Desiccant Wheel

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I'm trying to model a Munters packaged desiccant unit (diagram above)
that uses a heat pump to operate both sides of the wheel (heating side
for the desiccant recharge and cooling side for pre-cool). Is it
possible to model this in eQUEST? If so - how?

Vikram Sami, LEED AP

Vikram Sami's picture
Joined: 2011-09-30
Reputation: 0

For energy audits and calibrating energy models to actual utility data,
the actual climate data for the year is needed (instead of the usual
TMY2 file). Has anyone found a good source for these year-specific
climate files?



Katie Tuttle's picture
Joined: 2011-09-30
Reputation: 0

You can obtain hourly weather data from NOAA. There's a set from 1961-1990 (SAMSON) and a set from 1990-1995 (HUSWO).

In addition, you can purchase from NOAA hourly data for specific weather stations for the years not included in the data sets above. Don't know of any free info.


Yalin Uluaydin

Yalin Uluaydin's picture
Joined: 2011-09-30
Reputation: 0

Dear all:

I have a problem about setting of the thermal distribution losses in
For Step 2, both the Baseline building and the proposed building should
take the thermal losses into consideration. If project which can't
obtain the actual performance dada, we can use the Default seasonal
performance values for DES heating plant efficiency (70% for total
boiler plant) , DES cooling plant efficiency (COP of 4.4 for total
cooling plant efficiency )and thermal distribution losses.
As to DES heating plant and DES cooling plant efficiency, I think it is
just enter in the "Equipment Efficiency" to represent the comprehensive
But How can we set the distribution losses? Does anyone know this and
kind share with me?

Best regards!
Eleanor Shen

Shen, Jie                 CAR's picture
Joined: 2011-09-30
Reputation: 0

Hello Vikram,

This is how we modeled gas-fired desiccant units serving multiple AHUs in a
storage building with very tight conditioning tolerances.

1. If you have a fresh air (FA) section to pre-cool the air, make a
single-zone AHU that is controlled to maintain the discharge temperatures
you want. Note that the DAT has a lower limit of around 40?F or so. Set
the design airflow rate to be whatever you need for ventilation air, force
the unit to be 100% OA.
2. Create a ?FA ghost zone?, and make the space temperature setpoints
be the desired FA discharge setpoints. Don?t put any lights, people, etc in
the space.
3. Make a second single zone AHU that will be your desiccant section,
for now let?s call it DD system. You need to set up the ?outside air from
system? as the FA system, set the ventilation airflow rate as what you need
to pass through the DD.
4. Create a ?DD ghost zone? that has temperature setpoints typical of
the discharge temperature from your desiccant section.
5. Create the AHUs that are actually in the design, include their
heating and cooling coils and any humidification equipment ? this is
straightforward. Outside air needs to come from the DD system.

This approach can accurately predict gas use for regeneration, cooling for
the FA and AHU units, and heating in the FA and AHU units when the DD
section is turned off. The tricky thing about this approach is that you
need to select the DD discharge temperature to be representative of the
typical operating point during the dehumidification season since DD
discharge temp varies with the degree of dehumidification. An alternate
approach (which we have not tried) would be to make 365 day schedules based
upon your weather file and use a user-defined function to calculate the DD
ghost zone space temp setpoints based on the humidity entering the DD unit.
This function would need to be based on detailed information from Munters.
Wouldn?t it be great if you could make user defined functions that directly
relate to hourly information in the weather file?


Eric Studer's picture
Joined: 2011-09-30
Reputation: 200