Starting with Bernoulli's Equation...
Starting with Bernoulli's Equation...
(OP)
Does anyone out there have a reference showing how to calculate the volume flowrate (cfm) vs. static pressure (inches water) curve for an aircooled electronics enclosure? This would involve consideration of duct losses due to expansion, contraction, splits, turns, etc. Years ago I saw where someone started with Bernoulli's equation but I can't seem to put my hands on it anymore.
My goal is to determine the enclosure's operating point given the fan's published static pressure vs. flowrate curve; I want to overlay the two curves on the same graph and find the intersection (the operating point).
I've been able to find plenty of sources who talk about doing the above but haven't been able to find a source that actually DOES it and shows how to do it!
Thanks in advance for your help!
Regards,
Tunalover
My goal is to determine the enclosure's operating point given the fan's published static pressure vs. flowrate curve; I want to overlay the two curves on the same graph and find the intersection (the operating point).
I've been able to find plenty of sources who talk about doing the above but haven't been able to find a source that actually DOES it and shows how to do it!
Thanks in advance for your help!
Regards,
Tunalover





RE: Starting with Bernoulli's Equation...
Once your are done with system resistance at maximum flow, it is a cake walk to construct a system resistance curve as follows.
Take flowrate on x-axis and system resistance on y-axis. Mark the max. flow rate and corresponding system resistance on the graph(say, point A) and drop a vertical line from this point to the x-axis (say, point B. So AB will be parallel to y-axis). Draw a line OA with O as origin of the graph. Now split AB into 5 parts and name them C, D, E and F from x-axis. Draw OC, OC, OE and OF. Draw lines parallel to x-axis from C,D,E and F to cut OA and name them G, H, I and J respectively. Draw vertical lines parallel to y-axis from G, H, I and J to cut OC, OD, OE and OF respectively at K, L, M and N. Join K, L, M and N and you will get a parabloa. This is your system resistance curve. You can take as many no. of point as you wish to make a smooth curve, but I took four points for simple explanation.
Each point on this curve will give you system response if you fix any one parameter. (either flow or resistance) Now you have to superimpose this curve on various fan performance curves to check which fan best suits your application. Maximum possible, try to select a fan which operates at best efficiency point.
The above said example is the simplest one and some corrections are to be done depending upon different applications.
Regards,
RE: Starting with Bernoulli's Equation...
Looks like you've done this before! I was actually looking for more detail e.g. formulas. Do you know where I might find a worked out example?
Tunalover
RE: Starting with Bernoulli's Equation...
You can get it from Amazon (they have links to used versions of this book too.)
RE: Starting with Bernoulli's Equation...
sounds like a definite one for my bookshelf,
Thank You,
Wilg
RE: Starting with Bernoulli's Equation...
Tunalover
RE: Starting with Bernoulli's Equation...
Hope that helps.
RE: Starting with Bernoulli's Equation...
Tunalover