On the effect of the dynamic contact angle of a vapor embryo interface trapped in a nucleation site

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.The effect of boiling and cavitation phenomena on nucleation was first experimentally studied. Results highlight the fact that the "classical" theory of nucleation cannot describe such a configuration. New theoretical approaches were proposed in order to describe the dynamic effects which occur when the liquid pressure oscillates over time and when a heat flux imposed to the system. It then appears that the dynamic and the hysteresis of the contact angle may play a significant role in nucleation by simultaneous boiling and cavitation effects

Control of pool boiling incipience in confined space: dynamic morphing of the wall effect

This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.A new active heat transfer enhancement and control technique is proposed in this work. One of the major aims of the technique is to decrease pool boiling incipience temperature by dynamic morphing imposed to confinement wall. Dynamic deformation generates variation of pressure which increases the fluid metastability level. An experimental device was built to evaluate boiling incipience temperature. Experimental results were compared with hydrodynamic and nucleation models.CNRS Energie CITAMPE PR09-3.1.3-2 and FNRAE SYRTIP

Pumping and heat transfer enhancement by wall's morphing

In a previous study, heat transfer enhancement using a deformable wall in a heat exchanger was demonstrated numerically using CFD calculations in liquid single-phase situation. This configuration allows the pumping function to be integrated within the heat exchanger itself. Based on these results, a prototype has been developed (but with different dimensions than in the numerical study) in which one of the walls constituting the channel is subjected to dynamic deformations in the form of a traveling wave. Electric heaters on the other wall heat the channel. Actuation is achieved by means of piezoelectric actuators. Experimentally, the pumping function is observed, for all frequencies of deformations and for two different fluids (water and HFE 7000). The heat transfer intensification is also shown, and this in two experimental configurations: - a pressure difference (which may be zero) between the inlet and outlet of the channel is imposed: in this configuration, the traveling wave imposes the flow-rate. The heat transfer enhancement is then due both to the increase of the flow-rate and the disruption of the thermal boundary layers generated by the wave; - a flow-rate is imposed with a mechanical pump: in this case actuation has no effect on the pumping, and the measured heat transfer enhancement is then due only to the effects of the imposed dynamic deformations. First experiments with the presence of boiling were also performed. It was found that boiling can occur even if the fluid does not reach the saturation temperature within the channel. A 100% increase in the mean heat transfer coefficient was found when actuating the channel wall.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016

Russia’s idea of the multipolar world order: origins and main dimensions

Contemporary international relations are rife with the ideological struggle over the potential nature of the rapidly changing world order. Two distinct paradigmatic positions have surfaced. One champions economic, cultural, and political globalization conducted under the leadership of the Western world. The other advocates a more particularistic approach that fends for a balance of interests, multiplicity of politico-cultural forms and multiple centers of international influence. The latter doctrine, often referred to as the multipolar world theory, is the subject of this paper. The discussion argues that the idea of a multipolar world order has emerged as Russia’s main ethical and ideological position advanced in the international arena. Its philosophical tenets buttress Russian society intellectually at home, providing the expedients to pursue the country’s foreign policy goals abroad. The paper examines a substantial value package with roots in both Russian and Western philosophy that sustains the multipolar world order theory

Understanding scientific study via process modeling

This paper argues that scientific studies distinguish themselves from other studies by a combination of their processes, their (knowledge) elements and the roles of these elements. This is supported by constructing a process model. An illustrative example based on Newtonian mechanics shows how scientific knowledge is structured according to the process model. To distinguish scientific studies from research and scientific research, two additional process models are built for such processes. We apply these process models: (1) to argue that scientific progress should emphasize both the process of change and the content of change; (2) to chart the major stages of scientific study development; and (3) to define “science”

About phenomenology and modeling of dropwise condensation

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Mechanisms of nucleation by simultaneous boiling and cavitation phenomena

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Heat transfer enhancement by dynamic corrugated heat exchanger wall : Numerical study

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Heat transfer enhancement by dynamic corrugated heat exchanger wall: Numerical study

International audienceA new concept of heat exchanger at sub-millimeter scale is proposed for applications in cooling on-board electronics devices, in which the quality of the exchanges between fluid and wall is very critical. In the proposed system, the upper wall of the channel is deformed dynamically to obtain a sinusoidal wave on this surface. The lower wall is exposed to constant heat flux simulating the imprint of an electronic component. A systematic 3-D numerical study in transient regime on the different deformation parameters allowed obtaining both the pumping characteristics and the heat transfer characteristics of the system. It was observed that the dynamic deformation of the wall induces a significant pumping effect. The intensification of the heat transfer is very important even for highly degraded waveforms, although the pumping efficiency is reduced in this case