Experimental studies of turbulent pulsating flow and heat transfer in a serpentine channel with winglike turbulators

• Published in: International communications in heat and mass transfer 2022-02, Vol.131, p.105837, Article 105837
• Main Authors: Wang, Chun-Sheng, Chen, Chieh-Chu, Chang, Wei-Che, Liou, Tong-Miin
• Format: Article
• Language: English
• Subjects: Infrared thermography; PIV; Pulsating flow; Serpentine heat exchanger; Thermal-fluidic correlation; Winglike turbulator
• ISSN: 0735-1933; 1879-0178
• DOI: 10.1016/j.icheatmasstransfer.2021.105837

Particle Image Velocimetry and Infrared Thermography measurements are applied to explore the effect of quasi-triangular pulsatile flow inlet on active thermal-fluidic performance in a serpentine channel with innovative winglike turbulators. The novel turbulators are mounted in-line on two sidewalls of the channel with the attack angle (α), thickness to chord line ratio (t/C), and pitch to the channel hydraulic diameter ratio (Pi/DH) respectively fixed at 20°, 0.2, and 0.7. The Strouhal number (St) varies from 0 to 0.67 at a fixed Reynolds number (Re) of 10,000. Relative to the steady-state case (St = 0), the flow pulsation not only strengthens the Fujiwhara co-rotating vortices but also eliminates the corner vortex streams, leading to the overall Nusselt number (Nu¯/Nuo) enhancement by 13%. Moreover, both the Nu¯/Nuo and friction factor (f¯/fo) reveal the tilde-like trends with St, resulting in the highest Nu¯/Nuo of 5.2 and thermal performance factor of 1.39 at St = 0.67, which are higher than the previous best results for 10≤f¯/fo≤100 in the Nu¯/Nuo-f¯/fo diagram. Finally, by combing the present data with our previous steady state results, composite correlations of Nu¯/Nuo and f¯/fo versus Re, α, t/C, Pi/DH, and St are proposed. •Flow pulsation and winglike turbulators on heat transfer are firstly explored.•Fujiwhara vortices are enhanced by pulsatile flow and increase Nu¯/Nuo by 13%.•The highest TPF of 1.39 with Nu¯/Nuo of 5.2 is reported at St = 0.67.•wp'rms/Ub¯p¯ emerges as one of the major heat transfer mechanisms with R = 0.82.•Correlations of Nu¯/Nuo and f¯/fo versus Re, α, t/C, Pi/DH, and St are proposed.