Abstract
In this study 3-D numerical simulations on heat transfer and pressure drop characteristics for a typical louver fin-and- double-row tube heat exchanger were carried out. The heat transfer improvement and the corresponding pressure drop amounts were investigated depending on louver angles, fin pitch and Reynolds number, and reported in terms of Colburn j -factor and Fanning friction factor f . The heat transfer improvement and the corresponding pressure drop amounts were investigated depending on louver angles between 20° ≤Ө≤ 30°, louver pitch of Lp =3.8 mm and frontal velocities of U between 1.22 m/s - 3 m/s. In addition, flow visualization of detailed flow features results, such as velocity vectors, streamlines and temperature counters have been shown to understand heat transfer enhancement mechanism. The present results indicated that louver angle and fin pitch noticeably affected the thermal and hydraulic performance of heat exchanger. It has been seen that increasing louver angle, increases thermal performance while decreasing hydraulic performance associated to pressure drop for fin pitches of 3.2 mm and 2.5 mm. Fin pitch determines the flow behaviour that for fin pitch of 2 mm, increasing louver angle decreased heat transfer and pressure drop. Velocity vectors and streamlines give considerable information about the flow whether it is duct directed or louver directed. For all conditions the flow is louver directed.
Highlights
IntroductionThe air side of heat exchangers have much more thermal resistance. Decreasing attempts of air side thermal resistance play an important role to improve the performance of the heat exchangers
As it well known, the air side of heat exchangers have much more thermal resistance
The hydraulic and thermal performances of a louver fin heat exchanger depend on geometrical details and flow conditions
Summary
The air side of heat exchangers have much more thermal resistance. Decreasing attempts of air side thermal resistance play an important role to improve the performance of the heat exchangers. Researchers and engineers attempt to design more efficient louver fin heat exchangers studying various geometrical parameters experimentally and numerically In their experimental study, Aoki et al [1] concluded that heat transfer coefficients at low air velocity conditions decreased with increasing fin pitch while heat transfer coefficient reached a maximum value at angle of 28°-30°. Wang et al [3] conducted experiments using commercially available louver fin-and-tube heat exchangers They studied heat transfer and pressure drop characteristics depending on number of tube rows, fin pitch, and tube size. Dong et al [6] conducted an experimental study testing air side heat transfer and pressure drop characteristics of 20 types of multi-louvered fin and flat tube heat exchangers. Results are given in terms of Colburn j factor and Fanning factor f, temperature counters and stream-lines results
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