EVAPCO PHW Parallel Hybrid Closed Circuit Cooler

Large closed circuit cooler cells for industrial plants and data centers

The EVAPCO PHW is a Parallel Hybrid closed circuit cooler: a mechanical induced draft, crossflow unit in which the process fluid is kept inside a sealed coil while spray water and air carry the heat away. It combines a spray-wetted coil with a crossflow PVC fill below it. Hot fluid enters the coil at the bottom connections, basin water is pumped over the coil, and air is drawn in parallel flow with the water through the coil; the water then falls through the fill, where more air removes additional heat by evaporation, before returning to the basin.

EVAPCO builds the series around its largest single cells, a 12 ft by 24 ft and a 14 ft by 26 ft unit, for projects that need the fewest units, connections and fans. The EVAPCO product page names industrial plants, data centers and large HVAC applications as the target uses, and states that the PHW offers CTI certified performance and is supplied with a written thermal performance guarantee.

Technical specifications

Model range and engineering data

The printed tables list each model by fan motor letter, from M to Q on the 12 ft cell and M to R on the 14 ft cell, with a number from 5 to 10 before the letter. The data below includes fan hp as printed, air flow, weights, coil volume, spray pump and remote sump data. Selected rows:

Every printed model lists a (2) 7.5 hp spray pump delivering 1,800 gpm and a 14 in remote sump connection. Notes state that series flow piping is marked with a Z suffix, stainless coils with a C suffix and low sound fans with an R suffix, that heaviest section is the upper section, and that unit dimensions may vary slightly from catalog drawings.

Use, access and winter protection

EVAPCO notes that closed circuit coolers should only be used on sealed, pressurized systems, because continual aeration of the water in an open system can cause corrosion inside the coil tubes. The internal walkway is standard on the double air inlet units, a large access door and pump house access are standard, and optional features include an elevated internal service platform, an internal motor davit, an external service platform with ladder and a Sun-Blocker system against algae.

Electric basin heater packages with thermostat and low water cutoff are listed for the two cell sizes, for example two 12 kW heaters at 0 F for the 12 x 24 ft cell and two 15 kW heaters for the 14 x 26 ft cell, and external pumps should be heat traced and insulated. Support is on structural I-beams under the outer flanges, levelled within 1/8 in in 6 ft, without shimming between the unit and the beams. An electric water level control can replace the mechanical make-up valve.

Using the PHW in Oman and the GCC

Large closed circuit coolers are used in the region in data centres, power generation, industrial process cooling, compressor stations and water-cooled heat pump systems, where the process fluid must stay clean and free of dust and sand. Keeping the fluid inside the coil avoids fouling of heat exchangers and process equipment, which is a common problem with open towers in dusty locations. The cooler must be selected 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.

The spray water outside the coil needs a water treatment programme, blowdown control and a Legionella control plan, because scale on the coil and fill reduces capacity. Make-up water in the region may be desalinated water, groundwater or treated effluent, and the treatment programme should be designed for the actual source. Plan regular cleaning of the basin, strainers, nozzles and fill, and leave access space around the unit for maintenance. Check the structural support for the operating weight, including the coil fluid and spray water.

Information to send with an enquiry

• Process fluid, flow rate and 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 attached brochure includes the full PHW engineering tables and the optional equipment pages. Seven Star LLC is an independent supplier in Muscat; to quote a closed circuit cooler send the fluid, flow rate, entering and leaving temperature, allowable pressure drop and design wet bulb. See also cooling equipment.