Frosting characteristics and prediction of thickness of frost layer on a finned tube in regasification process of cryogenic liquids
Abstract Frost frequently forms on cryogenic equipment and is the main reason for the decline in the heat transfer of cryogenic ambient air vaporizers. In this paper, the characteristics of frosting on the surface of a finned tube in the regasification process of liquid nitrogen were investigated by a series of experiments. The experiments were conducted in an air temperature range of 2–12°C and a humidity range of 1.4–4.0 g•kg–1. The results show that frosting of the finned tube is complex, and a new “wisteria-type” frost crystal is observed at the inlet of the finned tube. The “wisteria-type” frost crystal is formed in the area of the fins with an initial temperature drop rate of higher than 2.32°C•min–1. The data on the frost layer thickness show that along the tube, the frost layer thickness first decreases and then increases, which results from the wall temperature and the concentration of water vapor. A comparison of the measured data with the frosting models in the literature is also presented. Moreover, the wall temperature is identified to modify the frosting model. The modified frosting model can predict 62.4% of the present database within a ±25% error band. This work highlights the vital role of the wall temperature in the frost porosity.