Preparation Of Electrocaloric Film With Evaporation Method And Its' Performance Study

The electrocaloric effect refrigeration technology is a new type of pollution-free green solid refrigeration technology with great potential to replace the traditional vapor compression refrigeration technology.The electrocaloric material is the base for the application of electrocaloric refrigeration.In the work,the solution evaporation method is used to prepare(P?VDF-TrFE?electrocaloric polymer film.This method is low in cost and simple to operate.It is suitable for laboratory membrane production.The film making process and the properties of the prepared film are studied,and a new type of electrocaloric effect refrigeration device is proposed based field synergy theory.The main research work and conclusions are as follows:?1?The effect of different preparation process conditions on the preparation of P?VDF-TrFE?electrocaloric film was studied.By comparing and analyzing the thickness average deviation percentage,remaining solvent ratio,micro-morphology,crystallinity and other aspects of electrocaloric film,the film preparation was finally obtained the best process conditions.The results show that under the process conditions of mass concentration of 2%?7%,evaporation temperature of 60?,evaporation time of 24 h,and annealing heat treatment temperature of 140?,the thickness can be prepared within 100?m,the average thickness deviation percentage is 3%,and the residual solvent ratio is about 6%,and the ideal P?VDF-TrFE?electrocaloric polymer film with high crystallinity and good surface micro-topography.?2?The mechanical properties,electrocaloric properties,dielectric properties and thermal stability properties of P?VDF-TrFE?electrocaloric film prepared by solution evaporation method are studied and analyzed.The results of performance research are as follows:the best performance of the crystallinity inside the film,the polarity,the electrocaloric will appear when the annealing temperature is 140?.The maximum polarization strength and the residual polarization strength are 11.02?C?cm^-2 and6.74?C?cm^-2,the grains are fully grown,the grains are packed closer,making the intermolecular force is stronger,so the film has the largest elastic modulus and the best mechanical properties.As the electric field strength increases,the polarization strength increases accordingly,but when the electric field strength reaches 200 MV?m^-1,the hysteresis loop of the film has already approached saturation,and continuing to increase the electric field strength may cause the film breaks down,so the electric field strength of its operation should be controlled within 200 MV?m^-1;as the switching frequency of the electric field increases,the dielectric constant of the electrocaloric film gradually decreases,and the dielectric loss first decreases after the increase,so the electric field switching frequency should not be too large,should be controlled within1000 k Hz.In terms of thermal stability,P?VDF-TrFE?electrocaloric film begins to thermally decompose above 400?,so its working environment temperature should be no more than 400?.?3?According to the characteristics of the electrocaloric effect of the existing electrocaloric materials,combined with the field synergy principle,a new type of electrocaloric effect refrigeration device solution is proposed.The device has a modular structure and can be expanded by superimposing unit modules in three directions according to actual application requirements.By superimposing in different directions,the temperature span and cooling power can be improved.