Getting ready for the Bio-Mizer

[StorminN]

Jeff, I'd start with the local metals scrap yard, or building recycling place...

Are any of these places near you?

-Norm.

[Reddog]

I'd like to find a smaller old fashioned"Radiator" for out there, but I dont have a clue where you would start to look. That aint something you could afford to have shipped, and there is no where around here that I know of that would have any salvaged.

Jeff,
If you find one down my way let me know. I could always get it on the "Going to the farm delivery truck".  ;)

[Furby]

They just sold 4 cast iron radiators at auction about a month or so back.
I'll keep watching.
There is a scrap yard that I need to stop to soon to check their recycle center, they ALWAYS have some, but can be pricey there.

[ronwood]

Furby,

Those tall cast iron radiators don't seem to work to well. My dad has one in his shop and it does not seem to work well for some reason even with a fan behind it. I think the were made for steam heat. I might be wrong on that.

Ron

[Jeff]

I've had one of those inspirational moments. They don't come often and some times I wish they never came at all.  ;D    I think I got a way to build a el cheapo heat exchanger....

"From the guy that built the remote control gate."  ;)

[StorminN]

When I was in Italy a couple of winters ago for the Olympics, the apartment we rented was heated with hot water, and the bathroom had a heated towel rack... simply some pipes welded together in such a way as to make a towel rack and also let water flow through it. There's nothing like warm, dry towels when you come in from the snow...

-N.

[Furby]

I did the gal. pipe thing in reverse, using as a heating element in the fire.
Worked so well I ended up with a steam whistle!

[beenthere]

I've had one of those inspirational moments. They don't come often and some times I wish they never came at all.  ;D    I think I got a way to build a el cheapo heat exchanger....

"From the guy that built the remote control gate."  ;)

Just goin to buy some good garden hose? 

[Jeff]

No, I have accumulated some parts today. A segment of finned copper tubing. (replacement parts for a baseboard heater acquired from the obsolete shelf at the local plumbing and heating store for scrap price), a 5 foot chunk of 3" stove pipe, some copper sweat fitting to 1" barb, a small metal bathroom exhaust van with a 3" duct port on it, some stove pipe hanger clamps and some other odds and ends. 

[Jeff]

I'll let ya know if this works later on this evening.


The first photo shows the parts I used. I already had started and the 90's and extensions and fittings all soldered on to the old baseboard element in this photo. I layed out where abouts on the length of stove pipe I wanted my copper to come through, and then cut notches with my dremel.  I then simply slid the element in the stove pipe, lined the tubing up in the notches, and snapped the pipe together.


Here is is completed. Ready to go install.



A look down the end to see the element inside the pipe.



Tammy came out and helped me hold things while I installed the PEX. Here she is taping the PEX runs together.  there is quite a bit of exposed PEX now, so I should be using up a bunch of that extra heat I've needed to get rid of.


Installed in the little cabin.  I don't have the thermostat hooked to it yet. Not going to waste my time on that in case it don't work. If it does work, I'll build a cedar enclosure for the heater with some sort of decorative grill front when I get to finishing off that back wall in the cabin.  I may need to drill holes around and along the stove pipe for more air to come out. Right now it can just all blast out the end.  We'll see how it works that way.  I'm out of L.P. and Tammy is getting the tank filled while she is up town. I'll fire it all up when she gets back.



Its pretty warm out today compared to what its been. Here is the starting Temperature in the shed.  Hope it works!

[Kevin_H.]

Hey jeff that looks really interesting, I dont see why it wouldn't work.

[Jeff]

If it does, I got out of this for less then $40 counting the additional PEX clamps I had to get. 

[breederman]

If you put an elbow on te end will it shoot the hot air out into the room instead of along the wall? 

[Jeff]

The room is insulated, so I wouldn't think it would matter if it goes up down or sideways would it?

THis looks like its going to be pretty low volume so Its probably going to take quite awhile to heat that room up as everything in it including the building itself has been froze solid all winter.

[Brucer]

Jeff, you might find it works better without the fan and duct.

With the arrangement you've got, the first fin blocks the airflow across all the other fins. With no ductwork, air can rise freely past all the fins -- and it will rise as it picks up heat from the fins.

If it ain't heating up quickly enough for you, you could try snapping off the piece of duct and see if it works any better that way.

