DRY EVAPORATOR RATING CONVENTION

[lippy]

Hello fellow knowledge seekers,
We make custom hvac/refrig. system dedicated for particular close tolerance lab conditions. We match a ceiling mounted evaporator to the room load and to a Copeland condensing unit that has compressor, condensor, receiver pre-assembled.
The evaporator coil manuf. rate there coil at (x) btuh per
10 degree F. delta T. This gives a slope to a line we draw on the particular compressor curve chart. We then make sure we pick up the room heat load under this (capacity to temp.(x)) compressor curve.
Now, I am told that this 10 degree delta T is the difference between the liquid suction temp in the coil and the room condition (coil EAT). I was wondering why the delta is not the difference between the liquid suction and the leaving air temperature (LAT) from the air handling coil. Does this have something to do with LMTD which I kinda recall from heat transfer? Most people here think I'm being anal about things. Thanks, friends.

 

[imok2]

lippy: You said, "Now, I am told that this 10 degree delta T is the difference between the Refrigerent suction temp in the coil and the room condition (coil EAT". This is correct! To get the MTD you take the room temp. minus the Refrigerant (suction temp) and air off the coil minus the refrigerent(suction) temp add them togather and devide by 2. This gives you the MTD

 

[imok2]

One more thing low temp rooms (boxs) run at a 10 * TD where as Air conditioning coils usually run a 15*F TD coil