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Post by rmc on Dec 24, 2019 13:35:41 GMT
To evacuate a room of old air, one uses a fan.
But which type is strongest at that? Which fan is best at pulling air?
I ask this because I am designing a chamber one could sleep in, and the tiny chamber gets warm with body heat. I'd put a fan in, of course, but the ducts leading into and out of the chamber need to turn 180 degrees in order to damp down any incoming sound from outside the chamber.
So, this fan needs to be strong. Very strong. They have inline duct booster fans, but warn that they aren't really designed to produce pressure, which is likely what I need, I think.
Plus, my fan won't be pushing in air into the room the way a lot of fans usually do. Rather, it will evacuate air out something like the way bathroom ventilation works. So if you've ever put your hand in front of or behind a normal fan, you'd quickly see that the pusher side moves air hardest, I think. It is the same on both sides actually, overall. But, the pusher side concentrates power toward the center of the air column. While the inlet side pulls air evenly over a wide swath of space. It feels more powerful on the pusher side, therefore.
Ducted fan? Centrifugal fan? Other? Which type of fan pulls the hardest do you think?
Do you have any experience discovering a uniquely strong fan system? Can you share it here, please?
Thank you!
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Post by GTCGreg on Dec 24, 2019 14:24:44 GMT
What you want to use is a small centrifugal blower (squirrel cage type.) They are not only quieter than a fan, but can deliver substantially more static pressure as is required in a ducted application. Not only do they develop more static pressure on the discharge, but they can generate more suction on the intake. This could be used as an advantage as the blower could be mounted at the discharge end of the duct, further away from the sleep chamber and thus reducing the noise in the sleep chamber.
Keep in mind that the input of a centrifugal blower is usually at right angles to its discharge. This could actually be an advantage if you design your duct work to accommodate it.
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Post by rmc on Dec 24, 2019 15:04:12 GMT
What you want to use is a small centrifugal blower (squirrel cage type.) They are not only quieter than a fan, but can deliver substantially more static pressure as is required in a ducted application. Not only do they develop more static pressure on the discharge, but they can generate more suction on the intake. This could be used as an advantage as the blower could be mounted at the discharge end of the duct, further away from the sleep chamber and thus reducing the noise in the sleep chamber. Keep in mind that the input of a centrifugal blower is usually at right angles to its discharge. This could actually be an advantage if you design your duct work to accommodate it. Many, MANY thanks for this! Just as an aside, the method I've chosen incorporates the sound of the fan as a kind of white noise generator. The fan motor is housed on the outside of the chamber, naturally; after all that mineral wool, cellulose, etc. So the hum shouldn't be too bad. I wanted the fan to pull air out of the chamber, rather than blow air in, so as to better help keep the simple hatch shut by way of air suction. So, anyway, the evacuator motor is located almost directly above me, outside the chamber, pulling air out of the compartment. While the air inlet is located at the foot of the chamber, beneath the mattress frame, along the floor. Both ducts are padded (felt and mineral wool), and make a 180 degree turn too to help block outside sounds from getting in. I realize all chambers like this merely end up being sound-damped or sound "resistant" rather than actually sound proof. The low end thumps are hardest to damp down. So I have chosen to also incorporate white noise. I've become accustomed to a fan running on medium in an open room anyway. Plus I may continue to use the silicone putty ear things (not true ear plugs since they don't enter the ear canal - a problem for me if they did) Oddly, this one sounds powerful and inexpensive. But it doesn't seem to be centrifugal? link |
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Post by GTCGreg on Dec 24, 2019 15:17:07 GMT
One thing you might consider is reversing the airflow. Draw the air out of your chamber at the foot of the bed and fresh air in up near your head. That could have two advantages. First it would give you some direct airflow on your face. I like sleeping with a fan blowing on me because I like to feel the airflow, but this is a personal preference and you may not want this. The other advantage would be to locate the low frequency vibrations from the blower motor as far away from your hearing range as possible. While the higher frequencies of White Noise may be desirable to block outside noises, the low frequency rumble of a motor mounted directly to a hard surface is not normally desirable. Again, these are just suggestions and your airflow approach may be better for your personal situation.
