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HVAC ducting principles and calculations

Page history last edited by jim mason 14 years ago

Most of the issues encountered in syngas output distribution are identical to those confronted in the HVAC industry. The design of blowers, flow rates vs pipe sizes, pressure drop in straight vs curved runs, particulate entrainment and transport, orifice shapes, etc etc, all are well explored and solved in the HVAC trades. So let's pay attention and try not to reinvent the wheel here.

Here's the best paper i've found to date explaining the design and engineering principles of HVAC systems. It is put out by Cincinnati Fan in Mason, Ohio (no, no relation). Click here for the .pdf paper: CincinnatiAirDuctingandEntrainmentData.pdf

Here's one interesting chart from the paper, showing pressure losses across different types of orifice entrances. The difference in losses across a straight pipe inlet vs a flared or skirted inlet are quite striking. This will have some relationship to DIY ejector design (but please note the diagram below is not about ejectors, but rather just simply "entrance losses" for pipe inlets. See the orginal .pdf file, what appears to be an ejector nozzle is actually a line with an arrow, indicating the direction of flow).

Comments (1)

This is very interesting data Jim. I seem to have a low vacuum (< 1" H2O) in my cowling and this data certainly supports my idea that where my cyclone is tied into the cowling's mounting flange that I have flow problems and consequently the low vacuum. My first thought was that my fan may not be spinning fast enough, but now I believe my problem actually stems from the fact that I just didn't do a very good job cutting the opening into the cyclone, or possibly the cyclone to filter transition. Seeing the types of orifices, it makes me wonder how I could fab something to decrease this loss. I would suspect that this would even extend to possibly cutting a chamfer or countersink on the air inlets all the way back at the beginning of the chain.

Do you use any of these more efficient models on the GEK? Seeing the fab pics you've got, I haven’t seen you do anything like that for the cowling => cyclone, cyclone=> filter, filter => fan, or the fan => hose. Given how much of a commodity the pipe fittings are, I can’t think of any more economical way to move the gas more smoothly, but maybe there is something out there I’m just not thinking of...

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