ACRC celebrates 30 years of societal impact

In the late 1980s, damage to the ozone layer began to rapidly increase. This was due in part to an accelerated introduction of chlorofluorocarbon (CFC)—and other compounds that contain chlorine—into the ozone layer. Under proper conditions, chlorine can destroy large amounts of the ozone, so international agreements began limiting certain refrigerants. At the time, a DuPont executive and Illinois alumnus knew that the university was working on research for automobile and refrigeration companies, and he returned to the university to propose a collaboration to address this issue.

MechSE Professor Clark Bullard (now professor emeritus) helped facilitate grants from the estate of Richard W. Kritzer, the Illinois Governors’ Science Advisory Council, and the National Science Foundation. He also suggested expanding this research endeavor to include other companies across the industry. With this introduction, the Air Conditioning and Refrigeration Center (ACRC) at the University of Illinois was born, with Bullard and Roy Crawford (then an assistant professor in MechSE) at the head. This year marks the 30^th anniversary of the ACRC.

Now powered by more than 100 researchers, including about a dozen faculty and their students from MechSE, and funded by 30 industry partners, the cooperative research center strives to develop more energy-efficient equipment and technology for advanced air-conditioning and refrigeration systems, and to create solutions to address industry challenges. The focus of the industry partners is on increasing energy efficiency and reducing environmental impact of HVAC&R equipment. New technologies such as two-phase ejectors that are now being commercialized are just one of many examples of the center’s successful R&D output.

This industry-university collaboration has been at the heart of the ACRC since its creation. At their annual brainstorming session, the industry advisory board ranks the issues they need to address, and center researchers select the topics they will work on.

The ACRC has been funded entirely by industry support for the last 20 years, and the relationship is mutually beneficial. Companies use the center’s research findings to improve upon and create new product designs, and the researchers publish work that can then be applied.

This cross-pollination of industry needs and university research is “one of the greatest advantages of the ACRC. It provides opportunity for interaction between the technology gatekeepers of the industry with university researchers interested in developing fundamental knowledge that can be put in practice,” said Pega Hrnjak, research professor and director of the center since 2015. Hrnjak joined ACRC in 1993 and was its associate director and then co-director with Professor Tony Jacobi until 2015.

This collaborative approach also led to the creation by Hrnjak of Creative Thermal Solutions, Inc. (CTS), a university spin-off company founded in 2004 to better address the need for executing HVAC&R research projects for which industry sponsors request confidentiality. Stefan Elbel, an assistant research professor in MechSE, joined Hrnjak, his graduate adviser, at CTS as chief engineer, after earning his PhD in 2007. He has been involved with the ACRC since 2001, when he was a graduate student. Elbel is now one of the center’s associate directors.

For years, the ACRC has stood at the forefront of development and understanding of flow in small channels, as well as microchannel heat exchangers.

“The study of microchannel heat exchangers and chillers for ammonia with reduced charge is one of the very important projects that the ACRC has been involved with, along with transcritical CO2 systems,” said Hrnjak. “Our work on visualization of two-phase diabatic and adiabatic flows with or without oil, nonequilibrium heat transfer, developing two-phase flows, new control strategies based on subcooling, to mention just some, are making an impact in science and industry.”

In addition to heat exchangers, the ACRC has expanded its research scope to include materials development for advanced coatings.

“The ACRC is leading the charge on developing durable functional coatings for enhanced heat transfer, anti-icing, anti-fouling, and anti-corrosion in HVAC&R applications,” said Assistant Professor Nenad Miljkovic, another of the center’s associate directors. “The synergistic combination of fundamental studies led at Illinois with applied proof-of-concept experiments directly on ACRC member company equipment has given us the leading edge in this area.”

The ACRC’s ability to leverage industrial know-how and scale with Illinois’ fundamental science have resulted in competitive multi-year federal grants.

“The ACRC has been a tremendous help to my success as junior faculty at Illinois, not only in terms of external funding, but also in guiding the fundamental research direction of my laboratory toward industrially and societally relevant problems which I was unaware of prior to joining the center,” said Miljkovic.

Jacobi, MechSE department head and former co-director of the ACRC from 1997 to 2015, has been involved with ACRC since 1992 and has also seen the benefits the center brings to MechSE and his research program.

“The center provided a way for me to interact with industry and conduct research that’s relevant to society because of its industry-driven focus. It is also the premier center of its kind in the country and the world,” he said. 

ACRC leaders are planning for a future of continued preeminence.

“The ACRC’s research focus in the years to come will be on developing technologies that will result in even more sustainable heating and cooling solutions for both traditional and new applications. One of the center’s core responsibilities is to maintain a fresh eye and to advance emerging energy transformation approaches that one day could replace the century-old vapor compression technology that currently dominates the industry,” said Elbel.

Photo at top: Past, current, and future leaders of ACRC: Hrnjak, Elbel, Jacobi, Bullard, and Miljkovic.