98
Aquarea air / water heat pump – design handbook 07 / 2014
Project Design
Hydraulics
Pumping height and pipe network resistance
Copper pipe nomogram
Sample calculation of the rated
pipe diameter for the
WH-MXF12D6E5 with a
rated volume flow of 34 l / min:
This results in a rated copper pipe
width of 35 × 1.5 at a pressure drop
of 0.16 kPa / m and a circulation
speed of 0.7 m / s
Based on these criteria, the required rated pipe diameter can be read
from the copper pipe nomogram (see example). The recommended
range is highlighted in colour. In order to determine the pipe network re-
sistance of an entire line, the pressure drop per metre must be multiplied
by the length of the respective sub-sections, and the pressure drop of
the sub-sections must be added. The total resistance of a line is calcu-
lated from the total pressure drop of the sub-sections multiplied by an
estimated supplementary factor of 1.5.
0,05
50
60
80
100
140
200
0,06
Pressure drop [kPa
/
m]
Circulation rate [l
/
h]
Circulation rate [l
/
min]
Pressure drop [Pa
/
m]
20
30
40
50
60
80
100
200
300
400
500
600
700
800
1000
2000
3000
0,3
0,5
0,7
0,8
1,0
1,3
1,7
3,3
5
7
8
10
12
13
17
33
50
0,08
0,1 0,12
0,16
0,2
Tipp 2: Note the rated pipe diameter
The pressure drop in the pipelines increases exponentially with the volume
circulation. That means that doubling the rate of circulation increases the
pressure drop by a factor of 4! This is due to the circulation speed in the
pipe, which depends on the rate of circulation and the internal pipe diameter.
As an alternative to pipe network calculations, the pressure drop in pipe
sections can be determined via nomograms. The following applies as a
recommendation for designing main distribution lines:
• The circulation speed should be between 0.3 to max. 1.5 m / s
• The pressure drop per metre should be roughly 0.1 kPa / m
