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CharcoalRoaster
11/04/2019 1:58 AM
+1 snwcmpr

snwcmpr
11/03/2019 2:16 AM
Can we make the shoutbox UNAVAILABLE until a member has a certain number of posts?

allenb
11/01/2019 2:20 AM
Funopt, please post in the gas and electric heat sources forum

Funopt
10/30/2019 5:17 AM
Can someone help me for using forced propane burner as my heating element. I rather want to use lpg than electric. Do you think it would work

snwcmpr
10/22/2019 5:31 AM
Thanks to you all....... I was not sleeping ... I stayed awake worried about it all. :)

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Propane Flow meter for fluidbed roaster
pisanoal
Hey all,

I've been lurking on this forum for quite some time and gleaned a bunch of great info from the likes of allenb, oldgearhead etc. on fluidbed roaster design. I built a small 1 lb gas fired fluidbed roaster with a bake-a-round from these ideas and I'm now on to building a 5 lb roaster for a friend of mine.

The burner I am using is a jet propane burner capable of 100,000 BTUs, which I know is way overkill. I should be able to remove some of the jets and plug the holes if it does not have enough turn down, but so far it looks like it will.

My question is around a gas flow meter. Id like to implement something like the dwyer series vf visi-float flow meter with a needle valve (pic attached), but I'm a bit unsure on the flow range I should shoot for. I think my best two options are .6 - 5 LPM or 1-10 LPM

I did some calcs trying to wrap my head around it and id like someone to sanity check me.

Propane has around 2488 BTUs/cu. ft. There are 28.32 liters per cu. ft so that means ...

2488/28.32 = 87.85 BTUs/L

If my max flow rate I would see is 5 LPM, I would be at
87.85 * 5 = 439.27 BTUs/min or 26,356 BTUs/hr
Min would be 87.85 * .6 * 60= 3,162.6 BTUs/hr
(I assume burner BTU ratings are in BTUs/hr, someone please correct me if I'm wrong). This seems at the right range, but I could see maybe going above the top end?

Alternatively the larger range
Max Reading = 52,710
Min Reading = 5,250

My concern about the larger range is having enough resolution to be useful, and being low enough BTUs for end of roast.

Thanks!
pisanoal attached the following image:
flowmeter_small.jpg
 
allenb
Hi and big welcome to HRO! Your calcs look good to me for the 5 lb fluidbed. I had come up with around 7.5kw for a 5lb fluidbed which comes out to around 25,500 btus/hr and just under 5 LPM (propane) so I would go for the .6-5 LPM meter and should do fine. I didn't realize they made a flowmeter with needle valve in one package. That sounds like a great option.

Keep us updated on how this turns out.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
pisanoal
Thanks!

I looked at the specs on the flowmeter and the one thing i didnt think about was the fact that it is tuned for air. That means in order to get flow of a gas with a different specific gravity you need to multiply the flow rate by the square root of 1 divided by the SG of your gas Q2=Q1*sqrt(1/SG). The SG of propane is 1.50. It works out that the flows for propane are about 82% of the flows for air. So with that i think I'll actually go with the 1-10. They have a 4 inch option which will help with my resolution concerns, and the fact that the flows are 80% of the reading means my low range is equal to lower btus, so that mitigates that concern too. It also means im closer to going over the top end of the 5 lpm.
 
allenb
I had noticed the .6-5 lpm only comes in 2" scale, which to me would be tough to read with any precision. The 1-10 does seem to be the better option and looks like it would be the VFB-66-BV?

FYI, they will do a custom scale if requested but I don't know what this would add to the cost.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
renatoa
A bit puzzled... all roasters I seen so far are controlling their burners with an eye on a pressure meter... how would the things change based on flow ?
 
allenb
No change that I know of. Whether it be a display of flow or pressure, the end result is an indicator of heat energy level going into the roast so one can maintain their desired rate of rise at the various stages of a roast.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
pisanoal
allenb wrote:

I had noticed the .6-5 lpm only comes in 2" scale, which to me would be tough to read with any precision. The 1-10 does seem to be the better option and looks like it would be the VFB-66-BV?

FYI, they will do a custom scale if requested but I don't know what this would add to the cost.


Yeah. Not sure what the custom range would cost. I went ahead and ordered the 66-BV. I really like that the needle valve supposedly controls well throughout the whole flow range. I'll be sure to post back with the result. Shipping was $9 so $71 for flow meter and good quality needle valve is a pretty good price.
 
pisanoal
allenb wrote:

No change that I know of. Whether it be a display of flow or pressure, the end result is an indicator of heat energy level going into the roast so one can maintain their desired rate of rise at the various stages of a roast.


