Thermal Conductivity Research Articles

Investigation of the Theoretical Model of Nano-Coolant Thermal Conductivity Suitable for Proton Exchange Membrane Fuel Cells

The fuel cell vehicle is one of the essential directions for developing new energy vehicles. But heat dissipation is a critical technical difficulty that needs to be solved urgently. Nano-coolant is a promising coolant that can potentially replace the existing coolant of a fuel cell. However, its thermal conductivity has a significant impact on heat dissipation performance, which is closely related to nanoparticles’ thermal conductivity, nanoparticles’ volume fraction, and the nano-coolant temperature. Many scholars have created the thermal conductivity models for nano-coolants to explore the mechanism of nano-coolants’ thermal conductivity. At present, there is no unified opinion on the mechanism of the micro thermal conductivity of the nano-coolant. Hence, this paper proposed a novel model to predict the thermal conductivity of ethylene glycol/deionized water-based nano-coolants. A corrected model was designed based on the Hamilton & Crosser model and nanolayer theory. Finally, a new theoretical model of nano-coolant thermal conductivity suitable for fuel cell vehicles was constructed based on the base fluid’s experimental data.

Hybrid Geopolymer Composites Based on Fly Ash Reinforced with Glass and Flax Fibers

This article’s aim is to analyze physical, mechanical, and fracture properties as well as the thermal investigation of geopolymer composites reinforced with flax, glass fiber, and also the hybrid combination of fibers. Two types of matrices were considered as composites matrices. The first composition was based on fly ash and river sand. The second matrix composition contained fly ash and glass spheres. The content of reinforcement was 1% by mass. Compressive strength and three-point bending fracture tests were performed. The values of fracture toughness and fracture energy were determined. The resonance method was used to verify the dynamic characteristics, such as the dynamic modulus of elasticity and the dynamic Poisson ratio. The results show that single-type fibers in composites based on fly ash and glass spheres did not affect compressive strength. However, introducing hybrid reinforcement increased compressive strength by about 10% compared to the reference specimens. Flax fibers and hybrid reinforcement ensured higher fracture toughness and energy. The results also revealed great potential for glass sphere application to geopolymer materials in terms of fracture mechanics and thermal properties. Despite the lower strength properties in relation to geopolymers based on sand aggregate, applying reinforced fibers into the composite with glass spheres enhanced the compressive strength compared to other materials. Materials modified with glass spheres have a thermal conductivity twice as low as that of materials containing river sand.

Exploring nanoparticle dynamics in binary chemical reactions within magnetized porous media: a computational analysis

Artificial Neural Networks are incredibly efficient at handling complicated and nonlinear mathematical problems, making them very useful for tackling these challenges. Artificial neural networks offer a special computational architecture that is extremely valuable in disciplines like biotechnology, biological computing, and computational fluid dynamics. The present work investigates the applicability of back-propagation artificial neural networks in conjunction with the Levenberg-Marquardt algorithm for evaluating heat transmission in hybrid nanofluids. This work focuses on the computational analysis of a MgO + GO/EG hybrid nanofluid’s steady mixed convection flow over an exponentially stretched sheet, considering multiple slip boundary conditions, thermal conductivity, heat generation, and thermal radiation. A nonlinear system of ordinary differential equations is produced from the basic associated partial differential system by performing the proper exponential similarities modifications. For generating benchmark datasets, the resulting ordinary differential equations are processed employing the bvp4c method. Considering benchmark datasets set aside for training (70%), testing (15%), and validation (15%), the Levenberg-Marquardt algorithm, which employs back-propagation in artificial neural networks, is implemented. The accuracy of the suggested strategy for handling nonlinear problems is verified utilizing mean squared error, error histograms, and regression analysis, which are all used to evaluate the methodology. Outstanding agreement is seen when ANN outputs are compared to numerical results. The flow properties, including temperature, velocity, and concentration profiles, are shown graphically and numerically. For practical purposes, it is therefore essential to analyze the flow and heat transfer in hybrid nanofluids over exponentially extending and shrinking surfaces under mixed convection and heat source scenarios. Hybrid nanofluid problems have a wide range of practical and industrial applications, such as medication delivery, manufacturing, microelectronics, nuclear plant cooling, and marine engineering.

