Thermostat education please

[Aviator5]

Re: Thermostat education please

If you quench steel in the water and keep it still it will take much more time to cool it down as opposed to have it running in the water, or have water running by it, and the faster you run it the faster it will cool down. That will represent your closed, and open loop. If you run an open loop cooling system without thermostat, it will never reach the working temperature, it will always stay cool, but will never overheat, as it was suggested above. Assuming that it won't be clogged anywhere else.

 

[QC]

Re: Thermostat education please

You guys are TOTALLY missing the removed thermostat issue. If it is removed the raw (cold) water can bypass the circulating pump and not go through the engine. The thermostat directs water flow as well as controls temp. The engine can overheat because cold water is not completely routed through the engine. That's why racers and engineers that are testing use blocked open or orifice style thingees to replace the thermostat. If some of the cooling water is simply going back overboard then it cannot cool the engine . . .

 

[Knightgang]

Re: Thermostat education please

If you quench steel in the water and keep it still it will take much more time to cool it down as opposed to have it running in the water, or have water running by it, and the faster you run it the faster it will cool down. That will represent your closed, and open loop. If you run an open loop cooling system without thermostat, it will never reach the working temperature, it will always stay cool, but will never overheat, as it was suggested above. Assuming that it won't be clogged anywhere else.

Have you ever melted the bottom of an aluminum pot over a gas flame while it was full of water? I have. It is possible to heat metal faster than the water can absorb the heat. Having said that, if the water is moving through to fast, the heat exchange does not take place and the metal will continue to heat. I would say that in most engines running at normal cruise speeds this may not be an issue with no thermostat. However, running one very hard and at WOT speeds up the water flow and thus reduces the heat transfer. Could present an internal overheat situation, however it would not be caught if you are not moniting head temp, and are monitoring only collant temp...

 

[Aviator5]

Re: Thermostat education please

You guys are TOTALLY missing the removed thermostat issue. If it is removed the raw (cold) water can bypass the circulating pump and not go through the engine. The thermostat directs water flow as well as controls temp. The engine can overheat because cold water is not completely routed through the engine. That's why racers and engineers that are testing use blocked open or orifice style thingees to replace the thermostat. If some of the cooling water is simply going back overboard then it cannot cool the engine . . .

That is totally wrong, the fully open, or missing thermostat opens the flow thru the engine block and the pump. Closed thermostat redirects the water flow within the block, but it never bypasses circulating pump.

 

[Aviator5]

Re: Thermostat education please

Have you ever melted the bottom of an aluminum pot over a gas flame while it was full of water? I have. It is possible to heat metal faster than the water can absorb the heat. Having said that, if the water is moving through to fast, the heat exchange does not take place and the metal will continue to heat. I would say that in most engines running at normal cruise speeds this may not be an issue with no thermostat. However, running one very hard and at WOT speeds up the water flow and thus reduces the heat transfer. Could present an internal overheat situation, however it would not be caught if you are not moniting head temp, and are monitoring only collant temp...

Have you ever tried to melt the aluminum pot with water running thru it, espacially in the open loop, not recirculating?
And again, speeding up the water will not reduce, but increase the heat transfer.
Slowing down the water will only warm it up faster, thus reducing the heat transfer rate.

 

[Knightgang]

Re: Thermostat education please

That is totally wrong, the fully open, or missing thermostat opens the flow thru the engine block and the pump. Closed thermostat redirects the water flow within the block, but it never bypasses circulating pump.

I gotta agree with this statement. Water pump circulated water, on either system, whether the thermostat is open or closed...

 

[QC]

Re: Thermostat education please

That is totally wrong, the fully open, or missing thermostat opens the flow thru the engine block and the pump. Closed thermostat redirects the water flow within the block, but it never bypasses circulating pump.

I am sure I am not articulating it properly, but when there is no thermostat it goes both ways . . . Closed thermostat in a "closed" system bypasses the radiator/heat exchanger . . . Closed thermostat in an "open" system "cold" water goes overboard, hot water circulates in the engine. Open thermostat, coolant goes through block in both cases. Removed thermostat goes both overboard and through block, but is not purposely directed, path of least resistance . . .

