Air Cooled Heat Exchangers (ACHE): Complete Design & Selection Guide

Quick Answer

An air cooled heat exchanger (ACHE) — also called a fin fan cooler or air fin cooler — rejects heat from a process fluid directly to atmospheric air through finned tubes, eliminating the need for cooling water. ACHEs are essential in refineries, petrochemical plants, gas processing facilities, compressor stations, and power plants located in arid or water-scarce regions including the Middle East, North Africa, and Central Asia. The two main configurations are forced draft (fan below the tube bundle, pushing air upward — 80% of installations) and induced draft (fan above the bundle, pulling air through — preferred for high-temperature service and tight outlet temperature control). Design follows API Standard 661 (ISO 13076) and uses extended-surface finned tubes — typically L-foot, G-fin, or extruded aluminum fins on carbon steel or stainless tubes. While ACHEs require more capital and larger footprint than water-cooled alternatives, they eliminate water consumption, water treatment, biofouling, and water discharge issues — making them the standard cooling technology for hydrocarbon processing in water-scarce regions.

A refinery in Jubail, Saudi Arabia has no available cooling water. Seawater desalination is expensive and the process plant cannot tolerate the chloride risk. Treated water is scarce and costly. The ambient temperature reaches 50°C in summer. The cooling tower option simply doesn't work in this climate. The plant uses air cooled heat exchangers — hundreds of them — sized for the worst-case summer ambient, accepting the capital cost premium and larger footprint in exchange for eliminating water consumption entirely.

This is the situation across most of the Middle East, North Africa, Central Asia, and parts of Sub-Saharan Africa. Where cooling water is scarce, expensive, or chemically problematic, air cooled heat exchangers become not an option but a requirement. The technology has evolved over 70 years to handle some of the most demanding cooling duties in industry — refinery overhead condensers operating at 400°C, gas plant compressor coolers handling severe service, steam condensers for thermal power plants, LNG plant cooling loops.

ACHEs are also fundamentally different from shell and tube or plate heat exchangers. There is no water side to manage. Performance varies dramatically with ambient temperature (worst on the hottest summer days when cooling demand peaks). The footprint is 3-5× larger than equivalent water-cooled designs. The fan power consumption is significant. But for many applications — especially in water-scarce regions — these trade-offs are acceptable because the alternative is no cooling at all.

For refinery and petrochemical engineering procurement, gas plant designers, power plant specifications, and any project in water-scarce regions — this guide covers ACHE design comprehensively. The two main configurations (forced draft vs induced draft), the API Standard 661 governing global design practice, the fin tube types that determine thermal performance and temperature limits, applications across industries, and the selection criteria for choosing ACHE vs water-cooled alternatives.

For complete coverage of all heat exchanger types and how ACHE fits among them, see our Heat Exchangers Pillar Guide. For the water-cooled alternatives that ACHE replaces, see Shell & Tube Heat Exchangers: TEMA Types and Plate Heat Exchangers.

How an Air Cooled Heat Exchanger Works

An ACHE rejects heat from a hot process fluid to ambient air through extended-surface finned tubes. The complete heat transfer process:

1. Process fluid entry. Hot process fluid enters through inlet nozzles into headers — typically rectangular box headers at one or both ends of the tube bundle.

2. Flow through tubes. The process fluid flows through horizontal tubes (the tube bundle), which carry it across the structure of the unit. The tubes have finned outer surfaces — typically aluminum fins on carbon steel or stainless tubes.

3. Air flow. Atmospheric air is moved across the finned tubes either by fans (forced or induced draft) or by natural convection. Air enters at ambient temperature and leaves heated.

4. Heat transfer. Heat conducts from the process fluid through the tube wall, then through the fin material, and convects from the fin surface to the air. The fins are essential — bare tubes would have only 2-5% of the heat transfer area needed; finned tubes provide 15-25× the surface area for the same tube count.

5. Process fluid exit. Cooled process fluid exits through outlet headers. The temperature drop depends on the air flow rate, ambient temperature, and design point.

The basic configuration mounts horizontal tube bundles on legs or a pipe rack, with fans below (forced draft) or above (induced draft) the bundle. Air enters from beneath, passes over the finned tubes, and exits above the unit. Multiple tube bundles can be combined in a single bay (typically 2-6 bundles per bay) for higher capacities.

