Phase change materials (PCMs) are becoming increasingly popular in passive thermal management of electronics due to their high latent energies aiding to absorb the heat and keeping the device in safe temperature limits. However, the low thermal conductivity of PCMs mandates the use of thermal performance enhancers (TPEs) to better exploit the latent energy of PCM. As the PCMs absorb and release the latent energy isothermally, the melting and solidification rates of PCMs strongly depend on the difference between phase change and ambient temperatures. Therefore, varying the phase change temperature of PCM at constant ambient temperature has been taken as a fundamental strategy to further augment the thermal performance of PCM based heat sinks with TPEs.



Initial experiments have been performed to understand the melting dynamics of PCM through photographic visualization and liquid crystal thermography. Moreover, a numerical phase change model based on enthalpy porosity formulation is adapted with independent and in-house experimental validation, to numerically visualize and analyze the further insights on the melting process in the bulk of the PCM, which is challenging to investigate experimentally. Further experimental and numerical studies have been performed on PCM based heat sink with embedded and extended TPEs (i.e., fins and heat pipe) with different PCMs namely n-Eicosane, Docosane and Tetracosane having phase change temperatures of 36, 44 and 52 oC with identical other thermo physical properties. From the results, it is seen that, in case of heat sink with fins the PCM with the highest phase change temperature (i.e., Tetracosane) shows superiority in the charging time up to 68% over a low phase change temperature PCM (i.e., n-Eicosane) at lower heat inputs. However, with an increase in the heat input, the performance of all the PCMs is similar. In the discharging time, the PCM Tetracosane shows superiority up to 83% over n-Eicosane due to a large difference between phase change and ambient temperatures. In the case of heat sink with heat pipe too the Tetracosane shows superiority over n-Eicosane by up to 53% and 23% in terms of the charging and the discharging times respectively. In sum, the present study pushes the limits of thermal performance of PCM based heat sinks over existing strategies especially in augmenting the discharging time, without compromising on the charging time.