Cold Storage Material Research Articles

Urea-aided phase change thermal energy storage performance regulation for thermal management

Organic phase change cold storage materials show significant potential in various fields, including cold chain transportation, food and drug preservation, and battery thermal management. However, most organic phase change cold storage materials struggle with issues like difficult temperature control and flammability, which severely limit their application and development. In this study, by physically blending a modulated urea solution and alcohol with the polyethylene glycol lauryl ester (PLE), and adjusting the mass of urea and alcohol, a series of samples are prepared. Detailed characterization and analysis reveal that the prepared phase change materials (PCMs) possess excellent cold storage properties. These materials achieve precise control of melting temperatures ranging from −13.42 to −3.80 °C, with a maximum latent heat of melting of 85.12 J/g. Interestingly, this study reveals that seven groups of samples exhibit flame retardant effects. These properties are critical for enhancing the safety and efficiency of the materials in practical applications. This innovative approach not only addresses the temperature control and flammability issues but also expands the potential use of PCMs in various industries. Therefore, this study offers an effective method for developing advanced phase change cold storage materials, contributing to technological advancements in thermal management.

Performance of a CO2-based mixture cycled transcritical pumped thermal energy storage system

The transcritical CO2 cycle has the characteristics of high power density, high stability and high thermal energy transfer efficiency. It has been employed in pumped thermal energy storage system and ice slurry often serves as the cold storage material. However, ice slurry is not an optimal choice for cold storage due to its huge volume and high cost. In this study, an innovative transcritical pumped thermal energy storage system cycled with CO2-based mixtures is proposed. Temperature of the CO2-based mixture changes during the phase transition process, which means that simple two-tank cold energy storage arrangement with fluid heat materials is feasible to achieve the phase change of working fluid. R32, R161, propane, butane and pentane are screened to mix with CO2, respectively. Multi-parametric analysis of proposed system is conducted to assess its technical and economic performance. The Monte-Carlo method is employed to investigate the system uncertainty. Results display that for a 10 MW/8h scale the system cycled with CO2/R32 has the minimum levelized cost of storage of 0.1655 $/kWh, with a round trip efficiency of 65.51 %. The optimal levelized cost of storage is 0.1678 $/kWh, 0.1801 $/kWh, 0.1781 $/kWh and 0.1801 $/kWh for R161, propane, butane, and pentane, in sequence. The system investment cost decreases as the operating durations increase. The mean levelized cost of electricity and energy capacity cost are separately reduced by 29.35 % and 48.24 % as the installed capacity is extended from 10 MW to 10000 MW.

Research on Phase Change Cold Storage Materials and Innovative Applications in Air Conditioning Systems

Phase change cold storage materials are functional materials that rely on the latent heat of phase change to absorb and store cold energy. They have significant advantages in slight temperature differences, cold storage, and heat exchange. Based on the research status of phase change cold storage materials and their application in air conditioning systems in recent years, this paper provides an overview of the materials and their enhanced research progress. It summarizes the types of phase change cold storage air conditioning systems, optimization schemes, and system applications. This paper also identifies the current issues in phase change cold storage air conditioning and discusses the development trends in cold storage materials and air conditioning systems. It anticipates that future advancements will focus on composite phase change cold storage materials and low-energy consumption intelligent phase change cold storage air conditioning systems in steam compression using spherical capsules and concave–convex plate PCM.

