Pipeline Resistance

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Lama Sinto Member Join Date: Jun 2010 Posts: 7	Pipeline Resistance 07/22/2010 6:14 AM
	I have a ramifying network of pipeswhich join to a main duct of greatest diameter. At the end of the branches are suction mouths (56). The suction force comes fromt a centrifugal fan. Sample archetype: My problem is i want to be sure of what will happen to the system load curve and the flow rate in the following conditions: 1. With the suction firce constant, 15 suction mouths are closed completely 2. in the same fan condition, all suction mouths are closed 3. how will system load vary as a function of the number of suction mouths open 4. what will be the corresponding variation on the flow rate along the pipeline, before and after the fan (upstream and downstream) 5. for 56 mouths i have a flow rate Q1. if i wish to have the same flow rate for 48pots, what will be done to the pipeline or the fan
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#1 Re: Pipeline resistance 07/22/2010 7:39 AM
	The flowrates elsewhere on the network will increase, and the inlet pressure to the fan will reduce. The flowrate will become zero, in which case it is time to turn the fan off. This can be established by testing. ditto. Either: modulate the speed of the fan so that the flowrate is maintained. Fit a variable speed drive to the wiring feeding the fan, or Fit a damper in the fan pipework so as to throttle the flow through the fan while it is running. __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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Tornado Guru Join Date: May 2009 Location: Richland, WA, USA Posts: 21017 Good Answers: 795	#2 Re: Pipeline Resistance 07/23/2010 12:59 AM
	This problem has been thrashed to death in a number of related threads, mostly involving lots of overthink without understanding simple things. Put a pitot tube in a representative location, or maybe an "Annubar," using this to control a fan VFD to maintain near-constant pressure difference, and hence flow. __________________ In vino veritas; in cervisia carmen; in aqua E. coli.
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Lama Sinto Member Join Date: Jun 2010 Posts: 7	#3 In reply to #2 Re: Pipeline Resistance 07/23/2010 2:51 AM
	Actually the problem raised here is the fluid mechanics theory behind such ductwork. That is the behaviour of the global system resistance to flow as suction mouths are progressively closed.
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alberto galindo Active Contributor Join Date: Jul 2010 Posts: 15	#4 Re: Pipeline Resistance 07/23/2010 8:27 AM
	Este es ploblema tipico de mecanica de fluidos, y su calculo tendra los siguientes pasos 1-datos del sistema: curva del ventilador, presion caudal Curva de los Dampers Diamentros de los ductos Ascesorior, te, reducciones,etc 2- se hace correr el calculo para las distintas hipotesis de trabajo con Dampers cerrados con Dampers totalmente abiertos con dampers regulados a los caudales apropiadas si se seleccionan los nodos apropiadamentes se puede determinar la presion y caudal en cada nodo saludos a todos Ing galindo, Alberto
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