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Two-Phase Loops with Capillary Pump (Loop Heat Pipes (LHP) and Capillary Pumped Loops (CPL)) are currently among advanced thermal control technologies for aerospace applications. Large numbers of experimental and operational two-phase loops were successfully tested and used in several spacecraft in the past two decades. Novel technologies such as Advanced CPL-LHP, High Performance CPL, miniature LHPs, inversion (reversible, “Push-Pull") LHPs, ramified, multiple evaporator and condenser LHPs and CPLs, for complex thermal control systems are being proposed. This paper presents a state-of-the-art survey and analysis of these technologies. A classification of Two-Phase Loop with Capillary Pump designs is recommended. Basic principles, operational conditions and characteristics, temperature control and start-up initiation are discussed. The use of thermal control systems based on Two-Phase Loops with Capillary Pump for space applications is reviewed and summarized.

The main objective of this study is to develop a mathematical model for the simulation of the thermal characteristics of two-phase capillary pumped devices. The mathematical model presented in this paper is an extension of the earlier mathematical model developed for a conventional heat pipe. The three-dimensional incompressible energy, momentum and mass conservation equations are solved by using the finite element method. Except in the wick region, the viscous terms in the governing equations are neglected. However, the pressure drops due to frictional losses are introduced. The interface between vapor and liquid phases is assumed static and only converged steady-state solutions are retained. The reservoir dynamic is not modeled. The energy, momentum and mass jump conditions are written across the interface. The resulting set of equations is solved iteratively until the overall mass conservation is satisfied between the evaporator and condenser.