I wonder what would be the effect of a proper airstreamed venturi port.
I mean the back of the firebox would be rounded in a shape which would concentrate the flames on the port, then the port sides would be shaped properly for the air to flow as best as it can; and the gasses expansion after that would suck what's on the firebox side.
I won't try, i have no means of testing nor the time. But it would be cool to know.
And may be a longer port, i mean, narrow, venturi shaped, to concentrate all the flames in a little area, insulated like mad.
Technicaly the rapid expansion of gasses after a venturi is what creates the suction effect. like, increasing the flow of compressed air.
I've tried smaller and wider ports as well, results were not as good. So yes, the constant could be 72.36% but the question of why isn't answered.
Tantalizing, don't you think?
Yes, quite. Peter, you know more about this than I do.. Where else in the stove world do we see ratios like this? Is there some corollary to another type of stove? Something well known.. ? Perhaps a connection can be inferred somewhere. ?
@donkey, To my knowledge, nowhere in the stove world is something like this known, sorry. During all these years of digging through stove information I've never come across a constant, let alone this particular one.
@max, Shaping the firebox to optimize the venturi effect could lead to a less usable fire box. Maybe I could try a shaped port, sometime in the years ahead...
Very interesting. Since you seem to be the one who's knowledgable, what radius at the port entrance would you recommend? And what is the hydraulic diameter of a port of say, 240 x 54 mm?
The radius should be as big as feasible. At a given widh the height of the port influences the flow velocity in the port, which depends on the velocity before the port and the CSA ratio of box and port. I think the height of the port will influence the head loss mainly by the flow velocity, which is neglible by a radius to diameter ratio > 0.25. A ratio of 0.4 could be used for safety. 54 mm x 0.25 = 13.5 mm. 54 mm x 0.4 = 21.6 mm. I would recommend a radius of 15-20 mm.
OK, I've recalculated the rectangle of 240 x 54 mm to a circle of 128.45694 mm or 0.1284569 m diameter. Inserting this dia in the Thermal Wizard, flow velocity of 2 meter/sec. and a minimum of 0.03 m for the bellmouth radius, this would result in a Head Loss Coefficient of 0. Anything smaller radius would result in a slight loss.
On the other hand, only counting the sides of the port to be rounded off, this sides combined could be seen as the circumference of a circle with a diameter of 0.1527888 m. Using a radius of 0.04 m, this would result in no loss again.
This Thermal Wizard is maybe not fit for calculating a rectangle duct, I don't know.
Alright, maybe someone who's gearing up for the Woodstove Design Challenge could use this!
Karl, Peter, i was thinking about the airfoil shape you see in some high end carburetors. Tho, not having seen one for a fair while, i can't remember if it's normal a normal airfoil or a reversed one. I have seen a flame in such a venturi, gas flame, which created a horendous amount of suction. The gas jet has to be placed perfectly to create the best suction, it was like a ramjet of some kind but meant for sucking air or throwing flames. Can't remember exactly. Had a light thrust, but it had thrust. If we could implement that effect into a rocket, that would be mad I'm imagining this in the burn tunel of a J tube. I've been searching images for a while. But can't seem to find a rendering of this.
where: Q = stack effect draft (draught in British English) flow rate, m³/s A = flow area, m² C = discharge coefficient (usually taken to be from 0.65 to 0.70) g = gravitational acceleration, 9.81 m/s² h = height or distance, m Ti = average inside temperature, K To = outside air temperature, K
U.S. customary units:
where: Q = stack effect draft flow rate, ft³/s A = area, ft² C = discharge coefficient (usually taken to be from 0.65 to 0.70) g = gravitational acceleration, 32.17 ft/s² h = height or distance, ft Ti = average inside temperature, °R To = outside air temperature, °R
This equation assumes that the resistance to the draft flow is similar to the resistance of flow through an orifice characterized by a discharge coefficient C.
Notice that there IS a constant here AND it's in the "ballpark" of our 72% -- discharge coefficient.
I'm not sure how (or even if) this relates, though it FEELS at least close to the right direction for further inquiry.
