High Volumetric Heat Research Articles

Radiative heat transfer to enhance the performance of liquid metal-based phase change heat sink under natural convection condition

Liquid metal phase change materials have the advantages of high thermal conductivity and high volumetric latent heat, which are expected to address the growing challenges of thermal management of advanced electronics. In previous studies, the effect of radiative heat transfer from fins of a phase change heat sink on thermal management performance has rarely been considered. In this study, radiative coating materials with high emissivity were prepared and coated on the fins of the liquid metal phase change heat sink. The effect of radiative heat transfer on the performance of liquid metal phase change heat sink was investigated. The experimental results of continuous heating under natural convection conditions show that the introduction of the radiative coating with an emissivity of 0.9298 can extend the time for the surface temperature of the heat source to reach 100 °C by 9.4%, while shortening the recovery time of the phase change heat sink by 14.9%. The results of high-power cyclic heating indicate that the high emissivity coating can reduce the peak temperature by 16.6 °C in the tenth working cycle. A simplified numerical model was subsequently developed and validated to determine the specific effects of phase change and radiative heat transfer on the overall thermal control performance. The radiation-enhanced liquid metal phase change heat sink proposed in this study is simple and maintenance-free. It is expected to address the thermal management issues of electronic devices that cannot use active cooling or operate in thin-air environments.

Continuous processing of JP-10 production: Hydroisomerization of endo-tetrahydrodicyclopentadiene to exo-tetrahydrodicyclopentadiene using a novel bimetal catalyst of Ba/Se supported on TiO2/SO4

High-energy-density liquid fuels can be utilized as an energetic supplement to conventional fuels and are essential for volume-limited aerospace vehicles to boost payload and flying range. JP-10 has attracted much attention because of its high density, flash point, high volumetric heat, and low freezing point. Here we report the hydroisomerization of endo-tetrahydrodicyclopentadiene to exo-tetrahydrodicyclopentadiene (the main component of JP-10) was investigated over the TiO2/SO4 supported Ba(10 %)/Se(5–20 %) catalysts. This work aims to examine changes in continuous processing settings to maximize exo-THDCPD production, selectivity, and conversion. It was discovered that the synthesized TiO2/SO4/Ba(10 %)/Se(5–20 %) heterogeneous catalysts were novel, more effective, affordable, environmentally friendly, and simple to produce. The catalyst’s physicochemical characteristics were examined using FT-IR, BET, XRD, HR-SEM, HR-TEM, TGA and NH3-TPD. The produced TiO2/SO4/Ba(10 %)/Se(5–20 %) nano-catalysts have good catalytic activity and a wide range of active Lewis and Brønsted acid sites. Evaluation of the isomerization of endo-THDCPD to exo-THDCPD was conducted in a high-pressure fixed-bed continuous reactor operating at 200 °C, 20 bar of pressure, and 4.0mol/h of H2 flow rate. According to the investigations, the synthesized catalyst with a 15 % Se load performs exceptionally well, exhibiting 100 % conversion, 98.5 % selectivity, and 98.5 % yield at an H2 flow rate of 10 ml/min. The isomerized product is used in Jet Propellant-10, a high-density fuel. Under ideal circumstances, exo-THDCPD with a high degree of purity (>98 wt%) was produced without the need for any sort of separation technique.

Electroless Deposition of Ni Nanoparticles on Boron Particles: Physicochemical and Oxidation Properties

