With this material, the editors of the magazine “Climate World” continue the publication of chapters from the book “Ventilation and air conditioning systems. Design guidelines for production
water and public buildings." Author Krasnov Yu.S.
The aerodynamic calculation of air ducts begins with drawing an axonometric diagram (M 1: 100), putting down the numbers of sections, their loads L (m 3 / h) and lengths I (m). The direction of the aerodynamic calculation is determined - from the most distant and loaded area to the fan. When in doubt when determining a direction, consider all possible options.
The calculation starts from a remote area: determine the diameter D (m) of the round or the area F (m 2) cross section rectangular duct:
The speed increases as you approach the fan.
According to Appendix H, the nearest standard values are taken: D CT or (a x b) st (m).
Hydraulic radius of rectangular ducts (m):
 |
where is the sum of the coefficients local resistance on the air duct section.
Local resistances at the border of two sections (tees, crosses) are assigned to the section with lower flow.
Local resistance coefficients are given in the appendices.
Calculation example
Initial data:
| No. of plots | flow L, m 3 / h | length L, m | υ rivers, m/s | section a × b, m |
υ f, m/s | D l,m | Re | λ | Kmc | losses in the area Δр, pa |
| PP grid at the outlet | 0.2 × 0.4 | 3,1 | — | — | — | 1,8 | 10,4 | |||
| 1 | 720 | 4,2 | 4 | 0.2 × 0.25 | 4,0 | 0,222 | 56900 | 0,0205 | 0,48 | 8,4 |
| 2 | 1030 | 3,0 | 5 | 0.25×0.25 | 4,6 | 0,25 | 73700 | 0,0195 | 0,4 | 8,1 |
| 3 | 2130 | 2,7 | 6 | 0.4 × 0.25 | 5,92 | 0,308 | 116900 | 0,0180 | 0,48 | 13,4 |
| 4 | 3480 | 14,8 | 7 | 0.4 × 0.4 | 6,04 | 0,40 | 154900 | 0,0172 | 1,44 | 45,5 |
| 5 | 6830 | 1,2 | 8 | 0.5 × 0.5 | 7,6 | 0,50 | 234000 | 0,0159 | 0,2 | 8,3 |
| 6 | 10420 | 6,4 | 10 | 0.6 × 0.5 | 9,65 | 0,545 | 337000 | 0,0151 | 0,64 | 45,7 |
| 6a | 10420 | 0,8 | Yu. | Ø0.64 | 8,99 | 0,64 | 369000 | 0,0149 | 0 | 0,9 |
| 7 | 10420 | 3,2 | 5 | 0.53 × 1.06 | 5,15 | 0,707 | 234000 | 0.0312×n | 2,5 | 44,2 |
| Total losses: 185 | ||||||||||
| Table 1. Aerodynamic calculation | ||||||||||
The air ducts are made of galvanized sheet steel, the thickness and size of which correspond to approx. N from . The material of the air intake shaft is brick. Adjustable grilles of the PP type with possible sections: 100 x 200; 200 x 200; 400 x 200 and 600 x 200 mm, shading coefficient 0.8 and maximum air outlet speed up to 3 m/s.
The resistance of the insulated intake valve with fully open blades is 10 Pa. Hydraulic resistance heating unit 100 Pa (according to separate calculation). Filter resistance G-4 250 Pa. Hydraulic resistance of the muffler 36 Pa (according to acoustic calculation). Air ducts are designed based on architectural requirements rectangular section.
The cross-sections of brick channels are taken according to table. 22.7.
Section 1. PP grid at the outlet with a cross section of 200×400 mm (calculated separately):
| No. of plots | Type of local resistance | Sketch | Angle α, deg. | Attitude | Rationale | KMS | ||
| F 0 /F 1 | L 0 /L st | f pass /f stv | ||||||
| 1 | Diffuser |
 |
20 | 0,62 | — | — | Table 25.1 | 0,09 |
| Retraction |
 |
90 | — | — | — | Table 25.11 | 0,19 | |
| Tee-pass |
 |
— | — | 0,3 | 0,8 | Adj. 25.8 | 0,2 | |
| ∑ = | 0,48 | |||||||
| 2 | Tee-pass |
 |
— | — | 0,48 | 0,63 | Adj. 25.8 | 0,4 |
| 3 | Branch tee |
 |
— | 0,63 | 0,61 | — | Adj. 25.9 | 0,48 |
| 4 | 2 bends | 250×400 | 90 | — | — | — | Adj. 25.11 | |
| Retraction | 400×250 | 90 | — | — | — | Adj. 25.11 | 0,22 | |
| Tee-pass |
 |
— | — | 0,49 | 0,64 | Table 25.8 | 0,4 | |
| ∑ = | 1,44 | |||||||
| 5 | Tee-pass |
 |
— | — | 0,34 | 0,83 | Adj. 25.8 | 0,2 |
| 6 | Diffuser after fan |
 |
h=0.6 | 1,53 | — | — | Adj. 25.13 | 0,14 |
| Retraction | 600×500 | 90 | — | — | — | Adj. 25.11 | 0,5 | |
| ∑= | 0,64 | |||||||
| 6a | Confusion in front of the fan |
 |
D g =0.42 m | Table 25.12 | 0 | |||
| 7 | Knee | 90 | — | — | — | Table 25.1 | 1,2 | |
| Louvre grille | Table 25.1 | 1,3 | ||||||
| ∑ = | 1,44 | |||||||
| Table 2. Determination of local resistances | ||||||||
Krasnov Yu.S.,
„Ventilation and air conditioning systems. Design recommendations for industrial and public buildings”, chapter 15. “Thermocool”
Such losses are proportional to the dynamic pressure pd = ρv2/2, where ρ is the air density, equal to approximately 1.2 kg/m3 at a temperature of about +20 °C, and v is its speed [m/s], usually behind resistance. Proportionality coefficients ζ, called local resistance coefficients (KMC), for various elements systems B and HF are usually determined from tables available, in particular, in a number of other sources.
The greatest difficulty in this case is most often the search for KMS for tees or branch assemblies, since in this case it is necessary to take into account the type of tee (for passage or for branch) and the mode of air movement (discharge or suction), as well as the ratio of air flow in the branch to flow rate in the barrel Lo ʹ = Lo/Lc and cross-sectional area of the passage to the cross-sectional area of the barrel fn ʹ = fn/fc.
