Ventilation measurements

[Zephod]

I doubt there's an easy way to convert CFM to FPS so I've been measuring the throughput of my bilge blower. I have two and at full power they should extract 260CFM or the entire volume of air inside my bus in about 4 minutes.

Because I don't much care for bugs, my mushroom vents have mosquito mesh glued to plastic drain whatchamacallits just like these pictured beside the bilge blower.
https://photos.app.goo.gl/t5StPdYvEH22QJLZ2

I have ants crawling on the roof of my bus, even! Anyway I measured throughput from the bilge fan at about 50% when I'm using input and output meshes. I can upsize the input mesh easily by building a box with a mesh over it. That's easy. That eliminates any input reduction.

I'm thinking of some kind of flapper vents for the outside now. I'm not sure how much power I'd lose and whether my existing mushroom vents might be better.


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[muldoonman]

I would just use a Flux Capacitor. Think it  takes 1.21 gigawatts of electricity to energize it. Wouldn't need screens as all ants and small rodents would be vaporized if they touched it. Install it in front of bilge pump. 

PS,

Don't stand in front of it when you flip switch.

[richard5933]

I've pondered this thread for a while, just like I did your earlier thread about trying to ventilate with the bilge fans.

It seems to me that even at top performance these fans just won't have the ability to truly circulate and exchange the air in the bus. They could easily move their full rated CFM, but do so as a narrow column of air running from your intake port to your exhaust port. All the areas not immediately adjacent to this narrow column of moving air will be largely stagnant.

In my wood shop I've got a spray booth. The booth has an 8'x10' opening. There is a 24" fan on the roof which is moving 8000 CFM. However, the installers did not just put a 24" hole in the top of the booth to suck out the air. There is a 3-foot deep air plenum running all the way up the back wall of the booth which is the same size as the opening - 8'x10'. When I questioned the extra expense of the plenum, they explained about the necessity to have no stagnant air in the booth. If they only install a 24" opening, they explained that I'd have a 24"-wide path of fresh air and the rest of the booth largely not moving (other than what moved by friction).

I'm not suggesting that you install a plenum, but I just don't think that the small diameter of a bilge fan will ever properly ventilate a bus. The Fantastic Fan we had on the roof of our coach was able to move a lot of air and had a much wider fan, but even it had limitations. If we opened windows on the opposite end of the bus things would generally ventilate, but we'd still have stale air in the corners and in the more hidden areas.

Maybe it's time to cut bait on the bilge fans and move to something more substantial?

Richard

[Zephod]

If I had a roof vent, things would, im sure, be easier. I don't so I'm working within what I have. Ventilation as it is, is good - the air does not get stuffy nor do smells linger.

I'm attempting to pump more air out though in order to move the air faster. My bus has an interior of approx 97 inches by approx 72 by approx 24 feet. I've estimated that as over 1000 cubic feet.

If the bilge fans combined can remove 260CFM of air then 5 minutes of them running should exchange all the air in the bus and crucially remove some of the heat. Frequent running should keep the inside cooler even on hot days.


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[HB of CJ]

We used bug netting and just opened up some side windows to catch any prevailing breeze.   Velcro tabs were glued all around the perimeter of the window frames both sides ... the bug netting and the window frames. 

The bug netting and velcro were off white and cut to size.  The velcro also stabilized the netting turning it into stationary curtains while driving down the road with open side windows.  Crown Supercoach ex schoolie.

[Zephod]

I've had a go with those expandable bug screens. They're not bad bar for the 1/16th gap around the bottom. They certainly allow cool air in. I think some tape on the bottom would help by trapping critters. That's only half of the equation though. Extracting air is the priority. As I'm trying to keep my bus as anonymous and Bus like as possible, I can't do too much on the outside. Otherwise, I'd get some aluminum tubing, paint it black and set up a heat extractor powered by convection.


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[opus]

Unless you've put insulation on the ceiling of the bus, I'm afraid keeping a skoolie cool is pretty difficult....shy of staying in the shade. 

I'm assuming thats why you are wanting air flow.

[Zephod]

Unless you've put insulation on the ceiling of the bus, I'm afraid keeping a skoolie cool is pretty difficult....shy of staying in the shade. 

I'm assuming thats why you are wanting air flow.

Yes. So far the biggest thing was painting the roof white. That dropped internal temperatures by 30+ degrees in the height of summer.

I didn't insulate tge Roof and am unlikely to do so. That's why I want airflow.


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[windtrader]

Rather than use a exhaust fan to create air movement, you can always use a box fax to circulate the air within the coach. I assure you that will create more effective movement inside the coach at far less energy. This may change the ambient air temperature as the fan mixes the air high and low. The air movement feels cooler as well. Then use the exhaust air system to bring in outside air as desired. The fan specs can likely be less demanding including using a lot less energy.

[opus]

I didn't insulate tge Roof and am unlikely to do so. That's why I want airflow.


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Nor did I, nor will I.  Regardless, hard to beat the scorching steel, even with airflow.  I just find shade and call it good.

[eagle19952]

soaker hose on the roof.
a little water goes a long way.