Friction Loss in Y-type Pipe Calculation

[simelliott]

Hi all,

I am trying to calculate the friction losses found in a suction inlet pipe for a fire pump. I have attached an image which shows the pipe we are intending to use, but have no idea how to calculate the expected friction losses we would find when using it.

I know how to calculate for straight pipe and for bends, but no idea about interconnecting pipes such as this?

The section consists of 2 x 5" pipes joining into a 6" diameter at the pump inlet. The angle of the 5" pipes is 90 degrees if that helps?

Does anyone have any suggestions on where to start?

Thanks in advance.

 

[minosdis]

How accurate does your estimate need to be? You could just take the average of a straight pipe and a 45 deg bend. Friction loss calculations are a good deal of inherent error to begin with, as there are many variables such as temperature, Re number, velocity, actual wall roughness, etc that can make the typical models highly inaccurate. Your best bet may be to contact the manufacturer of the fitting to see if they have a K value.

 

[Q_Goest]

Assuming one of the branches has no flow in it, I would use the equivalent length for a miter bend of the same angle as indicated in Crane 410 (attached).