Thermal Memory Effects Research Articles

Non-Fourier computations of heat and mass transport in nanoscale solid-fluid interactions using the Galerkin finite element method

PurposeTo improve the thermal performance of base fluid, nanoparticles of three types are dispersed in the base fluid. A novel theory of non-Fourier heat transfer is used for design and development of models. The thermal performance of sample fluids is compared to determine which types of combination of nanoparticles are the best for an optimized enhancement in thermal performance of fluids. This article aims to: (i) investigate the impact of nanoparticles on thermal performance; and (ii) implement the Galerkin finite element method (GFEM) to thermal problems.Design/methodology/approachThe mathematical models are developed using novel non-Fourier heat flux theory, conservation laws of computational fluid dynamics (CFD) and no-slip thermal boundary conditions. The models are approximated using thermal boundary layer approximations, and transformed models are solved numerically using GFEM. A grid-sensitivity test is performed. The accuracy, correction and stability of solutions is ensured. The numerical method adopted for the calculations is validated with published data. Quantities of engineering interest, i.e. wall shear stress, wall mass flow rate and wall heat flux, are calculated and examined versus emerging rheological parameters and thermal relaxation time.FindingsThe thermal relaxation time measures the ability of a fluid to restore its original thermal state, called thermal equilibrium and therefore, simulations have shown that the thermal relaxation time associated with a mono nanofluid has the most substantial effect on the temperature of fluid, whereas a ternary nanofluid has the smallest thermal relaxation time. A ternary nanofluid has a wider thermal boundary thickness in comparison with base and di- and mono nanofluids. The wall heat flux (in the case of the ternary nanofluids) has the most significant value compared with the wall shear stresses for the mono and hybrid nanofluids. The wall heat and mass fluxes have the highest values for the case of non-Fourier heat and mass diffusion compared to the case of Fourier heat and mass transfer.Originality/valueAn extensive literature review reveals that no study has considered thermal and concentration memory effects on transport mechanisms in fluids of cross-rheological liquid using novel theory of heat and mass [presented by Cattaneo (Cattaneo, 1958) and Christov (Christov, 2009)] so far. Moreover, the finite element method for coupled and nonlinear CFD problems has not been implemented so far. To the best of the authors’ knowledge for the first time, the dynamics of wall heat flow rate and mass flow rate under simultaneous effects of thermal and solute relaxation times, Ohmic dissipation and first-order chemical reactions are studied.

Enhanced thermal cycle stability and shape memory effect in NiTiHf shape memory alloys fabricated by laser powder bed fusion

We report on the fabrication of NiTiHf high temperature shape memory alloys (SMAs) via laser powder bed fusion (LPBF), which are almost free of micro-pores and display (Ti, Hf)2Ni nanoprecipitates with variable size and volume fraction. The effect of variable laser powers of 50 W, 60 W and 70 W on the martensite variant microstructures and mechanical properties of the LPBFed SMAs was investigated. Interestingly, all LPBFed NiTiHf samples display enhanced thermal cycle stability of transformation temperatures with a temperature eviation of −3°C, which is attributed to the lack of dislocation slip originated from the habit plane configuration characteristic with multidomain (001) martensite compound twins. Meanwhile, all LPBFed NiTiHf samples exhibit trained one-way and two-way shape memory effects due to the dislocation slip upon compression deformation at room temperature.

Numerical study on generalized heat and mass transfer in cross-rheological fluid in the presence of multi-nanoscale particles: A Galerkin finite element approach

Thermal and concentration memory effects on the transport of heat and mass subjected to magnetic field and non-uniform free stream velocity are studied in this article. A cross-rheological model is used with governing laws that are solved numerically using the finite element method (FEM). A computer program is developed. The convergent and grid-independent solutions are computed, which are further used to analyse the impact of related parameters on flow fields. Influence of ternary, di-, and mono-nanoparticles on generalized transport of heat and mass in non-Newtonian fluids with cross-rheology. The dynamics of wall shear stress, wall heat, and mass fluxes are studied. Cross-fluid is a non-Newtonian fluid. It has shear rate-dependent viscosity. The behavior of cross-fluid rheology on velocity can be seen through a variation of the cross-fluid parameter called the Weissenberg number, and it has an increasing behavior on velocity. Cross-nanofluid is highly influenced by the magnetic field in comparison with cross-tri-nanofluid and cross-di-nanofluid.

