Experimental study of the connecting tube at the cold end of a U-shaped pulse tube cryocooler

• Influence of the connecting tube was experimentally studied.
• The performance is influenced by the straightener, thermal conductivity, and shape.
• The optimized connecting parts induced more than 10% cooling capacity reduction.

For certain special applications, pulse tube cryocoolers must be designed in a U-shape. Although the connecting tube at the cold end will influence the cooling performance, there is very little systematic experimental study concerning this connecting tube. In this paper, a pulse tube cryocooler was designed to study the influence of the connecting tube. The flow straightener between the connecting tube and the pulse tube was first optimized to avoid jet flow in the pulse tube. The influence of the diameter, length, thermal conductivity, and shape of the connecting tube were then studied. Even when the connecting parts are optimized, the performance of the U-shaped pulse tube cryocooler is more than 10 percent worse than that of an inline pulse tube cryocooler.