PROLOGUE:


I completed my testing of the intercoolers several weeks ago and did not publish the results, because I could not interpret the data in a meaningful way. Data is data and if it disagrees with your belief, this does not change the readings. Finally figured out the cause of the skewed results and now see that the results weren’t really bad. The test set up had a fundamental issue, which I had anticipated – and got bit by.

On to the real testing. To do bench testing of the intercoolers thermal capacity I ran hot water from a water heater thru the waterside of the IC. The gas water heater was 50-gallon capacity and with the thermostat, the water was held at a relatively constant temperature. The water went from the top of the water heater thru the IC then to the 90 series pump and back to the bottom of the heater to conserve water and maintain the water temperature. I reduced the water pressure in the heater so that it was about 5-6 psig pressure as the 60 psig house pressure would have damaged things and been blowing hoses off fittings, not to mention damage the IC.

I put the pump on the outlet side of the IC so that it would be sucking the cooler water and not cause cavitation or boiling at the input to the pump blades due to the low pressure. 120-degree water will boil very easily when its pressure is reduced, it does not boil in a pot because the atmospheric pressure holds the water surface together. 32-degree water will turn to ice in space because the vacuum causes it to boil so rapidly…… See chart at the end, 2 psi causes 120 water to break surface tension and boil..cavitate.

http://docs.engineeringtoolbox.com/d...emperature.pdf

PHOTOS at bottom, H/E chart also provided

Test setup video:


The included photos show the charts I prepared, and because this is the third or fourth time I did them I got carried away and neglected to write the FLOW GPM values on the photo that says” 5.5 Static psig”. The correct values should be are 2.0, 3.0,and 3.9 GPM ( almost 4.0) top to the bottom. The reason multiple tests were run, was that the setup had cavitation issues at first and visible bubbles were present at the flow gauge. I increased the pressure from 0.0 to about 5-6 psig to try and eliminate the boiling or cavitation in the pump. Think of the picture of an outboard motor prop in water. That is cold water and about 2 feet under the surface, about one more psig above the atmospheric value ( 14.7 psig absolute ).

The readings worked out to give the number of BTU’s expelled for each water flow rating. The BTU value, is the temperature change in degrees x (times) the number of gallons per minute x times the weight of water per pound (8). A 1-degree drop in water temperature with 2 gallons per minute would be 1 x 2 x 8 = 16 btus per minute. The first test of the 90 series pump on the stock IC was 6.6 degree drop with 2 gallons per minute x 8 pounds /gallon = 105.6 btu’s per minute. In an hour the result is multiplied by 60 to give about 6336 BTU’S per hour. Like I said the air conditioner is between ½ to 1 ton of cooling which is 6000 to 12000 BTU’s per hour. My test is representative of the operation of the IC in the car but the airflow is lower, and I anticipate the IC is doing even more cooling than this 6xxx BTU test value.




Results:

The stock ( series ) IC produced water temperature drops of 7.1, 5.0 and 3.9 degrees for a flow rate of 2, 3, and 3.9 ( 4.0) gallons per minute. I calculated the Btu rates, and got surprising results in that the 2 GPM provided 6336 BTU/ hour and 3.9GPH a greater water flow gave me 4956 BTU/ hour heat rejection rate. This all seemed wrong to me and was an issue to understand. How did better water flow reject LESS heat to the air stream - - - back in a moment.

My pet parallel flow IC seemed to operate correctly in that the heat rejected followed the water flow and did better with higher flows. When I crunched the numbers it worked out that the 2 GPM flow rejected 7104 BTU/ hour, 3GPM rejected 7200 BTU/ hour and at 4 GPM we were able to reject 7488 BTU/ hour a definite gain over the stock design. I will say that the parallel IC is a definite better design and will reject more heat and flow more water.

The video will show the test bed and some detail about the operation of my test stand. I’m glad to have gotten the results and that I am basically done with all this fiddling. Phew that was 20 hours to end up getting confused.


EPILOGUE:

The stock IC rejected less heat than the parallel IC design, but the heat it got rid of seemed to Fall as the water flow went up????? I now have gotten my arms around this counter intuitive result.

The water was hot, the pump was sucking the water thru the IC and then the flow went thru the flow gauge. I am convinced that the water flow was turbulent and also restricted by the three-pass design. This lead to voids or cavitation within the IC with increasing pump speed and flow. This means that the readings were lower due to the disruptive water flow…………….. Remember the static water pressure was about 6 PSIG!!!

In the car the water is pressurized by the radiator running about 15-19 PSIG of pressure and cavitation of the IC would not be an issue. With the separated IC water tanks, there is basically no pressure ( plus less heat in the water ) and cavitation may occur REDUCING the heat rejected. If cavitation occurs in the pump and or the IC body we loose benefit by some margin. The air heating the IC may be well over 250 degrees, on a stock SRT.

For the first time I’m seeing this and will devote thought to the idea of running a pressurized super cooler, to insure this can’t happen. I would have no way of knowing if the pump in my car is cavitating, remember the outboard motor video image.

WOW I learned more than I had expected, just by doing this “”simple”” measurment. Now I will have to see if there is a way to incorperate the better pump ( 90 ) in my car and monitor the water conditions in the IC.

PLEASE REMEMBER this has nothing to do with my using the 90 series pump in the test set up. A variable voltage motor speed controller controlled the speed and thus it was running slower than a stock pump. This is due to the larger impeller flowing the same water as a stocker or 30 series pump –around my self-imposed limit of 4 GPM in the testing program. Had the 90 series pump been running at high speed the results would not be similar to the real car conditions, and thus the readings would be out to lunch.

So parallel path IC is good, testing with higher static water pressure would provide better results on both of the IC tests. IF I do more testing I will be testing with 7 to 10 PSIG static pressure to avoid errors due to localized boiling. Gotta check my system in the car as soon as it gets warm and relay the findings back to all u all.

Wdy, enjoy