acceptable.

[0128] Recalculate

[0129] Acceptable.

[0130] 11. Calculate A j =d j ×w j =0.3 × 0.5 = 0.15m 2 .

[0131] 12. Calculate A j,total =N j ×A j =9 × 0.15 = 1.35m 2 .

[0132] 13. Calculate u j =Q duct / A j,total =384 / 60 / 1.35=4.74m / s → Acceptable.

[0133] 14. Using the obtained minimum installation height h = 7m for the air outlet duct and the air outlet length d, j =0.3m, width w j =0.5m, spacing ratio s j / d j =4.46, Number of air outlets N j =9. Average wind speed at the air outlet, u j =4.74m / s. [Step B] Design the geometric dimensions of the air outlet duct.

[0134] Step B is the geometric design step for the air outlet duct. The purpose of this design is to address the issue that when air is delivered into the air outlet duct and then ejected from "outlets" located at different positions along the duct's length (e.g., in HVAC applications: air supply ducts for ventilation systems, ducts delivering cool or warm air, etc.), if the air outlet flow rate, duct size, outlet velocity, or flow uniformity are not properly designed, in most applications delivering sufficient airflow, the uneven static pressure distribution within the duct, increasing from upstream to downstream, leads to an increase in the jet velocity at the outlet from upstream to downstream. This makes it difficult to obtain a "uniformly distributed" airflow, and the jet direction is difficult to control. Therefore, a method is needed to achieve acceptable "airflow distribution" and "direction adjustment."

[0135] Methods for adjusting the air velocity and direction at the air outlet of the air duct: (e.g.) Figure 11As shown, the jet direction at the air outlet is controlled by an empty pipe or guide vanes. Using CFD calculations, the guide vane length and the gap between adjacent guide vanes are adjusted to achieve the target jet direction. The method for adjusting the uniformity of the air outlet velocity or flow rate is based on the cross-sectional area A of the air outlet duct. duct The method involves a gradual narrowing from upstream to downstream. This method reduces the cross-sectional area A of the outlet duct. duct The flow rate is gradually reduced from upstream to downstream to adjust the static pressure distribution within the pipe, thereby adjusting the uniformity of the outlet velocity or flow rate.

[0136] like Figure 12 As shown, it represents the cross-sectional area A of the air outlet duct. duct A flowchart illustrating the design process of an air outlet duct using a gradual tapering method from upstream to downstream. (See attached diagram.) Figure 13 As shown, in the initial design, the air outlet duct 10 is divided into several sections 103 from the upstream end 101 to the downstream end 102, assuming that the velocity at each air outlet 104 is u. j =Q duct / A j,total Furthermore, the velocity of each section 103 of the air outlet duct 10 is the same as the velocity u at the air outlet duct inlet. duct Then, according to the law of conservation of mass, the initial cross-sectional area A of each section 103 is determined. duct,i .

[0137] Assuming the airflow is an ideal fluid with no pressure loss within the outlet duct, then according to Bernoulli's principle (the static pressure P without water...),... hs =When γh changes, the dynamic pressure P v +static pressure P s =constant), if the velocity in each section of the air outlet duct is u duct Then the dynamic pressure P v Since the static pressure P is equal in all sections of the air outlet duct, it is equal in all sections. s The static pressure will also be equal in all sections of the pipe (i.e., the total pressure is equal in all sections of the outlet duct); consider Bernoulli's law again at the outlet: when the static pressure in each section of the pipe or the static pressure near each outlet of the outlet duct is equal to P... s When they are equal, the velocity u of each air outlet j Therefore, based on the law of conservation of mass and Bernoulli's principle, the initial design ensures that the velocity in each section of the air outlet duct is u. duct And the velocity of each air outlet is u j =Q duct / A j,total This allows us to determine the initial cross-sectional area of ​​each section of the air outlet duct.

[0138] It is more appropriate to arrange one air outlet in a duct with the same cross-sectional area. If the duct is too long or there are too many air outlets, several air outlets can be arranged in a duct with the same cross-sectional area; however, in this arrangement, the air velocity of the upstream air outlet will be lower than that of the downstream air outlet in the same duct with the same cross-sectional area.

