The Numerical Simulation On The Two-Phase Flow And Heat Transfer Characteristics In The Internally Heated Pool

In the medical isotope reactor (MIPR) to separate and purify the medical isotope 99Mo and 131I, the reactive heat is constantly generated in the process of reaction, associated with the production of fission gas. In order to control the average temperature (usually≤80℃) of the reactor to prevent the sample from volatilizing, the cooling system of the reactor need to be designed carefully.Based on the analysis of the principal theory of natural convection and two-phase flow, the three-dimensional physical and mathematical models on the natural convection and two-phase convective heat transfer in the fluid with internal heat source were proposed, which is located on the background of analog test of MIPR. The natural convection in the pool was calculated by using the Boussinesq assumption, and the turbulent flow was computed by employing the RNG k-εturbulent model. The physical properties of the fluid were treated as temperature dependent. The bubble motion was predicted with the Euler-Lagrange discrete model, and the interaction of gas phase with continuous phase was taken into account.In the project, the numerical simulation was first performed on the natural convective heat transfer of the vertical tube heat exchanger in the inner heated liquid, of which the operation conditions and boundary conditions were determined according to the analog prototype experiments. The numerically computed results of the tube heat exchanger were compared with the corresponding detected values, which showed well consistency with the measured values. Meanwhile the reason resulted in the deviations of the computed results and measured ones was analyzed in conjunction with the temperature and velocity distribution.On the basis of solution of the natural convection, the two phase convective heat transfer to the vertical tube in the inner heated liquid was solved numerically,in which the bubble flow rate or the bare tower velocity was determined according to the prototype test. The computed results of two phase heat transfer characteristics of the vertical tube in the inner heated liquid were compared measured ones. By employing the dimension analysis and comparability principles, the non-dimensional criterion function related to the two phase flow and heat transfer was deduced, and the corresponding empirical correlation was derived by drawing up the computed results. The two phase flow and heat transfer characteristics was compared with the single phase natural convection, the influences of the bare tower velocity and the internal heat source intensity on the two phase convection were analyzed, respectively.According to the rule of the equivalent heat flux on the tube wall same as that of vertical tube, the 3D physical and mathematical models of natural convection and two-phase convective heat transfer of horizontal annular circular tube in the inner heated liquid were proposed, and were numerically solved under different operation conditions and boundary conditions. The corresponding heat transfer empirical correlations were developed with the computed results. The turbulent two-phase convective heat transfer characteristics was compared with the laminar natural convective heat transfer of horizontal tube heat exchanger in the inner heated liquid pool, and the influence of gas flow rate and heat source intensity on the two phase convective heat transfer was analyzed.