A novel desalination system for utilizing waste heat contained in cooling salt water of a steam plant condenser

• Developing a system to utilize low temperature heat source.
• Utilizing sea water heat in condensers of steam power plants for desalination.
• Confirming fresh water production capability using optimum system.
• Methodology for predicting the performance of fresh water production capability.

A novel system for utilizing low temperature heat contained in cooling sea water of a steam power plant condenser for desalination is proposed in this work. This system enables warm saline water, leaving the condenser of a steam power plant to flow through a barometer tube to a tight evaporator under vacuum where some water vapor is flashed. The produced water vapor flows to the tip of an inverted U-pipe through an entraining tube connected to the U-pipe due to the pressure difference. The required vacuum is produced by allowing fresh water to flow through the U-tube by immersing each of its two branch terminals in a holding tank full of fresh water. The water levels in the two tanks are at different heights. The brine remained in the evaporator is drained through a drainage barometric tube connecting the evaporator to a brine holding tank. The results of an analytical fluid flow and thermodynamics for predicting the proposed system performance led to infer that relatively high value of producing fresh water rate can be achieved by selecting the appropriate dimensions of the proposed system. For obtaining reasonably high produced fresh water rate (1.5–10.0 kg/h) at reasonably low specific energy consumption (1.0–8.0 kWh/kg) the inner diameters of the U-pipe and entraining tube are selected equal in the range 0.08–0.15 m, and the diameters of the suction and drainage tubes are selected in the range 0.04–0.08 m. Higher values of the produced fresh water rates can be achieved with selected diameters of suction and drainage tubes in the range 0.1–0.16 m, so that any disturbances of water flow through the greater inner diameters of both the U-pipe and entraining tube are obviated, but at greater specific energy expenditure. The height difference of the two fresh water holding tanks is selected in the range of 0.1–0.16 m, so that any disturbances of water flow through the U-pipe are avoided and the specific energy consumption is kept reasonably low. Right choice of the suction and drainage tube heights enables suction and draining the required rate of seawater. They lie roughly 10.1 m depending on their inner diameters.