Study On Characteristics Of Baffled Phase Change Material Water Tank

With the energy constraints and environmental problems,solar energy has became a new hotspot in current research as a clean energy.But when we using solar energy for heating,we always need to use a huge heat storage water tank to store the energy from solar energy absorbers,in order to overcome the disadvantages of solar energy,such as the mismatching between solar energy and heating load,the water tank always too huge to occupy lots of space and then.So to find a new way or a new material to store solar energy has been a new study point in solar energy field.Phase change material is a material which temperature reach phase transition temperature would came to constant,and the heat storage capacity continuous increase,so if we packing PCM into stainless steel box and put it into solar energy water tank with a suitable structure,we could increase the heat savings and maintain the temperature and prolong the heating time.In this research,firstly a combined heating system was built,and chosen 50 ? paraffin as the PCM in solar energy water tank,we put the PCM unit into water tank like baffles to prolong the heating time and increase heat transfer area.And then,through the experimental study on the thermal characteristics of the phase change tank storage,The effects of different plate spacing and water flow on the thermal storage capacity of the water tank under the heating power of 2kw were studied.It is found that the influence of different flow rates on the heat storage capacity is not significant.When the plate spacing is small,the flow resistance increases,and when the plate spacing is larger,the amount of phase change material is less.It was found that the heat storage tank with the 3cm spacing was the best one compared with the other one.It is found that the heat storage characteristics of the heat storage water tank with 3 cm spacing are better than others.When the water tank is in the discharging condition,the fan coil as the end equipment operating under 300m3 / h air volume,Filled with phase change material,the time of discharging mode is longer than ordinary water tank by at least 1h,And the smaller the flow rate is,the longer the discharging time is,If the flow is too large,the phase change material temperature drop relative to the water temperature drop will be delayed.Through the experimental study,the authors established a single temperature phase transition model.Comparing the experimental data with MATLAB,it is found that the difference between the experimental value and the simulated value is within ± 5% under the charging condition,difference within± 10% under the discharging condition,indicating that the experimental results with high accuracy.Finally,we set the inlet water temperature as a constant,using phase change rate,outlet water temperature,heat storage/release capacity and heat storage/release rate to evaluate the performance of PCM water tank.As the results shows,when thickness of the PCM plate,the heat storage/release rate larger,and the ability to maintain the temperature of water is stronger.When the lower of the flow rate,the longer the heat storage or release time,the more fully of heat transfer,and as flow rate increases,the flow rate effect to water tank performance decrease gradually.When the lower of the inlet temperature,longer the time of PCM fully transformation,and as inlet temperature increases,the inlet temperature effect to water tank performance decrease gradually.Within the increase of the latent phase change heat of PCM,the heating storage time increase relative,so when the cost of PCM have large latent heat value have little different with the small one,we could choose the larger one.And then a software with a visual interface was be developed by Visual Stadio,which aims to guide design.