Heat Storage Rate Research Articles

Study on heat storage characteristics and carbon optimisation in the sintering process

In response to the phenomenon of automatic heat storage during the sintering process of iron ore, heat balance analysis concerning the main chemical reactions and physical heat carried by gas and solid materials was conducted. A unit heat storage model for the sintering process was established. Further, a mathematical model to solve the heat transfer characteristics between different sintering layer units was proposed and established based on temperature–time curves of the gas and solid phases. Using these models, the heat storage of each layer unit was calculated under the condition of uniform carbon allocation. Subsequently, the optimisation of carbon allocation at each layer unit for maximising the utilisation of heat storage was investigated. The heat required for sintering by the layer unit was taken as the constraint, and the maximum utilisation of heat stored in each layer unit was taken as the goal to optimise the carbon allocation in the height direction. The calculation results show that as the unit thickness is 100 mm and the total thickness of the layer is 600 mm, the heat transfer ratio of the upper unit to the lower unit is 34.22%, 30.29%, 14.74%, 9.49%, and 1.17%, respectively. The heat storage and available heat storage rate increase with the increase of layer height, with heat storage ranging from 0.69 × 104 to 5.14 × 104 KJ/t and heat storage rate ranging from 11.63% to 49.37%. After optimising carbon allocation, the unit achieved a maximum carbon reduction of 60.04%, resulting in an overall reduction in carbon allocation of 46.20%. This adjustment aligns more closely with the industrial processes.

Improving the charging performance of latent heat thermal energy storage systems using triply periodic minimal surface (TPMS) structures

The utilization of latent heat thermal energy storage (LHTES) using phase change materials (PCM) has attracted considerable attention due to their high energy density and thermal regulation. However, the inferior thermal conductivity of PCM has hindered their widespread implementation, triply periodic minimal surface (TPMS) structures could considerably ameliorate the energy storage utilization. TPMS structures offer escalated surface area and pore interconnectivity, which can enhance the apparent thermal conductivity and improve the performance of LHTES systems. This study focuses on investigating the performance and storage capabilities of three unique TPMS structures, namely Gyroid, IWP, and Primitive, at different relative densities and charging temperatures. The computational model is developed, verified, and validated with the relevant experiment results. A comparative analysis of the temperature distribution and liquid fraction evolution in TPMS LHTES units is carried out and compared to pure PCM LHTES. At a charging temperature of 80 °C, compared to the complete melting time of 7206 s for the pure PCM LHTES, the results demonstrate that the G10, IWP10, and P10-PCM LHTES achieve complete melting at 344 s, 276 s, and 368 s, respectively. This affirms the superiority of IWP structures in improving the melting rates due to their escalated surface areas and tortuous paths. The use of TPMS structures improves the total heat storage, heat storage rate, and volumetric heat storage density, while reducing the gravimetric heat storage density, compared to the pure PCM LHTES. The G10-PCM LHTES attains total heat storage, heat storage rate, volumetric, and gravimetric heat storage density of 2120 J, 6.16 W, 63.6 kWh/m3, and 227 kJ/kg, compared to 1910 J, 0.27 W, 57.3 kWh/m3, and 250 kJ/kg for pure PCM LHTES, respectively. Moreover, increasing the relative density of TPMS structures adversely reduces the total heat storage, heat storage rate, and volumetric heat storage density, and significantly increases the heat storage rates. As the charging temperature increases, the complete melting time is reduced and the charging performance indicators are improved, for the pure PCM and TPMS-PCM LHTES units.

Experimental study on an improved direct-contact thermal energy storage container