For tees during suction, it is also necessary to take into account the ratio of the cross-sectional area of the branch to the cross-sectional area of the trunk fo ʹ = fo/fc. In the manual, the relevant data is given in table. 22.36-22.40. However, at high relative flow rates in the branch, the RMCs change very sharply, therefore, in this area, the tables under consideration are manually interpolated with difficulty and with a significant error.
In addition, in the case of using MS Excel spreadsheets, it is again desirable to have formulas for directly calculating the CMR through the ratio of flow rates and sections. Moreover, such formulas should, on the one hand, be quite simple and convenient for mass design and use in the educational process, but, at the same time, should not give an error exceeding the usual accuracy of engineering calculations.
Previously, a similar problem was solved by the author in relation to resistances encountered in water heating systems. Let us now consider this issue for mechanical systems B and HF. Below are the results of data approximation for unified tees (branch nodes) per passage. General form dependencies were chosen based on physical considerations, taking into account the convenience of using the resulting expressions while ensuring permissible deviation from tabular data:
It is easy to see that the relative area of the passage fn ʹ during discharge or, respectively, the branch fo ʹ during suction affects the CMS in the same way, namely, with an increase in fn ʹ or fo ʹ the resistance will decrease, and numerical coefficient with the specified parameters in all the given formulas is the same, namely (-0.25). In addition, for both supply and exhaust tees, when the air flow rate in the branch changes, the relative minimum KMS occurs at the same level Lo ʹ = 0.2.
These circumstances indicate that the obtained expressions, despite their simplicity, sufficiently reflect the general physical laws underlying the influence of the studied parameters on pressure losses in tees of any type. In particular, the larger fn ʹ or fo ʹ, i.e. the closer they are to unity, the less the flow structure changes when passing resistance, and therefore the less the CMR.
For the value Lo ʹ the dependence is more complex, but here too it will be common to both modes of air movement. An idea of the degree of correspondence between the found relationships and the initial CMR values is given in Fig. 1, which shows the results of processing Table 22.37 for KMS standardized tees (branch assemblies) for the passage of round and rectangular cross-sections during injection. Approximately the same picture is obtained for the approximation of the table. 22.38 using formula (3).
Note that, although in the latter case we're talking about O round section, it is easy to see that expression (3) quite well describes the data in table. 22.39, already related to rectangular nodes. The error of formulas for CMS is generally 5-10% (maximum up to 15%). Slightly higher deviations may be given by expression (3) for tees during suction, but even here this can be considered satisfactory, taking into account the complexity of changing the resistance in such elements.
In any case, the nature of the dependence of the IMR on the factors influencing it is reflected very well here. In this case, the obtained relationships do not require any other initial data other than those already available in the aerodynamic calculation table. In fact, it must explicitly indicate both the air flow rates and the cross sections in the current and adjacent sections included in the listed formulas. This especially simplifies calculations when using MS Excel spreadsheets.
At the same time, the formulas given in this work are very simple, clear and easily accessible for engineering calculations, especially in MS Excel, as well as in the educational process. Their use makes it possible to abandon the interpolation of tables while maintaining the accuracy required for engineering calculations, and to directly calculate the CMC of tees per passage for a wide variety of cross-sectional ratios and air flow rates in the trunk and branches.
This is quite enough for the design of V and HF systems in most residential and public buildings.
Sports disciplines - Chess, chess - team competitions, blitz, rapid chess:
Sports discipline - Chess composition:
Sports discipline - Correspondence chess:
CMS is performed from 9 years of age
| KMS | ||
| M | AND | |
| 1901-1925 | 1801-1825 | 75 |
| 1926-1950 | 1826-1850 | 70 |
| 1951-1975 | 1851-1875 | 65 |
| 1976-2000 | 1876-1900 | 60 |
| 2001-2025 | 1901-1925 | 55 |
| 2026-2050 | 1926-1950 | 50 |
| 2051-2075 | 1951-1975 | 45 |
| 2076-2100 | 1976-2000 | 40 |
| > 2100 | > 2000 | 35 |
| Sports categories | |||||
| I | II | III | |||
| Condition for fulfilling the norm: average Russian rating of opponents | Norm: % of points scored to the number of maximum possible points in actually played games | Condition for fulfilling the norm: average Russian rating of opponents | Norm: % of points scored to the number of maximum possible points in actually played games | Condition for fulfilling the norm: average Russian rating of opponents | Norm: % of points scored to the number of maximum possible points in actually played games |
| 1701-1725 | 75 | 1501-1525 | 75 | 1301-1325 | 75 |
| 1726-1750 | 70 | 1526-1550 | 70 | 1326-1350 | 70 |
| 1751-1775 | 65 | 1551-1575 | 65 | 1351-1375 | 65 |
| 1776-1800 | 60 | 1576-1600 | 60 | 1376-1400 | 60 |
| 1801-1825 | 55 | 1601-1625 | 55 | 1401-1425 | 55 |
| 1826-1850 | 50 | 1626-1650 | 50 | 1426-1450 | 50 |
| 1851-1875 | 45 | 1651-1675 | 45 | 1451-1475 | 45 |
| 1876-1900 | 40 | 1676-1700 | 40 | 1476-1500 | 40 |
| > 1900 | 35 | > 1700 | 35 | > 1500 | 35 |
| Sports categories (women's) | |||||
| I | II | III | |||
| Condition for fulfilling the norm: average Russian rating of opponents | Norm: % of points scored to the number of maximum possible points in actually played games | Condition for fulfilling the norm: average Russian rating of opponents | Norm: % of points scored to the number of maximum possible points in actually played games | Condition for fulfilling the norm: average Russian rating of opponents | Norm: % of points scored to the number of maximum possible points in actually played games |
| 1601-1625 | 75 | 1401-1425 | 75 | 1201-1225 | 75 |
| 1626-1650 | 70 | 1426-1450 | 70 | 1226-1250 | 70 |
| 1651-1675 | 65 | 1451-1475 | 65 | 1251-1275 | 65 |
| 1676-1700 | 60 | 1476-1500 | 60 | 1276-1300 | 60 |
| 1701-1725 | 55 | 1501-1525 | 55 | 1301-1325 | 55 |
| 1726-1750 | 50 | 1526-1550 | 50 | 1326-1350 | 50 |
| 1751-1775 | 45 | 1551-1575 | 45 | 1351-1375 | 45 |
| 1776-1800 | 40 | 1576-1600 | 40 | 1376-1400 | 40 |
| > 1800 | 35 | > 1600 | 35 | > 1400 | 35 |
| Youth sports categories | |||||
| I | II | III | |||
| Condition for fulfilling the norm: average Russian rating of opponents | Norm: % of points scored to the number of maximum possible points in actually played games | Condition for fulfilling the norm: average Russian rating of opponents | Norm: % of points scored to the number of maximum possible points in actually played games | Condition for fulfilling the norm: average Russian rating of opponents | Norm: % of points scored to the number of maximum possible points in actually played games |
| 1151-1156 | 75 | 1101-1106 | 75 | ||
| 1157-1162 | 70 | 1107-1112 | 70 | ||
| 1163-1168 | 65 | 1113-1118 | 65 | ||
| 1169-1174 | 60 | 1119-1124 | 60 | 1000 | 60 |
| 1175-1180 | 55 | 1125-1130 | 55 | 1001-1025 | 55 |
| 1181-1185 | 50 | 1131-1135 | 50 | 1026-1050 | 50 |
| 1186-1190 | 45 | 1136-1140 | 45 | 1051-1075 | 45 |
| 1191-1200 | 40 | 1141-1150 | 40 | 1076-1100 | 40 |
| >1200 | 35 | >1150 | 35 | >1100 | 35 |
3. To fulfill the norm of sports categories in a sports competition, physical education event, the athlete must actually play >= 7 games in sports disciplines"chess" or "chess - team competition".
