Propane burner starting efficiency

[drinktofabfabtodrink]

Hello all,

doing a bit of research for a project. with my newly built 3" bok on a 15.5gal stainless keg i am heating with a propane burner. i have the propane tank suspended by a load cell and i am recording weight of propane used every little while. i am collecting lots of data, but right now am focusing on start up efficiency... start up being bringing mash to boiling temps. knowing how much mash at what alcohol level i can do a little math (Q = McdT) to find how much energy it SHOULD take to bring to temperature, and then using my data how much energy i ACTUALLY used to bring it to temp. pot is not insulated (plan to do this later) but going through my numbers right now.. looking pretty poor.

have a spreadsheet with the numbers, but looks like each run is around 10% efficient... using 10 times more energy than i should need to...

anyone ever done something similar? any hard numbers? hoping my load cell is off... because that seems LOW!!!


happy stilling

[Truckinbutch]

No hard data to give you , just a lot of time spent playing with fire . Haven't installed it yet but i plan to put a heat shroud around my boiler to increase efficiency . Until then I am using a mid range burn to get up to speed . Opening the fire to full bore was blowing too much heat past the boiler sides and into my shop .

[Maritimer]

Hi drink,

Do you mind posting your speadsheet? You'll have to change the .xls or whatever to something that the forum uses, like .pdf. Then when it's downloaded we can change it back to .xls.

M

[okie]

If you don't mind, tell what brand burner and the output. Please.

[drinktofabfabtodrink]

here is the spread sheet, it was a bit of a quick check type sheet, checked it once i think, but please dont be afraid to point out errors or questions if it is wrong

Heat for start up worksheet (version 3).pdf

(35.18 KiB) Downloaded 94 times

*found a mistake. numbers look a little better now with version 3 *

so just change that format back to excel, believe it is .xlsx (its microsoft excel.)

burner i am using is a Camp Chef expedition 3x, BTU/Hr rating is 3 @ 30k. Model no. TB-90LW 07. only using the center burner when i run.
found something really similar on google images (minus the fancy towel rack and such)

here is an example of the spreadsheet with the data i collected. It is a bit messy, not ment to be a template, just to see how i am going about my data collection.

Trial 1 with U.J. (version 1).pdf

(37.51 KiB) Downloaded 101 times

[Maritimer]

Hi drink,

OK, got it working.

M

[VAChemE]

Hello all,

doing a bit of research for a project. with my newly built 3" bok on a 15.5gal stainless keg i am heating with a propane burner. i have the propane tank suspended by a load cell and i am recording weight of propane used every little while. i am collecting lots of data, but right now am focusing on start up efficiency... start up being bringing mash to boiling temps. knowing how much mash at what alcohol level i can do a little math (Q = McdT) to find how much energy it SHOULD take to bring to temperature, and then using my data how much energy i ACTUALLY used to bring it to temp. pot is not insulated (plan to do this later) but going through my numbers right now.. looking pretty poor.

have a spreadsheet with the numbers, but looks like each run is around 10% efficient... using 10 times more energy than i should need to...

anyone ever done something similar? any hard numbers? hoping my load cell is off... because that seems LOW!!!


happy stilling

Greetings,
The efficiency value that you claim to have received is likely to be slightly greater than the actual efficiency of your system as you have described it. To start, Q=mCdT is an idealistic thermal requirement of your process fluid which is established on the basis that the heat exchanging medium is perfectly insulated. Based on the image you provided as a reference for your heating element, it is evident to me that much of your potential to supply thermal energy from propane combustion is lost to the environment. Ideally, the heat source and the heating medium should be established relative to one another in a manner that prevents loss during thermal conduction. By this I mean that the regions surrounding the flame and the fluid-vessel should be encompassed by a barrier that concentrates/focuses conduction to the vessel. Furthermore, stainless steel has a lower thermal conductivity than alternative materials commonly used for boilers. Hence, the use of a material with a higher thermal conductivity would minimize energetic losses during the operation of your process. While I am not certain as to the extent with which you have employed an energy balance for your process, it would behoove you to include the ambient conditions (surrounding the regions of your heat loss) in your calculations. Upon implementing thermal insulation around the boiler and other sections in my process, it became qualitatively obvious that heat loss through conduction to the environment greatly limits one's ability to perform controlled distillation (paired with quantitative models). As far as what insulation to use, I have utilized a rolled insulation that has a grey/soft adhesive side and a silvery/metallic side (which faces outward once installed). I secured this insulation further with metal foil tape used for duct-work. On top of this I secure a blue plasticized rolled insulation with more foil tape. All of these items can be found at Lowe's in/around the insulation isle.
For further quantitative modeling endeavors, you will find that this step is essential. Once you reduce your inefficiencies to a minimum, it becomes possible to obtain heat capacity data that more closely characterizes your process fluids. Regression analyses of thermodynamic quantities become more useful as your system approaches feasible correlation to the mathematical model chosen to quantify the status of your fluid.

Prost,
VAChemE

[rad14701]

Hint To All

Rather than saving files as PDF's, requiring a file extension change, a better method would be to zip the XLS file which can then be extracted on the end users PC... Zip uploads are allowed...

[F6Hawk]

Assuming thermal loss is the same for electricity vs. propane (but obviously it's not), and assuming $3.50 per gallon of propane and $0.21 per KwH for electricity, and assuming 3.41 watts per BTU as a factor... your cost to run that still was about $1.72, whereas electricity would have cost $2.77.

I'm sure the electric cost would actually be lower, due to increased efficiency in the wash, so it's not exactly comparing apples to apples. But I still think electricity is more expensive on average to use, with those prices above. (I actually pay less per gallon than $3.50, so my cost to run would have been $1.57).

Now we need someone to do the same thing using an electric keg. You also didn't mention the time it took in your calculations.

[drinktofabfabtodrink]

VAChem - Yes, I agree with you on everything you said. I realize that the method i am using to heat my still is inefficient - no insulation ect ect... but rather than approach a theoretic exactness while i run my still, i just want some ball park numbers what its taking me to run. using a perfect theoretical model (Q=mcdT) is a base line that makes a comparison possible from mash to mash and size of run to another. i know that insulating will increase my efficiency, but i also know that on the small scale that i am running the extra propane i use is a matter of quarters... one of my main goals by looking at propane use was to see how inefficient it is, and will the hassle of putting up insulation and looking like a meth cooker in my back yard be worth the dollar i save from insulating (not to mention the cost of insulating).

so i agree with you 100%, but i want to keep this experiment simple and practical, which is why i started off testing on the most inefficient method of running, because its how i normally set up.

F6 - There is time on that sheet, however it shouldnt matter for calculations how much time passed, because i have the total weight of propane recorded. time will help me get flowrates, whether i was blasting it with heat or bringing it slowly to temp. i have actually done a range in my testing, going from blasting all the way through (stripping run) to running very very slow...painfully slow... so far it looks like going slow is good to a certain extent, less heat escaping from the sides (since im using stainless not copper) but if you factor in time, so far it looks like blasting it at first and then running slow was the best bang for you buck in terms of propane.. and taste for that matter..