Polymeric hollow fibers: a modular heat exchanger for thermal management systems of battery modules in electric vehicles

Abstract

The liquid-cooling system based on polymeric hollow fibers (1 mm) embedded inside durable polydicyclopentadiene is proposed for thermal management of li-ion cylindrical batteries from their surface. In the present work, a dramatically improved design is presented, eliminating the following drawbacks: I) the thermal resistance of the heat exchanger is minimized by bringing fibers into direct contact with the negative terminal/cylindrical shell, II) the fabrication process (combination of extrusion and rapid injection molding) is significantly simplified and accelerated as the essential component of the heat exchanger is nearly planar, and III) inlet/outlet manifolds were refined to enhance modularization of the cooling system of the whole battery pack. The pressure loss of the heat exchanger is favorably low, about 100 Pa, corresponding to 10 l/min of the coolant circulating in the entire battery pack of a virtual electrical vehicle. The heat exchanger was stacked with 18650-type lithium-ion cells, which were repeatedly charged/discharged. With the coolant inlet temperature of 20 °C and the C-rate of 1 C, the maximum temperature of the cells during cycling was between 26 °C and 22 °C in the given range of flow rates (5–45 ml/min). Temperature spreads were 10 °C and 4 °C.The liquid-cooling system based on polymeric hollow fibers (1 mm) embedded inside durable polydicyclopentadiene is proposed for thermal management of li-ion cylindrical batteries from their surface. In the present work, a dramatically improved design is presented, eliminating the following drawbacks: I) the thermal resistance of the heat exchanger is minimized by bringing fibers into direct contact with the negative terminal/cylindrical shell, II) the fabrication process (combination of extrusion and rapid injection molding) is significantly simplified and accelerated as the essential component of the heat exchanger is nearly planar, and III) inlet/outlet manifolds were refined to enhance modularization of the cooling system of the whole battery pack. The pressure loss of the heat exchanger is favorably low, about 100 Pa, corresponding to 10 l/min of the coolant circulating in the entire battery pack of a virtual electrical vehicle. The heat exchanger was stacked with 18650-type lithium-ion cells, which were repeatedly charged/discharged. With the coolant inlet temperature of 20 °C and the C-rate of 1 C, the maximum temperature of the cells during cycling was between 26 °C and 22 °C in the given range of flow rates (5–45 ml/min). Temperature spreads were 10 °C and 4 °C.