| Phase change material(PCM)refers to those thermal storage materials whose state of matter will be changed in the release or absorption of large amounts of heat storage material.The temperature of PCM is constant approximately while the course of phase change and the PCM has been studied extensively in the building and other areas.The solar-energy water tank is an energy saving device commonly used in our daily life.This device supplys our domestic hot water(DHW)which meet our request for the water temperature through the heating role of the solar collectors.However,the water has only sensible heat storage while the storage and release course of the heat and the heat storage density is low.The DHW tanks tend to be larger.Combining the phase change material with the DHW,using the latent heat of the PCM in the phase change process can obviously increase the storage density of the heat storage tank and reduce the volume of the water tank,which has certain advantages.Firstly,a novle design idea of DHW that encapusled two kinds of PCM has been proposed in this study.And the basic structure of the DHW was determined by the simulation calculation.Secondly,sodium acetate trihydrate and lauric acid,were selected as the PCM in this study.And according to the particularity of sodium acetate trihydrate properties,appropriate nucleating agent and thickening agent have been determined the in this experiment,also,thermal physical property testing have been performed on the chosen of PCM.Thirdly,PCM thermal storage water tank test system was built in Tianjin University.Through the control to the phase change module,flow,temperature,a variety of operating condition experimental test of heat storage water tank have been proceeded.At last,the experimental data accuracy and the energy efficiency of the water tank have been analyzed based on the law of conservation of energy.The test data about the thermal storage process show that,the needed time to storage thermal is shorter for lower PCM compared with higher PCM.And that means the time needed to complete the accumulation of heat for this water tank is shorter than the tank using the same PCM.The test data about the thermal release process show that,the influence of flow on three kinds of water tanks,which are 1#,2#,3#(PCM account for 0%,11.12% and 19.17% of the water tank volume respectively)are basically the same.The heat release of the tank gradually reduce with the increase of flow rate.On the condition of initial temperature and the heat release water flow rate 70? and 5L/min,the increase of PCM can obviously improve the heat release of the water tank.Compared with 1#,the heat release of 2# and 3# increased 24.82% and 34.05% respectively.Intermittent mode of heat release can make up the defect of the continuity mode and the heat release can increase 4.7% and 7.4% maximumly respectively.Qualitative analysis on the latent heat utilization of the PCM have been proceeded and the results show that compared with 2#,3# holds a higher PCM latent heat utilization and has obvious energy-saving advantages.Verification on the accuracy of the test data show that the data error is about 3.1% to 4.6%.And analysis on the energy efficiency of the tank encapusled 19.17% PCM(volume fraction)show that the increase of the thermal storage is 5805.6kJ,and the energy-saving rate is about 34.05%. |
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