Nanofluids for enhanced performance of building thermal energy systems

Energy consumption in the building sector can be potentially reduced by enhancing the heat transfer performance of building energy systems (BES). But low thermal conductivity and low heat transfer coefficient of the working fluids hinder the effectiveness of heat exchangers in the BES with limited heat transfer areas. An innovative way to enhance the effectiveness of heat exchangers without modifying the design is by suspending nanoparticles in the working fluid. Nanofluids’ applications in photovoltaic thermal and thermal energy storage systems are quite conventional but the involvement of compression and phase change processes in refrigerant-based systems are considered sensitive. Recently many advances have been reported in the nanofluids (mixture of nanoparticles and base fluid) field such as the preparation of nanorefrigerants that have enabled better usage of nanofluids in the BES. Available experimental studies have proved nanofluid as an effective measure to enhance the effectiveness of BES, though several practical hurdles still exist. This chapter reviews the experimental and theoretical studies related to nanofluid applications in building energy systems, including photovoltaic thermal systems, HVAC systems, and thermal energy storage systems. A comprehensive review of the available studies has been provided. Moreover, methods of nanoparticle suspension, widely used nanofluids, and limitations associated with nanofluids usage in BES are also discussed.