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Pierre Carlès - One of the best experts on this subject based on the ideXlab platform.
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Thermoacoustic waves near the liquid‐vapor critical point
The Journal of the Acoustical Society of America, 2008Co-Authors: Pierre CarlèsAbstract:The thermal relaxation in a fixed‐volume cell filled with a near‐critical fluid is governed by the rapid expansion of thermal boundary layers, which drive a series of thermo‐acoustic waves in the bulk fluid. The long‐term cumulative Effect of these waves is to increase the pressure in the cell, which in turn leads to a global temperature increase (a process named the Piston Effect). Recently and for the first time, the thermo‐ acoustic waves produced by the Piston Effect have been measured experimentally using interferometric methods [Y. Miura et al., to appear in Phys. Rev. E (2006)]. In the present work, we use asymptotic methods in order to derive a complete theoretical model of the Piston‐Effect‐driven acoustic waves, applicable to real fluid equations of state and to arbitrary reduced temperatures. The predictions of this model are compared to the above‐mentioned experimental data, and an excellent agreement is observed without any fitting parameter. This result confirms the high precision of the dat...
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Thermoacoustic waves near the liquid-vapor critical point
Physics of Fluids, 2006Co-Authors: Pierre CarlèsAbstract:The thermal relaxation in a fixed-volume cell of a near-critical fluid is governed by the rapid expansion of thermal boundary layers, which drive a series of thermoacoustic waves in the bulk fluid. The long-term cumulative Effect of these waves is to increase the pressure in the cell, which in turn leads to a global temperature increase (a process called the “Piston Effect”). Recently, and for the first time, the thermoacoustic waves produced by the Piston Effect have been measured experimentally using interferometric methods [Y. Miura et al., Phys. Rev. E 74, 010101(R) (2006)]. In the present work, we use asymptotic methods in order to derive a complete theoretical model of the Piston-Effect-driven acoustic waves, applicable to real fluid equations of state and to arbitrary reduced temperatures. The predictions of this model are compared to the above-mentioned experimental data, and an excellent agreement is observed without any fitting parameter. This result confirms the high precision of the data in qu...
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Two typical time scales of the Piston Effect.
Physical Review E, 2005Co-Authors: Pierre Carlès, Kokou Sename Enyonam DadzieAbstract:The existence of a fourth mode of heat transfer near the critical point, named the Piston Effect, has been known for more than a decade. The typical time scale of temperature relaxation due to this Effect was first predicted by Onuki et al. [Phys. Rev A 41, 2256 (1990)], and this author’s formula has been extensively used since then to predict the thermal behavior of near-critical fluids. Recent studies, however, pointed out that the critical divergence of the bulk viscosity could have a strong influence on Piston-Effect-related processes. In this paper, we conduct a theoretical analysis of near-critical temperature relaxation showing that the Piston Effect is not governed by one (as was until now believed) but by two typical time scales. These two time scales exhibit antagonistic asymptotic behaviors as the critical point is approached: while the classical Piston-Effect time scale (as predicted by Onuki et al.) goes to zero at the critical point (critical speeding up), the second time scale (related to bulk viscosity) goes to infinity (critical slowing down). Based on this property, an alternative method for measuring near-critical bulk viscosity is proposed.
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Two typical time scales of the Piston Effect.
Physical review. E Statistical nonlinear and soft matter physics, 2005Co-Authors: Pierre Carlès, Kokou Sename Enyonam DadzieAbstract:The existence of a fourth mode of heat transfer near the critical point, named the Piston Effect, has been known for more than a decade. The typical time scale of temperature relaxation due to this Effect was first predicted by Onuki [Phys. Rev A 41, 2256 (1990)], and this author's formula has been extensively used since then to predict the thermal behavior of near-critical fluids. Recent studies, however, pointed out that the critical divergence of the bulk viscosity could have a strong influence on Piston-Effect-related processes. In this paper, we conduct a theoretical analysis of near-critical temperature relaxation showing that the Piston Effect is not governed by one (as was until now believed) but by two typical time scales. These two time scales exhibit antagonistic asymptotic behaviors as the critical point is approached: while the classical Piston-Effect time scale (as predicted by Onuki ) goes to zero at the critical point (critical speeding up), the second time scale (related to bulk viscosity) goes to infinity (critical slowing down). Based on this property, an alternative method for measuring near-critical bulk viscosity is proposed.
