How to use Industrial Air-Cooled Heat Exchanger Sizing& Axial Fan Calculator
- Enter Process Heat Duty Requirement (kW) and adjust the options as needed.
- Run the tool and inspect its results, evidence and limitations.
- Copy or download the result, then verify it against the actual website, source data or business records.
Try a concrete example
In a petrochemical hydrotreating cooling loop with 1500 kW heat duty, process fluid cooling from 95°C to 50°C under 35°C ambient air: under API 661 crossflow heat transfer, outlet air reaches 53.6°C with 25.1°C LMTD (Ft = 0.94); using extruded aluminum high-fin tubes (18.5 surface area ratio) and overall U of 32.5 W/(m²·K), required extended external heat transfer area is 1840.5 m² (equivalent to 99.5 m² bare tube area); face velocity is 2.8 m/s, requiring 265,000 m³/h (155,972 CFM) total airflow at 142.0 Pa air-side static pressure drop; in forced draft layout, 2 x 2.4m diameter wide-chord axial fans with 11.0 kW motors are selected (total 16.8 kW shaft power with ample reserve), ensuring stable pressure drop and thermal duty.
How to interpret results
Air-Cooled Heat Exchangers (ACHE) are vital industrial heat rejection equipment across petroleum refining, natural gas processing, petrochemicals, and thermal power plants, cooling process fluids with ambient air rather than fresh water. Sizing complies strictly with API 661 and ISO 13706 standards. Hot process fluid circulates through tube bundles while ambient air is forced or induced crossflow across the bundle by axial fans. Because the air-side convective heat transfer film coefficient (typically 40 to 70 W/(m²·K)) is far lower than tube-side liquid coefficients, ACHEs utilize extended-surface finned tubes that expand bare surface area by 15x to 22x. ACHEs feature either forced draft (fans below bundle pushing ambient air) or induced draft (fans above bundle pulling air through): forced draft keeps fans and motors in cool ambient air for extended bearing life and ground-level maintenance; induced draft yields superior air distribution, higher stack discharge velocities, and zero hot air recirculation, but subjects drive components to hot exhaust air. Accurate calculation of air-side pressure drops and fan motor horsepower prevents process temperature pinch and summer capacity bottlenecks.
Frequently asked questions
Why do large petrochemical and natural gas projects prefer air-cooled heat exchangers over wet cooling towers?
First, massive water conservation: in arid or desert oilfields where water is scarce and costly, ACHEs reject heat into ambient air, eliminating 100% of industrial cooling water consumption. Second, eliminating scaling, chemical corrosion, and blowdown wastewater: avoiding cooling tower water treatment (biocides, scale inhibitors, acid dosing) and environmental blowdown treatment, preventing tube fouling from water hardness. Third, structural layout flexibility: ACHEs mount directly onto pipe racks or structural roofs, freeing valuable plant floor footprint.
What are the key aerodynamic and operating differences between forced draft and induced draft ACHEs?
First, forced draft (fans below bundle): axial fans push ambient air upward through tubes. Advantages: fans, belts, and motors operate in cool ambient air for longer mechanical life, and ground-level structural mounting facilitates inspection; disadvantages: lower face discharge velocity and vulnerability to hot air recirculation during lateral crosswinds. Second, induced draft (fans above bundle): fans draw heated air through the bundle and discharge upward at high velocity. Advantages: highly uniform face velocity across tubes, stack jet dispersion preventing hot plume recirculation, and built-in sun/rain shielding; disadvantages: fans and bearings endure hot exhaust air (50°C to 80°C), requiring high-temperature rated drive components and elevated deck maintenance.
What are the key technical advantages of extruded aluminum high-fin tubes over wrap-around L-fin tubes?
First, bimetallic corrosion barrier: extruded fin tubes place a heavy-wall aluminum muff over the steel base tube, cold-rolling the fins integrally under high pressure. The seamless aluminum collar completely encases the base tube, eliminating atmospheric galvanic corrosion even in offshore salt spray or acid rain. Second, permanent contact thermal resistance: wrap-around L-fins rely solely on mechanical tension, which loosens under thermal cycling, creating air gaps that increase contact thermal resistance by over 300%; extruded fin roots remain integrally bonded with the sleeve, ensuring zero thermal decay over 20+ years.
How is face velocity optimized against fan static pressure and shaft power in ACHE design?
Per API 661 guidelines, bundle face velocity is typically engineered between 2.5 and 3.5 m/s: First, if velocity is below 2.0 m/s: air-side convective heat transfer film coefficients drop sharply, requiring substantially oversized bundles and costly structural framing. Second, if velocity exceeds 4.0 m/s: air friction pressure drop escalates with velocity to the 1.8-2.0 power, driving up fan total pressure, motor kW, and aerodynamic blade noise. Wide-chord twisted aluminum axial fans running at low RPM deliver high airflow and low noise at minimum specific power.