2 replies to this topic

[jacobr]

Hi,

I am looking to design the outlet line of a vessel. The fluid(water) will have to be emptied in approx. 1 hour. Currently the drainage line is sized at 1". A constant pressure of 1 bar exists in the vessel. I require laminar flow. Im not an expert in fluid mechanics so am not sure whether to reduce the pressure in the vessel or increase the diameter of the drainage line to 1.5" to ensure laminar flow and the correct flowrate. Again the vessel must empty in 1 hour with laminar flow. Any advice would help

[Technocrat]

Can you please explain me the application, why do you want do empty the vessel within one hour only and by laminar flow only? What is the flow rate you desire?

[djack77494]

jacobr,
Your "requirement" for laminar flow makes no sense at all to me. I think it safe to say that I've never seen laminar conditions for water flow in pipeline. I can't imagine why one would strive for this, and with water's physical properties, and especially its low viscosity, I would think it very hard to achieve laminar flow. If you are draining from a pressurized 1 barg vessel to atmospheric pressure, you can almost surely neglect the static head in your vessel and just use 1 bar differential as your dP. Count your pipe length and fittings and you end up with a straight forward liquid flow problem. Solve using the Darcy equation or other suitable method. (I highly recommend that you obtain Crane TP410 to use as a refenece for this and future hydraulic calce.) You can even use the methods described in Crane to impose laminar flow on your situation. Offhand, I would probably try a trial & error approach. Assume a line size. Calculated flowrate to empty vessel in one hour = vessel volume / 1 hour. Calculate Reynolds Number. As needed, revise pipe diameter until Reynolds Number dictates laminar flow (<2000 if memory serves me). Done.