Experimental study on the heat transfer characteristics of a lead-bismuth/heat pipe heat exchange prototype for liquid metal matrix-based heat pipe-cooled microreactors

This study proposes an innovative reactor configuration termed the Liquid Metal Matrix-Based Heat Pipe-Cooled Reactor (LM-HPR). The design aims to address two primary challenges in advanced reactor systems: eliminating the additional solid-solid contact thermal resistance between solid matrix materials and high-temperature heat pipe (HTHP) surfaces, and concurrently mitigating the high-temperature dynamic corrosion issues commonly associated with lead‑bismuth fast reactors. The heat transfer performance of this novel configuration was investigated using a dedicated lead‑bismuth/heat pipe heat exchange prototype (LBE-HPHE Prototype). A specialized experimental platform was constructed to measure critical physical parameters of both the HTHPs and the Lead-Bismuth Eutectic (LBE), facilitating a detailed examination of the heat exchange dynamics between these two media. Initial tests conducted on potassium HTHPs successfully verified stable startup characteristics and excellent isothermal performance. A series of five steady-state experiments were performed under varying LBE temperature conditions. During the final testing phase, the HTHPs exhibited an average axial temperature gradient of 43.82 °C and demonstrated a heat extraction capacity of 2.42 kW from the LBE pool. The average equivalent thermal resistance of the HTHPs was calculated to be 0.0516 K·W⁻¹, indicating good overall heat transfer characteristics alongside their confirmed isothermal performance. The average temperature difference measured between the bottom and top layers of the LBE was 5.90 °C. Analysis revealed that as the LBE temperature increased, the interlayer temperature difference initially decreased before subsequently increasing, a trend attributed to the evolving performance characteristics of the HTHPs under different operational conditions. With increasing LBE temperature, the heat exchange process between the HTHPs and the LBE intensified significantly. The natural convection heat transfer coefficient exhibited a substantial enhancement, rising from 327.32 W/(m²·°C) to 8431.65 W/(m²·°C). This improvement corresponded with increased heat transfer efficiency of the HTHPs and stronger natural convection heat transfer between the LBE and the HTHPs. Consequently, the Nusselt ( Nu ) number increased, while the Rayleigh ( Ra ) number also showed a gradual rise accompanying the elevation in LBE temperature. These experimental outcomes validate the fundamental feasibility of the liquid metal matrix-based heat pipe-cooled microreactor concept, providing crucial empirical data to support its further development and potential deployment.