Characteristics of low-temperature short heat pipes with a nozzle-shaped vapor channel

This paper presents the results of experimental and numerical studies of heat transfer and swirling pulsating flows in short low-temperature heat pipes whose vapor channels have a conical nozzle shape. It has been found that as the evaporator of the heat pipe is heated, pressure pulsations occur in the vapor channel starting at a certain threshold value of the heat power, which is due to the start of boiling in the evaporator. The frequency of the pulsations was measured, and their dependence on the superheat of the evaporator was determined. It is found that in heat pipes with a conical vapor channel, pulsations occur at lower evaporator superheats and the pulsation frequency is greater than in heat pipes of the same size with a standard cylindrical vapor channel. It is shown that the curve of the heat-transfer coefficient versus heat load on the evaporator has an inflection corresponding to the start of boiling in the capillary porous evaporator of the heat pipe.