Airsys’ Yunshui Chen: One Cooling Mission, From Telecom to AI

Yunshui Chen often recommends the book “The Lessons of History,” by Will and Ariel Durant, because it reminds him that technology changes much faster than human nature. As founder and CEO of Airsys, he has spent 31 years testing that idea in the business of keeping computers cool. 

Chen formed Airsys in 1995, when China was building telecom networks faster than conventional cooling could protect the digital equipment going into them. Conventional comfort cooling could not deliver the reliability those demanding environments required. Chen could see that thermal management was about to become a fundamental constraint on the industry’s growth, and he built a company to address it.

Three decades later, Airsys’ mission remains the same, Chen says: “Remove the physical barriers that stand in the way of digital progress.”

In the AI era, the barriers have changed. Today’s workloads require concentrated computing power at densities far beyond those of most telecom facilities, and cooling, electricity and water have become limiting resources.

Chen’s way of looking at the problem has not changed.

“I can think simultaneously as an engineer, an entrepreneur and a student of history,” he says. “It helps me connect technical details with a much longer view of where an industry is going.”

That view is visible in how Airsys is built. The company develops air cooling, single-phase liquid cooling, two-phase technologies and heat-rejection systems, and that breadth, Chen says, means the company “can design around the customer’s complete computing environment rather than force every load into one technology.” That portfolio reflects Chen’s belief that the transition to liquid cooling will take years and will be hybrid rather than binary.

This same long view shapes how he leads. Asked how he wants to leave his mark on the people who work for him, Chen says he wants them “to become more capable, more confident and more independent than when we began working together.”

“A leader’s greatest legacy is not a group of followers, but a new generation of leaders,” he says.

Hybrid, Not Binary 

No one cooling technology is ideal for every application, Chen says. Each has limits. Immersion cooling delivers excellent thermal performance, but servers have to be installed and serviced inside fluid-filled tanks, which changes the data center’s physical layout, its maintenance procedures and its equipment ecosystem. Conventional cold-plate direct-to-chip systems are more familiar to the industry, but they place conductive, water-based fluids close to high-value electronics and require carefully engineered cold plates, manifolds and connections. The resulting systems can carry significant equipment and installation costs, he says.

His picture of the next several years is a facility running all of it at once.

“A data center may have conventional servers, liquid-cooled AI racks, low-temperature support loads and extremely high-density processors operating in the same facility,” he says.

Air handles the lower-density and residual loads. Single-phase liquid can support many current CPUs and GPUs, and two-phase cooling goes where heat flux is most demanding. Each connects to the high-, medium- or low-temperature heat-rejection loop that suits it.

Operators who assemble that mix from several vendors inherit the seams between them. Chen lists the risks that collect at those boundaries: controls integration, water chemistry, hydraulic balance, commissioning, maintenance and performance accountability. Owning every layer lets Airsys take responsibility for the whole system. 

“We are not trying to sell one cooling product everywhere,” he says. “We are trying to optimize the entire infrastructure around the customer’s computing requirements.” 

The Megawatts That Never Reach the Servers 

Chen would rather talk about Power Compute Effectiveness, or PCE, than power usage effectiveness, the industry’s standard PUE metric.

PUE measures the relationship between a data center’s total energy use and the energy consumed by its IT equipment. It does not, by itself, reveal unused provisioned capacity. A facility might have a 100-megawatt utility allocation but still be able to deliver only 60 or 70 megawatts to IT equipment. The remaining capacity may have been reserved and supported by facility investment yet cannot be converted into computing output.

Airsys defines PCE as the usable power available to IT and computing equipment divided by the total power capacity provisioned for the facility. It is a capacity-utilization metric, not an established replacement for PUE.

“It reveals how much of the power that an operator has purchased, financed and built can actually produce computing output,” Chen says.

He sees the two metrics as complementary. PUE measures operating efficiency. PCE measures utilization of the facility’s most constrained and valuable resource. For an existing data center, improving PCE can release substantial capacity without waiting years for a new utility connection or constructing a new facility. That is the version of the problem an entrepreneur sees, and it is the one Chen keeps returning to: how much productive computing the industry can get from every available megawatt.

Beyond the Chiller 

Chen has said publicly that mechanical chillers will eventually be eliminated from data center infrastructure. He treats the prediction as a specification.

Chillers are necessary, he explains, when IT equipment needs coolant colder than the outdoor environment can reliably supply. Eliminating them means moving the entire thermal chain to higher operating temperatures. Servers and cooling components have to be designed and warranted for warmer coolant. Liquid cooling must capture nearly all of the high-temperature heat at its source, so that very little load still needs low-temperature air. Then dry coolers, two-phase systems, heat exchangers and controls get engineered as one integrated high-temperature system. Extreme weather is handled through properly sized heat-rejection equipment, thermal storage or limited trim cooling during exceptional hours.

“Chillers will not disappear from every data center at the same time,” Chen says. “However, I believe mechanical refrigeration can cease to be the default solution for high-density AI facilities. As liquid temperatures rise and heat capture improves, many data centers will be able to reject heat directly to the outdoor environment for most — or eventually all — of the year.”

The same higher temperatures also bear on the question communities are asking about water. Zero onsite water consumption for heat rejection is technically achievable today, Chen says, through dry coolers, air-cooled systems and closed-loop liquid cooling. He is careful with the term. A closed-loop system still needs an initial fluid charge and occasional maintenance. Electricity generation carries its own upstream water footprint. In very hot climates, avoiding evaporative cooling can require more heat-exchanger surface, higher airflow or more energy.

