Ultra High lift!

[Larry Cobb]

As I have stated before, the flow rate of a 2" opening is well above what a 14" wand is capable of delivering.

Applying the appropriate formula to a 2" orifice with a lift available of 10 hg.; the flow would equal 786 CFM @ an airspeed of 384 ft./sec.

The maximum flow rate of a 2" opening is much higher with higher lifts.

In a previous test, the actual measurement of a 14" wand with the "newest scalloped hybrid greenglide" was only ~225 CFM @ a TM lift of 16".

Two 14" wands would be ~450 CFM...

Larry Cobb

 

[Lee Stockwell]

261 mph??

In theory.

 

[Duane Oxley]

"Applying the appropriate formula to a 2" orifice with a lift available of 10 hg.; the flow would equal ..."

Such a formula would have to be based upon airflow... but truck mounts have a mixture of air and recovered fluid / soils /residues, etc. in the vacuum hose- to- recovery tank part of the vacuum system.

"Pure" air weighs less and has less restriction via friction against airways than humid air (much less a mixture including soils as well as cleaning solution). The lighter (less dense) the recovered air / fluid stream, the more efficient transfer rates become(higher CFM). With that set of circumstances alone, the actual CFM capability would vary from job to job... even from one part of a job to another.

Hard numbers are at best, educated guesses, taking into account all of the possible variables... at worst, they're pure conjecture...

Taking this into account, it seems to me that using an instrument to gauge a system's airflow efficiency is only useful if you have a set of numbers to compare the results to. Then you could say with some degree of credibility that one is x% more efficient than the other... but that's as far as you could go, because there can be no true standard to represent the variable air / trash mixture that truck mounts deal with on a daily basis...

 

[Larry Cobb]

First of all, we need to correct a statement:

"Pure" air weighs less and has less restriction via friction against airways than humid air

The addition of water vapor to air (making the air humid) reduces the density of the air, which may, at first appear contrary to logic.

This occurs because the molecular mass of water {18} is less than the molecular mass of air {around 29}. For any gas, at a given temperature and pressure, the number of molecules present is constant for a particular volume. So when water molecules (vapor) are introduced to the air, the number of air molecules must reduce by the same number in a given volume, without the pressure or temperature increasing. Hence the mass per unit volume of the gas decreases, hence the density reduces.

Two additional factors also significantly reduce the density of the airstream:

1. Increased Heat of the TM reduces the density of the air and water vapor. It also aids the transition of water liquid to water vapor.

2. The reduced pressure of the air/water vapor due to the vacuum generated by the TM. This also aids the transition of liquid water to water vapor.

Soil and detergent particles do increase the density, but I don't think that anybody can argue that the effect is more than offset by the greater mass of the water, which reduces the density as it transforms to vapor.

The new CFM flowmeter we use @ Cobb Carpet Supply is a industrial rotary-vane device with sapphire bearings. While there are always some variables affecting the accuracy, I think it is more accurate than the other devices being used in our industry.

We are using it for comparing restrictions in the entire vacuum system and it has finalized our selection of a new series of 2.5" and 3" stainless silencers.

Wand airflow designs are another area where it can distinguish between CFM claims and reality.

Larry Cobb
Supporting Member

 

[Duane Oxley]

"Soil and detergent particles do increase the density, but I don't think that anybody can argue that the effect is more than offset by the greater mass of the water, which reduces the density as it transforms to vapor."

It's variable... As I said, a really dirty job will have more recovered soils.

I read what you'posted here... water, becoming vapor, weighs less per unit of volume than dry air.... I can go along with that, because I read the same thing in the Wikipedia page you cut and pasted from about it....

But, it seems to me that you're implying that some kind of "minus reading" results, that, even though soil particles weigh substantially more and do not vaporize, they can, at most, only "fill in the gap", so to speak, created by the vaporization of water. And I do have a problem with that one. To be honest, I'm not sure why just yet. I need to ponder that one a bit... There's a question that arises, regarding the process of vaporization, vs. the end result of it...

But here's another way of looking at it. Hydrogen, or any "lighter than air" gas, rises, because it's "less dense" by comparison. By inference of what you've posted above, we should be able to fill a balloon with humid air and it will rise... and we know that it doesn't... and the chance of it rising, I'm sure that no one can deny... should actually decrease as the air becomes more humid...

What comes up for me as I think about this is related to the term, "saturation", that Terry used above. He used it in another context, I think, but still, the concept applies here...

At 100% RH, the air is "saturated" with water vapor. And yet, at less than 100% there are still droplets present on surfaces... not vaporized.

And then, there's the heat factor to be considered. Under vacuum, the temperature should drop, if I'm not mistaken (since compression causes a rise in temperature, it's opposite, "vacuum" should cause the opposite...), which will not result in a decrease in density, but an increase. Cold air saturates faster than warm... it can "hold" less moisture.

Maybe we ought to consider the difference between "relative humidity" and "absolute humidity" here...