Efficient utilization of cold energy enabled by phase change cold storage brine gels with superior thermophysical properties towards biochemical reagent cold chain

Phase change cold storage, as an emerging cold chain method of maintaining a low-temperature environment and effectively ensuring the quality of biochemical reagents, is extensively utilized because of its benefits of high energy density, low cost, energy conservation and environmentally friendly mode. However, the low thermal conductivity of working medium affects its cold charging/discharging rate and operating efficiency. Meanwhile, the high leakage characteristic in the phase change process leads to a decrease of cold storage capacity and contamination of items. This work proposes the efficient utilization of cold energy enabled by leakage-free phase change cold storage brine gels with extraordinary high thermal conductivity towards biochemical reagent cold chain. Phase change thermal storage gel is prepared by confining brine in the sodium polyacrylate‑calcium alginate network and porous adsorption of expanded graphite. The prepared materials present leak free characteristics and almost 100% mass retention rate. Expanded graphite addition enables the thermal conductivity increase from 0.542 W m−1 K−1 to an extremely high value of 2.766 W m−1 K−1 (an increase of 510%). The enthalpy value of the cold storage brine gel is as high as 144 Jg−1, stably releasing cold at around −24 °C. By regulating the distribution of cold storage working medium, the minimum temperature difference inside the apparatus can be reduced from 6.7 °C to about 1 °C. Finally, performance-enhancing phase change cold storage materials and apparatus in the cold chain of biological reagents is fruitful, effectively providing a long-lasting and uniform low-temperature environment.

The effect of anti-agglomerant tween on the thermal and rheological properties of TBAF semi-clathrate hydrate slurry used for cold storage systems

Hydrate, as a phase change cold storage material, can form the slurry with certain fluidity, enabling convective heat transfer during both the heat absorption and heat release stages (cold storage or refrigeration), with high heat transfer efficiency. However, high viscosity and significant flow pressure losses are the principal challenges limiting its advancement. The paper selected four non-ionic surfactants as hydrate anti-agglomerants (Tween 20, 40, 60, 80) and utilized DSC to examine their effects on the thermal properties of TBAF semi-clathrate hydrate slurry at three theoretical hydrate concentrations (with mass fraction of 0.60, 0.70, and 0.80). Additionally, it measured the viscosity variation during the endothermic dissociation stage of the TBAF hydrate slurry and calculated the flow pressure losses in hydrate slurries within various pipe diameters. The results revealed that the presence of Tween increased the hydrate growth within the slurry, resulting in a higher available phase change enthalpy. Tween 80 demonstrated the most significant increase in enthalpy increasing effect, with an available phase change enthalpy ranging from 128.08 to 170.03 kJ/(kg·slurry) and an increase in enthalpy of 52.14 % to 91.62 %. For TBAF hydrate slurries with the theoretical hydrate mass fraction of 0.60, the addition of Tween 20 or Tween 80 significantly reduced viscosity, dropping to between 57.6 mPa·s and 116 mPa·s, and reducing viscosity by 43.4 % to 71.9 %. Furthermore, most flows with anti-agglomerants were in the laminar regime. The addition of Tween 20 and Tween 80 achieved the maximum reduction in flow pressure loss per unit length, with the highest reduction being 80.2 % (0.11 kPa/m) and 71.1 % (0.15 kPa/m), respectively. Both the phase change enthalpy of the hydrate and the viscosity of the hydrate slurry impacted the flow pressure drop within pipes. Increasing phase change enthalpy and reducing viscosity are effective strategies for mitigating flow pressure drop.

Preparation and properties of gel-type low-temperature phase change materials

In the context of the dual‑carbon target, there is a high emphasis on the energy efficiency of traditional mechanical cold storage systems with significant power consumption. Additionally, the implementation of time-of-use electricity pricing has played a crucial role in driving the rapid advancement of energy storage technology. The application of energy storage technology in cold storage can significantly reduce the energy consumption of the refrigeration system, save operating costs by shifting peak demand to valleys, and reduce start and stop frequencies. Therefore, studying phase-change materials with high latent heat, low cost, and good performance for cold storage is of great practical application in cold storage. The paper developed four types of gel-type phase-change cold storage materials with high latent heat, low cost, and good cycle stability. These materials mainly consist of NH4Cl, KCl, and deionized water. The phase transition temperature ranges from −18 to −21 °C, the latent heat of phase change is approximately 260 to 289 J/g, and the thermal conductivity ranges from 0.58 to 0.60 W/(m·K), which can meet the cooling demand of cold storage facilities. Furthermore, by comparing the phase transition temperature, latent heat value of phase change, and cyclic stability, a gel-type PCM with good comprehensive properties was selected for corrosion and corrosion inhibition studies with five common metal samples in welded and non-welded forms. The results showed that material B2 had slight corrosion on 1060 aluminum, 6061 aluminum, and 304 stainless steels, but no obvious corrosion phenomenon was found on 316 stainless steels. The corrosion rate of the material on red copper was the highest, and the corrosion was too strong. In addition, the corrosion of welded parts is more serious than that of non-welded parts, and the welding points are more susceptible to corrosion. Adding the corrosion inhibitor BTA to material B2 can reduce the corrosion rate of red copper by more than 94 %.

