Axial Conduction Research Articles

Anisotropic Heat Transfer in a Fibrous Membrane with Hierarchically Assembled 2D Materials.

Effective heat redistribution in specific directions is vital for advanced thermal management, significantly enhancing device performance by optimizing spatial heat configurations. We have designed and fabricated a hierarchical fibrous membrane that enables precise heat directing. By integrating hierarchical structure design with the anisotropic thermal conductivity of two-dimensional (2D) materials, we developed a fibrous membrane for anisotropic heat transfer. Such a structure is fabricated by aligning a 1D structured fiber in the 2D plane to achieve anisotropy at each scale level. The fiber units, where 2D nanosheets circumferentially and axially aligned, achieved a high axial thermal conductivity of 16.8 W·m-1·K-1 and advanced heat directing ability, confirmed by characterizations and simulations. The assembled membrane demonstrated an exceptional tensile strength (365 MPa) and high thermal conductivity (10.5 W·m-1·K-1) along the fiber axis. Our membranes are seen as a refined model for thermal management materials, combining the benefits of heat spreaders and thermal interface materials, thus being proficient in directing heat along programmed pathways. A practical wireless charging cooling demonstration illustrated this. Our methodology also proved versatile with different 2D fillers and various geometries. This research presents a method to achieve precise heat directing at the material's level, facilitating the systematic design of thermal management in electronics.

Advancing thermohydraulic performance of micro-grooved flat heat pipes through a combined numerical-experimental approach

A combined numerical-experimental model has been developed to predict the thermohydraulic characteristics of micro-grooved flat heat pipes (FHPs). This model uses a limited number of experimental data for calibration with two parameters, βexp,1 and βexp,2, which account for uncertainties in the accommodation coefficients used to determine evaporation and condensation mass fluxes. This calibration, which is a key feature of the developed model, addresses the uncertainties and challenges in determining these coefficients. Moreover, the model incorporates the effects of interfacial shear stress, axial wall conduction, heat transfer in the liquid block region, and the contact angle of the liquid–vapor interface. Furthermore, the evaporation mass flux from the curved liquid–vapor interface is calculated using a separate multiscale approach developed in two recent works for analyzing evaporation from the extended meniscus in microchannels, considering thin-film evaporation. The model demonstrates high accuracy in predicting the maximum heat transport capacity (Qmax) and wall temperature distribution across various input heat powers, with a maximum error of less than 0.5 % in wall temperature predictions, as validated against experimental data. The validated model is then used to explore a new micro-grooved wick structure featuring converging/diverging microchannels. In this structure, the channel width is constant and equal to Wf2 in the first half of the heat pipe, from the condenser end to the midpoint, and then it decreases or increases to Wf1 by the end of the evaporator section. Results indicate that a flat heat pipe with a converging micro-grooved wick structure (Wf1 = 200 µm and Wf2 = 160 µm) can enhance Qmax from 53 to 70 W, 70.8 to 91.8 W, and 91.2 to 116.5 W at working temperatures of 60 °C, 70 °C, and 80 °C, respectively. This means the new converging micro-grooved wick structure can boost flat heat pipe performance by more than 25 % compared to a flat heat pipe with a straight micro-grooved wick (Wf1 = Wf2 = 200 µm) without increasing the occupied space.

Performance analysis of a low-pressure cryogenic vaporizer for liquified hydrogen supply system

In this paper, we theoretically investigated the thermal performance of a low-pressure cryogenic vaporizer for liquified hydrogen supply system. A performance analysis model was developed by the modified effectiveness-NTU method considering the axial conduction and phase change of liquified hydrogen. In the analysis model, a plate-fin heat exchanger (PFHE) was chosen as the type of a cryogenic vaporizer. The inlet temperature and pressure conditions of liquified hydrogen were 20 K and 10 bar, respectively and the outlet temperature condition of hydrogen was a room temperature. Based on the theoretical results, we presented effects of geometric parameters on the performance of the vaporizer under the fixed pumping power condition. Especially, it is shown that the effectiveness of the hot fluid and cold fluid exhibit opposite trends depending on the axial conduction. In addition, we presented the effect of the aspect ratio of microchannels on the effectiveness considering both cases where the microchannel heights of the EGW mixture and hydrogen were either the same or different. Also, we showed the effect of the vaporizer length on the performance of the vaporizer. Finally, geometric parameters that can satisfy the two target performances are suggested.