Elemental boron also has a high volumetric heat of combustion (136 kJ/cm3), the third highest gravimetric heat of combustion (58.5 MJ/kg) and its oxidation is a highly exothermic process. All these features make boron an attractive constituent of propellants, explosives, and high energy density solid fuels for air-breathing propulsion as an energetic material. Given these uses, researchers have worked on the ignition and combustion processes of boron. However, boron has several serious issues that limit its practical use, including large ignition delay, inefficient combustion, and a complex burning process in solid propellants due to the formation of a defensive boron oxide (B2O3) layer on the boron surface. Previous studies have found that the ignition and combustion performance of boron can be improved by coating it with metal particles, metal oxides, or organic materials, as well as by removing the boron oxide layer.In the literature, there are limited studies on metal particle coating of a boron surface using the electroless Ni plating method. The electroless coating has several impressive advantages over conventional electrolytic coating. The prime advantage is that electroless plating does not require any electricity to operate and is a low-cost process. Among other advantages, it provides a uniform coating and can be used with all kinds of substrates with complex shapes. Conductive and non-conductive materials/powders can be coated with constant thickness with good adhesion.The present work investigated Ni nanoparticle coating on irregularly shaped/non-spherical boron particles using the electroless Ni-plating method at room temperature to prevent the oxidation of boron particles. This is preferable since it is very difficult to coat large quantities at relatively high temperatures. The four different simple paths were chosen during the electroless Ni plating to coat Ni on boron particles: no rinsing and no drying (Path A), only drying (Path B), both rinsing and drying (Path C) and only rinsing (Path D). Previous studies have explored the effect of bath concentration, pH, and temperature on the Ni coating. However, the influence of the four different paths mentioned above on Ni coating with boron particles or any other materials has rarely been investigated. Surface morphology confirmed the Ni nanoparticles coating on the surface of boron particles. The size of the Ni nanoparticles varied between 10 and 120 nm concerning the chosen paths used for preparation using TEM. XRD characterization results of the Ni coated boron particles showed the formation of crystalline Ni nanoparticles. EDAX and XPS results showed the presence of the primary B and Ni elements in samples synthesized in the present study. Thermogravimetric analysis conducted in air atmosphere found the boron particles coated with Ni nanoparticles had enhanced oxidation resistance compared to bare boron particles. Also, the Ni coated boron particles showed a shift in exothermic peak to a lower temperature and higher heat evolution than the bare boron particles.Acknowledgements:This work was supported by the National Research Foundation (NRF) of Korea grant funded by the Korea government (MSIT) No. 2019R1A2C1010862, 2022R1A2C2013508

Synergistic Enhancement on Ignition and Combustion Properties of Boron via Viton Core-Shell Coating.

The high gravimetric (58.74 kJ/g) and volumetric (137.45 kJ/cm3) heat values loaded in boron (B) offer significant potential for application in solid propellants and explosives. However, the high melting (2076 °C) and boiling (3927 °C) points of boron powder and the low melting point (450 °C) of oxidation products affect the energy performance and application of boron. Fluorine-containing polymers have high oxidation potential and excellent mechanical properties and can produce expectant gaseous products through the combustion reaction with boron oxide, but research examining the interaction between purified boron powder and fluoropolymers and the optimal selection of the fluoropolymer remains scarce. Herein, the binding energy between typical fluoropolymers [Viton, polyvinylidene fluoride, poly(vinylidene fluoride-co-chlorotrifluoroethylene), and vinylidene fluoride] and boron was calculated via molecular dynamics simulations, which shows that Viton is an appropriate candidate for coating boron powder. In the experiment, The Bw@Viton core-shell composites were prepared using Viton as the coating layer, and boron powder was pre-purified with acetonitrile. Its structure, thermal properties, ignition, and combustion characteristics were then characterized. The results revealed successful removal of the oxide layer, and the hydrophobicity was significantly improved after Viton coating. Purification and coating synergistically enhance the energy release of boron powder, and the composites demonstrated excellent thermal, ignition, and combustion performances. In particular, the heat of oxidation and heat of combustion were increased by 26.6 and 32.7%, respectively. The ignition delay time was reduced by 53.2% compared to raw boron. A prospective reaction mechanism between boron and Viton is thus proposed.

