New Air-cooled Heat Exchanger Expands RTC Capabilities

David Burton, Director, Research & Technology Center
Salem Bouhairie, Senior Project Engineer, Research

Airside heat transfer resistances limit the performance of an air-cooled heat exchanger (ACHE). To address member concerns about airflow predictions, HTRI is expanding its current research capabilities with the installation of a modular ACHE at the Research & Technology Center (RTC).  We plan to couple CFD numerical results with physical field experiments under natural, forced-, and induced-draft operations. Field research includes the impact of wind, ground clearance, lateral obstructions, and hot air recirculation.

Our ACHE is designed according to practical API 661 [1] guidelines, with reconfigurable mechanical components. Unlike conventional production-type air coolers, this test unit features options for forced- or induced-draft orientations, removable tube bundle air seals, and box or shaped plenums. To record airside measurements, a traverse system holds various anemometers, thermocouples, and temperature loggers, as well as static and total pressure sensors, along the ACHE.

The new ACHE features

  • two 1.5-m (5-ft) axial fans
  • a 1.8-m (6‐ft) wide bundle with six rows of 4.9-m (16‐ft) long tubes
  • extruded fin tubes (stainless steel tubes sleeved with aluminum fins)
  • chimneys for natural draft operation
  • manual louvers to control air flow and temperature
  • a variable frequency drive (VFD)
  • variable ground clearance
  • obstacles beside and under the air cooler

This air cooler is designed to operate with a maximum duty of 4.7 MW (16 MMBtu/hr). The new unit allows us to use water cooling services to address field operation concerns, such as air flows of low Reynolds numbers with fans on and off.



  1. API STD 661: Petroleum, Petrochemical, and Natural Gas Industries—Air-cooled Heat Exchangers, 7th ed., American Petroleum Institute, Washington, DC (2013).


HTRI-1 Water/Steam Cooler

HTRI’s new air-cooled heat exchanger, the HTRI-1 Water/Steam Cooler (WSC), connects to the RTC boiler water supply and is ready to cool the tubeside process.


HTRI-1 Water/Steam Cooler

Hail screens are optionally mounted to protect the tube bundle, increasing airside pressure losses that the fan motor needs to overcome.


HTRI-1 Water/Steam Cooler

The air-cooler fan is housed in a deep ring to accommodate both forced-draft (shown) and induced-draft operations.