COLD COLD COLD air intake!!
You work in the field, right?
Evaporation= going from a liquid state to a gaseous state
Sublimation= going from a solid straight to a gaseous state without becoming a liquid
Not bad for a liberal arts student 10 years out of college
Sublimation= going from a solid straight to a gaseous state without becoming a liquid
Not bad for a liberal arts student 10 years out of college
Newbie
Joined: Apr 2005
Posts: 62
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From: Atlanta, GA
Originally Posted by 05 Silver RA
negative, compressed gasses are actually the same temperature as the surrounding air. the chilling effect comes when you release the pressure. during the compression phase, the gs and the cylinder it's in actually heats up, sometimes quite a bit. think about it this way: by compressing something, you are actually storing energy.
example #1: paintball gun. As you fire repeatedly, the cylinder containing liquid CO2 gets colder. as the pressure is realeased, the molecules expand, and the liquid vaporizes to its vapro pressure. exothermic reaction, thus cooling.
JJ
example #1: paintball gun. As you fire repeatedly, the cylinder containing liquid CO2 gets colder. as the pressure is realeased, the molecules expand, and the liquid vaporizes to its vapro pressure. exothermic reaction, thus cooling.
JJ
sorry for bein a smart @$$...
i must also add that compressed gases are hotter than normal air especially in this case of forced induction. If this wasn't true the whole development of the diesel engine would not have occurred. Diesel effect is the idea that when air is compressed with diesel fuel the pressure increases the temperature of the air to the flash point of the fuel, which is the reason diesel engines don't use spark plugs. In your case of filling cylinders the compressed gas must cool, but that is because the energy you are adding to the system by increasing the pressure is let off as heat(back to first law of thermodynamics). it eventually cools to room temperature.
Newbie
Joined: Apr 2005
Posts: 62
Likes: 0
From: Atlanta, GA
ok, you got me on the first one, simple typo there.
your second post doesn't make too much sense. filling a cylinder or vessel will, of course, initially create the heat both you and i spoke of, but the vessel will eventually cool to ambient temperature, if no other input is allowed into the system
that's the point, too, of an intercooler. the compressed air is fed through the IC to draw heat off the intake charge.
JJ
your second post doesn't make too much sense. filling a cylinder or vessel will, of course, initially create the heat both you and i spoke of, but the vessel will eventually cool to ambient temperature, if no other input is allowed into the system
that's the point, too, of an intercooler. the compressed air is fed through the IC to draw heat off the intake charge.
JJ
Originally Posted by 05 Silver RA
your second post doesn't make too much sense. filling a cylinder or vessel will, of course, initially create the heat both you and i spoke of, but the vessel will eventually cool to ambient temperature, if no other input is allowed into the system
that's the point, too, of an intercooler. the compressed air is fed through the IC to draw heat off the intake charge.
JJ
that's the point, too, of an intercooler. the compressed air is fed through the IC to draw heat off the intake charge.
JJ
D
Evolving Member
Joined: Apr 2004
Posts: 400
Likes: 1
From: Columbus, OH
Originally Posted by acidandroid
does anyone know the air mass flow rate is at the intake?
like mfr VS engine speed?
like mfr VS engine speed?
A quick sanity check, say a 13:1 afr (way too lean, I know) means 0.02 kg/s of fuel. At about 0.8 g/cc fuel density that's 25 cc/s --> 1500 cc/min or 375 cc/min per injector. The evo has 550 cc/min injectors but we assumed less than peak airflow and very lean, so we're on target.
Suppose we want to cool the intake by 20C, how much heat do we need to get rid of? The heat capacity of air (using Cv, which is significantly lower than Cp) is 720 Joules/kg/C. So we need to get rid of heat at a rate of about 3700 J/s (3700 Watts). The heat of sublimation of CO2 is 5800 J/g so we go through CO2 at about 0.65 g/s (not including the loss from all the other heat it's absorbing).
I'll leave it to an HVAC engineer to figure out how much surface area is needed to dump 3700 Watts with a temperature drop of about 85C (10C air to -75C CO2).
Dave
ok, some of u might understand what i'm talking about here
correct me if i say anything wrong, i'm still a student
ok, basicly.....heat transfer calculation be done with this equation
Q = mdot*CP*deltaT = U*A*deltaT
mdot is mass flow rate of air, cp is heat capacity
U is overall heat transfer coefficient, A is heat transfer area
U is determined from heat conductivity of the pipe, dry ice, and the air, and convection of air
since air is blowing by so fast, convection of air is big, so a correlation is needed
convection of air is derived from air's properties : pipe diameter, velocity, density, viscousity, and some dimensionless numbers such as reynolds, prandt, number and so.....
also heat conductivity of air and dry ice
for a given size of that dry ice box, temperature drop of air can be calculated with all above calculation. then will be able to know how much this dry ice idea can cool down the air and to see whether it's effective for the car or not
correct me if i say anything wrong, i'm still a student
ok, basicly.....heat transfer calculation be done with this equation
Q = mdot*CP*deltaT = U*A*deltaT
mdot is mass flow rate of air, cp is heat capacity
U is overall heat transfer coefficient, A is heat transfer area
U is determined from heat conductivity of the pipe, dry ice, and the air, and convection of air
since air is blowing by so fast, convection of air is big, so a correlation is needed
convection of air is derived from air's properties : pipe diameter, velocity, density, viscousity, and some dimensionless numbers such as reynolds, prandt, number and so.....
also heat conductivity of air and dry ice
for a given size of that dry ice box, temperature drop of air can be calculated with all above calculation. then will be able to know how much this dry ice idea can cool down the air and to see whether it's effective for the car or not
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