[0139] Furthermore, since real fluids inevitably have viscosity, there will be pressure losses in each section of the outlet duct, so corrections are necessary. The flow field distribution is calculated using CFD, and the cross-sectional area A of each section of the outlet duct is adjusted based on the calculation results. duct,i To make the air outlet speed u j Uniform. The initial cross-sectional area A is typically used. duct,i The calculated flow field distribution shows a degree of uniformity at the upstream and midstream outlets of the duct, but the jet velocity at several downstream outlets is lower than that at the upstream and midstream outlets. If A is further adjusted... duct,i (Simultaneously reduce upstream A) duct,i With increasing the A in the middle and lower reaches duct,i This can improve the uniformity of air outlets throughout the entire air duct.

[0140] If several air outlets are arranged in an air outlet duct with the same cross-sectional area, the air velocity of the upstream outlet will be lower than that of the downstream outlet. To correct this problem, the air outlet duct with the same cross-sectional area can be made to gradually narrow downstream. Alternatively, using a certain Q... duct After completing the configuration and geometry of the air outlet duct and outlet according to the design, and obtaining satisfactory air outlet velocity uniformity, if Q is changed within a certain range... duct If the value is changed, the air outlet velocity unevenness will only change slightly. For example, in the following case A, the original Q... duct Within 0.4 to 5 times the value, the change in unevenness can be roughly ignored.

[0141] Maximum velocity u of each air outlet in the air duct jm,i non-uniformity η t definition:

[0142]

[0143] u jm,i Maximum speed of each air outlet

[0144] u jm,ave The average maximum velocity of all air outlets

[0145] The flow rate Q of each air outlet in the air duct j,i non-uniformity η t definition:

[0146]

[0147] Q j,i The airflow of each air outlet

[0148] Q j,ave Average airflow from all air outlets

[0149] For example: 18m air outlet duct (9 air outlets in total, denoted by Q) duct =5.4m 3 / s) After the design is improved, if the flow rate is changed but the same design is maintained, the non-uniformity η t,u The changes are not significant, as shown in the two tables below.

[0150]

[0151]

[0152]

[0153] Maximum variation (%): The difference between the maximum and minimum air velocity at all air outlets of the air outlet duct, divided by the average value. Wherein, the cross-sectional area A of each section of the air outlet duct... duct,i The adjustment principles are as follows:

[0154] 1. Increase A duct,i It can increase the maximum speed of the air outlet. jm,i ; Decrease A duct,i It can reduce the maximum air velocity at the outlet. jm,i .

[0155] 2. Compare the maximum velocity u at each air outlet. jm,i Average of the maximum velocity u of all air outlets jm,ave ,

[0156] If u jm,i jm,ave →Add A duct,i ;

[0157] If u jm,i >u jm,ave → Decrease A duct,i .

[0158] Adjust back and forth until an acceptable velocity distribution is obtained.

[0159] Case A: The original design of an air outlet duct is as follows Figure 14 The original duct velocity field inside and outside the air outlets, after CFD analysis, shows that the air velocity at each outlet is extremely uneven. Please design a method to increase the uniformity of the air velocity at each outlet.

[0160] The design adjustment process is as follows:​

[0161] 1. Lduct = 18m, divided into 9 sections, each with 1 air outlet.

[0162] 2. After four design adjustments, the velocity fields inside the air outlet duct and outside the air outlet are as follows: Figure 15 As shown, the velocity distribution at each air outlet is relatively uniform; the static pressure distribution inside the air outlet duct is as follows. Figure 16 As shown, the static pressure in the area above the air outlet is relatively uniform.

[0163] 3. Figure 17 , Figure 18 To adjust the process statistics table, among which, Figure 17 The maximum wind speed u at each air outlet jm,i Statistical table, based on

[0164] The initial design, based on the principles of "mass conservation" and "Bernoulli's principle," significantly improved the problem of "severely uneven air velocity at each outlet" in the "straight pipe." However, the air velocity distribution became: the upstream outlets had higher velocities than the downstream outlets, while the velocities at the last few outlets were too low. By subsequently adjusting the outlet duct dimensions back and forth according to the initial design (reducing the size of the upstream outlet duct and increasing the size of the mid-to-downstream outlet ducts), the flaws in the initial design could be effectively corrected, and its comparison η... t,u0 =40.0%.

[0165] 4. Figure 18 The airflow Q at each outlet j,i Statistical table, where u jm,i With Q j,i Uniformity may not be possible to achieve simultaneously; it is best to select the appropriate value based on actual needs before designing. jm,i Or Q jm,i As a criterion for judging uniformity, a design procedure is implemented to adjust the cross-sectional area of ​​each outlet duct, and its comparison η t,Q0 =61.4%.