A novel ultra-light bio-based fiberboard from mexican feather grass for thermal and acoustic insulation in green building construction applications

The use of natural fibers as raw materials for insulation fiberboard production is emerging as a strategy to replace wood fibers. This study developed an ultralightweight natural fiber insulation core fiberboard (CFB) with high mechanical strength, hygroscopic resistance, and excellent acoustic and thermal insulation properties. This study examined the production of CFB, which utilizes Mexican feather grass fibers with an epoxy resin binder across a range of densities of 0.18–0.36 g∙cm−3. Furthermore, the impact of incorporating a reinforcing skin layer of woven glass fibers on the core fiberboard's physical, mechanical, acoustic, and thermal properties was evaluated. All the fiberboard samples exhibited excellent thermal conductivity values (0.048–0.057 W/mK), which increased with increasing panel density (0.18–0.36 g∙cm−3). In addition, all of them displayed superior mechanical properties following the ASTM C208 standard. In terms of climatic resistance of the fiberboards, the results displayed excellent water resistance, exhibiting minimal humidity content (<5 %), thickness swelling (<6.5 %), and a hydrophobic surface, as indicated by the high-water contact angle (>121.96 at 30 s). Sound reduction exhibited a frequency-dependent tendency, with denser and sandwich fiberboards showing greater sound reduction of up to 27.9–36.56 dB at 3150 Hz for CFB-0.36 and SFB-0.52, respectively. Following ASTM C208, both core fiberboards and those coated with woven glass fiber skins (sandwich fiberboards, SFB) met the thermomechanical property requirements for regular and structural wall sheathing applications, respectively. These findings highlight the potential of Mexican feather grass as a bio-based alternative to wood, enabling the production of eco-friendly ultralightweight fiberboards with excellent thermomechanical properties suitable for building construction, such as regular and structural wall sheathing applications and ceiling decorations.

A facile method for carbon nanotube/carbon fiber‐reinforced polylactic acid composites

AbstractThe mechanical strength of polylactic acid (PLA) can be improved by carbon fiber (CF) compositing to expand its application in tissue engineering scaffolds. However, the mechanical strength of CF‐reinforced polylactic acid (CFRPLA) composites is compromised due to weak interfacial interaction resulting from the chemically inert surface of CF. In the article, carbon nanotube (CNT) with poly(diallyldimethylammonium chloride) (PDDA) as a coupling agent was covered on CF to improve the chemical activity and roughness of the surface of CF, and then the as‐prepared CF‐PCNT were further incorporated into PLA via melt compounding. The yield strength, modulus, and thermal conductivity of PLA/CF‐PCNT were 14.09%, 7.65%, and 5.24% higher than those of PLA/CF, respectively, and the volume resistivity was 99.74% lower at a 10 wt% loading. The enhancement for the mechanical properties of PLA/CF‐PCNT composites could be ascribed to the mechanical locking, hydrogen bonds and covalent bonds between CF and matrix through the interface modulation of CNT and PDDA. This facile and non‐destructive method offers a novel strategy for the modification of CF fillers.Highlights CF was modified by PDDA and CNT through a facile and non‐destructive method. The active functional groups and roughness on the surface of CF were increased. The surfaces of CFs were characterized by FT‐IR, Raman spectra, XPS and SEM. The interface was improved by mechanical locking, covalent, and hydrogen bonds. The mechanical strength, electrical and thermal conductivity of composites were improved.

Multifunctional green synthesized silver nanoparticle and polypyrrole-based e-textile for wearable thermoregulation applications

