Dilute viscoelastic polymer solutions for dielectric heat transfer applications: A molecular dynamics study

The suitability of industrially significant synthetic oils with dispersed polymeric chains that can be used as dielectric coolants with enhanced heat transfer properties in single-phase immersion cooling for electric vehicle components is evaluated via molecular dynamics simulations (MD). The fluids investigated are a synthetic solvent poly-alpha-olefin (PAO-2) and a solution based on PAO-2 with a single olefin co-polymer (OCP) chain dissolved. The simulation model accurately predicts the experimental thermodynamic properties of PAO-2. The effect of the polymer chain on the structural behaviour of the solution and its relation with the rheological properties is predicted and analysed at various temperatures in the range of 293 K–373 K. It is found that polymer solution shows an average viscosity enhancement of 9.2% and thermal conductivity enhancement of 2% within the temperature range. These properties eventually influence the Weissenberg and Nusselt numbers that impact the heat transfer. Analysis of the hydrodynamic radius of PAO-2 molecules shows that OCP chemistry acts as a thickening agent in the solution. Addition of the polymer chain is also shown to accelerate the shear thinning process due to increase in storage and loss moduli. The terminal relaxation time of OCP decreases with temperature and shear rate. The work conclusively establishes the impact of molecular interactions of the weakly viscoelastic liquids on their macroscopic behaviour. The viscoelastic nature of the examined polymer solution can lead to vortex roll-up in constricted flows inducing heat transfer enhancement. This in turn supports its use in immersion cooling applications which is shown for the first time.