Balancing

Owing to the fall in pressure in the length of the main duct, the air outlets at the initial end will deliver more air, and those at the extreme end less air, than the mean if the system is not bal­anced.

Unbalanced system example

In a blowing system with round piping designed on the percent­age system there are 2 similar lines of ducts each with 14 out­lets. No balancing adjustments were provided, and tests were

Outlet pop No.

Line 1 m3/s

Line 2 cfm

1

0.107 {+ 12% on Mean)

0.093 (+ 19% on Mean)

2

0.106

0.091

3

0.104

0.089

4

0.103

0.088

5

0.101

0.085

6

0.099

0.083

7

0.098

0.080

8

0.094

0.078

9

0.093

0.077

10

0.091

0.073

11

0.088

0.070

12

0.086

0.067

13

0.083

0.065

14

(74% of No 1) 0.079 (-17% on Mean)

(66% of No 1) 0.061 (-22% on Mean)

1.332

1.100

Table 3.9 Variation in flow on a typical unbalanced system

Made for the air volume flowrate discharged. The results are To balance the system, the resistance from A to B must be given in Table 3.9. equal to that from AtoC. the difference is the friction of the main

Between B and C and this must be compensated by adding re­sistance at B. This has been checked by experiments as will be seen later.

подпись: made for the air volume flowrate discharged. the results are to balance the system, the resistance from a to b must be given in table 3.9. equal to that from atoc. the difference is the friction of the main
between b and c and this must be compensated by adding re-sistance at b. this has been checked by experiments as will be seen later.

Posted in Fans Ventilation A Practical Guide


Добавить комментарий

Ваш e-mail не будет опубликован. Обязательные поля помечены *