Thermal Energy Storage Device Research Articles

Thermal Characterization of [C2Im][NO3] and Multivalent Nitrate Salts Mixtures

Due to their intrinsic properties, the current applicability of ionic liquids is enormous. In particular, their use in electrochemistry is beyond question. Numerous studies on these compounds and their mixtures, especially with lithium salts, focus on their use as electrolytes for batteries and other energy storage devices. This includes thermal energy storage devices, where 4th generation ionic liquids and their derivatives show a huge potential. Nevertheless, considering the uneven availability of the raw materials, such as lithium, research has extended to mixtures of these compounds with other salts of different metals that are more abundant and widely distributed, such as magnesium or aluminum. This work presents a comprehensive thermal characterization, using differential scanning calorimetry and thermogravimetry, of the protic ionic liquid ethylimidazolium nitrate and its mixture with magnesium and aluminum nitrate salts at different concentrations. Additionally, a comparison between these results and previous studies of mixtures of this ionic liquid with lithium nitrate, as well as mixtures of the protic ionic liquid EAN with the same metal salts, was also performed. The results indicated that the salt addition tends to broaden and reduce crystallization and melting peaks, while the glass transition becomes more visible and shifts to higher temperatures with increasing salt concentration. This is due to the disorder generated by the rearrangement of ions in the polar domains, which erodes the hydrogen bond network of the protic ionic liquid. Nevertheless, the thermal stability of the blended samples does not change significantly compared to the bulk ionic liquid.

Heat transfer investigation of nano – Encapsulated phase change materials (NEPCMs) in a thermal energy storage device

Phase change natural convection heat transport and flow features of a variety and new types of hybrid nanoliquids, suspension of Nano – encapsulated phase change materials (NEPCMs), within a square cavity is inspected theoretically in this analysis. The capsules are arranged with a shell and a PCM as a core. The shell of this NEPCM prevents the phase change material from the direct interaction of hot fluid and from the leakage. The heat capacity of the suspension contains latent heat generated at the time of phase change. The modeled equations are numerically scrutinized with Finite element method. Variable thermal conductivity parameter 1≤Nc≤5, variable viscosity parameter 1≤Nv≤5, radiation number 0.5≥R≥0.1, Rayleigh parameter 102≤Ra≤103, volume fraction of NEPCMs1%≤ϕ≤5% and fusion temperature (0.2≤θf≤1.0) impact on the patterns of heat capacity ratio, isotherms and velocity lines are examined in detail. The results indicates that, as the volume fraction values of NEPCMs amplifies from 1% to 5% the rates of heat transfer of the nanoliquid magnifies 42% compared to the host fluid. Non – dimensional rates of heat transport magnifies with growing (Ste) values.

Engineering lightweight Poly(lactic acid) graphene nanoribbon nanocomposites for sustainable and stretchable electronics: Achieving exceptional electrical conductivity and electromagnetic interference shielding with enhanced thermal conductivity

The challenge of creating flexible and sustainable electronics with properties such as lightweight, electrical and thermal conductivity, and electromagnetic interference (EMI) shielding is addressed in this study. Carbon nanotubes and graphene are commonly used in flexible electronic devices, but gaps exist in their conductivity and flexibility. A novel and scalable fabrication method is introduced, involving the creation of bio-based nanocomposites by integrating flexible and high aspect-ratio graphene nanoribbons (GNRs) into a poly (lactic acid) (PLA) matrix. The nanocomposites were drawn above the glass transition temperature (Tg) of PLA, resulting in the formation of extended shish structures, as observed in scanning electron microscope (SEM) images. These structures significantly enhanced thermal and electrical conductivities, as well as EMI shielding features. The combination of flexible GNR nanofillers with uniaxial stretching led to a substantial increase in Young's modulus, tensile strength, and toughness by approximately 550 %, 440 %, and 600 %, respectively, most likely due to the increased network connection despite the higher flexibility of GNRs. Moreover, in-plane thermal conductivity registered a notable enhancement of approximately 110 %. The EMI shielding reached 26 dB, with an absorption contribution to EMI shielding of around 45 %. Additional improvement was achieved through foaming of the stretched samples, resulting in multilayer structures with alternative extended shish and foam structures. Furthermore, a significant augmentation of approximately 33 dB in total EMI shielding of the foamed samples, accompanied by an 85 % increase in SEA was documented. These promising findings underscore potential applications across diverse domains, including thermal interface materials, electronic packaging, capacitors, and energy storage devices, with a specific emphasis on the realm of sustainable and stretchable electronics.

