Intensification of heat transfer in the zone of the thermosyphon evaporator when changing the boiling surface shape

Abstract

In present paper the influence of the boiling surface treatment types of thermosyphon evaporator on the heat transfer coefficient was studied. An experimental setup «Loop thermosyphon with replacing lower part of the evaporator» has been developed and assembled. This feature makes it easy to replace samples with various surface modifications as the lower part of the evaporator. The description of the experimental setup, equipment and research methods is given. Heat transfer coefficients for the samples at various applied thermal loads (from 5 to 200 W) were calculated. In case of flat aluminum plate (boiling surface) concentric grooves and uneven coating of aluminum oxide particles, an increase of the heat transfer coefficient from h1= 5760 W/(m2·K) to h2= 28339 W/(m2·K) at the supplied heat flux density q = 250 kW/m2was observed. The heat transfer coefficient for a sample without concentric grooves, but with an uneven coating of aluminum oxide particles was h3= 16952 W/(m2·K) at q = 250 kW/m2. Results of the study can be used for further increase of thermosyphon evaporator efficiency.