Controlling and affecting proper operating temp

[Ball Racing]

Daniel, are you using a valve in the bypass or is it blocked off? You may want to try the smaller shoe.

Dave Neptune

I have the moyer check valve and ball valve conversion, along with the adaptor plate, and a 160 thermostat.
I have the gate valve turned so it a straight shot, as to help make heat.
If I close the valve, the block never warms even at WOT...
But my block only has about 150 ish miles on it since I rebuilt it, and all the passages are clean.

That being said back in november when the creek was warmer I was getting 150 at WOT, but if I slow down, the temp is back to nothing.

The big shoe came with the pump, and I Love how it makes my exhaust sound

[ILikeRust]

I have the gate valve turned so it a straight shot, as to help make heat.

I think you meant ball valve.

I'll have to try this next time I'm motoring anywhere. I think I turned it so it was maybe 1/2 closed, out of caution so that the engine wouldn't get too hot. Maybe I'll open it up and see what happens.

[hanleyclifford]

Coolant Running Free

Now that I have joined the "no thermostat" group I observe that the engine runs about 10 degrees cooler at WOT. It seems that the thermostat itself had become the most restrictive component (MRC) or bottleneck in the system. I start the engine with the bypass wide open and the engine will get up to around 145 degrees at 1000 rpm. Only when I go to cruise rpm is it necessary to start closing the valve. I run 2000 rpm at 165 with valve fully closed.

[Ball Racing]

I think you meant ball valve.

I'll have to try this next time I'm motoring anywhere. I think I turned it so it was maybe 1/2 closed, out of caution so that the engine wouldn't get too hot. Maybe I'll open it up and see what happens.

Yeah, I "meant" ball valve
I was trying to think of the wording opposite of the check valve, and ball was on the brain, but gate on the fingertips, and fingers won...
Either way the valve that controls the flow is set to a non restriction at this point.

Just one more thing...
to pull off the last 100-200 max rpms I can see,,,,, the engine has to be warmed up alot.
When she is cold 2,400 rpms wot, after hot(well warmer rather) 2,600 rpms if barometer, and humidity are willing..

[Marian Claire]

I think several posts here highlight one of the benefits of the recirculating loop. With the loop you have some control over the temp of the coolant entering the engine and from that you can gain more control over the operating temp. FWC or RWC the affect of the temperature of the water the boat is sitting in can be minimized.
I also think that the higher the temp of the incoming coolant is, as long as it still can cool the engine, the better. There would be less difference between entrance and exit temps and that would add to more even temps thru out the system. Dan S/V Marian Claire

[edwardc]

How does solely running coolant faster lower its temperature? Does running hot coolant faster make it cooler? Using another thought experiment of an extreme example, could we run the coolant fast enough to eliminate the need for a heat exchanger??

Probably a bad choice of words. Running coolant (either raw water or antifreeze) through the block faster results in it being in the block a shorter amount of time, hence, as you have pointed out, it doesn't have as much time to absorb heat, and doesn't reach as high a temperature. Hence, faster corresponds to cooler.

...Without consideration of the variables of exchange efficiency, heat exchanger capacity, raw water temperature and raw water flow rate, inside the heat exchanger the longer the coolant remains there the more heat is extracted...

I know it intuitively seems that way, but it's just not so. True, the longer a particular cubic inch of coolant remains in the heat exchanger, the more heat is extracted from that cubic inch and the lower it's temperature gets; however, this also means that fewer cubic inches per second are going through the heat exchanger, reducing the total heat transfer. In addition, those cubic inches are now cooling to a lower temperature while inside the heat exchanger , decreasing the delta-T between the hot coolant and the colder seawater. This greatly decreases the heat energy transferred, because the total heat energy transferred is a function of the square of the temperature difference, much as electrical power (watts) is a function of the square of the voltage.

I know we'd like to ignore "...the variables of exchange efficiency, heat exchanger capacity, raw water temperature and raw water flow rate...", but in a dual heat transfer problem (block cooling jacket and heat exchanger), you have to deal with them. A static solution is not going to yield correct answers, as this is a dynamic problem that will eventually settle into a steady state. The two exchangers (block & HX) interact with each other and with each other's temperatures, every time something perturbs the system.

So lets try another thought experiment. Assume we have a FWC system where the coolant is running at some flow rate, and the raw water section is running at another rate, and everything is sized such that the system is in equlibrium and the HX is extracting all the waste heat the engine is generating. The temperature on the "hot" section of the coolant loop from the engine to the HX is higher than the temperature on the "cold" section from the HX back to the engine.

Keeping the engine (heat production) and raw water rate (heat removal) the same, lets increase the flow rate in the coolant loop. Each unit of coolant now spends less time inside the engine, and so does not absorb as much heat and its temperature increase is less. At the same time, this lower temperature allows a higher heat transfer rate, and the engine temperature falls reducing the heat transfer rate back to what it was.

Similarly, in the HX, each unit of coolant spends less time there, and does not loose as much heat there, and thus it's temperature does not fall as much. This higher temperature drives a greater heat transfer into the seawater side, until it also adjusts into equlibrium.

So it seems that the faster flow in the coolant loop causes the temperature difference between the "hot" and "cold" side of the coolant loop to be less.