Direct-contact thermal energy storage (TES) systems characterized by high heat density and rapid heat transfer rates have been exploited for the collection of industrial waste or surplus heat for subsequent utilization. In order to address blockage issue at the initial stage of charging process, an improved direct-contact TES container was developed by incorporating a double-pipe structure at both the inlet and outlet. Within the container, a U-shaped tube serving as the inner tube was concentrically positioned from the inlet to the outlet. Erythritol was selected as the phase change material (PCM), while heat transfer oil (HTO) functioned as the heat transfer medium during experimentation. During the charging process, hot HTO initially flowed through the U-shaped tube, establishing an indirect contact with the PCM. The high thermal conductivity of the U-shaped tube wall expedited the formation of a flow channel within the solid PCM. The duration of forming flow channel was 6 to 13 min. In the discharging phase, the liquid PCM was segregated into convection and conduction zones. The indirect-contact TES experiments were also conducted in the same container. Comparison between indirect-contact and direct-contact TES were analysed from the aspects of phase change behavior, charging and discharging time with the identical container structure and theoretical heat capacity. Results indicated that the direct-contact TES container exhibited superior heat storage and release rates, with the direct-contact discharging time being approximately a quarter of the indirect-contact duration. The phase change behavior of the PCM was notably influenced by the movement of HTO within the direct-contact storage container.

Solar thermal cooking device for domestic cooking applications: Bridging sustainable development goals and innovation

Fossil fuels are vital in the cooking field rather than the automotive sector. Hence, solar cooking has been popularized in recent years due to the rising cost of cooking gas. However, implementing successful renewable energy for cooking in urban area is still challenging for industries. Hence, a solar thermic cooking device with a compact size suited for domestic cooking in urban area is proposed. Thus, the solar cooking device will be developed as a fully functional prototype with necessary supporting modules, depending on the heat transfer fluid (HTF) flow and heat transfer rate between fluids. The main objective is to represent various computational fluid dynamics (CFD) and thermal analysis results on different optimistic designs for a solar thermoelectric cooking device's heat exchanger and storage unit. The 3D part model of the modules has been developed using SOLIDWORKS 2019 software. CFD has also been carried out using the same workspace with an additional package called flow simulation to analyze the flow properties of heat transfer fluid at different rates when circulated in other modules.Moreover, the thermal behavior of the HTF concerning the heat transition between module surfaces is simulated using SOLIDWORKS flow simulation to evaluate the heat storage capacity and rate of heat transfer. The theoretical formulations for the modules are derived through thermodynamic equations concerning the materials and fluid involved in the unit. The thermal and CFD analysis is carried out for different optimistic 3D models based on thermal sustainability, and the results are compared with theoretical analysis, which is discussed in this paper.

Modifying the performance kinetics in the shell-and-multi tube latent heat storage system via dedicated finned tubes for building applications

Phase change materials (PCMs) offer significant potential for building energy management, but are limited by poor heat transfer rates. This study investigates charging/discharging performance optimization of a shell-and-multi-tube heat storage system using high-enthalpy PCM (RT70HC) with differentiated fin configurations. The key novelty of the work lies in its thorough examination of geometric mutations within this system, specifically targeting building energy applications. A validated numerical model simulated charging and discharging processes, comparing finned and plain tube designs. Key performance metrics analyzed here include melting times, heat storage rates, phase transition velocities, and temperature profiles. Results reveal the finned tube design enables a 268 % higher heat storage rate (1421 W vs 387 W) and 74.5 % faster melting time (196 min vs 770 min) compared to the plain tube. Detailed analysis of the 10-h charging process exposes intricate thermal stratification patterns. The inclusion of dedicated discharging finned tubes significantly enhances heat distribution. During the 20-h discharge, heat transfer rates decrease from 2000 W to 100 W, providing crucial insights into solidification dynamics. These quantified findings highlight the potential of optimized finned tube arrays to substantially improve thermal performance of shell-and-multi-tube heat storage systems for building energy applications.

A Study of Asymmetric Hyperbolic Heat Storage Unit

ABSTRACTDue to the advantages of high energy density and constant temperature, phase change energy storage technology has attracted much attention in energy saving and efficient utilization of energy. In this paper, Fluent software is used to simulate and analyze the heat storage characteristics of six new thermal storage units: corrugated tube, hyperbolic‐shape, non‐hyperbolic‐shape, symmetric frustum‐shape, non‐frustum‐shape, and bow‐shape. The results show that the melting rate of the non‐hyperbolic‐shape phase change unit is significantly higher than that of the circular tube, the heat storage time is shortened by 22.52%, and Ra* reaches 0.0086. Second, the effects of the radius difference (δ) between the inlet and outlet of the non‐hyperbolic‐shape phase change unit and the asymmetric position (s) on the heat storage process are studied. The results show that when δ increases from 2 to 10 mm, the melting time of phase change material (PCM) is shortened by 22.89%, that is, the average heat transfer rate between PCM and heat transfer fluid increases with the increase of δ. On the other hand, the average heat storage rate of the heat storage unit decreases first and then increases with the increase of s. When δ = 10 mm, s = 35 mm is the best working condition, the average heat storage rate of the non‐hyperbolic‐shape thermal storage unit reaches 34.3 J/s. This study can provide new ideas and references for the optimization design of latent heat storage units and the progress of experiments.

