RESOURCES
Understanding the common knowledge of water impurities and their effects on metals is crucial. Astroyne TDI, with over 50 years of experience in water-cooled applications, can offer valuable guidance in implementing liquid cooling solutions from our extensive product line. However, we strongly recommend consulting with the appropriate experts within your facility to determine the best course of action.
In the realm of electronics, there's an interesting anomaly: while some components operate better at warmer temperatures, they are also limited by a catastrophic failure threshold, which is clearly outlined in all product datasheets—including ours. But why do these limits exist, and what do they mean for cooling strategies? It's essential to understand these real temperature limits. Typically, in electronics, passive components like inductors and capacitors are kept within a 100 to 105°C range, although cooler is always better. However, some semiconductor equipment can tolerate higher temperatures at their core junctions and may even perform better when warmer, though they also heat up more rapidly.
Insulation materials such as wiring insulations, PCB magnetics, coatings, and paints also have thermal limits. It is a balance of all these factors that determines the cooling requirements and the subsequent design of cooling systems.
Inside the box, components have one type of limit, but human contact introduces another—nobody wants to touch something that feels excessively hot. Around 65°C is the threshold where humans begin to perceive heat as uncomfortable, leading to a natural reaction to drop the object.
It's also well-documented that chemical reactions typically double in rate with every 10°C rise in temperature. This means that degradation processes will accelerate, sometimes twice as fast, with a 10°C increase. This is an inherent nature of plastics, metals, and coatings that we must diligently monitor and manage.
To maximize the useful life of electronic components, maintaining a cool temperature is essential. Investing in high-power systems, such as laser-cutting machines or power systems, is a long-term commitment. These systems are not only expensive to purchase but also require ongoing maintenance to achieve a lifespan of 20 to 30 years. While replacements are possible, the goal is to ensure a good return on investment over the long haul.
Reliability is intrinsically linked to temperature. Numerous theoretical and practical guidelines emphasize the importance of keeping components cool to extend their longevity. Infrastructure investment, whether in high-power systems or advanced tools like laser cutters, is substantial. The key to maximizing the return on such investments is to ensure a prolonged operational life. We know that effective cooling reduces the failure rate of electronic components. Managing heat efficiently allows for more power to be packed into a smaller frame, thereby enhancing the overall life of components and materials.
Heat management is crucial, not only to control temperature rise but also to prevent it from deteriorating over time. Higher temperatures accelerate corrosion and deposition, which degrade the cooling system, creating a vicious cycle that leads to quicker system failure. Therefore, superior cooling translates to a higher return on investment, a principle evident in both daily life and electronic systems.
When discussing electronic cooling, air cooling with fans is often seen as a straightforward and common method. However, why is liquid cooling sometimes preferred, and what advantages does it offer over air cooling?
While a common quick fix for heat dissipation is adding a fan, this approach comes with its own set of challenges. Fans generate noise and require regular filter changes to prevent dust accumulation, leading to ongoing maintenance. They also necessitate unobstructed airflow paths through the electronics, which isn't always practical. Furthermore, air cooling is inherently tied to the ambient temperature; if the surrounding air is warm, the cooling effectiveness diminishes significantly.
In contrast, liquid cooling addresses these issues. Water is a far more efficient heat carrier than air, being up to 100 times more effective in ideal conditions. In practical applications, water cooling can be 10 to 20 times more efficient than air cooling. Liquid systems are quieter, can be completely sealed to prevent dust and corrosion, and offer greater flexibility in component orientation and system design. Chilled water can be used to keep the electronics significantly cooler than the ambient air, further enhancing their lifespan. As illustrated in the accompanying diagram, liquid cooling enables much higher power density in compact form factors, offering clear advantages over traditional air cooling methods.
| MercuryFlex™ 23kW/4U (~6kW in 1U) | LiquaBlade™ 16.5 kW in 1U |
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Fans, DC power, Go! Thermal conductivity of 0.025W/(m*K)22,8 kW @ 4U Fan noise Limited life Air filter blockage Need clear straight-line path and plenum Inside is always warmer than the Ambient air |
Needs Coolant infrastructure Thermal conductivity of 0.598W/(m*K)Needs No noise Less maintenance Front and back can be obstructed Inside can be cooler than the Outside |
The possibility of conversion within the 1U space highlights a significant disparity, but it's clear that each system comes with its own set of advantages and disadvantages, which we'll explore further.
Now that we've covered some foundational concepts, let's shift our focus to the types of coolants, how to select them, and the decision-making process behind it. With the acknowledged superiority of liquid cooling, it's crucial to understand the fundamentals. How many cooling methods are there, and what cooling systems are available?
