DIY heat exchanger

[Doodlebug]

Thought this may be of interest to some. I have spent a while thinking that to make one would be very expensive using copper tubes or something similar, but the idea of using plastic to make it seems like a pretty good and efficient idea.

 

Heres the link,

 

http://www.builditsolar.com/Experimental/DIYHRV/DIYHRV.htm

 

I must say that the BSS is quite outdated, there is no reason that you could not have a super insulated boat, with no vents, using a heat recovery system to keep the room vented.

 

Doodlebug

 

 

[nicknorman]

I have thought about this, however one problem is the lack of secure power on a boat. If ventilation required power to run fans, it would only be a matter of time before the fans stopped for some reason, then no ventilation = dangerous especially when you want it - in winter with the stove on. I suppose you could have a "fail safe" ie fixed vents that are held closed when the fans are running, and spring open of their own accord if the fans stop. But that's all getting a bit complicated.

 

Also, in terms of heat exchanger design, might as well make use of the shape of the boat, for example a long thin heat exchanger running under the gunnels for the length of the cabin, concentric pipes with reverse airflow, thus giving a big exchange area but using fairly redundant space. A box is much harder to site.

 

Plastic tubes have the problem of much, much worse thermal conductivity than copper.

Edited October 8, 2013 by nicknorman

[by'eck]

We had a similar device on a Port Solent home to recover heat lost to ventilation in the winter. Keeping the filters clean was a dirty job in the loft though. There were summer and winter setting flaps you had to remember to adjust.

[Teadaemon]

I must say that the BSS is quite outdated, there is no reason that you could not have a super insulated boat, with no vents, using a heat recovery system to keep the room vented.

 

The main reason the BSS requires fixed ventilation is to reduce the risk of CO poisoning (or theoretically asphyxiation due to oxygen starvation). After all, saving money on your fuel bills isn't much use if you're not alive to enjoy your toasty, warm boat, is it? The problem with relying on forced ventilation using fans is that they fail, or batteries go flat, and then you've got no ventilation at all.

[Doodlebug]

But its no different to a house? Some houses (mainly on grand designs) are air tight and rely on ventilators.

 

I don't see how a boat is any different.

 

Also with some clever engineering it could be made so it uses the power of convection and not fans.

[Alastair]

Using the power of convection . . . Isn't that called having vents?

[Teadaemon]

But its no different to a house? Some houses (mainly on grand designs) are air tight and rely on ventilators.

 

I don't see how a boat is any different.

 

Also with some clever engineering it could be made so it uses the power of convection and not fans.

 

I think that you'll find that where those houses have fuel-burning appliances, they've got balanced flues, so they draw their combustion air directly from outside. If you have an appliance with a balanced flue on a boat, then it's ignored in the calculation of minimum required ventilation for BSS purposes.

[nicknorman]

 

But its no different to a house? Some houses (mainly on grand designs) are air tight and rely on ventilators.

 

I don't see how a boat is any different.

 

Also with some clever engineering it could be made so it uses the power of convection and not fans.

House: Much bigger air volume and more reliable power supply. For convection (even if it were feasible, which I'm not sure it is considering the aim is to heat the incoming air and cool the outgoing) requires vertical extent. Present in a house, present much less in a boat. Plus, as teadaemon says, balanced flues for fuel-burning boilers etc.

[Mac of Cygnet]

 

House: Much bigger air volume and more reliable power supply.

 

We have averaged about 3 power cuts per winter at the house. My boat batteries have only failed me once in several years. Yes, I know that once may be enough in this context, but a house (certainly our house) does not have a more reliable power supply.

[nicknorman]

We have averaged about 3 power cuts per winter at the house. My boat batteries have only failed me once in several years. Yes, I know that once may be enough in this context, but a house (certainly our house) does not have a more reliable power supply.

Well that's what comes of living in the wilds of Scotland! We have only had one power cut in our present house in Aberdeen, that was due to an underground cable fault outside the house. But anyway, my comments can only be a generalisation. Perhaps I should stick to the line about the volume of the house vs the boat! Unless you are going to tell me you live in a tiny house!