Another take on ventilation - (room) size does not matter - from urbangarden magazine

[LJB]

kind of interesting. would love to hear/read some opinions from the wider community.

part 1: http://www.urbangardenmagazine.com/...ht=ajaxSearch_highlight+ajaxSearch_highlight1

part 2: http://www.urbangardenmagazine.com/...ht=ajaxSearch_highlight+ajaxSearch_highlight1

The whole room size thing has been a complete red herring over the years. It was a general rule of thumb that hid many details and wasn’t really based on anything but history and lots of other loose rules-of-thumb. It tended to break down in unusual cases and nobody could explain why. We can’t find a basis for it anyplace. It doesn’t make any sense that a 2 cubic meter box with 600 watts needs any more/less cooling than a 35 cubic meter room with a 600 watt light. It just takes longer for the oven to get up to temperature but they both need to get rid of the same amount of heat in the end. A joule going in must be balanced by a joule coming out or the temperature will go up.

The formula shown above has been found in several other places on the web, once you know where to look. It’s basic bread-and-butter info for people that do cooling for desktop computers.

The formula works because it is based on energy transfer fundamentals. It ignores heat loss or gain through the side walls, but you can get more complicated and model that kind of heat also. The effect you point out is one facet of the facts it is based on.

The key idea we like is that it is temperature difference that matters, not absolute temperature. This means the same fan setting will give you the same difference no matter what your inlet temperature is. I’ve been thinking about this a fair amount and realised that the formula is the basis for a crude hot wire anemometer. That’s a thing that measures airspeed by measuring how much a hot wire is cooled by the air as it goes by.

I might have the opportunity to test this formula (details in part 1) in the coming weeks.


Was this originally covered in the Overgrow.com FAQ?

 

[krunchbubble]

very interesting.........

 

[Calimed]

cool article but I wish that mag would have more content than porno nute ads with women in funky fur outfits from barbarella queen of the galaxy

 

[LJB]

cool article but I wish that mag would have more content than porno nute ads with women in funky fur outfits from barbarella queen of the galaxy

Ok, but without the advertising, how are they to create revenue?

Have you ever been to one of the big hydro expos?

Especially in San Francisco it is funny, because they hydro companies send the actual girls in bikinis to stand around the convention hall and look cute.

 

[Calimed]

Really? That is sad. I understand the ads, but does some bikini woman going to sell me on buying nutes? What about hydro makes the titties pop out? No other regular gardening mags are like that are they? I'd rather see a big busty picture of the plant grown with said nutes vs. An anorexic stretched crack ho

 

[LJB]

Really? That is sad. I understand the ads, but does some bikini woman going to sell me on buying nutes? What about hydro makes the titties pop out? No other regular gardening mags are like that are they? I'd rather see a big busty picture of the plant grown with said nutes vs. An anorexic stretched crack ho

They all are accept for more mainstream mags such as Maximum Yield and Grower's Edge.

Urban Garden
High Times
Cannabis Culture
Weed World

 

[LJB]

Indeed. We don't know where the formula originated, but it was covered in the overgrow.com FAQ, as posted on several forums:

How Do I Design a Fan Powered Cooling System for my Growbox?

 

[andyboy]

Ok, first post and I will probably make an ass out of myself but here goes.

Larger room means more surface area and that would mean the heat has a better chance of dispersing through walls and floor. Othervise we could just tell computer-manufacturers to skip the heat-sink (used on the processor to increase surface area) and that they are doing it wrong, they should just get bigger fans.

 

[LJB]

andyboy, from part one of the article:

Avoiding hot spots and taking advantage of airflow momentum is key to this design. The goal is to set up circular air patterns where the incoming cool air enters down low and from each corner. It spirals inward and upward to get sucked out, travelling around the room a large distance and absorbing heat well.