Electronic textiles (e-textiles) build upon existing technologies to develop truly smart textiles: garments that sense, react, and adapt. Thermoregulatory e-textiles are an area of significant interest across the field. Designing e-textiles that satisfy electrical performance and simple construction is a significant challenge. To address these issues, a simple dip-coating and in-situ polymerization method was used to develop the first example of a thermoregulatory e-textile using green synthesized silver nanoparticles (AgNP) and polypyrrole (Ppy), based on the method previously reported (Naysmith, A.; Mian, N.S.; Rana, S. Development of conductive textile fabric using Plackett–Burman optimized green synthesized silver nanoparticles and in situ polymerized polypyrrole. Green Chemistry Letters and Reviews 2023, 16 (1)). This methodology was optimized using a Taguchi statistical design determining the optimal AgNP-Ppy synthesis method to obtain high performance Joule heating e-textiles, novel within the field of e-textiles. Reactant concentration and reaction time had the largest effects on the electrical resistance of subsequent e-textiles. The result is the first example of an e-textile heater based on green synthesized AgNPs. The e-textile demonstrated exceptional Joule heating (120°C), low electrical resistance (37 Ω), resistive temperature sensing behavior (negative TCR = −0.0046), and increased thermal conductivity (19.55 l (Wm−1 K−1)); the strain sensing behavior (gauge factor = −0.07). This work extends knowledge of the development and challenges within e-textile technologies as the field creates the next generation of textiles.

Effect of particle size distribution on the thermal conductivity of crushed GMZ bentonite pellet mixtures

Effect of particle size distribution on the thermal conductivity of crushed GMZ bentonite pellet mixtures

Inclusion of 2D nanosheets on ZnSb matrix as a unique approach to improve its thermoelectric performance

Enhancing the thermoelectric performance has been made possible by the strategy of introducing an additional phase to the thermoelectric (TE) material. ZnSb: MoS2 nanocomposites are successfully prepared using the solid-state method and sintering. Structural and morphology analysis confirms the inclusion of MoS2 in the ZnSb matrix. The phonon scattering is greatly improved in nanocomposites with newly designed ZnSb: MoS2 interfaces without impairing electron transport. Homogeneous dispersion of MoS2 nanosheets in the ZnSb matrix modulates the carrier effective mass, which is aided by a considerably greater interfacial barrier. The energy filtering effect leads to a significantly higher Seebeck coefficient with strongly reduced phonon conductivity. The addition of MoS2 nanosheets improves the TE power factor (PF) of ZnSb over the temperature of 300 K–673 K. For the ZnSb: MoS2 nanocomposite with 10 wt% of MoS2 achieves a maximum PF of 419.67 μW/mK2 at 673 K, a value that is much greater than pristine ZnSb. It has been shown that zT can be significantly improved by enhancing power factor values and reducing thermal conductivity. A high value of 0.65 is achieved at 673 K for ZnSb:15 % MoS2, which is higher than that for pristine ZnSb. This study lays the path for enhancing the thermoelectric efficiency of p-type ZnSb using interfacial additive of 2D MoS2 nanosheets.

Simultaneously Enhanced Thermal Conductivity and Dielectric Breakdown Strength in Micro/Nano-BN/Epoxy/PC Multilayer Composites

Simultaneously Enhanced Thermal Conductivity and Dielectric Breakdown Strength in Micro/Nano-BN/Epoxy/PC Multilayer Composites

Transferable Percolated Particle Monolayers Derived from Marangoni Flows for Thermally Conductive Dielectric Coatings.

Thermal management is becoming one of the most significant design and size limitations for high power density electronics, including motherboards, power converters, and phased array antennas for 5G communications. There are few options for conducting heat away with dielectric materials that avoid shortening or distorting the performance of these electronics. Certain highly thermally conductive 2D and 3D materials, including hexagonal boron nitride and diamond, offer ideal material properties to address these issues but are extremely challenging to process. This work studies highly oriented single-particle thick films of hexagonal boron nitride, manufactured through a modified Langmuir-Blodgett process and densified further using the Marangoni effect to attain remarkable thermal conductivity enhancement with minimal coating thickness. High loadings of hexagonal boron nitride (∼60 vol %) in dense, castable films are also produced to compare thermal spreading ability in a comparatively simpler but less-coordinated percolated system to the highly percolated particle monolayers. These procedures were applied to glass fiber reinforced polymers used in aerospace and radome applications as well as to a single-board computer to demonstrate enhanced thermal management.

