Dehumdification Software Recommendation
Dehumdification Software Recommendation
(OP)
I normally use HAP for my loads but it will not work in this case. I have a space that has a heating load, minimum ventilation load and substantial internal moisture production. I would like to heat the space with direct fired MAU with a minimum 40% outside air. I need to size the MAU fan cfm as a function of heating load AND indoor space RH\DP. Space will only be used when OA is less than 50F. Building is located in Midwest. Thus this is a dehumidification process w/o a cooling or desiccant wheel. I have completed the heating loads / MAU sizing based upon IAT&OAT + minimum OA flow but have the issue of using OA to lower space gr/ft3 in a direct fired application.





RE: Dehumdification Software Recommendation
The 60% that is recirculated will of course not remove the moisture created from the space.
Based on required inside Absolute Humidity and worst case OA Absolute Humidity you can calculate what volume of outside air is needed. If this is less than the 40%, then you are in luck. If it's more, the control system has to vary the OA % based on humidity.
I guess al you need is a Carrier/Mollier diagram and the appropriate climate data for the location.
RE: Dehumdification Software Recommendation
RE: Dehumdification Software Recommendation
IMHO direct-fired is only appropriate where you ventilate a dirty space, like a garage, shop or welding area etc. As mentioned above, combustion also produces water.... so it is questionable how you dehumidify with direct-fired units.
RE: Dehumdification Software Recommendation
RE: Dehumdification Software Recommendation
Overall your approach sounds correct. I still don't think recirculating in a direct-fired unit is good. Especially in your case you want to remove moisture with OA, so reducing OA seems counter intuitive. If you want to make up some additional building load, you could install a separate recirculating indirect-fired unit.
I once reviewed a design where the "designer" proposed to recirculate 100% of air in a direct-fired unit. They were a bit bitter when i made them change that... but I figured the unit will flame out after some run time for lack of oxygen, long after it had killed all humans.
RE: Dehumdification Software Recommendation
ROBATHERM have AHU's that fire gas or oil, but NOT in the airstream.
And it might be energetically more efficient to make heating/ventilation and moisture removal two separate processes.
RE: Dehumdification Software Recommendation
I have seen them used in a similar application where there was a large % of OA air and a requirement for latent cooling (de-hum) and not much sensible cooling. It was in a bar / club where they were using 100% OA to improve comfort level and allow patrons to smoke in certain areas of the bar. It worked a treat.
As a bonus it was very energy efficient.