Blower Exhaust

[Larry B]

Does anyone know what kind of temps the blower exhaust runs?

 

[XTREME1]

enought o melt cheap vac hose. I know

 

[Lee Stockwell]

Depends on the back pressure of the blower. Very little heat comes from mechanical friction of the blower or its bearings. Usually heat rise should be under 100 F. degrees. Adding back pressure raises heat output...dramatically.

 

[AshleyMckendree]

Depends on the back pressure of the blower. Very little heat comes from mechanical friction of the blower or its bearings. Usually heat rise should be under 100 F. degrees. Adding back pressure raises heat output...dramatically.

Lee is right,

I dont know how hot it was, but I had a tube in shell blower post heater that became clogged, and the pipe from the blower to the heat ex was CHERRY RED one night.

Thats what I got for not having a filter for my blower at the time.

 

[Greenie]

The sheer compression of air as the blower pulls against resistance of a wand on the carpet can make for 250º blower exhaust easily....restricted blowers, especially ones designed with blower HX in mind can run hotter.

Not a place for plastic exhaust plumbing.

 

[Larry Cobb]

Larry;

It depends on the actual load on the blower...
and the efficiency of the silencer.

We have measured 230° as a typical level while cleaning with about 90° in the truck.

Larry

 

[Greenie]

Larry, what blower and TM unit was that?

 

[Larry Cobb]

Greenie;

Dynachem TM with #4MP and 24 HP Honda.
2.5" Stainless Silencer & HX.

Larry

 

[Larry B]

If you hook a blower exhaust HX to a 4.7 for secondary heat is it possible to get another 30-40 deg without air loss from the blower?

 

[Gary Bethel]

A ballpark figure is usually the 36-frame blower delivers 200F. The 47 frame blower 210F. The 59-frame blower will have an exhaust reading of around 220F. Of course those temperatures will vary upwards if there is more restriction. Goes to show that those big blowers do give more heat to use for heating water.

Gary.

 

[Larry B]

Would adding a HX to the blower make enough restriction to run the temp up?

How would this effect the performance of the blower?

 

[MerCrewser]

I bumped my PC 405 Hg up to 16" while I ran my rx20 on nasty commercial restaurant carpet. Unit got HOT. Had no problem maintaining 240 with an rx20 running 10 flow. The truckmount smelled hot, and I was somewhat alarmed so I reduced Hg back to Prochems specs. Blowers get real hot real fast.

 

[steve frasier]

and the pipe from the blower to the heat ex was CHERRY RED

I remember seeing this one night on my 427 BOXXER with no blockage

 

[gasaxe]

Would adding a HX to the blower make enough restriction to run the temp up?

How would this effect the performance of the blower?

it depends on the style of heat exchanger.

 

[Greenie]

If a 47 blower has a 3" exhaust, in theory anything but a full 3" opening and straight plumbing will cause some back pressure and load on the blower, so I would say it's safe to say ANY blower HX cause teh loss of potential airflow.

Now the reality, do you need 450cfm or can you give some of that up for a heat increase....hence todays HX TMs.

 

[Shane T]

Would adding a HX to the blower make enough restriction to run the temp up?

How would this effect the performance of the blower?

it depends on the style of heat exchanger.

It will also depend how close to the blower it is installed.
You can always play around with changing the size of the discharge opening on the exchanger. If it is reduced this will increase the time of duration which the hotter air stays in the shell as well as add back pressure to the blower which will also increase temp.

 

[Larry B]

Thanks for the info so far. More questions to come

 

[MerCrewser]

I'd like to see what a water jacketed blower would do. Blower temps would stay down, but probably wouldnt add as much heat as the blower exhaust hx?

 

[Lee Stockwell]

There are hundreds of blower designs from dozens of manufacturers, many of them water-cooled.

 

[Dolly Llama]

OK, someone help me out with how the restriction thingie can cause decrease in airflow?

Is it because of blow by/air slip (for lack of a better term) on the lobes?

if not, it will still pull/push the same amount of air whether restricted or uncorked, no?
(given the real ristriction is at the wand end, not exhaust)
Just the increased HP required to over come the restriction is all that happens, no?

am i missing sump'um?

the greatest choke point to the vac system is the wand, not on the back end exhaust.
How many CFMs are even possible at 15HG through typical UNglided 14" wand?
Now restrict it even more, and tell me how much CFM is possible thru a hole glide?


..L.T.A.

 

[Lee Stockwell]

Like the weather Larry. Compressing a gas (air) gives off heat.

 

[Dolly Llama]

Like the weather Larry. Compressing a gas (air) gives off heat.

Thanks Lee
(good to see you around the board more lately too)

I can the dig the heat build up thingie and restriction , my question is on the airflow

never mind, i don't want to hi-jack larryB's thread, so I'll start another

..L.T.A.

 

[Larry B]

Its a good question Larry. I also am trying to fi all the info I can on this subject

 

[Larry B]

So if I ad a secondary HX after the blower & its mounted close to the blower with few turns I should get some extra heat with little loss of air movement on the wand end of the system?

 

[Lee Stockwell]

Yep

 

[gasaxe]

if you look at a performance chart for a roots pump it will show max psi or max vac. at a given rpm. Also it will show the volume of air moved (cfm). My understanding is that the final factor in how the pump is ran is the exhaust or pressure side temp. In a 68 urai that magic number is 250 deg. the ratings in the peformance chart are based on a set atmoshperic condition,temp etc. So if you have 2 or 3 psi of backpressure then it will likely require you to run less vaccum in order to keep the egts at or below 250. It is called a pd or positive displacement pump bcause it will move a given amount of air on each revolution. restriction on either side can effect this number as well as the amount of heat generated.
all three 68 urai pumps ive had when ran at 16" vac with less than `1 psi of backpressure would easily see 250+ degrees of egts.

 

[AshleyMckendree]

A system my dad built for me 7 years ago, had only a Tube in Shell heat exchanger off the blower's exhaust, and I would get that "POP n HISS" coming out of the wand all day long.

I never had a temp gauge, but I can tell you I had a quick-connect shaped 2nd degree burn on my arm when I did some stairs and let the wand rest on my arm :shock: