Interesting Cooling Idea...

[Kmehr]

So while studying for my cost accounting exam I ran across an example which used a refrigerator as the product, which in turn led me to howstuffworks.com to figure out refrigeration works. Anyways, I got to wondering if anything like refrigeration had ever been used to cool an engine. Does not seem like it would be too difficult to setup and seems like it would be much more effective than a conventional radiator water pump setup. Seems like the problem most face when trying to build power is always heat. Just some food for thought. Let me know what yall think. Funny how cost accounting gets turned into a diesel page post!

[DmaxMaverick]

Refrigeration systems can be (and are, in some cases) used to cool stationary power systems. That's where the usefulness ends. It isn't practical for use on a mobile platform. The current automotive cooling system used is the most efficient available (although the designs could use some improvement, IMO). A cooling system on an engine has one purpose: Move heat from one place to another. Heat is removed from an engine via coolant, and the coolant (and heat) is transfered to the radiator, where the heat is then transfered to the ambient air. This method is far from 100% efficient, which is why, despite our efforts, we still have heat issues. A refrigeration system does exactly the same thing, only with a different medium. However, it is even less efficient, although it may appear to be more effective. In any case, you will still have the heat removed from the engine to send somewhere. If employed similarly to the A/C system, that would be the same place as we are currently sending it: the cooling stack. The size of the refrigeration system required to transfer the heat from an engine would make it enormous, compared to our current approach. It would also be cost-prohibitive.

[Kmehr]

I guess you are right when you think about it, it takes a really long time to cool a refrigerator down from room temperature. Are there fluids which possess heat exchange properties that are unique to that fluid? I guess what I am saying is there some fluid that would be more effective than another in heat transfer? I have always heard that water is the best coolant you can use you just can't use it for too long because it corrodes the internals and can freeze and crack the block. After thinking about this refrigeration thing, it seems to me that there would be more aftermarket research and development on coolants. You never see and add in a magazine for high performance coolant.

[DmaxMaverick]

There are coolant fluids more efficient than water, but not practical for automotive use (toxicity, volatility). Unfortunately, we have to accept the inefficiencies of water/coolant(antifreeze) due to the corrosive and evaporative characters of straight water. Water is the most efficient, least toxic, of any fluid we could use for this purpose, but does have undesirable qualities, as you've mentioned.

The use of refrigerant (freon, ammonia, etc.) is not necessarily more efficient than water. It is ideal for refrigeration due to its ability to remove heat, at sub-[water]freezing temps, and its gas-liquid transition temperature. With water, the same transition range is 212° (at sea level, atmospheric pressure), compared to common refrigerants able to do this at temps well below water-freezing. It becomes less efficient at higher temps, the same as water becomes less efficient at lower temps. And, there is no tangible quality known as "cold". There is only heat. More heat, or less heat, but it's only heat. Absolute zero is the absence of heat. Cold is only a perceived condition of less heat. A refrigerator works the same as a cooling system on a vehicle. It moves heat from one place to another. With a residential refrigerator, it moves heat from the inside of the box to the outside. That's all. This is why stand-alone air conditioners don't work well at all if they can't be ducted (the condenser) outside the room you are in. For the same reason, water (swamp) coolers do work in this situation, but relies on water evaporation for the heat absorption. Water evaporation is dependent on the ambient air's ability to take up the water, which is greatly effected by relative humidity (local saturation). Oh, well. Enough of that stuff.....

What we are doing with our engine cooling is about as good as it gets. We can improve upon the design, but there's nothing we can do about the principal method.

[enormiss]

It is interesting...
Couldn't auto cooling systems take advantage of compression generating heat and the cooling effect from expansion like refridge systems do?

[DmaxMaverick]

It is interesting...
Couldn't auto cooling systems take advantage of compression generating heat and the cooling effect from expansion like refridge systems do?

It could. However, efficiency will still be a major factor. The additional power requirements (compared to circulation only) will also be prohibitive, and counterproductive.

[Kmehr]

I am still curious about this. Would a compression pump like the A/c compressor really take that much more power than a standard water pump? I am guessing it would have to be much larger than the one used for the a/c.

[DmaxMaverick]

No matter how we try it, the additional power demand would be tremendous, compared to a traditional water pump and radiator system. Efficiency can't be gained. Mass and power demands will keep it out of contention, before we start doing some math.... The BTU's (units of heat) we are considering for "normal" driving characteristics are in excess of 200K (1 HP = 2544 BTU/hr), with very conservative power output. Add in some hard work, and it will more than double. Just for perspective: An average home window-type A/C is less than 8K BTU's, average large RV A/C unit is about 15K BTU's, and an average household central unit is less 48K BTU's (4 ton capacity).

Theoretically, a refrigeration system required to cool an internal combustion engine would about equal its power output, at 100% efficiency (currently impossible), and this isn't considering parasitic loss of the inefficiency. However, at 50% efficiency (requiring only 50% of its power output), it would be comparable to our traditionally accepted standard for engine cooling (we aren't trying to keep the engine at ambient temp). The power requirement for traditional engine cooling uses less than 10% of gross power output. I'm just pulling rough figures off the top of my head, but they won't be far from actual.

[Kmehr]

Got, it, refrigerate type cooling for truck = big ass refrigerator. Thanks,
Dmax, you must be an engineer of sorts...

[DmaxMaverick]

Engineer? Nah. I'm just the janitor. But I did stay in a Holiday Express last night.