Your statement seems to imply that you're assuming 100% vaporization... While that is a stretch, IMO, due to reasons that i stated above, there's also the variable of flow rate of the recovered fluid to be considered. A high- flow system (like a "standard" #6 jet allows for, much less a higher flow one like Mikey's #12 jet configuration) would, by definition, have more fluid to be recovered... and less chance of such a thing as "complete" vaporization... a variable to be considered.

It may be more appropriately- applied to a lower- flow system... like an entry- level heat exchanger with #3 or #4 effective jet size, running at 300 PSI... effectively 150 PSI ATW...

Still, instruments do give a reliable way to compare two or more situations that have known and understood variables...

 

[Larry Cobb]

Duane;

And then, there's the heat factor to be considered. Under vacuum, the temperature should drop, if I'm not mistaken

When I grab the wand on the TM's we operate, the tube is definitely hot.

Maybe, there are some out there where the wand is cool ....

running at 300 PSI... effectively 150 PSI ATW...

I hope we are not using TM's with 150 PSI at the wand ....

Also, take a look at cloud formation. They rise in the air due to lighter density.

Larry Cobb
Mikey Board Supporting Member

 

[truckmount girl]

Duane nailed it. LIFT has a huge effect on potential CFM. It is NOT always a directly inverse relationship. You can have more of both. Both are also different depending on WHERE in the system you measure them.

In other words, if you measure at the truck it will be different than where the hose joins the wand, which will be different than across the lips of the wand. It is not a stable measurement throughout the system. Also, it will be different when the wand is off the carpet than when cleaning.

The place it matters the most is across the lips of the wand, in the working position. UNFORTUNATELY it is impossible to measure here because of the shape of the wand head, so we must measure other places and use other means to measure the effectiveness at the wand/carpet interface.

It also must be noted that many test water recovery by using a flood tank, like they use to demo the Water Claw, this is an excellent evaluation for a flood tool, but not a cleaning tool. A tool which pulls more water from below the carpet backing requires lift, a tool that is built for removing more water from face fibers needs more CFM. Evaluations of tools used for cleaning (like glides) should be evaluated using cleaning procedures.

We ran into this as some people tested various glides in a Water Claw tank and reported that holes did not recover as much water. We knew from experience that hole glides recover more moisture while cleaning...so began to investigate why they were getting those results. What we concluded is that for FLOOD work, more lift needs to be communicated deeper PAST the carpet, requiring larger holes. For water contained in the face fibers more CFM velocity, from smaller holes dried the fibers much more efficiently. So the ideal glide for flood work is not going to be the same as the ideal glide for cleaning.

Take care,
Lisa

 

[Duane Oxley]

Larry...

I know "all about" heat through a wand pickup tube. I cleaned carpet myself for 8 years, using high heat / high flow systems similar to what I build today... I had a callous on my hand from running at 230- plus ATW, that I had to grind off with a pumice stone every couple of weeks or so...

The temperature at the wand head is hotter than in the tube, which is hotter than in the vac hose, etc... So there's a constant cooling that occurs as the stream travels from the carpet.

Yes it's hot, but, as soon as the flow of just- hot liquid reduces (for instance, on a dry stroke...) the wand cools virtually instantly... within a second or two... to the point that it can actually be cool to the touch, depending upon which wand it is. (Thicker wall diameter of some wands causes slower cooling... an old Prochem is one such wand... so that it may take a bit longer...)

Regarding the 150 PSI Comment...

Most truck mounts, as you know, use 1/4" ID hose for solution. But apparently, what you don't know (based upon your statement), is that there is a pressure drop through such a diameter hose, that's dependably 150 PSI and as much as 200 PSI or more, if live reels are used and 200 feet is in line, by the time it's delivered to the wand jet(s), and assuming a #6 jet size or equivalent.

...Granted, the system pressure gauge doesn't show this, but you have to look a little deeper to become aware of it...

...Try putting a pressure gauge at the wand quick disconnect and you'll see... I did that one back in the 1990's...)

The net result is that, for instance a #6 jet at 600 PSI ATM ("at the machine"), is really "seeing" 400 to 450 PSI, meaning that (I'm doing this from memory, but I'm reasonably accurate here...) instead of the 2.1 GPM you'd expect, it's really flowing about 1.5 GPM...

...So, "Yes", those little "entry level" systems running at 300 or even (Gasp!!!) 400 PSI ATM, are really delivering 150 to 200 PSI... if they're running a #6 jet. (Just as a larger jet will reduce delivered pressure, a smaller one would increase it, of course, since the flow from the pump is a constant.) I haven't done a study with a jet size equivalency of less than #6, because I don't recommend a smaller- than- 6 size.

That's why I get miffed / amused at the jet size "games" some manufacturers play... Virtually NONE of the other (other than Accelerated, I mean...) manufacturers I know of, except Shawn York and (believe it or not...) Little Giant, mention flow rate in their temperature claims...

 

[Dolly Llama]

"Virtually NONE of the other manufacturers I know of, except Shawn York and (believe it or not...) Little Giant, mention flow rate in their temperature claims"

Steamway always has too
if i recall right, it's 250@2.1gpm

..L.T.A.