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Temperature and density relaxation close to the liquid-gas critical point: an analytical solution for cylindrical cells.
Physical review. E Statistical nonlinear and soft matter physics, 2005Co-Authors: Pierre Carlès, Mark Weilert, Fang Zhong, M BarmatzAbstract:We present a study of the temperature and density equilibration near the liquid-gas critical point of a composite system consisting of a thin circular disk of near-critical fluid surrounded by a copper wall. This system is a simplified model for a proposed space experiment cell that would have 60 thin fluid layers separated by perforated copper plates to aid in equilibration. Upper and lower relaxation time limits that are based on radial and transverse diffusion through the fluid thickness are shown to be too significantly different for a reasonable estimate of the time required for the space experiment. We therefore have developed the first rigorous analytical solution of the Piston Effect in two dimensions for a cylindrically symmetric three-dimensional cell, including the finite conductivity of the copper wall. This solution covers the entire time evolution of the system after a boundary temperature step, from the early Piston Effect through the final diffusive equilibration. The calculation uses a quasistatic approximation for the copper and a Laplace-transform solution to the Piston Effect equation in the fluid. Laplace inversion is performed numerically. The results not only show that the equilibration is divided into three temporal regimes but also give an estimate of the amplitudes of the remaining temperature and density inhomogeneity in each regime. These results yield characteristic length scales for each of the regimes that are used to estimate the expected relaxation times in the one- and two-phase regions near the critical point.
Bernard Zappoli - One of the best experts on this subject based on the ideXlab platform.
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Thermal Effects in Near-Critical Fluids: Piston Effect and Related Phenomena
Advanced Applications of Supercritical Fluids in Energy Systems, 2017Co-Authors: D. Beysens, Yves Garrabos, Bernard ZappoliAbstract:In this chapter is addressed the very particular thermal behavior that supercritical fluids exhibit when nearing their critical point. In this region, supercritical fluids exhibit strong anomalies in their thermodynamic and transport properties. Pressure change associated to a temperature variation leads to a nearly isentropic thermalization of the fluid, the “Piston Effect”, which leads to a paradoxical “critical speeding-up”. Bulk fluid temperature is uniform, temperature gradients are confined in thermal boundary layers, making the bulk fluid a thermal short-circuit. It follows very particular behavior, as dynamic heat pipes or heat going seemingly backward, in apparent contradiction with the 2nd principle of thermodynamics. Under an acceleration field, thermal convection occurs only in the boundary layers, which paradoxically can enhance the fluid stability or even cool the fluid after a heat pulse. These Effects can deeply modify the supercritical fluids thermal behavior in space and energy activities, giving to these Effects socio-economic relevance.
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Heat Transport by the Piston Effect: Experiments
Heat Transfers and Related Effects in Supercritical Fluids, 2014Co-Authors: Bernard Zappoli, Daniel Beysens, Yves GarrabosAbstract:Heat transfer experiments are presented where heat pulses are produced by a point-like thermistor at the center of a thermostated cell. This configuration allows the theoretical analyses of the Piston Effect mechanism to be tested. It is observed, first, a hot boundary layer, developing at the heat source, which shows large coupled density-temperature inhomogeneities. This part relaxes by a diffusive process, whose density and temperature relaxations are slowed down close to the critical point. During heating, the dynamics of the bulk fluid part, which remains uniform in temperature and density, is accelerated near the critical point and governed by the characteristic time of the Piston Effect. At the thermostated walls, a slightly cooler boundary layer forms, simultaneously. It cools down the bulk by also a Piston Effect mechanism. The final sample cell relaxation to the temperature and density equilibration is governed by the time of the thermal diffusion, which corresponds to the slowest mechanism. Comparison with a one-dimensional model shown good agreement with experimental results when the characteristic length of the three-dimensional sample cell is obtained from a pancake cell model. A brief illustration of the situation in the presence of gravity is also given.
