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NewClearSports

Sooooo Very Very HOT!

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What,s up with the crazy heat the tunnel produces?
Is this normal? If so how do the rest of you Instructors out there deal with it?

Here is the senario.

Nice Spring day in Niagara Falls, maybe 65 - 70F
RED BULL buys 2hrs for all the Air Raid Girls ;)
OH And talking about HOT, this was 45 of the most smoking hot girls on the planet!
We have 3 Instructors on hand. I take groups 1, 4, and 7, with 7 being the last group.
Group 1, no problems, group 4, starting to get hot, guessing at 100F, by the last group it was an oven in there. I'm betting it was 120 - 125F.
I wasn't able to make it through my session without several stops to just get out of the heat and drink some water. By the end I felt sick, very sick. This is the next day and my sinus and throut feel burnt from the inside.

So obviously, I suggested there might be a problem with the tunnel. I,ve been told it just needs to be calibrated for the warmer weather, as the unit was set up in February at sub 0 temp.

Somehow I don't think that alone is going to fix this problem.

I know the friction of the air creates some heat, but I don,t think this kind of heat is from that, I think the engine is getting really hot. Will calibrating it really make it run that much cooler, I guess I will have to see.

This is a Flyaway style tunnel.

Any input is appreciated

cheers

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I have been in 1 Flyaway tunnel. I was in Pigeon Forge in the middle of July when it was 101 degrees outside. I had been told that the Flyaway tunnels can get hot inside, so I was prepared for that. And while it was like a sauna in the tunnel, I was not prepared for the AT LEAST 130 degree air of the actual air column. All exposed skin felt like it was being damaged and burned and my husband had raging respiratory issues for a few days afterwards. It makes me admire the folks that stuck with tunnel flying when these were the only tunnels available. But, you might be out of luck. From what I hear, recirculators without any sort of intake can tend to get uncomfortably warm, especially during the summer. Hopefully lots of hydration and some conditioning will keep you from feeling so sick in the future.
jenn
Tunnel Junkie Since November 2005! ;o)~
TPM #46
Paraclete XP TPM Delegate

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More than Friction, I think any motor(s) will produce more heat than you want. Think about the engine in your car sitting in the back seat. Even with the windows down, you are going to cook!!
Seen this manager (not sure why crazy), dump a cup of water on the motor cover(when it was off), it was so hot, the water made a scream as it bounced off. That is pretty hot.

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That sounds par for the course with this style tunnel. Here in Vegas we have close to 100 tons of AC pumped into the tunnel and by the end of a busy day it will still get so hot that it feels like your skin is on fire.

Your body will build a tolerance to the heat. When we're training new instructors we purposely take them in the first few times when we know it's painfully hot so we can see who can hack it. We've had trainees have to run out of the tunnel to vomit from heat and exertion.

It sucks, and it will suck the energy right out of you...but for some reason it never ruins a first timer's flight. They'll complain about the heat but still come out with a smile talking about how it was totally worth it.
Brad Hess
Manager
Vegas Indoor Skydiving

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>but I don,t think this kind of heat is from that . . .

A closed circuit unvented tunnel is basically a closed system. The Perris tunnel takes about 600kW (half a megawatt) during operation. Most of that energy stays in the tunnel as waste heat, so you effectively have a half-megawatt heater on whenever the tunnel is operating. Conservation of energy and all.

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Billvon is right, the conservation of energy, that is it gets converted from one form to another, in this case its electrical energy to kinetic energy (movement of the air). No conversion is 100% efficient so some of it (in this case) is converted to heat.

So it's not quite like having a 600kw heater more like a
600KW * (100 - efficiency%) at 80% this would be 120KW

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I've clearly been spoilt :P I've only ever flown in either Bodyflight (1500Kw of cooling), AirKix (recirc with vents to use outside air to cool it down, Orlando and Spain (both non-recirc but use outside air). It was over 100 in Spain just using the outside air - I'd hate to have a recirc in that climate. [:/]

Sure it's been hot (seen 100+ degrees in Bedford on monster hot, monster long days, where we've used maximum power most of the day) but never unbearable. That would truly suck instructing in that heat. Good job to you guys I say.

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>So it's not quite like having a 600kw heater more like a
>600KW * (100 - efficiency%) at 80% this would be 120KW

Where do you think that other 480kW goes?



the Alaskan tundra?

or Cleveland. Hard to tell.

...
Driving is a one dimensional activity - a monkey can do it - being proud of your driving abilities is like being proud of being able to put on pants

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> It goes into 480kW of air movement

OK. So you have run the tunnel for an hour. That's 600kWhr of energy that you pumped into it. Then you turn it off and the air stops. We've agreed that 120kWhr of energy was lost as motor/inverter inefficiency.

Where did that other 480kWhr go? After all, since you can't create or destroy energy, it went somewhere.

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> It goes into 480kW of air movement

OK. So you have run the tunnel for an hour. That's 600kWhr of energy that you pumped into it. Then you turn it off and the air stops. We've agreed that 120kWhr of energy was lost as motor/inverter inefficiency.

Where did that other 480kWhr go? After all, since you can't create or destroy energy, it went somewhere.

