Closed Circuit Coolers

eco-ATWB-E Closed Circuit Cooler

eco-ATWB-E Closed Circuit Cooler

Induced draft axial fan counterflow closed circuit cooler. The eco-ATWB-E 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-E line of Closed Circuit Coolers offers the same great design benefits and features as the eco-ATW, an increase in the efficiency of both evaporative and dry cooling modes, but it has also been specifically designed to optimize both the evaporative (latent) and dry (sensible) modes of cooling simultaneously. This unique design joins an evaporative cooler and a dry cooler into one unit.

The eco-ATWB-E 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 eco-ATWB-E 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-ATW-units are constructed for a maximum nominal capacity of 2,6 MW.

Long-lasting corrosion protection is guaranteed with Z-725 heavy gauge mill hot-dipp 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).

Technical Data 

  • Unit:    Closed circuit cooler
  • Models:    228 Models (eco-ATWB-E 9-3G8 till eco-ATWB-E 12-6P20)
  • Width:    2.283 / 2.388 / 2.991 / 3.607 mm
  • Design:    Induced draft
  • Capacity:    377 till 2.636 kW
  • Air Flow:    13,3 till 72,4 m³/s
  • Fan:    Axial
  • Drive:    Powerband-belt driven


  • Reduced water consumption
  • High dry bulb switchover
  • Lower energy costs
  • Smaller plan area

The eco-ATWB-E maintains all of the advantages of the eco-atw with the additional benefit of enabling simultaneous wet and dry operation. The unique Water Efficient Mode of the eco-ATWB-E allows for a portion of the heat load to be rejected through both evaporative cooling AND dry cooling, even at high ambient temperatures, this further increases your ability to save water and offers additional associated cost savings through reduced water make-up, blow-down and chemical consumption. The eco-ATWB-E provides an ideal solution for applications where minimizing both energy and water consumption is critical.

Depending on the optimum eco-Cooler you select for your job, one can operate 100 % wet, 100 % dry or simultaneously Wet & Dry in the  Water Efficient Mode, offering unique advantages in freezing climates, higher temperature industrial cooling applications where 100 % evaporative cooling is not always favorable.

Consider a Data Center cooling application for 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-ATWB-E is compared to:

• ESWA 96-33J-2 – an evaporative cooler without dry cooling capability
• ATW 120-4K-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-ATWB-E and the use of the Sage3® Water and Energy Conservation Control System, the eco-ATWB-E is able to operate dry for more than 80 % of the year:







Reduced costs associated with water usage.

Dry Mode
(Sensible Heat Transfer)

In the dry mode, the recirculating spray pumps are turned off (Fan on, Pump A & B off). The process fluid enters the eco-ATWB-E 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 walls 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 coils 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.


Water Efficient Mode
(Evaporative and Sensible Heat Transfer)

The joint wet and dry operation mode provides water savings as well as low approach temperatures. In this joint mode of operation, the fan is on and the process fluid enters the coils through the top coil connections (Fan on, Pump A on, Pump B off). Recirculating pump B is turned off and coil B rejects a portion of the heat load to the atmosphere through the tube and fin walls to the air passing over the coils using sensible heat transfer. Pump A is left on where heat from the process fluid is transferred through the coil tubes to the water cascading downward over coil A. This mode of operation minimizes the amount of water used while maintaining the cooling capacity required. The cooled fluid then returns to the process via the bottom coil connection.


Evaporative Mode
(Latent Heat Transfer)

In the evaporative mode, the process fluid enters the cooler through the top coil connections and circulates through the finned coils. With both pumps on, theheat from the process fluid is transferred through the coil tubes 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 A & B 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 AT Cooling Tower 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

Spray pump

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.