Chilled Water Piping Design
Requirements :
- Water Flow Rate . ( GPM )
ECWT : Entering Chilled Water Temperature = 54 F' = 12 C' ( in Egypt )
LCWT : Leaving Chilled Water Temperature = 44 F' = 6 C' ( in Egypt )
ᐃT = ECWT - LCWT = 10 F
Q = MCPᐃT
M : Water Flow Rate ( GPM )
GPM = T.R * 24 / ᐃT
- IN Egypt ( 1 T.R = 2.4 GPM @ ᐃT = 10 F' )
- IN Arab Gulf States ( 1 T.R = 2.4 GPM @ ᐃT = 12 F' )
Pipe diameters are determined and there are factors:
- The velocity of the water inside the pipes ( 2 : 10 feet / s ) and the appropriate value ( 5 fteet )
- The Pressure drop should not exceed ( 10 ft / 100 ft) and the appropriate value ( 4 ft / 100 ft )
- Pipe Material ( Galvanized steel or Seamless black steel schedule 40 )
- Chilled water cycle is closed
Pipe diameters can be determined by one of the methods :
- Friction Chart
- Friction Table
- Pipe Sizer Program
- Pipe Flow Wizard Program
Example :
ᐃT = 10 F' velocity = 5 ft/s
GPM = T.R * 2.4
We start with the farthest point
- @ AHU 1 Flow Rate = 20 * 2.4 = 48 GPM
- @ AHU 2 Flow Rate = 15 * 2.4 = 36 GPM
- @ AHU 3 Flow Rate = 20 * 2.4 = 48 GPM
- @ AHU 4 Flow Rate = 15 * 2.4 = 36 GPM
- @ AHU 5 Flow Rate = 10 * 2.4 = 24 GPM
We start with the farthest point
- From ( 3 s.t ) to ( 4 s.t ) 24 GPM
- From ( 2 s.t ) TO ( 3 s.t ) = 24 + 36 = 60 GPM
- From ( 1 s.t ) TO ( 2 s.t ) = 48 + 60 = 108 GPM
- From ( G.F ) TO ( 1 s.t ) = 108 + 36 = 144 GPM
- From ( Chiller ) TO ( G.F ) = 144 + 48 = 192 GPM
Through this table, we get the pipe diameters
You can use the chart if you like
Thank You
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