Thermal analysis of a viscoelastic Maxwell hybrid nanofluid with graphene and polythiophene nanoparticles: Insights from an artificial neural network model

The utilization of solar radiation by converting them into thermal energy is discussed in this paper. Nanoparticles improve the ability of heat transfer therefore, it is beneficial in the use of solar thermal systems and energy storage devices. The novel mixture of nanoparticles Graphene and Polythiophene in base fluid, which has high thermodynamic properties for the improvement of thermal effect with electromagnetic effect by using Maxwell fluid model is discussed. Polyvinyl alcohol water is taken as base fluid flowing through a moveable flat plat. The governing partial differential equations are transformed into ordinary differential equations. The semi-analytical technique, homotopy analysis method is used to obtain the solution of the ordinary differential equations. The velocity is enhanced with magnetic and electric field strength. The increase of the Prandtl number, Eckert number and chemical reaction parameter, exceeds the thermal effect which produces more entropy generation and heat enhancement. The results show that the hybrid nanofluid with this Novel mixture is highly thermodynamic with higher entropy and rapid thermal augmentation which can be used in energy production and energy storage devices. A novel intelligent numerical computing technique multi-layer perceptron with feed-forward back-propagation, an artificial neural networking method with the Levenberg-Marquard algorithm is used in this model. The data is gathered for the neural networking method training, validation, and testing. The efficiency of the model is obtained and mean square error is obtained by artificial neural networking.

Temperature and salt concentration behavior of a compact rectangular salinity gradient solar pond

Design of economical and effective solar ponds which are useful thermal energy storage devices, remains a huge challenge. The present work aims at investigating the thermal performance of low cost mini salt gradient solar pond. The portable pond was fabricated as a rectangular configuration having a volume of 0.5m3. Polystyrene and high density polyethylene sheets were employed for insulating the walls. The top of the pond was covered with a slender glass so that the dust accumulation could be prevented without affecting the absorption of solar radiation. Sodium chloride salt was used as the medium and the three salt gradient regions namely lower convective, non-convective, and upper convective regions were established through injection filling technique. The temperature and salt gradient data were observed experimentally for a period of 20 days at Coimbatore, India. The pond could absorb significant amount of available radiation (around 65%) and the maximum temperature of the pond was observed to be 49oC. Frequent washing of the water surface is necessary to maintain stable salt gradient. Nevertheless, portable pond fabricated with low cost materials exhibited good potential of storing solar energy for solar thermal applications.

A Eulerian Numerical Model to Predict the Enhancement Effect of the Gravity-Driven Motion Melting Process for Latent Thermal Energy Storage.

Latent thermal energy storage (LTES) devices can efficiently store renewable energy in thermal form and guarantee a stable-temperature thermal energy supply. The gravity-driven motion melting (GDMM) process improves the overall melting rate for packaged phase-change material (PCM) by constructing an enhanced flow field in the liquid phase. However, due to the complex mechanisms involved in fluid-solid coupling and liquid-solid phase transition, numerical simulation studies that demonstrate physical details are necessary. In this study, a simplified numerical model based on the Eulerian method is proposed. We aimed to introduce a fluid deformation yield stress equation to the "solid phase" based on the Bingham fluid assumption. As a result, fluid-solid coupling and liquid-solid phase transition processes become continuously solvable. The proposed model is validated by the referenced experimental measurements. The enhanced performance of liquid-phase convection and the macroscopic settling of the "solid phase" are numerically analyzed. The results indicate that the enhanced liquid-phase fluidity allows for a stronger heat transfer process than natural convection for the pure liquid phase. The gravity-driven pressure difference is directly proportional to the vertical melting rate, which indicates the feasibility of controlling the pressure difference to improve the melting rate.

