Thermal Energy Storage Characteristics Research Articles

The Thermal Energy Storage Characteristics of Oleic Acid Modified ZnO‐Decorated Polymer Matrix‐Supported Composite Phase Change Materials: Synthesis and Characterization

AbstractIn this study, modified nano zinc oxide (ZnO)‐reinforced polymer‐supported novel thermally enhanced form‐stable composite phase change materials (PCMs) are presented, which are prepared via water in oil emulsion polymerization and following impregnation process steps. First, ZnO nanoparticles are modified with oleic acid (OA) to obtain lipophilic structures for emulsion stability, which are designed to take a role as a heat transfer activator. To ensure the shape stabilization of n‐hexadecane used as organic PCM, polymeric support materials are synthesized in the presence of modified ZnO nanoparticles (ZnO@OA). The polymeric frameworks exhibit open porous morphology, and the thermal stability of the support matrix improves with the addition of ZnO nanofiller. In the second step, composite PCMs are prepared by incorporation of n‐hexadecane with the solvent‐assisted vacuum impregnation method into polymer composites. The 1.0% ZnO@OA incorporated composite PCM has the highest incorporation ratio and exhibits a thermal storage capability (η) of 100%. According to the T‐history and thermal conductivity tests, it is observed that the heat conduction rate is enhanced with the addition of ZnO@OA nanofiller. The conclusion is that the obtained ZnO@OA integrated composite PCMs have a remarkable potential for latent heat storage applications requiring low temperature in the range of 5–25 °C.

The Thermal Energy Storage Characteristics of Oleic Acid Modified ZnO‐Decorated Polymer Matrix‐Supported Composite Phase Change Materials: Synthesis and Characterization

AbstractIn this study, modified nano zinc oxide (ZnO)‐reinforced polymer‐supported novel thermally enhanced form‐stable composite phase change materials (PCMs) are presented, which are prepared via water in oil emulsion polymerization and following impregnation process steps. First, ZnO nanoparticles are modified with oleic acid (OA) to obtain lipophilic structures for emulsion stability, which are designed to take a role as a heat transfer activator. To ensure the shape stabilization of n‐hexadecane used as organic PCM, polymeric support materials are synthesized in the presence of modified ZnO nanoparticles (ZnO@OA). The polymeric frameworks exhibit open porous morphology, and the thermal stability of the support matrix improves with the addition of ZnO nanofiller. In the second step, composite PCMs are prepared by incorporation of n‐hexadecane with the solvent‐assisted vacuum impregnation method into polymer composites. The 1.0% ZnO@OA incorporated composite PCM has the highest incorporation ratio and exhibits a thermal storage capability (η) of 100%. According to the T‐history and thermal conductivity tests, it is observed that the heat conduction rate is enhanced with the addition of ZnO@OA nanofiller. The conclusion is that the obtained ZnO@OA integrated composite PCMs have a remarkable potential for latent heat storage applications requiring low temperature in the range of 5–25 °C.

Scalable Sol–Gel Permeation Assembly of Phase Change Layered Film Toward Thermal Management and Light‐Thermal Driving Applications

AbstractPhase change materials (PCMs) are pivotal in thermal energy management and conversion applications owing to their exceptional thermal energy storage and release characteristics. However, persistent challenges such as poor thermal conductivity and leakage issues have impeded their widespread adoption. While existing approaches mitigate these challenges by constructing and incorporating 3D thermal conductive networks, they are constrained by discontinuous preparation methods and mold size limitations. Herein, a scalable sol–gel permeation assembly strategy is proposed to prepare phase change layered film by in situ filling polyethylene glycol (PEG) in aramid nanofibers (ANF)/graphene nanoplates (GNP) network. Befitting from the laminated network encapsulation effect of ANF and GNP, the phase change film demonstrates leak‐free and stable phase transition behavior, even after undergoing 500 heating/cooling cycles. Moreover, the resulting PEG/ANF/GNP layered film exhibits an impressive in‐plane thermal conductivity of 23.7 W mK−1 at GNP loading of 28.1 vol.%, rendering it suitable for thermal management applications in electronic devices. The phase change layered film possesses exceptional photo‐thermal conversion properties, maintaining temperatures exceeding 90 °C under a light power density of 200 mW cm−2. Capitalizing on the thermally induced flexibility of the phase transition film and its temperature‐dependent stiffness, its utility extended to developing a light‐thermal driving gripper.

