Research On Composite Phase Change Cold Storage Material Of Sodium Sulfate Decahydrate And Its Cold Chain Transportation Application

Phase change cold storage technology can solve the mismatch between cold energy supply and demand in time and space,which plays a key role in cold chain logistics.Phase change cold storage materials,as the core of phase change cold storage technology,can realize low temperature control and seamless linkage in all aspects of cold chain logistics.Sodium sulfate decahydrate(SSD)is a high latent calorific value,widely available,and inexpensive hydrated salt,which can be widely used in the field of phase change cold storage.In this paper,we prepared composite phase change cold storage materials of sodium sulfate decahydrate and applied them to cold chain transportation.The regulatory mechanism of phase change cold storage performance of sodium decahydrate sulfate was elucidated,its performance was optimized,and phase change cold storage materials with high cold storage capacity,high thermal conductivity,and good circulation performance were prepared and realized for cold chain transportation applications.(1)A new method for the preparation of phase change cold storage materials by modified sodium sulfate decahydrate was proposed.A series of sodium decahydrate sulfate-based phase change cold storage materials(SSD-BCKN)were prepared by using SSD as the main raw material and modified with supercooling inhibitor(borax,B),phase separation inhibitor(sodium carboxymethyl cellulose,CMC)and phase change temperature regulator(KCl and NH4Cl).The crystal structure and chemical composition of the sodium decahydrate sulfate-based composite phase change cold storage materials were examined,and it was confirmed that the new composite phase change cold storage materials had good chemical stability.The long time state observation of the samples showed that the CMC effectively suppressed the phase separation of the phase change cold storage materials,in which no phase separation was observed for SSD-BCKN3.The step-cooling curve test showed that the supercooling inhibitor borax significantly reduced the supercooling degree of the phase change cold storage materials.the DSC characterization revealed that the phase change thermoregulator reduced the phase change temperature of the series of composite phase change cold storage materials,among which,the phase change temperature of SSD-BCKN3 was 6.8℃,its melting latent heat and supercooling degree was 97.05 J g-1 and 0.7 ℃,respectively.The application experiment showed that SSD-BCKN3 significantly improved the freshness of strawberries for 48 hours and had the potential for cold chain transportation applications.(2)The strengthening mechanism of the cold storage performance of sodium decahydrate sulfate/expanded graphite composites was elucidated.A series of composite phase change cold storage materials(SBCKN/EG)were prepared by using expanded graphite(EG)loaded with sodium decahydrate sulfate-based phase change cold storage material(SBCKN)to improve its morphological stability and cold conduction properties The physical phase,chemical composition and morphology of the samples were characterized,and it was confirmed that the expanded graphite modulated the microstructure of the composites,and the SBCKN/EG composite phase change cold storage materials had good chemical compatibility and stable morphology.The DSC results showed that the supercooling degree of SBCKN/EG5 with the addition of 5 wt%EG was reduced by 18.93℃ compared with SSD,and its melting and cooling latent heat values were 99.35 J g-1 and 66.39 J g-1,respectively.The thermal conductivity characterization experiments showed that the thermal conductivity of SBCKN/EG5 was 0.43 W m-1 k-1,and its cold energy storage and discharge rate and instantaneous temperature response were significantly improved compared with those of SBCKN.The strengthening mechanism of the cold storage properties of SBCKN/EG composites was elucidated through atomic structure simulations by conducting a study on the morphological stability and cold conduction properties of the SBCKN storage and cooling process with the synergistic strengthening of expanded graphite.Cold chain transportation application experiments show that SBCKN/EG5 has good cold energy storage/release capability.(3)The regulation mechanism of the thermal insulation performance of sodium sulfate decahydrate/silica composites was revealed.Silica(S)was used to modify the SBCKN material and regulate its thermal insulation performance to prepare a series of composite phase change cold storage materials(SBCKN/S).The morphology,crystal structure,and chemical stability of the samples were characterized,and it was confirmed that the chemical compatibility between silica and SBCKN was good,and the physical structure of the new composite phase change cold storage material SBCKN/S was unchanged.DSC experiments showed that the melting phase transition temperature of SBCKN/S3 with 9 wt%silica was 6.45℃ and the latent heat value was 75.93 J g-1.Compared with the original base material SBCKN,the thermal conductivity of SBCKN/S3 was improved to 0.39 W m-1 k-1,which showed better cold energy storage and discharge performance in the cold storage and discharge experiment and transient thermal response experiment.The atomic structure simulation method was used to study the process of silica co-operating with SBCKN putted out cold to extend the holding time,and revealed the regulation mechanism of silica on composite phase change cold storage materials.Cold chain transportation application experiments show that SBCKN/S3 phase change cold storage material shows good low-temperature cold supply capability.Based on the crystal structure and energy storage characteristics of sodium decahydrate sulfate,this paper develops a series of sodium decahydrate sulfate-based composite phase change cold storage materials,proposes a new method to prepare phase change cold storage materials by modifying sodium decahydrate sulfate,elucidates the strengthening mechanism of cold storage performance of sodium decahydrate sulfate/expanded graphite composites,and reveals the regulation mechanism of thermal insulation performance of sodium decahydrate sulfate/silica composites.Strawberries are selected as the object of cold chain transportation,and the research of cold chain transportation application is carried out to establish the judging system of phase change cold storage material application.This paper provides a new composite phase change cold storage material for cold chain transportation and enriches the phase change cold storage theory.