Study of short low temperature range heat pipes. Part 2. Theoretical model*

Abstract
*The beginning of article in «Vestnik Mezhdunarodnoi akademii kholoda» 2014, No 4, р. 38-43. The research results of heat transfer coefficient and pulsation vortex flows in the vapour channel, resembling to Laval nozzle, of short low-temperature range heat pipes are presented. In a cooled top cover of the heat pipes capacitive sensors, which are exposed to electromagnetic pulses from an external generator, are installed. When the heat pipe evaporator is heated electromagnetic pulses became modulated starting from a certain boundary value of the thermal power. It is connected with the beginning of boiling in the evaporator, and the formation of a large amount of vapour that leads to a rapid increase in pressure and termination boiling in the evaporator, and the occurrence of the pressure pulsations in the vapour channel. The frequency of pulsations, with its dependence on the magnitude of the evaporator overheating, are measured. It is shown that the frequency of pulsations are higher and they occur at lower values of overheating of the evaporator in the heat pipes with vapour channel, resembling to Laval nozzle, compared with heat pipes with standard cylindrical vapour channel of the same dimensions.