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Homeroasters - Home Roasting Coffee Community » BUILDING A ROASTER » Fluidbed Roaster

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Page 2 of 2: 12

Rotational Axis Roaster
allenb	#26 Posted on 02/27/2010 8:56 PM
Administrator Posts: 3858 Joined: February 23, 2010	I tried to attach the patent file for the Rotational Axis Roaster but its a PDF so it didn't save. If you look up the patent application shown in my previous post and bring it up in Free Patents Online you can view the patent application with drawings included. Looks real interesting. It also looks like he doesn't use exhaust recirc if I'm seeing it correctly. Cheers 1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana


klemenv	#27 Posted on 02/28/2010 8:56 AM
Newbie Posts: 11 Joined: February 17, 2010	Thanks for the patent link. There is calculation regarding CFM in Downloads area. Does anybody have a clue, what is the unit for pressure called "inWS"? I am trying to Google it, but I can't find anything. I guess required CFM for 1Kg would be around 100, so I guess requirement for buble bed would be ~500 CFM.


allenb	#28 Posted on 02/28/2010 12:07 PM
Administrator Posts: 3858 Joined: February 23, 2010	Excerpt from patent by James P Mahlmann patent # 4501761 The bubbling bed is formed by suspending the greater mass of coffee beans in a large volume of upwardly flowing roasting atmosphere. One difference between conventional static bed roasting and bubbling bed roasting is shown by the weight ratio of roasting atmosphere to coffee beans, the so-called air to bean ratio. In a typical drum commercial coffee roaster, the air to bean ratio is about 1.0 kg air (roasting atmosphere)/1.0 kg roasting coffee beans. The air to bean ratio of the present method though, is preferably from 40.0 to 150.0 kg air/1.0 kg coffee beans. With the high air to bean ratio, the individual coffee beans are surrounded by an "envelope" of roasting atmosphere, contributing to the uniformity of the roasted coffee. The air to bean ratio for a fluidized bed is between 10.0 and 30.0 kg air/1.0 kg coffee beans. The inlet velocity of the roasting atmosphere needed to maintain a bubbling bed is also intermediate between the velocity in a drum roaster and the roasting atmosphere velocity in a fluidized bed roaster. In a bubbling bed roaster, the velocity is on the order of 670 m/min to 1250 m/min compared to between 40 m/min and 46 m/min for a drum roaster and on the order of 3660 m/min for fluidized bed roasting. As is apparent, the maintenance of the bubbling bed as compared to a fluidized bed differs primarily in the inlet velocity of the roasting atmosphere I can't tell you how to convert kg air to cfm but if you can figure it out you might have a starting point. Another angle would be to take his (670-1250 meters/min) and convert it to feet/min then with knowing your surface area of the roast chamber you could probably come up with cfm. I'm hoping the cfm turns out to be less than 500 as this is a heck of lot of air. WS is a German abbreviation for water column. Cheers 1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana


endlesscycles	#29 Posted on 02/28/2010 1:56 PM
Pounder Posts: 420 Joined: April 11, 2009	Pressure lofts beans, CFM runs away with heat. CFM and BTU are linearly related for a given ET. Perforation distribution can be optimized. Obviously 100% lofted requires more CFM for a given bean bed depth. Bed depth is an independent design parameter to bean mass. length and width are variable for a given design, not depth. This looks like an air hockey table with engineered high loft zones. -Marshall Hance Asheville, NC


allenb	#30 Posted on 02/28/2010 10:02 PM
Administrator Posts: 3858 Joined: February 23, 2010	Good points on bean bed depth/lift. I know this can probably be engineered up to a point by someone who has the math down pat but I thnk for most of us we just have to take a stab at it and modify as we go. I'd bet you could get away with closer to 250 cfm and still get the lift needed. The trick will be figuring out what static pressure will be needed and total open area square inches on the perf plate so you maintain a positive pressure below the plate. In looking more into whats going on in a bubble bed using a perf plate it turns out there is an acutal mini spouting plume at each location on the plate where you have the higher density hole count. You still have air flow in the areas of low density hole count but just enough to get the "air hockey table" effect. This allows the beans not in the plumes to easlily slide towards the plumes. Facinating technology! Here's the video of Nepro's demo bubble bed showing spout areas: http://www.nepro....hneAni.gif 1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana


