Thomson Coefficient Research Articles

The Elusive Thomson Effect in Thermoelectric Devices. Experimental Investigation from 363 K to 213 K on Various Peltier Modules

At steady state, in the governing equation of one-stage thermoelectric cooler, the heat resulting from Fourier conduction is balanced by heat generation due to the Joule and Thomson effects inside semiconductors. Since the heat flux observed at the junction of a semiconductor, r pair includes the Peltier effect and the Fourier heat flux caused by both the aforementioned contributions, the Thomson effect is easily masked by the Joule heat, which makes it elusive. With the aim of highlighting the contribution of the Thomson effect, measurements were carried out in the temperature range from 363 K to 213 K on different Peltier modules. The temperature dependence of the Seebeck and Thomson coefficients was evaluated as well as the electrical resistivity, and thermal conductivity of the Peltier modules examined. The results obtained show that the temperature dependence of the thermoelectric properties can reduce the cooling capacity of the Peltier module compared to what is declared in the technical datasheets of the commercial devices. The analyses allow us to conclude that an increase in the Thomson effect could have a positive effect on the performance of the Peltier only if it were possible to reduce the Joule contribution simultaneously.

Modeling and analysis of the influence of Thomson effect on micro-thermoelectric coolers considering interfacial and size effects

Micro-thermoelectric coolers have great potential in the thermal management of highly integrated electronic devices, especially the local cooling. This paper develops a numerical model to explore the influence of Thomson effect on the cooling performance of micro-thermoelectric coolers, capturing interfacial and size effects. The presented model is validated with a commercial micro-thermoelectric cooler. And, analyses are carried out with respect to micro-thermoelectric coolers of different sizes, under different temperatures and cooling loads. The results indicate that a positive Thomson coefficient can improve the cooling capacity, and higher current and thickness correspond to greater impact of Thomson effect. In addition, the decrease of minimum cooling temperature caused by Thomson effect is even more obvious under higher cooling load. The results also show that the influence of Thomson effect on the maximum cooling temperature difference gradually becomes weaker as the cross area to thickness ratio increases. For heat fluxes of 100 W/cm2 and 200 W/cm2, the minimum cooling temperature can be respectively reduced by 2.1 K and 4.1 K, considering Thomson effect. In addition, for the thickness of 10 μm, the increment of maximum cooling temperature difference gradually declines from 2.2 K to 1.1K as the cross area to thickness ratio increases.

Effect of massive gravity on Joule–Thomson expansion of the charged AdS black hole

In this paper, we have studied how the presence of massive gravity modifies the Joule–Thomson expansion of the charged AdS black hole. We showed that the graviton mass and the coupling parameters affect the constant mass curve, the Joule–Thomson coefficient, and the inversion curve on a significant level. For the graviton mass or the coupling parameters at/above certain values, the Joule–Thomson expansion of the black hole with given mass and charge is only possible to lead to the heating without leading to the cooling. In addition, massive gravity can make the heating and cooling in the Joule–Thomson expansion of the black hole happen faster or slower, depending on the sign of the coupling parameters. Furthermore, the lower value of the inversion temperature can appear at the nonzero pressure.

Effects of Lovelock gravity on the Joule–Thomson expansion

Effects of Lovelock gravity on the Joule–Thomson expansion are probed from various perspectives. The well-known Joule–Thomson coefficient is derived with both the explicit expression and intuitive image presented. Moreover, the inversion curves showing the relation between the inversion temperature and the inversion pressure are studied. It is shown that for given inversion pressure, the inversion temperature of the case ( is the Lovelock parameter) is much lower than that of the case . And the inversion temperature tends to decrease with , in contrast to the effect of the electric charge. It is also shown that the ratio between the minimum inversion temperature and the critical temperature decreases with for . Furthermore, the isenthalpic curves are investigated with rich physics revealed. The intersection point between the isenthalpic curve and the inversion curve is exactly the inversion point discriminating the heating process from cooling process. It is shown that both the inversion temperature and the inversion pressure for are much lower for the same given mass of the black hole, showing the effect of Lovelock gravity. Last but not the least, we discuss the uncharged Lovelock AdS black holes. It is shown that the Joule–Thomson coefficient is always positive, suggesting the expansion is always in the regime of cooling process. And no inversion temperature exists, in contrast to the case . Isenthalpic curves are also quite different since the temperature increases monotonically with the pressure when the mass is specified.

