eco-ATWB Closed Circuit Cooler
Induced draft axial fan counterflow closed circuit cooler. The eco-ATWB cooler is used for cooling of water or water/glycol mixtures. The process fluid remains without oxygen and impurities. Executed as per standard with Z-725 (725 g/m² zinc) galvanized steel panels.
The new eco-ATWB (Advanced Technology) design dramatically increases the efficiency in both the evaporative and dry cooling modes of operation thereby saving water and energy.
The eco-ATWB utilises EVAPCO's new patent pending Ellipti-fin coils which are the Most Efficient Closed Circuit Cooler Coil in the HVAC industry! The Ellipti-fin features elliptical spiral fin technology to maximize the surface area available for heat transfer. The elliptical tube design allows for closer tube spacing, resulting in greater surface area per plan area than round-tube coil designs. In addition, the revolutionary Ellipti-fin design utilises spiral fin technology and has lower resistance to airflow than typical finned coil designs. The coils are manufactured from high quality steel tubing following the most stringent quality control procedures. The assembled coil is pneumatically tested under water in accordance with the European Pressure Equipment Directive (PED) 97/23/EC.
The ATWB cooler range is CTI certified in the USA and is complient with the International Building Code (IBC). Evapco Europe provides with each closed circuit cooler a Thermal Performance Guarantee. eco-ATWB-units are constructed for a maximum nominal capacity of 11 MW.
Long-lasting corrosion protection is guaranteed with Z-725 heavy gauge mill hot-dip galvanized steel (Z-725 = 725 g/m² zinc). The galvanized steel construction withstands the most difficult environmental and operating conditions.
For special applications, Evapco can produce the units with stainless steel sump, with a water touched stainless steel construction or a complete stainless steel construction (AISI 304 or 316 are possible).
- Unit: Closed circuit cooler
- Models: 704 Models (eco-ATW 3-2C3-Z till ATW 24-6P40)
- Width: 927 / 1.232 / 2.283 / 2.388 / 2.991 / 3.607 / 4.906 / 6.112 / 7.344 mm
- Design: Induced draft
- Capacity: 42 till 10.813 kW
- Air Flow: 2,0 till 289,8 m³/s
- Fan: Axial
- Drive: Powerband-belt driven
- Reduced water consumption
- High dry bulb switchover
- Lower energy costs
- Smaller plan area
The eco-ATW features the new EVAPCO Ellipti-fin coil, which utilizes elliptical spiral fin coil technology. This technology allows for a significant increase in thermal performance with up to a 40% lower operating horsepower (kW) than a typical evaporative cooler! This will result in tremendous energy savings throughout the year.
If minimizing the footprint of the unit is of greater concern, the increased thermal capacity of the Ellipti-fin technology will allow a selection that yields up to a 40% smaller plan area!
Additionally, the Ellipti-fin coil technology enables the eco-ATW to be operated in a 100% Dry Mode, whereby the switchover temperature is significantly higher than that of a typical bare tube coil. This leads to a significant increase in dry operating hours, thus increasing your water savings. This combination of features allows the eco-ATW to be operated with both energy and water efficiency in mind, making it the ideal choice for many installations.
Consider an industrial application in Munich (Germany), where the unit is required to reject a constant heat load of 740 kW with 30 l/s of water entering at a temperature of 32 °C and a leaving temperature of 26 °C. The process operates 24 hours a day 7 days a week. The eco-ATW is compared to:
• ESWA 96-33J-2 – an evaporative cooler without dry cooling capability
• ATW 120-3L-2 – an induced draft counter-flow cooler capable of some dry operation
Generally the eco-coolers require lower total installed kW than ATW and ESWA with consequent energy savings.
With the increased dry cooling efficiency of the eco-ATW and the use of the Sage2® Water and Energy Conservation Control System, the eco-ATW is able to operate dry for more than 25 % of the year:
Due to the Dry Operation capabilities of the eco-ATW, the water consumption is extremely lower than ATW and ESWA coolers as illustrated below:
with reduced costs associated with water usage. In this case for example, during winter eco-ATW doesn't request any water consumption.
Dry Mode (Sensible Heat Transfer)
In the dry mode, the recirculating spray pump is turned off (Fan on, Pump off). The process fluid enters the eco-ATW cooler through the top coil connection and circulates through the coil with the Fan On. Heat from the process fluid is dissipated to the atmosphere by sensible heat transfer through the tube wall and fins to the air passing over the coils. The coils are finned to promote optimal airflow over the coil and to maximize heat transfer area. Air is drawn over the finned coil by the fan drive system. The process fluid is then returned to the heat source via the bottom coil connection. This mode of operation eliminates water consumption when the dry bulb temperature is favorable.