A novel cement mortar comprising natural zeolite/dodecyl alcohol shape stable composite phase change material for energy effective buildings

Investigations into Phase Change Materials (PCMs) for heat storage in facilities have gained significance, contributing to indoor temperature regulation, decreased energy usage, and improved building efficiency, thereby supporting sustainability initiatives. However, the issue of PCM leakage during the heating phase has constrained its thermal energy storage (TES) prospective at large scaled-practices. Addressing this concern, the present study emphases on elimination of the leakage problem of dodecyl alcohol (DA) as a PCM with appropriate melting temperature for building TES request by its impregnating into the natural zeolite (NZ) as a low cost host matrix. In the second stage of the work, using the developed shape stable-NZ/DA (SS-NZ/DA) composite PCM in cement mortar instead of sand, novel cementitious mortars with enhanced thermal properties were created by incorporating different weight percentages (25 %, 50 %, 75 %, and 100 %) compared to the mortar comprising NZ. Experimental works were carried out to analyze the shape-stability, TES features, cycling TES stability and thermal endurance of the SS-NZ/DA composite as well the physical properties, mechanical strength, and solar temperature regulation performance of the SS-NZ/DA included mortars. The SS-NZ/DA demonstrated the melting enthalpy of 107.5 J/g at 19.47 °C and a freezing enthalpy of 106.1 J/g at 19.86 °C. The performance test results obtained under real weather conditions indicated that the integration of SS-NZ/DA into mortar presented maximum drop of 10 % and 9.26 % in peak indoor temperature at the SS-CPCM slab surface and the center of SS-CPCM slab-cabin, respectively, accompanied by an approximate 3-hour time delay. Mortars with SS-NZ/DA composite PCM exhibited a decreased dry unit weight (1189 kg/m3) and thermal conductivity (0.394 W/mK) while experiencing a moderate strength loss (4.5 MPa). These favorable physico-mechanical properties, TES characteristics and thermal management capability make the novel cementitious mortar containing composite PCM as an energy-efficient material for creating thermo-regulative building components. In this study, the natural, economical, and environmentally friendly nature of the NZ material used for PCM impregnation, its ability to contain a high percentage of PCM (up to 45 %) without any leakage issues, is the most fundamental and important characteristic of the composite used. The most unique feature of this composite mortar is the ability to achieve sufficient mechanical and thermal properties in cementitious mortars produced using this composite material without any leakage problems.

Preparation, characterisation and property modification of a calcium chloride hexahydrate phase change material slurry with additives for thermal energy transportation

Efficient thermal energy distribution and rational energy management are effective solutions to address the significant and fast-ascending energy consumption in building heating, ventilation, and air conditioning (HVAC). Phase change material (PCM) slurries with excellent thermal energy transportation and storage characteristics have been recognised as promising secondary refrigerants to simultaneously facilitate efficient heat/cold transport and effective thermal energy storage in air conditioning systems. Among various PCM slurries, salt hydrate PCM slurries have attracted increasing attention in recent years due to their many inherent advantages. This paper presented the preparation, characterisation, and property modification of a CaCl2·6H2O slurry based on a methodology proposed for optimal salt hydrate PCM slurry development. Theoretical modelling was first carried out to assess the availability of salt hydrate PCM slurries based on the phase diagram and solid fraction, followed by a series of property measurements to reveal the mechanisms and address the problems behind the phase transition, crystal particle morphology, stability and rheologic characteristics, using nucleating agents, surfactants and stabilisers. It was found that the salt hydrate PCM slurry developed provides a unit volume enthalpy twice that of water over the phase change temperature range of 5°C, together with acceptable fluidity. The results also showed that the PCM particle size can be well controlled, and the slurry can be stabilised, with the assistance of surfactants and stabilisers. Compared to other types of PCM slurries, the proposed salt hydrate PCM slurry has the advantages of being cost-effectiveness, easy preparation, adjustable phase change temperature, etc., which is promising to facilitate energy saving and rationalisation in building HVAC.

