Increasing Energy Efficiency of Central Cooling Systems with Engineered Nanofluids

Abstract

Buildings consume about 40% of the world’s energy consumption and of that, 65% is dedicated to cooling (or heating) systems. Central building cooling uses water as the main heat transfer medium. The nanoparticle fluid suspension exhibits thermal properties superior to water. The goal was to achieve the highest possible thermal properties with just the right amount of nanoparticles in a uniform and stable dispersion and suspension in water. This engineered nanofluid contains a uniform and stable suspension of graphene nanoparticles (GNP) in water. Using covalent functionalization, centrifugation and high-speed dispersion, the GNP remains in a stable suspension indefinitely. The nanofluid is applied to the closed loop of the chilled water system, where the heat transfer enhancement occurs at the fluid tubes within the evaporator and the tubing in the chilled water coils within the Air Handling Units(AHUs). The Proof of Concept (POC) completed in 2019 using laboratory-derived nanofluid resulted in energy saving that averaged at 32% compared with the baseline fluid (water). In 2022, a Scaled-Up mini plant produced GNP nanofluids in a commercial process environment, showing an average energy savings of 21%. These results were further verified and validated on small chilled water plants outside of the Scaled-Up plant with 25% and 29% average savings.