technology in refrigeration
Refrigerant pipes calculation
The following chart shows maximum and minimum cooling capacity recommended for each suction line (gas line) pipe, as well as the average
cooling capacity recommended for liquid line pipes.
Selection chart
VERY LOW TEMPERATURE
Evaporation temp.: -40ºC, isolation 30mm
LOW TEMPERATURE
Evaporation temp.: -30ºC
MEDIUM TEMPERATURE
Evaporation temp.: -10ºC
HIGH TEMPERATURE
Evaporation temp.: +0ºC
Evap.
temp.
ºC
56
Nominal
diameter
for copper
refrigerant
pipes
LIQUID LINE
GAS SUCTION LINE FROM EVAPORATING UNIT TO COMPRESSOR
Recommended
Recommended Maximum cooling capacity (kW) for a 1K saturation temperature drop
averange
minimum
in, depending on the pipes equivalent length.
R404A load
cooling
cooling
gr/m
capacity
capacity
10 m
15 m
20 m
25 m
30 m
40 m
50 m
(kW)
(kW)
1/4”
2
3/8”
5
20
50
0,6
1,2
1,0
0,8
0,7
0,7
0,6
0,5
1/2”
9
100
1,2
3,0
2,4
2,1
1,8
1,7
1,4
1,2
5/8”
15
160
1,9
5,8
4,6
3,9
3,5
3,1
2,7
2,4
3/4”
23
240
3,0
9,6
7,7
6,6
5,8
5,3
4,5
4,0
7/8”
32
340
4,0
15
12,0
10,3
9,1
8,2
7,0
6,2
1”
42
450
5,5
22
17,6
15,0
13,3
12,0
10,3
9,1
1 1/8”
55
570
7,0
25
24
20,5
18,2
16,4
14,0
12,4
1 3/8”
80
850
10
38
38
35
31
28
24
21
1 5/8”
110
1200
15
54
54
54
49
44
38
34
2 1/8”
200
2100
30
95
95
95
95
94
80
71
1/4”
1,7
20
3/8”
4,5
50
0,4
0,9
0,7
0,6
0,5
0,5
0,4
-
Liquid line pipe selection
Once it is known a cooling capacity value at a particular
evaporating temperature, a diameter for refrigerant liquid
line pipes should be selected deppending on the cooling
capacity recommended with a ± 50% margin.
Suction line (gas line) pipe selection
Once it is known a cooling capacity value at a particular
evaporating temperature, this value should be between the
recommended minimum cooling capacity and the maximum cooling capacity of the selected pipe, depending on
its equivalent length.
To guarantee a correct oil return through vertical pipes it
is recommended to select a pipe diameter for which the
cooling capacity is at least a 50% higher than the recommended minimum value.
It is recommended not to select a pipe which values are in
red color, due to a cooling capacity loss higher than 15%
associated to these values.
It is recommended not to select a pipe which values are
in blue colour, associated to a maximum gas speed of 15
m/s.
Suction line pipes thermal isolation
1/2”
9
100
0,8
2,1
1,7
1,4
1,3
1,1
1,0
0,9
It is suggested the following minimum isolation thickness,
made in elastomeric material, to avoid any water condensation in ambient conditions of 25ºC and 50% RH:
5/8”
14
160
1,3
4,0
3,2
2,7
2,4
2,2
1,9
1,6
 High and medium temperature: 10 mm
3/4”
22
240
2,0
6,7
5,3
4,6
4,0
3,6
3,1
2,7
 Low temperature (Tev: -30ºC):
20 mm
7/8”
30
340
2,8
10,4
8,3
7,1
6,3
5,7
4,9
4,3
 Very low temperature (Tev: -40ºC): 30 mm
6,3
1”
40
450
3,7
13
12,2
10,4
9,2
8,4
7,1
1 1/8”
50
570
4,7
17
16,7
14,2
12,6
11,4
9,7
8,6
1 3/8”
75
850
7,0
25
25
24,1
21,3
19,3
16,5
14,6
1 5/8”
110
1200
10
35
35
35
34
31
26
23
2 1/8”
200
2100
18
65
65
65
65
65
56
50
1/4”
1,5
20
3/8”
4
50
0,25
0,4
0,3
0,25
Calculation basis
The present calculation method, developed by Intarcon, is
provided as a guideline, being the project technician responsible for making verifications. The calculation method
is only used to calculate R404A refrigerant pipes made in
copper specifically for refrigeration purposes.
Maximum cooling capacity shown for each situation are
based on a 1K saturation temperature drop, with a gas
speed limit of 15 m/s (values in blue colour).
1/2”
8
100
0,45
0,9
0,7
0,6
0,5
5/8”
14
160
0,7
1,6
1,3
1,1
1,0
0,45
0,9
0,8
0,7
3/4”
20
240
1,1
2,8
2,2
1,9
1,7
1,5
1,3
1,1
7/8”
30
340
1,5
4,3
3,4
2,9
2,6
2,3
2,0
1,8
1”
40
450
2,0
5,8
5,1
4,3
3,8
3,4
2,9
2,6
1 1/8”
50
570
2,5
7,3
6,9
5,9
5,2
4,7
4,0
3,6
1 3/8”
70
850
4,0
10,5
10,5
10,0
8,8
8,0
6,8
6,0
1 5/8”
100
1200
6,0
15,0
15,0
15,0
14,2
12,8
10,9
9,7
2 1/8”
170
2100
10
28
28
28
28
27
23
21
1/4”
1,5
20
3/8”
4
50
0,2
0,2
0,6
1/2”
7
100
0,3
0,5
5/8”
12
160
0,5
1,0
0,4
0,8
0,7
3/4”
18
240
0,8
1,7
1,4
1,2
1,0
7/8”
25
340
1,1
2,7
2,1
1,8
1,6
1,4
1”
35
450
1,5
3.5
3,1
2,7
2,3
2,1
1,8
1,6
1 1/8”
40
570
2,0
4.5
4,3
3,6
3,2
2,9
2,5
2,2
0,9
1,2
1 3/8”
60
850
3,0
6.5
6.5
6,2
5,5
4,9
4,2
3,7
1 5/8”
90
1200
4,0
9.1
9.1
9.1
8,8
7,9
6,8
6,0
2 1/8”
150
2100
7,0
17
17
17
17
16,8
14,3
12,7
Minimum cooling capacity recommended in suction line is
relative to a minimum speed of 4 m/s in medium and high
temperature, 5 m/s in low temperature and 6 m/s in very
low temperature applications.
