Convective-radiative heat transfer in the thermal entrance region of the semicircular duct with streamwise internal fins

Zhang, H.Y.; Ebadian, M. A.

doi:10.1016/0017-9310(91)90082-p

Cited by 12 publications

(4 citation statements)

References 21 publications

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“…Fluid flow around a semicircular tube had been carried out by many researchers [22][23][24][25][26][27]. is geometry is of particular interest for chemical and food processing industries, heat pipe designs, solar energy applications, and the design of heat exchangers.…”

Section: Introductionmentioning

confidence: 99%

Analytical Investigation into Effects of Capillary Force on Condensate Film Flowing over Horizontal Semicircular Tube in Porous Medium

Chang

Shiue

Ciou

et al. 2021

Mathematical Problems in Engineering

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A theoretical investigation is performed into the problem of laminar filmwise condensation flow over a horizontal semicircular tube embedded in a porous medium and subject to capillary forces. The effects of the capillary force and gravity force on the condensation heat transfer performance are analyzed using an energy balance approach method. For analytical convenience, several dimensionless parameters are introduced, including the Jakob number Ja, Rayleigh number Ra, and capillary force parameter Boc. The resulting dimensionless governing equation is solved using the numerical shooting method to determine the effect of capillary forces on the condensate thickness. A capillary suction velocity can be obtained mathematically in the calculation process and indicates whether the gravity force is greater than the capillary force. It is shown that if the capillary force is greater than the condensate gravity force, the liquid condensate will be sucked into the two-phase zone. Under this condition, the condensate film thickness reduces and the heat transfer performance is correspondingly improved. Without considering the capillary force effects, the mean Nusselt number is also obtained in the present study as N u ¯ | V 2 ∗ = 0 = 2 R a D a / J a 1 / 2 ∫ 0 π 1 + cos θ 1 / 2 d θ .

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Section: Introductionmentioning

confidence: 99%

Analytical Investigation into Effects of Capillary Force on Condensate Film Flowing over Horizontal Semicircular Tube in Porous Medium

Chang

Shiue

Ciou

et al. 2021

Mathematical Problems in Engineering

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“…This kind of study is useful in understanding solidification and therefore, the related hydrodynamic stability has attracted many researchers' interest (Hwang and Choi 2004;Mackie et al 1999;Karcher and Müller 1995;Zhang and Nguyen 1999;Zhang et al 1991;Beckermann and Viskanta 1988;Weaver and Viskanta 1986;Boger and Westwater 1967). The convective motion driven by buoyancy forces in the presence of solid components plays an important role in industrial applications, such as manufacturing of composite materials and purification of metals, as well as in a wide range of systems in nature, such as seasonal freezing and melting of soil, lakes, and rivers, artificial freezing of the ground as a construction technique for supporting poor soils, insulation of underground buildings, thermal energy storage in porous media, and storage of frozen foods.…”

Section: Introductionmentioning

confidence: 99%

Onset of Buoyancy-driven Instability in Porous Medium Solidified from Above

2008

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When a porous melt layer saturated by liquid is solidified from above, convection often sets in due to buoyancy forces. In this study, the onset of buoyancy-driven convection during time-dependent solidification is investigated by using the similarly transformed disturbance equations. The thermal disturbance distribution of the solid phase is approximated by the WKB method and effects of various parameters on the stability condition of the melt phase are analyzed theoretically. For the limiting case of λ → 0 and finite k r , the critical conditions approach asymptotically Ra * D,c = 25.89 and a * c = 1.80. This study presenting a constant-temperature cooling model predicts greater instability and gives more unstable results than those obtained from the constant solidification rate model.

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“…The variations of surface and mean temperatures, local heat transfer coefficient, local Nusselt number, and local friction factor with the axial dimensionless distance along the duct were presented in this study. Zhang and Ebadian [8] analyzed numerically the steady laminar forced convection and radiation heat transfer for the flow of an absorbing, emitting, gray, non-scattering gas in the entrance region of an internally finned semi-circular cross-sectioned duct. Hong and Bergles [6] studied the thermally developing process in the entrance region of semi-circular cross-sectioned ducts with uniform heat flux.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional numerical investigation of turbulent flow and heat transfer inside a horizontal semi-circular cross-sectioned duct

Arslan

2014

THERM SCI

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In this study, steady-state turbulent forced flow and heat transfer in a horizontal smooth semi-circular cross-sectioned duct was numerically investigated. The study was carried out in the turbulent flow condition where Reynolds numbers range from 1·10 4 to 5.5·10 4 . Flow is hydrodynamically and thermally developing (simultaneously developing flow) under uniform surface heat flux with uniform peripheral wall heat flux (H2) boundary condition on the duct's wall. A commercial CFD program, ANSYS Fluent 12.1, with different turbulent models was used to carry out the numerical study. Different suitable turbulence models for fully turbulent flow (k-e Standard, k-e Realizable, k-e RNG, k-w Standard, and k-w SST) were used in this study. The results have shown that as the Reynolds number increases Nusselt number increases but Darcy friction factor decreases. Based on the present numerical solutions, new engineering correlations were presented for the average Nusselt number and average Darcy friction factor. The numerical results for different turbulence models were compared with each other and similar experimental investigations carried out in the literature. It is obtained that, k-e Standard, k-e Realizable, and k-e RNG turbulence models are the most suitable turbulence models for this investigation. Isovel contours of velocity magnitude and temperature distribution for different Reynolds numbers, turbulence models and axial stations in the duct were presented graphically. Also, local heat transfer coefficient and local Darcy friction factor as function of dimensionless position along the duct were obtained in this investigation.

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Convective-radiative heat transfer in the thermal entrance region of the semicircular duct with streamwise internal fins

Cited by 12 publications

References 21 publications

Analytical Investigation into Effects of Capillary Force on Condensate Film Flowing over Horizontal Semicircular Tube in Porous Medium

Analytical Investigation into Effects of Capillary Force on Condensate Film Flowing over Horizontal Semicircular Tube in Porous Medium

Onset of Buoyancy-driven Instability in Porous Medium Solidified from Above

Three-dimensional numerical investigation of turbulent flow and heat transfer inside a horizontal semi-circular cross-sectioned duct

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