For a chilled-water coil, the primary air temperature leaving the coil typically ranges from 45[degrees]F to 48[degrees]F (7.2[degrees]C to 8.9[degrees]C) while the primary air temperature from a DX coil
is about 55[degrees]F(12.8[degrees]C).
The outside air, OA from the zone is passed through the DX coil
of the DOAS system to get conditioned outside air, OA'.
It can be seen that in Miami, [T.sub.w] takes the same value as the standard rating condition at 30[degrees]C (86[degrees]F) for the WSHP in most operating hours, while [T.sub.oa] is lower than the standard rating condition at 35[degrees]C (95[degrees]F) for both the ASHP and DX coil
. In Fairbanks, however, [T.sub.w] is higher than the standard rating condition at 20[degrees]C (68[degrees]F) for the WSHP in most operating hours, while [T.sub.oa] fluctuates around the standard rating condition at 8.3[degrees]C (47[degrees]F) for the ASHP.
The BAS collects measurement data of nearly all components, including the required measurements for this study such as the ambient conditions, temperature and humidity ratio entering and leaving the DX coil
, airflow rates, damper positions, and compressor power.
The actual DX coil
furnished for the system was 8 row, 10 fpi, with a face velocity of 440 fpm (2.24 m/s), so it is very near the pressure drop of the coil required for the chilled-water system:
When the temperature drop of about 20[degrees]F(11[degrees]C) across the dX coil
results in a discharge temperature below the comfort setpoint of 53[degrees]F(12[degrees]C), the economizer controller will reduce the economizer airflow to keep the discharge air temperature from getting too low.
For a zero-superheat dry DX coil
, there is only sensible cooling, and the local heat transfer rate is thus given by
* DX coil
with the DOAS AHU for achieving dehumidification:
A part of the return air mixes with the outside air from the DOAS and is cooled by the heat pump DX coil
, while the rest of the return air leaves the building by passing through the enthalpy wheel located in the rooftop DOAS unit.
Training RMSE (%) of Each Component Component Circuit A Circuit B Compressor 5.1 1.8 Condenser 9 TEV 14.5 14.5 DX coil
5.8 Supply fan 4.2 Table 4.
The indoor coil model is an extension of the DX coil
model that exists in EnergyPlus (Raustad 2013).