Pilot Study Of The Large Frozen Equipment And Efficient Evaporator Heat Transfer Technology

In the last 70 years, developed countries have accumulated abundant experience in the research and manufacturing of quick-freeze equipment. The technology of quick-freeze equipment is growing mature day by day. Domestic manufacturers of quick-freeze equipments also wish to manufacture high-efficiency, energy saving and economical quick-freeze equipments, but they could not make it because of the lack of research in relevant fields. Therefore, it's very important to strengthen the theoretical and experimental research in these fields, and to develop high-efficiency quick-freeze equipment with independent intellectual property rights.The project of "Research and Development of the Technology and Equipments Used in the Deep-processing of Agricultural Products" is a "National 'the 10th Five-year Plan' Key Technological Special Project". Take the opportunity of this project, theoretical and experimental researches on the high-efficiency evaporator used in a large quick-freeze equipment have been done. The main work of experimental research is as follows:(1) Compare and analyze the influences of structural parameters on the heat transfer coefficient of an evaporator. The calculation results show that, under non-freezing conditions, the structure possessing the highest heat transfer coefficient is the one with circular fins, equilateral-triangle arranged small tubes and varying fin-spacing.(2) Further analysis indicates that, under freezing working conditions, the structure with continuous unitary waved fins, equilateral-triangle arranged tubes and varying fin-spacing has the highest heat transfer coefficient. A test evaporator with this structure has been manufactured to be tested. The heat transfer coefficient obtained is very close to the calculation result.(3) Considering the influence of air resistance on the fluidization of materials to be frozen, structure with integral waved fins, foursquare arranged tubes and varying fin-spacing has been adopted. Cooperating with the manufacturer, an evaporator with this structure, which has the capacity of freezing 4 tons of green sword beans per hour, has been made. The auxiliary equipments have also been designed to form a complete set of freezing system. Compared with current quick-freeze equipments of the same type, this equipment decreases by 40% or above in size and by 30% in energy consumption.(4) Based on the Visual C++ programming environment, a program for calculating the heat transfer coefficient of an evaporator has been developed. In this program, the user only has to input the structural type of the evaporator, the working condition parameters, and the structural parameters, and then the heat transfer coefficient of the evaporator will be obtained. It has been proved that the result of this program is in good agreement with the test result. So this program is of certain value.