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Post by rmc on Dec 24, 2019 15:21:41 GMT
One thing you might consider is reversing the airflow. Draw the air out of your chamber at the foot of the bed and fresh air in up near your head. That could have two advantages. First it would give you some direct airflow on your face. I like sleeping with a fan blowing on me because I like to feel the airflow, but this is a personal preference and you may not want this. The other advantage would be to locate the low frequency vibrations from the blower motor as far away from your hearing range as possible. While the higher frequencies of White Noise may be desirable to block outside noises, the low frequency rumble of a motor mounted directly to a hard surface is not normally desirable. Again, these are just suggestions and your airflow approach may be better for your personal situation. Since you make some valuable points, I am designing it such that it could be configured in either manner now... the door won't be simple press fit any longer since air entering could blow open the simple hatch I had designed. Thanks again! By the way, did you see the blower at 1200 CFM from Lowe's in that link above? It doesn't look centrifugal, but promises to make negative pressure if needed. How is their design configured? |
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Post by GTCGreg on Dec 24, 2019 17:41:11 GMT
1/3 hp sounds like it may be a little overkill for your application. But of course, if that’s marketing horse power, then who knows. I would think that something more like this would be better suited. Note the the larger the diameter of the wheel, the lower the overall noise will be. At about 120CFM, at 0.2" static pressure, which is probably a lot higher than what you are going to have, it would replace the entire air in a 6X8X5 foot sleep room about every two minutes. They do make smaller diameter ones with the same CFM specs but they turn a lot faster and would be a lot nosier. Of course, if you want noise, the smaller ones would be the way to go.  www.zoro.com/dayton-blower-134-cfm-115v-055a-1550-rpm-2c647/i/G0995732/ |
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Post by rmc on Dec 24, 2019 18:05:54 GMT
1/3 hp sounds like it may be a little overkill for your application. But of course, if that’s marketing horse power, then who knows. I think I'll end up just testing several blowers within the chamber, and settling on the one best suited. Will need to be able to return the ones I didn't like (or most of them, anyway). Besides, the noises such a fan makes might not be too bad for me tucked away inside (might not)... but people in my unit or above my unit may notice the constant vacuum sounding noise and may not appreciate that all night. So yeah, one third horse power could cause all kinds of trouble... So, I take it you mean that the Lowe's blower, linked above, is basically a strong fan even though apparently not designed as a centrifugal fan all because it just has a whopper of a motor? Is that what you mean? |
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Post by GTCGreg on Dec 24, 2019 18:30:14 GMT
They don't give a noise spec, but at 1200CFM, this things got to sound like a 747 at take off. But then, it does have a speed control so you could always throttle it back some and would still have plenty of reserve if you needed it.
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Post by rmc on Dec 24, 2019 18:32:17 GMT
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Post by GTCGreg on Dec 24, 2019 18:38:50 GMT
Some reviews I find useful and others pure BS. Because this one is a centrifugal type, I like it better than the Lowes blower. May be a little awkward to mount and attach ducting to, but with two auxiliary outlets, you can always find a place to plug in your phone charger. |
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Post by rmc on Dec 24, 2019 20:00:07 GMT
Some reviews I find useful and others pure BS. Because this one is a centrifugal type, I like it better than the Lowes blower. May be a little awkward to mount and attach ducting to, but with two auxiliary outlets, you can always find a place to plug in your phone charger. Some "bounce house" pump-fans have additional cooling fan to prevent overheating. I might house the fan to cut some sound. It might be nice to avoid overheating in that case: Bounce house fan or pumpThere is an FJ-30 air pump by zhongshan wilson plastic industrial co ltd, but of those that I found they were second hand, on auction. Anyway, that model includes the additional cooling grill for the motor. Most others that I've found so far don't have the cooling port, making it difficult to justify totally enclosing it. |
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Post by GTCGreg on Dec 24, 2019 21:43:51 GMT
The bounce house fan is probably designed for a lot higher static pressure than you need but lower CFM. I don't know about motor cooling. That one looks like it's pretty well sealed to make it rain proof. I think you are better off sticking with a ventilation type blower of fan rather than one designed more for compressing air.
Another thing you may consider using is a bathroom vent fan. They come in a number of different sizes and configurations and are usually configured to attach to a 4 inch duct..
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Post by rmc on Dec 24, 2019 23:49:16 GMT
The typical bathroom-grade fan struggles to move air through a lot of convoluted ducting like I need to have. Keep in mind the currently-intended inlet is situated beneath the bed. Air has to squeeze up past the mattress in a few places to cool the cabin. The inlet is situated down there to make outside noise less likely to get in easily. And the padded ducts coming in from the outside all double back on themselves zig zagging 180 degrees in a possibly futile attempt to fend off outside noises coming in... which would make all that heavy and expensive insulated wall panels pointless if outside noises can just bypass the insulation and Walz on in through some holes. Thus a complicated ducting path to better enable sound damping.
But, now a lot of power is needed to flow the air through all that.
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Post by the light works on Dec 25, 2019 3:59:11 GMT
I can pretty much guarantee that with the ones you listed, you won't hear much other than the fan. also keep in mind that with the 1200 CFM you're specifying, you'll have to have a good grip on your blankets. you'd be better off with something like this: na.panasonic.com/us/home-and-building-solutions/ventilation-indoor-air-quality/ventilation-fans/whisperfresh-selecttmthat way you can put it on the supply side with oversized (nonmetallic) flex duct, and have an oversized flex duct for the exhaust, and the ducting will transmit the least possible amount of noise. but industrial blowers like your links - quiet is a relative term. and those are quiet relative to a gas powered blower. |
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Post by rmc on Dec 25, 2019 11:29:50 GMT
Will need several experiments once the sound resistant cabinet is constructed, less the duct work:
Experiments with bathroom-type ventilation fans with cfms between 150 to 450.
Experiments with blowers from 500 to 1000 cfms.
Experiments other than those planned above (currently unforeseen experiments)
Experiments trying the ventilation as an extractor located at the head.
Experiments trying the ventilation as an extractor located at the foot.
Experiments trying the ventilation as a blower (into the cabin), head then foot.
