Purdue University engineers have developed a second-generation smart accumulator with oil circulation ratio (OCR) sensing capabilities for heating, ventilation, air conditioning and refrigeration, or HVAC&R, systems.

Oil starvation is one of the major reasons for compressor failure in HVAC&R systems. The Purdue smart accumulator OCR sensor could provide better insight about the oil flow within a system. It would address the failure and improve the reliability of the overall system, especially one running with variable-speed compressors. The sensor also would support the efficient operation of new systems that use alternative, low global warming potential refrigerants, thereby reducing carbon footprint and increasing energy efficiency.

In 2020 Vatsal Shah, a former Ph.D. student, who graduated from the School of Mechanical Engineering in 2021, and other researchers in the school and the Ray W. Herrick Laboratories at Purdue developed a methodology to monitor OCR in real time for HVAC&R systems. The OCR monitor provided data on oil circulation in the system outside the compressor and the health and functionality of the overall oil management system.

The monitor was shown to industry leaders, who suggested it needed improvements to its design, which restricted its use beyond the laboratory. As a result, the group created an improved, second-generation monitoring technology.

"We were told if the technology could be developed in a small-form factor and simplified to reduce the cost, it could have great market appeal," Shah said. "A more compact product could be installed as an OCR sensor in HVAC&R equipment, leading to many possibilities for actively monitoring and managing oil by using advanced control systems."

The Purdue engineers' second-generation smart accumulator functions as well as the first, but in a small-form factor.

"Furthermore, to keep costs low and to make the technology easy to install in current and new systems, the OCR sensor was integrated with a suction line accumulator," said Parveen Dhillon, a Ph.D. candidate from the School of Mechanical Engineering. "This is a commonly used component in HVAC&R systems, which means no special equipment is needed to install it."

A prototype of the second-generation smart accumulator OCR sensor was tested within an oil management test stand at the Herrick Laboratories. Along with performing well in validation testing, Dhillon said, the sensor addresses industry feedback on design requirements.

"The developed technology allows OCR quantification in the vapor line without disturbing the system, in contrast to the commonly used sampling-based method in the liquid line, which can be tedious and time-consuming," Dhillon said.

Future tests of the OCR monitor could include a two-staged, cold-climate heat pump system that is being currently developed at Purdue as part of another research project.

Dhillon and his colleagues disclosed the second-generation smart accumulator OCR monitor to the Purdue Research Foundation Office of Technology Commercialization, which has applied for a patent to protect the intellectual property. For more information on licensing and other opportunities, contact Dhananjay Sewak at dsewak@prf.org about 2021-GROL-69502.

The other members of the Purdue team are James E. Braun, the Herrick Professor of Engineering; Eckhard A. Groll, the William E. and Florence E. Perry Head of Mechanical Engineering; Orkan Kurtulus, a former senior research engineer at the Herrick Laboratories; Frank Lee, a lead engineering technician at the Herrick Laboratories; and Haotian Liu, a postdoctoral researcher at the Herrick Laboratories.

The prototyping and validation testing of the smart accumulator OCR sensor was supported by an award from the Trask Innovation Fund, which is managed by the Purdue Research Foundation Office of Technology Commercialization.