The cooling capacity values have been calculated according to a 45ºC condensation temperature, with superheat
10K and subcooling 0K.
technology in refrigeration
Equivalent length
The equivalent length of a refrigeration pipe is usually about 1,2 to 5
times longer than its real length, depending on the number of elbows
and chokes in it. As a guideline, the values shown in the following chart
can be used to get an approximate calculation:
Equivalent length (m)
Nominal diameter for
copper refrigerant pipes
90º elbow
T-shape coupler
straight flow
angular flow
Choke
Siphon
Angular
service
valve
Gate
service
valve
3/8”
0,7
0,3
0,8
0,3
1,1
1,8
0,2
1/2”
0,8
0,3
0,9
0,4
1,2
2,0
0,2
5/8”
0,9
0,4
1,0
0,5
1,4
2,2
0,3
3/4”
1,0
0,4
1,2
0,6
1,6
2,5
0,3
7/8”
1,1
0,5
1,4
0,6
1,8
3,0
0,3
1”
1,2
0,5
1,5
0,7
2,0
3,5
0,3
1 1/8”
1,4
0,6
1,8
0,8
2,3
4,0
0,4
1 3/8”
1,7
0,7
2,2
1,0
2,7
5,0
0,5
1 5/8”
2,0
0,9
2,7
1,2
3,5
6,0
0,6
2 1/8”
2,5
1,1
3,3
1,5
4,3
8,0
0,7
Recommendations
Example 1.- cooling pipes calculation
Sizing up cooling pipes to service one evaporating unit of
a cooling capacity of 1500W in a -20ºC cold room with
DT1 = 7K.
We size up the liquid pipes according to recommended
cooling capacity, it is acceptable a pipe diameter of 1/4”.
We accept as premise a equivalent length of 1,5 times
longer than real length. In our situation:
Leq = 1,5 x 20 m = 30 m
We accept a pressure drop equivalent to a 1K saturation
temperature drop, we see in 30m column, in low temperature section (evaporation temp. -30ºC), and we found
that:
 3/4” pipes are related to a recommended maximum
cooling capacity of 1,5 kW, but with a cooling capacity loss higher than 15% (values in red colour).
 7/8” pipes are related to a recommended minimum
cooling capacity of 1,5 kW, but making difficult the
gas return in vertical pipes.
It is recommended to take notice of the following tips for a better
cooling pipes design:
• Designing the pipes as straight as possible, with the lowest number
of elbows, couplers and refrigerant jets.
So, it is recommended to utilize 7/8” pipes in horizontal
and descending piping and 3/4” only in ascending piping.
We can check out that equivalent length estimated is right, indeed:
Leq = 20m + 3x 1,1m (elbow) + 2x 1,6m (siphon) +
+ 2,5m (service valve) = 29 m
• Installing a siphon in vertical pipes in suction lines every 3 metres.
• Giving the horizontal stretch a little inclination down to the compressor.
• Connection from the evaporating unit to the suction line collector
should be always undertaken from the unit up to the collector.
Example 1
Sizing up a multiservice installation pipes, as seen in scheme, to service 5 evaporating unit of 1000W each one in
0ºC cold rooms with DT1 = 8K.
We size up the liquid pipes according to recommended
cooling capacity, it is acceptable a pipe diameter of 1/4”
for a cooling capacity between 1000 and 2000W and
a pipe diameter of 3/8” for a cooling capacity between
3000W and 5000W.
5m x 7/8”
3m x 7/8”
We accept as premise a equivalent length of 1,5 times
longer than real length to the most distant evaporating
unit. In our situation:
3m x 3/4”
1/4”
1/4”
3m x 7/8”
Example 2.- multiservice installation calculation
Siphon every 3 metres
in vertical pipes
1/4”
3m x 3/4”
1/4”
We accept a pressure drop equivalent to a 2K saturation
temperature drop, we see in 25m column (50m÷2), in
medium temperature section (evaporation temp. -10ºC),
and we found that:
 For a cooling capacity of 1000W it is recommended
a 1/2” pipe,
3m x 7/8”
Example 2
Leq = 1,5 x 35 m = 52,5 m
 of 2000W it is recommended a 5/8” pipe,
1/4”
 of 3000W it is recommended a 3/4” pipe,
5m x 7/8”
 and of 5000W it is recommended a 7/8” pipe,
We can check out that equivalent length estimated is right, indeed:
1/4”
5m x 1/2”
5m x 5/8”
10m x 7/8”
3/8”
1/4”
Leq = 35m+ 1,1m (elbow) + 3x 1,8m + 1,2m (siphons) +
+0,5+0,6+0,6 (chokes) + 2,5+0,2 (valves)
= 47m
3/8”
1/4”
5m x 3/4”
1/4”
5m x 1/2”
5m x 5/8”
5m x 1/2”
5m x 1/2”
5m x 1/2”
5m x 1/2”
5m x 1/2”
57