Why Finned Tubes Are Essential

Air has much lower heat transfer coefficient than water — typically 30-50 W/m²·K for air convection vs 5,000-10,000 W/m²·K for water in shell and tube. To compensate, ACHEs use extended-surface tubes with external fins.

Without fins (bare tubes): Required heat transfer area would be 20-50× larger than water-cooled — physically impractical for industrial duties.

With fins (finned tubes): External surface area is 15-25× the bare tube area. The fins multiply the air-side heat transfer surface, compensating for air's poor heat transfer coefficient.

Result: ACHEs achieve practical heat transfer rates within reasonable equipment size — though still 3-5× larger than equivalent water-cooled designs.

Forced Draft vs Induced Draft: The Primary Design Decision

The two main ACHE configurations differ in fan position relative to the tube bundle.

Forced Draft ACHE (~80% of installations)

The fan is located below the tube bundle, pushing air upward through the finned tubes.

Configuration:

• Tube bundle mounted at the top of the structure

• Fan(s) below the bundle in a "fan ring"

• Air enters at the bottom, exits at the top

• Motor and drive accessible from below (cooler air, easier maintenance)

Operating characteristics:

• Fan handles cool inlet air (ambient temperature)

• Lower air volume per BTU/hr compared to induced draft (air is denser at inlet)

• Less fan power required

• More uniform tube bundle access for inspection/repair

Advantages:

• Lower capital cost — typically 10-15% less than induced draft

• Lower fan power — handles cooler, denser air

• Easier maintenance — motors and drives in cooler environment

• Better tube bundle access — bundle is on top, accessible from above

• Better suited for very high-temperature process fluids — fans aren't exposed to hot exhaust

Limitations:

• Hot air recirculation potential — if outlet air drifts back to inlet, performance degrades

• Less uniform air distribution — air may channel along the path of least resistance

• Wind sensitivity — strong wind affecting one side of the unit can disrupt air flow

• Air leakage at periphery — some air bypasses the bundle if structure is not tight

Best for: Most refinery and petrochemical applications, especially where motor maintenance access matters. The default ACHE configuration unless specific requirements favor induced draft.

Induced Draft ACHE

The fan is located above the tube bundle, pulling air upward through the finned tubes.

Configuration:

• Fan(s) at top of structure

• Tube bundle below the fan

• Air enters at bottom (drawn by induced draft), exits through fan at top

• Motor and drive can be mounted above (in hot exhaust) or below

Operating characteristics:

• Fan handles heated exhaust air (higher volume, lower density)

• More uniform air distribution across the bundle (negative pressure pulls air evenly)

• Higher fan power required (lower density air)

• Less hot air recirculation (exhaust velocity is higher)

Advantages:

• More uniform air flow — pulls air evenly across the tube bundle

• Better close-approach performance — can achieve outlet temperatures closer to ambient

• Less hot air recirculation — high-velocity exhaust prevents reentry

• Better wind tolerance — bundle is less affected by horizontal wind

• Cleaner air at bundle — debris and dust are pulled past the bundle rather than blown into it

Limitations:

• Higher capital cost — typically 10-15% more than forced draft

• Higher fan power — handles lower-density hot air

• Motor in hot environment — if mounted above, requires high-temperature motor; if below, requires longer drive shaft

• More difficult tube bundle access — fan structure above limits crane access for tube replacement

Best for:

• Close approach applications (where outlet temperature must be within 8-15°C of ambient)

• Steam condensing service (turbine condensers)

• Locations with severe dust/sand environments

• Applications where hot recirculation must be minimized

A-Frame and V-Frame Configurations

Two tube bundles arranged in a triangular (A) or inverted-triangular (V) shape sharing one fan.

A-frame configuration:

• Two bundles meeting at the top

• Forced draft fan below

• Compact ground footprint

• Common for steam condensers

V-frame configuration:

• Two bundles meeting at the bottom

• Often induced draft

• Used in specific space-constrained applications

These configurations reduce the ground footprint by ~40-50% versus horizontal configurations, at the cost of more complex construction and slightly higher per-unit cost.

