As the thermal runaway (TR) probably occurs in enclosed space, the fire of lithium ion batteries (LIBs) in such system may cause more severe hazards on surroundings. To acquire deep understanding about the characteristics and evolution of LIBs fire in top-confined space, a refined study has been conducted with a single 18650 lithium ion battery under a plate obstacle. The fire extension length includes three main stages, and correlation between the plate height and extension length is proposed. The radiant heat flux of fire balls during deflagration is measured. The results show that the maximum heat flux in top-confined space is about four times that of open space. At early TR, the thermal hazards are more severe as the temperature of flame reaches peak in this period as well as the increasing rate of the back surface temperature. The heat flux to the plate during deflagration has been calculated based on the one-dimensional conduction model, and is found increase with decreasing height for center region but little difference for farther region. The results are expected to provide useful insights into LIBs fire in enclosed system and valuable guidelines for safety design.
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