Woods Hole Science Center
What thermal properties do we measure?In each experiment, we simultaneously measure thermal conductivity, thermal diffusivity and specific heat. Thermal conductivity, λ: The amount of heat passing through a body in response to a thermal gradient. A low thermal conductivity material is like insulation in a house, letting very little heat pass out of the house on a cold day. The units are (W/m·K). Thermal diffusivity, κ: The rate at which heat spreads through a body. It is a function of the body's thermal conductivity and its specific heat. A high thermal conductivity will increase the body's thermal diffusivity, as heat will be able to conduct across the body quickly. Conversely, a high specific heat will lower the body's thermal diffusivity, since heat is preferentially stored as internal energy within the body instead of being conducted through it. The units are (m2/s). Specific heat, cp: The amount of heat required to raise the temperature of one kilogram of material one degree Celsius. The units are (J/kg·K). Why are these properties important to know?Methane hydrate stability depends sensitively on temperature, meaning thermal properties are important for modeling thermal fluctuations at local, regional and global scales [Ruppel, 2000; Xu and Germanovich, 2006].
How do we measure these properties?We have developed a method for simultaneously determining λ, κ, and cp [Waite et al., 2006] based on the von Herzen and Maxwell [1959] needle probe thermal conductivity measurement and the analytical approach of Blackwell [1954]. Here we describe both the simultaneous measurement technique and the needle probe measurement apparatus. Publication:The measurement process described here is published in: Waite, W. F., Gilbert, L.Y., Winters, W.J., and Mason, D.H., (2006), Estimating thermal diffusivity and specific heat from needle probe thermal conductivity data, Review of Scientific Instruments, 77, 044904, doi:10.1063/1.2194481.
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