The heat pipe heat exchanger with the heat pipe as the heat transfer unit is a new type of high efficiency heat exchanger, which is composed of a casing, a heat pipe and a partition plate. As the main heat transfer element, the heat pipe is a heat transfer device with high thermal conductivity. It is a vacuum container whose basic components are a housing, a wick and a working fluid. The casing is evacuated and filled with an appropriate amount of working fluid, and the sealed casing constitutes a heat pipe. When the heat source supplies heat to one end, the working fluid absorbs heat from the heat source and evaporates and vaporizes. The steam carrying latent heat is transmitted to the other end of the casing at a high speed under the pressure difference, and the latent heat is released to the cold source to be condensed, and the condensate is returned to the condensate. The hot end is boiled again. Repeatedly, the heat is continuously transferred from the hot end to the cold end.

The heat pipes are classified into three types: wicking heat pipe, gravity heat pipe and centrifugal heat pipe according to the condensate circulation mode. The condensate of the wick heat pipe returns to the hot end according to the action of the capillary tube. The heat pipe can work under weight loss; the condensate of the gravity heat pipe flows back to the hot end by gravity, and its heat transfer has unidirectionality, generally Vertical placement of the centrifugal heat pipe relies on centrifugal force to return the condensate to the hot end, typically for cooling of rotating components.

The heat pipe is divided into four types: deep cold heat pipe, low temperature heat pipe, medium temperature heat pipe and high temperature heat pipe according to the working temperature of the working fluid. The cryogenic heat pipe works below 200K, and the working fluid has nitrogen, hydrogen, helium, oxygen, methane, ethane, etc.; the low temperature heat pipe works in the range of 200~550K, and the working fluid has Freon, ammonia, acetone, ethanol, water, etc. The medium temperature heat pipe works in the range of 550~750K. The working fluid has thermal conductivity A, mercury, strontium, water and potassium-sodium mixture; the high temperature heat pipe works above 750K, and the working fluid has liquid metal potassium, sodium and lithium. , silver, etc.

The heat transfer characteristic of the heat pipe is that the heat transfer in the heat pipe is carried out in three steps of boiling vaporization, steam flow and steam condensation. Since the convective heat transfer strength of boiling and condensation is large, and the steam flow resistance loss is small, both ends of the heat pipe The temperature difference can be small, that is, a large heat flow can be transmitted with a small temperature difference. Therefore, it is especially suitable for low temperature differential heat transfer and some occasions with high isothermal requirements. The heat pipe heat exchanger has the advantages of simple structure, long service life, reliable operation and wide application range, and can be used for heat exchange between gas-gas, gas-liquid and liquid-liquid.

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