Browsing by Author "Chimres, Nares"

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Effect of elliptical winglet on the air-side performance of fin-and-tube heat exchanger
(2018-08-01)
Chimres, Nares
;
Wang, Chi-Chuan
;
Wongwises, Somchai
;
機械工程學系
;
Department of Mechanical Engineering
This study numerically examines the elliptical winglets (EW) on the overall performance of fin-and-tube heat exchanger. The major geometrical parameters characterizing the EW has been investigated thoroughly, including the winglet location, attack angle and the trailing angle of the elliptical winglets with two different winglet lengths which are 1.0 mm and 1.5 mm. The numerical results indicate that the elliptical winglets with the 30 degrees attack angle, 0 mm horizontal distance, 6 mm vertical distance and 120 degrees trailing angle of both winglet lengths shows the highest performance. The heat transfer coefficients and pressure drops obtained by both winglet sizes are larger than that of the plain fin by about 13% and 35%, respectively. In term of the performance efficiency index, the 1.5 mm winglet length indicates about 1.8-2.9% improvement relative to plain fin geometry and the efficiency index of 1.0 mm winglet length is comparable with that of the plain fin. (C) 2018 Elsevier Ltd. All rights reserved.
Optimal design of the semi-dimple vortex generator in the fin and tube heat exchanger
(2018-05-01)
Chimres, Nares
;
Wang, Chi-Chuan
;
Wongwises, Somchai
;
機械工程學系
;
Department of Mechanical Engineering
The fin and tube heat exchanger with a semi-dimple pair is numerically studied in terms of the air side's thermal performance. The investigated parameters consist of the diameter, attack angle and the placed location of the semi-dimple. The results show that the 30 attack angle, 5.5 mm vertical distance and 7.5 mm horizontal distance can perform the highest j/f ratio or "goodness parameter" of every semi-dimple's diameter. Additionally, the thermal performance of the fin with a semi-dimple pair is also compared with that of the fin with existing semi-dimples and the plain fin within the Reynolds number ranging from 813 to 4019. Obviously, the existing semi-dimple exhibits the highest heat transfer coefficient and pressure drop. However, the semi-dimples' pair demonstrates a goodness factor of 33-37% greater than the existing semi-dimples and 15-20% greater than the plain fin, approximately. (C) 2017 Published by Elsevier Ltd.