There are mainly two types. One is that there is no water inside the tube. , One is the water in the tube. The traditional vacuum tube is the water in the tube. The introduction of the double vacuum and the introduction of the "heat pipe in-line" vacuum tube make the glass tube no water.
As the heart of solar water heaters, vacuum tubes will continue to change with changes in the environment, because regional differences, differences in target consumer groups, and differences in buildings require solar water heaters to adapt to local conditions and to effectively integrate with buildings.