The application of numerical and analytical approaches for the determination of thermophysical properties of Al–Si–Cu–Mg alloys

Thermophysical properties are very important to simulate the behavior of materials. Computer simulations are low cost as compared to what is needed for physical simulations, as far as it normally requires only a computer, a model and a computer language. However, the accuracy of numerical simulations depends on the quality of the thermophysical properties used in the prediction of physical phenomena, such as fluid flow, heat transfer, alloy solidification and solid-state phase transformations. The thermophysical properties for pure metals are widely available in the literature; nevertheless, for multicomponent metallic alloys, this is not the case. In this paper, a novel definition of non-equilibrium Gibbs–Thomson coefficient is presented, and thermodynamics calculations are carried out based on analytical and numerical approaches for the prediction of: liquidus and eutectic temperatures, equilibrium and non-equilibrium latent heats of fusion, solid–liquid surface tensions, solid and liquid densities, equilibrium and non-equilibrium Gibbs–Thomson coefficients, viscosity and surface tension as a function of temperature of quaternary Al–Si–Cu–Mg alloys.

Spin analogs of thermo-magnetoelectric phenomena for heat switches

The study of novel thermal effects associated with spin current is fundamental to understanding the relationship between magnetoelectric and thermal phenomena. The central focus of attention of our research is on the spin analog of the Thomson effect as the most promising in terms of its use in heat switches of solid-state coolers. In order to model heat flows, the heat conduction equation is derived in the presence of magnetic and electric fields. Applying the developed theoretical framework, the spin Thomson coefficient is calculated for a yttrium-iron garnet plate. It is demonstrated that this coefficient strongly depends on the thickness of the plate. The corresponding estimates of the heat flux carried by the spins are also obtained. For a 200 nm plate, it is 6.81 W/cm2, which is comparable to the heat fluxes in the best thermal switches. Moreover, the results of the paper indicate at the possibility of further increase in the flux by an optimal choice of plate thickness and magnitude of magnetic field.

Thomson Power in the Model of Constant Transport Coefficients for Thermoelectric Elements

The analytical expressions derived using simple models provide clear insights on the processes in thermoelectric coolers. The model of constant transport coefficients (CTC) considers that the thermal conductivity, the electrical resistivity and the Thomson coefficient are constants. The version of the CTC model that has become standard in the description of the global energy balance may yield grossly inaccurate predictions for thermoelectric cooling applications. We show that these failures can be avoided by accurately describing the Thomson effect in the energy balance. Calculations for bismuth telluride semiconductors show that deviations as large as a factor of three in the Thomson power contribution to the global balance may be found under conditions of practical interest. Compared to the standard version (valid only for moderate temperature gradients), the improved version (valid for highly nonlinear temperature distributions) of the CTC model predicts that a larger fraction of the power released by the electric current leaves the thermoelectric element through the hot boundary. Significant differences in the estimations of the cooling capacity and the coefficient of performance of the thermoelectric cooler are also observed.

Effect of Thomson and thermal loading due to laser pulse in a magneto‐thermo‐elastic porous medium with energy dissipation

AbstractThe present work attempts to investigate the influence of the Thomson heating and the Fourier's heat conduction, in the presence of a magnetic field, on half‐space thermo‐electricity solid with voids. The material is heated by a non‐Gaussian laser beam with pulse duration of 0.23 ps. The heat conduction equation is affected by the Thomson coefficient. A constant Thomson coefficient, instead of traditionally a constant Seebeck coefficient, was assumed. The charge density of the induced electric current is taken as a function of time. The basic governing equations are modified by using Green–Naghdi theory of type‐III. A normal mode method is proposed to analyze the problem and obtain numerical solutions. The results of the physical quantities have been illustrated graphically by a comparison between two values of time, with and without void parameters, as well as with and without Thomson coefficient.