Quick Comparison Table

API Standard 661: The Governing Design Code

API Standard 661 / ISO 13076 — Air-cooled heat exchangers for general refinery service — governs ACHE design globally. The current edition (7th, 2013, with updates) specifies:

Material Requirements

• Tube material specifications and limits

• Fin material specifications (typically aluminum 1100 or 6063)

• Header material specifications and pressure ratings

• Bolting and gasket specifications

• Coating and corrosion protection requirements

Mechanical Design

• Tube sheet design (rolled, welded, or expanded joints)

• Header types (plug, removable cover, manifold)

• Tube layout and pitch

• Bundle support and tie-down requirements

• Fan and drive specifications

Performance Requirements

• Air flow rate specifications

• Sound levels (typically <85 dBA at 1 meter)

• Vibration limits

• Minimum operational efficiency

Header Types (Critical Specification)

The header is where process fluid enters/exits the tubes. API 661 specifies header types for different services:

Plug-Type Headers (most common for hydrocarbon service)

• Threaded plugs (one per tube) provide access to each tube end

• Removable plugs allow tube cleaning and inspection

• Required for all hydrocarbon gas and liquid service per API 661

• Stamped pressure ratings for project compliance

Removable Cover Plate Headers

• Single cover plate provides access to all tube ends

• Used for auxiliary services (lube oil, hot oil, cooling circuits)

• Lower cost than plug-type

• Less suitable for fouling service (limited tube cleaning access)

Manifold-Type Headers

• Welded construction with no maintenance access

• Lowest cost

• Used only for clean, non-fouling service

• Limited use in refinery applications

For complete coverage of header design considerations as they relate to broader heat exchanger configurations, see Shell & Tube Heat Exchangers: TEMA Types.

Fin Tube Types: The Heart of ACHE Performance

The fin tube determines the ACHE's thermal performance, temperature limits, and service life.

L-Foot (L-Footed) Fins

The most common fin type for general service.

Construction: Aluminum fin material wrapped around the tube, with the foot pressed flat against the tube surface. Continuous fin wrapping in a helical pattern.

Operating range:

• Temperature: Up to 130°C continuous, 175°C peak

• Fin spacing: 8-12 fins per inch typical (8-10 fpi most common)

Advantages:

• Lower cost than other fin types

• Good thermal performance

• Replaceable in field if damaged

• Wide availability

Limitations:

• Limited temperature (atmospheric oxidation accelerates above 130°C)

• Galvanic corrosion potential at fin-tube interface (especially with chlorides)

• Fin can detach from tube if mechanical impact

Best for: General process cooling at low to moderate temperatures.

LL-Foot (Overlapped L) Fins

L-foot fins with overlapping feet for better contact.

Operating range:

• Temperature: Up to 175°C continuous, 200°C peak

• Better than basic L-foot

Advantages:

• Improved thermal contact at fin foot

• Better corrosion resistance (less crevice space)

• Suitable for slightly higher temperatures

Limitations:

• Slightly more expensive than basic L-foot

• Similar limitations at very high temperatures

Best for: Moderate-temperature service where basic L-foot is insufficient.

G-Fin (Grooved/Embedded) Fins

Fins embedded in grooves machined into the tube surface.

Construction: Aluminum or copper fin material rolled into a groove cut into the tube. The fin is mechanically locked into the groove.

Operating range:

• Temperature: Up to 400°C continuous, 450°C peak

Advantages:

• Excellent fin-to-tube thermal contact (mechanical lock)

• High temperature capability

• Long service life

• Robust mechanical attachment

Limitations:

• Higher cost than L-foot

• More limited tube material options (groove must be machinable)

• Specialty manufacturing

Best for: High-temperature refinery service, hot oil systems, steam condensing service.

Extruded Fins

Aluminum sleeve extruded over the tube, with fins formed from the sleeve material.

Construction: Aluminum bimetallic tube with fins formed from extruded aluminum surrounding a steel inner tube.

Operating range:

• Temperature: Up to 200°C continuous, 250°C peak

Advantages:

• Excellent corrosion resistance

• Lower galvanic corrosion (aluminum-aluminum bond)

• Mass production economies

• Aluminum oxide layer protects fins

Limitations:

• Moderate temperature limit

• More expensive than L-foot

Best for: Marine and offshore applications, coastal refineries, areas with high humidity or salt exposure.

Welded Fins (Solid Tension Wound)

Fin material welded continuously to the tube.

