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Hastings Industries Inc.
Vari-Cool Evaporative
Vari-Cool Evaporative - Page 2
Vari-Cool Evaporative
| The uses of the cooled dry-side airThe major use of the
cooled, dry- side air is to pre- cool entering air to reduce the load on air conditioning
system coils. Cooled, dry-side air may also be used as an exclusive cooling source in
applications where design conditions permit. Two-stage cooling applies dry-cooled air to a
second stage direct evaporative cooler. The two-stage I/D" (Indirect/Direct) unit is
used as the total cooling source in many systems applications.
Wet-side air source Normally outside ambient air is used as the secondary wet-side air source. In cases where sufficient exhaust air is available to handle the secondary air requirements (nominally 800 CFM per core), the pre-conditioned air will provide a lower wet-bulb temperature, thus increasing the capacity of the VARI-COOL unit for cooling; also, this application will allow wintertime heat reclaim operation. Never apply exhaust air at temperatures above 125°F.The use of the cooled wet-side air The wet-side(secondary) air is cooled as it passes over the tubes. The air may be directed, and used as the entering air, to air conditioning system air-cooled condensers. This will create further energy reduction (attributable to the VARI-COOL equipment) and increased capacity of the air conditioning system. The dry bulb temperature reduction of the secondary air can be expressed as approach to wet-bulb temperature. The VARICOOL unit, based on nominal8OO CFM per core of secondary air will achieve an approximate 1O°F W.B. approach. Heat Reclaim When the VARI-COOL unit is applied to pre-cool outdoor air in the cooling season and building exhaust air is provided as the wet side air source, an additional energy-saving by-product is obtained in the heating season: the outdoor air is pre-heated by reclaiming the heat of the exhausted building air. Heat reclaim is accomplished when the cooling thermostat de energizes the circulating pump and the knitted tube sleeves dry out, creating a sensible heat exchange. Automatic control can be provided to energize and de-energize the water pump based on the entering air temperature to the dry-side air passage.Heat reclaim, based on equal air quantities (primary air through the tubes and secondary air across the tubes), is approximately 40% of the temperature difference between entering primary air and entering secondary air. Example: Entering Exhaust Air = 80°Entering Outdoor Air = 35° Temperature Difference = 45° At 40% efficiency, the temperature rise to the entering outdoor air is 45°x4O%= 18° rise or a leaving temperature of 53°F. Do not apply exhaust air temperatures above 125°F. To avoid frost accumulation, do not provide outdoor air temperatures to the unit below 3O°F. Tempered (pre-heated or bypass) air may be provided at temperatures below 30°F. Do not apply exhaust air above 1000 CFM per core to avoid water carry over.
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