Forced Convection Heat Transfer and Temperature Fluctuations of Lithium under Transverse Magnetic Fields.

Abstract

The MHD effects on a heat transfer of liquid lithium flowing in an annular channel were studied, using a newly constructed comparatively large-scale lithium loop. The data on the heat transfer characteristics were arranged in N u-St diagrams where St=Ha 2 /Re. The diagrams indicate that N u decreases as St increases as a whole trend. However, singular peaks of N u were observed at about St=13, corresponding to the singular increments of temperature fluctuations, whereas the peaks occurred at St=1.5 in the previous experiment with a smaller channel. In considering a predominant MHD effect due to conductive wall duct, the current load factor K P for external circuit was taken into account. And Miyazaki number Mi=K P St, which means the effective electromagnetic interaction, was adopted in substitution for St and the heater pin diameter was taken as the characteristic length in place of the conventional hydraulic equivalent diameter.Thus, an appreciably good agreement was obtained concerning the peaks at Mi=0.13 in the previous and at Mi=0.14 in the present experiments. Generation of vortex series in the singular phenomena was suggested from both the periodicity of temperature fluctuations in their PSD analysis and the proportionality between peak frequency and mean flow velocity, resulting in a 32 mm interval length of series.

Influence of Induced Magnetic Field on Thermal MHD Flow

“…Simulations for liquid lithium with Pr ¼ 0.065 for Re ¼ 100 and 200 are made and plotted in Figure 9. The observation shows the non-monotonic behavior of mean Nusselt number Nm that agrees with the findings of Uda et al [21], where forced convective heat transfer results on lithium under the influence of magnetic field are presented. In the absence of the magnetic field that is, N ¼ 0 for Pr ¼ 0.73,…”

Thermo-structural analysis and design consideration of the replaceable backwall in IFMIF liquid lithium target

“…Since the former constraint is not acceptable due to high thermal stress, the latter constraint was used in this analysis. Temperatures of the target assembly and liquid Li were both 300°C, and the convection heat transfer coefficient between Li and the backwall was 34 kW/m 2 K, estimated as the minimum value from experimental results [7]. Emissivity of the backwall was 0.3.…”

“…Design requirements of the Li target system are: heat removal of 10 MW from the deuterium beams, production of a stable Li jet for production of intense neutron irradiation damage more than 20 dpa/year in the high flux test module, control of the impurity levels (T, 7 Be, C, O, N), assurance of safety with respect to the Li hazard and tritium release from the Li loop and achievement of system availability of more than 95% during plant lifetime [5]. Major specifications of the IFMIF Li target are summarized in Table 1.…”

Thermo-structural analysis of integrated back plate in IFMIF/EVEDA liquid lithium target

“…The surface with insulation was assumed to be an adiabatic boundary and the other surface was assumed to be a radiation boundary. Emissivity was 0.3 and ambient temperature was 50 • C. Temperature of liquid Li was 300 • C, and the convection heat transfer coefficient between Li and the back plate was 34 kW/m 2 K which was the minimum value estimated from experimental results [6]. In general, the heat transfer coefficient was a variable as a function of the flow conditions, but it was assumed to be a constant in this analysis.…”