Hectorite aerogel stabilized NaCl solution as composite phase change materials for subzero cold energy storage

Inorganic phase change cold storage materials have garnered significant interest in cold chain transportation due to their high energy storage density. Nevertheless, practical applications have been hindered by inherent limitations such as high supercooling and susceptibility to phase separation. To address these challenges, this study devised 3D-Hectorite/sodium chloride (NaCl) composite phase change cold storage materials by utilizing 3D-Hectorite aerogel to adsorb NaCl solution, effectively mitigating the issue of phase separation common in such materials. Additionally, various concentrations of nucleating agents such as SrCl2·6H2O, borax, and diatomite were introduced for step cooling curve tests, establishing 0.03% diatomite as the optimal concentration for nucleation, reducing the supercooling of the NaCl solution to 1.1 °C. The results showed that the latent heat and thermal conductivity of 3D-Hectorite/NaCl were 215.30 J/g and 0.6315 ± 0.013 W/mK, respectively. The phase transition temperature could be adjusted in the range of -33~0 °C by changing the concentration of NaCl to meet the different temperature requirements. Furthermore, exceptional cyclic stability was observed even after subjecting the material to ten dissolution-solidification cycles. Analyzing the temperature change of the air inside the insulation bag showed that, compared with ice, 3D-Hectorite/NaCl can be applied to meet lower cooling temperature requirements, demonstrating good prospects for its application in cold chain transportation.

Preparation and Performance Study of n-Undecane Phase Change Cold Storage Material.

With the fast development of the cold chain transportation industry, the traditional refrigeration method results in significant energy consumption. To address the national call for energy saving and emission reduction, the search for a new type of energy storage material has already become a future development trend. According to the national standard GB/T28577 for the classification and basic requirements of cold chain logistics, the temperature in frozen logistics is typically below -18 °C. In this study, n-undecane with a phase change temperature of -26 °C is chosen as the core material of microcapsules. Poly(methyl methacrylate) is applied as the shell material, with n-undecane microcapsules being prepared through suspension polymerization for phase change cold storage materials (MEPCM). Using characterization techniques including SEM, DSC, FTIR, and laser particle size analysis, the effects of three types of emulsifiers (SMA, Tween-80, Tween-80/span-80 (70/30)), SMA emulsifier dosage, core-shell ratio, and emulsification rate on the thermal performance and micro-surface morphology of n-undecane/PMMA microcapsules were studied. The results indicate that when comparing SMA, Tween-80, and Tween-80/span-80 (70/30) as emulsifiers, the dodecane/PMMA microcapsules prepared with SMA emulsifier exhibit superior thermal performance and micro-surface morphology, possessing a complete core-shell structure. The optimal microstructure and the highest enthalpy of phase change, measuring 120.3 kJ/kg, are achieved when SMA is used as the emulsifier with a quantity of 7%, a core-to-wall ratio of 2.5:1, and an emulsification speed of 2000 rpm. After 200 hot and cold cycles, the enthalpy of phase change decreased by only 18.6 kJ/kg, indicating the MEPCM thermal performance and cycle life. In addition, these optimized microcapsules exhibit favorable microstructure, uniform particle size, and efficient energy storage, making them an excellent choice for the refrigeration and freezing sectors.

