Retrofitted IDVs could produce 7.3% gain

DENMARK: Danfoss claims that lab tests have proven that intermediate discharge valves (IDV) retrofitted on air conditioning compressors could yield a 7.3% system-wide gain.

At a time when air conditioning companies worldwide are responding to challenging targets for energy efficiency, the IDV technology, launched last year, is said to dramatically improve scroll compressor efficiency when the system is under partial load.

This is especially important in Europe, where Eurovent data is said to have shown that 80% of today’s air conditioning chillers would fail to meet minimum energy performance standards.

The new IDV technology is being rolled out now. And because the new compressors are backward-compatible with its existing products, Danfoss says they can be exchanged like-for-like, with minimal redesign costs.

Tests are said to have confirmed a significant, system-wide benefit of 6-12% depending on the system type. In test conditions, this change alone improved a rooftop unit’s Seasonal Energy Efficiency Ratio (SEER) by 7.3% from 3.43 to 3.68: enough to exceed the challenging Tier 2 Ecodesign target.

The tests also validated Danfoss’ new simulation model, which allows manufacturers to compare the system-wide effects of component and guide their design choices. At every load point, the simulator predicted the real results to within 1%.

“A designer might wonder about the SEER impact of increasing the size of the condensing coil by 2K or how a system might perform in another region,” explained Matthieu Stoll, Danfoss’ global marketing manager for air conditioning compressors. “For example, this same RTU design scaled to 60Hz would yield 14.02 IEER, above the DOE 2023 target. We can now help OEMs to predict on the impact of the system performance with less physical testing of expensive prototypes.”

Importantly for OEMs, this change is effectively a like-for-like replacement within an existing design. The new scroll compressors are backward compatible with the existing Danfoss S and H ranges – minimizing redesign costs. Danfoss has already deployed IDV technology to its full range of DSH scroll compressors (ten sizes from 7.5TR to 40TR and soon a new 50TR size) and part of the VZH series (variable speed compressors from 28cc to 65cc).

All the tests took place in a double psychrometric room at the Danfoss compressor factory in China. It is one of a growing number of Danfoss test facilities around the world, which the company is making available to select partner OEMs. Three new test rooms at the Danfoss Application Development Centre in Florida expands this capability still further – testing chillers to 150T, and rooftop units to 50T.