Operating range:

• Temperature: Up to 500°C+ depending on material

Advantages:

• Highest temperature capability

• Best thermal contact (metallurgical bond)

• Excellent vibration resistance

• Suitable for severe service

Limitations:

• Highest cost

• Specialized manufacturing

• Limited size availability

Best for: Highest-temperature applications, severe vibration environments, critical service.

Fin Type Selection Matrix

Sizing Considerations

ACHE sizing is more complex than water-cooled designs because ambient air conditions vary continuously.

Step 1: Define Process Conditions

Inputs:

• Process fluid: type, flow rate, inlet temperature, outlet temperature, fouling factor

• Operating pressure, design pressure

• Maximum allowable pressure drop (process side)

Step 2: Establish Design Air Conditions

Critical for ACHEs:

• Design ambient dry-bulb temperature (typically 95th-99th percentile maximum summer temperature)

• Design ambient humidity (less critical than water-cooled designs)

• Site elevation (affects air density)

• Prevailing wind conditions

Example design ambients:

• Northern Europe: 30-35°C design

• Middle East / North Africa: 45-50°C design

• Tropical regions: 35-40°C design (year-round high humidity)

The design point typically uses the warmest expected ambient temperature so the ACHE provides adequate cooling on the hottest day.

Step 3: Calculate Heat Duty

Q = m × Cp × ΔT (process side)

The heat removed by air must equal the heat removed from process: Q = m_air × Cp_air × (T_out_air - T_in_air)

Step 4: Determine Air Flow Rate

m_air = Q / (Cp_air × ΔT_air)

Where:

• Cp_air ≈ 1.005 kJ/kg·K (at typical conditions)

• ΔT_air = typically 15-25°C (air temperature rise)

For 1 MW of heat duty with 20°C air temperature rise: m_air = 1,000,000 / (1,005 × 20) = ~50 kg/s = ~180,000 m³/h at 35°C

Step 5: Calculate Required Heat Transfer Area

Q = U × A × LMTD

Where:

• U = overall heat transfer coefficient (based on bare tube area, typical 200-600 W/m²·K)

• A = bare tube heat transfer area (m²)

• LMTD = log mean temperature difference

Key insight: Air flow rate and ambient temperature drive the LMTD. As air gets hotter (peak summer), LMTD decreases, requiring more area.

Step 6: Estimate Number of Bays

Standard tube bundle sizes:

• Small: 2-3 m wide × 3-6 m long, 2-4 tube rows

• Medium: 3-4 m wide × 6-12 m long, 4-6 tube rows

• Large: 4-5 m wide × 12-18 m long, 6-10 tube rows

For a 5 MW duty at 50°C design ambient:

• Required bare tube area: ~3,000 m²

• Per bay: ~600 m² (typical)

• Total: 5 bays

• Each bay: 4 m × 12 m × 6 tube rows

Step 7: Verify Performance Across Operating Range

Critical: ACHE performance varies dramatically with ambient temperature.

• Summer design (50°C): minimum performance, maximum cooling

• Spring/autumn (25°C): higher performance, slightly more cooling than needed

• Winter (5-15°C): much higher performance, may require variable speed fans or louver controls to reduce cooling

The unit must be designed for summer maximum but also provide control for winter operation (typically variable-pitch fan or VFD on fan motor).

Industry Applications

Refineries (Largest Application)

Refineries use hundreds of ACHEs across many process units:

Crude unit: Atmospheric and vacuum tower overhead condensers cool naphtha and gasoline vapors. Forced draft, G-fin tubes, plug-type headers for hydrocarbon service.

Catalytic cracking: Main fractionator overhead condensers, light cycle oil coolers. Forced draft, high temperatures, G-fin tubes.

Reformer: Reformate cooling, hydrogen-rich gas cooling. Forced or induced draft.

Hydroprocessing: Hydrotreater and hydrocracker product cooling. Often high temperatures, G-fin tubes.

Utilities: Cooling water systems (for closed-loop), lube oil cooling, air compressor intercoolers.

Standard configuration: Forced draft, A-frame for some condensing applications, API 661 compliant, plug-type headers, G-fin or L-foot tubes per temperature.

Petrochemical Plants

Similar to refineries but with more specialty service:

Ethylene production: Quench tower overhead, propylene refrigerant cycles, charge gas cooling.

Methanol production: Synthesis loop cooling, product condensation.