Experiment and simulation study on transfer phenomena and performance optimization of MgH2 based hydrogen storage reactors

This paper investigated the heat transfer phenomenon and enhancement mechanism in MgH2 based hydrogen storage reactors, aiming to optimize the heat and mass transfer resistance and reaction kinetics issues encountered in practical applications of the hydrogen storage materials. The powdered MgH2 hydrogen storage material and its compacted disks were prepared to study the thermophysical properties and hydrogen absorption/desorption characteristics. For the disk prepared by composite 5 wt% EG under a compression pressure of 100 MPa, its axial and radial thermal conductivity can be as high as 2.53 and 2.03 W/(m·K), respectively, and the average hydrogen absorption rate within 1000 s is 17.2% faster than that of the powder material when applied in reactors. To gain a better understanding of the influence of the material properties, and operating conditions on the heat transfer and reaction performance inside the reactor, mathematical models for the heat and mass transfer and reaction processes of the reactor were established. Simulation results revealed the coupling mechanism of heat transfer and reaction within the storage reactor, and showed that the increased thermal conductivity and hydrogen absorption pressure can further accelerate absorption process. When the thermal conductivity increases from 2 to 10 W/(m·K) and the absorption pressure increases from 1 to 1.8 MPa, the average hydrogen absorption rate can increase by 79.4% and 42.2%, respectively.

Frequency-domain axisymmetric and thermomechanical viscoelastic analysis of thermoplastic composite pipe

ABSTRACT Thermoplastic composite pipe (TCP), composed of polymers and composite laminates, shows significant potential for deep-water offshore oil field development due to its lightweight and high strength. However, current mechanical studies primarily focus on the elastic domain, ignoring the critical viscoelasticity of non-metallic materials. To solve this, we introduce a comprehensive theoretical model that incorporates viscoelastic properties under both axisymmetric and thermal loads, considering radial convective thermal gradients and axial heat conduction. This model accurately predicts TCP's mechanical behavior by using stiffness coefficients, differential geometry, and radial-axial temperature transfer curves. By applying the principle of elastic-viscoelastic correspondence, we obtain viscoelastic solutions in the frequency domain, showing strong agreement with Finite Element (FE) models particularly under cyclic loading. Viscoelasticity introduces larger equivalent axial stiffness and viscoelastic damping within complex structures, which become more obvious with temperature fluctuations.

Hierarchical Incorporation of Reduced Graphene Oxide into Anisotropic Cellulose Nanofiber Foams Improves Their Thermal Insulation.

Anisotropic cellulose nanofiber (CNF) foams represent the state-of-the-art in renewable insulation. These foams consist of large (diameter >10 μm) uniaxially aligned macropores with mesoporous pore-walls and aligned CNF. The foams show anisotropic thermal conduction, where heat transports more efficiently in the axial direction (along the aligned CNF and macropores) than in the radial direction (perpendicular to the aligned CNF and macropores). Here we explore the impact on axial and radial thermal conductivity upon depositing a thin film of reduced graphene oxide (rGO) on the macropore walls in anisotropic CNF foams. To obtain rGO films on the foam walls we developed liquid-phase self-assembly to deposit rGO in a layer-by-layer fashion. Using electron and ion microscopy, we thoroughly characterized the resulting rGO-CNF foams and confirmed the successful deposition of rGO. These hierarchical rGO-CNF foams show lower radial thermal conductivity (λr) across a wide range of relative humidity compared to CNF control foams. Our work therefore demonstrates a potential method for improved thermal insulation in anisotropic CNF foams and introduces versatile self-assembly for postmodification of such foams.

Carbon Nanotube-Based Catalyst Modification to Improve Proton Exchange Membrane Fuel Cell Interlayer Interactions