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Interaction Between the Piston Effect and Gravitational Convection
Heat Transfers and Related Effects in Supercritical Fluids, 2014Co-Authors: Bernard Zappoli, Daniel Beysens, Yves GarrabosAbstract:Strong gravitational instabilities are observed on the ground in heated near-critical fluids. However, the Piston Effect homogenizes temperature. The origin of strong convective instabilities in a near homogeneous pure fluid addresses the question posed by the evaluation of the interaction between the gravitational convection and the Piston Effect. After a brief one-dimensional model generalization to the two- or three-dimensional models subjected to a vertical steady state acceleration, the two-dimensional studies of the experimental heating are detailed for two configurations: a side-heated cavity and an immersed point heat source.
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Temperature and Density Equilibration
Heat Transfers and Related Effects in Supercritical Fluids, 2014Co-Authors: Bernard Zappoli, Daniel Beysens, Yves GarrabosAbstract:The basic features of thermoacoustic Effects in a near-critical fluid layer is presented for the simplest (one dimensional) configuration. A temperature step is imposed at one wall side of a slab-like container filled with a near-supercritical pure fluid. The other wall side of the container is thermally isolated. Gravity is assumed to be zero, so buoyant convection is absent from the system. The transient behavior of a given fluid mass is thus studied between two thermodynamic equilibrium states corresponding to the temperature step. It will be shown in particular that the respective relaxations of temperature and density towards equilibrium are uncoupled to first order. The Piston Effect homogenizes temperature on a timescale that is much shorter than the diffusion one, while density relaxes diffusively in a quasi-isothermal medium. A thermodynamic description of heat exchanges in a near critical fluid is given first. This shows the source of characteristic timescale of the adiabatic temperature equilibration. This characteristic time scale compares well with the characteristic time of the Piston Effect obtained from the detailed hydrodynamic approach presented hereafter.
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Heterogeneous reaction induced by the Piston Effect in supercritical binary mixtures
Chemical Engineering Science, 2007Co-Authors: Isabelle Raspo, Sofiane Meradji, Bernard ZappoliAbstract:It is now well established that the large compressibility of supercritical fluids is responsible for the strong enhancement of the thermo-acoustic heating, leading to the speeding up of the heat transport thanks to the Piston Effect instead of the expected slowing down. We show in this paper, through numerical simulations, that the hydrodynamics behavior of supercritical fluids also couples with the critical behavior of the solubility of solids to cause the release of a heterogeneous reaction at solid surfaces in dilute binary supercritical mixtures.
Akihiro Nakano - One of the best experts on this subject based on the ideXlab platform.
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Studies on Piston and soret Effects in a binary mixture supercritical fluid
International Journal of Heat and Mass Transfer, 2007Co-Authors: Akihiro NakanoAbstract:Heat and mass transport phenomena in a binary mixture compressible supercritical fluid around the pseudo-critical line were investigated theoretically and numerically. In this study, we focused on supercritical artificial air with a composition of 79% nitrogen and 21% oxygen, and investigated the Piston Effect, the soret Effect, and the interactions between these Effects. We derived thermo-fluid dynamic equations, in which the compressibility of the fluid, the temperature, the pressure, and the concentration dependences of the entropy were taken into account. The governing equations were solved numerically by using the finite difference method. We could verify that the thermal energy was propagated by the Piston Effect in a binary mixture supercritical fluid, and the concentration change certainly occurred due to the soret Effect. Moreover, we could also estimate the thermal diffusion ratio, which made a direct correlation between the temperature gradient and the concentration gradient.
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Piston Effect in supercritical nitrogen around the pseudo-critical line
International Communications in Heat and Mass Transfer, 2005Co-Authors: Akihiro Nakano, Masao ShiraishiAbstract:Abstract The combination of very high thermal compressibility and small thermal diffusion near the critical points of fluids affects thermal energy propagation, leading to the formation of weak acoustic waves as carriers of thermal energy. This heat transfer phenomenon is called the Piston Effect. It has been reported that the Piston Effect appears near the critical point. In this study, the Piston Effect in supercritical nitrogen was investigated by use of a laser holography interferometer. Since natural convection due to gravity interferes with the Piston Effect under terrestrial conditions, we attempted to suppress the generation of natural convection by adding heat from the top of the experimental cell and successfully observed the typical temperature profiles formed by the Piston Effect around the pseudo-critical line. The pressure and the temperature are relatively higher than the critical pressure and the critical temperature.
