|Syaiful||- Department of Mechanical Engineering, Diponegoro University
|Astrid Ayutasari||- Department of Mechanical Engineering, Diponegoro University|
|Maria F. Soetanto||Aerospace Department of Polytechnic of Bandung|
|Ahmad Indra Siswantara||Mechanical Engineering Department of University of Indonesia|
|Myung-whan Bae||Engineering Research Institute, Department of Mechanical Engineering for Production,Gyeongsang National University|
The numerical simulation of heat transfer and pressure drop characteristics was carried out on the airflow through a rectangular channel-mounted vortex generator (VG). The VG was installed on a plate that was attached to the heater. The inlet velocity of the airflow varied from 0.4 to 2.0 m/s. The VGs used in this study were concave delta winglet pairs (CDWPs) with the attack angle of 30° and with variation in the number of rows: one pair, two pairs, and three pairs. The CDWPs are predicted to produce the longitudinal vortex (LV), which increases the intensity of turbulence resulting in better mixing of flow. This, in turn, can improve the heat transfer between the plate surface and the airflow in the rectangular channel. The results showed that the installation of CDWPs does improve the overall heat transfer performance. However, it has the consequences of a greater pressure drop. Based on the variation in the number of rows, the greater the number of pairs of VGs was the greater the convection heat transfer coefficient (h) in both laminar and turbulent flows. The h value was based on the number of row of CDWPs: one pair, two pairs, and three pairs exhibited increases of 65.9-108.4%; 34.4-71%; and 42.2-110.7% compared to the baseline, respectively. A great number of rows of VGs also led to an increasing pressure drop value in laminar and turbulent flows. The percentage increases in pressure drop for CDWPs with one pair, two pairs, and three pairs, as compared to the baseline, were 70.1-92.1%; 123.6-161.3%, and 180-266.9%, respectively.
Concave delta winglet; Convection coefficient of heat transfer; Longitudinal vortex; Pressure drop; Vortex generator
A numerical simulation and experiments evaluating thermal and hydrodynamic performances have been carried out. Good agreement between the numerical simulation and experimental results has been found. The LV generated by the CDWP VG was stronger and wider than that of the DWP VG, resulting in greater improvement of heat transfer. This was probably caused by the centrifugal instability manifested when the fluid flowed over the concave wall. Unfortunately, the advantage of using a CDWP VG in improving heat transfer was accompanied by a greater increase in pressure drop than that exhibited in the use of the DWP VG.
This work was supported by the Fundamental Research Project of Indonesia (KEMENRISTEK DIKTI Number 343-21/UN7.5.1/PP/2017). The authors are grateful to all research members, especially those of Lab. Thermofluid of Mechanical Engineering of Diponegoro University Indonesia, Aerospace Department of Polytechnic of Bandung Indonesia, Mechanical Engineering Department of University of Indonesia, and Advanced Combustion Lab. of Mechanical and Aerospace Engineering Faculty of Gyeongsang National University Korea.
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