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Effect of nanoparticle additives on the refrigerant and lubricant mixtures heat transfer coefficient during in-tube single-phase heating and two-phase flow boiling.

Author(s) : DEOKAR P. S., CREMASCHI L.

Type of article: Article, IJR article

Summary

Lubricant in heat exchangers acts as a contaminant and it affects the heat transfer and pressure losses. Nanolubricants, that is, nanoparticles dispersed in lubricant oils, have shown potential to augment heat transfer rates in refrigerant direct-expansion evaporators. However, the mechanisms of such heat transfer enhancements are still unclear. Experiments were conducted to study the saturated two-phase flow boil- ing heat transfer phenomena of refrigerant R410A with two nanolubricants in a 9.5 mm I.D. smooth cop- per tube. The nanolubricants had non-spherical ZnO nanoparticles and spherical ?-Al2 O3 nanoparticles dispersed in Polyolester (POE) lubricant. Al2 O3 nanolubricant shared similar thermal conductivity in the wet state as that of ZnO nanolubricant. However, Al2 O3 nanolubricant had about 15% higher heat trans- fer coefficient that ZnO nanolubricant. The heat transfer coefficients of R410A-nanolubricant mixtures degraded by about 20% with respect to that of the R410A, but improved at higher vapor qualities. The experiments showed that long-term flow boiling testing of R410A and nanolubricant mixtures resulted in a continuous gradual increase of the heat transfer coefficient. In smooth copper tubes, nanoparticle deposition on the tube inner wall, which was experimentally observed, and the near wall interactions of nanoparticles promoted additional nucleate boiling and led to such increase.

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Pages: 142-152

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Details

  • Original title: Effect of nanoparticle additives on the refrigerant and lubricant mixtures heat transfer coefficient during in-tube single-phase heating and two-phase flow boiling.
  • Record ID : 30027295
  • Languages: English
  • Source: International Journal of Refrigeration - Revue Internationale du Froid - vol. 110
  • Publication date: 2020/02
  • DOI: http://dx.doi.org/10.1016/j.ijrefrig.2019.10.018

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