Supercharger Inter / After cooler 1

[finman]

I've checked the FAQ's and Keywords but still can't find what I need, apologese if you guy's know better.

I have an idea that I'd like to try for a water cooled Intercooler for a supercharger. I have access to a thermal design engineer to assist my project but I have no idea of what temperatures I'll be seeing downstream of the supercharger.

Can anyone advise???????

 

[patprimmer]

It all depends on boost pressure plus compressor efficiency.

On a system with a Roots blower pumping 30 psi with methanol used as the fuel, and it is added before the blower, 90 deg C is fairly typical. This would be much higher if the fuel was added downstream, and somewhat higher if petrol was the fuel and added upstream.

Regards
pat

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[overrange]

A water cooled aftercooler is available for the Eaton SC 3.8L GM engines. If I can locate the URL, I'll post back. Grand Prix GT array of hop up parts. The specs on that unit might shed light on your design.

Dave at USI

 

[SBBlue]

Here's a bit more on Pat's supercharger;

If you have a 100% efficient compressor, and an ambient temperature of 80 deg F, and a boost of 30 psi, the temperature of the air coming out of the supercharger will be about 281 deg F.

If instead of a 100% efficient compressor, you are using a Roots supecharger which is about 50% efficient, the temperature of the air coming from the Roots unit will be 479 deg F.

As Pat pointed out, adding fuel to the air before the supercharger will decrease the temperature somewhat, since a portion of the fuel will vaporize and cool down the air.

 

[Warpspeed]

The biggest problem you will face is the intermittent nature of the operating conditions. The system NEVER reaches steady state, so you cannot just plug some figures into a formula.

Try to imagine what happens when the whole system heat soaks in a traffic jam. Then you madly accelerate up through the gears, with a gear change every three seconds.

Initially a lot of the heat is absorbed by the blower casing and pipework, so the temperature spike you expect never actually happens, it just gradually builds up. But it cannot build up for very long before you have to get back off the throttle.

Really, data logging and some testing is the only way you are going to get some realistic numbers to play with.

 

[finman]

Okay Guy's, Many thanks for the help.

My query was to determine the worst temperature scenario in order to add some confidence to our tube to tube plate jointing system.

Our matrix will be superior to the brazed options but executing the tube joint was the difficult bit, welding is not an option!

If there are any advances on 479f Please up date this forum.

Once again thanks for all your help.

 

[spereira]

hi Finman,


you can use the adiabatic compression equation for ideal gases to have an idea of the temperatures after air compression:

Tdicharge=Tinletx(Pdischarge/Pinlet)^.283

where .283 is a constant for air (other gases have different constants since it's a function of its heat capacities)

be sure to introduce temperatures in ºR (ºR=ºF+460) and pressures are absolute pressures. for the example given by patprimmer you should have:

Tinlet=80ºF=540ºR
Pdischarge=30+14.7 psia=44.7
Pinlet=14.7 psia

so you get Tdischarge=540x(44.7/14.7)^.283=737.9ºR=279.7ºF very close to the result he mentioned.

but this is assuming 100% compressor efficiency.

for a given compressor efficiency (eff)discharge temperature is given by:

Tdischarge=Tinlet(ºF)+((Pdischarge/Pinlet)^.283-1)xTinlet (ºR)/eff

again for the example of patprimmer you get:

T discharge=80+((44.7/14.7)^.283-1)x540/.5=479ºF

for further info, take a look at this link. it should help:

http://www.thrashercharged.com/L67_htm/intercooler.shtm

regards,

Susana

 

[finman]

Thanks Susana, this stuff and the link is just great, I owe you one.