Variation Of Specific Heat Research Articles

Turbulent pipe flow and heat transfer of a binary mixture at supercritical pressure: Influences of cross-diffusion effects

Cross-diffusion effects, including Soret and Dufour effects, are enhanced around the pseudo-critical temperature (Tpc) of a binary mixture. Their influences on heat transfer at supercritical pressure have been scarcely studied. To bridge this gap, large-eddy simulations (LES) are conducted to investigate forced convective heat transfer of a CO2–ethane mixture at supercritical pressures in a circular pipe subject to a uniform heat flux. Both heating and cooling conditions, along with varying initial concentrations and thermodynamic pressures, are included in the simulations. The LES results reveal that the Soret effect causes concentration separation, resulting in a concentration boundary layer. The magnitudes of the thermodiffusion factor (kT) and the radial temperature gradient control the intensity of separation, which is more pronounced at near-critical pressure and high heat flux. Since kT is significant only around Tpc, downstream decay of the concentration separation is observed as the loci of T=Tpc migrate away from the wall so that the local radial temperature gradient diminishes. The primary factors affecting heat transfer are the variations in thermal conductivity and isobaric specific heat resulting from concentration separation. In contrast, the Dufour effect and the accompanying inter-diffusion play negligible roles. In deterioration scenarios, the bulk Nusselt number (Nub) shows a maximum relative drop of 8%, whereas in enhancement scenarios, Nub shows a maximum relative increase in 10%, with both deterioration and enhancement decaying downstream. Cross-diffusion effects have negligible impacts on density and streamwise velocity, but noticeably alter streamwise velocity fluctuation and turbulent kinetic energy.

Thermophysical Characterization of Materials for Energy-Efficient Double Diaphragm Preforming

The Double Diaphragm Preforming (DDPF) process uses vacuum pressure and heat to pre-shape dry carbon fabric reinforcements between flexible diaphragms in liquid composite molding (LCM). Accurate modeling of heat transfer within DDPF requires knowledge of the thermophysical properties of the constituent materials under processing conditions. This study investigates the thermal conductivity of silicone diaphragms and carbon fabrics with embedded thermoplastic binder webs, utilizing transient plane source (TPS) and modified transient plane source (MTPS) methods, respectively. Additionally, the specific heat of silicone, carbon fibers (both chopped and powdered), and binder were measured using differential scanning calorimetry (DSC). Mixed samples comprising chopped fibers with 1.8 wt% binder and powdered fibers with 3.6 wt% binder was also analyzed with DSC. This study also examined the influence of reheating cycles on the specific heat of carbon fiber—3.6 wt% binder samples—and the effect of compaction and vacuum on the thermal conductivity of carbon fabrics with an embedded binder. While silicone exhibited linear-specific heat behavior, the thermoplastic binder showed non-linearity due to phase change. The combined carbon fiber-binder samples demonstrated slight non-linear specific heat variations depending on reheating cycles. The thermal conductivity of the fabric preforms decreased with the addition of thermoplastic binder and under vacuum-compaction conditions. The established temperature-dependent specific heat relationships and thermal conductivity provide valuable data for optimizing DDPF preforming parameters and enhancing energy efficiency in composite manufacturing.

Lattice dynamical and elastic properties of fluoride structure PbF2, CdF2 and their mixed superionic conductors PbxCd1-xF2

Elastic and lattice dynamical properties of fluoride structure PbF2, CdF2 and their mixed superionic conductors PbxCd1-xF2 have been calculated through a twelve parameter three-body shell model. The calculated elastic constants and the related properties, phonon density of states, phonon dispersion relations, variation of lattice specific heat with the absolute temperature are in good agreement with the available theoretical and experimental data. The obtained results of calculated elastic constants for the studied compounds PbF2, CdF2 and their mixed compound PbxCd1-xF2 are mechanically stable. The results of the elastic constants suggest that the above compounds are less compressible along the principle axis than their face and body diagonal. The results for bulk, shear and Young's modulus decreases as CdF2 → PbxCd1-xF2→ PbF2. The Pugh's ratio for the above compounds shows ductile behavior.

