Study on Air Cooled Heat Exchanger with Corrugated Fin Surfaces : 2nd Report, Characteristics of Corrugated Straight Fin Surfaces

Abstract

Air cooled heat exchangers with corrugated fin surfaces are now in mass production for automotive and air conditioning applications. In these heat exchangers, the fin length is short relative to the equivalent diameter, and particularly, in heat exchangers with corrugated straight fins, heat transfer and flow friction characteristics are governed mainly by the entrance flow region. Most design data so far reported are, however, concerned with a fully developed flow rather than an entrance flow. In this paper, basic heat transfer and flow friction characteristics are presented on corrugated straight fin surfaces with the ratio of fin length to equivalent diameter, less than 26.5, by employing the steady state and transient techniques. These data were rearranged by the aid of analysis on the entrance region between parallel flat plates, and the result expressed in a correlation in the form, N_u=φ[R_e, P_r, (d_e/L), R], f=Ψ[R_e, (d_e/L)], applicable to the optimum design of air cooled heat exchangers with corrugated straight fin surfaces.