Proton exchange membrane fuel cells (PEMFC) were identified as a highly viable solution for addressing climate-related issues. Previous theoretical investigations have underscored the significance of Pt nanoparticles as the optimal metal for hydrogen fuel cell catalysts due to their special activity and selectivity. [1] Current works focused on the utilisation, durability, and site activity of Pt particles on support, and most of the schemes achieved performance enhancement by loading Pt onto porous support with different morphology such as graphene, carbon fibre, and carbon black. [2] Some schemes have also incorporated cost considerations to achieve lower Pt loading. [3] However, the design of the catalyst layer (CL) structure in the membrane electrode assembly (MEA) must consider the interactions between the layers.Addressing the crucial aspects of water management, low contact resistance, and the establishment of effective three-phase boundary for MEA, multi-walled carbon nanotubes (MWCNTs) are a promising CL support due to their intrinsically high hydrophobicity, high axial electrical conductivity, and potential for ordered alignment. [4] However, the drawbacks of MWCNTs such as strong agglomeration, wall surface chemical inertness, and unopened ends are unfavourable for Pt nanoparticle loading, which is detrimental to MEA processing and leads to inhomogeneous CL surfaces. This further deteriorates the utilisation of Pt and increases the contact resistance. Previous efforts have explored methods such as introduction of polar functional groups on MWCNT using strong reflux oxidation condition, or nitrogen doping to construct localised pyridine structure. [5, 6] However, over-functionalisation can cause MWCNT to lose its favourable structure and properties.In this work, MWCNT was modified based on the operational requirements of the MEA from the viewpoint of interlayer interactions, including the search for the optimal degree of oxidation, N-doping, and micro-arrangement. MWCNT were functionalise by oxidising, N-doping, as well as micro-alignment to achieve lower contact resistance between CL and proton exchange membrane (PEM), better hydrophobicity, and enhanced performance. Furthermore, this work expects to construct a more continuously distributed three-phase boundary by aligning MWCNT to form a locally ordered structure, which is essential for the efficient utilisation of Pt active sites.Preliminary experiments in this work have tested a range of reflux oxidation conditions for MWCNT treated with concentrated nitric acid ranging from 0 to 10 h. The maximum power density of 979.81 mw cm-2 was achieved by Pt loading on 6h MWCNT oxidation time (Pt-MWCNT 6h). This represented a 59.53% improvement over the commercial Pt/C catalyst of 614.17 (mw cm-2) (Figure 1 (a)). In addition, due to the stronger electrical conductivity, the charge transfer resistance of Pt-MWCNT6h in the electrochemical impedance spectroscopy (EIS) test was 0.09 Ohm cm-2, which was 48.86% lower than that of Pt/C (Figure 1 (b)). This study will discuss the developed catalysts and their efficacy in a working fuel cell system.In conclusion, this research proposed alternative perspectives on the design of the CL based on the actual operational characteristics of MEA with emphasised on the interlayer interaction between CL and other layer. Additionally, the research will validate the impact of low-functionalization modification of MWCNTs on the performance of PEMFC, which simplifying the preparation challenges of CL and contributing for the widespread commercial application of PEMFCs on a larger scale. References Seh, Z.W., et al., Combining theory and experiment in electrocatalysis: Insights into materials design. Science, 2017. 355(6321): p. eaad4998.Sui, S., et al., A comprehensive review of Pt electrocatalysts for the oxygen reduction reaction: Nanostructure, activity, mechanism and carbon support in PEM fuel cells. Journal of Materials Chemistry A, 2017. 5(5): p. 1808-1825.Tian, Z.Q., et al., A Highly Order-Structured Membrane Electrode Assembly with Vertically Aligned Carbon Nanotubes for Ultra-Low Pt Loading PEM Fuel Cells. Advanced Energy Materials, 2011. 1(6): p. 1205-1214.Lehman, J.H., et al., Evaluating the characteristics of multiwall carbon nanotubes. Carbon, 2011. 49(8): p. 2581-2602.Hernández-Fernández, P., et al., Functionalization of multi-walled carbon nanotubes and application as supports for electrocatalysts in proton-exchange membrane fuel cell. Applied Catalysis B: Environmental, 2010. 99(1): p. 343-352.Gribov, E.N., et al., Effect of modification of multi-walled carbon nanotubes with nitrogen-containing polymers on the electrochemical performance of Pt/CNT catalysts in PEMFC. Materials for Renewable and Sustainable Energy, 2019. 8(1): p. 7. Figure 1

Modeling and mathematical analysis of root water uptake in the rhizosphere

ABSTRACT This research focuses on elucidating a system of partial differential equations designed to model the process of water uptake by a single root within an unsaturated soil. This model extends a unidimensional root scenario by incorporating radial and axial hydraulic conductance in the root structure. The flow dynamics in the rhizosphere are represented by the Richards equation, while a diffusion equation is employed to characterize water movement within the root. The resulting system forms a strongly coupled, nonlinear parabolic-elliptic system. To establish the existence and uniqueness of a solution, we utilize the technique of semi-discretization and the Schauder-Tychonoff fixed point theorem. Additionally, we approximate the system using a mixed finite element method, and the subsequent numerical tests presented align well with the model predictions. This comprehensive approach contributes to our understanding of the intricate dynamics involved in root water uptake and provides a robust framework for further exploration in this field.

