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If different pressure drops are needed, the cooling capacity shall be corrected with the following formula:
Where:
Pf: cooling capacity
P : cooling capacity shown into the table 1
Le : equivalent length of the table 1
Leff : actual equivalent length
ΔT : required pressure drop
ΔTtab: press
ure drop shown into the table 1
The equivalent length can be calculated as follows:
A fictitious length for each curve or branch or concentrated drop shall be added to the real lengths, corresponding to the linear tube
length that would give the same pressure drop caused by the curve or by the branch.
Those fictitious lengths are shown in the table 2 and shall be considered effective for fully open valves.
Table 2:
Equivalent lengths (in meters) for concentrated drops.
The table1 is referred to a condensation temperature of 40°C.
In case of different condensation temperatures the following correcting values shall be applied to the cooling capacity.
Cond. Temp (°C)
20
30
40
50
K suction line
1.18
1.1
1
0.91
K discharge line
0.8
0.88
1
1.11
Table 2.a:
Cooling capacity of the correction factors in function of the condensing temperature.
Using the table 1 and the suggested correction factors it is possible to choose the proper diameter in accordance with the requested
cooling capacity and the evaluated pressure drops.
Once the choice is taken a check shall be made by calculating the real pressure drop using the following formula.