Agreed. It was easier for me to figure out flow for the BTUs i was expecting. Pressure is more of a case by case depending on piping configuration among other things.

There are advantages and disadvantages to both I suppose.
 
renatoa
allenb wrote:

No change that I know of. Whether it be a display of flow or pressure, the end result is an indicator of heat energy level going into the roast so one can maintain their desired rate of rise at the various stages of a roast.


Flow is a function of pressure and speed... so using pressure as an energy indicator we should rely on the (unknown) fact that gas speed is constant. Is this a sure thing ?
Asking because a friend roaster has a very weak source of gas supply, the heat varying wildly every tank, even if using same pressure.
So the only thing to blame would be the gas composition, that led to variable speed ? Could a flowmeter instead pressure improve his heat control ?
 
pisanoal
renatoa wrote:

allenb wrote:

No change that I know of. Whether it be a display of flow or pressure, the end result is an indicator of heat energy level going into the roast so one can maintain their desired rate of rise at the various stages of a roast.


Flow is a function of pressure and speed... so using pressure as an energy indicator we should rely on the (unknown) fact that gas speed is constant. Is this a sure thing ?
Asking because a friend roaster has a very weak source of gas supply, the heat varying wildly every tank, even if using same pressure.
So the only thing to blame would be the gas composition, that led to variable speed ? Could a flowmeter instead pressure improve his heat control ?


This is one concern I had as well. Same pressure doesnt always mean same flow, although I would think it would be close enough unless something changed in the layout of tbe machine. It also depends on where your control valve is. If you have Cv-gauge-burner I would say it would likely be pretty darn consistent. If its Pressure gauge-Cv- burner then probably not.

Why do you think the gas composition is changing? If it changes enough, that could have a large impact on BTU value. So he may be getting the same amount of gas, but the gas isnt providing the same amount of heat. Also, the specific gravity of the gas has an effect on flow, so if that is changing enough, flow measurements might be off too.

If its just velocity that is changing because of how the system is set up (maybe varuijg supply pressures/piping setup), then a flowmeter instead of preasure would definitely help as flow is conserved.
 
allenb
So the only thing to blame would be the gas composition, that led to variable speed ? Could a flowmeter instead pressure improve his heat control ?


It's interesting that the propane being delivered to your friend varies in BTU content. I know that commercial grade propane has a lower caloric value than consumer grade but I don't know how any supplier could stay in business if a specific grade of propane varied more than a tiny percent as it would require that equipment be recalibrated or adjusted constantly.
In this particular situation, I don't see how measuring flow versus pressure would improve the ability to control things.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
pisanoal
So I actually already recieved the 1-10 lpm flow meter and this thing is awesome. The needle valve allows for very precise conteol throughout the range measured. I'll post a link to a video showing the control range. Gas regulator is set at 2 psi.

I moved the needle valve pretty aggressively throughout most of the video but I do show some fine controls briefly. Id say it could be controlled to the .1 lpm although resolution is not that good. Hash marks are .5 lpm, so a decent amount of interpolation is possible.

Id say a really good option for anyone looking to do a new build.

 
CoffeeInterest
This is a great looking way to control the BTU.

How does the jet torch stand up to the forced air? Do all the tips stay lit?
 
allenb
I am totally impressed by your find and how well it dials in the flame output with precision control. If you don't mind, when you have a moment, if you could post a thread under "electric and gas heat sources" within "building a roaster" with a brief description of the meter/needle valve unit and your video, it would be a great resource for folks looking for gas control options.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
pisanoal
CoffeeInterest wrote:

This is a great looking way to control the BTU.

How does the jet torch stand up to the forced air? Do all the tips stay lit?


I haven't gotten that far yet. I just welded up the firebox section of the roaster.

I did blow on the burners and was able to put a few of them out by blowing pretty hard. My inclination is its going to be pretty hard to blow out under our circumstances.

If that becomes an issue, a simple air diffuser or deflector would be sufficient to direct the velocity away.
 
pisanoal
allenb wrote:

I am totally impressed by your find and how well it dials in the flame output with precision control. If you don't mind, when you have a moment, if you could post a thread under "electric and gas heat sources" within "building a roaster" with a brief description of the meter/needle valve unit and your video, it would be a great resource for folks looking for gas control options.


For sure. Ill definitely put something in there.
 
pisanoal
CoffeeInterest wrote:

This is a great looking way to control the BTU.

How does the jet torch stand up to the forced air? Do all the tips stay lit?


Ive gotten to the point where i could test this. It didnt do great at first for me, but the burner is only 6 inches from the air inlet. After I made a diffuser, I'm able to turn it down quite a bit without the tips blowing out.

It struggles more then my smaller roaster, but that one is a camp stove that has a built in windscreen.
 
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