The life of high-powered electronic equipment is directly affected by its operating temperature. Keep the equipment cool, and it should last a long time. But anyone who has ever experienced equipment failures due to dirty air filters, high ambient temperatures or “burned out” exhaust fans knows how challenging this goal can be. Wouldn’t it be nice if you could seal your equipment enclosure and keep it clean from the day-to-day dirt, dust and grime in your plant?
With water cooling systems, you can. Water is a more efficient heat-transfer agent than air and has been used successfully for many years to minimize electrical power losses in the form of heat generated by the equipment. Although water cooling presents some challenges, the advantages often outweigh the drawbacks, especially for plants that have experienced repeated problems using air-cooled systems.
The following questions can help you decide whether water cooling makes sense for your application.
- Is the installation site contaminated with
dirt, dust (especially conductive dust) or grime?
- Do you experience frequent electronic equipment failures due to
- Is cooling water available?
- Does your plant have a high ambient temperature?
- Would a smaller overall enclosure size help minimize space constraints in your plant?
The Advantages of WaterThe most obvious advantage to using water cooling is its ability to keep the equipment cool. Lower temperatures in electronic equipment usually translate to higher reliability.
Sealed enclosures are common in water-cooled equipment because the heat generated from the power losses is removed with the cooling water through air-to-water heat exchangers and chill blocks. In the case of transformers, the actual winding can be a hollow tube with water flowing through it. Such sealed designs can substantially minimize the maintenance requirements and equipment failures often experienced with air-cooled systems, which are susceptible to dirt infiltration.
If the overall size of the unit is important - and it almost always is - water-cooled enclosures can be made smaller because the individual components of the water-cooling system usually are smaller. In some cases, the overall equipment size can be reduced by 30 percent or more compared to air-cooled systems.
Overcoming Common ChallengesThe initial cost of the equipment and plumbing as well as the cost of cooling water are the biggest drawbacks to implementing water cooling systems. However, these costs should be weighed against the value of keeping the electronic equipment operating efficiently with minimal maintenance requirements. Additionally, the water consumption and flow requirements in a closed-loop water cooling system are minimal. Generally speaking, 0.25 gal/min of water will dissipate 1 kW of heat and only experience a 27˚F (15˚C) temperature rise. Each piece of equipment is different, so the water requirements should be reviewed for each application.
Another common challenge faced with water cooling is inadequate water quality. Hardness, suspended solids, acidity, alkalinity and biological contaminants can affect the efficiency of the water-cooling system. Ensuring adequate water quality is not as difficult as it might seem, however. Simply put, if the water is of drinking quality, then it is safe to use for cooling electronic equipment.
In some cases, corrosion or oxidation can be caused by dissolved oxygen in the water. This oxidation is a thermal barrier that can reduce the effective cooling of the water system. Chemical inhibitors can be added to the water to reduce the dissolved oxygen, but these chemicals also will reduce the resistivity of the water. Always monitor the water resistivity/conductivity after adding any chemicals to make sure it does not fall below accepted levels.
One other reason many plants have been reluctant to use water cooling systems is the potential environmental impact related to water consumption. However, modern water cooling systems are designed to be safe and efficient.
By using a properly sized, installed and maintained water system, you can prolong the life of your electrical equipment and minimize maintenance requirements without adversely affecting the environment.
Water System Characteristics
- The maximum inlet water temperature
should be 102˚F (40˚C).
- The minimum inlet water temperature should be above the dewpoint to
- The system should have a maximum pressure of 80 psig, limited to the
inlet of the equipment.
- The water flow should follow the equipment specification.