Enhancing the thermal performance of nanoslurries through tailored shell composition and solid loading

Pumpable nanoencapsulated phase change slurries (NPCS) with thermal energy storage (TES) capacities exceeding that of water are attracting increasing interest due to their potential to reduce heat exchanger equipment size, thermal fluid flow rate or the temperature gap. The influence of shell composition and initiator type on core content and encapsulation efficiency cannot be predicted a priori. In this work, the shell monomer ratio (styrene/divinylbenzene, S/DVB), the initiator type, and the solids content were systematically investigated to maximize the TES capacity of the NPCS. NPCS with solids content ranging from 27.4 to 45.0 wt% were produced, achieving TES capacities in the operating range 288.15–304.65 K of 0.024/0.024 to 0.029/0.027 kWh kg−1, respectively, for heating/cooling processes. Those values surpass those reported in literature. An S/DVB ratio of 75/25 combined with AIBN as initiator were identified as the optimal operating parameters. These conditions allowed to increase the solid content while keeping pumpability, yielding the s-S75~DVB25@RT2745. This formulation exhibited a TES capacity 1.5 times higher than that of water for the same temperature change and a viscosity of 193.0 ± 2.8 mPa·s (680 s−1, 298 K).