Development of a Self-Regulating Solar Shading Actuator Based on the Thermal Shape Memory Effect

In the field of adaptive building technologies, this research introduces the development of a self-regulating solar shading actuator that utilizes the thermal shape memory effect. The study focuses on addressing the actuator’s performance under diverse environmental conditions. Thermal simulations were carried out during the development of the individual components of the actuator and for the prediction of specific switching temperatures. The investigation includes an analysis of the sunshade’s response to varying environmental conditions, emphasizing its effectiveness on clear summer days and identifying challenges during overcast periods. The critical coordination between the solar collector and the shape memory alloy (SMA) wire is examined, shedding light on the impact of SMA temperature dynamics on the actuation performance. Through the integration of simulation data and real-world measurements, the study validates the thermal model for the solar collector, establishing the robustness of the system’s operation. This research work contributes significantly to the development of intelligent actuators and outlines the importance of validation of SMA-based applications under real conditions.

Memory of incomplete phase transitions from a random squares model.

We present a simple two-dimensional model for a phase transition, then study its predictions, in particular the memory properties. The direct transformation is modeled by randomly placing small squares, "nuclei", on an initially empty surface. Then, the nuclei expand ("grow") up to finite final sizes which are randomly chosen in a given range, while keeping their square shape. An important issue is the "interaction" which forces some squares to remain at smaller sizes if the surrounding squares get in the way of their growth. Interestingly, this naturally leads to quasiequal total area covered by the squares of each size after a complete direct transformation. Next, it is shown that the system "remembers" incomplete ("arrested") reverse transformations taking place in reversed order of the squares sizes. The memory is "encrypted" in the distribution of the squares sizes after a next direct transformation and manifests as a significant imbalance between the areas covered by the "big" and "small" (relative to the arrest size) squares. We are able to also reproduce the so-called "hammer effect" and the memorizing of multiple arrest points. Our model is particularly relevant for the thermal memory effect in shape memory alloys, and we actually borrowed many features from existing thermodynamic models addressing this effect. However, here we eliminate the explicit thermodynamics and end up with a statistical geometry model, presumably easier to reproduce.

Enhancing the thermal stability and recoverability of ZrCu-based shape memory alloys via interstitial doping

ZrCu-based shape memory alloys (SMAs) are regarded as emerging smart materials with high phase transformation temperatures. However, unfavorable thermal stability and poor strain recovery rate hinder commercial applications. Herein, these issues were addressed by doping interstitial B atoms, and the impacts of B content on microstructure, martensitic transformation behavior and properties of ZrCu-based SMAs were systematically investigated. It was shown that (Zr50Cu25Ni7.5Co17.5)99.98B0.02 SMAs possessed excellent thermal stability and shape memory effect. The change of martensitic transformation temperature for this alloy was 15.7 °C after several cycles. The shape recovery rate reached 92.5 % at 8 % compressive pre-strain, which was attributed to the de-twinning of (0 0 1) compound twins and the appearance of (1 1 1) type I twins. Furthermore, it was elucidated for the first time by first-principles calculations that B atoms were covalently bonded with Zr and Cu atoms occupying the octahedral interstitial positions in the B19′ and Cm phases. This study offers an available pathway to exploit efficient and advanced products.

A generalized thermal memory effect of Caputo–Fabrizio fractional integral on natural convection flow of hybrid nanofluid

In this paper, the natural convective flow of hybrid nanofluid over the vertical plate has been examined. Cattaneo law of thermal flux is used to characterize thermal transport. The novel model for fractional constitutive equation is expressed by the time fractional Caputo–Fabrizio integral. The analytical solution of the generalized convective flow of viscous fluid over the vertical plate along generalized conditions is obtained by using the Laplace transform. Mathcad is used to determine numerically the influence of the physical and fractional parameters on the temperature and velocity field to depict the results graphically.