[0166] 5. Figure 19 The overall non-uniformity of the maximum air velocity at the air outlet, η t Percentage improvement.

[0167] 6. Figure 20 Let A be the cross-sectional area of ​​each section of the air outlet duct. duct,i Statistical table, where A duct,1 ~A duct,3 Compared to the initial design A duct,i (#0) small; while A duct,4 ~A duct,9 Compared to the initial design A duct,i (#0) Big.

[0168] 7. Figures 21-23A table summarizing the design parameters for the air outlet duct. Among them, Figure 21 These are the original air outlet duct design parameters. Figure 22 The adjusted design parameters for the air outlet duct. Figure 23 These are the design parameters for the air outlet regulator.

[0169] Step C is the design process for the location and configuration of the factory's air outlet ducts, and its design flowchart is as follows: Figure 24 As shown. The purpose of designing the location of the factory's air outlet duct is to: after completing steps B and C, the required total air volume Q has been obtained. total Total window area A win Single outlet air volume Q duct Number of air outlet ducts N duct 1. Geometric dimensions of the air outlet duct (L) duct W duct H duct ), air outlet length d j Width w j Spacing ratio s j / d j Number of air outlets N j 1. Minimum installation height h of the air outlet duct. Step C requires adjusting the horizontal position and height of the air outlet duct installation, as well as the window configuration / height. The horizontal position and height of the duct installation, along with the window configuration / height, affect the airflow pattern within the plant, consequently influencing the distribution of temperature and concentration. Without proper design, the velocity, temperature, and concentration distribution within the plant may be extremely uneven. This step uses CFD calculations to adjust the flow field, temperature field, and concentration field within the plant to achieve the required distribution and values ​​for air velocity, temperature, and concentration.

[0170] The design principles for the configuration of air outlet ducts in the factory are as follows:

[0171] 1. The configuration method of concentrating the air outlet ducts on one side of the factory will generate large backflow bubbles in the factory. Compared with the air outlet ducts being evenly distributed in the factory or concentrated in the central area, the airflow in the work area has a higher average velocity, but there will be a higher and more uneven distribution of pollutant concentrations.

[0172] 2. Distributing the exhaust ducts evenly throughout the factory or concentrating them in the central area will create many small backflow bubbles in the factory. Compared with concentrating them on one side of the factory, the airflow in the work area will have a slightly lower average velocity, but there will be a lower and more uniform average concentration of pollutants.

[0173] 3. The average temperature of the work area obtained by the configuration method of evenly distributing the air outlet ducts in the factory building is similar to that obtained by the configuration method of concentrating the air outlet ducts on one side or in the central area of ​​the factory building. However, the temperature field of the work area is slightly more uniform when the air outlet ducts are evenly distributed in the factory building or concentrated in the central area than when they are concentrated on one side of the factory building.

[0174] 4. Comparing the distribution and values ​​of the flow field, temperature field, and concentration field in the work area, the order of superiority and inferiority of the air outlet duct distribution methods is:

[0175] <1> They are concentrated in the central region.

[0176] <2> They are evenly distributed throughout the factory buildings.

[0177] <3> They are concentrated on one side of the factory building.

[0178] 5. Lowering the outlet air temperature of the air duct near the heat source can reduce the average temperature of the working area and also reduce the temperature of the heat-generating machine.

[0179] 6. The relative orientation of the air outlet duct and the window affects the shape of the flow field, temperature field, and concentration field. The average velocity, temperature, and concentration in the operating area when the window is installed on the wall perpendicular to the air outlet duct axis and when the window is installed on the wall parallel to the air outlet duct axis are close to the theoretical values ​​of the overall parameter design; however, the local concentration field and temperature field distribution when the window is installed on the wall perpendicular to the air outlet duct axis are better than when the window is installed on the wall parallel to the air outlet duct axis.

[0180] 7. If the window height is adjusted from below the wall to above, the flow field, temperature field, and concentration field in the work area will all deteriorate slightly (the difference is not significant).

[0181] Example of factory ventilation duct configuration design: A factory manufacturing plastic bags, (length L × width W × height H) = (15m, 12m, 15m). There are 4 heat-generating machines (total heat output q = 5kW), which must be kept in a low-dust state to prevent dust from adhering to the plastic bags. It is desirable that the temperature difference between the inside of the factory and the outside air temperature ΔT < 0.5℃ to maintain product quality.