Sure, an open-loop system seems straightforward—you take clean river water, run it through pipes, and then discharge it. However, rivers aren't available everywhere, so you need to consider which cooling systems you can build and maintain. The type of coolant you use is today's key topic, and we'll delve deeper into this and the markets we serve.
Coolant and cooling system attributes often determine their suitability for specific markets, as we will see. When it comes to flow rate, it might seem intuitive: more power generates more heat, necessitating a higher coolant flow. However, flowing substantial fluid through compact systems means dealing with confined plumbing, which can only handle a certain amount of water before pressurizing.
Another critical aspect is compatibility. Not all coolants or metals are the same. Understanding the impact of the coolant on the metal and plumbing structure over the long term, including its effects on rubbers, insulators, and gaskets, is essential.
Ultimately, the quality of the coolant is paramount. Is it consistently clean? What level of purity does it maintain, and how much maintenance is required to keep it that way? These are some of the topics we'll briefly cover.
What Qualities Make a Good Coolant?
Fundamentally, a good coolant must flow well. If it lacks good flow, it isn't effective. It should also have excellent thermal conductivity, allowing it to pick up heat efficiently as it moves through the pipes and metal structures. The coolant must be friendly to the metal plumbing and compatible with materials like rubber and silicone used in gaskets, ensuring the system's long-term health.
Sustainability is another crucial factor. You don't want toxic materials flowing through your plumbing system due to potential leaks and disposal issues. The coolant also needs to be commercially viable—not so exotic that it becomes prohibitively expensive. Longevity is key; the coolant should offer a high return on investment over a long period, maintaining consistent performance year after year.
Generally, high-power applications benefit the most from liquid cooling systems. Industries like semiconductor manufacturing, heavy industries, and the military, which involve significant power usage, require efficient cooling solutions. Semiconductor plants, for instance, might use around 10 megawatts of electrical energy, with a significant portion of that dissipated as heat, necessitating robust cooling systems.
In industrial and military applications, the infrastructure can support sophisticated circulating cooling systems, potentially incorporating chillers and high-grade water purification systems like distilled or deionized water. Military systems, due to mobility and weight constraints, often use hybrid systems to operate under extreme conditions.
Depending on the industry, different coolants—ranging from tap water to more sophisticated mixes like water-glycol or specialized non-water-based coolants—are used. While some industries use fluorocarbon or hydrocarbon liquids, others might use non-conductive oils, like those found in oil-cooled transformers.
In summary, while various cooling systems and infrastructures can support liquid-cooled applications, the choice often depends on the specific needs and constraints of the industry.
In capital-intensive sectors like semiconductor manufacturing and heavy industry, the infrastructure allows for advanced and intricate circulating cooling systems. These can include chillers to cool below ambient air temperature, thereby enhancing system reliability. High-grade water purification systems, such as those using distilled or deionized water, are often integrated to ensure optimal performance.
Military applications, due to their need for mobility and compactness, often use hybrid systems to balance investment with operational requirements. The choice of coolant can vary widely based on the industry. Tap water is common, but more sophisticated options include distilled and deionized water, both chemically inert and free from ions. To prevent freezing, water is often mixed with glycol compounds like propylene glycol.
Some specialized applications can't utilize water at all and instead rely on fluorocarbon liquids, hydrocarbon liquids, or non-conductive oils. Oil-cooled transformers are a common example. While propylene glycol mixes offer better weather resilience, they may not be the best for heat transfer. Ultimately, the cooling system used depends on the specific needs of the industry.
Addressing the most common infrastructure for liquid-cooled applications, water remains a preferred choice due to its availability and efficiency. When processed and kept clean, water recirculation systems reduce contamination and water consumption while maintaining consistent quality with minimal maintenance. Typically, these systems pump water through a facility, recirculating it through a radiator that dissipates heat, reducing the temperature by about 5°F before routing it to cooling towers. These towers use large fans and sometimes dripping water to ultimately release the heat into the atmosphere.
Despite their complexity and high initial investment, such systems are justified in places like data centers, food and beverage processing plants, large industrial processes, and marine systems, where managing large amounts of heat is crucial.
When chillers are added to the setup, they offer the advantage of significantly extending the life of electronics by cooling them below ambient temperatures. For instance, reducing the temperature by 10 degrees can double the life of electronic components. However, chillers require a considerable investment, regular maintenance, and additional cooling agents, making them suitable only when the system's longevity justifies the costs.
Our target is to maintain temperatures between 100 and 105 degrees Celsius for all passive and active components. But what if we could reduce it by an additional 10 degrees? Remember, every 10-degree drop in temperature can significantly slow down chemical activity, effectively doubling the lifespan of electronic components. By investing in a chiller, even with its modest initial cost, you can potentially extend the life of your electronics from 10 to 20 years or even from 20 to 40 years.
