Enhancement of PCM materials using metal fins in a battery thermal management system

It is clear that the world of transport is dominated by oil: today 55% of global demand for oil comes from the transport sector as a whole, the trend will increase over the years (60% in 2040). The increasingly critical scenario of pollutant emissions calls for the use of alternative propulsion sources. These include the use of hybrid propulsion vehicles (hevs) whose operating principle is based on batteries of various types, including lithium-ion batteries. The optimal operation of the batteries is obtained when they work in a temperature range ranging from 15 ºC to 35 ºC. Working with temperature values in the range of 0 ºC, the main effect is the loss of energy and power. On the other hand, excessively high temperatures can lead to catastrophic phenomena such as the Thermal Runaway. The need to limit the temperature gradient of the battery to less than 5 ºC should not be overlooked. Because of this, it is useful to implement an effective battery body cooling system (BTMS). In this case study a lithium-ion battery with "Pouch" structure and chemical composition of the NMC cathode is analyzed. For temperature control, a passive system is used, which uses the latent heat of material phase change to obtain battery cooling (LHTES) as a useful effect. The first step of the study consists in the simulation, through the software ANSYS FLUENT, of the thermal behavior of the cell in order to obtain a temperature trend of the numerical model similar to that obtained by experimentation. The cooling system of the cell consists in the coating of the latter with phase change material (PCM), in particular n-Octadecane (paraffin) was chosen because of its thermophysical properties and the convenient market price. Octadecane has high latent heat values (about 225 kJ/kg) at the expense of thermal conductivity values of the order of 0.385 W/mk. To overcome this problem, a system of increasing the performance of the PCM is adopted: PCM-Fin Structure. The second step, therefore, concerns the study of the thermal behavior of the battery subject first to a layer of pure PCM and, later, to a layer of PCM-Fin Structure. Having analysed the effects of cooling on the single cell, the analysis involves the study of the thermal behavior of a battery pack with 1P3S configuration. The last part of the work consists in the variation of geometric parameters such as thickness of the PCM, thickness and spacing of the fins in the battery pack in order to verify how the variation of these leads to a consequent variation of the thermal behavior of the entire package.