A vacuum heating tube is a device that utilizes a vacuum environment to achieve efficient heating, primarily categorized into two types:

Electronic Component Vacuum Tubes

Refers to the vacuum tubes (electron tubes) used in early electronic devices, which heat the cathode to release electrons and use the grid to regulate electron flow for signal amplification or switching control. Their structure includes a cathode, grid, and anode, and they were once widely used in fields such as radio communication and computing but have been largely replaced by solid-state devices.
Vacuum Tubes for Solar Thermal Collectors
Primarily used in solar water heaters, these employ a double-layer glass tube structure: the outer tube is made of high-borosilicate glass (light transmittance 92-99%), while the inner tube is made of metal or glass, with the interlayer evacuated and coated with a selective absorption layer. Key advantages include:
The vacuum interlayer isolates air convection, reducing heat loss
The magnetron sputtering coating can withstand temperatures up to 600°C
A metal-glass composite structure developed in 2024 can endure temperatures up to 600°C
Market share exceeds 70% in China's solar water heater market
Additionally, vacuum heating tubes are also used in industrial coating equipment, where they are made of stainless steel and employ special processes to operate stably in high-temperature vacuum environments.