The study of the flow in the vapour channel of short linear heat pipes

E-mail: seryakovav@yandex.ru The results of studies of flow of moist vapour in Laval-like vapour channels of short linear heat pipes (HPs) are pre- sented. The increase in heat transfer coefficient of short linear HPs, intended for creation of the cooling systems of heat-stressed designs of spacecraft, is carried out by making the HPs vapour channel forms similar to the shape of the Laval-like nozzle. Comparison of the heat transfer coefficients of short HPs with the standard cylindrical vapour channel and the channel, made in the form of the Laval-like nozzle with the equality of all dimensions, flat evaporator and the same amount of the working fluid, shows that the HPs with the vapour channel in the form of the Laval-like nozzle exceeds the heat transfer characteristics of the standard HPs with a cylindrical vapour channel under high ther- mal loads. The study of the flow and condensation in such shaped vapour channels of the short HPs at high thermal loads gives an opportunity to analyze in detail the advantages of using such HPs and make the conclusion about the necessity of wide introduction of such HPs for the cooling systems of the spacecraft. Capacitive sensors were addition- ally installed in cooled top covers of the HPs, and electromagnetic pulses with a frequency of 100 kHz were supplied to them from the external generator. At heating the HPs evaporator, starting from a certain thermal power threshold value, electromagnetic pulses became modulated. It is related to the formations of the boiling process in the capillary- porous evaporator and large amount of vapour over it and its discontinuous distribution. It was discovered that the frequencies of the pulsations are more and they occur at lower values of heat load at the evaporator in the HPs with a vapour channel of a Laval-like nozzle, compared to the HPs with the standard cylindrical vapour channel with equal overall dimensions.