Experimental analysis on improving heat storage efficiency of high-temperature packed bed system using spherical capsules filled with MgCl2–KCl–NaCl/Al2O3 nanoparticles composite phase change material

While thermal energy storage (TES) systems are becoming crucial to the stable operation of solar power plants, molten salt packed bed thermal energy storage (PBTES) systems attracted widespread attention due to their wide operating temperature range and low cost. However, achieving high-efficiency thermal storage systems is still a datum challenge to meet the higher energy demand, as well as sustainable development and utilization of renewable energy systems. This study developed spherical capsules employing nanocomposite salts (MgCl2–KCl–NaCl/Al2O3 nanoparticles) as composite phase change materials to experimentally study the heat storage process of a high-temperature PBTES prototype experimental system. Also, the heat storage performance of the PBTES system under different operating conditions is further investigated. The results showed that the nanocomposite salt gradually melted along the flow direction of the heat transfer fluid by exhibiting three-stage characteristics including solid phase sensible heat, phase change latent heat, and liquid phase sensible heat. Also, the temperature difference inside and outside the capsules showed the characteristics of peak-trough-peak. The PBTES system reached a heat storage density of 1290.51 MJ m−3 at a thermal efficiency of 86.95 %. The average heat storage rate increased by 49.55 % and the heat storage time was shortened by 29.67 % when the blower speed was increased from 800 r·min−1 to 1200 r·min−1. The experimental results implied that the PBTES system encapsulating nanocomposite salts has excellent thermal performance. This study demonstrated solving the problems of insufficient thermal energy supply in time or space and improving energy utilization could result in a high-efficiency thermal storage system.

Photovoltaic panel cooling with new composite of phase change materials and hierarchical nanoparticles

In this research, the use of a new type of phase change materials (PCM) and hierarchical nanoparticles is discussed to improve the electrical and thermal efficiency of PV panels. TiO2/CuO hierarchical nanoparticles are synthesized by hydrothermal method, and PCMs containing nanoparticles (2.5–10%wt) are prepared, and then experiments are performed in indoor conditions under solar simulator light. The PV panel with a maximum nominal power of 30W is used. The new PCM is made from a mixture of lauryl alcohol and beeswax (LABW). A spiral heat exchanger is placed in the PCM container, in which the flow rate of cool water is variable (m˙ = 0.002–0.01 kg s−1). Firstly, the temperature and voltage-current changes of the PV panel with time are investigated without using PCMs as a reference case, and in steady-state conditions, the temperature and output power values are 67.34 °C and 22.33W. The use of LABW compared to pure beeswax leads to a significant decrease in the PV panel temperature and as a result, an increase in its electrical and thermal efficiency. Also, adding nanoparticles to PCMs from 2.5 % to 7.5 %wt due to the improvement of their thermal conductivity and increasing the heat storage rate of the PV panel leads to an increase in its electrical and thermal efficiency. There is no significant change to decrease the temperature and increase the production capacity of PV panels by increasing the percentage of nanoparticles from 7.5 % to 10%wt. The maximum production power, electrical and thermal efficiency of the PV panel at a flow rate of 0.01 kg s−1, 10%wt of nanoparticles, and a radiation intensity of 1000 W m−2 are 28.92 W, 12.55 %, and 76.67 %, respectively.

