Experimental study and dynamic simulation of a coaxial annular tube convective heat switch

Abstract Heat switches are used in cryogenic systems to manage the heat flow. The convective heat switch is a passive device whose thermal conductance depends on the temperature difference of the two extremities. Previously, we investigated a heat switch with a novel structure using CFD methods and obtained geometric dimensions for manufacturing. We fabricated a heat switch, tested its thermal performance, and used it for precooling a 1 K system without a heat load. The fabricated heat switch operated effectively from room temperature (300 K) down to the base temperature (4 K). The thermal conductance is 15.26 mW/K when the temperatures at the two ends are 4.02 K and 28.62 K, indicating somewhat inefficient heat transfer. The cooling process can be divided into three distinct stages based on the cooling rate: initiation, acceleration, and disconnection. In the acceleration stage, the convective circulation inside the heat switch intensifies, improving the heat exchange effect.