delta T

[wilks]

could anybody explain how we find out if theres sufficient air flow by checking delta T ? EG how does 2 temp readings tell you if theres correct airflow across an evap or condenser?
thanks .

[wilks]

Does anybody know of any books with the above info in then?
Can you get Garys book over here in England?

[sachin230]

http://prostores1.carrierzone.com/se...com/StoreFront

[chemi-cool]

When air at certain temp flows through a heat exchanger such as evaporator, the heat in the air is absorbed by the refrigerant in the coil and the air is leaving the coil cooler.

Air flow is designed so that maximum heat is absorbed keeping air throw far enough to cool the entire aria to be cooled.

Therefore, Δt is not a fixed No. but will differ with certain situations.

[wilks]

thanks chemi , sachin ,

so delta T changes with different applications , so you couldnt just walk up to say an evap in a cold room , take delta t and work out if theres enough air flow?

[TRASH101]

could anybody explain how we find out if theres sufficient air flow by checking delta T ? EG how does 2 temp readings tell you if theres correct airflow across an evap or condenser?
thanks .

If you know the rest of the data then yes.

Transpose the formula Q=m x cp x p x dt for m

i.e. m = Q / (cp x p x dt)

m = volume
cp = sh capacity
p = density

Only any good if you know Q and its 100% sensible load

so delta T changes with different applications , so you couldnt just walk up to say an evap in a cold room , take delta t and work out if theres enough air flow? 07-07-2010 06:05 PM

You can do a decent guesstimation

[wilks]

thanks thrash

whats a good guesstimation ? or correct Delta T , how does these 2 temps tell you that you have correct airflow,
Thanks for your time

[TRASH101]

Consider this situation

A split a/c unit running at full capacity (says 5kw on the nameplate)

You measure air on at 23c and air off at 10c therefore dt =13k

5/(13 x 1.205 x 1.005)

5/ 15.73

vol = 0.318 m3/s

If this looks reasonable for the fan then OK

Get a bit more accuracy by doing the condensor the same way.

Or do it properly using anemometer/ balometer etc..

[wilks]

Arh thanks trash it's starting to make sense now.