U-pipe is copper pipe welded as "U" shape installed inside the evacuated tube then all the U-pipes are welded with two main copper pipes in the manifold. In AUDSUN U-pipe collector water or antifreeze circulates inside every U-pipe then pass through the main copper pipes on the top to transmit the heat while in heat pipe collector the water will just go through the main pipe in the manifold.

All the U-pipes and aluminium heat conducting sheets are well installed in the collector by AUDSUN workers before leaving the factory so you just need to insert the evacuated tubes to each U-pipe and fix them with tube supports on the brackets when you receive the product.

Because the diameter of U-pipe is small (Φ9mm) antifreeze is recommended to be used for the circulation inside the U-pipe however water of poor quality will block the pipe. But heat is collected from every tube of the collector to get high efficiency and higher percentage of antifreeze you use lower temperature environment it can be used. Of course, you should make good insulation for the outlet piping.