Back into heat. The friction of air circulating in the tunnel against the walls, air mass against air mass, results in heat. A frictionless tunnel would continuously circulate air when the tunnel stopped, but that's not true. The air slows! The energy got converted very efficiently into heat by virtue of friction. So still (near) 600 kilowatts of heat, at the very end, one way or another!

Putting the motor out of the airstream and cooling it with a separate airstream would probably help, but would probably complicate the windtunnel design significantly and hurt efficiency! Increasing efficiency (more energy into actual air motion and less energy wasted in motor) is another way. But there comes limits.

I'm told best to go early in the day, when the tunnel is not hot, or go during colder weather. Then it's fine. For the short amusement rides, it's a non issue, but for training it becomes more an issue...

FWIW, I've never overheated in a Skyventure type tunnel, whether it was cold or hot outside. The high power recircs with venting can equallize to almost equal the outdoor temperature, because they have so much excess power, that they can vent a significant minority of the air on every cycle -- This results into total air replacement many times per hour. So that it never seems to get noticeably hotter in the chamber than outdoors, if they're operating the vents ... All that excess heat is vented from a modern Skyventure recirc. If somebody complains of heat, they adjust and the chamber cools down pretty quickly - a nice convenience of a high power ventable recirc. Of course, in the winter, the extra heat is helpful, so the vents are adjusted until the chamber is a comfortable non-sweating non-freezing temperature, no matter how cold it is outdoors... The tunnel does lose efficiency (more KW to stay at the same speed) the more open the vents are, but there's plenty of excess power in a high-powered recirc, and the motors are very efficient to begin with to the point that only a tiny amount of venting is required most of the time...

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Eh? Maybe where you live and fly ;) I wouldn't call >25% a "tiny amount" of required venting - and we've not even got into summer yet here :)
Oh and I agree they can open the vents to cool the tunnel further - but shutting down to do so and then starting back up *can* be a pain...

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Eh? Maybe where you live and fly ;) I wouldn't call >25% a "tiny amount" of required venting - and we've not even got into summer yet here :)

Actually, I didn't say opening the vents to expel 25% of the air per cycle -- Sorry about not being clear...

Please correct me if I am wrong but it is my understanding Skyventure can continuously operate while the vents are open a tad. No need to shut down the tunnel.

A tiny opening can still replace the air rather quickly enough to keep it almost equal to the outdoors temperature, as well as the SkyVenture has more than 25% "headroom" - i.e. It'd takes a lot of venting to slow 150mph down to a 120mph -- and I don't even know if SkyVenture vents can be opened that big to hurt the airflow by that margin. Still plenty strong enough with enough performance to keep flying, even if the vents are always open a bit, no? Imagine that the recirculator becomes a 99% recirculating, 1% non-recirculating (pick a small number - % of air vented versus % of air recirculated, per cycle) -- just enough to keep it cool. No need to shut down the tunnel... Recirculators, in theory, are more efficient than non-recirculators.

I don't remember the exact terminology used, but I think terminology used is "inlet" or something. There are two and I understand that a bit of hot air is pushed out somewhere, and a bit of cooler air is sucked in somewhere, replacing a % of the air that is recirculated. It may not be much per cycle, but adds up to a great deal of cooling in what ends up becoming a fairly efficient method of air-conditioning of the recirculating tunnel (but only as far as down to outdoors temperature). Which makes it excellent at keeping at room temperature under most operating conditions which is what I have always perceived... Even in Skyventure recirculating tunnels, they admit a little external air -- even while running. The vents are adjustable, to adjust the amount of adding external air - and to expel stale recirculating air. You see the panels on the left and right sides of a recirculating Skyventure. (link - see square depression with inwards-opening trapdoor flap on the left side in the middle). They behave as a kind of movable flap that can be cracked open a little by remote control by the tunnel operator. Even while people are flying. There's plenty of excess power in a powerful freefly-capable recirculator to not need it to be a 100% pure recirculator, it can introduce outside air at variable amount of small percentages....

I am sure they have specific operating procedures, such as preferring to run the vents intermittently within specific parameters, especially between groups, but it's my understanding airspeed is still capable of going well past bellyfly speeds even with vents open -- it may only need a tiny bit (say, trapdoor vent opened by a mere few centimeters - which makes it hard to see from the ground), if the weather is damn hot.

Just open vent a little more, crank the motor up a tiny %, keep operating, tunnel runs a bit cooler at the same chamber speed -- the slight extra energy more offset by extra cooling of new air from the trapdoor vents. It's my understanding this is all controllable all right at the tunnel operator location... It seems to take them only mere seconds (almost immediate) for the air to stabilize after adjusting the vents and the motor speed, so they can do it pratically "on-the-fly" during hot weather if they need to...

At least in theory anyway - they could even program the computer to maintain airspeed by modulating the motor in parallel to the vents - maybe some of them already do this now. (Maybe someone could chime in about how this is currently being done at some of the ventable recirculators)

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Please correct me if I am wrong but it is my understanding Skyventure can continuously operate while the vents are open a tad. No need to shut down the tunnel.



