Performance investigation of plain and finned tube evaporatively cooled heat exchangers

Ala Hasan (Corresponding Author), Kai Sirén

Research output: Contribution to journalArticleScientificpeer-review

61 Citations (Scopus)

Abstract

The performance of two evaporatively cooled heat exchangers is investigated under similar operating conditions of air flow rates and inlet hot water temperatures. The heat exchangers are plain and plate-finned circular tube types which occupy the same volume. Spray water, which is circulated in a closed circuit, is injected onto the exposed surfaces of the tubes and fins. The contact between air and spray water results in evaporative heat transfer. The tubes are copper, 10 mm o.d. The finned configuration is constructed by introducing 0.5 mm thick copper plates between the tubes, with a total area ratio of four. A substantial increase in heat transfer takes place for the plate-finned tubes. The increase is 92-140% for air velocities from 1.66 to 3.57 m s-1. A model is used to calculate the thermal performance of the plain and finned tubes assuming a constant spray water temperature in the heat exchanger. The wet-finned surfaces show low fin efficiency compared with dry surfaces. An energy index defined as the ratio of volumetric thermal conductance to air pressure drop per unit length is found to be close for the two heat exchangers. This reveals higher thermal utilisation of the occupied volume by the finned tubes with the same energy index.

Original languageEnglish
Pages (from-to)325-340
Number of pages16
JournalApplied Thermal Engineering
Volume23
Issue number3
DOIs
Publication statusPublished - Feb 2003
MoE publication typeA1 Journal article-refereed

Keywords

  • Evaporative
  • Heat exchanger
  • Plate-fin
  • Wet

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