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Post by wrekinwanderer on Feb 23, 2014 12:49:57 GMT -8
Hi Ronyon, been having a bit of an internet break - ahhhhh.
My system uses a shower pump to boost the low flow of the hot water coming out of the tank due to the not very high header tank. This gives me a nicely pressured shower and our huge family bath fills up much faster!
Although my system is a little different as there is a thermosyphon loop from the heat exchanger which goes into an insulated open vented hot water cylinder. While it may be a less efficient, being indirect, than Donkey's excellent direct system, I chose this way as I felt the water would then stay hot longer...
It's based on a 4" batchbox, tied to a 100litre storage cylinder. One load provides piping hot shower from cold.
2tranceform - certainly much lower than copper, but it's used in solar thermal applications. Just checking "thermally conductive silicon tubing" advertised, although without the appropriate W/(m.K) - wait here's one 0.8! Streuth, so only 500 times less than copper! And just looking at prices, not necessarily that much cheaper too. Hmmm looks like I will be bending copper for that long awaited apple juice pasteuriser...
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Post by thendon on Feb 23, 2014 15:19:25 GMT -8
Fluid Transmission Surface Fluid Overall Heat Transmission Coefficient (Btu/ft2 hr oF) (W/m2 K) Water Mild Steel Water 60 - 70 340 - 400 I found this data, I have no idea how to interpret it but someone else might. Being European... I use the W/m2 K this tells us the energy that will be transfered (W) through a given area (m2) for every degree Kelvin (K) difference between one side of the material and the other. 1 Kelvin is the same interval as 1 Degree C. Kelvin just starts from absolute zero. so to give a worked example... a surface area of 1m2 with a delta T (differential of temperature) of 40K would give us anywhere from 40*340=13600W (or 13.6kW) to 40*400=16000W (or 16kW) to convert kW to Btu, times kW by 3414. hope that helps. Thendon Jones. |
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Post by kpolano on May 26, 2014 12:00:47 GMT -8
Donkey
how are you moving the hot water to point of use?
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Post by Donkey on Jun 19, 2014 23:41:41 GMT -8
I've done a little testing of this idea. This coil is made with about 49 feet of 3/8 inch, soft copper pipe.  Here, I set it in a pot of water on a propane stove and let it boil for some time. No problems.  |
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Post by Donkey on Jun 19, 2014 23:51:02 GMT -8
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Post by matthewwalker on Jun 20, 2014 6:54:00 GMT -8
Nice one Donkey.
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Post by morgan on Jul 1, 2014 19:54:59 GMT -8
Hi all, I'm new to this forum and only just recently discovered the concept of rocket mass heaters. I had made an impulse purchase of a 100 gallon stocktank at my local Costco, deciding on the spot that I would make it into a hot tub. I never could have imagined the can o' worms that that impulse would open! My path to discovering RMH's began when I googled 'hot tub heating alternatives'. My first result was the Chofu wood fired heater, which I thought was really good looking but comes with too big a price tag. So then I decided to look into DIY approaches, which lead me here. I'm thoroughly fascinated by what I've seen and read so far but I'm concerned that this little project may be beyond my engineering capabilities. I realize it's a great opportunity to learn some new skills like welding, masonry, cob construction, and sheet metal fabrication though. On the other hand I'm not sure how much time and effort I want to put into the pursuit of a hot soak after a hard day of work/play. There's also this local ordinance to consider:
"Can I have a fire pit in my yard? At this time, there is a No Open Burning policy in place in the city limits of South Lake Tahoe. Even if your pit is the metal or mesh kind that you can purchase at the store and even if it has a metal lid, you may not use them in the city limits at this time. BBQs are acceptable, as long as you are cooking food with them".
I live in the front unit of a duplex with a small yard facing a lightly traveled road. My intention is to have the tub and heater off to the side of the yard behind a bamboo or wicker type screen. If anyone can advise me on the legality, and feasibility, of building a rocket stove hot tub heater in my front yard I'd greatly appreciate it. Also, I'd be most grateful if someone would show me plans that strike a balance between efficiency and simplicity of implementation. At any rate, I'm really excited about these innovations in wood fired heating, cooking, etcetera. I think it'll be fun to ,at the very least, build a small cinder block rocket stove for camping. It seems like a logical progression from the beer can stoves I recently learned about and have successfully made.
Thanks!!
Morgan.
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Post by ericvw on Jul 2, 2014 17:11:35 GMT -8
Hi Morgan,
Tell anyone interested enough to ask that you're bbq-ing water!
I've not read up enough on Donkey's water heating ideas, but am plenty interested, seeing as my brother was employed as a hydronic engineer for some time in the late 90's-2000's. Radiant floor heating and such... He's since moved on, but the idea of heating water with a rocket stove for domestic (al beit, hot tubbing in your case!) use is intriguing.
Keep up the fight!
Eric VW
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Post by morgan on Jul 7, 2014 18:54:35 GMT -8
Thanks Eric, will do. Maybe I'll try replicating Donkey's hot water heater plans with a 30 gallon barrel
Cheers!
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adiel
Junior Member
Posts: 119
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Post by adiel on Jul 13, 2014 6:06:44 GMT -8
hey
maybe it's my english but i dont get it. if the coil is closed how is the pressure is not getting build up inside it?
looks amazing anyway
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Post by peterberg on Jul 13, 2014 6:43:25 GMT -8
Definition is simple, really.
The water around the coil is free to the air and boils, 100 degrees Celsius. This water isn't able to get any hotter than that since it is open to the atmosphere. The water in the coil is under pressure by the main water supply so it do need to get hotter than 100 degrees to boil, let's say 120. But it will never get there because of the limited temperature of the water around it.
In short: the water in the coil won't get to steam so it won't boom. The dangerous point is that of phase change, where the liquid changes to gaseous.
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adiel
Junior Member
Posts: 119
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Post by adiel on Jul 14, 2014 2:05:19 GMT -8
ok
But doesnt the water surrounding the coil run out?
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Post by peterberg on Jul 14, 2014 2:46:33 GMT -8
In the setup Donkey tried, it will. The coil won't be heated anymore when that's the case so the water will be coming out cold. Heating a dry pot will destroy the latter but that's all. Usual solution is installing a mechanism borrowed from a flush toilet, so the water will be topped up at the same pace as it evaporates.
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Post by satamax on Jul 14, 2014 3:00:24 GMT -8
I'm wondering about two points about this type of system.
Where do you vent the "boiler" inside the house? Or outside?
And, ok, the water is hot in the coil, then you draw water, but does the incoming water has time to heat up enough when passing through the coil?
I'm just wondering how adapted this would be to shower.
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Deleted
Deleted Member
Posts: 0
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Post by Deleted on Jul 14, 2014 3:50:25 GMT -8
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