Crazy Dream: Bleed cold air from A/C into engine

[eljefino]

Originally Posted By: Burt
Originally Posted By: NHGUY
Is the ambient air that's forced in at high speed/velocity THAT much warmer? Imagine high performance driving in the winter.Now there's temps of 0-30 degrees F....do you pick up that much power and fuel economy?


It isn't the velocity that increases the temp, it is the compression. look up adiabatic compression.


I thought it was that, but also that more timing could be run without knocking, as the cold air sucked heat out of the process.

 

[Shannow]

Originally Posted By: A_Harman
"Will the system for refigerating the charge air absorb more power than is added by burning the additional fuel enabled by higher intake manifold density?"

Unfortunately, I don't know doodly-squat about how much power refrigeration systems absorb for a given amount of cooling and mass flow. But I can give some ballpark numbers for engine airflow conditions. Let's say that we have a 2.0L turbocharged engine running 15psi boost with a 90% effective intercooler on a 77F day. At 5500 rpm and 30% thermal efficiency, the engine would produce 302 HP. The heat rejection from the intake airflow of 1600 lb/hr would be 1011 BTU/min.

Then add a refigeration system to the intercooler loop with an assumed media temperature of 30F, and keep the same assumptions for engine performance as above. Intake mass flow would increase to 1732 lb/hr, and intake air heat rejection would increase to 1387 BTU/min. Power would increase to 327 HP just by decreasing the intake manifold temperature, an increase of 25 HP. I don't think that a refrigeration system would absorb all that additional power. Are there any HVAC engineers out there that can ballpark some numbers on the refrigeration system?


OK, I'll be your huckleberry.

One of my favourite books is The Efficient Use of Steam, by Oliver Lyle (1947)...he mentions that utilising heat pumps where a latent heat advantage can be gained should never be discounted.

I was hasty in my comments previously.

This is far more complicated, involving not a latent heat process, but a non linearity in terms of the combustion process.

Can you throw me two data points with a fixed max airflow mass and different intake temps

 

[Jetronic]

Originally Posted By: Shannow

Unless there's a latent heat process involved, you can't gain more shaft power than you put into the AC compressor.


you could keep knock at bay, given a big enough AC system. But how much is there to gain from a bit more turbo pressure or a few more degrees advance?

I suppose this idea was conceived for use with carburetted turbo engines, to keep the weather influence to a minimum.

 

[Jetronic]

Originally Posted By: Burt


I always wondered though, if cooler air means more hp, why doesn't my rate of acceleration increase as it gets cooler? Seems like if you get 10% more hp by chilling intake to 30 degrees, then the effect should be even greater at zero or below?


The mass of the air your car has to be pushed through also increases.

 

[A_Harman]

Originally Posted By: Shannow
Originally Posted By: A_Harman
"Will the system for refigerating the charge air absorb more power than is added by burning the additional fuel enabled by higher intake manifold density?"

Unfortunately, I don't know doodly-squat about how much power refrigeration systems absorb for a given amount of cooling and mass flow. But I can give some ballpark numbers for engine airflow conditions. Let's say that we have a 2.0L turbocharged engine running 15psi boost with a 90% effective intercooler on a 77F day. At 5500 rpm and 30% thermal efficiency, the engine would produce 302 HP. The heat rejection from the intake airflow of 1600 lb/hr would be 1011 BTU/min.

Then add a refigeration system to the intercooler loop with an assumed media temperature of 30F, and keep the same assumptions for engine performance as above. Intake mass flow would increase to 1732 lb/hr, and intake air heat rejection would increase to 1387 BTU/min. Power would increase to 327 HP just by decreasing the intake manifold temperature, an increase of 25 HP. I don't think that a refrigeration system would absorb all that additional power. Are there any HVAC engineers out there that can ballpark some numbers on the refrigeration system?


OK, I'll be your huckleberry.

One of my favourite books is The Efficient Use of Steam, by Oliver Lyle (1947)...he mentions that utilising heat pumps where a latent heat advantage can be gained should never be discounted.

I was hasty in my comments previously.

This is far more complicated, involving not a latent heat process, but a non linearity in terms of the combustion process.

Can you throw me two data points with a fixed max airflow mass and different intake temps




If the boost pressure is lowered to keep the same mass airflow at the lower intake manifold temperature due to refrigeration:
boost = 12.7 psi
IMT = 50 F
mass airflow = 1600 lb/hr
Horsepower stays the same at 302.

Original case was:
boost = 15 psi
IMT = 94.6 F