Heat transfer experiments and correlations for vent gases emerging from a Li-ion battery and impinging on a flat surface

Abstract

During thermal runaway of Li-ion battery cells, high-temperature gas jets may impinge onto nearby surfaces and may increase the risk of a propagating failure. In this paper, heat transfer rates of jets emerging from a cylindrical Li-ion cell and impinging on a flat surface were measured experimentally and empirical correlations were developed based on the resulting data. Experiments used compressed air as the working fluid, which issued from the isolated safety vent and impinged on a target plate. Infrared thermography was used to obtain the spatially-resolved, convective heat transfer distribution on the target plate. While heat transfer distributions showed local maxima at the site of jet impingement, complex geometric features within the vent resulted in variation in the convection rate when comparing the multiple impinging jets emerging from a single Li-ion cell. Heat transfer correlations were developed in the form of Nusselt number as a function of Reynolds number and may be used in thermal runaway models which seek to include the effects of venting and combustion as an alternative to resolving the impingement heat transfer rates with expensive 3-D computational fluid dynamics simulations.