 

[Aviator5]

Re: Thermostat education please

Bottom line is - termostat is a necessary part of the engine. Running engine either too cool or too hot will have a negative effect on engine performance, engine life, fuel consumption and so on. End of story.
As far as heat exchange between cylinder and water, or coolant, - refer to Newtons Law of Cooling

 

[Maclin]

Re: Thermostat education please

Bottom line is - termostat is a necessary part of the engine. Running engine either too cool or too hot will have a negative effect on engine performance, engine life, fuel consumption and so on. End of story.
As far as heat exchange between cylinder and water, or coolant, - refer to Newtons Law of Cooling

Bottom line -.5 learn Marine raw water cooling systems.

 

[Dshow]

Re: Thermostat education please

I have to agree with Aviator on this one. If the water goes to fast, it may cause cavitation in the cooling system leading to poor heat exchange, but that is the only thing I've heard of.

 

[Aviator5]

Re: Thermostat education please

Thanks for advise Maclin,
perhaps you should learn fundamentals of thermodynamics too.

Dshow, you are correct, but to reach the cavitation stage in the cooling system it will take more than just recirculating pump. In fact it will start cavitating first.

 

[Don S]

Re: Thermostat education please

Thanks for advise Maclin,
perhaps you should learn fundamentals of thermodynamics too.

Dshow, you are correct, but to reach the cavitation stage in the cooling system it will take more than just recirculating pump. In fact it will start cavitating first.

You do realize, that a raw water cooled system on a MARINE engine also have a raw water pump FORCING coolant through the system faster than the circulating pump can. Maybe my words of slowing down the water so there was more heat transfer, could be the result of cavitation because of excess water movement and possible air in the system from the water pickup.
Whatever, it does happen on boats.

 

[Aviator5]

Re: Thermostat education please

That is correct, Don. The cavitation may cuse the overheat, but not water running too fast. Marine, or automotive, or aeroplane or any other engines and their cooling systems work according to fundamental laws of physic, thermodynamics, heat transfer. Unless everything MARINE gets blessed by Neptune, and follows its own law.
Just out of curiosity I'll try to calculate at what speed raw water pump should run to start cavitating. But I'm pretty sure engine won't rev up that high.

 

[Don S]

Re: Thermostat education please

Not necessary for a bunch of calculations. Basically, for the most effecient heat transfer use a thermostat. As manufacturers of engines have known for YEARS, without a thermostat (where there should be one) the possibility of an overheat is possible. I have seen it on boats, and on cars. So a lot of fancy equations isn't going to change my opinion.
I'll be glad when summer gets here and everybody wants to go boating and doesn't have to nit-pick over every little word that is said on these forums.

 

[Aviator5]

Re: Thermostat education please

Thermostat is used to keep constant temperature, not the most efficient heat transfer.
I wonder what would it be like, if all apparatus that we use were built based upon somebodys opinion, but not calcullations.
Why spend millions on sciense when somebody seen overheated engine with thermostat missing, and assumes that it is a cause of overheat. Perhaps if you have looked further you would've found the real cause of overheat.

 

[trendsetter240]

Re: Thermostat education please

Hey guys, remember the OP? The one who wanted to learn a little bit about thermostats?

Yeah, a thermostat is used to regulate temperature. The thermostat has a set temperature at which it begins to open and continues to open as engine temp increases.

The thermostat will open or close, regulating water flow through your engine to maintain the engine at the optimal operating temperature. As metioned, engines are less efficient when cold, that is why the thermostat is closed when the engine is cool. When the engine reaches the pre-determined optimal operating temp, as set in the thermostat, it opens to maintain the temp.

Is one required for your motor to run to it's maximum efficiency? YES

Should you ever remove it? NO

Should you replace yours if it's stuck. YES.

Now I don't have an engineering degree nor did I recently take any outboard mechanic courses; but I did stay in a Holiday Inn Express last night

 

[Don S]

Re: Thermostat education please

Now I don't have an engineering degree nor did I recently take any outboard mechanic courses; but I did stay in a Holiday Inn Express last night

And with that note, we will put this never ending thread to bed.