Experimental study on the cooling performance of medical protective clothing coupled with phase-change cold storage materials

To solve the problems of poor cooling and moisture permeability of the normal medical protective clothing. A scheme of coupling the phase change cold storage material 1-dodecanol to normal medical protective clothing was proposed. Then the effect of phase change cold storage material on the cooling performance of the normal medical protective clothing internal microenvironment was studied under different conditions. The results showed that compared with normal medical protective clothing, when frontline medical workers wore the phase change medical protective clothing for light labor at 24℃ of the chamber temperature within 1 h, the temperature fluctuation can be effectively reduced by 30 %. One piece of phase change materials package was set up in the head, arm and leg, respectively. And four Phase change materials packages were set up in the chest and back, respectively. The test results showed that the internal temperature of the Phase change medical protective clothing could be sustained reduction of 8 %. The internal relative humidity increased by about 21 % compared with the normal medical protective clothing. The thermal comfort of the MPC was improved by 62.55 %, 26.43 % and 6.37 % for the head, back and chest, respectively. The remaining parts should be considered for future work.

Fabrication of poly(vinyl alcohol) foam/gel composite used for cold storage by combing molding foaming and freeze-thawing technologies

Ice, the widely used low-temperature storage material, plays an important role in the short-time cold chain transportation. To avoid water leakage caused by ice melting, special encapsulation is needed, but inevitably leads to the single shape and the poor contact between ice and the cooled object. It is urgent to develop a new type of leakage-proof cold storage material. Accordingly, in this paper, by combing the technologies of molding foaming and freeze-thawing, a novel cold storage material containing poly(vinyl alcohol) (PVA) carrier foam and PVA gel was fabricated. PVA carrier foam mainly provided the strength foundation, while PVA gel locked the absorbed water. With the addition of 7.0 wt% PVA gel into PVA carrier foam, denser and uniform cells were formed, endowing the foam/gel composite with good shape retention. Even after 500 times’ cyclic compression, the compression curve of the composite still coincided with the original one. The further introduction of 2.0 wt% NaCl into PVA gel enhanced the cold storage effect of the composite, i.e., the temperature in an incubation box could reach −2.5 °C and be maintained for 16 h. This novel PVA foam/gel composite was expected to be used as cold storage material for cold chain transport, and thus broadening the practical application of PVA.

An Experimental Study on the Influence Solution Concentration and Nano-Additives on Cold Storage Performance of Tetrabutylammonium Bromide

Tetrabutylammonium bromide (TBAB) is considered a promising alternative cold energy storage material. Due to the high dissociation heat of phase transition at an atmospheric pressure of 278–293 K, which reaches 200–500 kJ/kg, this substance is considered an effective cold energy storage medium for air conditioning systems. In this paper, the cold storage crystallization process of TBAB solution with different concentrations was tested by conducting experiments and the phase transition’s temperature and latent heat were measured. Finally, the growth characteristics of TBAB hydrate crystals with different concentrations (10%, 20%, 30% and 40%) were analyzed. Considering the cold storage temperature, phase transformation temperature and latent heat, the cold storage effect is the best when 40% TBAB solution is used. Although single substance phase change materials have a long service life, they have problems with low thermal conductivity and high undercooling. Therefore, researchers usually improve the performance of phase change materials by adding other auxiliary materials, thereby enhancing their application prospects. Among these auxiliary materials, adding nano additives to phase change materials can significantly improve latent heat, thermal conductivity and nucleation ability, while also reducing undercooling. Therefore, we studied the influence of different nano-additives (Al2O3, SiC, TiO2 and ZnO) on phase change materials. The composites with excellent properties were screened by cooling step cooling curve and differential scanning calorimeter (DSC). Compared with pure TBAB solution, the phase transition latent heat of the composite phase change materials (PCMs) prepared by adding nanoparticles were significantly increased. The results show that adding nano-SiC into 40% TBAB solution can obtain better performance. This work not only provides reference for the further research, but also a sight to design the phase change materials for the application of new phase change cold storage materials.

