Comparison of Liquid Nitrogen Flow Resistance in Corrugated Pipe With Smooth Pipe for HTS Cable

In the high-temperature superconducting (HTS) cable system, liquid nitrogen is usually chosen to be the coolant because of its low saturation temperature and large latent heat of vaporization. The liquid nitrogen should be forced to flow in the cryostat, which is usually made of flexible corrugated pipes. Compared with smooth pipes, the surface of corrugated pipes is more complicated and rough. Thus, the characteristics (e.g., wave pitch and wave depth) of corrugated pipes have more effects on the flow resistance coefficient between corrugated pipes and liquid nitrogen. In this paper, an original model was referenced to analyze the effect of corrugated characteristics on the flow resistance of liquid nitrogen. In addition, an experimental apparatus was set up to measure the flow resistance of liquid nitrogen in the corrugated and smooth pipes, respectively. The flow resistance of liquid nitrogen gradually increases as the wave pitch of the corrugated tube decreases and the wave depth increases. The flow resistance coefficient in corrugated pipes is three times as large as that in smooth pipes at least.