Cryogenic Variable Conductance Heat Pipe

Our proposed innovation advocates the use of well-known variable conductance heat pipe (VCHP) technology for cryogenic applications where temperature control of sensitive components is also required. IR sensors operating at cryogenic temperatures frequently require temperature control to plus or minus 1.0 degrees C while some applications demand finer control down to pluse or minus 0.1 degrees C. While VCHP's have been used on satellites to control electronic components to narrow temperature bands, despite changes in load and environment that are normally experienced, they have not been developed for cryogenic applications. Our program seeks to evaluate their use by studying the available combinations of working fluids and noncondensible gases that lead to efficient (VCHP) control systems. We propose to use a modified version of a successfully developed monogroove heat pipe as our VCHP baseline design because it has many desirable features in cooling cryogenic IR sensor systems currently being sought by AF and NASA. Having but a single groove, it provides maximum heat transport with minimum fluid charge thereby reducing ambient pipe pressure; it can be configured with flexible sections to provide compliance; it can be configured with multiple evaporators to accommodate multiple sensor/single cooler applications.