Choosing a Coolant for Liquid Cooling Power Supplies

Liquid cooling uses a liquid, often water, to absorb heat and move it away from components. Compared to air-cooled systems, liquid-cooled power systems are much more efficient since liquids have a higher heat capacity than air. Water in particular has a heat capacity four times higher than air and can provide the same cooling power in a smaller space or better cooling in the same space.

Liquid cooling provides superior thermal management, is silent, and improves efficiency and reliability. These power systems are easily scalable and additional ingress protection keeps out dust and debris.

The coolant you choose can enhance system efficiency to better prevent components from overheating. Selecting the right coolant is especially important in high-power situations such as semiconductor fabrication equipment or industrial machinery. Learn how to choose the right liquid cooling system coolant for your application.

Understanding Coolant Types and Their Properties

The two most common cooling liquids are water and water-ethylene glycol.

Water is ideal for general use. It has a high thermal conductivity, is easily available and provides a good baseline to compare other coolants. The density of water is 0.99, its boiling point is 100 degrees Celcius (212 degrees Fahrenheit), and its freezing point is 0 degrees Celcius (32 degrees Fahrenheit). Using water in your liquid-cooled power system is cost-effective, especially if you use tap water. Purified and deionized water are more expensive.

Water-ethylene glycol (WEG) is a coolant mix similar to automotive coolant or antifreeze. While WEG has improved thermal properties, it's also more viscous, more expensive and more difficult to dispose of. Because WEG has a higher boiling point than water and a lower freezing point, it's better at maintaining stable system temperatures and has a lower risk of evaporation. However, the glycol can break down over time, requiring regular coolant checks and changes.

Properties of a Good Coolant

Key properties of good coolants are:

  • Thermal conductivity: Proper thermal conductivity is essential for efficient heat transfer. Water and WEG have about the same thermal conductivity, though WEG has a lower heat transfer efficiency.
  • Corrosion resistance: Ensuring corrosion resistance prolongs your system's life and maintains performance. WEG often contains additives to inhibit corrosion, which can reduce wear and extend the life span of the system. Minerals in water, especially tap water, can cause corrosion and scaling.
  • Environmental health and safety: Ensures safe usage and disposal. Water is the easiest to dispose of. In some regions, you can just pour it down the drain as long as it doesn't have additives and hasn't been contaminated. Check your local regulations, as well — you may need to neutralize it before pouring it down the drain or contact a hazardous waste disposal service. Ethylene glycol is toxic and special disposal methods incur additional costs. Some coolant can be recycled. 


Choosing the Right Coolant

When choosing coolant for liquid-cooled power systems, you'll want to consider several factors related to system compatibility and coolant performance:

  • Material compatibility: Ensure your coolant won't provoke chemical reactions or degradation. Not all components are compatible with every coolant. For example, deionized water isn't compatible with copper, some brass alloys or certain types of PVC.
  • Heat transfer requirements: Of course, you'll want to match coolant properties to your system demands. Pure water has a higher heat transfer efficiency, but WEG provides better protection in extreme temperatures. More ethylene glycol increases the protection against freezing at the cost of reducing the efficiency of heat transfer.
  • System design constraints: Be sure to consider any space and hardware limitations for your system. You may not have a place to safely store ethylene glycol, or your existing hardware might not be compatible with deionized water.
  • Heat absorption and dissipation: How a coolant absorbs and dissipates heat is key to maintaining optimal system temperatures. You'll also want to consider the ambient air dew point and humidity to avoid condensation. Ensure your coolant stays warmer than the dew point.
  • Flow rate considerations: The right viscosity ensures efficient circulation within the system. A fluid that is too thick flows too slowly and is ineffective at moving heat away. If it gets too thick, it can increase the system pressure or create clogs, damaging the system. Depending on the ratio of water to ethylene glycol, WEG is about twice as viscous as water alone.
  • Longevity and maintenance needs: Reducing downtime and operational costs. Water is prone to bacterial and algae growth, especially if you use tap water, so it requires regular checks, water processing, and maintenance. WEG has a longer life span but requires special disposal methods and careful handling.
  • Budgeting for coolants: When creating a budget for a liquid-cooled system, look at the initial investment and running costs. Water is generally cheap and readily available, but deionized water requires additional components to keep the water deionized, increasing the cost. If you choose water, budget for ongoing maintenance to test for bacterial growth. WEG is more expensive than water but still widely available. It requires less frequent maintenance and careful handling and disposal, raising maintenance expenses.

Enhancing Your Liquid Cooling Solutions With Astrodyne TDI

Astrodyne TDI supports various commercial liquid cooling needs.

Our LiquaBlade power supply is compatible with water, deionized water and WEG. It can be used independently in a standalone application or in parallel for high-power situations, such as military or industrial applications. All our liquid-cooled power supplies have robust power protection including fuses, circuit breakers, EMO and safety interlocks. Additionally, sealed power supply options protect the coolant system from contamination.

We can provide complete rack assemblies with plumbing, bussing and power distribution or only the components you need. We can also create a custom solution for your unique cooling requirements, tailoring a system to your specific application.

Selecting the Optimal Coolant for Enhanced Performance

Picking the right coolant affects your system's efficiency, efficacy and longevity. You can feel confident in your choice by learning about different coolants and making decisions based on compatibility and a performance evaluation.

Reach out to Astrodyne TDI for expert advice and customized liquid cooling solutions. We provide custom power systems for the medical industry, military and industrial use, and semiconductor capital equipment. Our components meet common standards for various industries and have additional filtering options to comply with EMI/EMC regulations.

Explore our options for liquid-cooled power supplies, or request a quote today!