Estimation of heat transfer coefficient on the vertical plate fin of finned-tube heat exchangers for various air speeds and fin spacings

The finite difference method in conjunction with the least-squares scheme and experimental temperature data is proposed to predict the average heat transfer coefficient over(h, ̄) and fin efficiency η_f on a vertical square fin of one-circular tube plate finned-tube heat exchangers for various air speeds and fin spacings. The distribution of the heat transfer coefficient on the fin can be very non-uniform, thus the whole square fin is divided into several sub-fin regions in order to predict the over(h, ̄) and η_f values. These two predicted values can be obtained using the present inverse scheme in conjunction with the knowledge of the temperatures recordings at several selected measurement locations. The results show that the heat transfer coefficient on the upstream fin region can be markedly higher than that on the downstream fin region. The over(h, ̄) value increases with increasing the fin spacing S and air speed V_air, and the η_f value decreases with increasing the S and V_air values. The over(h, ̄) and η_f values respectively approach their corresponding asymptotical values obtained from a single fin as S → ∞. The distributions of the fin temperature depart from the ideal isothermal situation and the fin temperature decreases more rapidly away from the circular center with increasing the fin spacing and air speed.