Good afternoon everyone.
I'm new to the site, but there seems to be quite a bit of knowledgeable people here. I was hoping to get some pointers on a project I'm working on.
I have a small, two room cabin that I am trying to heat. I built this out of 8' landscaping timbers to give you an idea of the scale. There are two 8' square cabins connected by an 8' dog trot. I have a couple of heater cores like you'd get out of a central unit on your house. I thought about running hot water through these using s thermosiphon system ran off a j-style, poured "concrete" rocket heater that I saw online.
The design was simple enough, but since its a solid pour, I need to hammer out all the details before hand. I have a few sections of 10" stove pipe I thought to use as a stack. I figure I can wrap 1/2" or so copper tubing around the stack before I pour so it will be set in place. The burn chamber I figured I could construct a square framework. I think the mass of the "concrete" will hold heat to give me a nice warm fireplace, and also heat the tubes enough to get a strong supply of hot water to my radiators.
Here's where my questions come in. I've never done ANY of these things. I understand the concepts of all of it, but are there any certain EXACT ratios that need to be followed?
For instance, I'd like the capability of a long burn so you could start it before bed and it would stay going, or at least warm until morning. So can the "j" portion, for wood feed, be taller to accept longer kindling and it not effect efficiency? With a 10" exhaust stack, is there a particilar size that the burn chamber needs to be? I fired 10" all the way through but I honestly don't know.
On the water heating part. I know that hot water will rise and create a flow, but if the entire system is basically a loop of 1/2" copper tube, appox. 30' long...will that circulate? I worry that the radiators won't draw enough heat and the water temp will equalize in the tube. This would be fine as far as a heating stand point, but if it gets too hot and turns to steam...I just worry lol.
Anyway, I could go on all day. I hope my ramblings aren't TOO confusing. Thanks in advance for any help you all can provide.