 

[Duane Oxley]

Okay, thanks, Mr. C, I stand corrected. And I can't say that I'm surprised that SteamWay mentions it... they have nothing to hide with their kero systems, in terms of flow vs. temperature...

When I first tested the new exchanger that I designed, I was surprised to see that it "only" got 125 to 140 degrees F, at 1.5 GPM. (I used a short hose and a #6 jet, at 600 PSI, which I've always used as "the" standard.) Then I considered a couple of things... Input temperature was about 60 degrees, so the net rise in temperature at 1.5 GPM was about 70 degrees.

The point is that, in order to have real- world figures, I had to look at the flow rate itself. If I would have used a #4 jet, and run the test at 800 PSI, I would have had about the same flow rate, so the temperature would have stayed virtually the same...

There's more to the story on the final temperature (for instance, that test was with a single exchanger, with no delay in through-put and no added recirculation for more heat gain). But that's better left for another thread.

 

[Greenie]

BRAVO!

Other than the chest pounding this has been an excellent thread.

only thing missing is how many BTUs you can capture from one horsepower of internal combustion engine exhaust.

This thread is surely headed for Popular Mechanics.

 

[Mikey P]

Actually its Outhouse worthy as well..

 

[Duane Oxley]

only thing missing is how many BTUs you can capture from one horsepower of internal combustion engine exhaust.

Engine exhaust alone... or all things that it powers in the process as well...? (I'm thinking of blower exhaust powered by the motor, radiator heat from the motor, radiated heat from the motor, etc.)

Years ago, in another conversation I had with a heat exchanger manufacturer, he stated that all you could get from an 18 Vanguard was 65,000 BTU's...

But, if you really look into it, you'll see that an 18 Kohler actually generates more heat...

Hmmmm......

 

[Larry Cobb]

Greenie;

1 gallon of gasoline can generate 125,000 BTU of energy.

Of course, some of this energy is used for powering the devices operated by the engine.

At 2 GPH, you have 250,000 BTU/hr. If 1/2 of that can be recovered, that is 125,000 BTU of heat/hour.

Larry Cobb
Mikey Board Supporting Member

 

[Greenie]

That's just it Larry:

"If 1/2 of that can be recovered, that is 125,000 BTU of heat/hour."

It's a guess.

I would like to focus more on the output of 1 hp.

 

[Guest]

Where is the sizzle

Product, in this case the machine and it's lift, is the product. What about the other 6 principles. Don't know the new 6 principles, try the Marketing principle videos (http://ecommerce1.securesites.com/store ... rketingDVD)
People care about the vacuum and all the other stuff associated with your product, but in reality it is only 14% of your marketing mix. So, stress about the 14%, and ignore the 86%.
Fast Eddie, this comment is not targeted at you, but some of the dumbest comments I read after the post.

 

[Duane Oxley]

Larry...

The 65.000 BTU statement from the guy was accompanied by a further statement that pulling more than "X" (the 65.000 BTU figure for an 18 I mentioned, for instance) would cause the motor to run "too cool". I'm guessing that he had exchangers mounted "on" the motor, and that having them further away would offset that phenomena.

Taf:

I agree with you, but the scope of this thread isn't about how to market systems. Believe me, there's a lot of focus on that as well. I see things like ergonomics (lack of clutter, ease of access to controls), simplicity, compactness, symmetry of appearance, ease of maintenance, performance to spare (so that it performs well over the years, in spite of losing some performance capability due to wear and age...), and other factors, as important.

But that wasn't the topic here...

 

[Greenie]

Taf, get your butt over to "Two rooms $12.95" where you belong.

 

[Guest]

This has to be my favorite thread on this board .

 

[steve frasier]

I just went to 17" from 14" with a different machine

I use a hybrid glide and it can be hard to move on some plush carpets, the air is really pulling through the wand

an unglided wand would not be possible to use without punishing yourself

I tried 17" with a 5mp and 49 hp, it wasn't enough and the machine would bog down

 

[FastEddie]

Wow, I forgot how good this thread was. Tons of great info.

 

[RichardnTn]

Duane, With a machine using 2 gph gasoline and let's say that 1/2 of that, 125,000 BTU's, is lost in heat, at the blower and the exhaust, how much can a
person expect to capture with exchangers..... seems that diverting hot water to a supply tank would help to create greater temps. I have thought of putting an exchanger on my Predator and then running the water to the heater....would save a lot of propane and run much hotter...Richard R

 

[Guest]

Richard, sure a HX might save you money on LP but it would add alot of head ache also . Personally id rather go all LP or all HX.

Jeff

 

[FastEddie]

I personally think liquid cooled engines with coolant H/X's then LP post heating is the ticket for a hot slide-in.

 

[RichardnTn]

Hey Jeff, Your probably right....a couple of manufacturers use a HX as a preheater.....

Ya ever get over this way, stop in and we'll "chew the fat." Richard R

 

[Guest]

mmm fat. Add some bread to sop it up and im there.

 

[RichardnTn]

Jeff, Need any installs over this way...let me know...RR

 

[Steve in Omaha]

Mutha!

Great thread, many very smart people present.