Design of Compact High-Effectiveness Cryogenic Counter-Flow Heat Exchangers for Remote Cooling and Space Reverse Turbo-Brayton Applications

Abstract

Heat exchangers (HEX) are the backbone of almost all thermodynamic cycles. In cryogenics they are a demanding technological brick and their effectiveness can be a cornerstone for the performance of an entire system. A highly effective counter-flow heat exchanger (CFHEX) plays a crucial role in systems that are based on fluid circulation. Such systems enable cooling in the range between ≈ 2.5 W and several Watt at 4.5 K, which is above the cooling power range of an individual small-scale cooling source (e.g. cryocooler) and outside of the working range of a large-scale cryoplant [1]. Examples of applications that would benefit from such enhanced cooling capacities are infrared detectors and spectrometers in space missions [2], Superconducting Radio-Frequency (SRF) cavities in particle accelerators [3], Superconducting QUantum Interference Devices (SQUIDs) that, for instance, are used in the CERN Antiproton Decelerator [4-6], superconducting proton and heavy-ion therapy gantries for medical applications [7,8], cryogenic mirrors in gravitational-wave detectors (e.g. KAGRA [9]) and low-temperature experimental platforms. Moreover, for many of these applications, the cryogenic cooling needs to be provided in a minimised-disturbance and remote manner. The novel solutions, which are being developed to meet this challenging cooling requirement [10], heavily rely on effective and compact CFHEXs.With these purposes in mind, the development of a compact higheffectiveness counter-flow heat exchanger technology for space and high-energy applications was fostered under the initiative of the European Organization for Nuclear Research (CERN) and the European Space Agency (ESA). The design of CFHEXs, which allows to expand the existing cryogenic cooling capabilities and to enable a range of highly demanding applications, is the topic of this thesis.This chapter will outline the cooling cycles used for cryogenic applications * The value range is approximated from [13] as well as assuming the maximum tube packing density.** The value depends on the mesh number or sphere diameter. *** A single value is given instead of a range due to availability of data from [53].