Enhancement of an air conditioning system performance utilizing a PCM-based heat exchanger: Impact of aspect ratio

This research emphasizes enhancing air conditioning (AC) system performance through the integration of a phase change material (PCM)-based annulus heat exchanger (HEX) within the condenser unit. The present study delves into how aspect ratio (AR), inlet velocities, and inlet air temperature impact the coefficient of performance (COP) and melting rate. Moreover, it considers the variable specific heat of the PCM, a less-explored aspect in AC-integrated PCM systems. Results have revealed that the AR notably affects the complete melting time. Specifically, an increase in the AR from 15 to 21 has led to a noteworthy reduction of 30.07% in the total melting time under fixed velocity conditions at 2.55 m/sec and θ = 0.429. The present study has also established a correlation to demonstrate how total melting time is influenced by AR, inlet air temperature, and inlet velocity. Also, modifying AR and inlet velocity to the HEX could lead to lower outlet temperatures from the HEX. Initially, at a given velocity of 2.55 m/sec and θ of 0.429, increasing the AR from 15 to 18 leads to a 1.61% decrease in the outlet air temperature from the HEX, while increasing AR from 15 to 21 results in a 3.12% decrement. PCM-enhanced AC systems consistently exhibit improved COP values, especially in low-velocity scenarios, outperforming systems without PCM. At the onset of melting, for a given velocity of 2.55 m/sec and θ of 0.429, the percentage increase in the COP for the altered system compared to a system without the PCM is found to be 11.28%, 12.84%, and 14.01% for ARs of 15, 18, and 21, respectively. Configurations with higher ARs are found to be more suitable for higher cooling loads with shorter working periods.

Effects of rotation and temperature‐dependent viscosity on thermal convection in Oldroydian fluid saturating porous media: A modified stability analysis

AbstractThe onset of thermal convection in an incompressible Oldroydian fluid‐saturating porous media is examined to study the combined impact of uniform rotation and temperature‐dependent viscosity. A characteristic equation from the basic hydrodynamic equations governing the Brinkman–Oldroyd model is derived using linear stability theory and modified Boussinesq approximation. For various combinations of stress‐free and slip‐free boundaries, the expressions for the Darcy–Rayleigh numbers for both non‐oscillatory as well as oscillatory convection with linear and exponential temperature‐dependent viscosity are derived, using the “weighted residual method.” The effects of rotation, variable viscosity parameter, strain retardation and stress relaxation time parameters and other fluid parameters on non‐oscillatory and oscillatory convection are investigated numerically and the results are presented graphically. From the analysis, it is found that overstability is the preferred mode of onset of convection. The rotation, the coefficient of specific heat variations (due to temperature variation), and the strain retardation time have a stabilizing influence on the stability of the system, whereas the stress relaxation imparts a destabilizing effect. Additionally, it is noticed that the variable viscosity parameter and Brinkman‐Darcy number stabilize the system for each set of boundary conditions.

Elevated temperature properties of foam concrete: Experimental study, numerical simulation, and theoretical analysis

Foam concrete, as an inorganic cellular material possessing exceptional thermal insulation and fire resistance properties, emerges as a promising candidate for thermal insulation. To achieve a more precise evaluation of its performance under elevated temperatures, the present study comprehensively investigates the thermal characteristics of foam concrete with a combined experimental, numerical, and theoretical approach. Firstly, a high-temperature test is conducted to investigate the influence of temperature and foam concrete density on its macroscopic appearance and internal temperature distribution. Meanwhile, the thermal conductivity of foam concrete at various densities and temperatures is directly measured with a thermal conductivity analyzer. Subsequently, to acquire comprehensive specific heat and thermal conductivity parameters of foam concrete, with a numerical model established within ABAQUS, the genetic algorithm is applied to identify these thermal parameters based on the measurement data from the elevated temperature test. In addition, CT scanning and 3D reconstruction of foam concrete before and after exposure to elevated temperatures are utilized to extract pore characteristics. This facilitates the thermal conductivity calculation using theoretical models, enabling the determination of the thermal conductivity of foam concrete above 600 °C. Through a comparison of the experimental, numerical, and theoretical results, it is recommended to consider the variation of specific heat in three dehydration stages due to the observed notable dehydration. Due to the effect of cracks, the numerically determined thermal conductivity is slightly higher compared to the experimentally and theoretically determined thermal conductivity. Based on the analysis, an improved formula predicting the specific heat of foam concrete, and a formula determining the thermal conductivity of foam concrete subjected to elevated temperature are proposed.