Ultralow thermal conductivity in Si–Ge nanograin mixtures: A cost-effective granular material for thermoelectric applications

This paper presents a theoretical study of the thermal conductivity of Si–Ge nanograin mixtures using a multiscale computational methodology based on solving the Boltzmann transport equation for phonons with first-principles techniques. A size-dependent correction factor is developed to account for the spatial dependence of the phonon distribution function on nanograin size, with parameters derived from the phonon properties of infinite Si and Ge crystals. This approach makes it possible to accurately calculate the thermal conductivity within a single nanograin, using force constants obtained from first-principles calculations. Thermal energy transport by phonons across grain boundaries is modeled by accounting for phonon transmission by two-phonon processes, weighting specular, and diffuse transmission for each phonon mode as a function of the root-mean-square roughness of the boundary relative to the phonon wavelength. The boundary thermal conductance model, previously validated against experimental data, is implemented using first-principles techniques. This approach excludes specular transmission for phonon modes with specific symmetries while ensuring conservation of the total number of modes in each symmetry class. The study examines the influence of grain size, nanograin mixture composition, temperature, and boundary asperities on the thermal conductivity of nanograin mixtures.

Free‐Standing, Multifunctional Thermoelectric and Acoustic Absorbing Nanocomposite Foams

AbstractThermoelectric materials are potential energy harvesting technologies that enable direct, clean conversion between thermal and electrical energy. The efficacy of thermoelectric energy conversion is influenced by the electrical conductivity, thermal conductivity, and Seebeck coefficient. Flexibility, manufacturability, and cost‐effectiveness are also important factors. Polymeric nanocomposites offer advantages in these respects. However, the development of conductive‐polymer thermoelectric materials is limited to an in‐plane architecture, which does not resemble common real‐world scenarios. Moreover, existing works have low thermoelectric properties or rely on additives for performance improvement. In this work, a free‐standing thermoelectric nanocomposite foam is fabricated via the integration of thermally activated microspheres. Due to the microstructure, a thermal conductivity as low as 0.03 W m−1 K−1 is achieved, which is lower than reported for aerogels fabricated via freeze‐drying methods. Additionally, the nanocomposite foam can reach a maximum electrical conductivity of 1.13 S cm−1, power factor of 0.12 µW m−1 K−2, and thermoelectric figure of merit of 3.0 × 10−4. The study also evaluated the compressive stiffness and demonstrated the potential for sound absorption. With the unique combination of the thermoelectric, sound absorption, and mechanical behavior, these nanocomposite foams would offer versatile solutions to address the next generation energy harvesting and acoustic absorption applications.

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.

Assessing the Impact of Shredded Polyethylene Terephthalate (PET) Post-Consumer Plastic as a Partial Replacement for Coarse Aggregates in Unreinforced Concrete

This study investigates the feasibility of incorporating shredded polyethylene terephthalate (PET) post-consumer plastic waste as a partial replacement for coarse aggregates in unreinforced concrete such as masonry blocks. Standard concrete blocks were produced with varying PET content (0%, 5%, 25%, 35%, 50%) and tested for workability, air content, density, compressive strength, flexural strength, and thermal conductivity. Results indicated that replacing up to 25% of traditional aggregates with PET maintains adequate compressive strength for non-load-bearing applications and enhances thermal insulation by reducing the thermal conductivity from 0.7 W/m·°K to 0.27 W/m·°K at 25% replacement level, representing a significant improvement of approximately 61%. Higher PET content (35–50%) resulted in reduced structural integrity but improved insulation, suggesting its suitability for non-structural applications. This research highlights the potential of using PET plastic waste in unreinforced concrete, promoting sustainable construction practices by reducing plastic waste and conserving natural resources.

