Investigation of shell-and-tube and plate heat exchangers as an evaporators with nanofluids

This study examines the thermal performance of shell-and-tube and plate heat exchangers operating as evaporators, utilizing aluminium oxide-water nanofluids at 0.1% and 0.2% volume concentrations. While nanofluids have been widely studied in heat exchanger applications, their effectiveness as secondary refrigerants under refrigeration conditions remains underexplored. To address this gap, an experimental evaluation was conducted on key performance parameters, including heat transfer rate, overall heat transfer coefficient, effectiveness, and coefficient of performance (COP). Additionally, numerical simulations were performed for the shell-and-tube heat exchanger to validate experimental findings. The results indicate that nanofluids significantly enhance heat exchanger performance compared to water. At a 0.2% concentration, the secondary fluid outlet temperature decreases by 9.8% and 12.5% in the shell-and-tube and plate heat exchangers, respectively, with a lesser effect at higher flow rates due to reduced residence time. The overall heat transfer coefficient increases by 33.5% and 60.2%, while the heat transfer rate improves by up to 32% and 56%. Additionally, effectiveness increases by 25.8% and 54.5%, and COP improves by 22.4% and 38.7%, with enhancements attributed to improved thermal conductivity and convective effects. These findings highlight the potential of nanofluids as efficient secondary refrigerants in refrigeration systems, offering enhanced heat transfer performance, reduced energy consumption, and improved cold chain efficiency.