Bio-Based Polymers for Environmentally Friendly Phase Change Materials.

Phase change materials (PCMs) have received increasing attention in recent years as they enable the storage of thermal energy in the form of sensible and latent heat, and they are used in advanced technical solutions for the conservation of sustainable and waste energy. Importantly, most of the currently applied PCMs are produced from non-renewable sources and their carbon footprint is associated with some environmental impact. However, novel PCMs can also be designed and fabricated using green materials without or with a slight impact on the environment. In this work, the current state of knowledge on the bio-based polymers in PCM applications is described. Bio-based polymers can be applied as phase-change materials, as well as for PCMs encapsulation and shape stabilization, such as cellulose and its derivatives, chitosan, lignin, gelatin, and starch. Vast attention has been paid to evaluation of properties of the final PCMs and their application potential in various sectors. Novel strategies for improving their thermal energy storage characteristics, as well as to impart multifunctional features, have been presented. It is also discussed how bio-based polymers can extend in future the potential of new environmentally-safe PCMs in various industrial fields.

Energy storage and hydrophobicity characteristics of cement-based materials containing paraffin-pumice at low air pressure

Pumice is an environmental friendliness and low-cost carrier material for development of paraffin-pumice phase change energy storage composites (PP) at low air pressure in this work. PP was incorporated into cement to obtain CBM-PP. Microstructural, chemical, and thermal characteristics of PP were investigated by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) tests. Moreover, thermal energy storage and hydrophobicity characteristics of CBM-PP were performed by thermal conductivity, drip, and water absorption experiments. Results show that paraffin is effectively impregnated into pumice pores. There exists a physical interaction between paraffin and pumice. And PP possesses excellent compatibility and thermal stability, while its phase change temperatures and thermal energy storage capacities are in the ranges of 51.84–54.69 °C and 77.22–110.60 J/g, respectively. Furthermore, CBM-PP possesses excellent thermal energy storage and hydrophobicity at low air pressure in plateau areas, thus exhibiting a good application prospect in building thermal management and impermeability. Moreover, the thermal conductivity variation of CBM-PP is studied by the thermal conductivity model, which can predict the thermal conductivity with an error of no >9 %.

Experimental investigation of diesel engine driven micro-cogeneration system integrated with thermal energy storage for power and space cooling

In this paper the performance and emission characteristics of thermal energy storage integrated micro-cogeneration system was investigated. This system was developed by connecting the vapor absorption refrigeration (VAR) system and thermal energy storage (TES) system with the exhaust gas pipe of a single-cylinder diesel engine. The vapor absorption refrigeration system has the cooling capacity of 500 W. A cabin of 1500 mm length, 1200 mm width and 1500 mm height was fabricated with proper insulation as space for cooling. The cabin temperature drop of 8.6 ℃ was achieved in 45 min. The cooling capacity of the VAR system was 302 W, and the COP of the VAR system was 0.398. The cabin temperature drop decrease with decrease in engine RPM but it was maintain stable (8.6℃) for 25 min by using TES. The overall efficiency of the cogeneration system was 1.79 % higher than the single generation. Hence, the result showed that the small capacity (5 kW) stationary diesel can be successfully converted into a cogeneration system to produce power and space cooling simultaneously.

