Details

Autor(en) / Beteiligte

• Hata, K.
• Shirai, Y.
• Masuzaki, S.
• Hamura, A.

Titel

Computational study of turbulent heat transfer for heating of water in a short vertical tube under velocities controlled

Ist Teil von

• Nuclear engineering and design, 2012-08, Vol.249, p.304-317

Ort / Verlag

Amsterdam: Elsevier B.V

Erscheinungsjahr

2012

Quelle

Elsevier ScienceDirect Journals

Beschreibungen/Notizen

• ► Measure systematically steady-state turbulent heat transfer coefficients. ► Use Pt pipe of a 6mm inner diameter under flow velocity ranging from 4 to 41m/s. ► Solve numerically turbulent heat transfer. ► Numerical solutions are in good agreement with experimental data. ► Clarify thickness of thermal boundary layer in pipe. The steady-state turbulent heat transfer coefficients in a short vertical Platinum (Pt) test tube for the flow velocities (u=4.11–41.07m/s), the inlet liquid temperatures (Tin=296.47–310.04K), the inlet pressures (Pin=810.40–1044.21kPa) and the increasing heat inputs (Q0exp(t/τ), exponential periods, τ, of 6.04–23.66s) were systematically measured by an experimental water loop comprised of a multistage canned-type circulation pump with high pump head. Measurements were made on a 59.2mm effective length and its three sections (upper, mid and lower positions), which were spot-welded four potential taps on the outer surface of the Pt test tube of a 6mm inner diameter, a 69.6mm heated length and a 0.4mm thickness. Theoretical equations for turbulent heat transfer in a circular tube of a 6mm in diameter and a 636mm long were numerically solved for heating of water with heated section of a 6mm in diameter and a 70mm long by using PHOENICS code under the same condition as the experimental one considering the temperature dependence of thermo-physical properties concerned. The surface heat flux, q, and the average surface temperature, Ts,av, on the circular tube solved theoretically under the flow velocities, u, of 4.11–41.07m/s were compared with the corresponding experimental values on heat flux, q, versus the temperature difference between average inner surface temperature and liquid bulk mean temperature, ΔTL [=Ts,av−TL, TL=(Tin+Tout)/2], graph. The numerical solutions of q and ΔTL are almost in good agreement with the corresponding experimental values of q and ΔTL with the deviations less than ±10% for the range of ΔTL tested here. The numerical solutions of local surface temperature, (Ts)z, local average liquid temperature, (Tf,av)z, and local liquid pressure drop, ΔPz, are within ±10% of the corresponding experimental data on (Ts)z, (Tf,av)z and ΔPz. The thickness of the thermal boundary layer, δTBL [=(Δr)out/2], and the non-dimensional thickness of thermal boundary layer, yTBL+[=(fF/2)0.5(ρluδVSL/μl)], for the turbulent heat transfer in a short vertical tube under velocities controlled are clarified based on the numerical solutions. It was confirmed in this study that authors’ steady-state turbulent heat transfer correlation based on the experimental data (Hata and Noda, 2008) can not only describe the experimental data of steady-state turbulent heat transfer but also the numerical solutions within ±10% difference for the wide ranges of temperature differences between heater inner surface temperature and liquid bulk mean temperature (ΔTL=5–200K) and flow velocities (u=4.01–41.07m/s).