What is HyFI?
The HyFI test system is designed for measuring properties of sediments and pure-phase materials, with a particular focus on gas hydrates. The term "Hydrates From Ice" refers to a technique in which hydrate is formed by slowly warming granular ice in a pressurized atmosphere of the hydrate former (methane, for instance). This methodology was developed at the USGS (Menlo Park) by Dr. Stephen Kirby and Laura Stern [Stern et al., 1996; 1998].
During an experiment, a pressure vessel containing hydrate rests in a temperature controlled bath capable of maintaining stable temperatures from -25°C up through the hydrate stability temperature (generally less than room temperature). The bath itself is held in a chest freezer to insulate it from room air fluctuations. The chest freezer and bath controller are housed in a fume hood. The hood provides a measure of safety in case of gas leaks during experiments with hydrocarbon gases, and allows us to work with volatile hydrate formers such as tetrahydrofuran (THF).
HyFI has been used to measure thermal properties, defined succinctly by Briaud and Chaouch :
Thermal conductivity, λ: if λ is high, heat travels easily through the material.
Thermal diffusivity, κ: if κ is high, it takes little time for the temperature to rise in the material.
Specific heat, cp: if cp is high, it takes a lot of heat to raise the temperature of the material.
The U.S. Geological Survey (USGS) is investigating gas hydrate thermal properties in support of efforts by the USGS and others to obtain methane from gas hydrates as an energy resource, mitigate the geohazard potential of gas hydrates, and understand the role hydrate-derived methane plays in global climate change. Our published data are available for download via links at the bottom of each measurement result page, just below the journal citation.