Experimental and analytical study on continuous frozen/melting processes of latent thermal energy storage driven by bubble flow

It is emphasized direct contact method that introduced to the frozen/melting processes has a high value of development due to the role for mitigating thermal stratification, reducing phase separation and enhancing heat transfer efficiency. However, the absence of fixed solid heat transfer walls can lead to discontinuous switch and difficult-to-control problem during frozen/melting processes. In this paper, the latent thermal energy storage device driven by bubble flow is experimentally investigated. With the usage of low melting point paraffin and the pattern of free expansion in a cabinet, continuous switch between the frozen and the melting process can be realized. Phase change processes, temperatures, heat transfer efficiency, volume change and pressure drops are measured and analyzed. A dynamic analytical model to describe the processes is also developed based on the ε - NTU method. The results show that the heat transfer efficiency can reach to 0.8 at least in all the experimental cases. Moreover, this study records the pressure difference of the gas flow, predicts the required input mechanical work and analyses the volumetric heat transfer coefficient, which help to reveal feasibility of the device.

State-of-the-art and challenges towards a MOlecular Solar Thermal (MOST) energy storage device

The current global energy scenario calls for the urgent replacement of fossil fuels for alternative, environmentally affordable, abundant and cheap energy sources. Among the different options available, MOlecular Solar Thermal...

PERFORMANCE OF HEAT PUMP BASED ON COMPOSITE ADSORBENT ‘SILICA GEL – CRYSTALLINE HYDRATE’

Performance of an adsorptive heat pump has been studied. The factors affecting the efficiency of its work have been analyzed. Operating parameters and efficiency of adsorptive heat pumps and adsorptive heat storage devices have been compared. An algorithm of calculating the basic operating characteristics of an adsorption heat pump in heat supply systems has been proposed. It involves calculating the mass transfer coefficient, final absolute humidity of the air flow passed though adsorbent layer, the water uptake or adsorption and the useful heat of adsorption and heat of condensation, determination of heat inputs for the operation of the device such as heating the adsorbent, case of the device, hydraulic circuit, the water in the tank and adsorbed water, heat of desorption and heat of evaporation, estimation the coefficient of energy performance. The evaluation criteria of the efficiency of adsorptive heat pumps and heat storage devices have been compared. It is shown that the operating parameters of the adsorptive heat pump and the adsorptive thermal energy storage device based on composite adsorbents ‘silica gel – sodium sulfate’ and ‘silica gel – sodium acetate’ are the same, i.e. airflow rate 0.08 - 0.1 m3/s and initial absolute humidity of airflow 0.03 – 0.04 kg/m3, which are corresponded with maximal efficiency of the device. The temperature of the humid air flow directed to the adsorbent layer is suggested to be set at 20 – 40 °C. The measures to increase the efficiency of the adsorptive heat pump are proposed. It is shown that ultrasonic air humidification allows to increase the coefficient of energy performance by almost 2 times compared to steam humidification. The obtained results can be used for developing energy-efficient heating systems of residential premises.

Charging/discharging performance and corrosion behavior of a novel latent heat thermal energy storage device with different fin plate materials

The use of low-grade industrial waste heat for building heating could facilitate the decarbonization of heat sector, which accounts for a large share of energy consumption worldwide. However, the uncontrollable fluctuation characteristics of heat source and mismatch between energy supply and demand greatly limit its large-scale application. Notably, latent heat thermal energy storage (LHTES) technology, showing remarkable advantages in terms of energy storage density, heat storage temperature (nearly constant), technology maturity and cost, could effectively solve the above problem. Hence, this work specially focused on LHTES device that utilized fin plate for improving performance of heat harvesting and reuse. Furthermore, charging/discharging performance and corrosion behavior of a novel device with different fin plate materials (brass, aluminum and stainless steel) were investigated. Results showed that temperature difference between plate surface and melting point above 10 °C effectively shortened charging time more than 45.7 %. A higher thermal conductivity of fin material contributed to a better thermal performance. Aluminum and stainless steel preferred to be used as fin plate materials of targeted hydrated salt owing to their low corrosion rate of 0.016 and 0.002 mg/(cm2·yr), respectively. This work was expected to provide a guidance on designing a LHTES device applied in building heating.

