A hybrid cooling system combining self-adaptive single-phase mechanically pumped fluid loop and gravity-immune two-phase spray module

Highlights: • Usage of phase change material and ejector realizes the operation of hybrid system. • A Great compatibility between single-phase module and two-phase one is obtained. • Gravity immunity features the proposed system for space application. • Thermal tests were conducted to verify the coordinated operation between modules. • Systematic operation efficiency is 17.7 which illustrates a high economy. - Abstract: Although single-phase mechanically pumped fluid loop (MPFL) and two-phase spray cooling technologies have been investigated independently for decades, there is a lack of understanding on the combined operation of these two modules. The MPFL has been extensively utilized in the space thermal control system due to its technological maturity and gravity immunity. The spray cooling, which is characterized by the speciality in thermally dealing with the high heat flux equipment, has not gone that far owing to its complexity in the management of the two-phase flow in the space environment. It is also acknowledged that the MPFL, as an overall cooling strategy in the space thermal control system, will not be replaced completely in the foreseeable future because the primary on-board electronic devices require normal heat dissipation demand and only a few equipment such as on-board laser diode and multi-chip modules demand extreme high heat removal technologies. Therefore, a combination of the MPFL and spray cooling technologies, which constitutes the biggest innovation in this paper, is imperatively needed. A hybrid cooling system (HCS) combining the single-phase self-adaptive MPFL and gravity-immune two-phase spray module which satisfies various cooling demands is proposed in the present study. A validating system as a prototype was established on the basis of the optimal design method. Three test cases were conducted to verify the coordinated operation between the single-phase module and two-phase one and investigate thermal performances of both modules. In all the experiments, the controlled temperature of the cold plate in the MPFL remains within a range between 35.9 °C and 41.9 °C under the heat load from 50 W to 150 W. The highest heat flux acquired by the spray cooling module can be up to 468.8 W/cm² with the superheat level being 70.0 °C. Results can be drawn that the two modules can be operated simultaneously and independently. Systematic operation efficiency of the proposed HCS is calculated to be 17.7 which displays a high economy of the proposed system.