Enhanced Laser Damage Threshold in Optically Addressable Light Valves via Aluminum Nitride Photoconductors

AbstractOptically addressable light valves (OALVs) are specialized optical components utilized for spatial beam shaping in various laser‐based applications, including optics damage mitigation, and enhanced functionality in diode‐based additive manufacturing requiring high intensities. Current state‐of‐the‐art OALVs employ photoconductors such as Bismuth Silicon Oxide (BSO) or Bismuth Germanium Oxide (BGO), which suffer from limited laser‐induced damage thresholds (LiDT) and inadequate thermal conductivities, thus restricting their use in high peak and average power applications. Aluminum nitride (AlN), an emerging ultra‐wide band gap (UWBG) III–V semiconductor, offers promising optoelectronic properties and superior thermal conductivity (&gt;300 Wm−1K−1 at 298° K, compared to BSO's 3.29 Wm−1K−1). In this study, the first AlN‐based OALVs are designed, fabricated, and experimentally demonstrated using commercially available single‐crystal AlN substrates. These AlN‐based OALVs have shown clear superiority over BSO and BGO‐based devices. Design considerations for OALVs incorporating UWBG photoconductors are discussed, and the photoresponsivity from defect‐mediated sub‐bandgap absorption in AlN crystals is verified as sufficient for OALVs operating under high light fluences. The optimum driving voltage for the AlN‐based OALV is determined to be ≈ 45 Vpp at 100 Hz, achieving a transmittance of 91.3%, an extinction ratio (ER) of more than 100, and a 51:1 image contrast.

New Eco-Friendly Thermal Insulation and Sound Absorption Composite Materials Derived from Waste Black Tea Bags and Date Palm Tree Surface Fibers

A tremendous amount of waste black tea bags (BTBs) and date palm surface fibers (DPSFs), at the end of their life cycle, end up in landfills, leading to increased pollution and an increase in the negative impact on the environment. Therefore, this study aims to utilize these normally wasted materials efficiently by developing new composite materials for thermal insulation and sound absorption. Five insulation composite boards were developed, two were bound (BTB or DPSF with polyvinyl Acetate resin (PVA)) and three were hybrids (BTB, DPSF, and resin). In addition, the loose raw waste materials (BTB and DPSF) were tested separately with no binder. Thermal conductivity and sound absorption coefficients were determined for all boards. Thermal stability analysis was reported for the components of the tea bag (string, label, and bag) and one of the composite hybrid boards. Mechanical properties of the boards such as flexural strain, flexural stress, and flexural elastic modulus were determined for the bound and hybrid composites. The results showed that the thermal conductivity coefficients for all the hybrid composite sample boards are less than 0.07 at the ambient temperature of 24 °C and they were enhanced as the BTB ratio was reduced in the hybrid composite boards. The noise reduction coefficient for bound and all hybrid composite samples is greater than 0.37. The composite samples are thermally stable up to 291 °C. Most composite samples have a high flexure modulus between 4.3 MPa and 10.5 MPa. The tea bag raw materials and the composite samples have a low moisture content below 2.25%. These output results seem promising and encouraging using such developed sample boards as eco-friendly thermal insulation and sound absorption and competing with the synthetic ones developed from petrochemicals in building insulation. Moreover, returning these waste materials to circulation and producing new eco-friendly composites can reduce the number of landfills, the level of environmental pollution, and the use of synthetic materials made from fossil resources.

Study on enhancing mechanical and thermal properties of carbon fiber reinforced epoxy composite through zinc oxide nanofiller

This study investigates the enhancement of mechanical and thermal properties of carbon fiber reinforced epoxy composites by incorporating zinc oxide (ZnO) nanofillers. The composites were developed by adding 3–15 g of ZnO nanoparticles into the epoxy matrix and were evaluated through experimental testing. The results showed significant improvements in mechanical performance, with the maximum tensile strength of 112.49 MPa and flexural strength of 114.82 MPa at the 15 g ZnO concentration. SEM analysis revealed a reduction in void content and improved fiber-matrix adhesion, enhancing load transfer. Thermal conductivity is 13.47 W/mK, while the coefficient of linear thermal expansion is 9.29 × 10−5/°C, indicating superior thermal stability. TGA analysis demonstrated a shift in decomposition temperature from 310 to 375 °C, confirming enhanced thermal stability. These results highlight the positive influence of ZnO nanofillers on both the mechanical and thermal properties of carbon fiber reinforced epoxy composites, making them more suitable for advanced structural applications.