Experimental analyses of solidification phenomena in an ice-based thermal energy storage system

Latent thermal energy storage devices can efficiently store surplus thermal energy during off-peak hours. The system's phase change material (PCM) improves energy storage capacity and isothermal properties. Most PCMs have weak thermal conductivity, which hampers heat transfer. Thus, the present analysis involves an insight into the heat transfer characteristics and thermal performance of a vertical tube-in-tank cold storage system. The objective of this investigation is to gain a better understanding of the significance of buoyancy-driven convection within the side bulk region during the discharging of water as PCM in the heat exchanger. A series of experiments are conducted to investigate the effect of varying the initial bulk temperature on the rate of PCM solidification. The effects of three distinct initial bulk temperatures which are 20 °C, 15 °C, and 5 °C on the solidified mass fraction, thermal performance, and heat transfer rate at various radial and axial locations in PCM are examined. It is seen that PCM experienced a varying cooling rate with varying axial height and is found to be the highest in the bottom region. PCM temperature decreases from top to bottom under the cases of 20 °C and 15 °C, respectively. In contrast, a narrow-ranged thermocline layer is observed under 5 °C bulk temperature, making uniform temperature distribution within the bulk. The influence of bulk natural convection prevails in the later stages of the discharging process under 5 °C bulk, whereas it predominantly exists during the initial stages of solidification under bulk temperatures of 20 °C and 15 °C.

Heat transfer enhancement and applications of thermal energy storage techniques on solar air collectors: A review

Solar air collectors have been used in a variety of industrial applications, prompting a study and summary of various studies on the topic. Solar collectors’ exceptional energy conversion and storage outputs have piqued curiosity in the field of energy research. The current review study focuses on solar thermal application advancements and provides an overview of thermal energy storage devices and solar collectors. This paper presents and discusses a variety of solar collectors, both concentrating and non-concentrating. The energy storage media utilized in these plants, phase change material with melting temperatures exceeding 300°C, was exam-ined. The goal of this study is to provide the necessary information for advanced investiga-tions in the development of cost-effective high-temperature thermal storage systems. Finally, a summary of the presentation, as well as potential solar power plants are reviewed.

Enhancing the performance of composite phase change materials using novel triply periodic minimal surface structures

Organic phase change materials (PCMs) are widely used in thermal management applications owing to their high latent heats of fusion and low cost. Unfortunately, their poor thermal conductivities severely hamper the thermal transport process. Hence, PCMs are often hybridized with high thermal conductivity materials that promote phase change for time-sensitive applications and potentially increase the power density of thermal energy storage (TES) devices. Optimized thermally conductive networks with high-latent-heat PCM matrices are critical in the thermal management of high heat flux applications. With advancements in additive manufacturing, it has become easier to create complex topologies, such as triply periodic minimal surfaces (TPMS), that can further augment the performance of composite PCMs. TPMS surfaces have shown great promise in improving thermal transport performance but investigations into their thermal properties remain limited. In this study, the thermal performances of PCM infused TPMS structures of wall thicknesses varying from 0.4 mm to 0.8 mm were systematically investigated. The TPMS structures were designed using level-set equations, and each system of structures was fabricated by selective laser melting, a metal additive manufacturing technique. Numerical investigations were performed to understand the phase change dynamics of PCM in TPMS cells and experiments were performed to determine their thermal properties and phase change performance for thermal energy storage applications. Our simulations revealed that for structures with uniform wall thickness of 0.4 mm, the novel Neovius structure resulted in the highest effective thermal conductivity enhancement. For a given thickness, it is thus hypothesized that more complex TPMS topologies have higher surface areas and volumes which enhance their thermal conductivities. However, the complex shape of the Neovius structure could not be further uniformly thickened without self-intersecting geometries. Ultimately, a balance of both the surface area and thickness of the TPMS cell determines the thermal conductivity enhancement. Overall, the 0.6 mm thick IWP cells had the highest thermal conductivity of 13.84 W/m K, which was consistently verified in experiments. This is likely due to the fact that it has a larger surface area than the P structure but is also thicker than the 0.4 mm Neovius structure. To further demonstrate the potential application of our PCM-based TPMS design, low temperature thermal cycling tests were performed. Our results showed the IWP cell structure promoted a more uniform temperature distribution as compared to the P cell. Phase change in the 0.6 mm thick IWP cell structure was completed 1.4 times faster than the 0.8 mm thick P cell and 1.8 times faster than the 0.6 mm thick P cell. The purpose of this study is to provide useful guidelines for the selection of TPMS structures for various applications such as battery packs and spacecraft and to open doors for the co-optimization of materials and device geometry for enhanced energy and power density.