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Visualization for heat and mass transport phenomena in supercritical artificial air
Cryogenics, 2005Co-Authors: Akihiro Nakano, Masao ShiraishiAbstract:A laser holography interferometer is applied to investigate heat and mass transport phenomena around the pseudo-critical line of supercritical artificial air with a composition of 79% nitrogen and 21% oxygen. In a previous study, we successfully observed the heat transport phenomenon, the Piston Effect, around the pseudo-critical line of nitrogen. The same experimental set-up is applied to the supercritical artificial air, which is a compressible binary mixture fluid. We attempt to suppress the generation of natural convection, and successfully observe the heat and mass transport phenomena, which are the soret Effect and the Piston Effect, respectively. Here, we discuss these Effects observed in the supercritical artificial air.
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Numerical simulation for the Piston Effect and thermal diffusion observed in supercritical nitrogen
Cryogenics, 2004Co-Authors: Akihiro Nakano, Masao ShiraishiAbstract:Heat transport mechanism in supercritical nitrogen near the pseudo-critical line is investigated using a two-dimensional calculation model that is a rectangular cavity with a horizontal heated wall located at the top. The thermo-fluid dynamics equations are solved directly using the finite difference method. The calculation results qualitatively agree with the experimental results, which were obtained using a laser holography interferometer. It is verified that thermal energy is propagated by the Piston Effect around the pseudo-critical line.
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Application of laser holography interferometer to heat transport phenomena near the critical point of nitrogen
Cryogenics, 2001Co-Authors: Akihiro Nakano, Masao Shiraishi, Masahide MurakamiAbstract:A laser holography interferometer is applied to investigate heat transport phenomena near the critical point of nitrogen. The very high thermal compressibility and small thermal diffusion near the critical point of fluids affect thermal energy propagation, lead to the formation of weak acoustic waves as carriers of thermal energy. This heat transfer phenomenon is called the Piston Effect. The Piston Effect in supercritical nitrogen is investigated using a laser holography interferometer. Natural convection due to gravity interferes with the Piston Effect under terrestrial conditions. Therefore, we attempt to suppress the generation of natural convection by creating stable density stratification in the cell. The experiment consisted of two different procedures. In the first, heat was added from the bottom of the experimental cell, while in the second, heat is added from the top of the cell. From the two results, we successfully extracted the heat transfer phenomenon, the Piston Effect, which is considered to be the fourth mechanism of heat transfer.
Masao Shiraishi - One of the best experts on this subject based on the ideXlab platform.
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Piston Effect in supercritical nitrogen around the pseudo-critical line
International Communications in Heat and Mass Transfer, 2005Co-Authors: Akihiro Nakano, Masao ShiraishiAbstract:Abstract The combination of very high thermal compressibility and small thermal diffusion near the critical points of fluids affects thermal energy propagation, leading to the formation of weak acoustic waves as carriers of thermal energy. This heat transfer phenomenon is called the Piston Effect. It has been reported that the Piston Effect appears near the critical point. In this study, the Piston Effect in supercritical nitrogen was investigated by use of a laser holography interferometer. Since natural convection due to gravity interferes with the Piston Effect under terrestrial conditions, we attempted to suppress the generation of natural convection by adding heat from the top of the experimental cell and successfully observed the typical temperature profiles formed by the Piston Effect around the pseudo-critical line. The pressure and the temperature are relatively higher than the critical pressure and the critical temperature.
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Visualization for heat and mass transport phenomena in supercritical artificial air
Cryogenics, 2005Co-Authors: Akihiro Nakano, Masao ShiraishiAbstract:A laser holography interferometer is applied to investigate heat and mass transport phenomena around the pseudo-critical line of supercritical artificial air with a composition of 79% nitrogen and 21% oxygen. In a previous study, we successfully observed the heat transport phenomenon, the Piston Effect, around the pseudo-critical line of nitrogen. The same experimental set-up is applied to the supercritical artificial air, which is a compressible binary mixture fluid. We attempt to suppress the generation of natural convection, and successfully observe the heat and mass transport phenomena, which are the soret Effect and the Piston Effect, respectively. Here, we discuss these Effects observed in the supercritical artificial air.