Evaporative Mode (Latent Heat Transfer)
In the evaporative mode, the process fluid enters the cooler through the top coil connection and circulates through the finned coils. With the pump turned on, the heat from the process fluid is transferred through the tube wall and fins to the water cascading downward over the coils while simultaneously air is drawn upward over the coil opposite the water flow using the fan drive system (Fan on, Pump on). A small portion of the water is evaporated to dissipate the heat to the atmosphere in a latent heat transfer. This mode of operation provides fan energy savings and lower leaving water temperatures by utilizing evaporative cooling.
1. Casing and basin design
High Performance drift eliminators
The drift eliminators remove entrained water droplets from the air stream to limit the drift rate to less than 0.001% of the recirculating water rate. The unit can be located in areas where minimum water carryover is critical. The drift eliminators are constructed of an inert polyvinyl chloride (PVC) plastic material which effectively eliminates corrosion of these vital components. They are assembled in sections to facilitate easy removal for inspection of the water distribution system.
Water Sight Tight air inlet louver (WST)
The air inlet louvers are both water and sight tight to ensure that the water stays in and sunlight stays out of the cold water basin. The water tight design maximizes thermal performance while minimizing water loss. The sight tight design also inhibits algae growth more effectively than previous designs.
Z-725 Galvanized steel panels
EVAPCO has developed the ultimate system for corrosion protection in galvanized steel construction - the EVAPCOAT Corrosion Protection System. Z-725 is the heaviest level of galvanizing available for manufacturing evaporative condensers and has a minimum of 250 % more zinc protection than competitive designs using Z-275 steel.
2. Heat transfer system
Ellipti-fin evaporative coil
The new eco-ATW Closed Circuit Cooler utilizes Evapco's patent pending Ellipti-fin coil design which assures even greater operating efficiency. The elliptical tube design allows for closer tube spacing, resulting in greater surface area per plan area than round-tube coil designs. In addition, the revolutionary Ellipti-fin design utilizes elliptical spiral fin coil technology and has lower resistance to airflow than typical finned coil designs. This permits greater water loading, making the new Ellipti-fin coil the most effective design available. The coils are manufactured from high quality steel tubing following the most stringent quality control procedures. Each circuit is inspected to ensure the material quality and then tested before being assembled into a coil and encased in a steel framework. Finally, the assembled coil is pneumatically tested in accordance with the "Pressure Equipment Directive" - PED 97/23 EC. After fabrication, to protect the coil against corrosion, the entire assembly is hot-dip galvanized.
3. Mechanical design
Power-Band Drive System
The eco-ATW Closed Circuit Cooler features the highly successful, easy maintenance, heavy duty Power Band Drive System. It consists of Standard heavy-duty pillow block bearings with a minimum L10 life of 75,000 hours, extended lube lines, external motor/belt adjustment, aluminum alloy sheaves, solid-back multi-groove Power- Band belts and totally enclosed motors.
Single speed fan motor
Each Evapco unit is equipped as per standard with a heavy duty, single speed IP55 TEFC / TEAO electrical motor.
Standard axial fan
The standard fans are heavy duty statically balanced axial propeller type. The fans are constructed of extruded aluminum alloy blades, installed in a closely fitted cowl with venturi air inlet for maximum fan efficiency. Each fan blade is individually adjustable. The fan cowl is covered with a heavy gauge hot dip galvanized wire fan guard.
4. Water distribution
The spray pump is optimized for high waterflow at relative low pressure. The motor is totally enclosed and protected with an end-cap to ensure a long trouble free operation.
Spray-water distribution system
The water distribution system is enclosed and completely protected by the casing panels and drift eliminators. The water distribution system is made with non-corrosive materials including schedule 40 PVC pipe and durable ABS plastic nozzles. The spray branch piping is easily removed and designed with threaded end-caps for easy cleaning. Evapco’s design avoids the problems of biological growth and clogging.
ZM II ™ Zero-Maintenance spray nozzles
Even and constant water distribution is paramount for reliable, scale-free evaporative cooling. EVAPCO's Zero Maintenance ZM II™ Spray Nozzle, mounted in a PVC distribution pipe with end-caps remains clof-free under the toughest conditions to deliver approwimately 4 l/s tovery square meter of coil paln area. The heavy-duty nylon ZM II™ Spray Nozzles have a 33 mm diameter opening and a 38 mm splash plate clearance, enabling EVAPCO to use 75 % fewer nozzles.
5. Maintenance and inspection
Large access door
A large hinged access door is located on the side of the unit for easy access to the fan drive system. The belt can be adjusted by tightening the tensioning-bolts on the motor base and the tension can be checked easily through the access door, all while standing at the side of the unit. The bearings can also be lubricated from the side of the unit. The bearing lubrication lines have been extended to the exterior casing and are located by the access door.
6. Operational control
Mechanical water level control
Simple but reliable water level control system with adjustable mechanical float and brass float-valve.