Phase change heat storage and enhanced heat transfer based on metal foam under unsteady rotation conditions

Phase change heat storage technology is an essential method for balancing supply and demand in solar energy heat utilization. In this study, a numerical model of the phase change heat storage process is built to explore the impact of non-constant rotation, with and without metal foam. Subsequently, an investigation into the influence of metal foam pore density and porosity on heat storage performance is conducted, with a focus on Taguchi design for statistical analysis. The research delves into the effects of foam parameters on heat storage rate, temperature response, heat storage time, and heat storage properties. Findings reveal significant resolidification in the melting process of this thermal storage structure without metal foam, due to periodic rotation speed hindrance in transferring heat to the outside. Taguchi design results underscore the greater influence of porosity on the melting time and average heat storage rate compared to pore density. Specifically, a reduction in melting time by 62.21 % and 30.49 %, and an increase in average heat storage rate by 237.56 % and 51.19 % is observed when pore density and porosity are 40 PPI and 0.97, compared with the ones with porosities of 0.99 and 0.98, demonstrating minimal impact on total heat absorption.

Analysis on the effect of novel topological optimization fin structures considering eccentricity on the heat storage and release characteristics of shell and tube phase change heat accumulator

Shell and tube phase change accumulator (STPCA), as a common type of heat accumulator, can effectively solve the mismatching of time and space in solar thermal power generation by using phase change storage technology. However, the low thermal conductivity of phase change materials (PCMs) reduces its heat storage and release rate. To achieve a rapid latent heat energy storage and release, it needs to carefully modify the structure of STPCA. In the existing literature, insufficient attention has been given to simultaneously addressing the heat storage and release processes, while there is a scarcity of topological optimization methods employed in fin design. On one hand, it is difficult to find the optimal structure. On the other hand, the optimized structure is suitable for melting process but may not be suitable for solidification process. In this contribution, we initially integrated topological optimization and eccentricity to derive fin structures suitable for respective melting and solidification processes. Then, we compared and analyzed the effects of eccentricity and objective function on melting and solidification processes. Finally, we summarized the topology optimization process, objective function and eccentricity suitable for fast heat storage and release. The findings indicated that as the eccentricity increases, the rate of heat storage and release initially rises before subsequently declining. In this work, it is found that an eccentricity of 5 mm is the best. From the whole heat storage and release cycle, when the eccentricity is 5 mm, the objective function is the minimum temperature difference and the topological optimization fin structure calculated during solidification process shows the best heat storage and release performance. Compared with the topology optimization structure without eccentricity, the heat storage speed is increased by 36.43 %, and the heat release speed is increased by 15.53 %. The design law of the STPCA based on combined with the eccentricity influence and topology optimization method is summarized to help improve its heat storage and release performance.

Analysis of the influence of asymmetric V-shaped fins on the melting of phase change materials in latent heat storage units

Improving the melting performance of latent heat storage devices is highly important for achieving efficient utilization of thermal energy. To achieve this goal, this paper proposes an innovative thermal storage unit with asymmetric V-shaped fins. The influence of structural parameters including eccentricity, fin angle, height and shape on the melting process of phase change materials is analysed. The results show that compared with concentric tubes without eccentricity, when the eccentricity is increased to the point where the bottom fins are in contact with the outer tube, the total melting time is shortened by 33.56%, and the average heat storage rate is increased by 32.95%. At the same time, increasing the angle and height of the top branch fins can strengthen the natural convection in the heat storage unit and shorten the total melting time by 13.54%. It is worth noting that changing the upper-side branch fin parameters has little effect on the melting process. In addition, when the shape of the branch fins constituting the V-shaped fin changes from rectangular to trapezoidal, the total melting time decreases by 3.11%. In summary, the use of asymmetric V-shaped fins can improve the melting performance and heat storage performance of eccentric heat storage units, and changing the fin shape can further shorten the total melting time and increase the average heat storage rate.