Thermal energy storage characteristics of carbon-based phase change composites for photo-thermal conversion

Capture and utilization of solar energy using phase change materials (PCMs) can effectively answer the challenge of solar intermittency. However, the flaws of low thermal conductivity and poor thermal stability of PCMs limit their practical applications, and the selective absorption of solar energy also hinders it to achieve high photo-thermal conversion. In this work, a novel PCM was synthesized by adding expanded graphite and olefin block copolymers blended within paraffin wax. Enhanced thermal conductivities were realized that a 17.12 W/(m·K) in the vertical compression direction and 4.71 W/(m·K) in the parallel compression direction, which were 68.48 and 18.84 times in contrast to that of raw paraffin wax. A maximum solar absorptance of 97.47 % was achieved, and the photo-thermal conversion and energy storage capacity in the vertical compression direction were superior using the novel PCM. With the increase in light intensity, this PCM completed phase transition faster, reached a higher equilibrium temperature, and exhibited an outstanding thermal stability and cyclic stability within the assisted electron conductivity. Additionally, commercial software was also used to simulate thermoelectric applications of the PCM in real-world settings. This study provides new ideas for preparation and solar-thermal applications of anisotropic carbon-based PCMs.

Experimental and numerical investigations on operation characteristics of seasonal borehole underground thermal energy storage

To investigate operation characteristics of seasonal borehole underground thermal energy storage (SBUTES) with different operational strategies, a model test platform with reduced size was established based on similarity principle. The test results show that the larger the start-stop time ratio, the smaller the average heat exchange rate per unit depth (HERPUD) of borehole, and the lower the energy storage efficiency, but the thermal energy storage and extraction capacity increase. For the time ratio of thermal energy storage to extraction (TROSE), the larger the TROSE, the larger the thermal imbalance rate of energy storage body, which will lead to the gradual increase or decrease of temperature of energy storage body and is not conducive to the operation of energy storage. Compared with the asynchronous mode of storage and extraction, the synchronous mode of storage and extraction can effectively reduce the average temperature of energy storage body and increase the heat exchange efficiency of boreholes during the thermal energy storage. The focused energy storage mode can improve the energy storage efficiency and soil temperature recovery rate, balance the thermal energy storage and extraction capacity, and thus the performance of SBUTES can be optimized. A 3-D CFD model of borehole energy storage was established to further find the influences of borehole layout forms, layout spacing and depths on characteristics of the SBUTES. It can be found that for the energy storage efficiency, the hexagonal layout is the highest, the rectangular layout is the lowest, and the circular layout is slightly higher than the square one. Under the same volume of boreholes group, increasing the spacing of inner boreholes can effectively alleviate thermal interference of inner boreholes during the thermal energy storage, and the heat exchange capacity undertaken by inner boreholes can be improved. But it is not conducive to thermal energy extraction. Although increasing borehole depth can increase thermal energy storage and extraction capacity and system operation efficiency, the increase degree is decreasing with the increase of borehole depth, and the greater the borehole depth, the smaller the influence of borehole depth on characteristics of SBUTES.

Numerical modeling and parametric study of the heat storage process of the 1.05 MW molten salt furnace

The implementation of thermal storage technology in the steel industry has the potential to reduce carbon emissions and contribute to a more sustainable future for the planet. Utilizing molten salt furnaces to convert waste heat from blast furnace gas into thermal energy from molten salt is an innovative approach. In this study, the heat flux density data calculated using ANSYS FLUENT were imported into a MATLAB calculation program developed based on the multi-section lumped parameter method to model the three-dimensional transient thermal performance calculations of the molten salt furnace. A benchmark energy storage experiment on a 1.05 MW furnace validated simulation results. The experimental molten salt outlet temperature is 566.5 °C, 13.92 °C higher than the simulation data with 2.46% deviation. The study investigates the dynamic characteristics of thermal energy storage in molten salt furnaces by disturbing external parameters. Results show that molten salt temperature rise is linearly related to heat flux density, molten salt inlet temperature, and mass flow rate. Notably, every 0.8 kg/s increase in molten salt mass flow rate reduces the outer coil temperature by 6.59%. The highly accurate model provides a reference for the design, control and commissioning of molten salt heating and thermal storage systems.

