Ed,

I went with parallel cores to maximize the flow through the engine, and to keep the pressure drop as low as possible.

 

Interestingly, I have a thermocouple on the inlet to the cores, and one on the exit to the cores. They show a ~5*F temperature drop across the cores. I also measure the temperature at the engine, on the block where the coolant has gone 1/2 way through the engine on the hot side. It registers somewhat higher, but that should be expected.

 

 

Bill Schertz
KIS Cruiser #4045
N343BS
Phase I testing

 

Hi Bill,

 

Had seen your nice data before, but one thing finally awoke in my old brain when I looked at it this time that I had not considered before.  We know that parallel cores give slightly better efficiency than a serial core set because the DT decreases for the second core in the series compared to both parallel cores having the same DT (at least in theory).  However, what jumped out at me this time was the real significance of the parallel cores in cooling.  In this case, I am assuming no thermostat in the coolant flow.

 

If I understood your graphs correctly, it looks like you are getting around 20 gpm flow with a single core (so presumably you would get a bit less with two cores in series – but perhaps not significantly), but looks like with parallel cores you are getting around 32 gpm flow.  That is a 20/32 =  approx 37 %  more mass coolant flow through the engine.   That means (all else being equal), you should transfer 37% more heat out of the engine per unit time with the parallel cores compared to the serial cores (assuming cores of same type and size). 

 

Now the engine is producing X amount of waste heat at Y HP that it needs to get rid of.  That won’t change for a given power setting Y.  So Q (waste heat X) produced by the  engine should be a constant at Y Hp.

 

So taking Q = M*Dt/Cp and since Q (waste heat)  = constant at power setting Y, then with M (mass flow up 37%)  implies that in this case Dt = (Temp of coolant out of engine – temp of coolant into engine)  should decrease by 37%.  When you increase the mass flow and are removing the same quantity of heat, the DT is of necessity a lower value.

 

If that is the case, then the question is  - does this mean the temp of coolant into the engine increases – not necessarily desirable, or does the Temp of coolant out of the engine decrease? Or a bit of both?  I suspect it’s a bit of both depending on the radiator’s performance.  If your radiators/air flow are the limiting factors, then transferring more heat per unit time to the radiators is not going to buy you much.  The reason is that if it is not able to get rid of the heat at the faster rate and the DT between the coolant and air will be less.

 

But, my guess is that this theoretical increase in heat removal by using parallel cores could be useful in some situations – again if you are already limited in the airflow situation, then this won’t make much difference.  It  does suggest that using parallel cores could result in the need for core sizes 37% smaller.  OR did I miss something here?

 

 

 Like your data in any case

 

Ed

 

 

Al,

Are you sure of the 40 GPM?  That seems like a lot.  My radiator in/out is 1.25 inches, so the water would be traveling at 628 feet per minute at that flow rate.  That is over 7 miles per hour!