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Title: The use of processes evaporation and condensation to provide a suitable operating environment of systems

Abstract

All electronic components which exhibit electrical conductor resistance, generates heat when electricity is passed (Joule - Lenz’s Law). The generated heat is necessary to take into surrounding environment. To reduce the operating temperature of electronic components are used various types of cooling in electronic devices. The released heat is removed from the outside of the device in several ways, either alone or in combination. Intensification of cooling electronic components is in the use of heat transfer through phase changes. From the structural point of view it is important to create a cooling system which would be able to drain the waste heat converter for each mode of operation device. Another important criterion is the reliability of the cooling, and it is appropriate to choose cooling system, which would not contain moving elements. In this article, the issue tackled by the phase change in the heat pipe.

Authors:
 [1]; ;  [2]
  1. University of Žilina, Research centre, Univerzitná 8215/1, 010 26 Žilina (Slovakia)
  2. University of Žilina, Faculty of Mechanical Engineering, Department of Power Engineering, Univerzitná 8215/1, 010 26 Žilina (Slovakia)
Publication Date:
OSTI Identifier:
22608631
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1745; Journal Issue: 1; Conference: 20. International scientific conference on the application of experimental and numerical methods in fluid mechanics and energy 2016, Terchova (Slovakia), 27-29 Apr 2016; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; COMPUTERIZED SIMULATION; COOLING SYSTEMS; ELECTRIC CONDUCTIVITY; ELECTRICITY; ELECTRONIC EQUIPMENT; HEAT TRANSFER; WASTE HEAT

Citation Formats

Kolková, Zuzana, E-mail: zuzana.kolkova@rc.uniza.sk, Holubčík, Michal, E-mail: michal.holubcik@fstroj.uniza.sk, and Malcho, Milan, E-mail: milan.malcho@fstroj.uniza.sk. The use of processes evaporation and condensation to provide a suitable operating environment of systems. United States: N. p., 2016. Web. doi:10.1063/1.4953718.
Kolková, Zuzana, E-mail: zuzana.kolkova@rc.uniza.sk, Holubčík, Michal, E-mail: michal.holubcik@fstroj.uniza.sk, & Malcho, Milan, E-mail: milan.malcho@fstroj.uniza.sk. The use of processes evaporation and condensation to provide a suitable operating environment of systems. United States. doi:10.1063/1.4953718.
Kolková, Zuzana, E-mail: zuzana.kolkova@rc.uniza.sk, Holubčík, Michal, E-mail: michal.holubcik@fstroj.uniza.sk, and Malcho, Milan, E-mail: milan.malcho@fstroj.uniza.sk. 2016. "The use of processes evaporation and condensation to provide a suitable operating environment of systems". United States. doi:10.1063/1.4953718.
@article{osti_22608631,
title = {The use of processes evaporation and condensation to provide a suitable operating environment of systems},
author = {Kolková, Zuzana, E-mail: zuzana.kolkova@rc.uniza.sk and Holubčík, Michal, E-mail: michal.holubcik@fstroj.uniza.sk and Malcho, Milan, E-mail: milan.malcho@fstroj.uniza.sk},
abstractNote = {All electronic components which exhibit electrical conductor resistance, generates heat when electricity is passed (Joule - Lenz’s Law). The generated heat is necessary to take into surrounding environment. To reduce the operating temperature of electronic components are used various types of cooling in electronic devices. The released heat is removed from the outside of the device in several ways, either alone or in combination. Intensification of cooling electronic components is in the use of heat transfer through phase changes. From the structural point of view it is important to create a cooling system which would be able to drain the waste heat converter for each mode of operation device. Another important criterion is the reliability of the cooling, and it is appropriate to choose cooling system, which would not contain moving elements. In this article, the issue tackled by the phase change in the heat pipe.},
doi = {10.1063/1.4953718},
journal = {AIP Conference Proceedings},
number = 1,
volume = 1745,
place = {United States},
year = 2016,
month = 6
}
  • Heat transfer data are presented for direct-contact evaporator and condenser geometries suitable for Open-Cycle Ocean Thermal Energy Conversion (OCOTEC) applications. Falling turbulent jets and films were tested at typical operating conditions. The flash evaporator performance was relatively constant over the range of conditions tested, with efficiencies as high as 95 percent due to the breakup of the jets (or films) into sprays. The condenser performance was only affected by the jet or film Reynolds number and the steam air content. Condenser heat transfer coefficients of the order of 27 kW/m/sup 20/C were achieved with jets which were higher than thosemore » obtained with films. An empirical correlation was developed for the condenser data after it was shown that none of the existing correlations found in the literature could correlate all of the data trends observed.« less
  • A recent criterion for shock waves which predicts the behaviors of the internal energy across the shock is extended to a vapor between two interfaces. We look at the predictions of monotonic or not behavior and at the possible inversion of the internal energy inside the gas. We consider different discrete Boltzmann models, construct new classes of exact solutions (models with a rest particle and models leading to 3{times}3 Riccati systems), and verify the criteria predictions. {copyright} {ital 1996 American Institute of Physics.}
  • The evaporation/condensation coefficient (β) and the evaporation rate (γ) for n-dodecane vs. temperature, gas pressure, gas and liquid density, and solvation effects at a droplet surface are analysed using quantum chemical density functional theory calculations of several ensembles of conformers of n-dodecane molecules in the gas phase (hybrid functional ωB97X-D with the cc-pVTZ and cc-pVDZ basis sets) and in liquid phase (solvation method: SMD/ωB97X-D). It is shown that β depends more strongly on a number of neighbouring molecules interacting with an evaporating molecule at a droplet surface (this number is estimated through changes in the surface Gibbs free energy ofmore » solvation) than on pressure in the gas phase or conformerisation and cross-conformerisation of molecules in both phases. Thus, temperature and the surrounding effects at droplet surfaces are the dominant factors affecting the values of β for n-dodecane molecules. These values are shown to be similar (at reduced temperatures T/T{sub c} < 0.8) or slightly larger (at T/T{sub c} > 0.8) than the values of β calculated by the molecular dynamics force fields (MD FF) methods. This endorses the reliability of the previously developed classical approach to estimation of β by the MD FF methods, except at temperatures close to the critical temperature.« less
  • The authors consider a mixture of heavy vapor molecules and a light carrier gas surrounding a liquid droplet. The vapor is described by a variant of the Klein-Kramers equation; the gas is described by the Navier-Stokes equations; the droplet acts as a heat source due to the released heat of condensation. The exchange of momentum and energy between the constituents of the mixture is taken into account by force terms in the kinetic equation and source terms in the Navier-Stokes equations. These are chosen to obtain maximal agreement with the irreversible thermodynamics of a gas mixture. The structure of themore » kinetic boundary layer around the sphere is determined from the self-consistent solution of this set of coupled equations with appropriate boundary conditions at the surface of the sphere. The kinetic equation is rewritten as a set of coupled moment equations. A complete set of solutions of these moment equations is constructed by numerical integration inward from the region far away from the droplet, where the background inhomogeneities are small. A technique developed earlier is used to deal with the numerical instability of the moment equations. The solutions obtained for given temperature and pressure profiles in the gas are then combined linearly such that they obey the boundary conditions at the droplet surface; from this solution source terms for the Navier-Stokes equation of the gas are constructed and used to determine improved temperature and pressure profiles for the background gas. For not too large temperature differneces between the droplet and the gas at infinity, self-consistency is reached after a few iterations. The method is applied to the condensation of droplets from a supersaturated vapor as well as to strong evaporation of droplets under the influence of an external heat source, where corrections of up to 40% are obtained.« less