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IDEC is two stage process which includes Indirect and Direct evaporation of water to cool supply air stream. . The first stage is Indirect Cooling stage where hot ambient air passes through sensible air to air cross flow heat exchanger where the sensible heat is removed. Heat exchanger is made up of engineered polymer having anti fungal, anti bacterial inert coating on wet side to improve the heat transfer through adjacent surfaces. Construction of heat exchanger is like a mesh of horizontal and vertical channels. In which ambient air enters from bottom and water is poured from top of vertical channel which forms uniform thin water film at inner surface and air is cooled by adiabatic evaporation in vertical channel. At the same time another air stream passes through the horizontal channel which is cooled by thermal conduction between air stream of horizontal and vertical channel. As water is not in direct contact with the horizontal air stream, the supply air is cooled by sensible cooling only without adding any moisture. Second stage is direct evaporation in which cellulose pads are used .when the cellulose pad get wetted, due to high surface area of heat transfer and uniform distribution of wet surface along the air stream evaporation efficiency is increased. In this stage cooling takes place through adiabatic evaporation and results in moisture addition in air stream. This air is now ready to pick up heat load from area to be cooled.
• Energy Efficient: Significant energy saving when compare to conventional HVAC
• Lowest Connected Loads: Less than 30 % energy usage as only fans and low wattage pumps required.
• Water saving: Use 30 % less water to provide require cooling with conventional evaporating cooling
• Competitive life cycle cost:Lower operational cost, decrease power back up sizing and minimal maintenance cost lead to real long term saving at little additional cost.
|Parameter||Units||TWO Stage IDEC||Evaporative Cooling System|
|Summer dry bulb||Dec C||38||38|
|Summer wet bulb||Dec C||20.5||20.5|
|Sensible heat load||TR||25||25|
|Supply air temp.||Dec C||19||23|
|Space temp.||Dec C||28||28|
|Installed Cost||INR lacs||6.8||5|
|Operating Cost||INR lacs||2.88||6.4|
In conventional TFA only cooling coil is used but in pre-cooled TFA consist of two stages , first is indirect evaporation in which ambient air is sensibly cooled by air to air heat exchanger and then in second stage precooled air is passed through cooling coil to obtain the required air conditions. Due to precooling of air the heat load of coil is reduced through the reduction in Δ T on air side. Measurable energy and cost saving through overall HVAC circuit by reduction in required capacity of cooling coil and other components like condensing unit, piping and valve etc. The other advantage of TFA is, it offers unique heat recovery opportunity between incoming ambient air and building exhaust air without any cross contamination. Air to air heat exchanger can intake even toilet exhaust for heat recovery which is not possible with traditional heat recovery wheels.