An air-cooled heat exchanger, often called a fin fan cooler, removes heat from a hot fluid using ambient air instead of cooling water. The fluid runs through finned tubes while fans move air across them. Because it needs no water, it is widely used in oil, gas, petrochemical and power plants, and in locations where cooling water is scarce or expensive, which includes much of Saudi Arabia and the GCC. This guide explains how they work, the main designs, and what to check when you specify one.
How a fin fan cooler works
Hot process fluid enters a header and flows through a bundle of tubes. Fins on the outside of the tubes add surface area, because air carries heat away far less effectively than water. One or more fans push or pull ambient air across the bundle, and the fluid leaves cooler. The bundle sits in a frame, usually on a steel structure, with the fans and their drivers mounted above or below it.
Forced draft and induced draft
- Forced draft. The fan sits below the bundle and pushes air up through it. The fan and drive are easy to reach for maintenance, and the design is common.
- Induced draft. The fan sits above the bundle and pulls air through it. Airflow is more even, and hot air is discharged higher, which reduces recirculation. It also protects the tubes somewhat from sun, rain and hail.
Air cooler or condenser
The same construction is used for two jobs. An air cooler cools a liquid or gas without changing its phase, for example lube oil, jacket water or process gas. An air-cooled condenser turns a vapour into liquid, for example steam or process vapour. Condensers need careful design of the tube layout and drainage so condensate does not collect inside the tubes.
Finned tubes
The fins are what make an air cooler work. Common types include extruded fins, where the fin is formed from the tube wall itself, and wound or embedded fins, where a metal strip is wrapped or set into a groove on the tube. The right choice depends on the operating temperature, the corrosive atmosphere and how much surface is needed. In a dusty, hot climate, fin spacing and cleaning access matter, because fouled fins lose capacity quickly.
Standards: API 661 and TEMA
API 661, also published as ISO 13706, covers air-cooled heat exchangers for refinery and related service. Oil and gas projects often call for it, together with the pressure vessel code for the tube side. The tube-side headers and tubes are designed to the applicable code, and the project specification usually sets inspection and testing. When you request a quotation, state the standard and any third-party inspection up front.
Air-cooled or water-cooled
- Water use: an air-cooled unit needs none, a shell and tube exchanger needs a supply of cooling water.
- Approach temperature: an air cooler can only cool the fluid to somewhat above the ambient air temperature, so the hottest summer day sets the design. Water-cooled units can usually cool closer.
- Size and cost: air coolers need more surface and floor area, but they avoid the water treatment, piping and fouling problems of cooling water.
- Power: air coolers use fan power, which should be weighed against pumping cooling water.
What to tell us for a quotation
- The fluid, flow rate, and inlet and outlet temperatures
- Heat duty, if known
- Design pressure and allowable pressure drop
- Design ambient air temperature and site elevation
- Whether the unit is a cooler or a condenser
- Materials, standards and inspection requirements
Frequently asked questions
What is a fin fan cooler?
A fin fan cooler is an air-cooled heat exchanger. Hot fluid flows through finned tubes while fans blow ambient air across them, so no cooling water is needed.
What is the difference between forced draft and induced draft?
In forced draft the fan is below the bundle and pushes air up through it. In induced draft the fan is above the bundle and pulls air through it, which gives more even airflow and less hot-air recirculation.
What is API 661?
API 661, also published as ISO 13706, is the standard for air-cooled heat exchangers in refinery and related service.
Why are air coolers popular in Saudi Arabia?
They need no cooling water, which saves a scarce resource and removes the cost of treating and circulating it. The design must allow for high summer air temperatures.
Power Energy Gulf supplies Flovex heat exchangers, including air coolers and condensers, for industrial plants across Saudi Arabia and the GCC. See our industrial heat exchangers page, read our guide to heat exchanger types, or contact us with your fluid, temperatures and site conditions and we will help you select a suitable unit.