Journal Article Conductive sublayer of turbulent heat transfer for heating of water in a circular tube

Hata, Koichi  ,  Fukuda, Katsuya  ,  Masuzaki, Suguru

53 ( 8 )  , pp.2559 - 2576 , 2017-08 , Springer Verlag
ISSN:0947741114321181
Description
The steady-state and transient turbulent heat transfer coefficients in circular platinum (Pt) test tubes (inner diameters: 3 and 6 mm; heated lengths: 66.5 and 100 mm and 69.6 mm, respectively) were systematically measured using an experimental water loop for a wide range of flow velocities, inlet liquid temperatures, Prandtl numbers, inlet pressures, and exponentially increasing heat inputs (Q (0) exp(t/tau), tau: exponential period). The Reynolds-averaged Navier-Stokes equations and the k-epsilon turbulence model for unsteady turbulent heat transfer in circular test sections were numerically solved for heating of water with heated sections of diameter 3 and 6 mm and length 67 and 100 mm and 70 mm, respectively, by using computational fluid dynamics code under the same conditions as those in the experiment and with temperature-dependent thermophysical fluid properties. The thickness of the conductive sublayer, delta (CSL,st) and delta (CSL) [=(Delta r) (out) /2], and the nondimensional thickness of the conductive sublayer, (y (CSL,st) (+) ) (TEM) [=(f (F) /2)(0.5) rho (l) u delta (CSL,st) /mu (l) ] and (y (CSL) (+) ) (TEM) [=(f (F) /2)(0.5) rho (l) u delta (CSL) /mu (l) ], for steady-state and transient turbulent heat transfer at various heated length-to-inner diameter ratios, inlet liquid temperatures, and exponential periods were measured on the basis of the numerical solutions. The correlations of the thickness of the conductive sublayer, delta (CSL,st) , and nondimensional thickness of the conductive sublayer, (y (CSL,st) (+) ) (TEM) , for steady-state turbulent heat transfer and those of the thickness of the conductive sublayer, delta (CSL) , and nondimensional thickness of the conductive sublayer, (y (CSL) (+) ) (TEM) , for transient turbulent heat transfer in a circular tube were derived.
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