Thermal storage performance of latent heat thermal energy storage device with helical fin under realistic working conditions

Latent heat thermal energy storage has garnered increasing interest and development as a significant technique for recovering waste heat. In this research, the latent heat thermal energy storage device with helical fin is proposed and its thermal storage performance is also investigated by numerical simulation. First, assorted helix pitches (400 mm, 200 mm, 100 mm and 50 mm) and fin numbers are taken into account to investigate the thermal storage performance with various fin parameters. Then, four types of nanoparticles (SiC, TiO2, CuO and Al2O3) are dispersed into the phase change material to address the inherent defect of poor thermal conductivity of phase change material. Afterwards, several realistic working circumstances, including four inclination angles (θ = 0°, 30°, 60° and 90°) and eight oscillating inlet temperatures among which the frequencies are 1 Hz, 2.5 Hz, 5 Hz and 10 Hz, and amplitudes are 0.25, 0.5, 1 and 2, are selected to explore the impact on melting process. The results indicate that shortening helix pitch and increasing fin number can accelerate the melting rate, while the selection of these two parameters needs to consider the thermal storage performance and the processing difficulty as a whole. Furthermore, the selection of nano phase change materials needs to balance the relationship between thermal storage rate and capacity. Compared to the complete melting time when the device is placed vertically, the complete melting time is reduced by 14.3% when the device is placed horizontally. Utilizing the oscillating inlet temperature reduces the complete melting time by at least 21.2% compared to using the steady inlet temperature. When the frequency value is increased from 1 to 10, the complete melting time is only reduced by 3.4%. Complete melting time of the amplitude of 2 is 12.9% shorter than that of the amplitude of 0.25.

Thermally Conductive Molten Salt for Thermal Energy Storage: Synergistic Effect of a Hybrid Graphite-Graphene Nanoplatelet Filler.

Renewable energy technologies depend, to a large extent, on the efficiency of thermal energy storage (TES) devices. In such storage applications, molten salts constitute an attractive platform due to their thermal and environmentally friendly properties. However, the low thermal conductivity (TC) of these salts (<1W m-1 K-1) downgrades the storage kinetics. A commonly used method to enhance TC is the addition of highly conductive carbon-based fillers that form a composite material with molten salt. However, even that enhancement is rather limited (<9W m-1 K-1). In this study, the partial exfoliation of graphite to graphene nanoplatelets (GnP) in a molten salt matrix is explored as a means to address this problem. A novel approach of hybrid filler formation directly in the molten salt is used to produce graphite-GnP-salt hybrid composite material. The good dispersion quality of the fillers in the salt matrix facilitates bridging between large graphite particles by the smaller GnP particles, resulting in the formation of a thermally conductive network. The thermal conductivity of the hybrid composite (up to 44W m-1 K-1) is thus enhanced by two orders of magnitude versus that of the pristine salt (0.64W m-1 K-1).

Numerical investigation of the impact of toothed fins on the heat transfer performance of a shell-and-tube exchanger during phase change material melting process

The poor thermal conductivity of phase transition materials hampers the development of latent heat energy storage devices. There is much scholarly interest in enhancing heat transmission in these materials. Using a finned shell-and-tube exchanger is a traditional strategy for improving the effectiveness of latent thermal energy storage devices. However, the storage systems' actual working volume decreases when many fins are added. Numerous studies have shown that toothed fins are more efficient in transferring heat than regular fins. As a result, it is anticipated that toothed fin latent heat energy storage systems will produce better thermal effects. Unfortunately, the impact of toothed fins on the melting of phase transition materials has only been briefly discussed in published literature. To close this important knowledge gap, this paper thoroughly studies two regularly used fins, namely the annular fin and longitudinal fin with toothed apertures. The impact of different toothed-opening volumes and tooth spacing on the melting process of phase transition materials are examined using numerical simulations. The results show that toothed fins have a 20% lower fin volume than traditional circular and longitudinal fins, which has a marginally less positive impact on phase change material melting times of 1.09% and 0.98%, respectively. The recommended toothed-opening volume and tooth count for the annular fin are 10%–20% and 16 teeth, respectively, whereas the recommended toothed-opening volume and tooth spacing for the longitudinal fin are 10%–20% and 1 mm, respectively. Additionally, the tooth spacing affects heat transfer, in one investigation, decreasing the tooth spacing by 2.5 and 2 times led to reductions in the melting periods of phase change materials of 60 and 70 s, respectively.