Effect of different particle sizes on combustion characteristics of DCR engines

The ramjet engine has undergone rapid development in recent decades, and the dual combustion chamber ramjet (DCR) engine was proposed in the last century. Boron, with its high volumetric and gravimetric heating values, is one of the most attractive fuel additives for ramjet engines. However, due to the problem of low combustion efficiency, boron is difficult to achieve high efficiency combustion in practical applications. In order to investigate the combustion characteristics of boron-containing gas solid phase components in DCR engines, the Realizable k-ε model, finite rate/vortex dissipation model and boron particle King model ignition combustion calculation program were written. A three-dimensional full-scale two-phase flow numerical simulation was carried out in the combustion chamber of the DCR engine to calculate the effects of different particle sizes on the combustion characteristics. Through the analysis of the simulation results, the particle size affects the ignition time of boron particles and is positively correlated with the combustion efficiency, but with a non-linear growth. A smaller particle size can promote the ignition of boron particles, improve the solid phase combustion efficiency and achieve efficient combustion.

A novel thermal-tailored strategy to mitigate thermal cracking of cement-based materials by carbon fibers and liquid-metal-based microencapsulated phase change materials

Massive concrete structures are susceptible to thermal cracking due to the large surface-to-internal temperature gradients induced by the exothermic cement hydration, threatening their durability and safety. This study explored a novel thermal-tailored strategy to mitigate thermal cracking of cement-based materials by incorporating carbon fibers (CF) and liquid-metal-based microencapsulated phase change materials (MEPCM). Specifically, spherical MEPCM composed of In-Bi-Sn alloy cores coated by polyvinyl alcohol shells was prepared through a high-speed liquid-phase dispersion method, with average diameters of 36.26 μm and a high volumetric latent heat of 214 MJ/m3. The synergistic effect of CF and MEPCM on the microstructure, mechanical and thermal properties of cement mortars was further investigated. Upon adding 0.3 wt% of CF and 3.2 vol.% of MEPCM, the flexural strength of cement mortars exhibited a significant increase of 30.3 %. Microanalysis revealed that the molten MEPCM could flow to fill the pores and microcracks within its surrounding matrix and form a network skeleton with well-dispersed CF, imparting flexibility to the typically rigid cement hydrates. By this way, the thermal conductivity of cement mortars was increased by 21.7 % and internal temperature rise was decreased by 12 ℃ by adding 4.8 vol.% of MEPCM, contributing to the mitigation of risks associated with thermal cracking. The research outcomes will provide valuable insights into the development of thermal cracking-resistant cement-based materials in a highly efficient way.

Utilizing Ragone framework for optimized phase change material-based heat sink design in electronic cooling applications

This study explores the latent thermal energy storage potential of an organic phase change material with porous copper foam and its applicability in electronic cooling under varying heat load conditions. The organic phase change material, n-eicosane, is known for its inherently low thermal conductivity of 0.15 W/mK, rendering it vulnerable during power spikes despite its abundant latent heat energy for phase transition from solid to liquid. Porous copper foams are often integrated into n-eicosane to enhance the composite's thermal conductivity. However, the volume fraction of the phase change material in the porous foam that optimally improves the thermal performance can be dependent on the boundary condition, the cut-off temperature, and the thickness. A finite difference numerical model was developed and utilized to ascertain the energy consumption for the composite of n-eicosane with two kinds of porous copper foam with varying porosity under different heat rates, cut-off temperatures, and thickness. In addition, the results are compared with a metallic phase change material (gallium), a material chosen with a similar melting point but significantly high thermal conductivity and volumetric latent heat. For validation of the numerical model and to experimentally verify the effect of boundary condition (heat rate), experimental investigation was performed for n-eicosane and high porosity copper foam composite at varying heat rates to observe its melting and solidification behaviors during continuous operation until a cut-off temperature of 70 °C is reached. Experiments reveal that heat rate influences the amount of latent energy storage capability until a cutoff temperature is reached. For broad comparison, the numerical model was used to obtain the accessed energy and power density and generate thermal Ragone plots to compare and characterize pure gallium and n-eicosane - porous foam composite with varying volume fractions, cutoff temperature, and thickness under volumetric and gravimetric constraints. Overall, the proposed framework in the form of thermal Ragone plots effectively delineates the optimal points for various combinations of heat rate, cut-off point, and aspect ratio, affirming its utility for comprehensive design guidelines for PCM-based composites for electronic cooling applications

