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This research aims to explore a novel PCM that can satisfy the needs of vaccine cold chain logistics temperature zone (2–8 °C), with decyl alcohol (DA) and lauric acid (LA) chose to be eutectic. Considering the thermal conductivity and leakage of materials, DA-LA/EG composite phase change material (CPCM) with a mass ratio of 12:1 is prepared by the vacuum adsorption method. The thermal properties of DA-LA/EG CPCM are analyzed by DSC, cooling curve, Hot Disk, SEM etc. From the DSC graphs of DA-LA eutectic phase change material (EPCM), it is found that there is difference between the melting temperature and solidification temperature, which is defined as phase change hysteresis. The results indicate that the phase transition temperature of DA-LA/EG CPCM is 2.08 °C, with high latent heat and thermal conductivity of 188.71 J g−1 and 1.7527 W m−1 K−1, respectively. Due to the unique porous structure of EG, the thermal conductivity is 13.75 times higher than that without EG, which leads to the phase transition time shortened by 79.47%. Furthermore, DA-LA/EG CPCM shows excellent cyclic stability and chemical stability after 500 high-low temperature alternating tests. From TGA, the decomposition temperature of DA-LA/EG CPCM is 186.55 °C, higher than the working temperature range. The applicability is demonstrated by using the CPCM into an incubator. Overall, DA-LA/EG CPCM has good application prospects in vaccine cold chain logistics.

Being a novel energy storage medium, ice slurry has the advantage of good fluidity, high latent heat and heat transfer efficiency, which has a broad application prospect. In this work, the ice making characteristics of different types of additives (MgCl2, ethylene glycol and magnetic iron oxide nanoparticles) in a binary ice system by vacuum flash evaporation under the action of solid adsorption were experimentally investigated. Subcooling, flash rate, ice packing factor, latent heat and thermal conductivity were measured to evaluate the performance of ice production. The results showed that 0.075% wt of iron oxide nanoparticles and 1% wt of MgCl2 are more suitable to be used as additives for binary ice preparation than ethylene glycol, with the former outperforming the latter. Under optimal conditions, compared with pure water for ice making, the subcooling degree of iron oxide nanofluid was reduced by 55.80%, and the thermal conductivity and ice packing factor were increased by 98.80% and 54.22%, respectively. The subcooling degree of the MgCl2 solution was reduced by 37.52% and the ice packing factor was improved by 59.51%. Meanwhile, DSC tests showed that the latent heat of the nanofluid was almost independent of the nanoparticle concentration. However, the increase of MgCl2 solution would cause the decrease of latent heat. In addition, high concentrations of additives can inhibit ice crystal nucleation and growth, but a certain concentration of additives facilitates ice crystal refinement in vacuum ice making process, which is conducive to the transportation of ice slurry.

As a new type of cold storage medium, binary ice has the advantages of high-density energy storage, fast cooling rate, good fluidity and high thermal efficiency, which bring it broad application prospect. Compared with other ice making methods, the vacuum flash preparation of binary ice has the benefits of high efficiency, simple equipment and convenient operation. In this paper, the theoretical and experimental research status of binary ice preparation by vacuum flash has been introduced in detail. To better understand the heat and mass transfer mechanisms of binary ice vacuum preparation process, this paper also reviewed the influence of superheat, waterfilm height and pressure changes on the heat and mass transfer during vacuum flash evaporation. Finally, according to the current research situation, future research trends for the preparation of binary ice by vacuum flash are prospected.

Traditional equilibrium thermodynamics can only solve a few equilibrium processes composed of continuous stable equilibrium states. However, the vacuum flash evaporation process is a typical unsteady process. The study of non-equilibrium thermodynamics of the two-phase flow model is helpful to improve our understanding of the basic law of the flash evaporation process. Based on the theory of non-equilibrium thermodynamics, the flash chamber in the vacuum flash ice making system was studied in this paper, and the possibility of non-equilibrium steady state evaporation with superheat was obtained. The chemical potential difference between liquid water and water vapor under non-equilibrium steady state conditions was determined, and the corresponding evaporation entropy was calculated. It is shown that the results obtained by equilibrium thermodynamics are only related to the temperature difference, while the results obtained by non-equilibrium thermodynamics are not only related to the temperature difference, but also the state of the evaporation process. This is because non-equilibrium thermodynamics considers the cooling of liquid water and the evaporation of water vapor as a whole, taking into account the interaction between the two processes. However, the traditional equilibrium thermodynamics theory divides the steady state evaporation process into two independent processes and ignores the influence of each other.

Form-stable phase change material (PCM) has become the preferred material in the field of thermal management. However, the practical application of form-stable PCM is restricted by low thermal conductivity, strong rigidity, and complicated production. In this work, a facile strategy is successfully proposed to prepare a novel form-stable PCM, which is composed of paraffin (PA), styrene-ethylene-propylene-styrene (SEPS), and expanded graphite (EG). Here, SEPS acted as supporting material not only prevents leakage of liquid PA but also provides thermal-induced flexibility property. Moreover, EG takes a positive part in improving heat transfer and shape stability. The thermal conductivity and enthalpy of PA/SEPS/EG composite are measured as high as 1.340 W m−1 K−1 and 207.02 kJ kg−1, respectively. Simultaneously, the composite PCM performs excellent leakage-proof and realizes good flexibility under external force without fracture. It is worth mentioning that the flexible PCM can reduce thermal contact resistance between battery and PCM under steady state. As a result, the battery temperature could be maintained about 43 °C by PA/SEPS/EG composite in the form of interference fit. Therefore, these results imply that the flexible composite PCM with excellent integrated properties has promising prospects for applications in thermal management.

In order to explore the effect of different concentrations of additives on aqueous solution in vacuum ambient, this paper uses molecular dynamics simulation method to study different concentrations of magnesium chloride (MgCl2) aqueous solution, ethylene glycol aqueous solution and nano iron oxide (nano-Fe3O4) aqueous solution. The radial distribution function of atoms, the water molecules’ self-diffusion coefficient and the type and number of hydrogen bonds are analyzed in detail. The dynamic behavior between water molecules and chloride and alcohol molecules in the solution is revealed. The results show that the additives affect the crystallization of the solution by inhibiting the self-diffusion rate of water molecules, and the iron oxide nanoclusters exhibit the most obvious behavior. Meanwhile, the added additives can also restrain the formation of hydrogen bonds between water molecules in solution. This suppresses the hydrogen bonds between two water molecules. At the same time, it reduces the diffusivity of water molecules. These effects weaken the tendency of water molecules to migrate to the nucleus, and can curb the nucleation and growth of ice crystals in the aqueous solution to a certain extent. This research will provide reference value in the selection of ice-making working fluid. Nano-iron oxide has better performance than MgCl2, and glycol solution is not conducive to vacuum ice making.