EVAPCO ATC-E Induced Draft Evaporative Condenser

Induced draft evaporative condensers for industrial refrigeration plants

The EVAPCO ATC-E is an induced draft, axial fan evaporative condenser built for large ammonia and halocarbon refrigeration systems. Hot gas from the compressors enters the coil, water from the sump is sprayed over the tubes, and air is drawn through louvers at the base and up over the coil against the falling water. A small part of the water evaporates, which removes the heat of condensation, and the condensed refrigerant drains from the coil. EVAPCO describes the ATC-E as its premier induced draft condenser for the industrial refrigeration market.

Units are offered as single cells in widths from 4 ft up to 12 ft and as multi-cell arrangements for large plants; the printed ratings run from 35 to 2,637 ammonia tons at standard conditions, across a long list of single and multi-cell models. EVAPCO also lists 7 ft wide box sizes for containerized export shipments, which matters for projects supplied overseas.

Technical specifications

Model range and engineering data

Selection starts from the heat of rejection, or for open reciprocating compressors from evaporator tons, multiplied by a factor from the bulletin tables for the condensing temperature and wet bulb; the result is matched to unit MBH in Table 3. In the printed worked example, a 450 ton ammonia load with 500 BHP compressors at 96.3 F condensing and 78 F wet bulb gives about 9,142 MBH and points to an ATC-639E or ATC-XC641E. Selected rows from the engineering tables:

The tables also give coil volume, spray pump size and flow, remote sump gallons, connection sizes and unit dimensions. The note states dimensions are subject to change and not for pre-fabrication, and that coil connection quantity changes with refrigerant and design conditions.

Construction and maintenance features

The sloped clean pan basin drains completely and can be inspected with the pumps running, the water-and-sight-tight PVC inlet louvers keep sunlight out to limit algae and block splash-out even with the fans off, and an optional hinged air inlet access door gives quick access to the make-up float and strainer on models above ATC-165E. A field seam design eliminates up to 66 percent of fasteners to reduce leaks and installation cost.

For corrosive environments EVAPCO lists stainless steel basin, casing and coil options, and factory mounted water treatment: a chemical-free Pulse-Pure system or a controlled release solid chemistry feeder. Variable frequency drive control by others may need extra components such as shaft grounding brushes, load reactors or filters, as the bulletin warns.

The drive is a Power-Band belt with aluminum alloy sheaves on 8 ft and wider models, with the motor mounted outside the casing on the smaller units under a swing-away cover, or inside the fan casing on a swing-out base on the larger ones, so belt tension and bearing grease lines are reached from outside. Inverter duty motors are standard, the sump strainer is stainless steel, and all components that see water are specified in corrosion resistant materials.

Using the ATC-E in Oman and the GCC

Evaporative condensers are used in the region in industrial refrigeration plants such as cold stores, food processing plants, dairies, beverage plants, poultry and fish processing, and logistics centres. Evaporative condensing allows lower condensing temperatures than air-cooled condensers in hot climates, which reduces compressor energy, but the condenser must be selected at the project’s design wet-bulb temperature, which can be high in coastal summer conditions.

For ammonia systems, the condenser 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 air inlets, so plan regular cleaning of the basin, strainers and spray nozzles. Leave access space around the unit for maintenance, and check the structural support for the operating weight.

Record coil and water readings at each service visit, so trends can be seen early.

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 contains the full set of ATC-E tables and selection procedure. Seven Star LLC is an independent supplier based in Muscat. For a condenser quotation we need the refrigerant, total heat of rejection or compressor data, condensing temperature, design wet bulb and the cell layout allowed. Compare other equipment in cooling equipment.