Combustion performance of aluminum modified boron nanoparticles coated with silane coupling agent

Boron (B) powder, with its high mass and volumetric heat values, makes it highly promising in the field of energetic materials. However, the oxide layer on the B surface is the most significant barrier to realizing its full potential as a fuel. How to eliminate or disrupt the oxide layer is currently an urgent problem that needs to be addressed. This study proposes an approach to enhance the combustion of nano-B powder by coating aluminum (Al) onto its surface using a silane coupling agent. The combustion characteristics of Al-modified B powder with different Al contents were investigated through experimental and molecular dynamic simulation methods, and the bidirectional diffusion mechanism on the interfacial layer of modified B particles was revealed. A small amount of Al powder can largely lower the initial oxidation temperature of B powder, increase the maximum flame temperature, and enhance the heat release. However, an excessive amount of Al powder leads to a deterioration in the combustion of B powder but can alter the combustion behavior and suppress the aggregation of B powder during the combustion. Additionally, combination reaction and redox reaction occurring during the combustion of B@Al samples not only reduce the burning time of B powder but also accelerate the flame expansion speed and improve the combustion efficiency. These results lay the foundation for the application of B@Al in the field of energetic materials.

Mechanism and kinetics of catalytic decalin alkylation for the synthesis of high-performance fuel

Alkyl decalins are promising jet fuel components with high density and well cryogenic properties, but are difficult to obtain. Here we bring up a facile approach to synthesize methyl-substituted decalins including methyl decalin, dimethyl decalin and trimethyl decalin via catalytic alkylation reaction. The reaction conditions are optimized to obtain the high decalin conversion of 83.1 %. Based on a series of experiments, it is indicated that the intermediate complex formed by tetramethylsilane, aluminum chloride and dichloroethane is the key to accelerate the reaction rate, and the reaction mechanism is proposed. Moreover, a pseudo-first-order irreversible reaction dynamics is studied, and the reaction kinetics parameters and reaction rate equati andons are obtained. After vacuum distillation, the fuel product shows high density (0.872 g/cm3) and high volumetric neat heat of combustion (36.9 MJ/L), much higher than those of RP-3 fuel. This work provides a facile method to synthesize high-performance jet fuel.

Mechanism and kinetics of self‐sensitized photocycloaddition of cyclohexenone and norbornene

AbstractSolar‐driven conversion of renewable biomass resources into high‐density hydrocarbon fuels can effectively realize biomass valorization and renewable energy conversion. In this work, an efficient self‐sensitized [2 + 2] photocycloaddition process is explored to develop highly strained fuel with high yield using norbornene and biomass‐derived cyclohexenone as feedstocks. The enhancement mechanism is revealed by phosphorescent measurement and theoretical calculation, and a reasonable reaction path for self‐sensitized [2 + 2] co‐cycloaddition is proposed. When using methanol as solvent, the apparent activation energy of co‐cycloaddition is 21.37 W/mol, which is lower than that of self‐cycloaddition (31.57 W/mol). Importantly, the jet‐fuel‐range highly strained fuel has high density (0.986 g/cm3) and high volumetric net heat of combustion (41.14 MJ/L), which are 5.34% and 4.39% higher than those of JP‐10, respectively. This work proposes a green and effective pathway for the preparation of high‐performance hydrocarbon fuel with polycyclic‐asymmetric structure.

Accelerating the Design of High-Energy-Density Hydrocarbon Fuels by Learning from the Data.

In the ZINC20 database, with the aid of maximum substructure searches, common substructures were obtained from molecules with high-strain-energy and combustion heat values, and further provided domain knowledge on how to design high-energy-density hydrocarbon (HEDH) fuels. Notably, quadricyclane and syntin could be topologically assembled through these substructures, and the corresponding assembled schemes guided the design of 20 fuel molecules (ZD-1 to ZD-20). The fuel properties of the molecules were evaluated by using group-contribution methods and density functional theory (DFT) calculations, where ZD-6 stood out due to the high volumetric net heat of combustion, high specific impulse, low melting point, and acceptable flash point. Based on the neural network model for evaluating the synthetic complexity (SCScore), the estimated value of ZD-6 was close to that of syntin, indicating that the synthetic complexity of ZD-6 was comparable to that of syntin. This work not only provides ZD-6 as a potential HEDH fuel, but also illustrates the superiority of learning design strategies from the data in increasing the understanding of structure and performance relationships and accelerating the development of novel HEDH fuels.