Ammonia synthesis: Ammonia loop cooling, synthesis gas cooling.

Polyethylene/polypropylene: Reactor cooling, recycle gas cooling.

Gas Processing and LNG

Gas processing plants are heavy ACHE users.

Gas processing: Compressor aftercoolers, dehydration cooling, NGL cooling, gas/liquid separators.

LNG plants: Refrigerant cycle cooling (propane, MR, etc.), feed gas cooling, regeneration heat rejection.

Compressor stations: Pipeline gas compressor coolers (intercoolers and aftercoolers). High duty per cooler, typically forced draft.

Power Generation

Combined cycle plants: Steam turbine condensers (often A-frame), feedwater pump motor cooling, compressed air cooling.

Solar thermal plants: Heat transfer fluid cooling (parabolic trough plants in deserts use ACHEs because cooling water is unavailable).

Geothermal plants: Working fluid cooling (Organic Rankine Cycle plants).

Petroleum Production (Upstream)

Production facilities: Crude oil cooling, produced gas cooling, glycol regeneration.

SAGD (Steam Assisted Gravity Drainage): Steam generation systems use ACHEs for produced fluid cooling and waste heat rejection.

Offshore platforms: Limited use due to space constraints; typically water-cooled with seawater is preferred offshore.

When ACHE Is the Right Choice

ACHEs are preferred over water-cooled alternatives when:

1. Cooling water is scarce or expensive

• Desert and arid regions

• Areas with seasonal water shortages

• Remote locations without water infrastructure

• Sites with very expensive freshwater sourcing

2. Cooling water quality is problematic

• High chloride content (causes corrosion in shell and tube)

• High dissolved solids (causes scaling)

• High biological content (causes fouling)

• Acidic or alkaline water

3. Water discharge restrictions

• Strict environmental regulations on discharge temperature

• Discharge permit costs are significant

• Receiving water bodies have temperature sensitivity

• Zero liquid discharge (ZLD) requirements

4. Process must be reliable in all conditions

• ACHE doesn't depend on water supply infrastructure

• Water supply interruptions don't affect cooling

• No water quality variations to manage

5. Long service life is critical

• ACHEs routinely last 30+ years

• Less corrosion than water-cooled (no chloride, scaling, biological)

• Lower long-term maintenance cost

When Water-Cooled Is Better

ACHEs are NOT the best choice when:

1. Cooling water is abundant and cheap

• Coastal locations with seawater access

• Locations with major freshwater bodies

• Inland sites with adequate well water

2. Tight outlet temperature requirements

• ACHE outlet limited by ambient + 8-15°C

• Water-cooled can achieve outlet within 5-10°C of cooling water

• Critical process requirements may need closer approach

3. Variable ambient conditions are problematic

• ACHE performance varies dramatically with ambient

• Continuous process with tight temperature control may need water cooling for stability

4. Space is severely constrained

• ACHE footprint is 3-5× water-cooled

• Indoor or compact facility constraints favor water cooling

5. Acoustic restrictions

• ACHE fan noise (typically 80-85 dBA at 1m) may exceed limits

• Some urban or sensitive locations require quieter alternatives

Common Specification Mistakes

After 15+ years supplying heat exchanger equipment to industrial and process customers:

Mistake 1: Design Ambient Too Low

Buyer specifies ACHE for "average summer ambient" rather than the actual design hot day. ACHE undersized for actual operating envelope; performance inadequate on hottest days; process throughput reduced during peak summer.

Prevention: Use 95th-99th percentile maximum ambient temperature for design. Reference local climate data, not generic averages. For critical service, use 99% percentile or annual maximum.

Mistake 2: Wrong Fin Tube for Temperature

Buyer specifies L-foot fins for high-temperature service (180°C+). Aluminum fins oxidize and degrade rapidly; thermal performance drops within 2-3 years; service life dramatically reduced.

Prevention: Match fin type to process temperature. L-foot ≤130°C, LL-foot ≤175°C, G-fin ≤400°C, welded ≤500°C+. Always specify fin type appropriate for the actual operating temperature plus safety margin.

Mistake 3: Inadequate Hot Air Recirculation Allowance

ACHE installed close to other equipment or in confined space. Hot exhaust air recirculates back to inlet; inlet temperature is 5-15°C above ambient; performance degrades; process upset.

