Air cooled vs. water cooled chillers

[sheenders]

I am interested if anyone could lead me to an analysis of capital and operating cost comparison of air cooled vs. water cooled chillers. Further to that point, screw vs. helical, or other types of compressors.

 

[boilerdoc]

Hi sheenders,
water has big advantage from the thermodynamic point of view.When cooling water is available at low cost,I would prefer water cooled chillers.Of course it depends on the climatic conditions your plant is situated to give qualified advice concerning the most economical way.
For compressors it depends on the size of the chillers. But screw compressors have only two moving parts and handle large mass flows of refrigerant.Maintenancewise they have advantages compared to piston type compressors.
Hope this helps

 

[sheenders]

Setra
Thanks for the input. For more details, if we are in a moderate climate, with design temp about 75F and chiller size about 400T (each with multiple chillers needed for capacity), can you give me some more comment?.

Thanks again.

 

[quark]

Installation cost of air cooled condenser includes a condenser (generally bigger size than water cooled, so more cost) and a fan. Incase of water cooled condenser, you have to have condenser, cooling tower, pump and piping system. Insvestment on water cooled condenser is higher.But chillers have better efficiency at lower temperatures of cooling water. So overall advantage, though water cooled system seems to consume more power, is for water cooled systems.

For compressors you have to check specific power consumption (i.e kW/TR). Centrifugal chillers have stepless control for load variations. Screws come next and reciprocating chillers are worst in this case. Centrifugal chillers have better efficiency at part load conditions when compared to others.

What is this system used for? Airconditioning?

 

[sheenders]

quark
The chillers are primarily used for air conditioning, but there is also some process cooling that is used. Environmental temperature and humidity are necessary for process control. Our 'typical' installation would be about 1200t of refrigeration required and we have exclusively used air cooled units.

As you said, the water cooled systems have higher initial capital but is attractive from an energy point of view. Some of our more 'experienced engineers' i.e., the boss, says the advantages of water cooling drop off dramatically due to maintenance costs, water costs, chemical treatment, and a general drop off of efficiency.

What do you think?

 

[quark]

Your boss does have a point. It depends upon the water quality. There is also an increase in labour cost to operate extra equipment. But from a process stand point of view water cooled condenser would give you less headache. Generally wet bulb temperatures do not vary as high as dry bulb temperatures. In summer condition the efficiency of entire system drops down and it all depends upon how stringent your room condition requirement is.

 

[boilerdoc]

Consider that an air cooled condenser is also not maintenance free. Of course you need water treatment if recirculated water and cooling tower is used.Thats why I mentioned low cost cooling water like river water or well water in once through condensors.