[0182] Among them, (Q) duct A win V win ΔP win ) = (1536 CMM, 6m 2 (4.27 m / s, 5.31 Pa); 12 windows, each window (0.625 m wide × 0.8 m high).

[0183] The following steps were designed using the dilution and pressurization method:

[0184] Step A: Number of ducts N duct =4. Flow rate Q per duct duct =384 cm², minimum duct installation height h = 7 m, outlet length d j =0.3m, width w j =0.5m, spacing ratio s j / dj =4.46, Number of air outlets N j =9. Average wind speed at the air outlet, u j = 4.74 m / s.

[0185] Step B: Cross-sectional area A of the air outlet duct duct The design using a gradual tapering method from upstream to downstream results in a 3.4% non-uniform maximum velocity and an 11.8% non-uniform air volume at each outlet.

[0186] Tracking gas release methods:

[0187] 1. Tracking gases: such as Figure 25 As shown, when calculating the concentration field, an average of 105 grid points were configured within the working area (z≤3m) (5 rows in the x direction, 7 rows in the y direction, and 3 rows in the z direction). Each grid point generates 2.85 mg / s of carbon monoxide (CO) as the tracking gas, for a total of m. p =300mg / s.

[0188] 2. Air supply: Q total =1536 cm / mm = 25.6 m 3 / s,

[0189] P=101325Pa, T=29℃, ρ=1.159kg / m 3 ,

[0190] rH = 55%

[0191] →m=Q total ×ρ=29.67kg / s,

[0192] 3. Expected average mass concentration f p Estimate:

[0193] Based on the formula for designing the overall parameters of the factory building in [Step A]

[0194] f p =m p / (m+m p )

[0195] →f CO =10.111ppm

[0196] Please also refer to Figure 1 , Figure 2 As shown, in this case, the windows are on the walls of the first side wall 12 and the second side wall 14 without partitions, and the horizontal position of the air outlet duct has been changed. The design parameters of the factory building 1 in this case are as follows: Figure 26 , Figure 27 As shown, the configurations of the air outlet duct 10 are as follows (a), (b), (c), and (d). Figure 28As shown. Based on the structure of the above embodiments, this application conducts simulation tests using the above parameters and analyzes the calculation results using a computer program of Computational Fluid Dynamics (CFD). The statistical table of velocity, temperature, concentration, and pressure in the plant operation area is as follows. Figure 29 As shown.

[0197] Please also refer to Figure 30 , Figure 31 As shown, this is another example with partitions 18. Several partitions 18 are spaced apart and arranged side-by-side below the roof 11. The partitions 18 and the air outlet duct 10 are at the same horizontal level, and the partitions 18 are flat ceiling panels with a high thermal insulation coefficient to block the radiant heat emitted downwards from the roof 11. The plant design parameters are shown in the table below. Figure 32 , Figure 33 As shown, the configuration of the air outlet ducts (a), (b), (c), and (d) are the same as in the previous case.

[0198] Based on the analysis and calculation results using CFD computer programs, the velocity vector and streamline distribution diagram in the side-view elevation section with y=3m is as follows: Figure 34 As shown; temperature field distribution diagram as follows Figure 35 As shown; concentration field distribution diagram as shown Figure 36 As shown. In the section at x = 3m on the end view elevation, the velocity vector and streamline distribution diagram are as follows. Figure 37 As shown; temperature field distribution diagram as follows Figure 38 As shown; concentration field distribution diagram as shown Figure 39 As shown. And in the cross-section viewed from above at a horizontal plane z = 1.8m, its velocity vector and streamline distribution diagram are as follows. Figure 40 As shown; temperature field distribution diagram as follows Figure 41 As shown; concentration field distribution diagram as shown Figure 42 As shown in the table. Based on the test results, the statistical table of velocity, temperature, concentration, and pressure in the factory operation area of ​​this case is as follows: Figure 43 As shown. The arrows represent velocity vectors, and the black lines along the tangent to the velocity vectors represent streamlines; the colored areas represent temperatures, with the roof specified at 60℃, red being the highest temperature (the temperature inside the roof is specified as 60℃), followed by brown, yellow, light green, bright green, light blue to dark blue (dark blue represents the atmospheric temperature, specified as 29℃). Additionally, as... Figures 44-47 The diagram shows two cases: one without partition 18 and the other with partition 18. The comparison charts show that the average velocity, temperature, concentration and pressure are superior to the original plant in both cases. The diagrams also show that the plant with and without partition 18 outperforms the original plant in terms of average velocity, temperature, concentration and pressure.

