Experimental Study Of Frosting Process On A Vertical Star-Shaped Finned-Tube

Star-shaped finned-tube is widely used in various types of cryogenic systems from the turbocharger of cryogenic tankers to the vaporizer of cryogenic liquid storage tank for its simple structure, light weight and manufacturing convenience. When vaporizer is working, it absorbs heat from ambient air, meanwhile, frost will form on the finned-tube surface as soon as the fin surface temperature is lower than the three-phase point of humid air temperature. Frost increases both thermal resistance and air resistance, so the heat transfer coefficient will reduce, which also make the thermal performance reduce. So it is very necessary to have research on frosting characteristics for star-shaped finned-tube.In this paper, an experimental rig is designed and installed to test the performance of the star-shaped fin tube in the frosting process in different operating conditions. The growth process of frost layer on the finned surface is investigated, research on the performance of the star-shaped fin tube under frosting condition with different environmental factors and changing pressure and volume flow of the medium is also carried out. This result is obtained: the greatest impact on frost formation on the finned surface is given by air humidity while the flow is stable, compared with pressure and volume flow.In addition, by measuring the frost layer thickness and the temperature difference between import and export, the curve diagram for mean frost thickness and the temperature difference is painted out. From the curve it is founded that the temperature difference reduces when the frost layer thickness increases, which shows the frost formation reduces the performance of the finned-tube. Finally, an investigation is also carried out for the pressure drop of the finned-tube, from which the curve diagram for pressure drop and mean frost thickness is obtained. It's also found that if the volume flow and the air flow remain stable, it will keep the frost in soft cream form at the lower part of the finned-tube, instead of melting and freezing. When the falling airflow once forms, it will take the frost away from the fin surface, which helps to do the defrosting job.Through the study on the frosting process on the star-shaped fin tube, it shows great significance to the optimization of environmental parameters, improvement of the vaporizer performance and methods of defrosting.