Sorry, unsucessful at snatching the pebble from my hand.
Still goes out, have to blow a little harder.
Try puckering up your lips a bit when you inhale to increase your capture velocity. Practise the lip formation on banana.
Ah. nice try grasshopper, but your experiment is flawed.
Take a candle, and hold it a foot away from your mouth. Hold your mouth WIDE open just as you did when you “SUCKED” air in. Now blow as hard as you can to blow the candle out. Keep moving closer repeating, and you will burn your own lips grasshopper.
See robo, my theory doesn’t “suck” after all does it?
Go back to the drawing board guys.
I told you this is going to be good for another 20 pages.
Sorry, unsucessful at snatching the pebble from my hand.
Still goes out, have to blow a little harder.
Try puckering up your lips a bit when you inhale to increase your capture velocity. Practise the lip formation on banana.
The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.
http://www.ductstrap.com/
Hum,
The push-me-pull-you of HVAC
I wouldn't have tried to suck the candle out with my mouth wide open, othwies how would I burn my lips?
It will only go for another 20 pages because you are too stupid to understand when you are wrong. I can understand that you "suck" and "blow" with your mouth wide open as a natural thing to do, but I can certainly suck air with a very closely pursed lips. But then again, that thought has probably gotten you more excited then you deserve to be.
You realize that you are not only arguing with experts but one who in a single thread has proposed stealing from a local bar and a kid's birthday cake. You are just out of your league here maiden. Unfortunately you will continue to boor us with more mundane posting because you don't understand that you have no argument.
Lets see now; we have no clue as to anything about you, including your occupation, gender, location or affiliation with anything in the HVAC trade, yet we do know you are a boisterous conservative.......OH MY!!! You could be Ann Coulter! Is this your way of getting off on a sexual fantasy Ann? You are one sick beeech.
Training is important!
Practical Training is a must!
self edit, see below
[Edited by madeinusa on 11-30-2005 at 12:38 AM]
self edit. you got the message.
[Edited by madeinusa on 12-01-2005 at 12:31 AM]
Sorry for the rude interruption Carns.
I did think about velocity while inhaling and increasing velocity like you said.
I also know it is not possible to develop as much velocity inhaling when you are “sucking” from basically the whole atmosphere.
If you put a 5 foot straw in your mouth and recorded the velocity “at” your mouth while inhaling, and also recorded it while exhaling, it would probably be very close. Maybe not, being you are able to squeeze your lungs harder with muscles to exhale, than your ability to use your muscles to inhale.
Basically you are attempting this experiment at two different locations. Exhaling, the oxygen is coming out through a small duct system, your windpipe, and building velocity, yet when inhaling, the air is not coming through a duct system.
To get a truer reading you should measure at the entrance to the lungs while exhaling and inhaling.
[Edited by madeinusa on 11-30-2005 at 04:17 AM]
. The fan size, RPM, blade shape, Return duct size, Supply duct size, Filter size. And such. All have been designed for delivering a maximum specific amount of air with the ability to deliver a maximum specific temperature, under certain atmospheric conditions.
To do as one pleases would be speculation, yet I do realize that it is not cost effective or reasonable to do every single thing by the book. A lack of designed return air will place a drag on the motor and may require more hp. An increase in return air will affect temperature and efficiency. Some returns require plenum gravity. Others require fan forced air.
I come from a forced air home. A room was to hot close down on the room deffusser, room to cold open it up. It works but it is the same as the candle test. Works but to what degree and all the variables are missing from the equation. How much money going out the window.
Later on I Chose to install hot water but if I did do air for my self you can bet that system would receive not only a load for the full house but every inch of every room including btu absorbing decorations ,furniture and such. Including gage of duct and size of duct and the supply return with every diffuser balanced. You only should need to do it one time and forget it forever.
You could think of it this way, would you guess at how much your paycheck is? Or did you sit own and check to see if that you had been told hourly was actually in the check.
Like that quote some one has, measure twice cut once.
If you kept the lip position the same, perhaps to accomodate a big dill pickle, and breathed in and out at the exact same rate, you will be able to exhale and blow out the candle every time and but you will not be able to extinguish the flame by inhaling.Originally posted by madeinusa
Sorry for the rude interruption Carns.
I did think about velocity while inhaling and increasing velocity like you said.
I also know it is not possible to develop as much velocity inhaling when you are “sucking” from basically the whole atmosphere.
If you put a 5 foot straw in your mouth and recorded the velocity “at” your mouth while inhaling, and also recorded it while exhaling, it would probably be very close. Maybe not, being you are able to squeeze your lungs harder with muscles to exhale, than your ability to use your muscles to inhale.
Basically you are attempting this experiment at two different locations. Exhaling, the oxygen is coming out through a small duct system, your windpipe, and building velocity, yet when inhaling, the air is not coming through a duct system.
To get a truer reading you should measure at the entrance to the lungs while exhaling and inhaling.
[Edited by madeinusa on 11-30-2005 at 04:17 AM]
The velocity through your lips is the same in each case just the direction of the air flow is opposite.
So the little experiment shows that pressure differential causes air to move from areas of high pressure to lower pressure, and return air to a fan inlet will chose the path of least resistance. You were sucking air from directly in front of your lips, the minute amount of air that travels past the flame was ineffective.
Your straw demonstrates exactly what a ducted return can do, gives you control as to the path back to the fan. With a straw, you can have the candle away from your face and would still be able to extinguish it.
There is a point where the straw will become too long and you will not be able to inhale and extinguish that flame, but using the same length straw you will still be able to blow it out with out having to cough a lung out to build up enough pressure to do so.