Flow and heat transfer analysis of laminar flow in hypersonic aircraft with variable specific heat capacity at small attack angles

Purpose As to different angles of attack and nonlinear problems caused by high temperatures in coexisting hypersonic aircraft, people mainly rely on fluid software for research but lack analysis of flow mechanisms. Owing to computational difficulties, few people use numerical algorithms to combine them for discussion. Hence, this study aims to make a deep inquiry into the laminar flow and heat transfer of compressible Newtonian fluid in hypersonic aircraft with small attack angles. Design/methodology/approach In this paper, on the basis of mass, momentum and energy conservation laws, the governing equations of the hypersonic boundary layer are established. Viscosity, specific heat capacity and thermal conductivity are considered nonlinear functions concerning temperature. In virtue of the MacCormack finite difference method, the stationary numerical solutions are solved directly, and the validity of the algorithm is verified. Findings The results demonstrate that at Mach number 5, compared to the 0° attack angle, the maximum temperature near-wall at the 3° attack angle increases by about 25%. An enjoyable phenomenon is discovered, where the position corresponding to the maximum wall shear force shifts back as the attack angle and Mach number increase. The relationship between the near-wall maximum temperature versus attack angle and Mach number is fitted through numerical calculation results. Originality/value Empirical formulas can be used to estimate heat transfer characteristics at small attack angles, which will guide the design of aircraft thermal protection systems.

Experimental measurement and modeling of lattice thermal expansion and specific heat capacity of C15-Cr2Nb Laves phase intermetallic compound

In order to determine the lattice thermal expansion and specific heat capacity (Cp) of the C15-Cr2Nb Laves phase, an experimental investigation and modeling were carried out in the present paper by employing high-temperature X-ray diffraction (HTXRD) and differential scanning calorimetry (DSC). A thorough analytical model was utilized to predict the temperature-dependent variations of enthalpy and specific heat, and the predicted findings were compared to the experimentally measured data. Arc melting was employed to synthesize Cr2Nb samples with distinct hexagonal (C14/C36) and cubic (C15) Laves phase structures, which were then subjected to the appropriate heat treatment. Room temperature XRD patterns, SEM, and EDAX experiments on homogenized samples at 1273 K for 72 h validated the homogeneity and C15 (Fd-3 m) crystal structure of Cr2Nb. Rietveld refinement was used to determine the lattice parameters and relative phase fractions of the constituent phases. The average thermal expansion coefficient was determined to be αai = 0.659 × 10−5 and αVi = 1.977 × 10−5 K−1 respectively. The Cp of the C15-Cr2Nb Laves phase intermetallic compound was measured employing heat flux DSC, utilizing conventional “three-step” procedures, and being reported for the first time. The measured Cp and enthalpy increment data (HT – H298.15) with varying temperatures reported in the present investigation are being correlated utilizing the theoretical model applying the quasi-harmonic Debye Grüneisen model in the temperature range 0–860 K and illustrated different contributions to the total heat capacity i.e., vibrational, anharmonic, and electronic.

Determination of one unknown coefficient in a two-phase free boundary problem in an angular domain with variable thermal conductivity and specific heat

Two different two-phase free boundary Stefan problems in an angular domain with temperature-dependent thermal coefficients are considered. Analytical similarity solutions are obtained imposing a Dirichlet or Neumann type boundary condition, respectively, by solving functional problems. Moreover, formulas are obtained for the determination of one unknown thermal coefficient in the overspecified problem that consists in adding a Neumann condition to the problem with a Dirichlet one if and only if some restrictions on data are verified.

NUMERICAL SIMULATIONS OF THE INFLUENCE OF VARIOUS PARAMETERS ON HEAT TRANSFER AND FLOW SEPARATION IN SUPERSONIC COOLED NOZZLES

In rocket engine nozzle design, flow separation is essential and, given the high temperatures and pressures in the thrust chamber, regenerative cooling is critical for maintaining the nozzle wall's integrity. This passage provides a summary of an in-depth numerical analysis of boundary layer separation and heat transfer within a 30°-15° cooled nozzle. The performance of the SST-V turbulence model under these conditions is assessed numerically. A variety of factors are investigated, including wall temperature, turbulent Prandtl number, and constant specific heat ratios (spanning 1.31 to 1.4 for constant fluid properties of N2O, CH4, Cl2, and air). Furthermore, variable specific heat ratios (from 1.39 to 1.66 for variable fluid properties of air, CH4, O2, and Helium) are examined, along with other parameters that affect the location of separated flow and the local wall heat transfer.