“The warmer the liquid leaving the servers, the easier it becomes to reject that heat directly to outdoor air,” he says. 

Airsys works from the chip outward: capture heat at a higher temperature, minimize low-temperature loads and design the dry-cooling and control systems around those conditions.

“Zero onsite water consumption for heat rejection is not simply a choice of outdoor equipment. It is a complete system architecture,” he says. “Properly designed, it can support large-scale AI development without placing an unsustainable demand on local water resources.”

An Energy Company 

Chen has called Airsys an energy company rather than a cooling company. His reasoning starts with what the customer is buying.

“Customers do not ultimately purchase cooling; they purchase productive computing within a limited power envelope,” he says. “Cooling is one of the places where power is either preserved for computing or consumed as overhead.”

Thinking like an energy company changes the engineering objective. The team considers how every watt moves through the facility, how much becomes useful computing capacity and how much is lost to conversion, cooling and distribution. It also weighs water consumption, equipment life, heat reuse and the embodied resources in any new construction.

The company’s phrase for this is “Balance the Environment.” Chen defines it as balancing the growth of the digital economy against the limits of the electrical grid, the natural environment and the communities hosting these facilities. He insists it be expressed through engineering: higher-temperature cooling, reduced fan and pump energy, water-free heat rejection, longer equipment life and more computing output from existing infrastructure. Sustainability that does not improve the customer’s economics, in his view, does not scale.

“The most durable solutions are those that reduce environmental impact while increasing the return on invested power,” he says.

Made in Woodruff 

In May, Airsys opened the first phase of a 60-acre global headquarters campus in Woodruff, South Carolina. It will house a large-scale 3D-printing operation for cooling components.

Chen says U.S.-based manufacturing brings engineering, production and customer deployment closer together. Customers building critical infrastructure need traceability, consistent quality, secure supply and responsive technical support, along with confidence that their cooling partner can scale with them. Working directly with Airsys engineering and production teams during development, testing and qualification shortens the loop between field performance and product improvement, and it strengthens lifecycle service after installation.

The printers also change what Airsys can design. Complex internal flow paths, heat-transfer geometries and customized components that would be difficult or impossible to machine conventionally can be produced additively, avoiding some of the constraints of conventional machining. That shortens the path from design to prototype, qualification and scaled production.

“The Woodruff campus is more than a factory,” Chen says. “It is a commitment to technological development, manufacturing accountability and long-term participation in the North American data center ecosystem.” 

Inside the Server 

Airsys’ server-level liquid cooling architecture, LiquidPack, delivers dielectric fluid directly to the principal heat sources inside the server through a spray mechanism rather than immersing the whole rack. It captures heat at the chip and preserves much of the familiar rack configuration and service workflow. Properly designed, Chen says, it combines high heat-transfer capability with a relatively small fluid inventory and strong electrical safety.

The tradeoff is precision. Spray distribution, sealing, fluid management and system controls all have to be engineered exactly. He sees particular value in brownfield retrofits, mixed server fleets and facilities that need more computing density without rebuilding their white-space infrastructure.

Two-phase cooling goes further. It uses the latent heat absorbed when a fluid changes from liquid to vapor, allowing the fluid to remove substantial heat at a nearly constant temperature. Compared with single-phase cooling, it supports much higher heat fluxes, reduces temperature differences across the chip and can operate with lower fluid-flow requirements. That can mean smaller components, lower pumping energy and more uniform chip temperatures as processors move toward multi-kilowatt thermal loads. The engineering challenge is greater. Boiling stability, pressure, vapor transport, condensation, material compatibility, fluid containment and long-term serviceability all have to be controlled.

Chen does not see two-phase replacing what came before. He describes the cooling roadmap as an integrated spectrum. Air will keep handling legacy equipment and lower-density components, and single-phase liquid will be the workhorse for much of the market. Two-phase will matter most at the leading edge, where conventional cold plates approach their practical limits. 

Looking Ahead 

Asked what has to be true for AI infrastructure to keep scaling at the pace the industry expects, Chen answers like someone who has watched a buildout before. Cooling technology must become standardized, manufacturable and serviceable at scale, “not merely thermally impressive in a laboratory.”

“Servers, electrical systems and cooling infrastructure must be designed as one system,” he says. “The industry will need higher coolant temperatures, standardized liquid interfaces, clear warranty responsibilities, water-conscious heat rejection and practical upgrade paths for existing data centers. It must also develop the manufacturing and service capacity required to deploy these technologies across thousands of sites.”

Airsys’ role is to connect those layers: air, single-phase liquid, two-phase and heat-rejection technologies, together with system controls, manufacturing and lifecycle support. Chen wants to help operators unlock stranded capacity in existing facilities and design the next generation of high-temperature, zero-water AI infrastructure.

“If we succeed, cooling will no longer be the constraint that determines how quickly AI can grow,” he says.

Technology changes much faster than human nature. That is the theme Chen takes from “The Lessons of History.” Every technology in this story, from the telecom equipment Airsys first protected to the two-phase components it is developing now, has a shelf life. The things that outlast them are human: the need for reliable computing, the limits of the grid and the communities that host the facilities, and the judgment of the people who decide how to work within them. Thirty-one years in, Chen is still building for the slow-moving side of the equation.