Loss of R407c performance at high temperature

[SETCURE]

We manufacture a line of water and air cooled water chillers specifically designed for supplying chilled water at a precisely controlled temperature to small heat exchangers, which we also make. It is a niche market.

Until a few years ago, our chillers used R22 with good success. At that time, our chiller capacity was derated on a percent capacity basis for every degree above 95 deg F (35 C). When the plant cooling water or ambient air reached 105 deg F (41 C), the capacity of our units decreased, however, they continued to provide chilled water. On really hot summer days, if our customers had cooling water/air above 105 F, they could limp along by lowering the process load.

We made a change to R407c to allow us to continue to sell to the EU and in anticipation of the upcoming change in US refrigerant regulations. With minor modifications to our designs, we have seen similar performance in our current chillers as compared to our R22 versions, with one exception.

Rather than simply losing some capacity at high cooling water/air temperatures, the R407c chillers seem to completely stop chilling above about 105 F. The drop off seems to occur at an even lower temperature with our air-cooled units due to the larger inefficiencies seen with the air-cooled condensers (especially with dirty coils). It makes it difficult to sell the air cooled units in warmer climates if the maximum air temperature is only 95 F (35 C).

What other refrigerant options are out there? Changing to higher pressure refrigerants will most likely price us out of the market, so we are trying to avoid those. Other U.S. manufacturers of similar units seem to still use R22. We don’t know what their plans are for 1/1/2010.

Any suggestions would be greatly appreciated. Sorry for being long-winded!

[Gary]

You might find this thread helpful:

http://www.refrigeration-engineer.co...ad.php?t=19839

[Argus]

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It has not been possible to sell new systems utilising ODS (HCFCs) such as R22 in the EU for many years and the same EU regulation bans the use of new R22 for service from the end of this year. You already know this because you made the change.


About 10 - 12 years ago, many EU manufacturers of systems evaporating at high temperatures (typically around 0 / 32) chose R 407C because the options to use high temperature near Azeotropes such as R 410A were limited at that time by the availability of compressors and other devices. R 407C was seen as a virtual drop-in to products deigned for R22 with minimal design changes.

The main market in packaged chillers in the EU has since then shifted to R 134a in the main.

I believe that your main problem is associated with mixture quality.

The problem with R 407C was and still is, its high glide both in the evaporator and conversely in the condenser which makes predicting performance losses at extremes of working temperatures difficult.


You will only be able to scientifically check the effects of glide on performance at higher condensing temperatures in a test laboratory.



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