Study On Heat Storage Performance Of Composite Phase Change Energy Storage Structure Based On Graphite Tailings Preparation

With the rapid development of industrial productions,a lot of industrial solid waste residues are being increased rapidly during the recent years.How to make effective and reasonable use of the industrial solid waste residues has become the problem of common concern around the world.In addition,non-renewable energy is exhausting increasingly,improving energy efficiency and developing renewable energy sources will become the main direction in the field of energy research.Phase change materials have the functions of heat energy storage and thermoregulation control,but single phase change material may be insufficient of lower heat conductivity etc.Therefore,to explore and develop composite phase change energy storage structures by combining phase change materials with porous matrix prepared by the industrial solid waste residues is of great significance and practical value.In this paper,porous ceramic structure was prepared by using graphite tailings,and octadecane-lauric acid/nano copper composite phase change material was developed by octadecane,lauric acid and copper.By using the method of spontaneous melting impregnation,composite phase change energy storage structure was made by combining octadecane-lauric acid/nano copper composite phase change material with the porous ceramic structure of graphite tailings,whose main properties were characterized.The experimental testing system was established to carry out the measurement of heat storage performance.The main research contents are as follows:1.Preparation of porous ceramic structure by using graphite tailings.Porous ceramic structure was prepared by using graphite tailings with the method of adding pore-forming agent and compression molding.The influence of different contents of pore-forming agent and binder on the properties of the porous ceramic structure was analyzed.The selection of bentonite as the binder was not only increased the cohesiveness of the graphite tailings,but also reduced the sintering temperature.The selection of carbon powder as the pore-forming agent made uniform pore size distribution and no residue.The final prescription and the technical conditions were obtained by combining with the results of crystal phase and microscopic analyses of the porous ceramic structure of graphite tailings:the dosage of 74%graphite tailings,the dosage of 20%carbon powder,the content of 6%bentonite,the content of 13%moisture,bone size of 75?m-97?m,heat preservation time of 60 min,molding pressure of 9MPa,sintering temperature of 1125?.2.Preparation and characterization of octadecane-lauric acid/nano copper composite phase change material.According to the mole ratio of 6:4 octadecane was mixed with lauric acid and nanometer copper powder was added to prepare octadecane-lauric acid/nano copper composite phase change material.Its main thermophysical property parameters(including phase transition temperature and latent heat,thermal conductivity coefficient and specific heat)were measured by adopting NETZSCH STA449F3 Differential Scanning Calorimeter and DRE-2C Thermal Conductivity Testing Instrument.The main thermophysical properties were measured as:phase transition temperature of 24.19?,latent heat of 167.2kJ·kg-1,thermal conductivity coefficient of 0.341 W·m-1·K-1,density of 871kg·m-3,specific heat of 871kg·m-3.Its thermal stability was verified by the experiment of multiple storage-exothermic circulations.3.Preparation and characterization of composite phase change energy storage structure The prepared octadecane-lauric acid/nano-copper composite phase change material was heated to a molten state to prepare composite phase change energy storage structure by the method of molten spontaneous impregnation(whose impregnation temperature,immersed time and pressure were respectively 70?,60 min and atmospheric pressure)with the porous ceramic structure of graphite tailings.The main mechanical properties and thermophysical properties were characterized by bending test,X-ray diffraction,SEM and DSC.4.Measurements and analyses of heat storage performance of the composite phase change energy storage structure In order to verify heat storage characteristic of the composite phase change energy storage structure,the experimental testing system was constructed by phase change energy storage testing device,adjustable blower,electric heater with adjustable temperature,pipes and valves.The multiple temperature measuring points were respectively arranged on the surface of the composite phase change energy storage structure,and the composite phase change energy storage structure was put into the phase change energy storage testing device.While the hot air of 50? flowed respectively over the experimental testing system with five different velocities,the process of its heat storage was measured by the thermocouples of multiple temperature measuring points,DH3816 Temperature Testing Analytical System and the computer with the related software.The laws of temperature change of the various measuring points as a function of time at the outlet of the phase change energy storage testing device,on the surface of the composite phase change energy storage structure and the porous ceramic structure could be obtained.The experimental measurement results showed that,the process of heat storage of the composite phase change energy storage structure was composed of the two parts of sensible heat storage and latent heat storage,and its heat storage performance was excellent and could play a role in temperature control.The research work and achievements in this paper can provide a new approach for the integrated utilization of graphite tailings,which will afford a comparatively reliable experiment evidence and technical foundations for the preparation of composite phase change storage structure made by the porous ceramic matrix of graphite tailings.