The Characteristic Research Of Fast Cooling Technology Utilizing Thin Film Evaporation

Many energy saving technologies have been applied on vessels, but marine frozen preservation technology are outdated. Cooling and freezing methods used are the traditional convective and conductive heat transfer which apparently have lower heat exchange efficiency. Phase change heat transfer shows better performance. Therefore, it has significant social and economic values to develop a new and fast freezing technology using phase change heat transfer and apply them to marine refrigerated transport. This thesis researches the fast freezing technology utilizing thin film evaporation via experiments and numerical simulation.The main research tasks are represented below:(1) The feasibility of the fast freezing method based on liquid nitrogen thin film evaporation was verified by experiments. (2) The variation of the heat transfer characteristics of the frozen carrier has been analyzed by using the experimental data. (3) The heat transfer model of the frozen carrier has been established, which can analyze and optimize the frozen carrier.The following conclusions can be obtained:(1) The frozen carrier and the fast cooling technology designed in this thesis can acquire an high average cooling speed (90,437.14℃/min) in the 0℃～-60℃ temperature zone. (2) Two types of frozen carriers that one is etched micro structure on the surface (MSS) and another is plain surface, both show better heat transfer performance under the experimental pressure 10.3 kPa. Also, the carrier etched MSS performs better than the plain surface. (3) The controlled experiments prove the frozen carrier etched MSS can acquire a 44% higher average cooling speed (90,437.14℃/min) than the carrier with plain surface. (4) According to the heat transfer process of the frozen carrier, the calculation results of the three-dimensional heat transfer model are in good agreement with the experimental data. (5) The heat transfer across the carriers almost vertically, and less heat transmit from the horizontal direction along the carrier, thus it could be seen as a one-dimensional heat transfer. (6) A new carrier, which etch the same micro structure on the liquid, can decrease the thermal resistant of liquid and improve the average cooling speed 27% compared with the carrier do not etch the micro structure on the liquid side.The research results can provide technical support for practical application.