An investigation on heat transfer performance of polystyrene encapsulated n-octadecane based nanofluid in square channel

Highlights: • Synthesis of polystyrene encapsulated phase change material by mini emulsion polymerization method. • Dispersion of nanoencapsulated PCM in deionized water. • No significant change in thermo physical properties of PCM based nanofluid. • 37% improvement in heat transfer performance for PCM based nanofluid as compared to deionized water. • 17% enhancement in pumping power for PCM based nanofluid as compared to deionized water. -- Abstract: The phase change material based nanofluids (PCM nanofluids) is a promising heat transfer fluid for various applications including electronics cooling and thermal power plants. The present work focusses on the study of heat transfer performance of polystyrene encapsulated phase change material (nanoPCM) based nanofluid. The nanoPCM was synthesized by mini-emulsion polymerization in which PCM core (n-octadecane) is encapsulated within polystyrene shell. The nanoPCM was characterized by Scanning Electron Microscope (SEM), Particle Size Analyser (PSA), Differential Scanning Calorimetry (DSC) and Fourier Transform Infrared (FTIR) spectroscopy. The PCM nanofluid was prepared by dispersing nanoPCM in deionized water and the thermo-physical properties of the nanofluid were estimated. The optimum concentration of PCM nanofluid for maximum stability was fixed as 0.7% v/v, based on zeta potential measurements. The heat transfer and pressure drop studies of PCM nanofluid were conducted in a square channel of 8 mm hydraulic diameter. The PCM nanofluid shows up to 37% improvement in heat transfer performance as compared to deionized water (DI water). The enhancement in heat transfer coefficient of PCM nanofluid is attributed to the improved heat capacity of nanoPCM and latent heat absorption during its melting. The results reveal that heat flux and flow rate of PCM nanofluid plays a crucial role in heat transfer performance. A slight increase in pressure drop and the pumping power was observed for the PCM nanofluid as compared to deionized water, especially at higher mass flow rates due to the increase in the viscosity of PCM nanofluid.