Improving rheological and thermal performance of Gilsonite-Modified binder with phase change materials

Gilsonite, as a type of natural asphalt binder, has been used to improve the high-temperature performance of regular asphalt binders. However, the addition of gilsonite may compromise binders’ low-temperature thermal cracking resistance. In this research, polyethylene glycol (PEG), as one type of the phase change materials (PCMs), was used as an innovative material to balance the impacts of gilsonite on high and low performance of asphalt binders. The dosages of gilsonite and PEG were first determined based on the materials’ rheological behaviors at low temperatures. The performance of the PEG-gilsonite-modified binder was then fully evaluated in terms of the resistance to cracking and rutting at various temperatures. Thermal tests were also conducted to assess the thermal behaviors of the modified binders. The testing results indicate that with the proper dosage of gilsonite and PEG, the rutting resistance of the binder can be improved without sacrificing its low-temperature performance. With the addition of the PCM, the binder was tested to have high volumetric heat capacity, which indicates PCM can reduce the rate and the magnitude of the temperature changes in pavements.

Ignition and combustion characteristics of boron-based nanofluid fuel

With its high gravimetric and volumetric heat value, boron-based nanofluid fuel is potentially well suited for future high-energy propulsion systems. In this experimental study, we investigate the ignition and combustion of boron-based nanofluid fuel, with a focus on the effects of oleic acid (OA) concentration (0 to 10 wt.%), boron particle concentration (2.5 to 20 wt.%), and boron particle size (300 nm to 13 µm). Thermogravimetry−differential scanning calorimetry and laser ignition tests reveal that adding boron nanoparticles to a fuel can improve its combustion intensity, but without much affecting the oxidation and ignition characteristics, primarily because of agglomeration and thicker oxide layer properties relative to boron microparticles. Pure kerosene droplets are found to undergo pre-ignition heating and classic combustion, whereas OA or boron addition promotes puffing and micro-explosions, accelerating the classic combustion process. The co-existence of OA and boron is found to lead to more frequent and stronger disintegration of the nanofluid fuel droplet. The ignition delay reaches 156 ms with only 2.5 wt.% OA inclusion, compared to just 73 ms for pure kerosene. Both the ignition delay and combustion rate increase, while the solid residual decreases owing to enhanced micro-explosions as the OA concentration increases. Unlike OA, boron addition promotes ignition, with 2.5 wt.% boron yielding an ignition delay reduction of 24 ms, but this effect weakens with increasing boron concentration. The combustion rate is found to be relatively insensitive to boron addition. Although the particle size affects the ignition and combustion performance of boron powder, its effect on the combustion of the nanofluid fuel droplet is, under the present test conditions, relatively weak. Finally, a phenomenological model is presented to capture the ignition and combustion of a boron-based nanofluid fuel droplet. The predicted ignition delay and combustion rate are found to be within 7.15% of their experimental values. This study contributes to an improved understanding of boron ignition and combustion in high-energy liquid fuel systems.

Pd/C catalytic cyclopropanation of polycyclic olefins for synthesis of high‐energy‐density strained fuels

AbstractCyclopropane derivates are appealing to synthesis of high‐energy‐density fuels because of the high strained energy of the three‐numbered ring. The catalytic cyclopropanation of olefin with diazomethane is very effective to construct the carbocycle. The majority of the catalysts employed are nonrecyclable homogeneous compounds. Herein, we report cyclopropanation of polycyclic olefins catalyzed by heterogeneous Pd/C. The optimal cyclopropanation conditions were explored utilizing dicyclopentadiene as model substrate and a series of polycyclic olefins were cyclopropanated with high yield. Additionally, the catalyst has good recyclability and stability, as shown by characterizations as well as the fact that no inactivation happens after cyclopropanation. The synthesized cyclopropane derivates exhibit good fuel characteristics like high density (1.006–1.087 g/cm3), high volumetric net heat of combustion (42.58–46.45 kJ/cm3), good low‐temperature and combustion performance. This work shows industrial potential for cyclopropanation of polycyclic olefins with diazomethane.