Hydrophobic and thermal insulation properties of modified wood based on ATRP polymerisation

Balsa wood, despite being a cost-effective insulation material, has limited applications due to its inherent hydrophilicity. This study introduces an innovative technique for the in-situ growth of low surface energy long alkyl chain segments on balsa wood using the atom transfer radical polymerization (ARGET-ATRP) method, which not only provides durable and stable hydrophobicity but also preserves its natural texture, mechanical strength, and thermal insulation. The resulting hydrophobic wood demonstrated exceptional hydrophobicity in diverse environments, with a water contact angle up to 141.3° and a contact angle decrease of no more than 10.47 % after 150 min, confirming its hydrophobic stability. Furthermore, axial thermal conductivity of the wood was as low as 0.1012 W/m·K, the axial compressive strength decreased by only 12.8 %, further evidencing the retention of its mechanical properties. This simple yet effective strategy of in-situ alkyl chain growth on balsa wood not only preserves its structure but also opens new avenues for the multifunctional development of biomaterials.

Beyond Mechanical Protection: The Electron-Shielding Effect of SWCNT for the Stabilized SiO Interface.

The single-walled carbon nanotube (SWCNT) commonly serves as a conductive additive for SiO-based anode materials due to the excellent conductivity and mechanical properties. However, the potential action mechanisms for the SWCNT beyond conductivity and mechanical features have rarely been studied. Herein, an interfacial electron-shielding effect and preferential adsorption to the electrolyte components for the SWCNT are revealed through a series of advanced characterizations and density functional theory (DFT) simulations. It can be determined that SWCNT networks could restrict the transmission of the electron from SiO interface to electrolyte with the reduced decomposition, because of the typical axial conductivity of the SWCNT. Moreover, the SWCNT shows stronger adsorption energy for LiPF6 and ethylene carbonate (EC) molecules, rather than nonselectivity of traditional carbon additives, facilitating the generation of inorganic-rich and denser solid electrolyte interface (SEI) film. As a result, benefiting from the electron-shielding effect, preferential adsorption, and mechanical protection, the SWCNT endows the SiO@C anode with a higher average Coulombic efficiency (CE) value of 99.4% over 100 cycles and a long cycling stability.

Correction: Numerical analysis of Carreau fluid inside a horizontal passage with axial conduction and viscous dissipation: an extended Graetz problem

Correction: Numerical analysis of Carreau fluid inside a horizontal passage with axial conduction and viscous dissipation: an extended Graetz problem

Integrating the complex rheological Carreau model with the Graetz-Brinkman problem in a horizontal passage

ABSTRACT The current investigation emphasizes the influence of viscous dissipation in laminar forced convection internal flow for horizontal conduit using the non-Newtonian fluid. A Carreau fluid model is taken into account. The hydrodynamically developed velocity profile is obtained by employing a perturbation approach. A classical Graetz approach is utilized to achieve the solution of the developed energy equation while the MATLAB built-in command bvp4c is taken into account for the solution of the Eigenvalue problem. The negligible axial conduction and uniform physical characteristics are presumed. The influence of the viscous dissipation and model parameters on non-dimensional bulk temperature and Nusselt number is deliberated for both cooling and heating situations. The current analysis is valid for small values of Weissenberg number We ≤ 1 . The findings reveal that viscous dissipation has a significant impact on temperature distribution in both developing and fully established regions.

Micromechanical modeling of thermal conductivities of unidirectional carbon fiber/epoxy composites containing carbon nanotube/graphene hybrids

