View Full Version : DT of water heat excanger

Renato RR
26-02-2006, 11:57 AM
Why all chiller manufacturer vants 5 to 7 C DT.Would it be so bad to have 2 to 3 C DT?
Q = m c DT in boath case.When changing DT ,m rises so Q is the same.I know I miss something can some of you open my eyes.

Best regards,

26-02-2006, 12:09 PM

Larger td means a smaller evaporator, cheaper solution.

The dt you are refering to is the difference between the fluid on and off the chiller temperature. This relates to the design of the air side heat exchanger (air handling unit) or the process side heat exchanger. Most designs refer to a 6 to 10 td on the airside, again to keep the coil size down and the cost of the airside haet exchanger.

Kind Regards. Andy:)

26-02-2006, 02:05 PM

As Andy said, if you go down on dt, the 'm' - flow rate of liquid through the evaporator - increases, hence the bigger evaporator size. But this means also a bigger evaporator pump, increasing your investment/initial cost. Now, with a bigger pump your running cost will be also higher.
So, you lose on both initial and running cost.