Compatibility and lifespan of heat pipes

Compatibility and lifespan of heat pipes

The compatibility of a heat pipe refers to the ability of the working liquid inside the pipe to undergo no significant chemical or physical changes with the shell during its expected design life, or changes that are not sufficient to affect the performance of the heat pipe. Compatibility is of great significance in the application of heat pipes. Only heat pipes with good long-term compatibility can ensure stable heat transfer performance, long-term service life, and the possibility of industrial applications. Carbon steel water heat pipes effectively solve the chemical reaction problem between carbon steel and water through chemical treatment, which enables the large-scale promotion and use of high-performance, long-life, and low-cost heat pipes in industry.

There are many factors that affect the lifespan of heat pipes. In summary, the main forms of incompatible heat pipes are as follows: the generation of non condensable gases; Deterioration of thermal properties of working fluids; Corrosion and dissolution of shell materials.

(1) Non condensable gas is generated due to chemical or electrochemical reactions between the working liquid and the pipe material. During the operation of the heat pipe, this gas is blown by the steam flow to the flushing and condensing section, forming a gas plug, which reduces the effective condensation area, increases thermal resistance, deteriorates heat transfer performance, reduces heat transfer capacity, and even fails.

(2) The physical properties of working fluids deteriorate. Organic working media will gradually decompose at a certain temperature, mainly due to the unstable properties of organic working fluids or chemical reactions with shell materials, which can alter their physical properties. Organic working liquids such as toluene, alkanes, and hydrocarbons are prone to such incompatibilities.

(3) The corrosion and dissolution of the shell material result in continuous flow of the working liquid inside the shell, as well as factors such as temperature difference and impurities, leading to dissolution and corrosion of the shell material, increased flow resistance, and decreased heat transfer performance of the heat pipe. When the shell is corroded, it causes a decrease in strength and even leads to corrosion perforation of the shell, resulting in complete failure of the heat pipe. This type of phenomenon often occurs in alkali metal high-temperature heat pipes.

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