Thermal-hydraulic Optimal Design And Study Of Primary Heat Exchanger For Lead Alloy Cooled Natural Circulation Reactor

Natural circulation lead alloy cooled reactor is an important developing and designing direction of the fourth advanced reactors with high performance in neutronics, thermal hydraulics and security features. The primary heat exchanger (PHX) is a key heat transmission equipment of the lead alloy cooled reactor, and it is also a safety barrier to prevent the radioactive lead alloy coolant. Via the review of all kinds of PHX for lead alloy cooled reactor at home and abroad, a design of PHX for lead alloy cooled natural circulation reactor was proposed. Meanwhile, the capability of the PHX was evaluated and thermal hydraulic optimized.The schematic design of PHX for lead alloy cooled natural circulation reactor in this work was fully taken consider in the feasibility, reliable and economy. And in combination with the theoretical calculation and analysis, the tube and shell structure scheme of double-walled-straight-tube was put forward. In the reactor, there are four PHX arranged symmetrically, and each PHX was composed of tube bundle, pressure chamber, discharge chamber, declining center tube, shell and shielding component.The thermal contact resistance between inner and outer tube of the double-walled-straight-tube will dramatically influence the performance of PHX. The impact of total temperature difference at the interface, tube materials, surface roughness and the machining tolerance on thermal contact resistance and on total heat transfer property were analyzed with utilizing two concentric cylinder layers model, and finally got an influence law of these effects. The results showed:the lower thermal contact resistance but higher total heat transfer coefficient is obtained when316L stainless is used for steel tube, the machining tolerance degree is IT6, and the surface asperity Ra belongs to0.012～6.3μm.Finally, the main heat exchanger was make a thermal-hydraulic design. The influence of tube length, tube outer diameter, wall thickness and tube spacing on PHX performance was discussed. JF factor was adopted to evaluate the comprehensive performance of the PHX, and CR was used to study the influence degree of above effects. At last, the optimal structure of tube bundle was obtained. Made construction cost into consideration, CER was used to evaluate the overall performance of the PHX.