4. To fulfill the norm of sports categories in a sports competition, physical education event, the athlete must actually play >= 9 games in the sports discipline “quick chess”.
5. To fulfill the norm of sports categories in a sports competition or physical education event, the athlete must actually play >= 11 games in the sports discipline “blitz”.
6. In the sports discipline "rapid chess" time control is applied: 15 minutes until the end of the game with an addition of 10 seconds for each move made, starting from the 1st, for each athlete or 10 minutes until the end of the game with an addition of 5 seconds for each move made, starting from the 1st, for each athlete.
7. In the sports discipline “blitz”, time control is applied: 3 minutes before the end of the game with the addition of 2 seconds for each move made, starting from the 1st, for each athlete.
8. Russian championships, all-Russian sports competitions included in the EKP, among persons with an upper age limit, championship of the federal district, two or more federal districts, championship of Moscow, St. Petersburg, championship of the subject Russian Federation, other official sports competitions of a constituent entity of the Russian Federation among persons with an upper age limit, other physical education events of a constituent entity of the Russian Federation among persons with an upper age limit, municipal championships, intermunicipal official sports competitions among persons with an upper age limit, physical education events of a municipal entity among persons with an upper age limit, other official sports competitions of the municipality among persons with an upper age limit, other physical education events among persons with an upper age limit are held in the following age groups: juniors, juniors (up to 21 years); boys, girls (under 19 years old); boys, girls (up to 17 years old); boys, girls (up to 15 years); boys, girls (up to 13 years old); boys, girls (up to 11 years old); boys, girls (up to 9 years old).
9. World Universiade, World Championship among students, All-Russian Universiade, All-Russian sports competitions among students, included in the EKP, are held in the age group: juniors, junior women (17-25 years old).
10. To determine the average Russian rating of opponents in a sports competition or physical education event, it is necessary to summarize the Russian ratings of the athlete’s opponents in a sports competition or physical education event. The amount thus obtained is divided by the number of the athlete’s opponents in a sports competition or physical education event.
11. In a sports competition or physical education event, participants who do not have a Russian rating are counted as having a Russian rating of 1000.
12. Definition of norm:
12.1. In the column “Condition for fulfilling the norm: average Russian rating of opponents” we find a line with a number corresponding to the average Russian rating opponents of a held sports competition, physical education event, respectively, among men or women, the number located at the intersection of the specified line and the column “Norm: % of points scored to the number of maximum possible points in the games actually played” corresponds to the percentage of points scored from the maximum number of points that it was possible to score in the actual games played in a sports competition or physical education event.
12.2. Norm: % of points scored to the number of maximum possible points in actually played games, expressed in the number of points, calculated by the formula: A = (BxC)/100, where:
A - number of points,
B - the number specified in clause 12.1 of these other conditions corresponds to the percentage of points scored from the maximum number of points that could be scored in the games actually played,
C is the number of maximum possible points in the actual games played in the sporting competition.
12.3. If the norm of a sports category in a sports competition or physical education event is expressed as a fractional number, then it is rounded to the nearest half point.
13. Sports categories are assigned in the sports disciplines “chess”, “chess - team competitions”, “rapid chess” and “blitz” based on the results of official sports competitions, physical education events: CMS - not lower than the status of an official sports competition, physical education event of a municipality; I-III sports categories and I-III youth sports categories - at official sports competitions, physical education events of any status.
14. CMS in the sports disciplines “chess” and “chess - team competitions” is awarded for first place taken in official sports competitions with a status not lower than the championship of federal districts, two or more federal districts, the championship of Moscow, St. Petersburg in the following age groups: juniors, juniors (under 21 years old); boys, girls (under 19 years old); boys, girls (up to 17 years old); boys, girls (under 15 years old).
15. In the sports disciplines “rapid chess” and “blitz” in age categories: boys, girls (up to 13 years); boys, girls (up to 11 years old); boys, girls (under 9 years old) sports categories are not assigned.
16. I-III youth sports categories in the sports disciplines “chess” and “chess - team competitions” are assigned up to 15 years of age.
17. To participate in sports competitions, an athlete must reach the established age in the calendar year of the sports competition.
You can also use the approximate formula:
0.195 v 1.8
R f . (10) d 100 1 , 2
Its error does not exceed 3–5%, which is sufficient for engineering calculations.
The total pressure loss due to friction for the entire section is obtained by multiplying the specific losses R by the length of the section l, Rl, Pa. If air ducts or channels made of other materials are used, it is necessary to introduce a correction for roughness βsh according to table. 2. It depends on the absolute equivalent roughness of the air duct material K e (Table 3) and the value v f .
table 2 |
|||||
Correction values βsh |
|||||
v f , m/s |
βsh at values of K e, mm |
||||
Table 3 Absolute equivalent roughness of air duct material
Plasterer- |
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on the grid |
||||||
K e, mm |
For steel air ducts βш = 1. More detailed valuesβsh can be found in table. 22.12. Taking into account this amendment, the updated friction pressure loss Rl βsh, Pa, is obtained by multiplying Rl by the value βsh. Then the dynamic pressure on the participants is determined
under standard conditions ρw = 1.2 kg/m3.
Next, local resistances are identified in the area, local resistance coefficients (LRC) ξ are determined, and the sum of the IMR in this area (Σξ) is calculated. All local resistances are recorded in the following form.