This article deals with the micromechanical modeling of thermal conductivities of the unidirectional carbon fiber (CF)-reinforced composites with carbon nanotube (CNT)/graphene nanoplatelet (GNP)-enriched epoxy matrix. The thermal conductivity of epoxy-based nanocompounds enriched through the incorporation of CNT/GNP hybrids is estimated within the framework of micromechanics. The significant contribution of several microstructures, including the volume fraction, dimension, and straightness of nanofillers, thermal resistance at the interface of the nanofillers and epoxy matrix, and the percolation effect on the nanocomposite thermal conductivity is considered. Furthermore, the method of cells (MOC) is used to anticipate the axial and transverse thermal conductances of unidirectional composites featuring CFs integrated into the CNT/GNP-enriched polymer nanocomposite matrix. The results reveal that incorporating a combination of GNTs and CNTs into the polymer matrix significantly increases the transverse thermal conduction of the multiphase compound. Several factors contribute to improved thermal conductance of the transverse direction in CF/CNT/GNP composites: (i) higher nanofiller concentration, (ii) presence of straight nanofillers, and (iii) use of larger nanofillers. The predictions of micromechanical modeling give good agreement with available experiments. This study compares the transverse and axial thermal conductivity of unidirectional compounds predicted by MOC method with results obtained using the finite element method.

Numerical analysis of Carreau fluid inside a horizontal passage with axial conduction and viscous dissipation: an extended Graetz problem

Numerical analysis of Carreau fluid inside a horizontal passage with axial conduction and viscous dissipation: an extended Graetz problem

Orbit-attitude-structure-thermal coupled modelling method for large space structures in unified meshes

Large space structures would exhibit orbit-attitude-structure-thermal coupled effects in complicated space environment. Thus, a new thermal-structure coupled modelling method is proposed using gradient-deficient absolute nodal coordinate formulation beam elements. Compared to the previous methods, both axial and circumferential heat conduction are considered. The cubic interpolation in temperature field instead of the linear interpolation is adopted to obtain a unified-mesh temperature-displacement description. The gravitational force and gravity gradient are modelled, and the effects of attitude motion and structural deformation on solar radiation intensity are considered. In addition, three kinds of quasi-static thermal-structure coupled models are proposed based on Euler-Bernoulli beam theory. Based on the quasi-static models, the theoretical formulas are derived to effectively predict the thermally induced vibrations of the beam in space. Four numerical examples are studied to validate the proposed models, including the heat conduction examples with three boundary conditions and a thermal-structure coupled cantilever beam example. Based on the proposed formulation, the orbit-attitude-structure-thermal coupled dynamics of a multibody system consisted of a rigid body and a large flexible appendage is investigated considering the gravity gradient, solar radiation, Earth's shadow, and self-shadow.

Investigating the synergy of blockage ratio and external cold heat exchanger in standing-wave thermoacoustic engines: An experimental study

Thermoacoustic engines (TAE) offer a promising avenue for converting low-grade heat into useable energy. Despite its simplicity in fabrication, designing thermoacoustic engines face efficiency challenges hindering their widespread adoption. One key obstacle faced by current thermoacoustic devices is their lack of efficiency. The core components of TAE are the stack, Cold Heat Exchanger (CHX), Hot Heat Exchanger (CHX) and the resonator. These components are crucial in advancing the performance of thermoacoustic engines. The CHX keeps the working gas cool, which is essential for the engine to function efficiently and create the desired acoustic wave. However, many existing efforts in this field have not taken into consideration the effect of the CHX design which may have effect on the operating temperature and the engines performance. This study examines the influence of different CHX blockage ratios (28 %, 36 %, 42 %, 47 %, and 59 %), along with the addition of an external CHX, on performance metrics. Measurements were conducted using air at room temperature and atmospheric pressure to assess temperature difference, startup time, volumetric velocity, and sound pressure levels. Key findings indicate that Efficiency directly correlates with volumetric velocity and inversely with onset temperature. Even though decreasing the blockage ratio increases operating temperature, it lengthens startup and reduces volumetric velocity, suggesting increased axial conduction. In addition, External CHX lowers operating temperature, reducing volumetric velocity and sound pressure. Interestingly, resonance frequency remains unaffected by CHX blockage ratio changes. An optimal configuration with a 42–47 % blockage ratio achieves 5.92 m/s velocity, 136 s startup time, and 77 °C onset temperature. These findings offer valuable insights for optimizing thermoacoustic engine efficiency and advancing their potential as sustainable energy solutions.