Off Design Performance Analysis of a Turbo Shaft Engine

The off-design performance of a gas turbine engine is strongly influenced by the characteristics of individual components. It involves the interplay of a large number of variables and would require a detailed computer code. In this paper, an effort is made to predict the influence of performance characteristics of individual components on the off-design performance of the engine. For this purpose, a computer code is developed with necessary iterations and convergence criteria. Parameters are estimated with respect to speeds ranging from 39500 rpm to 50500 rpm for a typical turbo-shaft engine with free power turbine. The effect of altitude on these parameters up to 6 km is also studied. Variation of specific heat and enthalpy with respect to temperature and fuel to air ratio is considered to estimate the performance calculations more accurately and to simulate a real engine behavior as close as possible.

Experimental insights into thermal performance of a microtube precooler with drastic coolant properties variation and precooling impacts on turbojet engine operation

In theory, the operating Mach number of a turbojet engine could be broadened by using supercritical coolant precoolers. However, the thermal performance of microtube precoolers is drastically influenced by the variations of coolant properties, which may further affect the engine operation. In order to obtain the heat transfer characteristics and outlet temperature distortion of such precoolers, and to clarify the precooling impacts on turbojet engine thrust performance, an annular precooler with a tube diameter of 0.9 mm was designed and fabricated in this study. Besides, a comprehensive test platform for the precooler-turbojet engine coupling experiments was also built. On this basis, different Mach number simulating experiments were performed using supercritical cryogenic nitrogen as the coolant. For data reduction, a precooler segmented model was proposed to consider the effects of specific heat variation. The results indicate that the developed model is highly recommended for supercritical coolant precoolers operating with relatively high effectiveness. The operating Mach number of the turbojet engine was extended to Ma = 3.35 and the total thrust increased by 39.8% as the precooler outlet temperature decreased from 305.4 K to 248.6 K. Although there exists a temperature non-uniformity at the precooler outlet, it was confirmed to cause no damage to the turbojet engine operation during the experiments. Finally, a new Nusselt number correlation for the supercritical coolant heat transfer was developed based on the experimental data. The results of the present study verify the feasibility of using a supercritical coolant precooler to broaden the operating Mach number of turbojet engines and contribute to the preliminary thermal design of such precoolers.

Effect of discrete inclined ribs on flow and heat transfer of supercritical R134a in a horizontal tube

In this work, discrete double inclined ribs (DDIR) are introduced into the horizontal flow of supercritical R134a to improve the thermal performance of vapor generators in the trans-critical Organic Ranke Cycle. Effects of operating and geometric parameters are investigated after model validation against experimental data. Results show that DDIR are adaptable to changes in operating conditions because spiral flow maintains the dominant position of forced convection heat transfer. DDIR enhance the PEC of horizontal ST by at least 70% and reduce circumferential thermal non-uniformity by up to 90%. Rib pitch has the most significant effect on heat transfer, followed by rib height and inclination angle. The optimal values for the three geometric parameters are 20 mm, 0.8 mm, and 60°. Finally, the mechanism of rib-induced enhancement is analyzed. Average heat transfer is improved by the strengthened mixing between bulk and near-wall fluid instead of suppressing the buoyancy effect. DDIR-induced enhancement is superior to subcritical cases owing to the integral effect of sharp variations in specific heat at supercritical conditions.

Numerical Simulation of Heat Transfer Characteristics of Petroleum Hydrocarbon-Contaminated Soil During Ex-Situ Indirect Thermal Desorption

ABSTRACT Indirect thermal desorption process of petroleum hydrocarbon contaminated soil is very complex and difficult to be analyzed by engineering full-scale numerical simulation considering multi-phase flow and interphase heat as well as mass transfer. Therefore, it is urgent to develop a simple and rapid calculation method to guide technology development and engineering applications. In this paper, the method of equivalent specific heat approximation was proposed to simplify the mass transfer process on the material side to the heat transfer process under variable specific heat conditions, and the numerical simulation of engineering scale indirect thermal desorption equipment was studied by coupling the diffusion flame combustion model, weighted-sum-of-gray-gases model, and discrete ordinates model. The heating process of soil in thermal desorption chamber was simulated, and the influence of soil residence time and designed feed rate on process parameters was obtained. The research results showed that soil residence time should be extended appropriately under the condition of less than 1.75 hours and designed feed rate be limited within 4 t/h to ensure reasonable soil discharge temperature that was directly related to the removal efficiency of petroleum hydrocarbons in contaminated soil. Meanwhile, the modification scheme of power distribution of combustion system was further studied to improve the heating uniformity of tubes.

