Experimental study on the heat transfer enhancement in a rectangular channel with curved winglets

ABSTRACT

Effects of the curved winglet vortex generator inserts (CWVGs) on the forced convection heat transfer, friction factor, and performance evaluation criteria (PEC) interior flow were experimentally examined in this work. The CWVGs manufactured in CNC from aluminum 6061 material were used as the expanded finned surface with different attack angles (α) of 0°, 30°, and 60°. In the study, air was used as the fluid. The experiments were realized in the Reynolds number ranging from 6000 to 20000. The results showed that the CWVG insert in a rectangular channel ensured significantly higher Nusselt number than that of the channel without the insert through friction factor that was also increased. The Nusselt number and friction factor increased with the increase in the attack angle (α) of CWVG insert. The heat transfer enhancement by the CWVGs with attack angle of 0°, 30°, and 60° ensured higher than that of the plain tube in the range of 217.39–291.30%, 260.86–465.21%, and 278.26–476.08%, respectively. The friction factors in the inner rectangular channel produced by the CWVGs with attack angle of 0°, 30° and 60°, were about 8.93–10.33, 10.66–14.16, and 14.96–19.13 times above the plain tube, respectively. The performance evaluation criteria (PEC) for CWVGs with attack angle of 0°, 30°, and 60° were in the range of 1.22–1.78, 1.28–1.86, and 1.32–1.89, respectively.

ABSTRACT

KEYWORDS:

• Winglet
• heat transfer
• turbulent
• airflow
• rectangular channel

Highlights

• The effect of new design winglets (CWGs) on heat transfer and flow characteristics in the rectangular channel has been investigated.

• Heat transfer enhancement increased in the range 1.23–1.9 with the increase in the attack angle of winglets.

• Pressure drop increased with increasing attack angle of the winglets.

Nomenclature

Asurface area of heat transfer (m²)

CWVGscurved winglet vortex generator

D_hhydraulic diameter of duct (mm)

ffriction factor

hheat transfer coefficient (W/m²K)

Ielectric current (amp)

kthermal conductivity (W/mK)

Llength of test channel (mm)

NuNusselt number

PrPrandtl number

P_netnet electrical power

Δ Ppressure drop (Pa)

ReReynolds number

Qheat transfer rate (W)

q^ııheat flux (W/m²)

Ttemperature (K)

Vaverage velocity (m/s)

ΔVelectric voltage (volt)

Wwidth of channel (mm)

w_Runcertainty value