Something i discovered today...

[crankbender]

Originally posted by Defiant
An interesting shovel load.

Less time next to heat = less heat absorbed.

Less time in radiator = less heat radiated.

Less heat absorbed and radiated = more heat at source.

This is way too funny....

You are neglecting the changes in the convection coefficient and the fact that the water spends the same ammount of time next to each no matter how fast it flows....I don't know about you but i don't have a crap load of air in my cooling system.

Don't look at the water in little parts. look at the entire system.

 

[crankbender]

After reading through again it is apparent that I may have come across as an arse. I did not intend to do this I am just trying to teach you something.

Instead of insisting that you look at it my way which IMHO is correct I will approach the problem from a unit volume traveling through the system like you are thinking

A unit of water beings flowing through the block with a very restrictive thermostat and spends 30 seconds in the engine block. During this time energy is added to the water at a given rate that is dependent on temperature and convection coefficients. Lets say it absorbs 1 unit of energy. The water then flows to the radiator and spends 30 seconds there. During this time because of equilibrium we can say it has to loose the unit of energy.

We have a net transfer of 1 unit of energy during the minute.

Now imagine that we remove the thermostat. This time the unit of water only spends 15 seconds in the block. However because the convection coefficient is increased if we just make the incorrect assumption (this is wrong but will show the point) we will transfer energy a little faster. This means we pick up say .75 units of energy. The water then flows to the radiator and releases this .75 units of enerby

We have a net transfer of .75 units of energy during the 30 seconds.

If we neglect the time it does appear that we have transfered more energy with the slower flow but we can't neglect time. So we correct for it

system #1 1 unit of energy per minute
system #2 1.5 units of energy per minute

Here it becomes apparent that the faster flowing system has lost more energy.

I have never intended to make anybody look bad or stupid. If you are interested in the discussion it shows that you want to learn and as such are doing the correct thing. Being ignorant is human...to stay that way is foolish.

set3422: I am not at all saying you are dumb just saying you didn't explain your point correctly. What I thought you were saying might not be what you were saying please try and explain better.

When you do remember that you can not neglect the heat transfer as all rotational energy added to the system gets turned into heat and must be convected off in the radiator. The flow velocity (once at equilibrium) is not changing with time and the net energy change based on it is zero because of this. To understand this place the control volume boundaries in the metal surrounding the fluid. There can be no boundary work as the boundary is not moving. The pressures are static at equilibrium, and the temperatures are constant so there can be no energy storage changes in the system.

Do yall understand what I am saying here or should we open up a cooling system theory thread. Would it be helpfull if i wrote a tech article on the operation of a cooling system?

 

[MNGSX]

Originally posted by crankbender
The people who say this stuff don't often understand heat transfer.

I don't think you understood my post.

I was for increasing flow via the bigger thermostat.

I don't think it will do to much with the stock system but a fluidyne would work quite well if you can move more water thru it.

Moving faster does mean less time in the radiator but it will come out that AL one cooler than the stock radiator anyway. So why not pump cooler water thru at a faster rate.

Also some engines cooling systems function fine without a thermostat and some don't. It's been a while since for me with carbed V8s but I remember having restrictors in place of the stat I removed on one car and another with a different engine that worked just fine with an empty thermostat housing.

 

[Defiant]

Originally posted by Wobble
according to your theory.. the smaller the stat the cooler the car would run right?? water would move slower right? more time to heat more time to cool right?? so i should use as small of stat as possable because my car wil run cooler right??

No. Once you reach the compromise between the greatest latent heat absorption of the coolant, and the most efficient heat rejection by the specific radiator, you're at peak performance where the lines cross. Both will be running at less than their optimum capability.

the situation you describe would be the case if maby you used NO thermostat..

Which introduces flow turbulence and pump impeller cavitation issues. Molecular boiling of the impeller blades = bad.

but what you forget is that the stat opens and closes.. the water STILL stays in the block a long time but WHEN it gets hot it is evacuated quicker and replaced with cooler water quicker.. so you dont get as big of heat spike when getting on it.. if the water isnt absorbing enough heat (as you claim).. it wont be warm enough to trigger the stat to open.. and would stay put until it got hot enough to open..

The thermostat is dynamic and infinitely variable through its range of operation. It's also damped by the response time of the expansion element. "Getting on it" and coasting don't make it slap open and closed.

 

[Defiant]

Originally posted by Enigma_Man
So... according to this if I make the air flow slower through my intercooler, it'll absorb more heat?

Chalk and cheese. You have an endless amount of air to run across the intercooler and the radiator, because they're drawing from an open-ended source. You won't at road speeds in non-racing situations, but you can find a point where a radiator's turbulence will reduce flow through its cooling surfaces. There will be a point at which more airflow across a tube-and fin radiator will not increase heat rejection.

If you throw a lot of water past the heat source very quickly, it will cool it very well.

If you have an ocean, you can cool a volcano. However, you have two gallons in a DSM. Once you get the coolant moving quickly enough that it eddies around hotspots, those spots will boil and create a steam pocket, insulating them from efficient heat transfer.

 

[Defiant]

Originally posted by crankbender
After reading through again it is apparent that I may have come across as an arse. I did not intend to do this I am just trying to teach you something.

No, fiddle. It's just internet chatter, and not seeing one another makes it tough to express the emotional aspects of the conversation.

Which doesn't take away from your mother's wearing of combat boots.





I wouldn't be very Defiant if I just went along with what anyone said.

:laugh:

 

[crankbender]

Which doesn't take away from your mother's wearing of combat boots.

There jump boots foo....gosh don't you remember your gf buying a pair with her?

If you have an ocean, you can cool a volcano. However, you have two gallons in a DSM. Once you get the coolant moving quickly enough that it eddies around hotspots, those spots will boil and create a steam pocket, insulating them from efficient heat transfer.

The flow velocities involved with the water pump are so slow compared to this point. Oh yeah you want the eddies...water conducts like shite so you have to get it to mix for effective heat transfer.

Which introduces flow turbulence and pump impeller cavitation issues. Molecular boiling of the impeller blades = bad.

This isn't an issue because the speed of the impeller is controlled by the engine. You will have less cavitation tho with easier flow...however this cavitation is not related to the boiling you spoke of which is much more prevelant in bladed fan setups. Water pumps are set up so that if you cap the flow they cavitate on purpose so you don't get a bunch of pressure buildup. This is accomplished because the water in the rotor doesn't leave.

Also some engines cooling systems function fine without a thermostat and some don't. It's been a while since for me with carbed V8s but I remember having restrictors in place of the stat I removed on one car and another with a different engine that worked just fine with an empty thermostat housing.

This is because running your engine too cool is a bad thing. The engine is made to operate at a given temperature range. No thermostat can be bad...a thermostat at the same temp range that has more throw is "almost" never bad.