Forum Index » Editor's Roundtable » The Myth of Pressure Regulators


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Hikin' Jim
(hikin_jim) - M

Locale: Los Angeles, CA, USA
Re: Re: regulators on 07/10/2012 20:01:07 MDT Print View

Not knowing anything about the overall pressure drop across jets and thru the stoves, it is theoretically possible for a pressure regulator with a large orifice to pass more gas with a lower dP than a small fixed restriction can. This would enhance low pressure operation when the pressure in the cannister is low. IE, it would be a function of the size of the regulators adjustable orifice, not the fact that it is a regulator.
Stuart Robb advanced an explanation earlier (elsewhere on BPL) as to why Jetboils with regulator valves outperformed Jetboils with conventional needle valves. Essentially, if I understood Stuart correctly, he posited that the regulator made a larger diameter jet safe by limiting the gas flow when the canister pressure is high while allowing for improved gas flow when canister pressure is low in cold conditions.

HJ
M B
(livingontheroad) - M
flow on 07/11/2012 18:58:48 MDT Print View

"That's true until it hits sonic velocity (which gases can do at these pressures thru a small orifice). Then it is a constant mass flow, regardless of the delta P increasing."

Im sure what you intended to say, was regardless of the delta P increasing due to any further downstream pressure drop for a fixed upstream pressure and temperature.

Changes in pressure or temperature, will of course still effect a change in flow rate across a choked restriction.
Hikin' Jim
(hikin_jim) - M

Locale: Los Angeles, CA, USA
Re: The Myth of Pressure Regulators on 02/21/2013 14:27:51 MST Print View

Not that there was necessarily any question as to the science, but it never hurts to have some field testing to either confirm or deny what we expect.

I posted this in the gear section, but I thought a link here might be salient for whomsoever might read this article. I took my Soto Microregulator OD-1R and a Monatauk Gnat out about a week ago for a little field testing in 31F/-0.5C weather at about 6000' elevation (~1825m). To eliminate some variables, I used 100% n-butane as my fuel. The boiling point of n-butane at 6000' is about 19F/-7C. In other words, I was testing in conditions where the ambient temperature was about 12 Fahrenheit degrees above the boiling point of my fuel.

I shot a video of the two stoves running side by side for a period of approximately 20 minutes. That video is posted on my blog: Advantages (?) of Regulator Valved Stoves, Part II. The video is in two parts, 1) the first 17 or so minutes (if you want to see the whole thing) and 2) the last 3 or so minutes (if you want to see how things turned out). For those not wanting to take the time for either video, my testing was entirely congruent with the article.

HJ
Adventures In Stoving