GENERAL: An Indirect/Direct Cooler consists of two (2) separate stages. An Indirect Stage that cools without adding moisture to the air discharging it into the second stage and a second (Direct) stage which is an evaporative cooler which cools by adding moisture to the air.
PRINCIPLE: The principle behind this type cooling unit is to lower the dry bulb temperature and at the same time the wet bulb temperature. This can be accomplished by cooling through heat exchange without adding moisture (water vapor) to the air stream. By lowering the wet bulb temperature, the temperature drop across the direct stage (rigid cooling media) can be greater than the ambient outdoor wet bulb would normally allow. I.E. the achievement of cooling beyond the 100% efficient level is the goal of this type cooling.
A typical specification for performance of this type unit would be to start with ambient design conditions of 109 degree Dry Bulb and 70 degree Wet Bulb with a Wet Bulb Depression of 39 degrees Dry Bulb. A discharge temperature of 70 degrees (f) would represent 100% saturation efficiency. The specification however would be for a discharge temperature of 66.4 degrees (f) Dry Bulb or 110% (prox) saturation efficiency.
The process to accomplish this would be to discharge from the first stage (Indirect Stage) a Dry Bulb temperature of 88 degrees (f) (prox) which would also drop the Wet Bulb to 64 degrees (f). A 12" thick rigid media operating at 90% saturation efficiency would then discharge 66 .4 degrees (f). Calculation = (88Db - 64Wb = 24WBd X .9 = 21.6 temperature drop across the cooling media. 88Db - 21.6Dbtd = 66.4 degrees (f)).
PREMIER INDIRECT/DIRECT EVAPORATIVE COOLER: Formal testing of the latest design prototype is presently being conducted. Results and specifications will be published at the conclusion of these tests.
TESTING UPDATE! It has become apparent to us that it is not economically feasible to produce an Indirect/Direct type Evaporative Cooling unit that will provide performance in excess of 100% saturation efficiency. Premier has built and tested 3 separate design configurations of this type unit and has decided to discontinue research and development efforts.