Experimental Investigation of New Flat-Plate-Type Capillary Pumped Loop

摘要

A capillary pumped loop is a two-phase heat transfer device which has been increasingly applied in thermal control of satellite or spacecraft and electronic cooling. However, startup performance of a normal capillary pumped loop is poor and hydrodynamic oscillation in the system appears sometime during its operation. A flat-plate-type capillary pumped loop is constructed and tested in the present study, which combines the advantages of a capillary pumped loop and a loop heat pipe by improving both system and components. In the present capillary pumped loop, both evaporator and condenser are designed as a type of flat plate with porous wick, and a reservoir is used to control and adjust operation temperature of the system. In addition, a subcooler is adopted to improve the quality of working fluid flowing back to the evaporator. A plane type of evaporator with a cross channel for the liquid supply was made to reduce the probability of a dry-out point caused by strong evaporation in the case of high heat flux, and therefore to enhance the stability of the system. Also, a plane type of condenser with a porous wick is designed, which is of the three ports for vapor-pipe inlet, liquid-pipe outlet, and an adjusting pipe connected to a reservoir. The startup performance of the system benefits greatly from this three-port design, as liquid in the system can be easily pressed into a reservoir due to resistance reduction. The performance of a capillary pumped loop prototype was tested in startup, persistence operations, and different vacuum. Startup experiments under different heat loads and working conditions were conducted. Excellent startup performance, being stable and easy, has been shown for the plane-type capillary pumped loop system, which validates the new configuration. Pressure oscillation and temperature fluctuation in the system were reduced largely owing to the induction of a porous wick in the plane condenser. During experimental processes lasting more than 10 h, the new type capillary pumped loop shows outstanding thermal behavior and no dry-out phenomena were observed. The testing results indicate that 1) the new capillary pumped loop system shows excellent startup performance without pressure priming and liquid clearing of vapor line; and 2) the new capillary pumped loop system is stable under very severe operational conditions, such as low load, sudden power step, etc.