An analytical model for the energy storage potential of phase change materials supported by polymeric colloidal aerogels

Effective thermal energy storage has become one of the well-recognized aspects of modern energy management. Phase change materials (PCMs) shape-stabilized in the porous structure of porous support materials are one of the candidates to reach stable and effective thermal energy storage. This study presents an analytical model for the prediction of thermal energy storage density and thermal conductivity of colloidal aerogels impregnated by a PCM (TCAP model). The TCAP model is a series-parallel model that combines the thermal conductivity of the structure of the supporting aerogel and the thermal characteristics of the impregnated PCM. To validate the model, a mesoporous resorcinol-formaldehyde aerogel with an average pore diameter of 5.2 nm is synthesized, and two types of polyethylene glycol PCMs (PEG600 and PEG2000) are impregnated into the porous structure of the supporting material. The results confirm that the TCAP model can accurately predict the thermal energy storage characteristics of the system in terms of energy storage rate and density. Based on parametric studies, the highest heat capacity that can be achieved in a resorcinol-formaldehyde aerogel/polyethylene glycol is 35 kJ/kg.k with a ΔT of 40 K. On the other hand, it can be predicted that when ΔT increases from 10 K to 20 K, the energy storage of the system will change in the range of 52 % to 74 %. Moreover, The TCAP model developed in this study can be used to design/optimize energy storage materials for various applications such as smart buildings, solar energy storage devices, environmental thermal management systems, wearable thermal management devices, and temperature control in electronics.

Thermal energy storage characteristics of finned tubes with different gradients of fin heights

Adding fins is considered to be a promising method to enhance heat transfer. As for the vertical latent thermal storage tube, it can be observed that the phase change materials in the upper part have much shorter charging time than in the lower part. To further enhance the heat transfer to boost the overall energy storage efficiency and reduce the apparent inhomogeneity of melting characteristics, fins with gradient height are packed. In this study, vertical shell-and-tube thermal energy storage tubes with fins of positive and negative gradient height are analyzed. After using experiments to verify the established numerical model, the phenomenological thermal characteristics are revealed and then additional analysis is used to investigate the thermal characteristics of the charging process, including melting, temperature distributions, and flow features. Results show that the negative gradient fins perform better than the positive gradient fins compared to the uniform ones. Furthermore, the complete melting time is reduced by 32.47% with a measured gradient of −0.8. A 42.11% enhancement in the time-integral average proportion of phase change materials (PCMs) in medium-temperature and a 78.74% suppression in the ratio of overheated PCMs at the final moment are achieved by the negative finned tube of −0.8 compared to a case with uniform fins. A tube with a higher bottom fin has a higher transient maximum velocity of the liquid phase transition material during melting, which also has a time-integral Grashof number (Gr) improvement of 31.46% compared to a uniform fin. The average energy storage is improved by using the negative gradient height fins of −0.8, as much as 1.34 times that of uniform height fins.

Evaluating the effect of magnesium oxide nanoparticles on the thermal energy storage characteristics of the inorganic PCM

Thermal storage with phase changing materials (PCM) has got the attention of the researchers in recent days. Among the PCMs, inorganic salt hydrates are having high potential to act as thermal storing medium due to their large latent content. However, they lack large-degree supercooling and have issues with phase segregation. In the present study, the thermal characteristics of sodium acetate trihydrate (SAT) have been studied under the influence of different weight fractions (0.0%, 0.25%, 0.5%, 0.75%, and 1.0%) of MgO nanoparticles (nano-MgO). Carboxymethyl cellulose (CMC) has been used as the thickener, and nano-MgO has been tested as the nucleating medium. The results demonstrated that the use of 0.75% nano-MgO with SAT is suggested as the best composition to augment the thermal characteristics of SAT PCM. With 0.75% nano-MgO, the supercooling of the SAT was reduced to 0.32 °C, and the thermal conductivity of the SAT was enhanced by 40.94%. Nonetheless, the latent heat of the SAT PCM had not been significantly affected by the addition of nano-MgO until its fraction of 0.75%.

