Condenser water flow limitations

[engsam74]

I would like to know the basis of having a minimum condenser water supply temperature condition (ex: 60 F) and minimum condenser water flow. What are the key factors determining these two conditions.
Also, if the manufacturer specs say that the min. CWST is 60 F, can you go below that by reducing your flow using a VFD on the pump. Any light on VFD control of a condenser water pump based on the refrigirant diffential pressure between evaporator an condenser will be much appreciated.

 

[imok2]

"I would like to know the basis of having a minimum condenser water supply temperature condition (ex: 60 F) and minimum condenser water flow. What are the key factors determining these two conditions".

1. The first condition is better energy efficiency.
2. The second condition is usually considered when first cost is high like long pipe runs and many valves.

"Also, if the manufacturer specs say that the min. CWST is 60 F, can you go below that by reducing your flow using a VFD on the pump".
Not likely, as your cwst is based on wet bulb temperature and normal tower approach is around 7or8 degrees which means if wet bulb say is 70*f then water off would be 7 or 8 degrees higher. If the mfg. says to stay above 60*f then thats what you should do because you need to maintain a minimum head pressure for the chiller to function properly. I recommend you read this article

http://www.york.com/products/esg/updates/eng-Updates/22.pdf

 

[HVAC68]

1. Operating at lower than the recommended condenser entering water temperatures may cause the unit to shut down on low oil pressure alarms.

2. Lesser flow than recommended would in turn result in a lower velocity through the condenser tubes, thereby hampering heat transfer due to lack of turbulent flow and hence a lower Reynolds number.

HVAC68