Prevention: API 661 specifies minimum clearances. Account for prevailing winds and other equipment in the area. For very tight installations, consider induced draft (less prone to recirculation) or hot air recirculation calculations during design.

Mistake 4: Wrong Header Type for Service

Buyer specifies cover plate header for hydrocarbon service to save cost. API 661 actually requires plug-type headers for hydrocarbon gas and liquid service.

Prevention: Per API 661, hydrocarbon gas and liquid service requires plug-type headers. Cover plate headers are acceptable only for clean utility services (lube oil, hot oil, cooling water).

Mistake 5: Inadequate Winter Operation Capability

Buyer specifies fixed-speed fans only. In winter (low ambient), the ACHE provides too much cooling — process fluid is overcooled, viscosity issues, freezing in some applications.

Prevention: Specify variable-pitch fans, variable-frequency drives (VFD) on fan motors, or louvers/dampers to control air flow. For freezing-sensitive applications, include air recirculation provisions to prevent over-cooling.

Mistake 6: Insufficient Maintenance Access

Buyer specifies dense bay arrangement to minimize plot space. ACHEs installed too close together; cannot remove tube bundles for maintenance; future repair requires extensive equipment shutdown.

Prevention: API 661 specifies minimum clearances. Verify bundle removal access. For critical service, plan crane access for bundle extraction.

Mistake 7: Neglecting Sound Limits

Buyer specifies fans for maximum performance. Fans generate 90+ dBA noise; exceeds local environmental regulations or workplace exposure limits; expensive sound mitigation retrofits required.

Prevention: Sound criteria are part of API 661 specification. Verify local regulations and worker safety requirements. Specify low-noise fan options if needed (lower tip speed, more blades, larger diameter).

Specification Template

PROJECT: [Project Name]
APPLICATION: [Process unit and service]
LOCATION: [Country, Plant, Climate Zone]

PROCESS CONDITIONS:
- Process fluid: [Type, composition]
- Flow rate: [kg/s or m³/h]
- Inlet temperature: [°C]
- Outlet temperature: [°C]
- Operating pressure: [bar]
- Design pressure: [bar]
- Maximum allowable pressure drop: [kPa]
- Fouling factor: [m²·K/W]

AMBIENT CONDITIONS:
- Design ambient temperature: [°C — typically 99th percentile summer]
- Maximum ambient: [°C — for performance verification]
- Minimum ambient: [°C — for winter operation]
- Average humidity: [%]
- Site elevation: [m above sea level]
- Prevailing wind direction and speed

EQUIPMENT CONFIGURATION:
- Type: [Forced draft / Induced draft / A-frame]
- Number of bays: [Calculated]
- Number of bundles per bay: [Standard 2-6]
- Tube rows per bundle: [4-10]
- Bundle dimensions: [Width × Length]
- Total heat transfer area: [m²]

TUBE BUNDLE:
- Tube material: [Carbon steel / Stainless / Specialty alloy]
- Tube OD and thickness: [25.4mm × 2.11mm typical]
- Tube length: [m]
- Tube layout: [Triangular / square pitch]
- Tube pitch: [mm c/c]

FIN TUBES:
- Fin type: [L-foot / LL-foot / G-fin / Extruded / Welded]
- Fin material: [Aluminum 1100 / 6063 / specific spec]
- Fin spacing: [fpi]
- Fin thickness: [mm]
- Surface ratio: [extended area / bare area]

HEADERS:
- Header type: [Plug / Removable cover / Manifold]
- Header material: [Match tubes or specify]
- Header design pressure: [bar]
- Connections: [Flange size, class, type]

FANS AND DRIVES:
- Number of fans per bay: [1, 2, 4 typical]
- Fan diameter: [m]
- Fan type: [Fixed-pitch / Auto-variable pitch]
- Motor power: [kW per fan]
- Drive type: [Direct / V-belt]
- Motor enclosure: [TEFC / explosion-proof for hazardous areas]
- VFD on motor: [Required / Not required]

CONTROLS AND PROTECTION:
- Fan speed control: [Fixed / VFD / pitch control]
- Louvers/dampers: [Required / Not required]
- Hot air recirculation provisions: [For freezing service]
- Temperature monitoring: [Process outlet, motor temperatures]
- Vibration monitoring: [If specified]

