Share

IIR document

Overall surface fin efficiency and dry angle for ammonia finned tube evaporators.

Number: 0164

Author(s) : KÆRN M. R., JENSEN J. K., MARKUSSEN W. B., KRISTOFERSSON J.

Summary

The use of the overall surface efficiency for modelling finned-tube surfaces is frequently encountered in the scientific literature. The method relies on the assumption of a constant temperature along the external surface of the tube. The appropriateness of this assumption depends on the tube material, wall thickness and the fin spacing. Typically, ammonia finned-tube evaporators employ thin walled stainless steel tubes with large fin spacing for the accommodation of frost during long frosting periods. The tubes have a thermal conductivity about 25 times lower than that of copper and 15 times lower than that of aluminium. The low thermal conductivity leads to temperature changes along the external tube surface in the axial direction and the assumption of the overall surface efficiency loses its validity. The current paper investigates the applicability of the overall surface efficiency both analytically and numerically. The objective was to derive and verify a simple expression for the tube efficiency, similar to the fin efficiency, which takes into account internal as well as external dissimilar convection coefficients. Furthermore, the effect of two-phase stratification and variations in dry angle were investigated numerically.

Available documents

Format PDF

Pages: 9 p.

Available

  • Public price

    20 €

  • Member price*

    Free

* Best rate depending on membership category (see the detailed benefits of individual and corporate memberships).

Details

  • Original title: Overall surface fin efficiency and dry angle for ammonia finned tube evaporators.
  • Record ID : 30029756
  • Languages: English
  • Subject: Technology
  • Source: 15th IIR-Gustav Lorentzen Conference on Natural Refrigerants (GL2022). Proceedings. Trondheim, Norway, June 13-15th 2022.
  • Publication date: 2022/06/13
  • DOI: http://dx.doi.org/10.18462/iir.gl2022.0164
  • Document available for consultation in the library of the IIR headquarters only.

Links


See other articles from the proceedings (169)
See the conference proceedings

Indexing