[0199] In summary, based on the content disclosed above, this application can indeed achieve the intended purpose, providing a factory ventilation and heat dissipation method that can create a positive pressure effect inside the factory, making the pressure inside the factory higher than the atmospheric pressure outside the factory, thereby effectively preventing dust from drifting into the factory, and reducing the temperature and even the concentration of pollutants inside the factory. This method has great industrial application value, and therefore, an invention patent application is filed in accordance with the law.

Claims

1. A method for adjusting the air outlet uniformity of an air outlet duct, characterized in that, The air outlet duct is designed for installation in a factory building. The duct has an upstream end and a downstream end, and is divided into several gradually narrowing sections from the upstream end to the downstream end. Each section has at least one air outlet for outputting downward airflow. The factory building includes a roof and several side walls arranged sequentially beneath the roof. The roof and the side walls together enclose an interior space. The air outlet duct provides several downward airflows above the interior space. At least one of the side walls has at least one window for air supply and exhaust. The method for adjusting the airflow uniformity of the air outlet duct includes the following steps: The overall parameter design steps for a factory building are as follows: based on the total calorific value q of the factory building, the allowable temperature rise ΔT is set, and the actual required air volumetric flow rate Q is estimated. total And according to the actual demand for air volumetric flow rate Q total Select a suitable number of air outlet ducts N duct Calculate the flow rate Q of a single outlet duct. duct =Q total / N duct ; A. The geometric design steps for the air outlet duct height and outlet are as follows: a database is established using CFD computer program calculation and analysis; the minimum installation height h of the air outlet duct and the outlet length d are selected and adjusted. j Width w j Spacing ratio s j / d j Number of air outlets N j Average wind speed at the air outlet, u j , where u j =Q duct / [Total area of ​​air outlet A] j ×N j ] = Q duct / [w j ×d j ×N j ] = Q duct / A j,total A j,total =A j ×N j ; B. The geometric design steps for this air outlet duct are as follows: First, a preliminary design is made based on the basic principles of fluid mechanics; then, the geometric dimensions of the air outlet duct are designed using a CFD computer program, with the cross-sectional area A of the air outlet duct as the basis. duct The method of gradually narrowing from upstream to downstream is used to adjust the static pressure distribution inside the pipe, and the flow field distribution is calculated using a CFD computer program. The cross-sectional area A of each section of the outlet duct is adjusted according to the flow field calculation results. duct,i To achieve an average air velocity u at the outlets of several air outlets. j Uniform; as well as C. The design steps for the location and configuration of the air outlet duct in the factory building involve using a CFD computer program to estimate and adjust the flow field, temperature field, and concentration field within the factory building, thereby adjusting the horizontal position and height of the air outlet duct installation relative to the height of at least one window. The installation height h of the air outlet duct is greater than or equal to the height h of a person. p Add the minimum distance y* from at least one air outlet to the top of a person's head to ensure that the wind speed, temperature, and concentration in the factory reach the required values.

2. The method for adjusting the air outlet uniformity of the air outlet duct as described in claim 1, characterized in that, The plurality of side walls include a first side wall, a third side wall, a second side wall and a fourth side wall arranged sequentially, and the first side wall is parallel to the second side wall.

3. The method for adjusting the air outlet uniformity of the air outlet duct as described in claim 2, characterized in that, The first side wall and the second side wall each have at least one window for ventilation.

4. The method for adjusting the air outlet uniformity of the air outlet duct as described in claim 3, characterized in that, One end of the air outlet duct is connected to the first side wall, and the other end of the air outlet duct is connected to the second side wall, so that the air outlet duct is perpendicular to the first side wall and the second side wall respectively.

5. The method for adjusting the air outlet uniformity of the air outlet duct as described in claim 1, characterized in that, It also provides at least one partition, which is located at the same horizontal position as the air outlet duct.

6. The method for adjusting the air outlet uniformity of the air outlet duct as described in claim 5, characterized in that, At least one partition is a flat plate with a high thermal insulation coefficient, designed to block radiant heat emanating downwards from the roof.

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