We can convince ourselves that this is so by carrying the experiment to extremes. If we increase the coolant flow rate to infinity, each unit of coolant spends an infinitely small amount of time in the block, and so it's temperature does not rise. Similarly, each unit of coolant spends an infinitely small amount of time in the HX, and its temperature does not fall. So, for an infinite coolant flow rate, the temperature is uniform around the whole coolant loop. But the cooling system still works, as the engine sees it's coolant jacket filled with coolant at a uniform temperature that is lower than the engine's , and the HX sees its coolant side filled with coolant at a uniform temperature that is higher than the seawater's. The engine is still running at the same load, and producing the same amount of waste heat energy, it's now just running at a little lower temperature.

So the conclusion of all this is that running the FWC coolant loop faster results in less temperature extremes in the coolant, and lowers the engine temp.

And we see evidence supporting this in the real world. FWC systems remove the same amount of heat energy as RWC systems, they just tend to do it at a higher temperature. I suspect that the "equlibrium temprerature" of the engine in our infinite flow rate thought experiment is theoretically equal to that of RWC system at the same engine load and seawater flow rate. Since real-world FWC systems operate with a coolant flow rate somewhere below infinity , they should run a little bit above that of a RWC system.

MAN! I feel like I just completed a final exam word problem in a Thermodynamics class!

[hanleyclifford]

Stunning!

Ed - Thank you for that clear and logical discourse which will be of enormous value to this forum. And you did it without resorting to differential equations and integral calculus. This should be maintained as a link of very particular interest.

[ILikeRust]

Oh crap! I'm having flashbacks to Chem 31. I still remember the name of that class: "Chemical Equilibria in Aqueous Systems." I remember only a teeny, tiny fraction of what we covered, let alone what I "learned" - I do recall we spent a fair amount of time on thermodynamics.

Now I think I need a beer...

[edwardc]

Oh crap! I'm having flashbacks to Chem 31. I still remember the name of that class: "Chemical Equilibria in Aqueous Systems." I remember only a teeny, tiny fraction of what we covered, let alone what I "learned" - I do recall we spent a fair amount of time on thermodynamics.

Now I think I need a beer...

I think I need two!

Yeah, this does invoke flashbacks. And everywhere you look, chemistry, physics, thermodynamics, electronics, mechanics, biology, the same few equations keep popping up over and over again!

[positron]

Faster flow = more cooling for another very cool reason, on top of what Ed mentioned. Liquid flowing through a tube exhibits "laminar flow", where the wall of the tube cause a drag. The liquid in the center flows faster, and there is a small dead zone along the tube walls with little flow. The dead zone acts as a sort of insulator between the tube wall and the flowing water. Increasing the flow velocity decreases the size of the dead zone, which increases thermal transfer efficiency more than than the simple factor of more flow (up to point). This is especially important for tubing walls which may have minor imperfections. Or in the case of most A4s, somewhat larger imperfections.

[ndutton]

Just so I completely understand - -

In an extreme example, starting with hot coolant are you saying passing it through a heat exchanger rapidly like maybe 5 seconds will result in greater heat loss than letting is sit in there for say, fifteen minutes? Both conditions would have the same raw water flow at the same temperature and the same volume of hot coolant equal to the HX volume so the only variable is hot coolant flow.

[positron]

Not quite. As you increase the flow rate, you can decrease the amount of time needed to remove the same amount of heat. Your 15 min example is a little extreme. As mentioned in another response, heat transfer efficiency is higher when there is a larger difference between the coolant and the coolee (or sea water in this case). By pumping faster, the coolant is warmer throughout the heat exchanger so heat transfer is more efficient. This means that overall more heat will be removed from the coolant and hence the engine. On the other hand, letting coolant sit in the heat exchanger for 15 minutes is undoubtedly the best way to cell down that particular volume of coolant, but your motor won't be very happy... The ultimate goal is not to cool down the coolant, but to cool down the engine.

[Ajax]

The point here is that the temperature of the block, not the coolant, is the issue. Certainly by slowing the coolant in the exchanger we can extract more heat and deliver a cooler product to the block. But while this is occuring the block is heating up at different rates at various points in the block. The question then becomes; can we achieve a lower and more uniform average temperature throughout the block, notwithstanding we are injecting coolant at a hotter temp than is potentially available?

This is why I'm interested in the Indigo thermostat housing. It supposedly promotes uniform temperatures within the engine.

As it is, my engine never gets above the second tick mark no matter what the water temperature, or how hard I run it, even with new, hotter plugs. I will soon be installing the thermostat that Shawn lent me, so we'll see what happens then. My housing isn't badly corroded at all, so the dual-action should work as designed.

[edwardc]

Not quite. As you increase the flow rate, you can decrease the amount of time needed to remove the same amount of heat. Your 15 min example is a little extreme. As mentioned in another response, heat transfer efficiency is higher when there is a larger difference between the coolant and the coolee (or sea water in this case). By pumping faster, the coolant is warmer throughout the heat exchanger so heat transfer is more efficient. This means that overall more heat will be removed from the coolant and hence the engine. On the other hand, letting coolant sit in the heat exchanger for 15 minutes is undoubtedly the best way to cell down that particular volume of coolant, but your motor won't be very happy... The ultimate goal is not to cool down the coolant, but to cool down the engine.

Couldn't have said it better!

[Ball Racing]

As it is, my engine never gets above the second tick mark no matter what the water temperature, or how hard I run it, even with new, hotter plugs.

Hotter plugs means the plug tip runs hotter.Does not make the water hotter unless the motor was so rich and unable to fire on that cylinder, and make any HP or heat BTU's...