Passive, internal thermal management system for batteries using microscale liquid-vapor phase change

Conventional thermal management systems for lithium-ion batteries remove heat from the exterior surface of the battery, causing undesirable temperature increase and thermal gradients inside the battery. Internally cooling batteries can reduce both of these effects, improving safety and durability. In the present study, a novel internal cooling system that utilizes passive, liquid-vapor phase change processes is investigated using representative geometry and a surrogate heat source. Frictional and heat transfer characteristics of the representative cooling system with buoyancy driven flow are reported over a range of net heat inputs (94-6230 W L−1) and saturation temperatures (24 °C-33 °C). The results show that the mass flow rate increased to a maximum near a heat input of 1350 W L−1, and there was a slight influence of saturation temperature on the performance of the system. In addition, the calculated two-phase frictional pressure drops in the microchannel evaporator (3.175 mm × 160 μm channels) are compared to the representative correlation database (Dh < 1 mm) and used to develop a new frictional pressure drop model with improved accuracy over the tested mass flux range (45 < G < 112 kg m−2 s−1). The results presented here are utilized in a subsequent investigation to determine the performance improvement in large lithium-ion battery packs intended for electric and hybrid electric vehicular applications through internal cooling.