Hydrogen gas gap heat switch operating in the 150 K to 400 K temperature range

A prototype of a compact hydrogen gas gap heat switch (GGHS), built using the difference in the linear thermal expansion coefficients of copper and stainless steel, was designed to work in the temperature range of 150 K to 400 K. Using hydrogen, nitrogen and helium as working gas, a gap of 18 µm was measured. With hydrogen, an ON/OFF switching ratio higher than 100 was obtained at 150 K. A sorption pump was integrated to the GGHS and filled with the metal hydride ZrMn₂ to overcome the very low adsorption of hydrogen with activated carbon, material frequently used to manage the pressure in the gap. This solution allowed to reach both ON and OFF states by varying its temperature between 150 K and 300 K. The results obtained suggest that the proposed design allows for the development of tunable hydrogen heat switches while keeping the assembly very simple and sturdy.