Design and investigation of cold storage material for large-scale application in supercritical compressed air energy storage system

The compressed air energy storage is widely studied as promising large-scale energy storage technology. This study focus on the design and investigation of cold storage material for large-scale application in supercritical compressed air energy storage system. Different kinds of cold storage materials for supercritical compressed air energy storage system are comparatively analyzed at first, and the sodium chloride is selected as the suitable cold storage material for supercritical compressed air energy storage system. Meanwhile, the thermal and mechanical properties of suitable sodium chloride particle are measured. The results show that the density of sodium chloride particle is 2.1589 g/cm3. The average specific heat and thermal conductivity of sodium chloride particle are 0.81 J/(g·K) and 5.8576 W/(m·K) in the test temperature range. In addition, the average values of Mohs hardness and Vickers hardness of processed sodium chloride particles are 3 Mohs and 11.7 HV, respectively. The maximum compressive strength of sodium chloride samples tested at −196 °C and 20 °C are 6.25 MPa and 24.45 MPa, respectively. Furthermore, the abradability of sodium chloride particles are tested, the mass loss rate of sodium chloride particles is 0.11 %. The cold storage performance of the designed and processed sodium chloride particle cold storage materials is numerically simulated. The average temperature of sodium chloride particles gradually decreases from 293.15 K to 119.26 K, which can storage 37,128.57 kJ cold energy in total. This work can provide basic data for the further cold storage material research of supercritical compressed air energy storage system.

Production of ternary organic phase change material combined with expanded graphite and its application in cold chain transportation

Based on the temperature range of medical and food logistics (0 ∼ 8℃), Developed a cold storage material consisting of tetradecane, capric acid, and dodecanol, known as tetradecane-dodecanol-decanoic acid material (TDDA). The latent heat transition temperature and thermal conductivity of the resulting TDDA were determined as 258.3 J/g, 1.1 °C, and 0.201 W/(m·K), respectively. TDDA/EG was then obtained by adding expanded graphite (EG) to improve thermal conductivity and prevent leakage. The resulting TDDA/EG exhibited excellent cycling stability after 500 thermal cycles. The temperature change of vaccines in the cold storage box was analyzed through simulated body fluid cold storage box experiments. The average cold preservation time in the cold storage box with TDDA/EG material lasted 37.8 h, a value 50.4-fold higher than that of the cold box without TDDA. Overall, TDDA/EG phase change cold storage materials have good application prospects for temperature-sensitive products in cold chain logistics, such as vaccines.

Emerging phase change cold storage gel originated from calcium chloride hexahydrate

With the growth of human demand for cold energy, phase change cold storage technology has received widespread attention, and phase change cold storage materials as its core need a breakthrough. In this study, a phase change cold storage material suitable for cold chain transportation with CaCl2·6H2O as the main system was successfully prepared. The synergistic mechanism of phase change temperature regulation of CaCl2·6H2O by urea and NH4Cl was explored, and the subcooling phenomenon was overcome by adding SrCl2·6H2O to prepare the phase change cold storage material matrix CUNS3. Based on this, hydrophilic fumed silica and titanium dioxide nanoparticles were added to overcome the problems of phase separation and low thermal conductivity of CUNS3, and both were used creatively to slightly regulate its phase change temperature, thus optimizing the latent heat of phase change. The melting phase change temperature of the gel-like CUNS3-FS5-TDN2 synthesized was adjusted to 8.15 °C, and the latent heat of phase change was optimized to 93.80 J g−1, with a thermal conductivity 25.3 % higher than that of CUNS3-FS5, and the excellent phase change characteristics were maintained after 500 cycles. Finally, the fruit storage experiments showed that CUNS3-FS5-TDN2 was valuable for practical cold chain transportation applications.