Study on electric vehicle thermal management system using phase change materials and CO2 heat pump waste heat recovery under cold conditions

The thermal management system plays a pivotal role in electric vehicle. The CO2 heat pump technology, which performs well at low temperatures and environmentally friendly, has emerged as one of the most promising solutions for optimizing the thermal management system of electric vehicles. However, at −30 ℃ to −15 ℃, the CO2 heat pump faces issues with excessively high discharge temperatures and limited Gas Cooler heat exchange area, thereby there is potential of waste heat recovery and utilization. This paper proposes a thermal management system that utilizes PCM heat storage to recover waste heat from the CO2 heat pump. The system aims to insulate the battery during winter parking, reducing the battery’s preheating energy consumption and enhancing the vehicle’s overall energy utilization efficiency. This paper explored the waste heat characteristics of CO2 heat pump under various conditions. Subsequently, Numerical structural optimization analysis of the PCM heat storage was conducted. Finally, an economic analysis of the PCM heat storage is performed, considering the boundary condition of the urban climate. The result showed that Under the heat production control strategy, the PCM heat storage has a high heat storage rate at −30 ∼ -20 ℃ ambient temperature, reaching 1470 W ∼ 2709 W, and the heat storage time is less than 1 h. At −15 ℃, where the energy saving is maximized, the system battery coupled with the PCM heat heat storage consumes only 0.88 kWh for preheating, saving 44 % compared to the 1.58 kWh consumed by the baseline. The PCM heat storage demonstrates a better energy-saving effect in colder areas.

Numerical study of PCM melting performance in a rectangular container with various longitudinal fin structures

This paper uses the enthalpy-porosity technique to conduct a three-dimensional numerical investigation on the effect of adding longitudinal fins in energy storage units to enhance the melting process, with a specific focus on natural convection. By reducing the extension length of the upper part of the fins and increasing the extension length at the bottom, the work aims to enhance heat transfer while reducing obstruction to convection. The effects of rectangular, trapezoidal, and triangular longitudinal fins with thicknesses of 0.2, 0.25, and 0.3 mm on the melting characteristics were compared while maintaining a constant filling volume of RT42 phase change material (PCM) within the rectangular container. The results indicate that the enhanced heat transfer capacity of fins with different structures increases as the fin length increases. Triangular fins exhibit the most significant heat transfer enhancement effect, with the least hindrance to convection. When the fin thickness is 0.2 mm, the triangular fin decreases the melting completion time by 15.7 %, increases the heat storage rate by 18.7 % compared to the rectangular fin, and exhibits optimal natural convection intensity and temperature distribution in the energy storage unit. Additionally, the maximum flow velocity and average Nusselt number can be increased by 21.2 % and 18.5 %, respectively. It was also found that triangular fins are more suitable for high-temperature working conditions.

Using metal foam and nanoparticle additives with different fin shapes for PCM-based thermal storage in flat plate solar collectors

This research focuses on employing heat transfer enhancement techniques as well as nanoparticles, porous metal foams, and extended surfaces, for the PCM-based thermal energy storage system of a flat plate solar collector. Numerical investigations are carried out for different combinations of the aforementioned techniques, with I-, Y-, and T-shaped fins as the extended surface. The mathematical model is developed with porous media equations, where nanoparticles are embedded in the PCM under the assumption of an equivalent single-phase medium. Results suggest that employing these techniques one by one augments heat transfer performances in terms of reduced melting time. The addition of both metal foam and nanoparticles in the straight wall (case A) reduces melting time by 85.16% when compared to the pure-PCM case, while a 84.38% reduction is reached if only foams are employed. The I-shaped fins (case B) are shown to have an impact too; they provide a 37.07% melting time reduction with only PCM, reaching 89.68% and 86.19% with nanoparticles with foams, respectively. This means that metal foams have a primary role in reducing melting time, where nanoparticles and I-shaped fins become helpful too. Furthermore, by considering all techniques together, the heat storage rate increases by an order of magnitude.

Effect of composite fin structure on phase change heat storage tank: A numerical investigation

