Manifolds in composite specifically designed for radiant ... - Caleffi

Hydraulic characteristics
∆P (mm w.g.)
1000
500
200
100
900
800
700
600
450
400
350
300
180
160
140
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90
80
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60
50
250
45
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35
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10
25
18
16
14
12
20
25
30
Example of calculation of total loss of head
Supposing we need to calculate the loss of head of a manifold with three outlets with the following characteristics:
Total manifold flow rate: 350 l/h
The pipes of the three loops have the following characteristics of flow rate and loss of head:
Circuit 1 Circuit 2 Circuit 3
∆P1 = 10 kPa ∆P2 = 15 kPa ∆P3 = 7 kPa (1.2)
G1 = 120 l/h G2 = 150 l/h G3 = 80 l/h
We calculate each term of the formula (1.1), using the relationship:
∆P = G 2 /Kv 0.01 2
35
40
45
50
60
70
80
90
· G = flow rate in l/h
· ∆P = loss of head in kPa (1 kPa =100 mm w.g.)
· Kv 0,01 = flow rate in l/h through the device, which corresponds to a head loss of 1 kPa
It should be stressed that the calculation of ∆PTot. must be made taking account of the circuit in which there are the greatest head losses
distributed along the entire loop of the panel piping.
In the case we are examining, the relevant circuit is No. 2.
It follows that:
∆PBV = 1502 /1002 = 2,25 kPa
∆PLoop = 15 kPa
∆PSV = 1502 /2402 = 0,39 kPa
∆PF Man. = 3502 /16002 = 0,05 kPa } Values obtained by disregarding variations due to flow rate to each branch circuit
∆PR Man. = 3502 /16002 = 0,05 kPa
∆PBall V = 3502 /16502 = 0,04 kPa
By means of (1.1) adding up all the calculated terms, we have:
∆PTot.= 2,25 + 15 + 0,39 + 0,05 + 0,05 + 0,04 = 17,64 kPa
100
Flow rate balancing valve fully open
Shut-off valve
120
140
160
180
- Kv = flow rate in m 3 /h for a loss of head of 1 bar
- Kv 0,01 = flow rate in l/h for a loss of head of 1 kPa
200
250
300
350
400
450
Kv
1,00
2,40
500
G (l/h)
∆P (kPa)
Note:
Because of the low head losses for the ball valves and the manifolds, the three terms relating to them can be neglected.
In general, the total head loss is reasonably approximate to that of the branched circuit of the panel.
9
8
7
6
2,5
10
5
4,5
4
3,5
3
2
1,8
1,6
1,4
1,2
1
0,9
0,8
0,7
0,6
0,25
0,5
0,45
0,4
0,35
0,3
0,2
0,18
0,16
0,14
0,12
0,1
Kv 0,01
100
240
∆P (mm w.g.)
1000
500
200
100
900
800
700
600
450
400
350
300
180
160
140
120
90
80
70
60
50
20
10
250
45
40
35
30
25
18
16
14
12
500
600
Flow or return manifold 3÷6 outlets
Flow or return manifold 7÷10 outlets
Ball valve
* Average value
700
800
900
1000
1200
1400
1600
1800
2000
2500
3000
Kv
16,0*
12,0*
16,5*
3500
G (l/h)
∆P (kPa)
4000
9
8
7
6
2,5
10
5
4,5
4
3,5
3
2
1,8
1,6
1,4
1,2
1
0,9
0,8
0,7
0,6
0,25
0,5
0,45
0,4
0,35
0,3
0,2
0,18
0,16
0,14
0,12
0,1
Kv0,01 1600*
1200*
1650*