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Numerical simulation for the Piston Effect and thermal diffusion observed in supercritical nitrogen
Cryogenics, 2004Co-Authors: Akihiro Nakano, Masao ShiraishiAbstract:Heat transport mechanism in supercritical nitrogen near the pseudo-critical line is investigated using a two-dimensional calculation model that is a rectangular cavity with a horizontal heated wall located at the top. The thermo-fluid dynamics equations are solved directly using the finite difference method. The calculation results qualitatively agree with the experimental results, which were obtained using a laser holography interferometer. It is verified that thermal energy is propagated by the Piston Effect around the pseudo-critical line.
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Application of laser holography interferometer to heat transport phenomena near the critical point of nitrogen
Cryogenics, 2001Co-Authors: Akihiro Nakano, Masao Shiraishi, Masahide MurakamiAbstract:A laser holography interferometer is applied to investigate heat transport phenomena near the critical point of nitrogen. The very high thermal compressibility and small thermal diffusion near the critical point of fluids affect thermal energy propagation, lead to the formation of weak acoustic waves as carriers of thermal energy. This heat transfer phenomenon is called the Piston Effect. The Piston Effect in supercritical nitrogen is investigated using a laser holography interferometer. Natural convection due to gravity interferes with the Piston Effect under terrestrial conditions. Therefore, we attempt to suppress the generation of natural convection by creating stable density stratification in the cell. The experiment consisted of two different procedures. In the first, heat was added from the bottom of the experimental cell, while in the second, heat is added from the top of the cell. From the two results, we successfully extracted the heat transfer phenomenon, the Piston Effect, which is considered to be the fourth mechanism of heat transfer.
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Visualization Study of Piston Effect in Supercritical Nitrogen
TEION KOGAKU (Journal of Cryogenics and Superconductivity Society of Japan), 2000Co-Authors: Akihiro Nakano, Masao Shiraishi, Masahide MurakamiAbstract:The heat transport phenomena near the critical point of fluids were investigated in this study. The very-high thermal compressibility and very-low thermal diffusivity near the critical point of fluids affect thermal energy propagation and lead to the formation of weak acoustic waves as the carrier of thermal energy. The heat transport phenomenon is called the “Piston Effect”, which is one of the thermodynamic phenomena that occur near the critical point of substances. The Piston Effect in supercritical nitrogen was investigated using a laser holography interferometer. An experimental apparatus was designed for the visualization study of the Piston Effect in supercritical nitrogen. Heat was added in step functions from a planar heater in a facedown orientation on the ceiling. The infinite-fringe method with a double-exposure technique was used in this experiment. We successfully observed a heat transport phenomenon Piston Effect, which is considered to be the 4th mechanism of heat transfer.
Sakir Amiroudine - One of the best experts on this subject based on the ideXlab platform.
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See-saw motion of thermal boundary layer under vibrations: An implication of forced Piston Effect
Physics of Fluids, 2017Co-Authors: D. Sharma, Arnaud Erriguible, Sakir AmiroudineAbstract:The phenomenon of Piston Effect is well known in supercritical fluids wherein the thermal homogenization of the bulk occurs on a very short time scale due to pressure change caused by expansion or contraction of the fluid in the thermal boundary layer. In this article, we highlight an interesting phenomenon wherein by the application of external forces (vibration) normal to the temperature gradient, see-saw motion of the thermal boundary layer is observed in weightlessness conditions. This is attributed to the thermomechanical coupling caused by the temperature change due to external forces. We term this change in the temperature field due to external forces as forced Piston Effect (FPE). A detailed investigation of this intriguing behavior shows that the see-saw motion is attributed to the variation of the relative thickness of the thermal boundary layer, defined on the basis of relative local bulk temperature, along the direction of vibration. This change in the temperature field, which is observed to be caused by FPE in vibration, is shown to depend on the compressibility (and thus proximity to the critical point), the imposed acceleration and the cell size. It is also found that see-saw motion persists in the presence of gravity and thus is described ubiquitous in nature for all conditions. A plot illustrating the maximum change in the temperature as a function of these parameters is further proposed.
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Piston-Effect-induced thermal oscillations at the Rayleigh-Bénard threshold in supercritical 3He.
Physical review letters, 2003Co-Authors: Sakir Amiroudine, Bernard ZappoliAbstract:We perform a Navier-Stokes numerical simulation of the transient Rayleigh-Benard convection onset in nearly supercritical 3He in the exact conditions in experiments performed by Kogan, Murphy, and Meyer [Phys. Rev. Lett. 82, 4635 (1999)]Phys. Rev. E 63, 056310 (2001)]]. We find an interpretation of the observed unexpected temperature oscillations at the convection onset in terms of the Piston Effect. This is our first result towards the exploration of the whole instability diagram as recently mapped in those experiments.
