Cryogenic
applications such as for liquid nitrogen, oxygen, argon, carbon dioxide, and liquefied
natural gas are natural applications for the use of NanoPore™ based vacuum panels because of the very high temperature
driving forces between ambient temperature and the liquid temperature. Examples include transfer piping, dewars for storage
and transportation, insulation for low temperature devices, and low temperature freezers. The performance of all insulation
varies as a function of temperature. For cryogenic applications, the performance of insulation improves over the room
temperature performance. A graph of both thermal conductivity and R-value for NanoPore™ based insulation products at various
temperaures is shown below (note temperatures are in Kelvin).
Because of the large thermal gradients, the insulation value of importance is the mean value averaged over the values on the
cold and hot side. A demonstration of the performance of NanoPore™ VIP insulation versus conventional insulations in a liquid
nitrogen storage test is given below.
Case Study - Liquid Nitrogen Boiloff
A four liter plastic (PET) box with dimensions of 140 x 140 x 200 mm was surrounded with insulation panels. On all sides but
the top, the edges were sealed. Liquid nitrogen evaporation (measured gravimetrically) was used for either NanoPore™ VIPs or
1” polyurethane insulation backed with foil on both sides. The NanoPore™ panels had a thickness of either 12 mm (½” nominal)
or 24.5 mm (1” nominal). Polyurethane boxes were built up using one, two, or three layers of 1” insulation. The nitrogen boiloff
loss from these various insulation configurations are shown below. Duplicate tests of the 1” vacuum panel tests are also included.
Small differences in the starting weight simply reflect slight changes in the liquid level when we started taking rate measurements.
In all cases, the ambient temperature during the measurements was between 20 and 22°C.
It can be seen in the figure above that the ½" VIP insulated container exhibited a lower boiloff rate than the container insulated
with 3" of polyurethane foam. The calculated R value per inch for the VIPs in this configuration is R57/inch, while the value calculated for
the foam insulated containers is R11/inch. While the performance of both insulation improves under low temperatures, the NanoPore™ VIPs
provide more than 5½ times better performance!
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