On the solar receiver thermal enhancement by using the dimple combined with delta winglet vortex generator

• Published in: Applied thermal engineering Vol. 111; pp. 586 - 598
• Main Authors: Luo, Lei, Wen, Fengbo, Wang, Lei, Sundén, Bengt, Wang, Songtao
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 25.01.2017
• Subjects: Delta-winglet vortex generator; Dimples; Energiteknik; Energy Engineering; Engineering and Technology; Inline and staggered layout; Maskinteknik; Mechanical Engineering; Solar receiver; Teknik; Thermal enhancement; Solar receiver; Delta-winglet vortex generator; Dimples; Thermal enhancement; Inline and staggered layout
• ISSN: 1359-4311
• DOI: 10.1016/j.applthermaleng.2016.09.096

•A novel solar receiver heated channel is proposed.•Delta winglet vortex generator combined with dimples is used.•Heat transfer is augmented by flow impingement on the dimples.•Interactions between dimples and delta winglet vortex generator are analyzed.•Thermal performances are evaluated and compared. In this study, effects of dimples and their arrangement on the flow structure, heat transfer and friction factor in a solar receiver heated channel with delta-winglet vortex generators (DWVGs) are numerically studied. The dimples are placed either in an inline or a staggered layout. A smooth channel with pure dimples and a smooth channel with pure DWVGs are studied, in which the smooth channel with DWVGs is considered as baseline. The Reynolds number is ranging from 4000 to 40,000. Results of the flow structure, heat plate Nu number, friction factor, temperature and turbulent kinetic energy (TKE) are included. The results show that the adoption of dimples significantly impacts the flow structure by interacting with the vortex which is generated by the DWVGs. A small part of the vortex moves downward and impinges on the inline arranged dimpled surface, which is beneficial for the heat transfer enhancement. However, for the staggered arrangement of dimples, the vortex flow is lifted upward before it impinges on the dimple surface. In this case, the inline arrangement dimples provides the best mixing and the highest heat transfer performance. The heat transfer is augmented by 36.23% while the friction factor is increased by 36.29% compared to the Baseline, respectively. The thermal performance analysis indicates that the use of dimples increases the thermal performance by 28.50%. It is also found that the adoption of inline dimples contributes to the optimal thermal performance and mixing of the cold and hot fluid.