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19-02-2003 17:42
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Step 3. Pressure loss analysis.
After the entire installation is completed, the program gathers all information needed
for pressure loss analysis and regulation: operating parameters, hydraulic
characteristics of elements and installation geometry.
After selecting the "pressure loss analysis" command, FDBES performs calculation
of flow capacities and pressure losses for all designed cooling and heating systems.
The flow quantity is a function of the cooling / heating power specified on terminal
units and of the temperatures given for the cooling / heating fluid in both the
supply and return pipelines. The program calculates pressure drops based on Darcy-Weissbach
equation and determines the linear pressure loss coefficient (Lambda) using the
Colebrook-White equation. Once all data is available to determine flow values and the
installation geometry, Coolpack performs pressure drop calculations, automatically
adjusts regulation valves and displays the resulting report in a well-readable format.
The first loop displayed in the "Pressure loss analysis" dialog box is the critical one
(the loop with the highest pressure drop). Empty lines separate loops belonging to the
individual terminal units, with each branch being specified in the sequence that
pressure loss analysis is performed - first showing the supply and then return pipes.
The pressure reduction displayed next to terminal units indicates the pressure that
should be reduced using the balancing valve placed on the path between the terminal
unit and the previous branching element. Owing to the "show element" function,
the user may easily locate on the drawing any element chosen in the reported table.
The program proposes a suitable Kv setting for control valves while the are being
placed and calculates the adjustments of balancing valves automatically. However,
correction of the authority (by changing Kv) of control valves and selection of
the size and type of balancing valves should be done by the designer - who should
ensure that pressure reduction is not displayed on any of the terminal units.
In cases when calculations result in values less than zero or when minor errors
are displayed in the pressure loss report, please check if the installation is
connected properly. The hints displayed in the command line can be very helpful.
The user may modify the used piping technology (absolute friction in [mm]) any
time before calculations are performed through the "Size table" tab of the "Settings" dialog box.
The specification resulting from this analysis may be exported to text file in
tabular form or to Microsoft Excel: an Excel window is opened automatically and
contains the pressure loss analysis specification for each system, grouped in
separate worksheets having the corresponding system symbol as their name.
The program also formats these tables automatically, including font size and
cell style settings, preparing the specification for printing.
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