STRUCTURAL:
- Support structure: [Steel frame, height to bottom of bundle]
- Foundation requirements: [Reinforced concrete]
- Walkways and platforms: [API 661 standard]
- Tube bundle removal access: [Crane access requirements]
- Wind load design: [Per local code, factor by region]
- Seismic design: [Per local code]

NOISE:
- Maximum allowable sound level: [dBA at 1m from fan inlet]
- Low-noise fan options: [If required]

CODE COMPLIANCE:
- API Standard 661 / ISO 13076
- ASME Section VIII Div 1 (for headers)
- PED (for European projects)
- Local pressure vessel codes

DOCUMENTATION REQUIRED:
- Thermal design calculation
- Mechanical design drawings
- Material test certificates
- Welding procedure qualifications
- Hydrostatic test certificates
- Performance test report
- Fan performance curves
- Sound level test report
- Vibration analysis report
- Operation and maintenance manual

DELIVERY:
- Required date: [Date]
- Shipping terms: [FOB / CIF / DDP]
- Delivery location: [Full address]
- Special transport considerations: [Large bundle dimensions]

Supply from Kasko Makine

Kasko Makine supplies air cooled heat exchangers for refineries, petrochemical plants, gas processing facilities, compressor stations, power plants, and industrial cooling applications across water-scarce regions:

ACHE configurations:

• Forced draft horizontal designs (standard refinery and petrochemical)

• Induced draft designs (close-approach service)

• A-frame configurations (steam condensers, space-constrained sites)

• Natural draft (specialty applications)

Sizing range:

• Small: 100 kW to 1 MW

• Medium: 1-10 MW

• Large: 10-100+ MW

• Multi-bay configurations for very large duties

Materials:

• Tubes: Carbon steel A179/A192, stainless 304/316L/321, alloy steels A335 P11/P22/P91, duplex 2205, titanium

• Fins: Aluminum 1100, aluminum 6063, copper, stainless (for severe service)

• Headers: Carbon steel, alloy steel, stainless steel per service

• Specialty alloys for HIC/SSCC service

Fin tube types:

• L-foot (general service)

• LL-foot (improved temperature/corrosion)

• G-fin (high temperature, refinery service)

• Extruded (marine, coastal)

• Welded (severe service)

Code compliance:

• API Standard 661 / ISO 13076

• ASME Section VIII Div 1 with U-stamp

• ASME Section VIII Div 2 (for high-pressure service)

• PED for European projects

• Other codes as required (GOST, etc.)

Documentation per shipment:

• API 661 datasheet completion

• Thermal calculation including ambient variation analysis

• Material test certificates (EN 10204 Type 3.1)

• ASME data sheets and Form U-1A

• Welding procedure qualifications (WPQ)

• Hydrostatic test certificates

• Fan performance curves and sound test reports

• Vibration analysis

• Operation and maintenance manuals

• Spare parts lists

Engineering services:

• Thermal design per API 661 with site-specific ambient analysis

• Mechanical design and stress analysis

• Hot air recirculation analysis for tight installations

• Fan selection and noise optimization

• Materials selection for severe service environments

• Wind and seismic analysis per site conditions

• 3D plot plan integration

Need an air cooled heat exchanger? Send us your duty (kW or MW), process fluid composition, flow rates, inlet/outlet temperatures, design ambient temperature, site location and elevation, applicable codes, and delivery requirements to info@kaskomakine.com or WhatsApp +90 (537) 521 1399. Our thermal design team will recommend the optimal configuration (forced/induced draft, A-frame, etc.), materials, fin type, and provide a complete API 661 compliant quotation within 72 hours. We deliver to refineries, petrochemical plants, and gas processing facilities across Africa, the Middle East, Central Asia, and beyond.