This study investigates the phase change heat storage process in the hot water displacement system. The PCHS unit incorporates V-shaped fins and straight fins to enhance heat transfer, with the additional enhancement of annular fins. Numerical simulation is used to examine the impact of fin structure and quantity on the evolution of internal flow rate, liquid phase, and temperature during the heat charging process. The response of different fin structures to parameters such as melting time, heat storage rate, storage capacity, and dimensionless temperature is analyzed. The results indicate that Model-6 (4 V-shaped fins + annular fins) exhibits the shortest melting time, reduced by 52.13 % compared to Model-1 (initial structure). The melting time of Model-4 (4 straight fins + annular fins) and Model-6 shows little difference, during the final melting stage, attributed to the good heat transfer performance of the bottom fin in Model-4. Furthermore, the total heat absorption of Model-4 and Model-6 is decreased by 3.92 % and 3.20 % respectively compared to Model-1, while the mean rate of heat storage is increased by 100.20 % and 102.21 % compared to Model-1, demonstrating the significant improvement in heat storage performance with annular fins. Additionally, the same number of V-shaped fins and straight fins, when paired with annular fins, exhibit minimal differences in their strengthening effects, with V-shaped fins enhancing pre-melting and mid-melting, and straight fins showing advantages for end-melting.

Mitigating low-temperature corrosion in flue-gas heat exchangers for improving thermal storage efficiency in geothermal power plants

Geothermal energy is a renewable and stable energy source that plays a crucial role in providing heat. However, underground sulfur fumes have been restricting the heat exchange and storage rate for years. Accurately predicting the condensation of acidic substances of flue gas heat exchangers is crucial in geothermal heat storage. In this paper, Acid and water vapor have been firstly utilized to forecast the deposition of acidic substances on the heat exchanger’s surface. Utilizing gas–liquid equilibrium data of H2SO4-H2O solution and multi-component transport theory, a numerical model has been developed to analyze the impact of acidic deposition and corrosion characteristics. The results shown a correlation between the distribution of acidic substances deposition within heat exchanger and temperature distribution. When water vapor volume fraction increased from 3 % to 18 %, there was a corresponding increase of acid condensation rate on surface. Specifically, the condensation rate increased by 9.6 %, 16.1 %, and 21.8 % respectively under the flow rates of 5 m/s, 8 m/s, and 10 m/s, while the acid mass fraction decreased by 22.4 %, 20.7 %, and 20.1 % respectively. Acidic substances predominantly deposit in specific areas of the heat exchanger. Moreover, Water vapor content increasing can lead to reduction deposition of acidic substances, this may be a potential method to reduce loss of heat exchanger and increase heat storage. These findings offer a significant step forward heat exchanger technology and geothermal energy application.

Development of Macro-Encapsulated Phase-Change Material Using Composite of NaCl-Al2O3 with Characteristics of Self-Standing

Developing thermal storage materials is crucial for the efficient recovery of thermal energy. Salt-based phase-change materials have been widely studied. Despite their high thermal storage density and low cost, they still face issues such as low thermal conductivity and easy leaks. Therefore, a new type of NaCl-Al2O3@SiC@Al2O3 macrocapsule was developed to address these drawbacks, and it exhibited excellent rapid heat storage and release capabilities and was extremely stable, significantly reducing the risk of leakage at high temperatures for industrial waste heat recovery and in concentrated solar power systems above 800 °C. Thermal storage macrocapsules consisted of a double-layer encapsulation of silicon carbide and alumina and a self-standing core of NaCl-Al2O3. After enduring over 1000 h at a high temperature of 850 °C, the encapsulated phase-change material exhibited an extremely low weight loss rate of less than 5% compared with NaCl@Al2O3 and NaCl-Al2O3@Al2O3 macrocapsules, for which the weight loss rate was reduced by 25% and 10%, respectively, proving their excellent leakage prevention. The SiC powder layer, serving as an intermediate coating, further prevented leakage, while the use of Al2O3 ceramics for encapsulation enhanced the overall mechanical strength. It was innovatively discovered that the Al2O3 particles formed a network structure around the molten NaCl, playing an important role in maintaining the shape and preventing leakage of the composite thermal storage phase-change material. Furthermore, the addition of Al2O3 significantly enhanced the rapid heat storage and release rate of NaCl-Al2O3 compared to pure NaCl. This encapsulated phase-change material demonstrated outstanding durability and rapid heat storage and release performance, offering an innovative approach to the application of salt phase-change materials in the field of high temperature rapid heat storage and release and encapsulating NaCl as a high-temperature thermal storage material in a packed bed system. Compared with conventional salt-based phase-change materials, the developed product is expected to significantly improve the reliability and thermal efficiency of thermal storage systems.

