Performance of Rectangular Fin in Wet Conditions: Visualization and Wet Fin Efficiency

Abstract

An experimental study concerning the performance of a rectangular fin in both dry and wet condition was carried out. The visual observation of the dehumidifying phenomenon identified four regions, including the fully dry, very fine droplet, larger droplet, and film-like region. Experimental results showed that the effect of dry bulb temperature on the wet fin efficiency is very small. The dry fin efficiency is about 15–25 percent higher than that of the corresponding wet fin efficiency. For fully wet condition, the effect of relative humidity on the fully wet fin efficiency is also small. For partially wet surface, a considerable influence of the relative humidity on the fin efficiency is encountered. Test results for the fully wet fin efficiency agree well with some of the previous studies but disagree with some of the previous investigations. The main cause to this controversy may be attributed to the formulation of the relation between the humidity ratio and the fin temperature. The fully wet fin efficiency decrease slightly with increase of fin base temperature. However, the effect of fin base temperature on the dry fin efficiency is relatively small.

Numerical Analysis of Heat and Mass Transfer in a Fin-and-Tube Air Heat Exchanger under Full and Partial Dehumidification Conditions

“…As reported by Lin et al (2001), most of the investigators applied the Chilton-Colburn analogy to set a relationship between the mass transfer coefficient and the sensitive heat transfer coefficient, hence; the following relation is reported and used in our work: …”

“…al., 2000, Chen, 1991, Lin et al, 2001, Elmahdy & Biggs, 1983, Coney et al, 1989. The most proposed relation between "the difference of the air humidity ratio and that evaluated at the fin temperature" and "the difference of the ambient temperature and fin temperature" used a factor named the condensation factor.…”

“…Their results show that the estimated fin efficiency under partially and fully wet conditions is sensitive to the relative humidity. Lin et al (2001) mentioned that the effect of the relative humidity on the fully wet fin efficiency of extended surface was very confused. This work's aims to estimate the overall heat transfer coefficient and the fin efficiency as well as the total heat rate exchanged under partially or fully wet conditions using an appropriate numerical procedure.…”

Shape optimization for the minimum volume of pin fins in simultaneous heat and mass transfer environments

“…For example, when humid air encounters the surface of a cooling coil whose temperature is lower than the dew-point temperature, condensation of moisture will take place. Extensive research [1][2][3][4][5][6][7][8][9] has already been undertaken to analyze the effect of condensation on the performance of rectangular geometric longitudinal fins. It is important to note that in each of these studies, a suitable fin geometry (rectangular, trapezoidal, triangular, etc.)…”

“…Kundu [7] used a decomposition method to carry out a thermal analysis of straight fins under fully wet and partially wet conditions, assuming the humidity ratio of saturated air to be a polynomial function of the fin temperature. Lin et al [8] experimentally investigated the performance of a rectangular fin in both dry and wet conditions. The thermal analysis and optimization of longitudinal and pin fins of uniform thickness subject to fully wet, partially wet and fully dry surface conditions were carried out analytically by Kundu [9].…”