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Thermoacoustic heating and cooling in near-critical fluids in the presence of a thermal plume
Journal of Fluid Mechanics, 1999Co-Authors: Bernard Zappoli, Arnaud Jounet, Sakir Amiroudine, Abdelkader MojtabiAbstract:This work brings new insight to the question of heat transfer in near–critical fluids under Earth gravity conditions. The interplay between buoyant convection and thermoacoustic heat transfer (Piston Effect) is investigated in a two-dimensional non-insulated cavity containing a local heat source, to reproduce the conditions used in recent experiments. The results were obtained by means of a finite-volume numerical code solving the Navier–Stokes equations written for a low-heat-diffusing near-critical van der Waals fluid. They show that hydrodynamics greatly affects thermoacoustics in the vicinity of the upper thermostated wall, leading to a rather singular heat transfer mechanism. Heat losses through this wall govern a cooling Piston Effect. Thus, the thermal plume rising from the heat source triggers a strong enhancement of the cooling Piston Effect when it strikes the middle of the top boundary. During the spreading of the thermal plume, the cooling Piston Effect drives a rapid thermal quasi-equilibrium in the bulk fluid since it is further enhanced so as to balance the heating Piston Effect generated by the heat source. Then, homogeneous fluid heating is cancelled and the bulk temperature stops increasing. Moreover, diffusive and convective heat transfers into the bulk are very weak in such a low-heat-diffusing fluid. Thus, even though a steady state is not obtained owing to the strong and seemingly continuous instabilities present in the flow, the bulk temperature is expected to remain quasi-constant. Comparisons performed with a supercritical fluid at initial conditions further from the critical point show that this thermalization process is peculiar to near-critical fluids. Even enhanced by the thermal plume, the cooling Piston Effect does not balance the heating Piston Effect. Thus, overall Piston-Effect heating lasts much longer, while convection and diffusion progressively affect the thermal field much more significantly. Ultimately, a classical two-roll convective-diffusive structure is obtained in a perfect gas, without thermoacoustic heat transfer playing any role.
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Cancellation of the heating Piston Effect by convective enhancement of a cooling Piston Effect
International Journal of Thermophysics, 1998Co-Authors: Arnaud Jounet, Sakir Amiroudine, Abdelkader Mojtabi, Bernard ZappoliAbstract:This work brings new insight to the question of the Piston Effect, which has been found to be the main cause of temperature equilibration in the vicinity of the liquid–vapor critical point under weightlessness conditions. The thermalization process of a near-critical fluid confined in a cavity and submitted to local heating is modeled with special emphasis on the role of gravity and boundary conditions. The solution of the unsteady Navier–Stokes equations written for a hypercom-pressible low-heat-diffusing van der Waals gas is obtained in a 2-D configuration by means of a finite-volume numerical code. Under Earth gravity conditions, the results show that the thermal plume rising from a heat source strongly decreases and rapidly cancels bulk fluid heating when it strikes the top thermo-stated wall. It is proved that convection does not prevent heat transfer by the Piston Effect but that it causes a sudden enhancement of the cooling Piston Effect generated at the thermostated top boundary, which leads to an early equilibrium between the cooling and heating Piston Effects.
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Mechanisms of the onset of Rayleigh-Benard instabilities for a near critical fluid
Advances in Space Research, 1998Co-Authors: Philippe Larroudé, Sakir Amiroudine, Patrick Bontoux, Bernard ZappoliAbstract:Abstract Phenomena in near critical fluids has recently led to important theoretical and experimental results, in particular the prediction and the evidence of a mode of heat equilibration called the Piston Effect (PE). The numerical method uses a finite volume approximation based on the SIMPLER algorithm and it considers an acoustic filtering on the Piston-Effect time-scale. In the case of a Rayleigh-Benard configuration (heated from below). different types of flows are shown to develop depending on the local Rayleigh numbers and on the proximity with the critical point. The types of flows at larger Rayleigh numbers than critical, exhibit plumes at the bottom while the cooled top layer gives rise to an unstable diffusive layer.