[Jeff]

Thanks for the ideas Bruce!   You may be right.

[Jeff]

I'm going to list this heat exchanger as a failure. Not enough heat comes from it to make a difference. There is no appreciable difference in the amount of heat I am using from the Bio-Mizer either, even with probably 30 foot of exposed uninsulated pex in the system.

[StorminN]

Jeff, what's the temperature of the water at the inlet of this baseboard section? Are you sure it's hot enough / has enough flow?

Anyhoo, those hot-water baseboard sections work much better when they are still mounted in the metal baseboard covering they come in... the shape of the coverings and the openings at the top and bottom set up a convection current for the whole room that takes heat away from the fins on the baseboard and fills the room.

P.S. If you want a cheap way to measure the water temp long-term, you can get an aftermarket automobile water temp gauge, they are usually 1/4" pipe thread... get a T that is 1" on either side and smaller on the other (what would be the base of the letter T) and then some reducers to screw the temp sensor into the T... I'll see if I can scrape up some pics of what I'm talking about.

[Jeff]

I'm guessing its almost as hot as the boiler. You dont want to touch it but for a moment and you certainly can't hang on to it.

I've been looking on line for the fans I have seen mounted to heat exchangers and hanging in shops, but I cant find anything.  There is a guy on ebay selling 12 by 12 20,000 btu coils, but there is no fan on them.  20,000 would be more then big enough for that 12 by 16 cabin.

[thecfarm]

I think the boiler guy told me you can hold on to pex pipe at 180°.It will be hot but you can stand it.But copper you can not hold on to it.Sorry it did not work out for you.Maybe the baseboard covering idea is right.It might need the air flow to make it work right.

[Brucer]

Liquid-to-air heat exchangers work best when the air side has fins arranged so the air can move parallel to the fins. The type of baseboard unit you have was designed to have the copper tube horizontal and the fins vertical (as you have). The air moves by natural convection as it is heated.

You should be able to more heat from it by moving the air across the fins with a fan. The problem with the system as it now exists is the air isn't moving parallel to the fins. In fact, the fan-blown air probably isolates the fins and interferes with  natural convection.

Possible solutions, starting with the simplest.
1) remove the piece of duct and let the air circulate naturally.
2) add more finned units in series -- these things were meant to transfer heat from water to air.
3) use a fan to pull air past the fins, but keeping the air flow parallel to the fins.

Regarding the last point, blowing the air is very directional and is hard to distribute evenly across a long surface. Pulling the air will draw the air from all directions. You don't need a very big fan to do this. The big problem is coming up with a way to do it, and that usually involves a lot of sheet metal.

One thing you can try is to open the piece of ductwork up along the seam, and spread it apart so the finned tube is sticking half way out of the side of the duct. Block off one end of the duct, and arrange the fan to pull air out the other end. This will draw air into the duct from between the fins. Your fan may turn out to be too powerful for this -- a surplus computer fan might do the job.

The fastest way to see how effective a heat exchanger is, is to measure the temperatures of the water going in and out. The more temperature drop, the more effective (provided the water flow doesn't change). When you're comparing one experiment to another, it's probably good enough to just measure the outlet temperature.

[beenthere]

I have this type of finned copper pipe for baseboard heat. On one loop, I have about 30' of it, with the openings on the baseboard enclosures in two of the three bedrooms closed. The water returns to the boiler just about the same temperature that it leaves....so the 10' of open baseboard removes very little heat from the water.

But it is even heat... ;D ;D  and it keeps the one bedroom (now a sewing room) heated.

Blowing air across, rather than along, like is being discussed sounds like the best way to go, to me.

[Larry]

Would a heater core out of a truck...or maybe a school bus work?

[chet]

Jeff.... why don't ya build a little plywood "furnace" like I got heatin' my shop? You've seen how toasty my shop stays. 

[Brucer]

Would a heater core out of a truck...or maybe a school bus work?

Yep. There's a few things to keep in mind, though.

First, heater cores are designed to have air blown (or sucked) across them. So you gotta have a fan to get any appreciable output.

Second, because an automotive cooling system is pressurized, the water temperatue is well above the "normal" boiling point of water. Jeff's system will be running cooler than an automotive system.

Finally, a truck cab ain't near as big as Jeff's cabin. The bus heater might do just fine.