SHEET KMS VENTILATION SYSTEMS
Etc.
IN in the “local resistance” column, write down the names of the resistances (bend, tee, cross, elbow, grille, air distributor, umbrella, etc.) available in this area. In addition, their quantity and characteristics are noted, by which the CMR values are determined for these elements. For example, for a round outlet this is the angle of rotation and the ratio of the radius of rotation to the diameter of the duct r /d, for a rectangular outlet - the angle of rotation and dimensions of the sides of the air duct a and b. For side openings in an air duct or channel (for example, at the location where an air intake grille is installed) - the ratio of the area of the opening to the cross-section of the air duct
f otv / f o . For tees and crosses on the passage, the ratio of the cross-sectional area of the passage and the trunk f p /f s and the flow rate in the branch and in the trunk L o /L s is taken into account, for tees and crosses on the branch - the ratio of the cross-sectional area of the branch and the trunk f p /f s and again the value of L o / L c . It should be borne in mind that each tee or cross connects two adjacent sections, but they relate to the one of these sections with less air flow L. The difference between tees and crosses on a pass and on a branch has to do with how the design direction runs. This is shown in Fig. 11. Here the calculated direction is depicted by a thick line, and the directions of air flows are depicted by thin arrows. In addition, it is signed where exactly in each option the barrel, passage and opening are located.
tee branching for the right choice relations fп/fс, fo/fс and Lо/Lс. Note that in supply ventilation systems the calculation is usually carried out against the air movement, and in exhaust ventilation systems - along this movement. The areas to which the tees in question belong are indicated with check marks. The same applies to crosses. As a rule, although not always, tees and crosses on the passage appear when calculating the main direction, and on the branch they appear when aerodynamically linking secondary sections (see below). In this case, the same tee in the main direction can be taken into account as a tee for passage, and in the secondary direction
– as a branch with a different coefficient. KMS for crosses
accepted in the same size as for the corresponding tees.
Rice. 11. Tee calculation diagram
Approximate values of ξ for commonly encountered resistances are given in Table. 4.
Table 4 |
||||
Values ξ of some local resistances |
||||
Name |
Name |
|||
resistance |
resistance |
|||
Round bend 90o, |
The grille is not adjustable |
|||
r/d = 1 |
May RS-G (exhaust or |
|||
Rectangular bend 90° |
air intake) |
|||
Tee on the passage (on- |
Sudden expansion |
|||
oppression) |
||||
Tee on branch |
Sudden contraction |
|||
Tee on the passage (all- |
The first side hole |
|||
sity (entrance into air intake |
||||
Tee on branch |
–0.5* … |
boron mine) |
||
Lamp lamp (anemostat) ST-KR, |
Rectangular elbow |
|||
90o |
||||
Adjustable grille RS- |
Umbrella over the exhaust |
|||
VG (supply) |
||||
*) negative CMR can occur at low Lo/Lс due to the ejection (suction) of air from the branch by the main flow.
More detailed data for KMS are shown in table. 22.16 – 22.43. For the most common local resistances -
tees in the passage - KMS can also be approximately calculated using the following formulas:
0.41 f "25 L" 0.2 4 |
0.25 at |
0.7 and |
f "0.5 (11) |
|||||||
– for tees during discharge (supply); |
||||||||||
at L" |
0.4 you can use a simplified formula |
|||||||||
prox pr 0. 425 0. 25 f p "; |
||||||||||
0.2 1.7 f" |
0.35 0.25f" |
2.4L" |
0. 2 2 |
|||||||
– for suction (exhaust) tees.
Here L" |
f o |
and f" |
f p |
|||||||
f with |
||||||||||
After determining the value of Σξ, calculate the pressure loss at local resistances Z P d , Pa, and the total pressure loss
leniya in the area Rl βш + Z, Pa.
The calculation results are entered into a table in the following form.
AERODYNAMIC CALCULATION OF THE VENTILATION SYSTEM
Calculated |
|||||||||||||||
Duct dimensions |
pressure |
||||||||||||||
for friction |
Rlβ w |
Rd, |
|||||||||||||
βsh |
|||||||||||||||
d or |
f op, |
ff, |
Vf, |
d eq |
|||||||||||
l, m |
a×b, |
||||||||||||||
When the calculation of all sections of the main direction is completed, the values of Rl βш + Z for them are summed up and the total resistance is determined.
ventilation network P network = Σ(Rl βш + Z ).
After calculating the main direction, one or two branches are linked. If the system serves several floors, you can select floor branches on intermediate floors for linking. If the system serves one floor, branches from the main line that are not included in the main direction are linked (see example in paragraph 4.3). The calculation of the linked sections is carried out in the same sequence as for the main direction, and is recorded in the table in the same form. The linking is considered completed if the amount
pressure loss Σ(Rl βш + Z) along the linked sections deviates from the sum Σ(Rl βш + Z) along the parallel connected sections of the main direction by no more than 10%. Parallel connected sections are considered to be sections along the main and linked directions from the point of their branching to the end air distributors. If the circuit looks like shown in Fig. 12 (the main direction is highlighted with a thick line), then linking direction 2 requires that the value of Rl βш + Z for section 2 be equal to Rl βш + Z for section 1, obtained from the calculation of the main direction, with an accuracy of 10%. Linking is achieved by selecting the diameters of round or section sizes of rectangular air ducts in the linked areas, and if this is not possible, by installing throttle valves or diaphragms on the branches.
Fan selection should be made according to the manufacturer’s catalogs or data. The fan pressure is equal to the sum of pressure losses in the ventilation network in the main direction, determined during the aerodynamic calculation of the ventilation system, and the sum of pressure losses in the elements of the ventilation unit ( air valve, filter, air heater, silencer, etc.).
Rice. 12. Fragment of the ventilation system diagram with the choice of branch for linking
It is possible to finally select a fan only after an acoustic calculation, when the issue of installing a noise suppressor has been decided. An acoustic calculation can only be performed after preliminary selection of a fan, since the initial data for it are the levels of sound power emitted by the fan into the air ducts. Acoustic calculations are performed following the instructions in Chapter 12. If necessary, calculate and determine the standard size of the silencer, then finally select the fan.
4.3. An example of calculating a supply ventilation system
Under consideration supply system ventilation for the dining room. The drawing of air ducts and air distributors on the plan is given in paragraph 3.1 in the first version ( typical diagram for halls).
System diagram
1000x400 5 8310 m3/h
2772 m3/h2 |
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More details about the calculation methodology and the necessary initial data can be found at. The corresponding terminology is given in.
