The Mechanical Analysis of an All-Glass Solar Evacuated Tube With Spiral Inner Tube for Seawater Desalination

Abstract

Solar desalination is an important way to obtain fresh water. Nowadays, the all-glass evacuated tube with only one open end (blind pipe) is widely used in hot-water system, and the glass-metal evacuated tube is commonly used in solar trough concentrating system in medium temperature area. But both of them have drawbacks for seawater desalination. The former cannot quickly heat seawater to 100 °C, and the latter is expensive and fails to make full use of its high temperature advantage. A new design of a medium-temperature full-glass evacuated tube whose inner tube is wound by a spiral structure is proposed in to achieve a more cost-effective solar trough concentrating system for solar desalination. The sealing stress between inner and outer tube is analyzed and the thermal performance is tested. The results showed that the evacuated tube could withstand temperature of 250 °C, quickly heat seawater, and has good corrosion resistance and can keep a long-term vacuum. Such a tube enables seawater to flow directly without oil heat-exchange system, so it is a more promising solution for seawater desalination.