Continue Reading: Heat Exchanger Series

This air cooled heat exchanger guide is part of our comprehensive heat exchanger series:

• Heat Exchangers: 6 Types, Working Principles & Selection Guide — The master pillar covering all heat exchanger types

• Shell & Tube vs Plate Heat Exchanger — Comparison of the two main water-cooled types

• Shell & Tube Heat Exchangers: TEMA Types — Water-cooled shell and tube alternative for high-pressure service

• Plate Heat Exchangers: Types & Selection — Compact water-cooled alternative

• Expansion Joints: Types, Materials & Applications — Critical for piping systems connecting to ACHEs

FAQ SCHEMA

Q: What is an air cooled heat exchanger?
A: An air cooled heat exchanger (ACHE) — also called a fin fan cooler or air fin cooler — is a heat exchanger that rejects heat from a process fluid directly to atmospheric air, eliminating the need for cooling water. It uses finned tubes (typically aluminum fins on carbon steel or stainless tubes) to compensate for air's low heat transfer coefficient compared to water. Atmospheric air is moved across the finned tubes by fans (forced or induced draft) or by natural convection. ACHEs are essential in refineries, petrochemical plants, gas processing facilities, and power plants located in arid or water-scarce regions including the Middle East, North Africa, and Central Asia.

Q: What is the difference between forced draft and induced draft ACHE?
A: In forced draft ACHE, the fan is located below the tube bundle pushing air upward through the finned tubes — accounting for approximately 80% of installations. In induced draft ACHE, the fan is located above the bundle pulling air through the tubes. Forced draft has lower capital cost, lower fan power, easier maintenance access (motors in cooler air), and is better for high-temperature process fluids. Induced draft provides more uniform air distribution, better close-approach performance (closer to ambient), less hot air recirculation, and is preferred for steam condensing service and dust-heavy environments.

Q: What is API Standard 661?
A: API Standard 661 (also published as ISO 13076) — "Air-cooled heat exchangers for general refinery service" — is the globally-recognized standard governing the design, fabrication, inspection, and testing of air cooled heat exchangers for hydrocarbon and chemical processing applications. The current 7th edition (2013, with updates) specifies materials, mechanical design, header types (plug-type required for hydrocarbon service), performance requirements, fan and drive specifications, and inspection requirements. API 661 is the universal reference for ACHE procurement in refinery, petrochemical, and gas processing applications worldwide.

Q: When should I use an air cooled heat exchanger vs water cooled?
A: Air cooled heat exchangers are preferred when: (1) cooling water is scarce or expensive (desert, remote locations, water-stressed regions), (2) water quality is problematic (high chlorides, scaling, biological contamination), (3) strict water discharge regulations apply, (4) process reliability cannot depend on water supply, (5) long service life with minimal corrosion is critical. Water cooled alternatives (shell and tube, plate) are preferred when cooling water is abundant and cheap, tight outlet temperature requirements exist (within 8°C of cooling water), space is severely constrained, or acoustic restrictions limit fan noise.

Q: What types of fin tubes are used in air cooled heat exchangers?
A: Five main fin tube types are used in ACHEs: L-foot fins (most common, suitable to 130°C, lowest cost), LL-foot fins (overlapped L-foot, suitable to 175°C, better corrosion resistance), G-fin (grooved/embedded fins, suitable to 400°C, best for refinery overhead condensers), extruded fins (aluminum sleeve over steel tube, suitable to 200°C, best for marine/coastal applications), and welded fins (metallurgically bonded, suitable to 500°C+, best for severe service). Match the fin type to the operating temperature plus safety margin to ensure long service life.

Q: How is air cooled heat exchanger performance affected by ambient temperature?
A: ACHE performance varies dramatically with ambient temperature because air is the cooling medium. As ambient temperature rises (summer peak), the temperature difference between process fluid and air decreases, reducing heat transfer and increasing process outlet temperature. As ambient drops (winter), performance increases significantly — sometimes excessively, requiring fan speed reduction or louvers to prevent overcooling. ACHEs are sized for the maximum design ambient (typically 95th-99th percentile summer maximum) to ensure adequate cooling on the hottest day. The variable performance is the primary limitation of ACHEs compared to water cooling.

Q: Why are air cooled heat exchangers preferred in the Middle East?
A: The Middle East has multiple factors driving ACHE preference over water cooling: (1) cooling water is genuinely scarce and expensive — most freshwater is desalinated at significant cost, (2) seawater cooling is problematic due to high chlorides causing severe corrosion in shell and tube equipment, (3) environmental regulations limit discharge of heated seawater, (4) ambient temperatures (45-50°C design) are still workable for air cooling with adequate design margins, (5) ACHEs eliminate water supply dependency in remote desert facilities. The combination has made ACHE the standard cooling technology for refineries, gas processing, and petrochemical plants across the region.