Study on coupling of expanded graphite and modified calcium chloride hexahydrate phase change cold storage material

Study on coupling of expanded graphite and modified calcium chloride hexahydrate phase change cold storage material

Analysis of the possibilities of increasing the energy efficiency of absorption refrigeration appliances through the use of refrigerating accumulators

One of the most important tasks of modern society is the solution of environmental and energy problems in power engineering and, in particular, refrigeration technology. At the same time, in the field of artificial cooling systems, it is necessary to solve the problems of reducing the impact on both the ozone layer and the greenhouse effect. An effective approach here can be absorption refrigeration systems with a natural working fluid (water-ammonia solution), which does not adversely affect the environment. For the effective use of absorption refrigeration systems, it is necessary to solve the problems of increasing their energy efficiency, in particular, through the use of cold accumulators. Thus, the object of research is absorption-type cooling systems with cold accumulators.
 The paper analyzes cold accumulators with different physical nature. It is shown that melting substances can be the most effective for solving problems of low-temperature cooling. An analysis of the thermal scheme of an absorption freezer of the «chest» type, which is the most problematic in terms of providing cooling modes at a level of (–18)–(–24) °С, was carried out. Optimization thermal calculations for typical absorption freezers up to 200 dm3 have been performed. It is shown that when the chamber is initially loaded with a product at an ambient temperature, the cooling capacity of the installed absorption refrigeration units is not enough – no more than 50 % of the required one. For an absorption freezer of the «chest» type, the most suitable cold-storage materials are a eutectic aqueous solution of sodium chloride or propylene glycol, since these solutions have the desired melting point of the order of –18 °C and a fairly high melting heat. The result of optimizing the weight and size characteristics of the internal volume of the absorption freezer is the following recommendations:
 – the optimal size of wire baskets for placing products is 315´370´240 mm;
 – the gaps between the basket and the cabinet wall, as well as between the baskets themselves, should be 10 mm to ensure normal convection conditions;
 – it is not advisable to place fans inside the volume of the freezer at this stage, since the freezing time is reduced by a maximum of 30 %, but this results in additional heat generation, energy consumption and increases the shrinkage of the products stored in the chamber.

Preparation and stability analysis of glycine water-based phase change materials modified with potassium sorbate for cold chain logistics

Organic water-based phase change material (PCM) shows great potential for cold chain logistics below 0 °C. However, its poor stability limits its application. The purpose of this study is to develop an organic water-based PCM with high latent heat and melting temperature of −4 °C to −6 °C based on solving the problem of poor stability. Glycine and mannitol aqueous solution were selected as the base PCM, and the static stability was improved effectively with 0.1 wt% potassium sorbate modification. The prepared 6-PCM5 composed of 6 wt% glycine, 1.5 wt% mannitol, and 0.1 wt% potassium sorbate, demonstrated moderate thermal conductivity of 0.6017 W/(m·K) and a suitable melting temperature of −5.78 °C as well as an enthalpy of fusion of 292.64 J/g. After 100 thermal cycles, the melting temperature, enthalpy of fusion, and thermal conductivity were −5.91 °C, 290.66 J/g, and 0.5886 W/(m·K), which decreased only by 2.24%, 0.68%, and 2.18%, respectively. Furthermore, the cold storage performances of 6-PCM5 and ice were compared and evaluated by loading strawberries. Compared with ice storage, the pre-cooling time and average temperature of strawberries in the cold storage box with 6-PCM5 was reduced by 68.4% and 2.55 °C, and the effective cold storage time was lasted for 22.83 h at a temperature range of 0.45 °C to 3 °C, which effectively improved the cold storage quality of strawberries. Overall, the developed 6-PCM5 cold storage material possesses good static and cyclic stability, providing an effective solution for pre-cooling and short-distance cold chain transportation of perishable food.

