Experimental investigation of free convective heat transfer along inclined pipes in high-pressure cryogenic storage tanks

The minimization of heat intake is one of the main challenges in the design process of cryogenic storage tanks. Previous investigations, mostly based on numerical calculations, have shown that connection pipes can increase the heat intake significantly. Under certain geometric conditions a free convective flow field builds up which is able to enhance the heat transfer from the warm end to the cold end of the pipe in a dramatic way. However, this effect is mainly an issue for high-pressure cryogenic storage tanks. In order to investigate the transferred heat experimentally, a test cryostat was designed and manufactured. It is pivot-mounted and can be positioned at any angle of inclination. Inside the cryostat vessel a thermally isolated test pipe with a maximum length of 1 m and a maximum fluid pressure of 200 bar can be placed. This paper gives a closer look at the cryostat design and the measuring principle. First measurement results for a helium filled 20x2x100 mm test pipe under various pressure levels are discussed. The measured heat transfer has a more dramatic maximum than anticipated and can achieve about 33.5 Watts at an inclination angle of γ = 15° for the test pipe under consideration.