ARLINGTON, Va. - A newly released Air-Conditioning and Refrigeration Technology Institute (ARTI) report characterizes how flattened-tube heat exchangers function under various environmental conditions and pressures.

The study, “An Assessment of the State-of-the-Art and Potential Design Improvements, for Flat-tube Heat Exchangers in Air-Conditioning and Refrigeration Applications,” found that replacing traditional round tube heat exchangers with flattened tube technology may enable the air conditioning industry to provide comfort cooling using a new refrigerant, while increasing efficiency, but not the system’s size.

“Flattened tube heat exchangers have received much attention as a possible replacement to traditional round tubes, but until now little research has been done on the thermal-hydraulic performance of flattened tubes under wet, dry, and frosted conditions,” said Elizabeth Jones, a project manager with ARTI. “This research report addresses the fundamental science needed to allow the air conditioning industry to engineer products using this technology.”

According to the report, the geometry of a flattened tube allows for improved heat transfer and thermal performance; increased coil and overall unit efficiencies; substantial refrigerant charge reduction; and more compact and reduced coil size.

In the ARTI report, University of Illinois researchers provided analysis, modeling, and interpretation of air-side, thermal-hydraulic performance for flattened tube heat exchangers under wet and frosted surface conditions. They made design recommendations to help improve the performance of plain, wavy, strip, and louvered fins for flattened tube heat exchangers. They also conducted a full assessment of the air-side thermal-hydraulic performance of flattened, round, and finned heat exchangers. In addition, researchers developed a new method to provide data on retention and drainage of water from the air-side surface of flattened tube heat exchangers under a number of operating conditions.

To read the final report, visit

Publication date:01/08/2007