Study On Cool Storage And Discharging Characteristic Of Direct-contact Cool Storage Device At Conventional Air-conditioning

Recently, with the development of national economy, occupation of the central air-conditioning system is lager and lager, whose electricity consumption exceeds40%of total construction energy. In the field of refrigeration and air-conditioning, cool storage air-conditioning technology is one of the most efficient ways to deal with the problem of peak-valley distance in electricity grid. Nowdays, the ice cool storage air-conditioning is most widely used in cool storgae air-conditioning. In the process of making ice, heat exchange is mostly via refrigerant or secondary refrigerant touching to wanter through coil. Coil not only makes structure of cool storage device more complex, increase the cost, and arouse additional thermal resistance in the process of heat exchange. In the system of using secondary refrigerant, in order to making ice successfully, it needs indirectly exchange heat twice, which greatly reduces the heat exchange efficiency of total system. In addition, low evaporating temperature of ice cool storage unit leading to a relative lower refrigeration coefficient to common air-conditioning conditions. It is pretty difficulty to transform the existing common air-conditioning system to the ice storage air-conditioning system due to the large variation of making ice condition and air-conditioning condition. Therefore it is significant to improve the heat exchange efficiency of cool storage system and research suitable PCM for conventional air-conditioning.This article applies the direct-contact heat exchange technology to the conventional air-conditioning cool storage system. It choose the organic material, praffin, as cool storage material, water, as secondary refrigerant, making them directly contact and exchange heat in cool storage device. Major research works and results are following:(1) The model of solidification and melting of PCM droplet are established to research the influence of initialized temperature to its solidification and melting process, phase interface movent pattern insiede droplet, distribution of temperature, and changes of liquid phase ration. Results indicate:temperature have a great influence on solidification and melting.(2) Regarding to the structural features of cool storage device and heat transfer characteristic of multiphase flow, a model of cool storage device is established to simulate the process of cool storage or discharging, research the influence of PCM inlet temperature and flow, secondary refrigerant inlet temperature and flow to cool storage characteristic; research the influence of secondary refrigerant inlet temperature and flow, initial temperature to discharging characteristic. Simulated results suggested that:in the process of cool storage, the total cool storage volume is direct ratio to the temperature and flow rate of PCM, flow rate of the secondary refrigerant while ti is inverse ratio to inlet temperature of the secondary. In the process of discharaging, the total discharging volume is direct ratio to inlet temperature of PCM, inverse ration to initial temperature of cool storage device.(3) A small visual direct-contact cool storage experiment device is set up to research its cool storage and discharging characteristic. This article studied the influence of the nozzle diameter, inlet temperature and flow rate of secondary refrigerant to cool storage device characteristic, finally, compared the simulated results with experimental results. It shows that there is some error between those two, while the overall trend is consistent.The results from simulation and experiments in this article has guiding function in some degrees to increase thermal efficiency of air-conditioning system and direct-contact heat exchange technology application in cool storage air-conditioning.