Testing was conducted to evaluate the performance of a prototype OASys™ hybrid air conditioner, which modifies their indirect/direct evaporative cooling unit with an added direct expansion (DX) system for increased range of operation. A test plan was developed based on the previous testing done on a standard OASys™ air conditioner, with some adjustments to cover operation of the DX system. A test condition matrix was established to evaluate system performance over a range of environmental conditions, which would capture the cooling
design conditions for several locations in the PG&E service territory. Other tests were conducted to determine its sensitivity to supply air external resistance.
The results indicate that with the DX system off, the wet-bulb effectiveness and power consumption are about the same as for the standard model, but the supplied airflow is reduced by about 25% on average due to the added resistance of the evaporator coil. Activating the DX system produces 2 to 5°F cooler temperature air, but with an even larger reduction in airflow while more than tripling the power consumption.
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