Improving the Efficiency of Thermosiphon Radiators by Structuring the Outer Surface of the Heating Tube

The main advantages of thermosiphon radiators over classic analogues are low metal consumption, an isothermal surface, a significant reduction of the heating water volume in the radiator, high corrosion resistance and aesthetics. At the same time there are also disadvantages such as insufficient heat transfer during the phase transition of the heat transfer liquid, and a characteristic humming noise at the nucleate boiling stage that significantly narrows the area of application of thermosiphon radiators in residential buildings. The authors propose a method of deformational cutting to obtain a complex heat exchange microstructure on the outer surface of the heating tube. The microrelief obtained by deformational cutting has a capillary effect, thus supporting intensification of the phase transition due to the significant enlargement of the heat exchange surface area. The phase transition in microrelief does not generate bubbles and therefore eliminates the noise when the radiator is in operation. High processibillity of the deformational cutting method has a minimal effect on the cost of the radiator. Isopropyl alcohol evaporation process is studied for various micro-structured surfaces obtained by deformational cutting. Compared to a smooth surface, the tested microrelief surfaces have shown a two-fold increase in heat exchange capacity, without the noise typical of nucleate boiling.

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