Compensation temperature and hysteresis behaviors of a graphene-like bilayer: Monte Carlo Study

Using the Monte Carlo method, the compensation temperature and hysteresis loops of a ferrimagnetic mixed spin-3/2 and spin-5/2 Ising-type graphene-like bilayer are investigated induced by different physical parameters such as crystal field, exchange coupling, external magnetic field, and temperature. The variations of magnetization, magnetic susceptibility, specific heat, and internal energy with the change of temperature are discussed. In addition, we also plot the phase diagrams including transition temperature and compensation temperature. Finally, multiple hysteresis loops under certain parameters are given.

Early-Hydration heat and influencing factor analysis of Large-Volume concrete box girder based on equivalent age

Large-volume concrete box girders are vulnerable to early cracking because of the hydration reaction at early ages. The excessive temperature difference between the core and external surface is the main reason for early cracking. Controlling the temperature field of concrete can reduce the risk of early cracking. Therefore, numerical simulations and tracking tests of a 50-m box girder were conducted. The early-age temperature field was simulated using ABAQUS and the secondary development of the subroutine. Meanwhile, the influences of different construction and curing method parameters were analyzed. The subroutine UMATHT considers the variations of hydration degree, thermal conductivity, and specific heat with equivalent age. The results indicate that the early-age hydration temperature of the box girder follows a general trend of “increasing temperature — continuous high temperature — cooling.” The measured results verify the accuracy of the numerical simulation method. The temperature peak and temperature difference between the core and surface increased with the increase in concrete section size, pouring temperature, and cement dosage. The effects of pouring temperature and cement dosage on the temperature rise and cooling rate were reversed. For every 5 °C decrease in the pouring temperature, the temperature peak of the web also decreased by approximately 5 °C, while the temperature difference between the core and surface of the web decreased by approximately 2 °C. When thermal insulation measures were taken for the box girder's outer formwork, the concrete temperature peak increased slightly, but the temperature difference between the core and surface decreased significantly. When the thickness of the polystyrene foam board reached 1 cm, the temperature difference between the core and web surface could be controlled within 6.1 °C.

The Comparison of Fixed and Variable Specific Heat Parameters Based on ANSYS-CFX

At present, in the aerodynamic simulation calculation of turbocharger using ANSYS-CFX, we usually use a fixed constant for the gas performance parameters (including specific heat and thermal conductivity, etc.).In the whole calculation and analysis process, the selection of this constant value is defined according to the inlet temperature. This study found an appropriate, easy to operate and usable way to make the gas performance parameters in the calculation process change with different temperatures in different areas. In the calculation process, Ansys did call the temperature of different locations to calculate the specific heat value. In this study, we also checked the use of non-constant air performance parameters compared to the traditional fixed value on the turbocharger vortex end performance, the impact mainly includes flow, efficiency, and temperature.

STREAmS-2.0: Supersonic turbulent accelerated Navier-Stokes solver version 2.0

We present STREAmS-2.0, an updated version of the flow solver STREAmS, first introduced in Bernardini et al. (2021) [1]. STREAmS-2.0 has an object-oriented design which separates the physics equations from the specific back-end, making the code more suitable for future expansions, such as porting to novel computing architectures or implementation of additional flow physics. Similarly to the previous version, STREAmS-2.0 supports NVIDIA-GPU and CPU back-ends. Additionally, this version features improvements of the input/output data management, new energy and entropy preserving schemes for the discretization of the convective fluxes, recycling/rescaling inflow boundary condition, and a model for thermally perfect gases with variable specific heats. New version program summaryProgram Title: STREAmSCPC Library link to program files:https://doi.org/10.17632/hdcgjpzr3y.2Developer's repository link:https://github.com/STREAmS-CFD/STREAmS-2Licensing provisions: GPLv3Programming language: Fortran, CUDAJournal reference of previous version: M. Bernardini, D. Modesti, F. Salvadore, and S. Pirozzoli. STREAmS: a high-fidelity accelerated solver for direct numerical simulation of compressible turbulent flows. Comput. Phys. Commun. 263 (2021) 107906.Does the new version supersede the previous version?: Yes.Reasons for the new version: New code structure and release of new features.Summary of revisions:•The original solver [1] has been rewritten following an object-oriented design implemented through Fortran derived types that include variables and type bound procedures. The new software architecture has been designed to increase modularity and extensibility of the code, allowing users to add new back-ends and physics equations while maintaining the same code structure. This allows users to reuse portions of the code that are independent of the physics equations, the back-end, or both. The layer of computing procedures maintains a lean structure that can be highly optimized with respect to the implemented back-end.•Input handling is now based on the classic .ini format improving both user readability and input data management.•A family of new kinetic energy and entropy preserving schemes (KEEP) are now available and can be selected for stable, non-dissipative and accurate spatial discretization of the convective terms of the Navier–Stokes equations in smooth flow regions [2]. Concerning the shock-capturing flux, the improved low-dissipative WENO-Z scheme proposed by [3] is now available.•New inflow boundary conditions based on the recycling/rescale approach [4] have been implemented for the simulation of spatially evolving compressible turbulent boundary layers. Moreover, a new inflow condition based on the solution of the compressible Blasius equation is available to take into account the case of laminar boundary layers.•The constitutive relations have been generalized to take into account thermally perfect gases with variable specific heats, approximated with polynomial functions of the temperature that can be specified by the user [5].•A new stretching function has been implemented to improve the distribution of grid nodes for the computation of wall-bounded turbulent flows. The formulation blends uniform near-wall spacing with uniform resolution in terms of Kolmogorov units in the outer wall layer, guaranteeing accuracy with higher computational efficiency [6].Nature of problem: The code solves the compressible Navier–Stokes equations in Cartesian coordinates for a thermally perfect gas. The solver is designed for direct numerical simulation (DNS) of compressible supersonic turbulent boundary layers and various canonical configurations are supported, including turbulent channel flow, laminar and turbulent boundary layer and shock-wave/boundary layer interaction.Solution method: The equations are discretized using high-order finite difference approximations with hybrid low-dissipative/shock-capturing capabilities and the time advancement is performed using a Runge–Kutta scheme.

