© 2007 Building Energy Partnership
LOW ENERGY ADIABATIC COOLING
This form of ventilation unit was proposed for a 400 seat auditorium. In addition to providing fresh air ventilation efficiently and according to occupancy levels, the unit was equipped with a high performance heat exchanger and high efficiency fans and consequently fully able to maximise the use of fresh air for free cooling for much of the year when ambient conditions were appropriate.
In summer months, the adiabatic cooling effect generated by simply spraying water into the leaving exhaust air is capable of removing some 10ºK from the ambient air. Any remaining cooling capacity was supplied by circulating water through the ground loop system of installed ground source heat pump (GSHP).
In summer months, the adiabatic cooling effect generated by simply spraying water into the leaving exhaust air is capable of removing some 10ºK from the ambient air. Any remaining cooling capacity was supplied by circulating water through the ground loop system of installed ground source heat pump (GSHP).
The fresh air temperature supplied to the room is reduced by indirect adiabatic cooling. Water evaporates inside the ventilation unit to provide the cooling effect. The humidity of the building is not increased as the water is sprayed into the warm dry return air. The cooling effect is transferred through the double plate heat exchanger lowering the temperature of the fresh air stream. This technology can provide comfortable conditions without the need for refrigerant compressors or refrigerants.
In winter months, the auditorium is held at a background temperature in the region of 18ºC using the GSHP system and under floor heating. Prior to occupancy, the air handling unit can be operated to rapidly bring the auditorium up to 21ºC using stratified heat from high level; any residual requirement for heat could be met from the GSHP 35ºC water supply. The auditorium in use will require cooling to offset the heat gain from the occupants and lighting, and this cooling will be “free” by increasing the fresh air rate to meet the prevailing demand for cooling. The adiabatic system will be called in only when the free cooling source of outdoor air iis fully exploited.
In summer months, the air handling unit automatically expels any excess stratified heat prior to occupancy. Adiabatic cooling is brought in as required which satisfies the majority of summer usage. To meet peak summer use of the auditorium, additional supplementary cooling is brought in from the ground loop system. This has the spin off of returning heat to the ground and in part making up the winter depletion of heat.
This system is increasingly used in many school and university auditoria where high system efficiencies with resulting low running costs are preferred over the alternatives of high operating cost refrigeration based cooling systems.
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