However, it's important to weigh the pros and cons. While chillers are excellent for reducing temperatures and prolonging the life of your systems, they require significant financial investment, regular maintenance, and additional cooling agents. These systems are substantial in size and come with higher operational costs. But when the longevity of your system justifies the expense, chillers become a worthwhile investment.
Astrodyne TDI offers several liquid-cooled product solutions. Some specialized applications require unique cooling systems where traditional infrastructure isn't available. In these cases, the electronics are placed inside an oil tank. The oil's natural mobility creates a churning effect as it heats up and moves to cooler areas, providing effective cooling. These portable systems are ideal for environments where external coolants can't be used, such as in large vehicles like trucks. They can even be submerged in water for deep-immersion applications.
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Immersion cooling Typical coolant: mineral oil |
Direct cooling via cold plates Typical coolant: tap or distilled water |
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Other systems use a cold plate to transfer heat to a cooler surface. The user can then determine the best method for cooling, whether by splashing water or attaching another cold plate.
Liquid Cooled Power Supplies Cooling Types
Tap Water
Tap water can be used as a coolant, depending on its quality. While easily accessible, tap water varies significantly in quality across different regions, even within the mainland U.S. In some areas, it's as good as bottled water, while in others, mineral buildup can cause significant issues, leading to corrosion and system failure within months. For short-term, basic cooling needs, tap water can be an option, but it’s crucial to consider the risks of contamination and corrosion.
Distilled Water
Distilled water is another option, offering good conductivity and being cost-effective for short-term use. However, it requires substantial infrastructure to produce in large quantities and can degrade certain materials like gaskets and plastics. Creating and maintaining distilled water systems also demands considerable energy and maintenance.
Deionized Water
Deionized (DI) water is highly effective for industrial use, especially in sensitive and scientific applications due to its excellent thermal conductivity and chemical inertness. However, DI water production is expensive and requires specialized equipment. Additionally, DI water can corrode certain metals, such as copper, over time.
In summary, choosing the right coolant depends on your specific needs and constraints. Whether you opt for tap water, distilled water, or deionized water, each has its own set of advantages and disadvantages that must be carefully considered.
Astrodyne TDI Liquid Cooled Power Supply: Coolant Recommendation
In our operating manuals, we highly recommend a mix of ethylene or propylene glycol due to one of its fundamental properties: it doesn't freeze. We typically design our products to withstand temperatures as low as -40°C. This means that even if the product is stored for an extended period in such extreme conditions, the coolant must remain liquid and flow freely when the system is activated. Ethylene glycol, in particular, functions effectively down to -50°C. Its widespread use in the automotive and military sectors has made it economical and improved its quality over the years.
Ethylene glycol is also notable for its stability; it doesn't degrade over time or accumulate contaminants, making it a reliable and user-friendly option. Its availability has increased in the commercial market, further enhancing its practicality. However, it’s generally suitable for small-scale local systems due to its thermal performance. The addition of glycol does reduce the coolant’s ability to absorb and transfer heat compared to pure water, but it remains a viable solution within its limitations.
One critical point is that ethylene glycol is a chemical, and its toxicity requires careful handling and disposal to meet environmental guidelines. This adds another layer of consideration when choosing the right coolant for your system.
Liquid Cooled Power Supply: System Maintenance
Maintaining a high flow rate with minimal pressure drop is essential for efficient coolant circulation. In industrial settings, the plumbing system is designed to handle multiple heat loads, requiring a low-temperature gradient to ensure consistent performance.
Whether using series or parallel configurations, as in our systems where up to 30 units can be daisy-chained, ensuring smooth coolant flow is crucial. Occasionally, systems are divided into smaller banks to manage flow more effectively. Ultimately, a combination of compatible coolant, robust system design, and specialized thermal management is vital for long-term reliability.
Temperature and humidity also play significant roles. Sustainable practices and attention to environmental regulations are crucial in both electronics and cooling systems. Regular maintenance, including flushing, corrosion monitoring, and filter replacement, is fundamental to keeping the system in optimal condition.
Environmental and safety concerns are paramount. Ensuring the coolant is environmentally friendly and compliant with disposal regulations is essential. Most coolant systems operate in closed loops, reducing the risk of leaks and making them easier to manage. Proper disposal and recycling practices ensure that the system remains sustainable and safe for human operators.
In summary, choosing the right coolant not only ensures efficient thermal management but also requires practical and environmental considerations. Our team of experts has extensive experience in selecting and maintaining the best coolant solutions to meet these diverse needs. To delve deeper into our liquid-cooled power supplies and discover how they can elevate your systems, we encourage you to reach out to our knowledgeable team.