Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Nov 9, 2014 23:50:26 GMT -8
Peter you have suggestions about the pressure drop through the heat exchanger & throat?
I know calculations are difficult to implement and correct after testing
best regards
AG
|
|
|
|
Post by Donkey on Nov 12, 2014 8:44:21 GMT -8
@filwifi,
When your XL file is reliable, would you please e-mail it to me? I will make it freely available in the reference library here.
Thank you
|
|
|
|
Post by bernardbon on Nov 12, 2014 11:29:32 GMT -8
Peter you have suggestions about the pressure drop through the heat exchanger & throat? I know calculations are difficult to implement and correct after testing best regards AG Congratulations! This work is important for all manufacturers we are. Bernard. |
|
|
|
Post by dimitrisgr on Dec 15, 2014 7:06:08 GMT -8
Sorry but give me your guidence on this, the "port" calculation are about the size of the throat that goes in to the riser or the opening of the primari air intake in the door?
|
|
|
|
Post by byronc on Dec 15, 2014 8:57:14 GMT -8
|
|
|
|
Post by dimitrisgr on Dec 15, 2014 9:52:55 GMT -8
Yes, i have seen this thread but it wasent clear to me, thanks for the info. So the diamensions that is given on the Chart is a box that fits exacly in to the opening of the throat. And i guess the P channels diamensions is the diamendios of the tube that gives the air right? Thanks again m8. |
|
|
|
Post by toshvan on Apr 6, 2015 17:16:57 GMT -8
OK then, a given combination of 150 mm batch box, chimney and fuel type is able to yield something between 15 and 25 kW/h. An average burn will last for about an hour, including the glowing phase. Larger and denser pieces of fuel will last a bit longer. This numbers are irrespective of how much fuel is in the firebox to begin with. So half a load will take the same time as a full load, in the latter case the power delivered is roughly twice as large. The above numbers are reflecting maximum load. Peter, if I am correct to assume that half loaded firebox will result in half of a power output - how will this translate to the burn efficiency? Also related to this, how will the system size relate to burn efficiency? Am I correct to assume that 4" system is less efficient than 6" (which in turn is less efficient than 8") system? Is the draft, the air draw, affected by the size difference? Most importantly: Could you please, roughly estimate the power output of the 4" system? I think you need to chance your way of thinking about mass heaters, those are completely different from steel box stoves. Provided there's adequate mass downstream from the combustion unit, the batch box is able to charge that heat sink in a shorter span of time as compared to the J-tube. So there won't be such thing as "suffering from excess heat". Alas, but I wont be able to use thermal mass (not much of it, anyway). Stove location will be on the second level of the building, and 3-5 tons of weight simply won't comply with the statics and structural integrity (of the the building). I do want to try and use at least some mass, maybe some short and low bench even though I'm aware it won't accumulate too much heat. But in any case, I will essentially have to do without heat storage. Which means that in my case, the proper dimensioning of the stove's power output is of absolute importance. (hence my interest for estimations of the power output) |
|
|
|
Post by peterberg on Apr 7, 2015 2:46:49 GMT -8
The calculation is dead simple. Karl just mentioned a 6" would deliver around 18 kWh. What you need to know is the volume of the 6" firebox compared to the volume of a 5" or 4" firebox. The power output of those systems follow the same proportions as volume. I did that for you, a 6" volume is 30.65 liter, a 5" volume is 17.49 liter and a 4" volume is 9.09 liter.
When the largest one in this equasion is 100%, the others are 57.08% and 29.657% respectively.
Given the output of the largest is 18 kWh, the others deliver 10.27 kW/h and 5.33 kWh respectively.
Beware! These are rough estimates and the fuel size need to scale down as well.
The power output of the 8" system is 2.37 times that of the 6", following this calculation. No wonder why the batch box thingy at the innovators gathering looked like a big fat flame thrower when running full tilt.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 7, 2015 4:06:00 GMT -8
Sorry, but it is not the volume ratio, which determines the ratio of power output.
The volume may determine the amount of wood that can be placed in the box,
but not the possible combustion rate.
Regardless of 8",6",5" or 4" the temperature and thus the draft will be about the same.
As the draft is the same, the amount of delivered air and flue gas that can be carried away,
is mainly determined by the cross sectional area.
For smaller systems a larger percentage of the heat will be sucked by the material
and the boundary layer takes a larger percentage of the cross sectional area,
which will make smaller systems less efficient.
Nevertheless, the ratios of possible power output will be mainly determined by the ratios of cross sectional areas.
|
|
|
|
Post by peterberg on Apr 7, 2015 6:25:55 GMT -8
Hmmm... Karl, are you pointing at the csa of the firebox or the fuel? When filled with small cuttings the fuel will be gone much earlier, when filled with large chuncks it will take more time. So to me, it looks like the csa of the fuel is a factor to be reckoned with.
I'd agree with you about the larger percentage of boundary layer in small systems though, so bigger seems to be better.
When I would use the csa of the firebox' front the ratios would be 100%, 68.8% and 44.6%. Power delivery would be 18 kWh, 12.38 kW/h and 8.03 kWh. Compensation for the larger percentage boundary layer of 10% for the 5" and 20% for the 4" system would lead us to 18, 11.14 and 6.42 kWh respectively. Not a shocking difference with my earlier estimate, I would think.
Compensation quantity is a wild guess on my part.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 24, 2016 23:56:53 GMT -8
|
|
|
|
Post by peterberg on Oct 25, 2016 1:29:11 GMT -8
In your drawing I seem to see a burn tunnel of considerable length behind the port. The riser is placed at the end of that tunnel.
In the batchrocket design, the riser is the afterburner and placed directly behind the firebox. So there's no burn tunnel to speak of, it's just the thickness of the back wall, nothing more.
Also, the p-channel is placed very high in your drawing, resulting in a comparatevely long vertical part. This could be a restriction because the hot end will be longer, the incoming air has a longer path to resist the downwards directed stream.
By the way, it would be better to start a new thread for your design, your post is off-topic as it is now.
|
|
|
|
Post by independentenergy on Oct 25, 2016 6:56:32 GMT -8
Ciao filwifi di dove sei?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 25, 2016 8:05:51 GMT -8
Ciao
Zona Castelfranco Veneto e tu?
Mi sa che siamo abbondantemente off-topic !!! Magari inviami un m.p.
Ciao
|
|
|
|
Post by independentenergy on Oct 25, 2016 8:08:41 GMT -8
Yes
|
|