In all cases will need to try and have an option to return unwanted equipment.
Each of us has stated their opinion: all of them with key points.
I'll let observation via experiment tell the whole story from here on out.
Thank you!
(After all I do want to end up with a sound resistant sleep chamber, not a sleep resistant one)
As to noisy kinds of fans: keep in mind the fan is outside the sound-resistant cabin.
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Post by rmc on Dec 25, 2019 13:41:00 GMT
I can pretty much guarantee that with the ones you listed, you won't hear much other than the fan. also keep in mind that with the 1200 CFM you're specifying, you'll have to have a good grip on your blankets. you'd be better off with something like this: na.panasonic.com/us/home-and-building-solutions/ventilation-indoor-air-quality/ventilation-fans/whisperfresh-selecttmthat way you can put it on the supply side with oversized (nonmetallic) flex duct, and have an oversized flex duct for the exhaust, and the ducting will transmit the least possible amount of noise. but industrial blowers like your links - quiet is a relative term. and those are quiet relative to a gas powered blower. Yes and no on that, I think, thelightworks. Keep in mind that air flows through some rather complicated baffles. It doesn't just port directly to the outside, or it would bring in a lot of the unwanted noises too. Inside a typical automobile muffler we can see some of the ideas my baffle system hopes to employ. Perhaps using some of the maths with regard to back pressures and air flow for a typical muffler could be useful for deciding how much power and work must be done? |
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Post by GTCGreg on Dec 25, 2019 14:25:43 GMT
MERRY CHRISTMAS!
Well, it seems you have many options to try. I’m not sure you realize how much airflow 100 CFM is. We use a 450 CFM blower to provide the HVAC to the patient box of ambulances. They move a LOT of air, to the point of standing anywhere near the discharge vents is downright uncomfortable. Anything over 500 CFM and you’re talking leaf blower amount of airflow. I think by the time you’re done with your experimentation, you’ll find that actual airflow of 75 to 125 CFM is what you will be needing.
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Post by rmc on Dec 25, 2019 14:47:21 GMT
MERRY CHRISTMAS! Well, it seems you have many options to try. I’m not sure you realize how much airflow 100 CFM is. We use a 450 CFM blower to provide the HVAC to the patient box of ambulances. They move a LOT of air, to the point of standing anywhere near the discharge vents is downright uncomfortable. Anything over 500 CFM and you’re talking leaf blower amount of airflow. I think by the time you’re done with your experimentation, you’ll find that actual airflow of 75 to 125 CFM is what you will be needing. I see that too. But my preferred design at the moment has the motor trying to draw air out... and through a bunch of baffles too. So the people feeling the intense part of the breeze will be on the outside, I'd think. Probably a blower will stir air all around my bedroom, fluttering papers around. Meanwhile, I'll be on the inside of the cabinet with whatever current is left. Merry Christmas and Sir Issac Newton day to you all, by the way!! |
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Post by the light works on Dec 25, 2019 16:05:31 GMT
MERRY CHRISTMAS! Well, it seems you have many options to try. I’m not sure you realize how much airflow 100 CFM is. We use a 450 CFM blower to provide the HVAC to the patient box of ambulances. They move a LOT of air, to the point of standing anywhere near the discharge vents is downright uncomfortable. Anything over 500 CFM and you’re talking leaf blower amount of airflow. I think by the time you’re done with your experimentation, you’ll find that actual airflow of 75 to 125 CFM is what you will be needing. an even better frame of reference is the floor model squirrel cage blower is commonly used to dry dogs in grooming shops - not with heat - just by blowing the water off of the dog. |
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Post by the light works on Dec 25, 2019 16:14:52 GMT
I can pretty much guarantee that with the ones you listed, you won't hear much other than the fan. also keep in mind that with the 1200 CFM you're specifying, you'll have to have a good grip on your blankets. you'd be better off with something like this: na.panasonic.com/us/home-and-building-solutions/ventilation-indoor-air-quality/ventilation-fans/whisperfresh-selecttmthat way you can put it on the supply side with oversized (nonmetallic) flex duct, and have an oversized flex duct for the exhaust, and the ducting will transmit the least possible amount of noise. but industrial blowers like your links - quiet is a relative term. and those are quiet relative to a gas powered blower. Yes and no on that, I think, thelightworks. Keep in mind that air flows through some rather complicated baffles. It doesn't just port directly to the outside, or it would bring in a lot of the unwanted noises too. Inside a typical automobile muffler we can see some of the ideas my baffle system hopes to employ. Perhaps using some of the maths with regard to back pressures and air flow for a typical muffler could be useful for deciding how much power and work must be done? lke I said - with cheap high volume blowers, the blower will drown out most of the outside noises, anyway - and especially if you are artificially restricting the airflow. all the fans I use in bathrooms are rated for quiet operation, and even with them, adding 180 degrees of bend roughly doubles the blower noise. that's why I like the oversized flex duct. there is a lot less restriction, and the soft material seems to soak up noise. it would also make it very easy to experiment with the shape of the duct. of course, the heating guys like it because it is the same stuff they use for distribution runs in their HVAC system. |
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