The Thermocouple Revisited: The Benedicks and Seebeck Effects

Abstract Through altering the ambient environment of the iron conductor with respect to the copper conductor of an iron-copper thermocouple, the output emf of the thermocouple was reduced by a factor of almost two. This reduction was apparently a result of a Benedicks emf. Such a Benedicks emf was produced here in a continuous iron conductor. The Benedicks emf produced was about half the expected Seebeck emf from the copper-iron couple. The source of the Benedicks emf can be explained as a Seebeck charge separation produced by the effect of ambient radiation in one conductor of the thermocouple, while the effect of ambient radiation was deliberately removed in the other part of the conductor. The effect of ambient radiation was removed by matching the surface temperature gradient of the second part of the conductor point for point with an external (or ambient) temperature gradient. The conclusions of this research contradict the assumption made by William Thomson [1] that the ambient surroundings have no effect on thermocouple behavior. This assumption, which was made almost two hundred years ago, has never been experimentally refuted. The idea of using such a temperature match arose from a lesson learned from observations of directly measured Thomson coefficients by Jacovelli et al. [2]

The Thermocouple Revisited: The Thomson Effect

Abstract Measurements of Thomson (later Lord Kelvin) coefficients are made in an evacuated region on a silver sample with a novel transducer in temperature intervals T A ± 20 K {T_{A}}\pm 20\hspace{0.1667em}\text{K} , where the T A {T_{A}} are very carefully controlled ambient temperatures. This is the first systematic examination of Thomson coefficients in these temperature intervals. The Thomson coefficients when plotted against T, the temperature of measurement, are found to be discontinuous precisely at T A {T_{A}} . When the Thomson coefficients are multiplied by a transformation involving T and T A {T_{A}} , a linear curve in T results. Examinations here of measurements of Thomson coefficients produced by others show multiple values at T in some cases and odd behavior in other cases. Multiplying the results of others by the transformation discovered here almost always produces linear curves. The conclusions are the following. (1) Thomson’s explicit assumption that the Thomson effect involves no energy exchange with surroundings was wrong. (2) Any non-equilibrium thermodynamic approach to deriving the Thomson effect must take into account the energy exchange with the surroundings and consequently must be made in three dimensions. (3) From the work here and that of others, the energy exchange with the environment is probably mostly thermal radiation.

New Thermodynamic Approach for Nonspherical Molecules Based on a Perturbation Theory for Ellipsoids

We propose a new thermodynamic approach for nonspherical molecules by applying a perturbation theory in which an anisotropic intermolecular potential, the hard Gaussian overlap, is the reference system. The new equation of state (EoS) modifies the usual statistical associating fluid theory (SAFT) approach by combining both segment and chain contributions as a single anisotropic term. Fluid particles are represented as ellipsoids rather than a set of a few tangential spherical segments. The perturbed potential is taken as a square well, following the original formulation of SAFT with attractive potential of variable range (SAFT-VR SW). The parameters of the proposed model were optimized to fit vapor pressures and saturated liquid densities for ethane and carbon dioxide. Derivative properties, such as isobaric and isochoric heat capacities, speed of sound, Joule–Thomson coefficient, thermal expansion coefficient, and isothermal compressibility, were evaluated at supercritical conditions up to 70 MPa for eth...