Synthesis of Self-healing and Light-, Thermal-, and Humidity-induced Deformative Polyurethane Actuator.

Intelligent actuating materials have drawn enormous attention because of their potential applications in soft robots, smart sensors, bionics, etc. Aiming to integrate light, thermal, and humidity stimuli deformations and self-healing function into a single polymer, a smart actuating polyurethane material CPPU-50 is designed and successfully synthesized through co-polymerization of azobenzene-containing Azo-C12 , polyethylene glycol 200 (PEG200), and 4,4'-diphenylmethane diisocyanate (MDI) at a ratio of 1:1:2. The obtained polyurethane CPPU-50 exhibits good photoinduced bending, thermal responsive shape memory effect, humidity triggered deflections and self-healing properties. Furthermore, an actuator combining light and thermal stimuli is created and the self-healing CPPU-50 film can withstand the object of 1800 times without tearing. This work can pave a way for further development of long-lived multi-stimuli-responsive actuating devices and intelligent materials.

Colossal Anisotropic Thermal Expansion through Coupling Spin Crossover and Rhombus Deformation in a Hexanuclear {FeIII 4 FeII 2 } Compound.

Colossal and anisotropic thermal expansion is a key function for microscale or nanoscale actuators in material science. Herein, we present a hexanuclear compound of [(Tp*)FeIII (CN)3 ]4 [FeII (Ppmp)]2 ⋅2 CH3 OH (1, Tp*=hydrotris(3,5-dimethyl-pyrazol-1-yl)borate and Ppmp=2-[3-(2'-pyridyl)pyrazol-1-ylmethyl]pyridine), which has a rhombic core structure abbreviated as {FeIII 2 FeII 2 }. Magnetic susceptibility measurements and single-crystal X-ray diffraction analyses revealed that 1 underwent thermally-induced spin transition with the thermal hysteresis. The FeII site in 1 behaved as a spin crossover (SCO) unit, and significant deformation of its octahedron was observed during the spin transition process. Moreover, the distortion of the FeII centers actuated anisotropic deformation of the rhombic {FeIII 2 FeII 2 } core, which was spread over the whole crystal through the subsequent molecular rearrangements, leading to the colossal anisotropic thermal expansion. Our results provide a rational strategy for realizing the colossal anisotropic thermal expansion and shape memory effects by tuning the magnetic bistability.

Colossal Anisotropic Thermal Expansion through Coupling Spin Crossover and Rhombus Deformation in a Hexanuclear {FeIII4FeII2} Compound

AbstractColossal and anisotropic thermal expansion is a key function for microscale or nanoscale actuators in material science. Herein, we present a hexanuclear compound of [(Tp*)FeIII(CN)3]4[FeII(Ppmp)]2⋅2 CH3OH (1, Tp*=hydrotris(3,5‐dimethyl‐pyrazol‐1‐yl)borate and Ppmp=2‐[3‐(2′‐pyridyl)pyrazol‐1‐ylmethyl]pyridine), which has a rhombic core structure abbreviated as {FeIII2FeII2}. Magnetic susceptibility measurements and single‐crystal X‐ray diffraction analyses revealed that 1 underwent thermally‐induced spin transition with the thermal hysteresis. The FeII site in 1 behaved as a spin crossover (SCO) unit, and significant deformation of its octahedron was observed during the spin transition process. Moreover, the distortion of the FeII centers actuated anisotropic deformation of the rhombic {FeIII2FeII2} core, which was spread over the whole crystal through the subsequent molecular rearrangements, leading to the colossal anisotropic thermal expansion. Our results provide a rational strategy for realizing the colossal anisotropic thermal expansion and shape memory effects by tuning the magnetic bistability.

A Polymorph of Dipeptide Halide Glycyl-L-Alanine Hydroiodide Monohydrate: Crystal Structure, Optical Second Harmonic Generation, Piezoelectricity and Pyroelectricity.

