Enhancement of heat transfer coefficient of water desalination in multi-stage flushing using hematite nanofluid

Abstract

This study is the first step toward the enhancement of the evaporation amount and heat transfer coefficient (HTC) in multi-stage flushing (MSF) desalination processes by incorporating hematite nanoparticles (Fe2O3 NPs) into saltwater. The study involved the application of a laboratory experiment aimed at determining various physical properties of saline water (SW) nanofluid (NF). These properties included stability, thermal conductivity (TC), evaporation volume and rate, boiling temperature (BT) and time, and local HTC in stagnant conditions. The investigation took into consideration the impact of salinity, NPs (with regard to both size and volume fraction (φ)), and pressure. The utilization of stable SW NF resulted in reduced BT and expedited boiling. In the actual MSF process, the preheating of the cooling SW occurs rapidly and at low temperatures prior to its arrival at the brine heater. The determined decline in usage of steam was 2 % in the least favorable scenario. Meanwhile, the measurement of the amount of evaporation was conducted by evaluating the condensation content under ideal circumstances, which indicated a 15 % increase under atmospheric pressure and a rise of 25 % under vacuum circumstances. A significant enhancement of the local HTC, reaching to 134 %, was observed under stagnant conditions when utilizing NPs with a size of 20 nm and φ of 0.05 %. This denotes the initial stage in the estimation of the augmentation in output of water through the utilization of SW NF. The deposition of Fe2O3 NPs with high thermal conductivity is expected to have a significant impact on the mitigating surface thermal resistance caused by inorganic scale in MSF plants.