SHEET KMS SYSTEM P1
Local resistance |
||||||
924 m3/h |
||||||
1. Round bend 90o r /d =1 |
||||||
2. Tee on the passage (discharge) |
||||||
fп/fc |
Lo/Lc |
|||||
fп/fc |
Lo/Lc |
|||||
1. Tee on the passage (discharge) |
||||||
fп/fc |
Lo/Lc |
|||||
1. Tee on the passage (discharge) |
||||||
fп/fc |
Lo/Lc |
|||||
1. Rectangular bend 1000×400 90o 4 pcs. |
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1. Air intake shaft with umbrella |
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(first side hole) |
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1. Louvered air intake grille |
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SHEET OF KMS SYSTEM P1 (BRANCH No. 1) |
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Local resistance |
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1. Air distributor PRM3 at flow rate |
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924 m3/h |
||||||
1. Round bend 90o r /d =1 |
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2. Branch tee (discharge) |
||||||
fo/fc |
Lo/Lc |
|||||
APPENDIX Characteristics ventilation grilles and lampshades
I. Clear cross-sections, m2, of supply and exhaust louver grilles RS-VG and RS-G
Length, mm |
Height, mm |
|||||
Speed coefficient m = 6.3, temperature coefficient n = 5.1.
II. Characteristics of lampshades ST-KR and ST-KV
Name |
Dimensions, mm |
f fact, m 2 |
||
Dimensional |
Interior |
|||
Lamp ST-KR |
||||
(round) |
||||
Lamp ST-KV |
||||
(square) |
||||
Speed coefficient m = 2.5, temperature coefficient n = 3.
BIBLIOGRAPHICAL LIST
1. Samarin O.D. Selection of air supply equipment ventilation units(air conditioners) type KTsKP. Guidelines for completing coursework and diploma projects for students of specialty 270109 “Heat and gas supply and ventilation.” – M.: MGSU, 2009. – 32 p.
2. Belova E.M. Central systems air conditioning in buildings. – M.: Euroclimate, 2006. – 640 p.
3. SNiP 41-01-2003 “Heating, ventilation and air conditioning”. – M.: State Unitary Enterprise TsPP, 2004.
4. Catalog of Arktos equipment.
5. sanitary facilities. Part 3. Ventilation and air conditioning. Book 2. / Ed. N.N. Pavlov and Yu.I. Schiller. – M.: Stroyizdat, 1992. – 416 p.
6. GOST 21.602-2003. System project documentation for construction. Execution Rules working documentation heating, ventilation and air conditioning. – M.: State Unitary Enterprise TsPP, 2004.
7. Samarin O.D. About the mode of air movement in steel air ducts.
// SOK, 2006, No. 7, p. 90 – 91.
8. Designer's Handbook. Domestic sanitary facilities. Part 3. Ventilation and air conditioning. Book 1. / Ed. N.N. Pavlov and Yu.I. Schiller. – M.: Stroyizdat, 1992. – 320 p.
9. Kamenev P.N., Tertichnik E.I. Ventilation. – M.: ASV, 2006. – 616 p.
10. Krupnov B.A. Terminology for building thermal physics, heating, ventilation and air conditioning: guidelines for students of the specialty "Heat and Gas Supply and Ventilation".
SVENT 6 .0
Aerodynamic software package
calculation of supply and exhaust ventilation systems.
[User's GuideSVENT]
Note. The instructions are somewhat behind in describing new features. Editing is in progress. The current version will be posted on the website. Not all planned opportunities have been implemented. Contact us for updates. If something doesn’t work out, call the authors (tel. at the end of the text).
"C N I I E P engineering equipment"offers to your attention
Aerodynamic calculation of ventilation systems - "SVENT" for Windows.
The "SVENT" program is designed to solve problems:
Two types of calculation:
The air duct database contains standard rectangular and round air ducts; non-standard ones are assigned by the designer himself. The air duct database is open for modification/addition.
In the database nodes(inputs/outputs, confusers, diffusers, bends, tees, throttling devices) calculation methods are laid down KMS(local resistance coefficients) from the following sources:
Designer's Handbook. Ventilation and air conditioning. Staroverov, Moscow, 1969 Reference data for design. Heating and ventilation. Coefficients of local resistance (source: TsAGI Directory, 1950). Promstroyproekt, Moscow, 1959 Ventilation and air conditioning systems. Recommendations for design, testing and commissioning. , TERMOKUL, Moscow, 2004 VSN 353-86 Design and application of air ducts from standardized parts. Catalogs Arctic and IMP Klima.
The node database is open for modification/addition.
Any system consists of a suction and/or discharge part. The number of plots is not limited.
There are no crosses, however, they can be imagined as two tees.
Special note on KMS:
Let's consider the principle of forming the name of the node selection button.
(When replenishing the node database, it is recommended (but not required) to use the following node numbering scheme: the first digit of the three-digit number reflects the source for the methodology: 0 - test and user nodes, 1 - Staroverov, 2 - Idelchik, 3 - Krasnov, the remaining numbers are free for others techniques)
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Node category |
Abbreviation |
Range of possible conditional numbers |
Default number | |
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Inputs and outputs | ||||
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Bends WITHOUT changing the section | ||||
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Bends With a change in cross-section | ||||
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Confusers and diffusers | ||||
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Gates, chokes, diaphragms | ||||
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Through tees | ||||
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T-pieces |
(Note: almost any tee has a KMS method for working on suction and discharge and, therefore, is designated by the same number when used on the suction or discharge part; and the inlet (suction) does not always have (usually does not have) an analogue output (discharge), for example, a free outlet from a pipe with an outlet, a shower pipe, etc.)
Many methods require entering additional parameters (for example, grid size, confuser length, number of throttle valves, etc.); for them, the base includes the calculation of default values such that the CMR is calculated at the current flow rate and cross-section (this is required for automatic enumeration sections). The default options are marked with check marks. To enter your value, you need to uncheck the box. At the end of the automatic calculation, you need to check whether these parameters satisfy you.
Let's introduce the concept prefabricated section: any number of series-connected air ducts with the same cross-section and flow rate. A straight duct of any length is called integral part collection area. When constructing an axonometric diagram, sections are numbered automatically, choosing the smallest available number. In the picture, the current one is prefabricated section No. 1 component No. 1 - designated No. 1.1 (at this component section No. 1 ends, then it branches into sections No. 2 and No. 3). Star
with a number means that the section following No. 10 will have a different number and may have a different flow rate and cross-section.
