Efficient, compact air coolers equipped with dual enhanced finned tubes

Improve plant efficiency and reduce construction costs

DIESTA is an innovative new finned tube technology, dedicated to air cooled heat exchangers, using enhanced surfaces. The technology allows to improve plant efficiency and to reduce construction costs without deviating from the robust design requirements of oil & gas industry standards such as API 661.

DIESTA - the tube

DIESTA, short for Dual Internally and Externally Structured Tube for Air-coolers, combines two established technologies for the outside and inside of a tube. The DIESTA tube is a bimetallic finned tube with an aluminum sleeve fully covering the base carbon steel tube. The outside aluminum fins are embedded into the grooves of the aluminum sleeve. To optimize the air- and tubeside heat transfer performance, enhancement structures are applied on both sides. The aluminum fins on the airside combine both a groove and a dimple structure.

  • Airside: robustness towards fouling, cleaning as well as mechanical strength of the fins equally to standard extruded finned tubes
  • Tubeside: increase of tubeside heat transfer coefficient while controlling the pressure drop ensured by the internally helical fin structure

Key application fields

  • LNG air-cooler fields including MR compressor inter- and aftercoolers, C3 refrigerant coolers (desuperheater, condenser and subcooler)
  • Ethylene quench-water air cooler fields (focus naphtha-based crackers)
  • Other areas: gas processing plants, gas compression stations, refineries
  • Available for greenfield and revamp debottlenecking projects

Different internal structures are available for:

  • Gas cooling
  • Condensation
  • Liquid cooling (incl. high viscous fluid Pr < 100)

DIESTA production program


  • 1 inch, 1 ¼ inch & 1 ½ inch tube OD
  • Plain end core tube thickness: - 2.11 mm min. (in accordance with API 661)
  • Fin density : 10 fpi (394 fpm)


  • Fin material: aluminum 1100
  • Carbon steel (ASME SA179 & SA334 Grade 6)

Benefits at a glance

  • CAPEX savings | Up to 20 % air-cooler field length reduction
    Savings in structures, piping, wiring and foundation
  • Increased Revenue | Substantial benefits depending on individual process conditions
    LNG air-cooler optimization does lead to up to 3 % capacity increase
  • Reduced energy consumption and CO2 footprint:
    System efficiency improvement (reduction of compression work)