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In this paper, a new technique is presented for structural acoustic analysis in the case of nonconforming acoustic–solid interface meshes. We first describe a simple method for coupling nonconforming acoustic–acoustic meshes, and then show that a similar approach, together with the coupling operators from conforming analysis, can also be applied to nonconforming structural acoustics. In the case of acoustic–acoustic interfaces, the continuity of acoustic pressure is enforced with a set of linear constraint equations. For structural acoustic interfaces, the same set of linear constraints is used, in conjunction with the weak formulation and the coupling operators that are commonly used in conforming structural acoustics. The constraint equations are subsequently eliminated using a static condensation procedure. We show that our method is equally applicable to time domain, frequency domain, and coupled eigenvalue analysis for structural acoustics. Numerical examples in both the time and frequency domains are presented to verify the methods.

In this study, wet surface j and f factors were obtained for spiral fin-and-tube heat exchangers. Nine samples having different fin pitches (2.12, 2.54 and 3.18 mm) and different tube rows (1, 2 and 3 row) were tested. Data are compared with those of the dry surface. For the wet surface, the effect of fin pitch on j factor is not significant. However, f factor decreases as the number of tube row increases. The j factor increases as the number of tube row increases. Different from the j factor, f factor decreases as the number of tube row increases. At one row configuration, the dry surface j factor is larger than that of the wet surface one. As the number of tube row increases, the trend is gradually reversed. Possible reasoning is provided considering the condensate behavior under wet condition. A new j and f factor correlation is developed, which predicts j and f factors within ± 20% and ± 30%, respectively.

In this study, wet surface pressure drop and heat transfer characteristics of plain finned heat exchangers having 5.0 mm diameter (5.3 mm after tube expansion) tubes were investigated. Nine samples having different fin pitches (1.1 to 1.3 mm) and tube rows (1 to 3 rows) were tested. The fin pitch had a negligible effect on j and f factors. Both j and f factors decreased as the number of tube row increased. When compared the j and f factors of the samples having 5.3 mm diameter tubes with those of 7.3 mm diameter tubes, 5.3 mm samples yielded higher j factors and lower f factors. The j/f ratios of 5.3 mm samples are larger than those of 7.3 mm samples which implies that 5.3 mm geometry is more beneficial than 7.3 mm geometry.