Experimental study on the effect of feed water nozzles on non-equilibrium temperature difference and flash evaporation in a single-stage evaporator and an investigation of effect of process parameters on the liquid flashing in a LTTD desalination process

TLDR: In this article, the effect of geometry of the upward facing nozzles on flash evaporation rate and non-equilibrium temperature difference (NETD) of the flashing process was investigated.

Abstract: Low temperature thermal desalination (LTTD) process involves flash evaporation of a seawater at 28–29°C in a single-stage evaporator maintained at a vacuum of around 25–27 m bar (abs). The seawater was splashed inside an evaporator through a 0.1 m diameter upward facing nozzles of around 24 nos arranged evenly throughout the evaporator and generated vapour was condensed in the shell and tube condenser using cooling water available at 12–13°C sucked from the deep sea through a long HDPE pipe. The main objective of this study was to find out the effect of geometry of the upward facing nozzles on the flash evaporation rate as well as on the non-equilibrium temperature difference (NETD) of the flashing process. Two different spout nozzle geometries with 0.37–0.87 m height were used in the experiment. The study indicated that the flashing rate increased by 0.9% (average) and and the NETD (Two – Tsat) decreased by 0.7°C (average), respectively, when nozzle height was increased by 0.87 m. Mechanism that ...