Key space- mark/remove the end of the section, you can build a confuser/diffuser, a tee.
When you press the space key multiple times in the parametric window header, an asterisk is placed and removed (if there is no branch), indicating the end of the section. It can be used at any time - both on the last section (then the next section will be built with a different number), and in the middle of the section - then at this place the section will either be divided into two or merged into one (with automatic renumbering).
designation in the text: LB/RB - left/right mouse button
Ctrl+LB– if the mouse cursor is in the graphics window, the area caught in the crosshairs becomes dotted or the selection is deselected.
Ctrl+Shift+LB- part of the diagram from the area caught in the sight and away from the fan becomes dotted or the selection is removed.
Alt+Shift+LB- part of the diagram from the area caught in the sight and away from the fan becomes highlighted with a dotted line.
Shift+mouse movement- moving the diagram
Mouse selection in the graphics window – change the current area to the one that is in the mouse sight.
Alt+Mouse selection in the graphics window – set the length and cross-section of the current section to be the same as that of the one that hit the mouse sight.
Mouse wheel changing the scale of the diagram (as in AutoCAD)
Middle mouse button hold the button pressed and move the diagram (as in AutoCAD)
Ctrl+G transition to a section with a given number (the number is set at the top of the window)
Ctrl+D make the current area round
Ctrl+F make the current area rectangular
Ctrl+N insert a new section before the current one
Operations with branches
After this, you can, for example, set another section as current (highlighted in green in the second figure), divide this section with the "space" key (an asterisk will appear (see above)), since in this place the flow rate and/or cross-section will change and select item Menu – Branch – attach from the buffer to the current section. The resulting diagram is shown in the second figure. A branch can be added according to the same rules as when adding one section. The sections are numbered automatically.
For a branch, you can change the section profile (from round to rectangular or vice versa) Menu – Branch – make areas round/rectangular or delete the branch (including the currently selected section). It is recommended that after these operations you check that the section without branches does not have a separation of numbers (branches with a change in section). Combine areas if necessary, because the node BRANCH WITH CHANGE OF SECTION allows you to calculate kms for a very limited set of sections and only for a rectangular profile. Leave the knot O251, if only you really needed in this place there is a branch with an expanded or narrowed outlet cross-section.
– Branch – make similar nodes the same: using this function you can assign a newly installed node (“in the node selection window” with the “apply” button) to the entire branch from the current section.
1. File menu – new system.
2. Menu System - Discharge part (or suction)
3. Menu Area – Round (or rectangular)
4. 
Section menu – add a new one (in the parametric window there is a green frame with the heading “add” and six buttons (with blue arrows), by clicking on which you can add components of a given length and direction (the arrow shows the direction from the fan)
5. 
The length can be changed at any time using the L[m] field – the length of the current component.
6. 
An erroneously specified direction can be changed: Section menu – change direction. The direction buttons (blue arrows) are logically found with other options in a common gray frame and are used to change the direction of the current component. With any change in the current direction, for example, the following changes can occur - the through tee has changed to a T-shaped one, the elbow has changed to a choke, or the node is simply unacceptable, for example, three sections do NOT lie in the same plane. All this is checked automatically when you click the “confirm changes” button. If everything is correct, then this button disappears when clicked. When the erroneous directions are corrected – Menu – section – add a new one. Continue building the diagram, specifying the lengths of the sections.
7. If you want to continue the section with another profile (round after rectangular or vice versa), mark the end of the section (space) - an asterisk should appear next to the number - add a section in the same direction, the red button in the parametric window will be called K/D - change this node at No. 000 in the node selection window - this is the exit from a larger section to a smaller one and vice versa; Method No. 000 does not impose any requirements on the air duct profile.
8. If you need to build a tee, mark the end of the section, attach any of the branches (you can continue building the diagram further along the selected branch), select the section that should branch and attach the second branch.
9. Air flow must be indicated only at the end sections (ending at the entrance or exit)
10. At any time, set the methods for determining the CMC by selecting a specific number for bends, tees, inputs/outputs, confusers/diffusers, chokes, etc. You can leave the ones suggested by default.
11. During the construction process, a diagram is displayed in the graphics window, automatically scaling and moving enough to show the entire newly added section and everything that was visible before its addition.
12.If you set the auto mode to “shift” (at the top of the graphics window), then the diagram will only move, displaying the added area and not change the scale. You can display the entire circuit by clicking the "Entire Circuit" button at the top of the graphics window.
13.During the construction process, red or purple areas may suddenly appear in the graphics window. This means that these highlighted areas have crossed or moved closer together, respectively.
14.Menu – System – Calculation – without linking- makes calculations, without changing anything in the diagram.
15.
Menu – System – Calculation – With linking– performs calculations with the selection of suitable sections that satisfy the given speeds with an attempt to reduce the discrepancy between parallel branches; always displays an input window permissible speeds(upper and lower limits for end areas and near fan). If the calculation is successful, sections will be placed throughout the entire scheme that satisfy the given velocities and for any section there will be specific numbers of total losses Hp, losses on a given component H, its components RL and Z [kg/m2], flow rate [m3/hour] , speed [m/s] and KMR on the current component and adjacent to it on the side farthest from the fan. If the status line displays the message “no options,” it means that not a single section option was found that would allow it to fit the specified speeds in all sections and determine the CMR using the selected methods for all nodes. In this case, you can use any of the methods (or a combination of them):
a. vary speed ranges;
b. change the methods for determining KMS for tees that produce the value KMS=NaN;
c. change expenses;
d. change the configuration of the circuit, focusing on the rule that in a tee the flow direction should correspond to a higher flow rate;
For example, for the situation in the figure, you can analyze how to adjust the flow rates or cross sections (you can reduce Lo - flow rate for branch No. 3, then the Lo/Lc ratio will decrease) so that the kms is calculated.
Before the calculation, the cross-section of the fan pipe is automatically set as smaller according to the specified minimum and maximum speeds; after the calculation, you can change this value to the nearest standard one.
Some added features that are under change:
16.If you are satisfied with all the results, you can generate a report in htm format (will open in a window Internet Explorer or another browser): Menu – system – report, which can be edited if necessary in a text editor (for example, MS Word). The report will look like this (the areas that form the path of maximum losses are highlighted in bold).
17.There is still an opportunity to get Menu – system – summary report for several systems. The total specification for air ducts and fittings for several systems will be calculated (the report will not include information about losses by area); the report will open in the browser; An 11-graph specification template will also open (if the free Open Office application is installed) and be filled in with summary data for the selected systems.
