EVAPCO AXS Advanced Crossflow Induced Draft Cooling Tower

Large crossflow cooling towers designed around easy maintenance

The EVAPCO AXS, short for Advanced Crossflow Series, is a factory assembled induced draft cooling tower with axial fans and a crossflow fill arrangement. Hot water enters the open, gravity fed hot water basins at the top, flows through large orifice nozzles over the fill and falls to the cold water basin. Air is drawn in horizontally through the louvers on the ends of the tower, crosses the falling water in the fill and is discharged upward by the fans. EVAPCO lists the series from 312 to 1,405 nominal tons per its product page, which places it in the large central plant, process and power duty range.

The tower is a cell-based design: each cell is a self-contained box with its own fan, so larger heat loads are met by combining cells and turning fans on or off, or slowing them with a variable frequency drive, as the load changes. EVAPCO also offers an optional velocity recovery stack for additional capacity and a stainless steel basin or upper section for harsher water or air conditions.

Technical specifications

Model range and engineering data

Model numbers combine the cell width in feet, a box length in feet and a letter that sets the motor size: AXS 12-13I22 is a 12 foot series, 13 foot long box with the I motor option (10 hp). The printed tables give nominal tons, the ASHRAE 90.1 efficiency in gpm per hp, motor hp, air flow, and shipping, heaviest section and operating weights. The 13, 17 and 20 foot long boxes also list a heaviest section weight. Selected rows:

The note on each drawing states that an adequately sized bleed line must be installed, that catalog drawings and weights are not certified prints, and that adequate spacing for access must be allowed as set out in the EVAPCO equipment layout manual. One drawing note states that the fan guard does not ship factory mounted.

Construction, maintenance and options

The modular hot water basins carry integral weir dams to accommodate at least 50 percent of design flow and can be serviced while the tower runs, and the two-pass PVC inlet louvers are integral with the fill to limit splash-out during fan cycling. The cold water basin and the upper section, including mechanical equipment support, fan cowl and guard, are available in Type 304 or 316 stainless steel with welded seams. Galvanized units need initial passivation, and the specification advises contacting the site water treatment vendor several weeks before water is added.

Maintenance options listed by EVAPCO include an external service platform, a basin level platform, a sloped ladder and a motor davit. Water treatment options are the Smart Shield solid chemical feeder and the chemical-free Pulse-Pure system, and HCAI special seismic certification preapproval is mentioned for the series.

Using the AXS in Oman and the GCC

Large crossflow towers are used in the region in district cooling plants, power and desalination plants, refineries, petrochemical plants and large commercial developments, where high cooling capacity and easy access to fill and basins are important. The selection must be made at the project’s design wet-bulb temperature, which can be high in coastal summer conditions, and multi-cell installations should consider recirculation of warm exhaust air between cells and from nearby buildings, which raises the effective inlet wet bulb.

Make-up water in the region may be desalinated water, seawater-influenced groundwater or treated sewage effluent, which is increasingly used in district cooling. Each source needs a suitable water treatment programme, blowdown control and regular monitoring, together with a Legionella control plan. Dust and sand enter crossflow towers through the air inlets, so plan regular cleaning of the hot water basins, nozzles and cold water basin, and consider side-stream filtration. Check materials of construction against the water chemistry, and leave access space around the tower for maintenance and fill replacement.

Information to send with an enquiry

• Heat load, flow rate and inlet and outlet water temperatures
• Design wet-bulb temperature and site layout
• Make-up water source and quality
• Number of cells, sound limits and quantity

Documents and quotation

The engineering data attached here lists all printed AXS models with weights and connection drawings. Seven Star LLC is an independent supplier in Muscat; to quote this tower we need the circulating water flow, entering and leaving water temperature, design wet bulb, cell arrangement and any sound or height limit. More options are under cooling equipment.