Embezzle a bit more of your building’s heat | Hacker News Reader

Embezzle a bit more of your building’s heat

marco.org

43 pointsblasdel17 comments

So, a box fan that looks roughly like the one pictured seems (from a quick poking around) like it uses 80-150 Watts. Intuitively (not measured, not scientific - just a hypothesis) it seems like a box fan will also move much more air than is really optimal for this application. Also, optimal results are probably obtained by drawing in air close to the ground and forcing it up through the radiator, not grabbing air from all around and pushing it through.

This seems like an area for experimentation, modeling, and maybe even product design. Would a few computer cooling fans produce as much benefit at a fraction of the electricity cost? Even better, maybe, can a very quiet and just-enough air circulation be built that operates solely on the thermal energy generated near the hot input side of the radiator? A probably absurd suggestion but I can think of one past apartment where I would have considered it: duct work (e.g., dryer vent tubes) combined with computer cooling fans drawing air from the coldest part of the apt. and pushing it towards the radiator....

Natural convection will do what you want. (If he removed the bookshelf,) air will get sucked in from the bottom, heat up, and then rise. The problem is that the warm air will sit under the ceiling. I think circulation would be better used to make sure the air doesn't stratify, ie blow some of the warm air under the ceiling downwards.

It's funny you should write this, because I've been meaning to try exactly this: I have a 12V cable lighting system running over the steam heat radiator in the room I'm sitting now, and I was going to put a 200mm computer fan across the cables blowing down. Power is already up there... ;-)

I don't understand the premise of what he's trying to do. It seems to allude to a system where someone else decides how hot your place should be, without any thermostat feedback. In Sweden, there are apartment buildings that have centralized hydronic heating, but in those cases the hot water is on all the time and you adjust the temperature in the apartment by changing the hot water flow using the valve on the rad. If the system turns itself off when it is too cold in some parts, then he really should demand to have a professional look at the system instead of hacking it. A heating system that's unbalanced and not running optimally is likely to waste a lot of energy.

He's talking about a traditional radiator system. They are generally hooked up to either no sensor, or to one that's nearby the unit. I think his idea is just to heat the room more quickly.

> In Sweden...

New York has old, old, old, old infrastructure. It might surprise you to know that they still dump their trash onto the streets, where it rots in the summer heat and mixes with AC condensation that drips down (because their AC units hang out of windows) and creates giant rivers of foul smelling shit water that you must step over carefully to avoid.

IIRC a fair amount of the steam used in NYC is actually generated in NJ and pumped under the river.

Passive solar heating worked remarkably well for me when I was living abroad in a place with so little electricity that I wasn't permitted by the landlord to have a space heater. I just opened my shades all day during daylight, and closed them at sunset. That's all, but that was enough to make my room noticeably warmer than ambient outdoor air temperature--so much so that my visitors from other units in the same building kept asking me if I was using a space heater on the sly. Try it; you might like it.

Good passive solar design (with the right surface of window to thermal mass) should be part of the education of all architects, IMO. Would make for more comfortable buildings and save a lot of fossil fuel energy that we could better use for something else.

He seems to have a shelf of books on top of the radiator, which will limit its effectiveness, box fan or not.

I would have to disagree. It certainly limits effectiveness without the fan, but I expect the fan to more than counteract that.

That's what I was going to say: Maybe he wouldn't need the fan if he removed the shelf.

Forced airflow is several times more effective than relying on convection. Remember that hot air rises, so if the room was narrow, removing the shelf would indeed be sufficient. However, if the end of the room is quite far, it will take a quite a little while for heat to circulate.

The fan speeds up the process by sucking a lot more cold air in through the radiator, forcing it against the warm metal and blowing it out into the room. (Think why the heatsinks in your computer have fans.)

The shelf may act as a way of ensuring air blows through the entire depth of the radiator, but I doubt it has any significant effect either way.

This is brilliant. I could have used this in draughty old apartments in Montreal, with their 12' ceilings and giant old radiators. Yet another of those "Why the ass didn't I think of... ah forget it" ideas.

This won't work for long if everyone in the building starts using the same trick. Better keep that box fan hidden from the neighbors.

That assumes that there's a fixed amount of heat being input into the hot water (steam?) circulation system.

Are there modern boilers that adjust the amount of fuel added and/or the burn rate, based on the incoming water temperature? Did traditional boilers just eject the excess as waste heat (perhaps through a steam pressure relief valve)?

This is surprisingly, and unfortunately, relevant to me. Nice hardhack.

Is that The Blank Slate by Steven Pinker?

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