Enhanced single-phase heat transfer performance via vortex secondary flow in hypervapotron configuration

Abstract

As the hypervapotron (HV) heat sink is used to cool many areas inside the fusion tokamak, it is essential to understand its heat transfer performance to calculate the thermal efficiency of the power generation system. Therefore, in this study, the single-phase (SP) heat transfer performance of HV heat sink was evaluated through sub-cooled flow boiling experiments under one-side high-heat load conditions. When vapor is generated inside the heat sink, flow instability and a potential risk of reaching the critical heat flux are created. Therefore, in commercial power plants, cooling systems tend to operate in the SP regime. System parameters that can be adjusted in the power generation system include the system pressure, mass flow rate, and subcooling, and the effect of these three parameters on the heat transfer performance in the SP regime was analyzed. It was experimentally observed that the mass flow rate was the most influential variable. The prediction performance of the SP forced convection heat transfer correlations of the existing conventiaonl channel were evaluated. The results revealed that they tended to under-predict the heat transfer performance of the HV heat sink. In addition, the same trends were found when the forced convection heat transfer correlation of the curved channel was evaluated. The reasons for the former and the latter are that the heat transfer enhancement effect by the vortex flow occurring between the fins of the HV heat sink is not reflected in the correlations, and the vortex effect of the HV heat sink is not expressed as a variable. Therefore, a new vortex forced convection heat transfer correlation was developed through the newly defined Dean number of the HV heat sink. The developed correlation recorded an average error rate of 0.48%.

Study on onset of nucleate boiling with screw tube for fusion reactor application

“…The two new correlations were evaluated for prediction performance by applying the AE, MAE, and RMSE metrics using the approaches in equations ( 4)- (6). Figures 20 and 21 show the prediction performance evaluation results for the ONB boiling number and superheating correlations, respectively.…”

“…It is also necessary to carefully consider the design and operational strategy of the plant cooling system. The primary wall of a tokamak, or blanket, is loaded with heat fluxes of up to 7 MW m −2 [5] and the inner/outer vertical targets of the divertor are loaded with heat fluxes of up to 20 MW m −2 [6]. Figure 1 shows a schematic of a tokamak diverter cooling system.…”