Thermal behavior in compact-type cryogenic needle valve with integrated heat sinks

A cryogenic needle valve is used to precisely control the flow rate of working fluids such as liquid hydrogen and liquefied natural gas, making it essential to design the valve with consideration of the cryogenic environment. To prevent freezing of the packing materials, which directly affects leakage, extended bonnet-type valves are commonly used. In these designs, the bonnet length is increased to position the packing farther from the flow path. However, due to spatial constraints, extended bonnet structures are often unsuitable for installation in confined spaces. To address this limitation, a compact-type valve was developed by significantly shortening the bonnet length and incorporating a heat sink capable of providing the required heat transfer performance within the reduced length. In this study, a cryogenic environment test using liquid nitrogen, along with heat transfer analysis, was conducted on the compact-type cryogenic needle valve to evaluate the thermal behavior of its components. A parametric study and size optimization were performed by treating the heat sink's outer diameter and thickness as shape design variables, with the goal of minimizing its size while maintaining the necessary heat transfer performance in the shortened bonnet. As a result of the optimization, the heat sink volume was reduced by approximately 54% compared to the initial design. A cryogenic leakage test was subsequently conducted on a prototype equipped with the optimized heat sink, in accordance with BS6364, confirming that no leakage occurred.