Reducing Air Flow through Dehumidifier
Reducing Air Flow through Dehumidifier
(OP)
We have an existing dehumidifier that we would like to re-purpose at a lower air volume. Has anyone had any experience with blocking off portions of an existing DX coil to reduce dehumidifier capacity?
Here's what we have: The AHU was originally specified to dehumidify 3500 CFM of air from 72*F/50% RH to about 42*F Saturated. The evaporator and condenser are in series in the dehumidified air stream and both are in the same air handler plenum as the unit's 15 ton scroll compressor. Refrigerant is 410A. Both coils were selected such that the face area is 3'x3', and the piping arrangement is full face with one distributor into the evaporator. There is hot gas-by pass, and with the heat of compression added into the dehumidified air, the air is supplied to our process at about 85*F/25%RH.
Due to process changes we are now limited to supplying about 1000 CFM of dehumidified air with the same target of 85*F/25%. We will do this for about a year, then the process will be permanently shut down. Instead of doing a complete reselection of the unit, would it be possible (and feasible) to replace the 15 ton compressor with (say) a 5 ton compressor, block +/- 2/3rds of the coil face area, re-balance the air and just start running at 1000CFM?
thanks
Here's what we have: The AHU was originally specified to dehumidify 3500 CFM of air from 72*F/50% RH to about 42*F Saturated. The evaporator and condenser are in series in the dehumidified air stream and both are in the same air handler plenum as the unit's 15 ton scroll compressor. Refrigerant is 410A. Both coils were selected such that the face area is 3'x3', and the piping arrangement is full face with one distributor into the evaporator. There is hot gas-by pass, and with the heat of compression added into the dehumidified air, the air is supplied to our process at about 85*F/25%RH.
Due to process changes we are now limited to supplying about 1000 CFM of dehumidified air with the same target of 85*F/25%. We will do this for about a year, then the process will be permanently shut down. Instead of doing a complete reselection of the unit, would it be possible (and feasible) to replace the 15 ton compressor with (say) a 5 ton compressor, block +/- 2/3rds of the coil face area, re-balance the air and just start running at 1000CFM?
thanks





RE: Reducing Air Flow through Dehumidifier
but couldn't you just reduce the airflow (and let the compressor cycle more often)? You probably want to talk to the compressor manufacturer how it will be have with the large coil.
RE: Reducing Air Flow through Dehumidifier
I didn't understand it, do you mean 3500 cfm at(72F) leaves the evaporator at(42F) then the condenser at(85F) then to the space and back to evaporator at(72F).
RE: Reducing Air Flow through Dehumidifier
RE: Reducing Air Flow through Dehumidifier
RE: Reducing Air Flow through Dehumidifier
You might be able to recircuit the coils, taking the no longer needed tubing out of the picture.
This would also involve changing the distributor and the expansion valve.
And probably the suction line - to get the velocity back up high enough to have oil return.
And you'll need to tinker with the controls, and the compressor motor protection, and the fan motor protection, and there is probably a sail switch, differential pressure switch or current sensor that interlocks compressor operation with proof of airflow.
And you are likely to need to change the fan as well, since making such a big reduction in airflow will probably move the current one into the unstable portion of its performance curve.
And.....
How badly to you want to become a dehumidifier manufacturer?
RE: Reducing Air Flow through Dehumidifier
RE: Reducing Air Flow through Dehumidifier