Evaporative cooling is a mechanism traditionally used to provide thermal comfort in hot and dry regions. The mechanism involves sensible and latent cooling of air with water. Direct evaporative cooling is most effective when the outside condition is dry and below the desired conditions. Indirect evaporative system is used during the seasons when little or no humidification is required i.e. when outside air humidity is within a comfortable range. Fresh filtered air is made to pass through a dry section of the system to cool the air through sensible heat transfer. Stage wise evaporative cooling systems can be either two stage or three stage.
The drawback of the two stage system is the high humidity level of the supply air. Over a period of time indirect evaporative cooling systems which provide sensible cooling of the air without humidification have emerged in the market.
|Can be added to existing chilled water systems at low costs||Needs high purity water to prevent the build-up of salts|
|Reduces use of HFC refrigerants||Requires periodic maintenance|
|Reduces energy costs significantly|
|Case study||Central University of Rajasthan|
|Location||Bandar Sindri, Ajmer, Rajasthan, India|
|Climate Type||Hot and dry|
|System Description||Two stage evaporative cooling
System consists of a direct evaporative pre cooler which provides cool and wet air to indirectly cool down the primary air in the tube bundle heat exchanger. The cool and dry air is then passed through a direct evaporative cooler to humidify it.
|System Performance||Energy consumption in the hostel building is estimated to have been reduced to 1/3rd of a similar building with no major energy conservation measures and using conventional air-conditioning systems. Indoor temperatures were measured to be between 31 °C to 34 °C when the ambient was approximately 44 °C.
Energy Performance Index was measured to be 60 – 65 kWh/m2/year (2012)