Evaporative condenser winter heat rejection

[hladotech]

Dear speculators,

Could somebody explain the next evaporative cond. observing:
BAC VXC110 507a
in summer at 35C/35% Tc=40C 100% fan power, dT=15K
in winter at -6C/80% Tc=30K 100% fan power, dT=36K
So it's looks like evaporative condenser in winter operation can't evaporate water and comes to almost clear heat exchange without evaporation, like dry condenser but with poor heat exchange surface.
Am I right?

[Segei]

dT is wet bulb approach. I checked your numbers and got summer dT=17K and winter dT=37K. Yes. At lower ambient temperatures evaporative condenser become less efficient because properties of wet air are different. I looked at IMECO table of capacity factors for evaporative condensers. To achieve wet bulb approach of 10F, at wet bulb temperature of 75F(24C) capacity factor should be 2.72. To achieve the same approach of 10F at wet bulb temperature of 50F(10C) capacity factor should be 3.53. It means capacity of the condenser should be 40% greater.
However, even at reduced efficiency capacity of wet operation of the evaporative condenser is much greater than capacity of dry(just air) operation.

[hladotech]

Thank you Segei.

E-C good in dry summer, but at saturated winter dry cond. is much better 'cause you can go down to minimum cond. pressure. But there is the decision - using of cooling tower instead of e-condenser to achieve good ESEER.

[Segei]

E-Condensers are good for summer and for winter. Hybrid e-condensers can use benefits of cold air during winter operation. Minimum condensing pressure can be achieved with any e-condenser but it should not be undersized like in your case. I know a few ammonia plants with e-condensers which run at condensing pressure as low as 60 psig(4 bars).
I believe that book of Wilbert Stoecker "Industrial Refrigeration Handbook" is the best book for industrial refrigeration. On pages 266-269 he showed that e-condenser is more efficient than cooling tower+water cooled condenser. Additionally, he explained why evaporative condenser is not so efficient at low ambient conditions. If you have a chance, look at this book.

[milbach]

E-Condensers are good for summer and for winter. Hybrid e-condensers can use benefits of cold air during winter operation. Minimum condensing pressure can be achieved with any e-condenser but it should not be undersized like in your case. I know a few ammonia plants with e-condensers which run at condensing pressure as low as 60 psig(4 bars).
I believe that book of Wilbert Stoecker "Industrial Refrigeration Handbook" is the best book for industrial refrigeration. On pages 266-269 he showed that e-condenser is more efficient than cooling tower+water cooled condenser. Additionally, he explained why evaporative condenser is not so efficient at low ambient conditions. If you have a chance, look at this book.

Agreed. Even if the summer is mildly humid, evaporative condensers/dry coolers works well. Regarding the efficiency, we have checked this one (http://www.kaltra.de/bora-dry-coolers) and found it works perfectly at the humidity of up to 55-60%. Pads can be removed for winter time.