Study of thermal transport in highly anisotropic materials for space recuperator applications

Abstract

A high-effectiveness, low-pressure-drop recuperator is one of the critical components of energy-efficient, high-capacity, low-temperature cryocoolers for long-term storage of cryogens including hydrogen. This paper presents an investigation of the thermal transport mechanisms in highly anisotropic materials. These materials enable the development of compact, lightweight, high-effectiveness recuperative heat exchangers. The high in-plane thermal conductivity allows effective heat transfer from the hot stream to the cold stream, while the low out-of-plane thermal conductivity keeps undesirable axial conduction to a minimum. The concept suggested in this paper could lead to a disruptive technology which affects how future space heat exchangers are designed and built. This is the first time an investigation is carried out to exploit the unique thermophysical properties of lightweight, highly anisotropic materials to enable the development of high-effectiveness, compact and lightweight recuperators for cryocoolers. A very attractive design feature of the recuperator is its modularity, so that high gas flow rates can be obtained by simply increasing the number of modules. NASA Space Technology Roadmap indicates that compact cryocoolers capable of removing 20 W or greater of heat from liquid hydrogen storage tanks could offer significant mass savings of cryogenic propellants through zero boil-off (ZBO), and thus enable long-duration space missions.