Kitchen hoods do not hoover the grease fumes from a cook line, they have to remove air from the hood at, at least the same rate that the thermal uplift from the heated cooking surfaces causes the greasy fumes to rise up into the hood.
The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.
http://www.ductstrap.com/
The birthday candle diffrence is about velocity of the air,really doesn't speak to the discussion.IMHO.
"it allows the higher pressure of air introduced into an area "Originally posted by RoBoTeq
The return air portion of an HVAC ducting system does not "pull" or "suck" air...it allows the higher pressure of air introduced into an area to "return" to the units blower.
That sounds like what you have stated before ,that the supply air pushes the air to and/or thru the return.
Question,if we have place paper over part of the return grille,it stays in place rather firmly.So is it being held their by the supply air pushing it,atmospheric pressure ,or suction from the fan????
hmmmm.
Does an airplane fly because of the air pressure below the wings, or because of a suction above them.
If I remove a sidewall supply, and put a piece of paper in it, and put the grille back on, will the paper blow against the grille because of pressure in the duct, or the return sucking air out of the room.
If I win the powerball for 50 mil, will I give a 2 week notice, or just not show up.
Try another Mr. Wizard experiment.
Get a metal can with a small screw on top. Remove top. Heat it up. Screw on cap and remove from heat source.
As can cools it starts to collapse. Why?
You can pull on a rope, you can pull your wire put you cannot pull air, you have to push it.
There is really no such thing is a negative pressure or a negative temperature, we just conveniently use the terms all the time.
Either you have heat or no heat. Temperature starts at absolute zero degrees and goes up. You cannot transfer cold to something but heat can come and go.
Either you have pressure or you do not, it starts at a perfect vacuum and goes up.
The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.
http://www.ductstrap.com/
The room air pressureOriginally posted by dash
"it allows the higher pressure of air introduced into an area "Originally posted by RoBoTeq
The return air portion of an HVAC ducting system does not "pull" or "suck" air...it allows the higher pressure of air introduced into an area to "return" to the units blower.
That sounds like what you have stated before ,that the supply air pushes the air to and/or thru the return.
Question,if we have place paper over part of the return grille,it stays in place rather firmly.So is it being held their by the supply air pushing it,atmospheric pressure ,or suction from the fan????
Hopefully in the type of climate you and I deal with it is slightly higher than atmospheric.
The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.
http://www.ductstrap.com/
My, my... I wonder if the maiden wet her pants for that last tirade against my character
Aside from the constant stupid interruptions by the maiden, this thread is bringing out a lot of answers to questions that seem to mostly be irrelevant until we get particular in the way we are viewing how physics works in our industry.
To answer the question about the plane; the air below the wing pushes the plane up as the curved top of the wing creates a lower pressure area on the top.
Training is important!
Practical Training is a must!
Originally posted by RoBoTeq
To answer the question about the plane; the air below the wing pushes the plane up as the curved top of the wing creates a lower pressure area on the top.
thanks for the answer, but I did know that.
discoverly channel, one of the 4 channels i watch.
Plus my dad took flying lessons.
So at what point does this air that is pushing in the return grill change to negative pressure and what causes it to do so? If what you say is true there would be no negative pressure in return ducts because the air is being pushed to the blower.Originally posted by Carnak
The room air pressureOriginally posted by dash
"it allows the higher pressure of air introduced into an area "Originally posted by RoBoTeq
The return air portion of an HVAC ducting system does not "pull" or "suck" air...it allows the higher pressure of air introduced into an area to "return" to the units blower.
That sounds like what you have stated before ,that the supply air pushes the air to and/or thru the return.
Question,if we have place paper over part of the return grille,it stays in place rather firmly.So is it being held their by the supply air pushing it,atmospheric pressure ,or suction from the fan????
Hopefully in the type of climate you and I deal with it is slightly higher than atmospheric.
I never flew a plane, but I have jumped out of nearly 300 of them. The parachute I use is actually a square, semi-rigid wing that works on the same aerodynamic principles that all wings work from.Originally posted by beenthere
Originally posted by RoBoTeq
To answer the question about the plane; the air below the wing pushes the plane up as the curved top of the wing creates a lower pressure area on the top.
thanks for the answer, but I did know that.
discoverly channel, one of the 4 channels i watch.
Plus my dad took flying lessons.
As carnak stated; there is no "negative" pressure associated with blowers in HVAC. There is high pressure areas and low pressure areas. Air always moves to a lower pressure area by the air pressure from the higher pressure area pushing its way into the lower pressure area. A blower is designed to mechanically move amounts of air from one side of the blower to the other. This pushes the air on the side that the air has been moved to and the air is replaced on the other side by higher pressure air pushing into the place where the blower took the air from to push.
Training is important!
Practical Training is a must!
When you take an esp reading before the blower with an incline manometer, isn't it referencing to the pressure out side the duct,(atmospheric pressure) trying to push through the manometer.
Its a pressure differencial.
Some one will correct me, but atmospheric pressure is about 411.6 IW, So a -.4IW returm would be 411.2 IW, its still pressure, just less.
Your measuring the loss of pressure, not a vacuum or suction.
you have two static presures. supply and return
return is not a negative presure it is a positive presure to the blower. the supply is a positive pressure leaving the blower. if you increase the static pressure to the blower you will get less presure on the supply. if you decrease the static on the return and alow more air to enter the blower you can increse the static in the supply
in either case you are useing the same air from the eara in witch the air is being used.
to have a negative presure you need to take the air from one place and exhaust it to another with out that same air going back to the same eara it is being taken from
we are useing the same air in the same total eara and the
return takes it in and the supply puts it back at differant volumes and cfm
you can have more return grilles then needed as long as you maintain the proper static presure in the return trunk line. the more grilles the easer it is to have the proper return.
imo only