Development of rigid polyurethane foam incorporating phase change material for a low‐temperature thermal energy storage application

AbstractPolyurethane (PU) foam is most commonly used in thermal insulation in cold storage applications but it lacks thermal energy storage characteristics. In the present work, a phase change material (PCM) n‐tetradecane is microencapsulated with poly(methyl methacrylate‐co‐methacrylic acid) using oil‐in‐water emulsion polymerization followed by incorporation into the PU foam formulation to fabricate composite foam. The purpose of the study was to combine thermal insulation along with thermal energy storage characteristics into PU foam. The phase change enthalpy of PU foam was improved from 22.43 to 55.46 J g−1 by changing the microcapsule loading fraction from 10% to 30%. The composite PU foam exhibits good thermal reliability even after 100 thermal cycling tests. The morphological observation confirms a decrease in cell size while increasing the microcapsule content. It is found that microcapsule addition has no effect on the thermal stability of PU foam. A prototype has been fabricated and tested, showing an enhancement in the thermal energy storage capacity of PU composite foam. This performance makes this PU‐PCM system feasible for cold energy storage applications. © 2022 Society of Industrial Chemistry.

Microencapsulation of n-tetradecane with poly (methyl methacrylate-co-methacrylic acid) shell by seeded emulsion polymerisation and its thermal energy storage characteristics

This study aims to enhance the latent heat storage properties of the microcapsules by altering the amount of crosslinking agent from 3 to 20%w/w, the core-to-shell ratio from 1:1 to 2:1, and the amount of initiator from 1 to 3%. The phase change material n-tetradecane (C-14) was microencapsulated by using poly (methyl methacrylate -co- methacrylic acid) as a shell material through an oil by water-seeded emulsion polymerisation technique. The structural, morphological, and thermal properties of microcapsules were evaluated by using Fourier transform infrared spectroscopy, optical microscopy, scanning electron microscopy, differential scanning calorimetry analysis, and thermogravimetric analysis. The average particle size of the microcapsules ranges from 01 to 15 µm. The results showed that the microcapsules have a higher melting enthalpy value of 127.3 ± 0.06 J/g with a microencapsulation efficiency of 66.72% when a 20% w/w crosslinker was used. The thermal stability of the phase change material (PCM) was increased by ∼30 ± 2 °C by encapsulation.

Influence of SiC on the thermal energy transfer and storage characteristics of microwave-absorbing concrete containing magnetite and/or carbonyl iron powder

A microwave-absorbing concrete with favorable heat transfer and storage was investigated to improve the efficiency of deicing concrete pavement during microwave heating and off in cold winter. The concrete was prepared using magnetite and/or carbonyl iron powder (CIP) as the absorbing material. The effect of SiC as the heat transfer and storage material on microwave absorption efficiency, thermal conductivity and thermal diffusivity of concrete were studied. In addition, the pore structures of concrete were investigated to analyze its influence on the thermal properties of concrete.The results showed that the SiC slightly affected the microwave absorption capacity of magnetite concrete (MC) and magnetite-CIP concrete (MCC). The SiC could effectively improve heat transfer and storage ability of concrete. When the content of SiC was 7%, SiC improved the thermal conductivity and effusivity of MC and MCC were improved by 86.4% and 110%, and 84% and 97.3%, respectively. Meanwhile, adding CIP and SiC could improve the porosity and pore diameter of concrete to make it dense, which might be an influence factor to improve the thermal properties of concrete. Under the same conditions, the thermal conductivity and storage capacity of concrete showed the same change trend. In addition, the coefficient of temperature nonuniformity (CTN) and coefficient of max temperature gradient (CMTG) as new indexes was used to evaluate the influence of SiC on the thermal properties of concrete. Therefore, to improve concrete absorption of more heat during microwave heating, and transfer and store heat quickly for road deicing, the magnetite-CIP-SiC concrete (MCSC) might be the most suitable.

