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Impact of oil on flow boiling of ammonia and of R-723 in smooth horizontal tubes.

Author(s) : BOYMAN T.

Summary

The average flow boiling heat transfer coefficients during the evaporation of the natural refrigerant ammonia (R-717) and of the azeotropic mixture ammonia/dimethylether (R-723) are summarized, thus including the impact of a frequently-used fully-synthetic oil (PAO ISO-VG 68). Tests were run in a 24-m long serpentine type evaporator equipped with smooth horizontal tube sections of 14-mm inner diameter connected by U-bends. The flow boiling of both refrigerants was studied at evaporation temperatures from -10 to 10°C, with mass velocities ranging from 40 to 260 kg/(m2.s), while average heat fluxes varied between 10 and 60 kW/m2. Small quantities of PAO-oil, which is immiscible with ammonia and miscible with R-723 under the test conditions, cause a considerable reduction of the boiling heat transfer coefficient mainly in the regions with annular two-phase flow regime. This paper gives an overview of the present applied research work.

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Pages: ICR07-B1-1399

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Details

  • Original title: Impact of oil on flow boiling of ammonia and of R-723 in smooth horizontal tubes.
  • Record ID : 2007-2471
  • Languages: English
  • Source: ICR 2007. Refrigeration Creates the Future. Proceedings of the 22nd IIR International Congress of Refrigeration.
  • Publication date: 2007/08/21

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