碩士 / 元智大學 / 機械工程研究所 / 83 / This study is concerned with heat transfer and pressure drop
characteristics of fin-and-tube heat exchangers. Experiments
were carried out in two wind tunnels with various operating
conditions. Results are presented as plots of friction factors,
sensible j factors and total j factors against Reynolds number
(ReDc ) based on tube collar diameter. Eighteen samples of wavy
fin heat exchangers with different geometrical parameters,
including row number, fin pitch and flow arrangement were
tested in an open type induced flow wind tunnel under dry
operating condition. It is found that the effect of fin pitch
has negligible effect on the Colburn j factors, and the row
effect increase with the increasing Reynolds number for inline
layout. Heat transfer and friction factor correlations are
obtained for staggered tube banks with wavy fins in the range
of Reynolds numbers ReDc = 300~7,000. Correlations were
proposed to predict the experimental data. The correlations can
correlate the present data within 10% for j factors and within
15% for friction factors. In addition, two louver fin heat
exchangers were tested in a forced-circulation wind tunnel
tested under both dry and wet operating conditions. One of the
heat exchangers is treated with hydrophilic coating and the
other is uncoated surface. Experimental data show that the
coating reduces friction factors by 30-to-40% under wet
operating conditions. In addition, experimental data indicate
that the sensible j factors decrease with relative humidity,
and the friction factors f and total j factors do not change
with the relative humidity. Nonetheless, if the surface is not
complete wet, the friction factors show a noticeable decrease
as compared to completely wet surfaces. It is suggested that
the friction factor of the partially wet surfaces can be
obtained as a combinations of the completely dry and completely
wet friction factors depend on the portion of the wet surfaces.
| Identifer | oai:union.ndltd.org:TW/083YZU00489008 |
| Creators | W. L. Fu, 傅文龍 |
| Contributors | C. T. Chang, 張昌財 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 88 |
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