Experimental study on flow boiling heat transfer in rigid-tail rib-channel under rolling motion conditions

This study proposes a novel addition of rigid filamentous tail structure at the trailing edge of the ribs to enhance the heat transfer performance of flow boiling in mini-channel under rolling conditions. The flow boiling heat transfer characteristics of Novec649 in both rib-channel and rigid-tail rib-channel are experimentally investigated. Heat flux, inlet flow velocity, rolling angle and rolling period are considered as the variable parameters, which are 50 – 300 kW·m⁻², 0.3 – 0.9 m·s⁻¹, 0 – 15°, 10 – 20 s, respectively. The experimental results show that the rigid-tail structure improves the heat transfer performance of the channels within the entire range of thermal parameters, while increasing the pressure drop at high heat flux and/or high velocity. Compared with rib-channel, the rigid-tail structure exhibits the strongest enhancement in flow boiling heat transfer performance under high heat flux of q_eff = 300 kW·m⁻² and high flow velocity of v_in = 0.9 m·s⁻¹, and the heat transfer coefficient can be increased by 6.93 % at most. And increasing the rolling angle or decreasing the rolling period will decrease the average wall temperature by a maximum of 1.94 °C and increase the heat transfer performance factor j by a maximum of 8 % at v_in = 0.3 m·s⁻¹, q_eff = 200 – 300 kW·m⁻² for the rigid-tail rib-channel. Furthermore, the addition of a rigid-tail structure helps maintain smaller bubble sizes and a more uniform distribution in the mainstream region of the two-phase flow.