Colder Water, Cooler Air: The Impact on Cooling Efficiency in Air Units

[TSN79]

If a cooling element in an air unit was designed for water temperatures of 7C in and 12C out, how much "better" will it become if it receives water at 2C ? Let's say the return is then 7C, will the effect then be the same since the delta T is the same as it was with 7/12 ? It just seems so logical to me that bringing colder water in will result in cooler air...

 

[mgb_phys]

Correct, although you won't get quite 5C colder air, the greater water-air temperature difference will cause more heat to flow but it will also increase the effects of anny thermal resistance.

 

[russ_watters]

This is called improving your "approach temperature". A bigger approach temperature will improve heat transfer and therefore you will pull more energy out of the air. So the delta T will go from, say, 5 C to 6C and you'll get perhaps 8 C return water. Of course, the approach temperature of the chiller that is making that water gets worse when you do that...

 

[TSN79]

Thx guys, just one more thing; if this will indeed make the air cooler, how can I calculate the total effect in Watts?