年間 8 号発行
ISSN 印刷: 1065-5131
ISSN オンライン: 1563-5074
Indexed in
Heat Transfer and Fluid Flow in Rectangular Fin and Elliptic Tube Heat Exchangers under Dry and Dehumidifying Conditions
要約
Experimental and numerical analyses were carried out to study the thermal-hydraulic and mass transfer characteristics of four-row rectangular fin and elliptic tube heat exchangers having a major/minor axis ratio of 2.83. Four types of rectangular finned configurations have been investigated for various inlet frontal velocities ranging from 1 to 6 m/s under dry and dehumidifying conditions: two staggered tube arrangements with fin heights of 7 mm and 10 mm, respectively; and two in-lined tube arrangements with fin heights of 7 mm and 10 mm, respectively. The results indicated that the sensible Colburn factor js and the friction factor f for the wet coils are, respectively, 56-71% and 2-16% higher than those for dry coils. In addition, a two-dimensional fin efficiency analysis for rectangular fins with elliptic tubes was presented for a wide range of air relative humidities and Biot numbers. It is shown that the fully wet fin effciency is lower than that of the dry fin by 20% and 31% with respect to fin heights of 7 and 10 mm.