On the Effect of Thomson and Initial Stress in a Thermo-Porous Elastic Solid under G-N Electromagnetic Theory

The present work investigated the effect of Thomson and initial stress in a thermo-porous elastic solid under G-N electromagnetic theory. The Thomson coefficient affects the heat condition equation. A constant Thomson coefficient, instead of traditionally a constant Seebeck coefficient, is assumed. The charge density of the induced electric current is taken as a function of time. A normal mode method is proposed to analyze the problem and to obtain numerical solutions. The results that were obtained for all physical sizes are graphically illustrated and we offer a comparison between the type II G-N theory and the G-N theory of type III, both in the present case and in the absence of specific parameters, as initial stress, pores and the Thomson effect. Some particular cases are also discussed in the context of the problem. The results indicate that the effect of initial stress, Thomson coefficient effect, and magnetic field are very pronounced.

Uncertainty analysis of microsegregation during laser powder bed fusion

Quality control in additive manufacturing can be achieved through variation control of the quantity of interest (QoI). We choose in this work the microstructural microsegregation to be our QoI. Microsegregation results from the spatial redistribution of a solute element across the solid–liquid interface that forms during solidification of an alloy melt pool during the laser powder bed fusion process. Since the process as well as the alloy parameters contribute to the statistical variation in microstructural features, uncertainty analysis of the QoI is essential. High-throughput phase-field simulations estimate the solid–liquid interfaces that grow for the melt pool solidification conditions that were estimated from finite element simulations. Microsegregation was determined from the simulated interfaces for different process and alloy parameters. Correlation, regression, and surrogate model analyses were used to quantify the contribution of different sources of uncertainty to the QoI variability. We found negligible contributions of thermal gradient and Gibbs–Thomson coefficient and considerable contributions of solidification velocity, liquid diffusivity, and segregation coefficient on the QoI. Cumulative distribution functions and probability density functions were used to analyze the distribution of the QoI during solidification. Our approach, for the first time, identifies the uncertainty sources and frequency densities of the QoI in the solidification regime relevant to additive manufacturing.

A new dimensionless number for thermoelectric generator performance

Thermoelectric generators (TEG) convert heat into electricity and offer a green option for renewable energy generation. The Thomson effect has been proven to impact the overall performance of TEGs negatively but is ignored in the widely-used formula for TEG maximum efficiency calculation. In this study, a new dimensionless number called the Ury number (Ur) is introduced to capture the influence of the Thomson effect on TEG power output and maximum efficiency. Ur is defined as the ratio between the Thomson coefficient and the Seebeck coefficient. It is found that as Ur increases both TEG output power and maximum efficiency decrease. Ur combined with the device figure of merit, ZT, can better dictate the overall performance of a TEG.

A straightforward 2ω technique for the measurement of the Thomson effect.

We present a simplified, rapid, and accurate method for the measurement of the thermoelectric Thomson coefficient by the dynamical heating of a suspended wire by an alternating current. By applying a temperature gradient across the wire, we find that the response at the second harmonic of the excitation frequency is directly proportional to the Thomson coefficient. The absolute thermoelectric coefficient of a single material can therefore be extracted with high precision by using a phase sensitive detector. We test our method on platinum and nickel wires and develop both analytical and numerical models to determine the leading sources of error.

Revisiting the Saha–Basu equation of state

The Saha–Basu equation of state, which has attracted little attention from the scientific community, is here revisited. This equation has been derived using an approach that is different from the original approach. Expressions for some physical parameters, such as critical constants, Boyle’s temperature, critical coefficients etc, have been derived and the equation has been expressed in terms of reduced parameters. Amagat’s curves have been explained using the virial form of the equation. Some thermodynamic quantities, such as the Joule–Thomson coefficient, inversion temperature and heat capacity relations, have been arrived at from this equation of state. The comparison has been made with other related equations of state.

Nonlinear electrodynamics AdS black hole and related phenomena in the extended thermodynamics

In this paper, we present the analytic solution for Anti-de Sitter-Nonlinear electrodynamics (AdS-NED) black hole in four dimensions. We study tunneling of vector particles from the AdS-NED black hole to find Hawking temperature as well as its thermodynamical properties in usual and extended phase space. Then we explore the properties of pressure–volume criticality by analyzing the phase diagram and its free energy. Finally, we investigate the Joule–Thomson coefficient, in which the inversion curve of warming and cooling are studied, and the ratio between the inverse temperature and critical temperature are computed in the black hole solution.