18.The created specification can be edited in Open Office.
Calculation results.
Ventilation system report: (file C:\last\v3.dat)
Total losses (suction part) 10.1 kg/m2
Losses by area:
|
Q, m3/h |
BxH/D, mm |
V, m/s |
Rl, kg/m2 |
Z, kg/m2 |
Ptotal, kg/m2 |
Radd, kg/m2 |
||
|
branches into 3 and 2 with a residual of 57%, |P3-P2|= 0.7 |
||||||||
Specification of collecting devices (for the suction part of the system):
Air duct specification:
Specification of fittings (bends, tees, throttling devices):
Decryption according to the database:
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TERMOKUL, Moscow, 2004 |
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TERMOKUL, Moscow, 2004 |
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Stroyizdat, Moscow, 1969 |
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Stroyizdat, Moscow, 1969 |
Calculation scheme in AutoCAD
19.
Menu - System – ExportDXF– generate dxf. If you plan to finalize the drawing in the AutoCad system, use the following paragraph (Axonometry SCR/LSP AutoCad). Before using this item, you need to adjust the scale (a field with a number at the top of the graphics window), for example, if it is 50, then the scale in the AutoCAD file will be 1:50. One unit of AutoCad drawing at any scale will be equal to 1mm (a 5m duct will be depicted with a line of 5000 drawing units), however, the line breaks will be such that on paper they will be 5mm, and scalable blocks and labels will correspond to the selected scale (the text when printed will have height 2.5mm).
20. Menu - System – AxonometrySCR/ LSP AutoCad– generate a file for the AutoCad system. Before using this item, you must adjust the scale (see previous item). A file with the extension scr will be generated. Remember the location of this file. It must be called from AutoCAD (menu item tools - run script (tools – run script)).
If the diagram is not drawn, it means
you have already run the script on this sheet, then either type (sv-build) or start a new drawing and run the script
The following message will appear (see picture)
If a new drawing is started, the blank will be drawn automatically; if the script is called again on this drawing, then to start drawing the blank, type in the command line:
(sv- build)
(right with brackets)!
Then you can sign with the command (svs) (also with brackets)!
(also typed with brackets). To install a signature, select the required air duct (immediately select in the middle, at the edge, or where it is convenient for the leader). A shelf will appear with the inscriptions of the cross section and air flow. Use the "space" key to select where to attach the leader (left/right), and use the 5,6,7,8,9,0 keys to determine the width of the text (0.5,0.6,0.7,0.8,0.9,1 - respectively), move the shelf to desired free place on the drawing and click the mouse button. The shelf will be fixed and the program will wait for the next air duct. To finish, click the right mouse button. You can start the process further with the command (svs) and continue unfinished areas. The text style of captions can be customized. To do this, it is recommended to open (in AutoCAD) the file before starting work dwglib. dwg from the program folder (usually "C:\Program Files\KlimatVnutri\Svent\").
Customize the "sv-subscript" style to your liking by specifying the font. Leave the height at 0. Using the block attribute manager, you can set the text height for the attributes "ATTR1", "ATTR2", "ATTR3", "ATTR4" of the "Attrs" block. Recommended values are 2.5 or 3. Here you can also set the default width.
Calculation example.
The text will use the following program interface elements:
1. When building a network, you must strive to ensure that the passage corresponds large quantity air than the branch.
2. Start: Menu - File - New system.
3. Selection: Menu - System - Suction part.
4. Menu – Area – Add new. Highlighted in the parametric window green framed area with buttons that can be used to add sections, as well as a default length field (the new section is initially given this length value, the fractional part is separated by a comma). If there will be many sections of a certain length, it is convenient to set this value here. Set it to 1.2 (this is in meters).
5. Menu – Area – set round (or rectangular) immediately (so as not to change later throughout the entire scheme from round to rectangular). Subsequent completed sections will have the same cross-section. If somewhere a transition from round to rectangular is necessary, you need to mark the logical end of the section with the space bar (see below) and continue building in the same direction. Specify the transition with the node KnotID=160 (the exit from a larger section to a smaller one or vice versa without specification is round/rectangular). We do not have a method for calculating the Kms of the round->rectangular transition, so the most suitable of the available ones is No. 000.
6. BY– press the down arrow with the mouse, a section 1.2 m long is added.
7. BY– click the right arrow with the mouse, adjust the length by 1m.
8. BY– press the down arrow with the mouse and adjust the length to 9.4 m.
9. and and.d. arrow left-down 1.2m, right 2.2m, left-down 2.5m.
11. Next you need to create a tee. To do this, mark the logical end of the section with the space bar. IN BY An asterisk will appear next to section number 1.6, indicating that the next section may have a different cross-section and/or flow rate. Branches can be arranged in any order. BY– press the mouse left arrow, length 1.5 m, down 0.3 m. GO– select section 1.6 with the mouse (the section where you pressed the space bar). BY should display the area №1.6 * .
12. BY– press the left-down arrow 2m. The result is a tee.
Note: during the construction process, the diagram is automatically scaled and moved so that the new section is always completely visible. At the top of the graphics window there is an Auto – shift/scale switch. Autoscale is a mode in which GO after adding a section, the same part of the diagram is always visible as before adding the section. If necessary, the diagram is shifted and scaled. Autoshift is a mode in which GO The newly added section is always visible, and the scale of the diagram does not change.
13. Press "spacebar". IN BY An asterisk will appear next to the number 3.1 of the site. BY– click the left arrow (another way to set the length: GO– press Alt+mouse select the previous branch (branch to the left, we just built a tee). In this case, the length of the current section will be set to 1.5 m, the same as that of the section selected with the mouse while pressing the Alt key). Now down 0.3m. GO– select section 3.1 with the mouse (the section where you pressed the space bar). BY should display the area №3. 1 * .
14. And.d. arrow left-down 1.5m, up 0.6m, left-down 1m, right 4.4m, "space", right-up 3m, down 0.3m, GO– select section No. 5.4*(2 “pieces” back), right 4.4m, right-up 2m, “space”, right 1m, down 0.3m, select section No. piece back), right-up 1m, right 1m , down 0.3m.