A multi-degree-of-freedom gas kinetic multi-prediction implicit scheme

A multi-scale implicit multi-degree-of-freedom (MDOF) kinetic model with molecular translational, rotational and vibrational effects is presented. The evolution and exchange of energy among translational, rotational and vibrational degrees of freedom are demonstrated by three coupled relaxation processes. An orthogonal polynomial system is used to involve heat-transfer and viscosity properties in construction of a sequence of objective distribution functions at various relaxation stages. Based on finite volume discrete velocity method framework, the asymptotic preserving discrete unified gas-kinetic scheme (DUGKS) flux is adopted to preserve particle motion information. A second-order prediction scheme based on the Navier-Stokes flux is constructed to predict macroscopic variables from macroscopic residuals for implicit DUGKS iteration, which contains a multiple prediction methodology. The current MDOF kinetic model provides a concrete insight into energy exchange between the rotational and vibrational degrees of freedom during molecular inelastic collisions. The accurate prediction procedure significantly accelerates convergence. Several numerical test cases, including rarefied gas flow in lid-driven cavity, variable specific heat ratio shock structure, hypersonic circular cylinder flows at different Knudsen and Mach numbers, and hypersonic flat plate flow, are performed to validate the accuracy and efficiency of present model. All numerical results of the present method agreed well with those of the reference data. A 2∼3 orders-of-magnitude improvements in computational efficiency of the multi-scale implicit method are achieved compared with the explicit method. It demonstrated that the present method is a promising scheme considering vibration-rotation-translation energy exchange of poly-atomic molecules for the fast simulation of multi-scale flows from low-speed incompressible flow to hypersonic flow, from continuum to rarefied regime.

Melting and Crystallization of Free Copper and Nickel Nanoclusters using Molecular Dynamics Simulations

Molecular dynamics simulations with second nearest neighbor modified embedded atom method have been performed on free-standing copper and nickel nanoclusters composed of 2048 atoms. Thermo-dynamical, dynamical and structural properties of the nanoclusters have been investigated during melting and crystallization process. Variation of potential energy, specific heat and self-diffusion coefficient of atoms during the phase transition have been used to determine the melting and crystallization points. Radial distribution function is used to characterize the structural changes of the nanoclusters. The melting and solidification profiles of both the nanoclusters showed hysteresis behavior, which is attributed to the undercooling effect during the solidification process. The melting temperature is about few hundreds of Kelvins higher than the crystallization temperature. The result shows that the melting and crystallization temperature of copper nanocluster are 1360[Formula: see text]K[Formula: see text][Formula: see text][Formula: see text]5[Formula: see text]K and 1090[Formula: see text]K[Formula: see text][Formula: see text][Formula: see text]5[Formula: see text]K, respectively, and those of the nickel nanoclusters are 1710[Formula: see text]K[Formula: see text][Formula: see text][Formula: see text]5[Formula: see text]K and 1390[Formula: see text]K[Formula: see text][Formula: see text][Formula: see text]5[Formula: see text]K, respectively.