Tap water meets the needs of most liquid-cooling applications. However, deionized water has chemical and electrical properties that make it the optimal choice for cooling when the liquid circuit contains micro-channels or when sensitive electronics are involved.
As the name implies, DI water has an extremely low concentration of ions which imparts important performance attributes. Firstly it eliminates mineral deposits which block the coolant flow. This will degrade cooling efficiency and system operating performance. Secondly it eliminates the risk of electrical arcing due to static charge build up from the circulating coolant. The arcing can damage sensitive control electronics in the equipment being cooled. The lack of ions in DI water eliminates both of these problems.
Applications that require the use of DI water are found in industries such as:
Care must be exercised when using DI water. The very lack of ions also makes this coolant unusually corrosive. Called the "universal solvent," DI water is one of the most aggressive solvents known. In fact, to a varying degree, it will dissolve everything to which it is exposed. Therefore, all materials in the cooling loop must be corrosion-resistant.
Copper and many other common materials are not compatible with DI water and will contaminate it. When you design a system using DI water, be sure to specify DI-compatible materials such as stainless steel or nickel.
In a heat exchanger or cold plate, we recommend a stainless steel fluid path such as those in our Aspen series heat exchangers or our CP10 cold plates. A DI friendly recirculating chiller should contain a nickel-brazed evaporator, a stainless steel pump head, and nickel-plated fittings. Finally, to maintain the DI water purity, a deionization cartridge must be included. As with all consumables the DI cartridge must be replaced periodically.
In summary, DI water-cooled systems are critical to the reliable operation of many types of equipment. When properly designed and maintained, these systems can provide reliable cooling and leak-free operation for many years.