Difference temperature in supply and discharge water in a chiller

Hi
I am a new engineer in a consultant company. A chiller manufacturer company suggest us to Manufacture a chiller which is work with 6 degree celsius as a supply and 15 degree as a return to evaporator and it said that it is goning to be better as efficiency.
That's my question if it is better or not?! And how does it affect on air handling units?!

Thanks It’s not clear what your question or point of comparison is but generally speaking:

The higher the operating temperatures of your chilled water system, especially your return water temperature - the more efficient your chiller will be as far as heat exchanged compared to electrical consumption

But having a higher chilled water temperature and/or a larger delta T (difference in supply and return) will means you will need bigger coils in your air handlers to exchange the same amount of heat and also you may not be able to reach discharge air temperatures from your air handler as cold as you may want This is a complicated question and depends on the chiller you have. Hopefully the manufacturer has performance and efficiency curves showing what your chiller output is when you increase your chiller delta T. You really just have to look through that to find your answer as to whether or not your chiller performance improves by operating at 44-60 EWT/LWT temps, and reducing your flow accordingly.

AHRI conditions you mention are just to provide like for like comparisons between chillers, but not to be used to determine your actual operating efficiency.

You will definitely saving pump energy, since higher delta T means less flow to cover the same load. As far as the chiller goes, I'd defer to the chiller catalogue which hopefully will demonstrate the difference by looking through all their performance tables. Chiller efficiency generally speaking is typically maintained by keeping your chiller or chillers running in the 65-85% capacity range, and is definitely improved by raising your entering water temperature. But as far as delta T goes, I don't have that boiler plate answer for you - since each chiller is unique as far as compressor quantities, compressor modulation capabilities, etc. Chiller Outlet temperature should be 44°F (6.7°C)as per AHRI.

Capacity calculation of chiller is based on dT (differential of Supply and return temperature) and manufacturer usually provide part load characteristic of chiller and efficiency at that load. If outlet temperature of your chiller is 15°C (59 F), what will be the return (Inlet) temperature? will this 15°C (59 F) sufficient to meet cooling of building?

AHRI req. 44°F chilled water supply temperature at 2.4 gpm per Ton. I believe, AHRI did required inlet temperature to be 54°F (12°C), which you have mentioned in your statement. jrrocks - Not really - it just means there is more water flowing around the system for the same load surely?

Back to the OP - the vendor says it is going to be "better"... Better than what?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

Advantages of Water-Cooled Chillers

Lifespan

Water-cooler chillers have longer lifespans than air-cooled chillers. This is because water-chillers aren’t exposed to outdoor elements such as rain, snow, ice, or heat, thus they are more protected.

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Quiet Operation

Water-cooler chillers operate quietly, while air-cooled chillers have ducts and vents, that may get quite noisy. The flow of water through the system is quite unnoticeable, compared to the contraction and expansion heard in air-cooled chillers.

This “silence” or quiet operation is quite beneficial in environments such as hospitals, or schools, where noise can become a nuisance to the occupants.

Energy Efficiency

The film coefficient is 10 to 100 times better in water-cooled chillers vs air-cooled chillers. This is because water-cooled chillers transfer heat more efficiently, and this results in savings on energy costs for businesses.

No Open Space Needed

Water-cooled chillers are placed inside buildings, which makes them great for companies that don’t have access to enough outdoor space. Air-cooled chillers stay outdoors and require an open space with fresh air to operate.

Safety

Water-cooled chillers use water as a refrigerant instead of toxic chemicals. This inevitably makes them safer for people who have frequent contact with them.

Disadvantages of Water-Cooled Chillers

Higher Cost

Air-cooled chillers are cheaper than water-cooled chillers since they don’t require parts like cooling towers or condenser water pumps. However, many companies feel that the longer lifespan of water-chiller, and their savings on energy, more than makeup for the initial purchase price.

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More Maintenance

Water-cooled chillers have more parts to take care of than air-cooled chillers, thus they require more maintenance. This means more periodic inspections, water treatments to remove impurities, and regular cleaning of the chiller’s machinery.

Since water-cooled chillers have more parts than air-cooled chillers, they also likely require more frequent repairs than air-cooled chillers.

Complicated Installation

The additional parts that a water-chiller has, inevitably leads to a harder installation, than in the case of an air-cooled chiller. This may mean higher labor costs for installation, compared to the air-cooled chiller.

Mechanical Room

You need to have a mechanical room to house a water-cooled chiller, to ensure that it will function properly with its cooling tower and extra components.

Not Good for Drought-Stricken Areas

Water-chillers use quite a large amount of water, and thus they aren’t suited for regions that have water shortages. The money spent on the water in these regions can leave you with a big pocket hole.

Less Efficient in Humidity

Though water-cooled chillers are mostly more efficient than air-cooled chillers, they won’t operate as efficiently in humid environments. This is because humidity raises the wet-bulb temperature, which indicates how efficiently water absorbs heat. Water-cooled chillers in humid environments may also affect the workers, making them feel cold or clammy.

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