A polymorph of glycyl-L-alanine HI.H2O is synthesized from chiral cyclo-glycyl-L-alanine dipeptide. The dipeptide is known to show molecular flexibility in different environments, which leads to polymorphism. The crystal structure of the glycyl-L-alanine HI.H2O polymorph is determined at room temperature and indicates that the space group is polar (P21), with two molecules per unit cell and unit cell parameters a = 7.747 Å, b = 6.435 Å, c = 10.941 Å, α = 90°, β = 107.53(3)°, γ = 90° and V = 520.1(7) Å3. Crystallization in the polar point group 2, with one polar axis parallel to the b axis, allows pyroelectricity and optical second harmonic generation. Thermal melting of the glycyl-L-alanine HI.H2O polymorph starts at 533 K, close to the melting temperature reported for cyclo-glycyl-L-alanine (531 K) and 32 K lower than that reported for linear glycyl-L-alanine dipeptide (563 K), suggesting that although the dipeptide, when crystallized in the polymorphic form, is not anymore in its cyclic form, it keeps a memory of its initial closed chain and therefore shows a thermal memory effect. Here, we report a pyroelectric coefficient as high as 45 µC/m2K occurring at 345 K, one order of magnitude smaller than that of semi-organic ferroelectric triglycine sulphate (TGS) crystal. Moreover, the glycyl-L-alanine HI.H2O polymorph displays a nonlinear optical effective coefficient of 0.14 pm/V, around 14 times smaller than the value from a phase-matched inorganic barium borate (BBO) single crystal. The new polymorph displays an effective piezoelectric coefficient equal to deff=280 pCN-1, when embedded into electrospun polymer fibers, indicating its suitability as an active system for energy harvesting.

Impact of Device Layout on Thermal Parameters and RF Performance of 90-nm SiGe HBTs

The present work investigates the impact of transistor layout on both the RF and thermal performance of 90-nm SiGe heterojunction bipolar transistors (HBTs). The resulting performance shows only slight degradation in small-signal RF figures-of-merit, while large-signal RF figures-of-merit relevant to power amplifiers (PAs) are improved. Thermal resistance and capacitance were extracted for five different SiGe HBT layouts with the same total emitter area. Additionally, a favorable trade-off exists between RF performance figures-of-merit and thermal parameters; namely, the thermal time constant can be reduced by up to 37% with optimal layout, with only slight degradation (up to 8%) in RF performance. These optimal device layout variations can help circuit designers mitigate thermal memory effects at the device level, thereby improving the overall large-signal linearity of PAs.

Behavior of hybrid nanostructure and dust particles in fluid motion with thermal radiation and memory effects

Behavior of hybrid nanostructure and dust particles in fluid motion with thermal radiation and memory effects

Designable Electrical/Thermal Coordinated Dual-Regulation Based on Liquid Metal Shape Memory Polymer Foam for Smart Switch.

Electronic components with tunable resistance, especially with synergistic regulation of thermal conductivity, play important roles in the fields of electronics, smart switch, soft robots, and so on. However, it is still a challenge to get the material with various resistance and thermal conductivity stably without lasting external force. Herein, a liquid metal shape memory polymer foam (LM-SMF) is developed by loading electrically and thermally conductive liquid metal (LM) on deformable foam skeleton. Based on thermal response shape memory effect, the foam skeleton can be reversibly pressed, the process of which enables LM to transfer between connected and disconnected states. As a result, obtained LM-SMF shows that the resistance stably changes from 0.8 Ω (conductor) to 200 MΩ (insulator), and the thermal conductivity difference is up to 4.71 times (0.108 to 0.509W m-1 K-1 ), which indicates that LM-SMF can achieve the electrical and thermal dual-regulation. Moreover, LM-SMF can be used as a designable self-feedback/-warning integrated smart switch or tunable infrared stealth switch. This work proposes a novel strategy to get the material with electrical-thermal coordinated dual-regulation, which is possibly applied in intelligent heating system with real-time monitoring function, electrothermal sensor in the future.

