Microchannel heat exchangers for charge minimization in air-cooled ammonia condensers and chillers

Pega Hrnjak, Andy D. Litch

Research output: Contribution to journalArticlepeer-review


This paper presents experimental results from a prototype ammonia chiller with an air-cooled condenser and a plate evaporator. The main objectives were charge reduction and compactness of the system. The charge is reduced to 20 g/kW (2.5 oz/Ton). This is lower than any currently available air-cooled ammonia chiller on the market. The major contribution comes from use of microchannel aluminum tubes. Two aluminum condensers were evaluated in the chiller: one with a parallel tube arrangement between headers and "microchannel" tubes (hydraulic diameter Dh = 0.7 mm), and the other with a single serpentine "macrochannel" tube (Dh = 4.06 mm). The performances of the chiller and condensers are compared based on various criteria to other available ammonia chillers. This prototype was made and examined in the Air Conditioning and Refrigeration Center in 1998, at the University of Illinois at Urbana-Champaign.

Original languageEnglish (US)
Pages (from-to)658-668
Number of pages11
JournalInternational Journal of Refrigeration
Issue number4
StatePublished - Jun 2008


  • Air-cooled condenser
  • Ammonia
  • Experiment
  • Heat exchanger
  • Liquid chiller
  • Micro-channel
  • Reduction
  • Refrigerant charge

ASJC Scopus subject areas

  • Building and Construction
  • Mechanical Engineering


Dive into the research topics of 'Microchannel heat exchangers for charge minimization in air-cooled ammonia condensers and chillers'. Together they form a unique fingerprint.

Cite this