When operating a water/glycol cold plate or heat exchanger, it is important to have a maintenance plan. The typical maintenance activity is flushing and refilling the system with the proper mixture of inhibited ethylene glycol and water. This should be done on a periodic basis at an interval determined through system level testing during the operational evaluation phase. Periodically, the fluid pH and refractive index should be measured. These measurements will change over time. From these measurements, a flushing frequency could be determined.
During deployment, it is common for coolant systems to be "topped off". This practice should not harm the cold plate or heat exchanger as long as the glycol concentration is not diluted to the point of making the inhibitor ineffective. Inhibitor effectiveness is a function of top-off water quality, other metal types in the fluid loop, and the age of inhibitor in the system. If "topping off" is employed, it is advisable to monitor the pH of the fluid. If the pH falls below 4.0 or rises above 9.0, a system flush/fill should take place as soon as possible.
Corrosion resistance begins with cold plate or heat exchanger design. It is also important to develop maintenance procedures that will maximize the life of the aluminum cold plate or heat exchanger.
1 Editor J.R. Davis, ASM Metals Handbook, Desk Edition, Volume 2, Materials Park, OH, 1998, page 501.
2 Ibid, page 499.