Rectangular vs. round pipe flow

[sathr]

I have limited space for a water jacket and am concerned about restricting flow compared to the rest of the circuit. The water jacket is .075" X 3.5" cross section and the rest of the circuit is .375 ID round. How much more resistance does the rectangular pipe have? Or, what is the relationship between rectangular cross section and flow-resistance? Thank you for any assistance.

 

[fredb]

Hello

From my handy dandy ductilator a 5" round has cross-section
of 19.625 sq in. Equivalent rectangular is: 4" x 5.25" and has cross-section of 21 sq in.

 

[arto]

How about use the Hydraulic Diameter?

Dh = 4A/P