A theoretical and experimental study of a small-scale barometric sealed flash evaporative desalination system using low grade thermal energy

• Single stage flash desalination system was designed utilizing low grade waste heat.
• Condenser reject warm water at temperature 7 °C more than ambient was utilized.
• Increase in reject seawater temperature and flow rate increases fresh water yield.
• Good agreement was observed between the experimental and theoretical values.

A barometric sealed flash evaporative desalination system was designed to ensure effective utilization of waste heat energy from a process plant. Unlike other conventional system, steam is not used in this desalination process. The plant was constructed in an existing thermal power plant, and experiments were carried out at various temperature differences between condenser reject and surface seawater at various flow rates. The operational and constructional parameters of the plant components were discussed and theoretical calculations for estimating the fresh water yield are presented. The influence of plant operating variables on fresh water generation using low grade thermal energy is experimentally studied. It is found that increase in the power plant condenser reject seawater temperature, feeding to the evaporator, influences the fresh water yield. Increased seawater flow rate to both the flash evaporator and the distillate condenser, decreased distillation plant saturation pressure lead to an increase in the fresh water generation. A maximum yield of 0.086 m3/h is obtained at 14.8 m3/h and 25 m3/h seawater flow rates to the evaporator and condenser respectively, for a flash evaporator system pressure of 49 mbar. The overall agreement between the measured and the theoretical calculations is of the order of 91–96%.