Airside characteristics of heat, mass transfer and pressure drop for heat exchangers of tube-in hydrophilic coating wavy fin under dehumidifying conditions

Abstract

The airside heat, mass and momentum transfer characteristics of seven wavy fin-and-tube heat exchangers with hydrophilic coating under dehumidifying conditions were experimented. The test inlet air dry bulb temperatures were 20, 27 and 35oC, the inlet relative humidity were 50%, 60%, 70% and 80%, and the air velocity were 0.5, 1.0, 2.0, 3.0 and 4.0ms−1. The test results indicate that both the Colburn jm factor and the Colburn jh factor decrease with the increase of fin pitch, and this phenomenon becomes more and more pronounced as Reynolds number decreases. The friction factor is very sensitive to the change of fin pitch, and the friction factor shows a cross-over phenomenon as fin pitch changes. The Colburn jh factor decreases and the Colburn jm factor increases when the number of tube rows increases, while the friction performance is insensitive to the change of the number of tube rows. The effects of inlet relative humidity on the heat transfer and friction performance can be omitted, but the Colburn jm factor decreases with the increase of the inlet relative humidity. The predictive ability of the available state-of-the-art heat transfer and pressure drop correlations was evaluated with the experiment data of the present study. The new heat, mass and momentum transfer correlations were proposed to describe the present test results according to the multiple linear regression technique. The mean deviations of the proposed jh, jm and f correlations are 6.3%, 8.9% and 7.9%, respectively. Comparing to published data reduction method, the process line on psychrometric chart of fin-and-tube heat exchanger for partially wet conditions and more accurate overall heat transfer coefficient equation are put forward in this paper.