Replacing traditional round tube heat exchangers with flattened tubes could increase the efficiency in a/c systems but not their size, according to a new report from the Air-Conditioning and Refrigeration Technology Institute (ARTI).

“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, which provided the funding for this project under its HVAC&R Research for the 21st Century program.

The geometry of a flattened tube, compared with the traditional round tube heat exchanger, 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.

The report includes analysis and modeling of air-side, thermal-hydraulic performance under multiple surface conditions, improved designs and a new method to provide data on retention and drainage of water.

To read the final report “An Assessment of the State-of-the-Art and Potential Design Improvements for Flat-tube Heat Exchangers in Air-Conditioning and Refrigeration Applications,” visit