Massive Fabrication of Flexible, Form-Stable, and Self-Repairing Brine Phase Change Material Gels toward Smart Cold Chain Logistics

Cold chain logistics plays an extremely important role in the storage and transportation of perishable products. Nowadays, phase change materials (PCMs) have been applied in emerging cold chain logistics to overcome the problems of low stability, high energy consumption, and high cost in mechanical refrigeration-based cold chain logistics. Mass production of high-performance phase change cold storage materials toward cold chain logistics is still a major challenge. Herein, self-repairing brine phase change gels (BPCMGs) massively fabricated by ionic cross-linking, covalent cross-linking, and hydrogen bond cross-linking are proposed. Brine containing 23.3% sodium chloride (NaCl) is selected as the phase change component because its phase change temperature is suitable for the cold storage demand of aquatic products. The proposed BPCMGs demonstrate superior thermophysical properties in terms of no phase separation, no supercooling, high form stability, high latent heat, high thermal conductivity, high cyclic stability, and high self-repairing rate. Meanwhile, the BPCMGs present high cost-effectiveness. Given these advantages, BPCMGs are utilized to assemble smart cold storage equipment for the storage and transportation of aquatic products. The cold storage time reaches 36.73 h for aquatic products when the stored cold energy is 364078 J. The location and temperature of the refrigerated products are monitored in real-time. The state-of-the-art BPCMGs provide diversified possibilities for the advanced smart cold chain.

Preparation and heat transfer model of stereotyped phase change materials suitable for cold chain logistics

Phase change cold storage materials have some defects such as easy leakage and poor thermal conductivity in practical application. In the cold chain logistics, the cold storage panels are used as the cold storage devices of the refrigerated trucks, choosing the right way of charging can shorten the charging time of cold storage panel, improve the charging efficiency, save the overall transport time of the cold chain, and improve the transport efficiency. A kind of phase change cold storage material apply to 0–8 °C cold chain logistics was developed by means of step cooling experiment and differential scanning calorimeter, expanded graphite (EG) was added to enhance thermal conductivity and establish porous structure. The heat transfer model of cold storage and charging was established, and the coupling relationship between the charging mode and the charging rate of the cold storage panel was analyzed. The results show that: After adding 8 % expanded graphite (EG), the mass loss rate of Caprylic Acid - Lauryl Alcohol (CA-LA) composite phase change material was 7.73 %, it can effectively prevent leakage of phase change materials. And the phase transition temperature was −0.7 °C, latent heat value was 170.4 J/g, thermal conductivity was 1.411 W/(m·K), and thermal conductivity was increased by 6.17 times. The charging efficiency of the cold storage panel with a built-in charge cold coil was obviously higher than that of the cold storage panel placed in a low temperature environment. The charging time can be shortened by 58.1 % with the same mass of the cold storage material. The research results have certain promoting significance and theoretical support for the adoption of phase change material cold storage technology in cold chain logistics.

Preparation and Thermal Model of Tetradecane/Expanded Graphite and A Spiral Wavy Plate Cold Storage Tank

A cold storage unit can store the cold energy off-peak and release it for building cooling on-peak, which can reduce the electricity load of air conditioning systems. n-tetradecane is a suitable cold storage material for air conditioning, with a phase change temperature of is 4–8 °C and a phase change enthalpy of 200 kJ/kg. However, its low thermal conductivity limits the application of n-tetradecane for high-power cold storage/release. This paper prepares a tetradecane/expanded graphite (EG) composite phase change material (CPCM), whose thermal conductivity can be increased up to 21.0 W/m·K, nearly 100 times over the raw n-tetradecane. A novel model to predict the maximum loading fraction of paraffin in the EG matrix is presented, with an error within 1.7%. We also develop a thermal conductivity model to predict the thermal conductivity of the CPCM precisely, with an error of less than 10%. In addition, an innovative spiral wave plate cold storage tank has been designed for the tetradecane/EG composite. The power and energy density of the cold storage tank are significantly improved compared to that of raw tetradecane. The energy density reaches 40 kWh/m3, which is high among the organic PCM thermal storage tank. This paper shows the significance of thermal conductivity enhancement in designing a cold storage tank.