Performance improvement of a 4 K GM/magnetic hybrid refrigerator with a new magnetic regenerator

A hybrid refrigerator that combines the GM refrigeration effect with the magnetic refrigeration effect has been built before. Based on the hybrid refrigerator, a new magnetic regenerator filled with Pb, ErNi and EuTi0.875Al0.125O3 has been constructed to improve the cooling performance of the hybrid refrigerator. Among the three regenerative materials, EuTi0.875Al0.125O3 is a newly developed ferromagnetic material with high volumetric specific heat and large magnetocaloric effect below 5 K, which is better than the TmCuAl used in the previous regenerator. The numerical prediction shows that the new magnetic regenerator filled with EuTi0.875Al0.125O3 could obtain a lower cooling temperature and a larger cooling power in the hybrid refrigerator. Then, the cooling performance of the new magnetic regenerator has been systematically studied by experimental tests. In the experiments, the minimum no-load temperature of the new magnetic regenerator could reach 2.48 K, which was much lower than the minimum no-load temperature of 3.5 K in the previous regenerator. Meanwhile, the cooling power of 0.652 W at 4.2 K was produced in the new magnetic regenerator, which was larger than the previous regenerator by 0.361 W, and the corresponding relative Carnot efficiency was 0.48 % at 4.2 K in the new magnetic regenerator.

A robust scheme for numerical simulation of heat transfer in two-fluid flows with high volumetric heat capacity contrasts

PurposeThis paper aims to propose a new method for robust simulations of passive heat transfer in two-fluid flows with high volumetric heat capacity contrasts.Design/methodology/approachThis paper implements a prediction–correction scheme to evolve the volumetric heat capacity. In the prediction substep, the volumetric heat capacity is evolved together with the temperature. The bounded downwind version of compressive interface capturing scheme for arbitrary meshes and central difference scheme are used for the spatial discretization of the advection and diffusion terms of the heat transfer equation, respectively. In the correction substep, the volumetric heat capacity is updated in accordance with the interface captured by using a coupled level-set and volume-of-fluid method to capture the interface dynamics precisely.FindingsThe proposed method is verified by simulating the advection of a hot droplet with high volumetric heat capacity, a stationary air–water tank with temperature variation between top and bottom walls and heat transfer during wave plunging at . The test results show that the proposed method is practical and accurate for simulating two-fluid heat transfer problems, especially for those feature high volumetric heat capacity contrasts.Originality/valueTo ensure the numerical stability, this paper solves an additional conservative form of volumetric heat capacity equation along with the conservative form of temperature equation by using consistent spatial-discretization and temporal-integration schemes.

Kinetic Decomposition Models for Ammonium Percholorate Hybrid Catalyzed with Nanothermite Particles

Ferric oxide is a universal catalyst. Reactive metal fuel can act as a high energy dense material such as aluminum which is marked by the very high gravimetric and volumetric heat output. This manuscript reports on the fabrication of colloidal ferric oxide nanoparticles of 5 nm. Colloidal ferric oxide/aluminum nanothermite mixture was integrated into ammonium percholorate (AP) via the coprecipitation technique. The shape and particles size of the prepared nano ferric oxide were investigated by using TEM instrument. Uniform dispersion of Al/Fe2O3 in the ammonium perchlorate matrix was verified using EDAX instrument. Nanothermite particles offered enhanced AP decomposition enthalpy by 120 % using DSC. Nanothermite colloid offered a decrease in AP activation energy by 51 and 40 % using Friedman and Ozawa models respectively. AP decomposition mechanism was reported to go through three consequent mechanisms including the first order mechanism, two-dimensional diffusion reactions, and one- dimensional diffusion mechanism according to extent of reacted fraction (α) of 0-0.25, 0.3-0.6, and 0.6-0.9 respectively. The results show that the catalyzing ability of the nanothermites was confirmed and has shown a superior effect on the AP energetic system.

