EVAPCO PMRC Forced Draft Axial Fan Evaporative Condenser

Single-stage axial fans at ground level for easier condenser service

The EVAPCO PMRC is a forced draft evaporative condenser that places single-stage axial fans at the base of the unit. Refrigerant gas from the compressors enters the condenser coil, water from the sump is pumped over the tubes, and the fans force air upward through the coil against the falling water. A small part of the water evaporates, which removes the heat of condensation, and the saturated air leaves through the drift eliminators at the top. The cooled water falls back to the sump and is recirculated.

EVAPCO redesigned the line around ground-level fans with individual fan drives, so drive components, motors and grease points are reached from the front of the unit and each fan can be cycled independently for capacity control. EVAPCO states the vane-axial fan arrangement can reduce energy use by up to 50 percent compared with traditional centrifugal fan condensers, and quotes a range of 124 to 1,516 ammonia tons for the line.

Technical specifications

Model range and engineering data

Selection follows the heat of rejection method: the total heat load is multiplied by a capacity factor for condensing pressure and wet bulb from the bulletin tables, with separate factors for R-717 suction temperature, and a unit is chosen from the MBH tables. The engineering tables then give fan hp and air flow, weights, refrigerant charge, coil volume, spray pump data, remote sump gallons and heights. Selected printed rows:

The notes state that dimensions are subject to change and are not for prefabrication, that tons are at the standard conditions above, and that water gallons shown are in suspension in the unit and piping, with allowance needed in a remote sump for pump suction.

Field assembly, maintenance and variable speed use

The field seam is designed with self-guiding channels and, according to EVAPCO, eliminates up to 85 percent of the fasteners typically used to join condenser sections, reducing contractor labor and the risk of seam leaks. Panels use butyl tape with an integral gasket, secondary caulking and double-brake flanges. All fan sheaves are on the front of the fan section and motors sit on a platform base for easy belt tension adjustment, with bearing grease fittings extended outside the unit. A man-sized access door allows easy motor replacement.

Inverter duty motors are standard, but the bulletin cautions that variable frequency drive control by others may need motor shaft grounding brushes, AC load reactors, low pass filters or tuned trap filters. An internal baffle system extends from the pan bottom through the coil bundle so individual fans can be cycled without air bypass inside the unit. Optional features include an external service platform, a basin access package and stainless steel construction. Water treatment options are the Pulse-Pure and Smart Shield systems.

Before ordering, compare the printed data with the heat rejection duty, refrigerant, condensing temperature and design wet bulb of the plant, and confirm the available plan area, hoisting access and support steel with the drawings from the manufacturer.

Using the PMRC in Oman and the GCC

Forced draft evaporative condensers are used in the region in industrial refrigeration plants such as cold stores, food processing, dairies, beverage plants and logistics centres. Placing the fans at the base makes motor and fan maintenance easier and safer, as technicians do not need to work at the top of the unit. The condenser must be selected at the project’s design wet-bulb temperature, which can be high in coastal summer conditions, rather than at a catalogue standard condition.

For ammonia systems, the installation must follow the applicable refrigeration safety codes, including relief, purging and access. The spray water needs a water treatment programme, blowdown control and a Legionella control plan, because scale on the coil quickly raises the condensing pressure. Dust and sand enter through the fan inlets, so plan regular cleaning of the basin, strainers and spray nozzles. Leave free space around the fan inlets so the air supply is not restricted, and check the structural support for the operating weight.

Information to send with an enquiry

• Refrigerant and heat rejection capacity
• Condensing temperature and design wet-bulb temperature
• Make-up water quality
• Sound limits and quantity

Documents and quotation

The attached bulletin holds the PMRC and PMC-E selection tables and engineering data, plus the eco-PMRC dry and evaporative mode description for projects that need reduced water use. Seven Star LLC is an independent supplier in Muscat. For a quotation provide the refrigerant, heat of rejection, condensing temperature, design wet bulb and the plan area available. See also cooling equipment.