Therocial And Experimental Research On Some Issues For In-Direct Refrigerator

Energy efficiency and noise reduction are the main target for domestic refrigeration appliance (refrigerator, room air-conditioner, etc) research. In-direct refrigerator is popular in developed counties since its automatic defrosting, high volume, multi-function. Comparing with direct refrigerator, lower energy efficiency and higher noise are main challenge to in-direct refrigerator. So, it is necessary to research the energy saving and noise reducing for in-direct refrigerator.Meanwhile, main development method for in-direct refrigerator are combined the experiential and the experimental method. To experiential principles, the reliability is affected by many factors, and the validity is limited. To experimental method, the results are reliable and it is necessary to find out the essential principles for refrigeration equipments. But the experiments normally mean high cost, long duration. Also, it is difficult to get an optimized result by pure experiments. Therefore, model based computer simulation is a good compensation for experiments.The main issues in in-direct refrigerator field, i.e. low energy efficiency and high noise, could be studied by numerical simulation method. The combination of simulation and experiment is an efficiency method for product development and improvement. In this paper, based-on theoretical and experimental method, researched some issues regarding to in-direct refrigerator as following:An experimental rig for frosting and heat transfer character of fin-tube evaporator was design to study the fin-tube heat exchanger.Experimental study was applied to in-direct refrigerator to validate the theoretical model built in this paper, as while as to optimize the structure and performance of the refrigerator.Based on mass and energy equation, a dynamic and distribution parameter model for frosting and heat transfer of fin-tube evaporator was set up. The model included air-side flow and heat transfer module, tube-wall module, refrigerant side flow and heat transfer module, and frost growing module. The model was validated by special experiment.From fundamental theory of heat transfer and thermodynamics, the defrosting model of in-direct refrigerator was established to look for an optimized defrosting cycle time of operating period, which provided a theoretical evidence for the defrosting control strategy.The analytical model of the flow and thermal field, including the enclosure structure and air-duct, fan and evaporator, was established, where the fan was treated as source power of the flow fields with the cooling capacity of the evaporator introduced as source item in energy equation. From above treatments, it was unnecessary to identify the flow and temperature boundary conditions by large quantities of experiments. The dynamic operating process was analyzed based on a specific in-direct refrigerator. By CFD simulation, the performance of this refrigerator was evaluated and the constructive optimized design was provided to improve the cooling capacity, and at the same time to reduce the energy consumption. A fact was found through the study of the radiating heat transfer that radiating process should not be omitted in an in-direct refrigerator.A system simulation model for in-direct refrigerator was established, including evaporator frosting module and duct-fan module. CFD method was used to calculate resistance curve of the air-duct, which makes the theoretical model more practical. The model was validated in a specific refrigerator, and simulation results agreed well with the testing results. Meanwhile, the application of system simulation used in analyzing refrigerator performance was discussed.A CFD noise model of in-direct refrigerator fan blades rotation was established. The aerodynamic noise of axial fan system was estimated and compared with testing result, which provided evidence of noise reduction. Finally, summary of the open issues in this research and further study topics related to this field in future was given.