Molten salts: Potential candidates for thermal energy storage applications

Molten salts as thermal energy storage (TES) materials are gaining the attention of researchers worldwide due to their attributes like low vapor pressure, non-toxic nature, low cost and flexibility, high thermal stability, wide range of applications etc. This review presents potential applications of molten salts in solar and nuclear TES and the factors influencing their performance. Ternary salts (Hitec salt, Hitec XL) are found to be best suited for concentrated solar plants due to their lower melting point and higher efficiency. Two-tank direct energy storage system is found to be more economical due to the inexpensive salts (KCl-MgCl2), while thermoclines are found to be more thermally efficient due to the power cycles involved and the high volumetric heat capacity of the salts involved (LiF-NaF-KF). Heat storage density has been given special focus in this review and methods to increase the same in terms of salt composition changes are discussed in the paper. Methods of concatenating energy storage systems with nuclear power plants are also discussed with different types of nuclear reactors like MHTGR, PAHTR, VHTR, etc. Nanomodifications of molten salts are done to improve heat transfer properties and efficiency of the transfer. The best dopants for such modifications were found to be TiO2, SiO2, MWCNTs, etc. Future challenges for large scale deployment of molten salts viz., high volume expansion ratio, low thermal conductivity, incongruent melting, corrosion, etc., are listed and discussed. Corrosion of molten salts and its mitigation has been discussed in detail for developing next-generation storage systems and its remedies are also discussed.

Preliminary finite element analysis of the stainless-steel liner of the maintainable test cell concept of IFMIF-DONES

• New maintainable design concept in fusion related facility. • Preliminary mechanical finite element analysis of an unusual shaped vacuum vessel. • Pareto front tradespace study for stiffening structure optimal variants. The main purpose of IFMIF-DONES facility is to provide a neutron source for irradiating small specimens and producing experimental data of material properties for the construction of DEMO fusion power plant. The Test Cell (TC) of the DONES is a confined and well-shielded room, where the strong irradiation environment is created. The biological shielding of the TC mainly consists of several meters thick concrete walls and shielding plugs, and a stainless-steel liner. The TC liner and the concrete walls are actively cooled by water because of the high volumetric heating coming from nuclear reactions. Although, the TC is designed to be fully functional for the complete life span of the facility, still there is a very low probability of defect of the TC biological shielding due to their exposure of intense neutron and gamma irradiation. Therefore, the original TC configuration, which was a monolithic approach, had to be revised. Due to this reason, at the end of 2019 the project team has changed the TC concept from the monolithic design to the so-called Maintainable TC Concept (MTCC) design, which allows a maintenance possibility in case of unexpected damage.

Pyrolysis mechanism of tetrahydrotricyclopentadiene by ReaxFF reactive molecular dynamics simulations

Tetrahydrotricyclopentadiene (THTCPD) has high density and volumetric heat, but its viscosity is also high, resisting its ignition and combustion, which somewhat limits its applications. Therefore, it is crucial to understand the mechanism of THTCPD pyrolysis. In this study, the ReaxFF reactive molecular dynamics simulations were performed to investigate the thermal dissociation of THTCPD. The detailed description of THTCPD pyrolysis behavior was obtained from the aspects of initial reactions, main species distributions and intermolecular reactions. Initiation of the THTCPD decomposition is mainly through CC bond fission of the bicycloheptyl structure in the middle, leading to the formation of highly active C15H22 diradicals. To give a better description of the pyrolysis behavior, main products related intermolecular reactions should be considered in the mechanism. The simulated pre-exponential factor A (2.30 × 1015 s−1) and activation energy E (55.72 kcal/mol) captured from simulations are found to be reasonably consistent with the experimental values.