A thermal-hydraulic test loop was designed and built to provide measurements that
can be used in the analysis of long length HTS cable systems. A schematic of the simulated
HTS cable test apparatus is shown in FIGURE 3. It was built by Eden Cryogenics in Plain
City, Ohio. Liquid nitrogen can be circulated through the test loop in either a counterflow
or parallel flow cooling arrangement. The distance between bayonet flanges is 4.7 meters.
The length of the flow path from the inlet flange to the far end where the flow turns around
in the counterflow arrangement is about 6.2 meters. There are five connections on the left
side. Two of the connections are for the liquid nitrogen inlet and outlet for counterflow
testing, two for instrumentation (thermometer) connections, and the last feedthrough is for
the electrical heater connections.
The simulated HTS cable consists of a standard 304 stainless steel tube with a
diameter of 12.7 mm and a wall thickness of 0.889 mm. It is wrapped with a resistive wire
heater that has a room temperature resistance of 0.157 ohms/m to simulate heating
developed in a HTS cable by ac loss. The cryostat has a 50.8 mm nominal pipe size inner
diameter. The tube is connected to the left side end piece and connected to the test section
using a bayonet connection. Liquid nitrogen is supplied through the inlet flange. The bare,
heated tube provides a limiting case where the inter-stream conductance is the highest.
Additional details can be found in [8].
The right side end piece is joined to the test section with a bayonet and has two
flanges. The flange on the top is for future instrumentation, and the flange on the side is the
liquid nitrogen outlet for parallel flow testing to be conducted at a later date.
The inlet and outlet temperatures are measured using temperature sensors in a
stainless steel sheath mounted in a tee upstream and downstream of the inlet and outlet
flange connection respectively. Measurements of the flow temperature and tube outer wall
temperature were made in order to provide information on the heat transfer processes in a
HTS cable. These thermometers are mounted in G-10 holders that are equally spaced over
a distance L=4.7 m along the tube. The first thermometer holder is located 50 mm past the
tip of the supply side bayonet. The last thermometer holder is located 50 mm before the
end of the tube. All of the temperature sensors are Lakeshore PT-103 thermometers which
were factory calibrated to within +/-0.02 K at 100 K. One sensor in the annular flow at
X/L=0.75 had a broken electrical lead and could not be read.