Pipe Flow Calculations Forum

What i am given: There is a 75kw heater that circulates fluid to two heat exchangers. Fluid enters each heat exchanger at 200 Celsius and exits at 150 Celsius with a flow rate of 0.00197m^3/s. The Length of the pipe to each heat exchanger is 10 m with 5 elbows. The specific heat, density, and viscosity are given also and are 1.95 kj/kg K, 900kg/m^3, and 0.38E-3 N-s/m^2 respectively.

How can i use this information to determine the Diameter of the pipe necessary for this system. Any guidance is appreciated.

You need either pressure drop in pipe or velocity.
Now, if you want to have 1 m/s velocity than you can calculate diameter for given flow rate and that velocity.
http://www.pipeflowcalculations.com/flowrate/index.htm
I get 50 mm internal diameter tube.

After that you should check pressure drop, to be sure that you have sufficient pressure on the start of pipe.
http://www.pipeflowcalculations.com/pre ... /index.htm

OR,

If you want to have certain pressure drop, than based on it you should calculate diameter for given flow rate.

Local resistance factor K should be calculated also at:
http://www.pipeflowcalculations.com/res ... /index.htm
I get for 2" tube and R/D=1.5 K=0.266 for one elbow, and for 5 five it is K=1.33

For your values I get pressure drop of 21 mbar, which is I think small pressure drop, so maybe you can go with 2 m/s velocity and get smaller pipe.

Thanks for the guidance, i just have one more question:

How do i know that the pressure drop is significant, for example what makes using a velocity of 2m/s better than 1 m/s in order to get a larger pressure drop.

with 2 m/s you will get smaller pipe - which is cheaper, but you have to check pressure drop not to be too high, because if the pressure drop is to high you will have no flow at all.