In a nozzle or other constriction, the discharge coefficient (also known as coefficient of discharge) is the ratio of the actual discharge to the theoretical discharge, i.e., the ratio of the mass flow rate at the discharge end of the nozzle to that of an ideal nozzle which expands an identical working fluid from the same initial conditions to the same exit pressures.
Where exactly should the port sit in terms of height relative to the batch box? Should the top of the port sit level with the top of the batch box, or bottom of port level with bottom of batch box, or somewhere in between?
mercedes: Not sure where this question will end up...I just registered. HOW THICK SHOULD PERLITE/VERMICULATE/CLAY INSULATION BE BEHIND THE THERMAL BATTERY/COB BENCH IF IT BACKS UP TO A STRAW BALE WALL? Thanks! Can you please also post me: firstname.lastname@example.org thnx!!
May 28, 2018 20:05:23 GMT -8
kkp: Mercedes: Benches don't get real hot. In fact, they are rather cool compared to other areas. You shouldn't need a mix like you described
Jun 7, 2018 18:10:52 GMT -8
maartenmartens: beste Peter, ik heb je eergisteren een mail gestuurd via het contact formulier op je website , heb je die goed ontvangen ? mvg Maarten Martens, architect - geobioloog (mail betreffende de bouw van onze eigen RMH)
Jun 20, 2018 13:21:57 GMT -8
martinm: any one here with info \ experience with heat (from a mass heater) distribution with ducts throughout two storey house ?
Sept 8, 2018 22:58:52 GMT -8
padica: Good morning, this is a wonderful subject, please someone can help me with the theme of double and triple combustion, how it is achieved, theory and design, thank you
Sept 15, 2018 7:13:40 GMT -8
wiscojames: I'm afraid you won't get a response to such a vague question - I suggest reading through some of the threads related to your questions before asking for an explanation. People will be very generous with their knowledge if your question is more specific.
Sept 18, 2018 4:48:00 GMT -8
daniel: in my experience as I am working now on something of that nature, I have thought of making a heat exchanger and distributing the heat through vents using a slower fan. Now after a few years I realize that mass heaters give out primarily radiant heat, for
Nov 30, 2018 12:48:38 GMT -8
coastalrocketeer: Anyone posting in this shout box... if you have something you want people to see and respond to, create a thread in the appropriate forum section... this is not the place...
Dec 16, 2018 18:10:49 GMT -8
vesuvius: High Temperature Glass options,
Jan 4, 2019 16:28:17 GMT -8
vesuvius: Do any of you have experience with using the glass from home oven doors on a rocket stove? I'd like to have a viewing port on my stove but don't want to fork out for new ceramic glass. Any thought as to whether it would take the heat of a rocket stove?
Jan 4, 2019 16:30:40 GMT -8
yaya: you dont need the blowair for that temp..
Jan 13, 2019 16:43:57 GMT -8
flybywire: Glass window from an old washing machine is designed to take high temps. Cheap solution to your need.
Jan 27, 2019 0:10:58 GMT -8
coastalrocketeer: Anyone posting in this shout box... if you have something you want people to see and respond to, create a thread in the appropriate forum section... this is not the place to have a discussion... it is for short announcements
Feb 7, 2019 0:11:23 GMT -8
coastalrocketeer: you won’t likely get replies to questions here, and it is not a spot that makes holding an ongoing discussion possible...
Feb 7, 2019 0:12:22 GMT -8
TexasGonzo: Sooooo glad I found this site! Its always rewarding to find such a super group of folks! To any and all, feel free to PM me anytime. Thanks for having me!
Mar 11, 2019 18:56:41 GMT -8
jlmtech: GADGET: CONSIDER USING A JET PUMP INSTEAD OF A BLOWER FAN TO INDUCE DRAFT; NO CLOGGING.
Mar 26, 2019 8:19:28 GMT -8
michaelegan: i am unable to open the sketchup files on my mac. I used sketchup a few years back but apparently the company now requires a subscription. does anyone have any advice/instructions on how to use the program or how to view pictures without spending money?
Aug 20, 2019 18:41:48 GMT -8
mannytheseacow: michaelegan: download AutoCAD student version for free... import .SKP
Aug 23, 2019 13:33:44 GMT -8