15. Arrange air flow rates in m3/hour only for final areas. Walk along all the “tails” 0.3m
16. Menu - System – Calculation – With linkage. In a real system, if in the table BY there are NaN symbols - this means the calculation is not completed, most likely due to the fact that the Kms were not calculated at some nodes (usually tees) or somewhere there was an error in division by 0. See above for how to act in this case (p. 6)
17. Menu - System – System-wide report
Let us introduce the concept " Conditional distance from the fan". The conditional range can be viewed in the "filter" window by selecting any section (the conditional range - distance from the fan - is indicated in parentheses). The section immediately before the IN/OUT has a range of "1", then as you approach the fan, the range increases by one with each change in the section number. The range of speeds in which to sort through the sections is calculated based on the distance. The range of speeds for any section can be viewed in the "Restrictions on ducts" window, which opens using the "Calculation with linking" command. (Velocity values are automatically calculated for all sections before calculation with linking; to view the actual ranges before calculation, you must click the "Apply" button in the "Duct Restrictions" window. The ranges can be corrected for any section by unchecking the checkbox(es) opposite the corresponding number(s) (and clicking the "apply" button By increasing the range, you can increase the number of combinations of sections to be searched.
1. If after calculation with linking the message " No options found, see black node" - this means that the calculation has advanced as far as possible to the current section (the black node in front, which is usually a tee, since the calculation cannot be obtained only due to the impossibility of determining the kms for the tee for any combination of sections installed in compliance with the specified speed range ).
Options:
Check that the side branch corresponds to a smaller amount of air than the through branch; the reverse option cannot be calculated due to the cms. If the rule is followed throughout the system: pass not less air than to the side outlet, then see further...
The easiest: Increase the design speed range in the "Duct Restrictions" window - "system-wide" tab. - reduce the minimum and/or increase the maximum speed of the input/output and/or fan. If the areas are uniformly loaded, this method may eventually work, but each increase in the speed range increases the calculation time.
Analyze the design. If there are special areas with low flow rates, then it is not practical to expand the speed ranges throughout the entire system - you need to go to the “for part of the system” tab and try to change the ranges in these special areas. To select a group of similar sections, you can use a filter and change the speed range for the entire group at once. Then run the calculation with linking.
If all else fails. -xi+2,
For example, node No. 000, uncheck the kms calculation box, select the value “approximate”; then the left and right tolerances Fn, Fo, Q of the table exit will be used for the calculation: open the source of calculation kms - kms pass Fo/Fc has a range from 0.8 to 0.1, if you enter the right tolerance "2", then the kms calculation will be performed by extrapolation from 1 up to 0.1 (i.e. 0.8+(0.8-0.6)).
Although this is incorrect, it will be more of a disservice to the truth than if you take the value of kms from the “ceiling”.
If everything still doesn't work out, you can set user node No. 000 (all user nodes conditionally have the first digit “0”) - manually set the kms for the outlet and passage, then the calculation will not stop at this point... At the same time, do not forget that in this place the air distribution is unpredictable, provide an adjustment mechanism (gate/diaphragm/throttle).
If the calculation is completed successfully, it means that it was possible to calculate local resistance for all nodes and maintain the specified speed range in all sections. However, linking parallel branches without additional adjustment may be impossible to achieve only by sorting out the sections. In this case, you can use the AMP-K grid (node No. 000) to link the final parallel sections, and install a throttle/gate/diaphragm on a less loaded one to link the branches. After this, run “calculation and regulation”. The gate slot or throttle angle or the position of the AMP(ADR) grid flow regulator will be automatically selected for linking parallel branches.
To correctly calculate the air distribution through the grilles installed along the air duct, you must use not tees, but in/out through the side openings. To define such a node (side input/output), you need to build a tee (or a bend with a change in cross-section) as usual, and then set the length to “0” on the branch, then the tee will turn into a “side in/out”, and a bend with a change in cross-section in "side entry/exit through the last hole". In this case, in the section with length "0" it is necessary to set the material "standard size" and use grille No. 000 on the input/outputs, then the standard sizes of the grille will be selected only those that geometric dimensions can be installed in this duct. Along with the losses in the lattice, the local losses of the side opening will also be taken into account. This feature is being improved. Ask for updates.
After successful calculation, you can adjust the sections as follows:
(for rectangular ones) left-click on the height mark H[mm], then right-click on it - a menu will appear with a list of sections (the first number is speed), from top to bottom the height is increasingly flattened; select the desired section, focusing on the desired speed... (this menu offers sections for which calculations are possible).
it is necessary to correctly assign sections to sections depending on
expenses. Below is data taken from German methods, in
according to which example exhaust system B.6 was made
TABLE 1. Air velocities in mains and branches of supply and air ducts exhaust systems depending on the purpose of the air duct.
┌─────────────┬────────────────────────┬─────────────────────────┐
│ Purpose │ Supply │ Exhaust │
│ object ├───────────┬────────────┼────────────┬ ───────── ───┤
│ │Mainline │ Branches│ Mainline│ Branches│
│Residential buildings │ 5 │ 3 │ 4 │ 3 │
├─────────────┼───────────┼────────────┼────────────┼────────────┤
│Hotels │ 7.5 │ 6.5 │ 6 │ 5 │
├─────────────┼───────────┼────────────┼────────────┼────────────┤
│Cinemas, │ 6.5 │ 5 │ 5.5 │ 4 │
│theaters │ │ │ │ │
├─────────────┼───────────┼────────────┼────────────┼────────────┤
│Administration│ 10 │ 8 │ 7.5 │ 6 │
├─────────────┼───────────┼────────────┼────────────┼────────────┤
│Office │ 10 │ 8 │ 7.5 │ 6 │
├─────────────┼───────────┼────────────┼────────────┼────────────┤
│Restaurant │ 10 │ 8 │ 7.5 │ 6 │
├─────────────┼───────────┼────────────┼────────────┼────────────┤
│Hospital │ 7.5 │ 6.5 │ 6 │ 5 │
├─────────────┼───────────┼────────────┼────────────┼────────────┤
│Library │ 10 │ 8 │ 7.5 │ 6 │
└─────────────┴───────────┴────────────┴────────────┴────────────┘
TABLE 2. Percentages of air quantity and area
air duct sections.
|
% area water duct sections | |||||||
Take the percentage of area from columns 2, 4, 6, 8.
Using the example of system B.6, see how to apply the data from table N2,
to correctly assign sections of air ducts.
F = L/3600 x V where
L - air flow in the area m3/h
V - air speed (can be assigned according to table N1 depending on
purpose of the system (supply or exhaust)) and the type of building.
Determine the percentage of air flow:
%L = Lch.(considered) / Lch.1
Performers:
Volkova Tatyana Arkadyevna (495) (d.), (495) (b.)
Volkov Vsevolod
Internet site: www. *****