The influence of Thomson effect and inclined loads in an electro-magneto-thermoelastic solid with voids under green–Naghdi theories

The present investigation deals with the 2-dimensional deformation in a homogeneous thermoelastic solid with voids subjected to inclined loads. The heat conduction equation is affected with the Thomson coefficient. The basic governing equations are modified by using Green–Naghdi theory of type-III. The normal mode analysis technique is used to obtain the components of stress, strain, temperature, induced magnetic field and change in volume fraction field. The variations of these quantities have been depicted graphically in the Green–Naghdi theories of type-II and III for an insulated boundary. From numerical calculations, the effect of Thomson parameter and angle of inclination on a homogeneous, isotropic, electro-magneto-thermoelastic material with voids is revealed and discussed.

Thermodynamic evaluation of irreversibility and optimum performance of a concentrated PV-TEG cogenerated hybrid system

In this paper, the thermodynamics evaluation of an irreversible CPV-TEG cogenerating system, having Siemens SP75 PV module and commercially available Bi2Te3 TE module, has been investigated for wide solar spectrum to encompass the winter and summer solar radiation. Modeling and simulation of the hybrid system has been carried out to understand the feasibility of the system and to determine the irreversibilities present in the hybrid system. The irreversibilities or exergy destruction caused by the irreversible conversion process of solar energy into electricity are calculated using exergy analysis based on second law of thermodynamics. The various exergy losses occurring in the hybrid system have been calculated using exergy analysis. The effects of the incident solar irradiance varying in a wide range from 100 W/m2 to 1000 W/m2, TEG junction temperature ratio, concentration ratio, TEG current, Thomson coefficient, irreversibilities or exergy destruction and the incoming solar radiation exergy have been studied. The results showed that the Thomson effect has adverse effect on the performance of the hybrid system and the irreversibilities increase with increase in concentration ratio, C. Further, the power output of hybrid system increases by 86% as C increases from 1 to optimum value of 3 and the exergy efficiency is higher than the energy efficiency by 8%. The higher values of the irreversibilities make the system less inefficient and therefore, significant improvements are required because the elevated temperature could result in hot spots formation. The results of this analysis may be helpful in designing of practical CPV-TEG hybrid system.

Estimation of density and compressibility factor of natural gas using artificial intelligence approach

Natural gas density is commonly measured by Coriolis density meters and gas chromatographs, both of which are used to calculate the natural gas mass flow rate. In this study, two networks are proposed to predict the density and compressibility factor of natural gas. The first network (N1) uses temperature, pressure and Joule Thomson (JT) coefficient of natural gas as input variables and density of natural gas is selected to be the target. This network is proposed to predict the natural gas density at natural gas pressure drop stations (CGSs). For this network, the gas mixture compositions are unnecessary. The second network (N2) is proposed based on the pseudo reduced temperature and pressure as input variables that the network by using these two variables can predict the density and compressibility factor of natural gas. This model needs the gas mixture compositions. For these targets, a novel idea based on artificial intelligence is used. Five models of artificial intelligence are implemented that are fuzzy inference system (FIS), adaptive neuro-fuzzy inference system (ANFIS), ANFIS optimized with genetic algorithm (ANFIS-GA), multilayer feed-forward neural network (MLFFNN) and group method of data handling (GMDH). The results demonstrated that the ANFIS-GA and GMDH model performed better than the FIS, MLFFNN and ANFIS models. For N1, root mean square error (RMSE) for ANFIS-GA and GMDH models were obtained as 0.2405 and 0.2042 (kg/m3), respectively. For N2 (compressibility factor), the value of RMSE for ANFIS-GA and GMDH models consecutively was achieved 0.0061 and 0.0054. Also, for N2 (density), RMSE for ANFIS-GA and GMDH models was taken 2.2735 and 2.6113, respectively. These values of RMSE were reported for the testing phase of the models.