Reproducible Superinsulation Materials: Organosilica-Based Hybrid Aerogels with Flexibility Control

In this study, we report highly crosslinked hybrid aerogels with an organic backbone based on vinylmethyldimethoxysilane (VMDMS) with tuneable properties. For an improved and highly reproducible synthesis, a prepolymer based on 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (D4V4) and VMDMS as monomers was prepared and purified. Di-tert-butylperoxide (DTBP) concentrations of 1 mol% initiate the radical polymerization of the mentioned monomers to achieve high yields of polymers. After purification, the obtained viscous polyorganosilane precursor could be reproducibly crosslinked with dimethyldimethoxysilane (DMDMS) or methyltrimethoxysilane (MTMS) to form gels in benzylic alcohol (BzOH), water (H2O) and tetramethylammonium hydroxide (TMAOH). Whereas freeze-drying these silica-based hybrid aerogels led to high thermal conductivity (&gt;20 mW m−1K−1) and very fragile materials, useful aerogels were obtained via solvent exchange and supercritical drying with CO2. The DMDMS-based aerogels exhibit enhanced compressibility (31% at 7 kPa) and low thermal conductivity (16.5 mW m−1K−1) with densities around (0.111 g cm−3). The use of MTMS results in aerogels with lower compressibility (21% at 7 kPa) and higher density (0.124 g cm−3) but excellent insulating properties (14.8 mW m−1K−1).

The Regulation of Temperature Fluctuations and Energy Consumption in Buildings Using Phase Change Material–Gypsum Boards in Summer

This study examined the thermal performance of Comfortboard23, a commercial gypsum board from Knauf infused with phase change material (PCM). Structural characterization using XRD and SEM confirmed the presence of microencapsulated PCM within the gypsum matrix. The study does not provide a direct comparison between Comfortboard23 and other PCM-integrated gypsum boards on the market. This is a limitation of the research. A comprehensive comparison would involve testing multiple products under identical conditions, and evaluating factors such as thermal performance, cost-effectiveness, durability, and ease of installation. Thermal characterization involved a novel low-scale thermal chamber to measure U-value, thermal conductivity, heat storage capacity, and dynamic thermal response. Results showed incorporating PCM decreased the U-value by 2% compared to standard gypsum boards. Additionally, PCM inclusion increased heat storage capacity by around 45% and improved dynamic thermal characteristics by decreasing thermal stability coefficient from 0.92 to 0.76 and increasing thermal lag from 0.27 to 0.49 h. The 45% increase in heat storage capacity of Comfortboard23 could lead to a 10–20% reduction in heating and cooling energy consumption, improved thermal comfort, and potential HVAC downsizing. Exact benefits depend on climate, building design, and occupancy patterns, necessitating further research in diverse real-world settings. The findings demonstrate Comfortboard23’s potential for enhancing thermal energy storage in buildings, contributing to energy savings, improved thermal comfort, and reduced temperature fluctuations across varying daily temperatures. Overall, the study highlights the promise of Comfortboard23 as an energy-efficient PCM-integrated building material.

The Role of Two Models of Thermal Radiation and Variable Properties on Thermal Explosion Critical and Transition Conditions of the Optically Thin Droplets

ABSTRACT Determining the criticality and disappearance of optically thin droplets (gas phase) by thermal explosions is crucial for maintaining thermal stability in various industrial and nonindustrial applications. The governing nonlinear ordinary differential equations of this problem make use of two distinct approximation models for thermal radiation loss, which were completed by Cogley et al. and Sohrab et al. Two methods of solving the problem – the Semenov method and the inflection point method – are used to identify the circumstances of criticality and disappearance of criticality (transition conditions). The governing equations utilize the use of the temperature-dependent Arrhenius frequency factor of the reaction and the thermal conductivity of the gas. The analytical solution of the equations yields the transitional values of the distinctive parameters at various initial conditions. Numerical methods are used to determine the equation’s exact solution. At specific initial conditions, the impact of θo, θa, γSh,F, and αSh,F on the temperature-time histories of ignition (supercritical region), non-ignition (subcritical region), and the critical boundary between them is derived. Notable effects on the ignition, non-ignition, and critical temperatures and times include the changing frequency of the reaction, the gas thermal conductivity, and two approximation models of radiation heat loss. The two radiation heat loss approximation models of the analytical and numerical findings are compared.