seedlings	#31 Posted on 03/01/2010 8:00 AM
1 1/2 Pounder Posts: 4226 Joined: June 27, 2007	I'd like to see a handful of marked beans in there to watch the circulation! CHAD Roaster: CoffeeAir II 2# DIY air roaster Grinder: Vintage Grindmaster 500 Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover


allenb	#32 Posted on 03/01/2010 8:55 PM
Administrator Posts: 3858 Joined: February 23, 2010	That would be a fun experiment to watch. In fact, I'm almost tempted to build one myself just to see that action. I've been trying to come up with a viable method of dumping the roaster. With a cone bottom or rectangular "V" it's not hard to do but with a flat bottom perf plate I'm not quite certain how one would attack this. The only way I've come up with is to hinge the plate at one point and drop at the opposite end which would require the plate to come up against a slightly smaller diameter ring when fully horizontal in the up position. This is hard to describe without visual props I know. In looking at the beans dumping on the Nepro it appears the beans are flowing out to one side which made me think of a hinged perf plate. I'm going to attempt to attach a sketch of a possible perf plate hole arrangement on an 8" dia plate with some patent info included on hole spacing. If it does'nt come through I'll try again on another post. Allen allenb attached the following image: 1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana


seedlings	#33 Posted on 03/01/2010 9:28 PM
1 1/2 Pounder Posts: 4226 Joined: June 27, 2007	Is this design supposed to have a more efficient heat transfer, requiring less wattage than a "standard" Sivetz-type roaster? I seem to remember some verbiage suggesting it was not. CHAD Roaster: CoffeeAir II 2# DIY air roaster Grinder: Vintage Grindmaster 500 Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover


endlesscycles	#34 Posted on 03/02/2010 8:45 AM
Pounder Posts: 420 Joined: April 11, 2009	What fan / motor can provide pressure and handle 450F? -Marshall Hance Asheville, NC


seedlings	#35 Posted on 03/02/2010 9:25 AM
1 1/2 Pounder Posts: 4226 Joined: June 27, 2007	I have one steel enclosure with aluminum radial fan blade. But there's a catch: http://forum.home...#post_9909 In order to use it with HOT inlet air is to either: shorten the life of the motor or use a pulley system like Sivetz uses. Beginning at :24 in this video, watch the lower, left corner to see the pulley driving the fan... the heat comes in from burner on the opposite side inlet: http://www.youtub...cyhPwpoIKw CHAD Roaster: CoffeeAir II 2# DIY air roaster Grinder: Vintage Grindmaster 500 Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover


allenb	#36 Posted on 03/02/2010 10:51 PM
Administrator Posts: 3858 Joined: February 23, 2010	Quote Is this design supposed to have a more efficient heat transfer, requiring less wattage than a "standard" Sivetz-type roaster? I seem to remember some verbiage suggesting it was not. CHAD I'm not aware that a bubble bed affords a higher heat transfer efficiency than spouted bed. The difference is that all or most of the beans are absorbing convective heat all at the same time so the spread between bean temp and environment temp can be much smaller equating to a reduced environment temp from start to finish of a roast. For an analogy lets say you had a 1kg standard fluid bed with normal spouting bean movement and your air was at 480 F. Now snap your fingers and you take the same batch of coffee and spread the beans into 5 or 6 mini spouts each getting the same 480 F air but add the ability to have air flowing (at a slower velocity) in between each spouting area. In this scenario the degrees per minute is going to speed up drastically unless something changes. That change has to be a reduction in environment temp. What is difficult for me to get my hands around is whether the increased air volume with decreased temperature is going to transfer as much of its BTU's passing through the coffee bed as with a standard fluid bed. If the answer is no then our efficiency will have dropped. The big question that comes up is does an increase in air flow and decrease in temperature cancel each other out making a bubble bed use no more BTU's/hr than a standard fluid bed? For a gas fired option the fan issue is a bugger as you mentioned needing to either have an extended length shaft with slinger or belt drive with/without slinger. Going electric with nichrome might be a simpler option if you have the 220 for the 5 or so KW needed. Allen 1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana

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