Thermo-Physical Characterization of Waste-Glass-Induced Packed Bed Material as Thermal Energy Storage Device for Compressed Air Energy Storage System

Abstract The article presents the preparation and testing of packed bed (PB) material to be used as a thermal energy storage (TES) device. The proposed TES device will be used to store the high thermal energy attained during air compression in a compressed air energy storage (CAES) system. The article examines the utilization of mortar-based admixture by incorporating waste glass powder (WGP), graphite powder (GP), and waste glass sand (WGS). The selection of these constituents as a primary ingredient for the PB material has been made based on their availability, cost, and sustainability. The thermo-physical assessment of samples with different proportions of aggregates outlined two categories of PB: the first category of PB with low volumetric heat capacity (CP) for short/quick TES and the second category of PB with high CP for large/longer TES. The study also showcases the importance of GP in enhancing the CP of mortar-based TES devices as a result of high porosity.

The impact of non-ideal phase change properties on phase change thermal energy storage device performance

Phase change materials have been known to improve the performance of energy storage devices by shifting or reducing thermal/electrical loads. While an ideal phase change material is one that undergoes a sharp, reversible phase transition, real phase change materials do not exhibit this behavior and often have one or more non-idealities – glide, hysteresis, supercooling – associated with them. Experimental and modeling techniques to characterize these non-ideal properties are reasonably well understood, however, their impact on the performance of a thermal energy storage system is not fully understood. Here, we analyze the performance of a heat exchanger with a phase change material as a function of the different non-idealities, for a heating and a cooling application. We focus on the impact of these non-ideal behaviors on different modes of operation of the thermal energy storage device, which will serve as a useful guide to researchers on the relative importance of the non-ideal properties, along with the necessary accuracy required during an experimental characterization.

Synergistic enhancement strategy on the heat charging process of a shell-and-tube thermal storage device based on close-contact melting mechanism and nano-enhanced phase change material

Nano-enhanced phase change materials (NePCM) exhibit immense potential for thermal energy storage (TES) applications, due to its improved thermal conductivity. However, its high viscosity can cause a significant deterioration in natural convection. In some cases, even a decrease in the total heat transfer rate can occur in shell-and-tube TES devices after nano-additives loading. Close-contact melting (CCM), featuring heat conduction through micro-liquid film, is regarded as a viable pathway to maximize the advantage of NePCM's high thermal conductivity and weaken the adverse effect of high viscosity on convection. To reveal the synergistic impacts of CCM and NePCM on the charging process of TES device, this study achieved the regulation of CCM by changing the fin configuration, and further analyzed the charging process of NePCM samples with three nano-additives loadings (0 wt%, 1 wt%, and 3 wt%) in TES devices with three different fin configurations. It was shown that expanding the CCM surface can significantly enhance CCM and weaken the contribution ratio of natural convection to the total heat transfer process. Under the experimental conditions established in this study, the best enhancement effect based on the synergistic strategy of NePCM and CCM was achieved, with a remarkable boost of >100 % in power density and a significant shortening of the total melting time to only 52.7 % of the original case. The introduction of CCM in LHTES through reasonable fin configuration is thus regarded as a highly applicable improvement method to enhance the power density, especially used in conjunction with NePCM, exhibiting great potential in the field of high-power-density latent heat storage and thermal management.

SIMULATION OF FLOW AND HEAT EXCHANGE IN A HEAT ACCUMULATOR TANK

The article deals with the research of thermal energy storage tanks. It is proposed to use a «thermal core» to minimize the effects of thermal stratification and high thermal inertia. The thermal core consists of a binary tube placed along the central axis of the tank, filled with a paraffin mixture with a melting point of 45 to 65oC and a density of 0,880 to 0,915g/cm3 at 15oC. In the study the Fluent software package was used to model the temperature distribution in the tank under free convection conditions, the data was then converted to the Transient Thermal module of the ANSYS software package for further calculations of the unsteady temperature distribution in the thermal core. The study showed that a 1400-liter thermal energy storage device, heated for 1 hour by a heat-transfer fluid at 115oC, cools down to 50oC in 4 hours. The research also revealed the need to improve the tank design based on the analysis of the hydrodynamic structure of the flow in the tank, as evidenced by the trajectory distribution of free convective flows. The authors concluded that the use of a heat core, regardless of the type of paraffin used to form it, helps to reduce temperature stratification by height in the tank and that the type of paraffin used has no significant effect on the overall cooling of the tank. However, using ceresin as a core filler results in a slightly higher average tank temperature. Based on the results of the study, the time of complete cooling of the tank was determined by the non-uniform temperature field of all elements of the tank.