Thermal performance augmentation of honeycomb metal matrix embedded phase change material in shell-tube latent heat storage unit

Due to the global warming challenge, there is a transition from the utilization of fossil fuels to harvesting new and renewable energy sources globally. Solar energy, being the infinite source with easy accessibility, leads the race among other allied sources. However intermittent nature of it demands an efficient thermal energy storage system. In the present experimental study, an innovative heat transfer augmentation technique i.e. aluminium honeycomb grill and fine mesh embedded in PCM is demonstrated. Both visualization of PCM melt fraction and capture of temperature contour complemented each other to identify the honeycomb version (HC-LHSU) as substantially better (43 % improvement in charge period) than the base model (BM-LHSU). On the other side, due to fine pores (porosity = 95 %), the fine meshmodel (FM-LHSU) yielded poorer results than BM-LHSU. Even the temperature gradient that exists during the charge or discharge period is gauged and recognized HC-LHSU as the best, followed by BM-LHSU and FM-LHSU. Since the onset of the phase transition zone reflects heat storage rate, the same is identified, and the charge period (sensible heat + latent heat) assessed to be 8000 s, 10000 s, and 12,000 s for HC-LHSU, BM-LHSU, and FM-LHSU, respectively. Further, an improvement in the average Nusselt number by 74 % and 67 % during the charge and discharge period respectively compared to the base model justified the honeycomb grill's role in augmenting the energy storage unit's performance.

Durable and reliable thermal management system with superior temperature uniformity for sidewall coring tool in extreme thermal environments

The sidewall coring tool (SCT) plays a crucial role in exploring the distribution of oil and gas resources, which needs to operate in a challenging high temperature (205 °C) and vibrating downhole environment for 21 h. However, the internal electronics are unable to withstand such extreme temperatures. Previous investigations on thermal management of downhole electronics have failed to ensure long operational duration and reliability. To solve this issue, a durable and reliable thermal management system (TMS) with superior temperature uniformity was proposed for the SCT in this paper. First, the proposed system adopted heat storage modules (HSMs) with high heat storage density and heat diffusion coefficient to enhance the heat storage rate and extend the operational duration. Second, HSMs were utilized for storing heat from nearby heat sources to improve temperature uniformity. Meanwhile, the reliability of HSMs was verified by high-temperature vibration experimental tests. Finally, through iterative optimization, the system utilized a well-designed configuration of thermal insulators and HSMs to further improve temperature uniformity, thereby extending the operational duration of the system. The performance of the total system was evaluated by thermal simulations. The maximum temperature of the heat sources remained below 150 °C after 21 h, with a maximum temperature difference between any two sources not exceeding 12 °C. Furthermore, the experiment was conducted to validate the simulated results, with the relative error within 5 %. The proposed TMS demonstrates a significantly extended operational duration and improved reliability compared to previous works, which has been successfully applied to downhole operations.

Analysis and comparative assessment of charging dynamics in vertical multi-channel latent heat storage system with corrugated wavy channels

Latent heat thermal energy storage (LHTES) is a promising technology, but thermal response limitations caused by the relatively poor thermal conductivity of phase change materials (PCMs) remains an issue. In recent years, computational fluid dynamics (CFD) has proven to be a powerful and reliable tool in design optimization of different systems and problems in the energy sector. Building on that, the present work will use CFD to investigate the thermal performance enhancements achieved using vertical double-tube LHTES systems with multi-channel sinusoidal wavy geometries. The main parameters investigated here are the wavy channel height (H), pitch (P) and the number of channels (N) and the results are assessed in terms of melting rates and heat transfer coefficients. The analysis found that increasing the height from 1 mm to 3 mm, accelerated the phase change by 21 %, while reducing the pitch from 12.5 mm to 5 mm, enhanced the heat storage rates by 28 %. In addition, increasing the number of channels from 3 to 7 improved the charging rate by 64 %. Compared to a conventional straight channel, the enhanced wavy channel (N = 7, H = 3 mm, P = 5 mm) achieved 80 % higher thermal storage rate and 42 % faster charging time. The above findings provide new insight into the potential of utilizing compact vertical LHTES systems via customized wavy channels, with significant impact towards enhancing the existing thermal energy storage systems.