As far as I am aware, they must shut down the tunnel to change the amount of "opening" of the vents. IE, to change from 10% open to 20% open (or close etc) requires a shutdown.

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A tiny opening can still replace the air rather quickly enough to keep it almost equal to the outdoors temperature, as well as the SkyVenture has more than 25% "headroom" - i.e. It'd takes a lot of venting to slow 150mph down to a 120mph -- and I don't even know if SkyVenture vents can be opened that big to hurt the airflow by that margin. Still plenty strong enough with enough performance to keep flying, even if the vents are always open a bit, no? Imagine that the recirculator becomes a 99% recirculating, 1% non-recirculating (pick a small number - % of air vented versus % of air recirculated, per cycle) -- just enough to keep it cool. No need to shut down the tunnel... Recirculators, in theory, are more efficient than non-recirculators.



Kindof. Do you fly in tunnels with the tunnel on maximum power (or close to it) a lot? In my (limited - 15-20ish hours) experience of a skyventure recirculating tunnel, opening the vents much beyond 20% hinders power considerably, but this is obviously offset against power hindered through heat. Too much heat causes a loss in "lift" whilst opening the vents a lot (to cool all this hot air down) also affects lift. The nicest lift comes from closed vents on a cold day, and being in the first session of the day ;)

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They behave as a kind of movable flap that can be cracked open a little by remote control by the tunnel operator.



Yes - I'm aware of how it works - its a good system to solve this problem :)
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Even while people are flying.

Are you sure about that? In the recircs I've flown in, a shutdowns required. Thats what I was talking about in my original post :)
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There's plenty of excess power in a powerful freefly-capable recirculator to not need it to be a 100% pure recirculator, it can introduce outside air at variable amount of small percentages....

I am sure they have specific operating procedures, such as preferring to run the vents intermittently within specific parameters, especially between groups, but it's my understanding airspeed is still capable of going well past bellyfly speeds even with vents open -- it may only need a tiny bit (say, trapdoor vent opened by a mere few centimeters - which makes it hard to see from the ground), if the weather is damn hot.



Ah - belly fly speeds are fine for sure. As you say, just crack up the power a touch if required, but that might not be even required as the air temperature falls in the chamber.

However, that does bring me onto another interesting point - in that a "vented" recirculating tunnel does loose lift to those vents (if they're open) regardless of the power it's running - belly speeds, maximum power, etc. Thats why you'll notice more power is required the more people you put in the chamber.

It's just one of the great things about Bedford - the more people you put in the chamber, the more lift you get. For example - two 4-way teams both flying on 50% decide to do some 8-way for their last flights - they'd probably want in the region of 45% (perhaps even a little less) when doing the 8 way.

For freefly, thats awesome too - the more flyers ripping it up in Bedford, the faster it gets B|

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Hey, thanks for the explanation....

I knew the tunnel operates with the vents a bit open, but I wasn't aware that to ADJUST the vent, it had to shutdown... (I wonder if that's universally the case for all the Skyventure recirculating tunnels?)

The tunnel always shuts down between groups, so they would have the opportunity to adjust the vent many times a day, between 2 and 4 times per hour, if needed. Seems to be often enough to keep the tunnel cool...

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>So it's not quite like having a 600kw heater more like a
>600KW * (100 - efficiency%) at 80% this would be 120KW

Where do you think that other 480kW goes?



It goes to kil polar bears. :)

Don't forget the compression of the air from the venturi effect.

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I knew the tunnel operates with the vents a bit open, but I wasn't aware that to ADJUST the vent, it had to shutdown... (I wonder if that's universally the case for all the Skyventure recirculating tunnels?)



Can only speak for the ones I've been to, but they both had to be shut down to adjust the luvers (sp?!?!).
Tunnel Pink Mafia Delegate
www.TunnelPinkMafia.com

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The motors generally dont create alot of heat... our motor isnt actually in the airflow either! Heat is generated simply from the air movement friction and compression around the flow circuit.

Sadly the laws of physics mean this will always be a problem which needs to be cooled! Venting and mechanical cooling both have some downsides but its necessary if you guys want to be comfortable! lol

Bodyflight Bedford
www.bodyflight.co.uk

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>So it's not quite like having a 600kw heater more like a
>600KW * (100 - efficiency%) at 80% this would be 120KW

Where do you think that other 480kW goes?



It goes to kil polar bears. :)

Don't forget the compression of the air from the venturi effect.


You will get lower pressure where the people are flying, and therefore cooler air. Bernoulli says fast and low pressure, or slow and high pressure.

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>You will get lower pressure where the people are flying, and therefore cooler air.

If the pressure was lowered enough to provide significant cooling, the walls would collapse on the tunnel. We're talking several PSI for a significant effect.

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The Niagara Tunnel is built with the latest and greatest in technology and can operate as both a closed-air and open-air system. The electric motor is equipped with two large forced air blowers that continually cool it even though it does not give off much heat to begin with. The system is designed so that it can operate in continously without the need to shut down to adjust louvers.

As with any newly built equipment there are always some glitches...this tunnel simply hadn't been operated in the open-air mode yet.

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