Highly thermally conductive composites of graphene fibers

Carbon fiber-based polymer composites have rich electric and thermal functions, the merit of weight lightness to meet important applications in thermal management. Graphene fiber, a newly emerged carbonaceous fiber, features high thermal conductivity that surpasses conventional carbon fibers. For the realistic applications of graphene fiber, fiber composite is one necessary form but still remains unexplored. Here, we prepared graphene fiber based polymer composites and achieved high specific thermal conductivity up to 363 W∙cm3∙m−1∙K−1∙g−1, outperforming composites of mesophase pitch-based carbon fiber. Graphene fiber composites with a fiber content of 59 vol% have a low density of 1.53 g∙cm−3 and high axial thermal conductivity of 553 W∙m−1∙K−1. For the high breakage elongation of graphene fiber, graphene fiber composites can be fabricated to adapt sharp curvature structures. This work develops polymer composites of graphene fiber and their high thermal conductivity can have extensive applications in thermal management.

An overview of conjugate heat transfer augmentation methods for thermal management and recent advancements in microchannel heat sink overall performance

Recent technological advancement creates high-dense circuits development which creates colossal cooling demand requirements. In the future, advanced technology and scientific applications need to balance heat fluxes beyond limitation that catalyse the research opportunities further to achieve cooling requirements. Conventional cooling equipment is inappropriate for extracting heat from microchips within the minimal surface area. Microchannel technology appeared as a next-generation heat exchanger for the given heat duty. In the classical case of accounting, micro-heat exchangers both axial and transverse wall conduction effects is usually neglected. However, from the year 2005 onwards, researchers identified conduction dominance at fluid velocity is zero zones at the interface, which created balance between conduction–convection currents, finally included axial wall/heat conduction effects to a general model. This present study made a comparative evaluation fluid flow, heat transfer characteristics, thermal performance (TP) based on geometrical parameters, substrate materials and discusses previous issues, and current issues-based future research directions. Till today, based on applications of microchannels in thermal management, several experimental and numerical investigations have been reported for further improvement in TP. However, many researchers are still trying to accomplish things over a long period. Therefore, an overview of previous studies is furnished in the present study to assist researchers in this area much useful for further improvement.

Flame-retardant wire burning behavior by jet flame heating: Ignition, charring, and secondary flame spread

This research presents an in-depth examination of the combustion characteristics of flame-retardant electrical wires, contrasting behavior with non-flame-retardant counterparts under jet flame heating. The study systematically investigates the pyrolysis process, ignition patterns, charring behavior, and the development of secondary flames in wires with different core diameters and insulation materials. Findings indicate the heightened susceptibility of thinner wires to rapid heating, pyrolysis and charring, leading to faster ignition and more intense secondary flame development. This insight is crucial for tailoring flame-retardant formulations to specific wire dimensions. The research also delves into the thermal dynamics within the wires, highlighting how the core diameter influences axial heat conduction and, consequently, the overall flame spread behavior and pyrolysis rate. A critical discovery is the relationship between heating duration and flame sustainability, establishing a specific range of heating times for sustaining secondary flames in flame-retardant wires. Theoretical models used in the study explained the critical heat flux heating time for wire ignition, offering insights into improved fire prevention strategies, particularly in prolonged heat exposure scenarios. These findings not only advance our understanding of flame-retardant wire behavior under fire conditions but also provide guidance for selecting and using electrical wires, thereby optimizing fire safety in diverse applications.

Examining the potential of sigma-thermic heat transfer fluid and its nanofluid in a natural circulation loop through CFD studies

This study investigates the impact of hot heat exchanger (HHX) inlet temperature on Sigma-thermic heat transfer fluid (STHF or STF) performance in a natural circulation loop. Various fluids, including STHF and STHF-based nanofluids, with volumetric concentrations ranging from 0.5% to 3%, are employed in the loop. The primary objective is to analyze the thermal performance of the loop under different conditions, focusing on temperature distribution, Nusselt number, friction factor, effectiveness, and mass flow rate. 3D numerical simulations are conducted, and the numerical model is validated against existing literature. The developed model incorporates considerations for viscous dissipation and axial conduction to predict the heat transfer potential of the loop. As the HHX inlet temperature increases, the mass flow rate rises. Notably, STHF/CuO nanofluids exhibit a more substantial enhancement than other nanofluids. At a 1 vol% concentration, the mass flow rate increases by 9.5%, 4%, and 2.7% for STHF/CuO, STHF/Al2O3, and hybrid nanofluids, respectively, compared to pure STHF. The study reveals significant improvements in mass flow rates and heat transfer efficiency with increasing HHX inlet temperatures, especially with STHF/CuO nanofluids. The total entropy generation reduction is notable, with percentages ranging from 2% to 18.5% for various nanofluids compared to pure STHF.