Magnetic Field Influence of Photo-Mechanical-Thermal Waves for Optically Excited Microelongated Semiconductor

A theoretical novel model is investigated that describes the dynamic effects of the microelongation processes of an exciting semiconductor medium. The influence of the magnetic field for the optically excited medium is taken into consideration according to the photothermal transport characteristics. The governing equations were derived during the electronic (ED) and thermoelastic (TED) deformation processes when the microelongation parameters of the semiconductor medium were taken into account. The interference between thermal-magnetic-microelongat-plasma-mechanical waves is investigated. The dimensionless expressions are utilized to solve the main equations according to the harmonic wave technique in two-dimensional (2D) deformation. The complete solutions of the expressions of the physical field were obtained when some conditions were taken on the outer semiconductor surface. The theoretical microelongated semiconductor model in this investigation was checked by comparing it with some previous studies. The numerical simulation for the main physical field distributions is graphically displayed when the silicon (Si) material is used. The impact of various factors such as the magnetic field, thermal memory effect, and microelongation on the wave propagations for main fields was discussed.

Numerical study on thermal and concentration relaxation time in tri, hybrid and mono nano-Sutterby magnetohydrodynamic fluid under generalized diffusion conditions

Sutterby fluid is a viscoelastic fluid and heat and mass transfer in such fluids obeys thermal and concentration memory effects which cannot be analyzed through classical laws of heat conduction and mass diffusion. This is the main motivation toward this study. Therefore, this article considers viscoelastic effects in the presence of thermal and solutal memory effects. A novel theory of heat and mass is simultaneously implemented and generalized models are developed because classical energy and heat equations do not provide accurate information for fluids with memory effect. These generalized models are reducible to their classical cases. Hence, this study considers both generalized and classical aspects. Further, generalized models are solved numerically with the help of the FEM. Results are computed for quantities of engineering interest. The predictions perceived from the analysis are of the use of engineers and industry to design nanofluids with desired thermal properties. A destructive chemical reaction in mono-nanofluid has the highest decreasing effect (relative to tri- and hybrid nanofluids) on the concentration field. A moderate effect of destructive chemical reaction on concentration field in hybrid nanofluid is seen. Mono, hybrid, and tri-nanofluids perceived different magnetic effects. Hybrid nanofluid experiences the greatest magnetic force in comparison with mono and tri-nanofluids. It is seen from the simulations that tri-nanofluid generates the highest heat as a result of Ohmic dissipation. Thus, in comparison with mono and hybrid nanofluid tri-nanofluid offers the highest resistance to the flow of electric current. Moreover, tri-nanoparticles are responsible for an optimized increase in thermal conductivity of Sutterby fluid relative to mono and hybrid nanoparticles. Thus, tri-nanofluid may serve as better coolant, a medium for transporting heat. Destructive chemical reaction in mono-nanofluid has the highest decreasing effect on the concentration field. A moderate effect of destructive chemical reaction on concentration field in hybrid nanofluid is seen. Tri-nanofluid exerts the highest shear stress on the solid boundary while the least shear stress on the wall is seen in the case of mono-nanofluid. A 56% increase in the Nusselt number is noticed if hybrid nanoparticles disperse rather than mono nanoparticles. Similarly, a 59% increase in the Nusselt number is observed if tri-nanoparticles are dispersed rather than mono nanoparticles. Thus the significant rise in heat transfer is possible due to the dispersion of tri-nanoparticles.

Unsteady natural convection flow due to fractional thermal transport and symmetric heat source/sink

Unsteady natural convection flow of viscous fluids in a circular cylinder, due to a generalized fractional thermal transport is analytically studied. The considered mathematical model is based on a new fractional differential constitutive equation of the thermal flux suitable to describe the thermal memory effects. To develop the mathematical model, the time-fractional Caputo-Fabrizio derivative is used. The generalized constitutive equation becomes equivalent to the classical Fourier's law for the zero value of the fractional order of derivative. Analytical solutions for the fluid temperature and velocity are determined using the Laplace and finite Hankel transforms. The influence of the memory parameter on heat transfer and fluid motion is discussed by numerical simulations and graphical illustrations.

