Thermo-hydraulic characteristics of laminar flow in an enhanced tube with conical strip inserts

Abstract Our previous study has demonstrated that the conical strip inserts have a good thermo-hydraulic performance in the tubular turbulent flow regime. This paper investigates its thermo-hydraulic performance of laminar flow numerically. Effects of some geometrical parameters are studied. Computation results show that the average Nusselt number of enhanced tube is augmented by 3.70–5.51 times (average Nu = 16.15–24.05), while the average friction factor increases by 5.31–14.77 times (average f = 0.59–1.51) those of plain tube. The values of performance evaluation criterion (PEC) range between 1.17 and 2.97. Numerical results indicate that larger strip size (characterized by a geometry angle), smaller strip-wall gap and smaller strip pitch can effectively enhance the heat transfer rate, but also increase the flow resistance. The impact of slant angle depends on the magnitude of Reynolds number. Moreover, it is shown that the Nusselt number and friction factor are sensitive to the geometry angle, while the most sensitive factor of PEC value is the strip pitch. Relatively high PEC value is obtained at a parameter combination with small slant angle, strip-wall gap, strip pitch, and moderate geometry angle (α = 30°, δ/D = 0.10, s/D = 1.5, β = 60°) among all the investigated conditions.

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