Air cooled / Water cooled chiller

[sevenone]

Hi,

Sorry for what might be a really noob question, but I am looking at trying to understand the potential difference in operating cost between an air cooled chiller and a water cooled chiller of equiv. size. This is in a small size situation of say around 100kw.

Water cooled chillers are supposed to be more economical however I am wondering where this is coming from. With the water cooled chiller there is the extra cost of operating the pump to pass the gycol/water out to the external condenser, plus also the cost of operating the fans in the drycooler/cooling tower.

Does anyone have a book or recommended reading which explains where the operational savings are coming from? I am especially interested in how this changes with different ambient conditions.


Cheers,

Sevenone

[install monkey]

water cooled chillers benefit from free cooling of the condenser water during low ambient temperatures,but u lose water from evaporation so the pond will req topping up-via a water meter.running costs will have to include dosing equipment,taking samples on a monthly basis.
condenser water pumps cost money whilst circulating water.also regular cleaning of the strainer(yearly) and rodding out condenser tubes (after about 5 yrs).
also the cost of installing cooling towers,pump sets,pipework,powering said items.
air cooled in my eyes is a cheaper option in installation,operating less maintenance. multiple fans and head pressure control reduce operating costs-recommend fitting inverter drives to reduce current draw on compressors.

[Tradewinds]

Hi Sevenone,
From what I understand, it's because you can absorb up to 31 times more heat energy into a liquid (water/glycol) than what you can into a vapour (ie air). So the amount of heat that can be rejected via a water cooled condenser is much greater than an air cooled equivalent.
It's the same reason why we keep an evaporator fully flooded with liquid refrigerant because we can absorb more heat from the product.


The other factor is that the evaporative condenser or cooling tower is the most efficient type because it uses two cooling mediums (both air & water) and can therefore reject a lot more heat.

[Magoo]

Packaged chillers generally come as air cooled, quick and easy install lower capital costs for install. Water cooled is more efficient due to utilizing the wet buld condition. But more capital expensive to install on site.
Most bean counters look at the initial cost of install, not the long term benefits and savings

[NoNickName]

Actually water cooled chillers are cheaper to run because water cooled condensers have a better heat exchange than fin packs and water can carry more heat per Kg or m3. The pumping energy equates the fan power of air cooled chillers, so we don't have any extra energy expenditure.

[sevenone]

Thanks for all the reply's so far.

The questions came after looking at various models available and coming across the Carrier 30RW series of chillers. These are available in two versions. One, the RWA has a R407 outdoor condenser, and then the other has an internal variable speed pump to connect to either an outdoor cooling tower or drycooler.

I am more leaning towards the drycooler to avoid all the water usage issues with a cooling tower but wanted to see if there was any benefit in operating cost with going this route over a straight R407 outdoor condenser.

[install monkey]

dont forget the power consumption of the tower fan and the pond heater !

[Magoo]

Hi Install .
Not too many pond heaters required in Australia.
Sevenone,
talk to BAC in NSW, I think they do a stainless steel model, basicaly an evap condenser with water in circuit.

[Tesla]

Hi Install
Magoo has good advise. Also you could do a life cycle costing - install, maintenance and power over expected life time of equipment. Really depends on your local conditions which AIRAH has much historical data on.