Turbulent Heat Transfer and Fluid Flow in an Unsymmetrically Heated Triangular Duct

Abstract

Experiments were performed to determine entrance-region and fully developed heat transfer characteristics for turbulent airflow in an unsymmetrically heated equilateral triangular duct; friction factors were also measured. Two of the walls were heated while the third was not directly heated. The resulting thermal boundary conditions consisted of uniform heating per unit axial length and circumferentially uniform temperature on the heated walls. Special techniques were employed to minimize extraneous heat losses, and numerical finite-difference solutions played an important role in both the design of the apparatus and in the data reduction. The thermal entrance lengths required to attain thermally developed conditions were found to increase markedly with the Reynolds number and were generally greater than those for conventional pipe flows—a behavior which can be attributed to the unsymmetric heating. The fully developed Nusselt numbers were compared with circular tube correlations from the literature, from which it was shown that the hydraulic diameter is not fully sufficient to rationalize the circular and noncircular duct results. However, excellent Nusselt number predictions were obtained by employing the Petukhov-Popou correlation in conjunction with the measured friction factors for the triangular duct. This approach may have general applicability for predicting noncircular duct heat transfer. The friction factor results also affirmed the inadequacies of the hydraulic diameter but supported a general noncircular duct correlation available in the literature.

Turbulent heat transfer enhancement in a triangular duct using delta‐winglet vortex generators

“…4(a). It should be noted that the friction factor correlations of Blasius [38], Petkhov and Popov [39], and Prandtl [40] are of a circular tube, whereas the correlations of Chegini et al [3] and Altemini and Sparrow [5] are of equilateral triangular ducts. The results of Refs.…”

“…Altemani and Sparrow [5] performed an experimental work in an equilateral triangular duct without VG. They have found that the hydraulic diameter is not sufficient to rationalize the difference Fig.…”

A Numerical Analysis on Nanofluid Mixed Convection in Triangular Cross-Sectioned Ducts Heated by a Uniform Heat Flux

“…In fact, triangular ducts ensure compactness cost effectiveness by means of low fabrication costs, relatively easy construction, and mechanical strength [11,12]. Forced convection was predominantly investigated both in laminar flow [13][14][15] and in turbulent one [16][17][18][19]. Furthermore, literature covers different fluids, like gas, liquid, non-Newtonian fluids, and, recently, nanofluids [14,20,21].…”

“…Furthermore, literature covers different fluids, like gas, liquid, non-Newtonian fluids, and, recently, nanofluids [14,20,21]. An experimental approach [4,17] or analytical [22] and numerical methods [21,23,24] have been adopted. Shah and London [25] performed a huge and exhaustive review about theoretical and experimental analyses on laminar forced convection and heat transfer in noncircular ducts.…”

Numerical Investigation on Mixed Convection in Triangular Cross-Section Ducts with Nanofluids

“…Investigations have been performed in mixed and forced convection, considering mainly the flow regime laminar and also turbulent ones [10][11][12][13][14][15] and recently also microchannel have been analyzed [16]. Experimental test [3,14] and analytical [17] and numerical methods [18,19] are available in the literature. The use of numerical methods is nowadays widely adopted calculator powers and scheme strongly improved.…”