Numerical study on thermal efficiencies in mono, hybrid and tri-nano Sutterby fluids

The impact of mono and hybrid nanoparticles on thermal enhancement in the fluid has been much focused on and discussed. However, tri-nanoparticles are considered a little. Therefore, Sutterby fluid is considered as base fluid and thermal improvement in this fluid is via the use of tri-nanoparticles analyzed. The comparative analysis helps to study the improvement in thermal enhancement in such fluids. The finite element approach (FEM) is used for numerical solutions. The quantities of engineering interest are investigated against the parameters. Thermal memory effects in mono nanofluids are stronger than in hybrid and tri-nanofluids. However, thermal memory effects in hybrid nanofluids have moderate values. Momentum diffuses in mono nanofluids faster than that in hybrid and tri-nanofluids. Comparative analysis for the wall shear stress exerted by tri-nanofluid is more than that exerted by mono and hybrid nanofluids. Higher wall heat flux in tri-nanofluids relative to wall heat flux in fluids with CuO and Al2O3 or CuO is noted. Thus, an optimized heat transfer by the tri-nanofluid is noted and tri-nanofluid is recommended for maximum heat transfer.

Shape Memory Alloy-Based Wearables: A Review, and Conceptual Frameworks on HCI and HRI in Industry 4.0.

Ever since its discovery, the applications of Shape Memory Alloys (SMA) can be found across a range of application domains, from structural design to medical technology. This is based upon the unique and inherent characteristics such as thermal Shape Memory Effect (SME) and Superelasticity (or Pseudoelasticity). While thermal SME is used for shape morphing applications wherein temperature change can govern the shape and dimension of the SMA, Superelasticity allows the alloy to withstand a comparatively very high magnitude of loads without undergoing plastic deformation at higher temperatures. These unique properties in wearables have revolutionized the field, and from fabrics to exoskeletons, SMA has found its place in robotics and cobotics. This review article focuses on the most recent research work in the field of SMA-based smart wearables paired with robotic applications for human-robot interaction. The literature is categorized based on SMA property incorporated and on actuator or sensor-based concept. Further, use-cases or conceptual frameworks for SMA fiber in fabric for ‘Smart Jacket’ and SMA springs in the shoe soles for ‘Smart Shoes’ are proposed. The conceptual frameworks are built upon existing technologies; however, their utility in a smart factory concept is emphasized, and algorithms to achieve the same are proposed. The integration of the two concepts with the Industrial Internet of Things (IIoT) is discussed, specifically regarding minimizing hazards for the worker/user in Industry 5.0. The article aims to propel a discussion regarding the multi-faceted applications of SMAs in human-robot interaction and Industry 5.0. Furthermore, the challenges and the limitations of the smart alloy and the technological barriers restricting the growth of SMA applications in the field of smart wearables are observed and elaborated.

Dual stimulus response mechanical properties tunable biodegradable and biocompatible PLCL/PPDO based shape memory composites

The aliphatic polyester poly(L-lactide-co-ε-caprolactone)(PLCL) was synthesized successfully in this research. And a temperature-responsive and water-responsive shape memory composite was prepared by the physical blend of PLCL and poly (p-dioxanone) (PPDO) for the first time. The thermal properties, crystallinity, microstructure, mechanical properties, shape memory behavior, and degradation properties of PLCL/PPDO composites were comprehensively investigated. The results showed that the mechanical properties of the composite could be adjusted with the addition ratio of PPDO. All materials possessed excellent shape memory fixation rates: close to 100%. PPDO improved the shape memory recovery ratio of PLCL without affecting the shape memory fixation ratio of PLCL. PL/PP82 showed the best shape memory recovery ratio at 37°C with 91.34 ± 3.56%. A combination of in situ wide-angle X-ray scattering and tensile modes was used to elucidate the unique mechanism of shape memory in the air for this range of composites. PL/PP82 also exhibited excellent thermal and water-induced shape memory effects in water at 37 °C, with a rapid return to the original state of the composite within 19 s. The introduction of PPDO improved the degradation rate of the composite and regulated the rate of degradation. Additionally, the addition of PPDO significantly enhanced the hydrophilicity of the composites, which promoted proliferative adhesion of osteoblasts to the composite surface. Thus, the temperature and water responsive shape memory composites had great potential in bone tissue engineering applications.