N-Heptadecane-Impregnated Wood as a Potential Material for Energy-Saving Buildings

Phase change materials (PCMs) are ideal for thermal management solutions in buildings. This is because they store and release thermal energy during melting and freezing. Spruce (Picea orientalis (L.) Peterm.) sapwood was impregnated with n-heptadecane (100%) as a PCM. The decay-resistance properties and thermal energy storage (TES) characteristics of the n-heptadecane-impregnated wood were studied. The phase change properties of n-heptadecane (nHD)-impregnated wood were characterized by Fourier-transform infrared (FTIR), thermogravimetry (TGA), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses. As confirmed by DSC analysis, nHD-impregnated wood demonstrated moderate performance in storing and releasing heat during the phase change process. Significant increases were observed in the 2800–3000 cm−1 and 1471 cm−1 peaks in FTIR spectra of wood samples impregnated with nHD, which showed C–H stretching in methyl and methylene groups and asymmetric deformation vibration of the paraffin methyl group (CH3–) and C–O stretch in lignin, respectively. It was observed that there was a change in the crystal structure of spruce wood samples after nHD impregnation. This study revealed that PCMs are resistant to wood-destroying fungi. The performance of nHD-impregnated spruce wood proves that it can be used as a thermal regulating building material to reduce energy consumption. In addition, it has been proven on a laboratory scale that the PCM used is highly resistant to biological attacks. However, large-scale pilot studies are still needed.

Evaporative cooling performance characteristics in ice thermal energy storage with direct contact discharging for food cold storage

In a vapor-compression refrigeration system for the cold storage of food, latent heat transfer not only adversely affects the freshness of food but also reduces energy efficiency. This study aims to investigate the evaporative cooling performance characteristics of ice thermal energy storage (ITES) with direct contact discharging for food cold storage to minimize latent heat transfer. Laboratory-scale test facilities were constructed for the ITES with direct contact discharge for evaporative cooling. The performance characteristics of the ITES with direct contact were measured and analyzed according to the conditions of the inlet air (temperature and humidity) and control parameters (face air velocity and ice amount). It is necessary to select an appropriate amount of ice at the maximum face air velocity for food cold storage. Therefore, for fresh foods with a low weight loss rate, such as potatoes, the amount of ice with the maximum COP should be set, whereas for fresh foods with a large weight loss rate, such as mushrooms, it is appropriate to select the minimum amount of ice to maintain a low weight loss rate.

Numerical investigation on melting and thermal performances of a phase change material in partitioned cavities with fins for thermal energy storage

The practical application of solid-liquid phase transition latent thermal energy storage devices is restricted by the low value of thermal conductivity in phase change materials (PCMs). To alleviate this problem, a proposal for a newly developed thermal energy storage unit with metal multiple partitions and flat fins coupled is presented in this paper. The design was constructed by dividing the typical vertical rectangular thermal energy storage unit into several partitions (1, 2, 4, and 8), including 4-fins and 8-fins in different partitions. A 2D transient solid-liquid phase change numerical model was firstly validated and then the effect of different configurations was numerically determined to obtain the thermal energy storage characteristics, velocity field, solid-liquid interface, temperature distributions, and thermal transfer performances. The results show that the optimized metal partitioned cavities lower the PCM's melting time with the maximum melting time reduction occurring at a value of 76.8 % compared to the common wooden partition. Because of increased thermal networks or enhanced local natural convection, increasing the cavity partitioning and fins shortens the melting time of the PCM. The 8-partitions cavity coupled with 8-fins generates the shortest melting time. Increasing the quantity of cavity partitioning and fins also leads to a reduction in the time needed to attain the largest amount of stored energy and an increase in the Nusselt number and power.