Research of physical properties of the wicks obtained by sintering the dispersed copper powder in the construction of thermosyphons and heat pipes

The method of powder metallurgy for manufacturing evaporative capillary cartridge using molds from fine copper powder (grade PMS-1) is proposed. The aim of this study is the selection of design and manufacture modes of instrumentation of fine powder copper (grade PMS-1) by powder metallurgy, which provides high performance. The influence of filling with activated carbon and the effect of powder particles of carbamide in the copper on the product’s capillary structure were investigated. A few variants of molds for the evaporative cartridges were made, ensuring accurate manufacturing of porous wick by means of powder metallurgy. The optimum sintering temperature of copper powder, which provides sufficient mechanical strength, thermal conductivity of instrumentation, optimal porosity of the powder structure that gives it the properties of the capillary pump and steam generator, is 840-850 °C. The wall thickness of the cartridge was defined as 2.5-3.0 mm by evaporation of water and alcohol during heating of the wick. Copper powder PMS-1 (State Standard 4960-75) is the most suitable material for the cartridge production. The wettability of copper wick depends on its capillarity, its purity before the pressuring, and pressure. A copper wick wets with considerable intensity in a vacuum. The influences of covering the molds by activated carbon and effect of the carbamide addition to the copper powder on the capillary structure of the products were studied. A mixture of copper powder and carbamide (less than 5 vol. %) as a raw material for sintering mold has the advantages of increasing porosity of instrumentation, easy removing of preforms from the molds and reducing of oxidation. The conditions for increasing the porosity of the structure, simplifying the removal of wick blank from molds and reducing of oxidation were recommended. Results of the study of the wicks may be used in the design of constructions of thermosyphons and heat pipes.