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Theses

Transferts de chaleur dans un mélange constitué de fluide frigorigène et d'huile

Abstract : The phase out of chlorine containing refrigerants (CFC and HCFC) has led to the introduction of new refrigerants and lubricants to the market. The interest in using HFC fluids as working fluids in heat pumps and refrigerating systems has increased during the last decade due to their ability to replace fluids harmful to the stratospheric ozone layer. The study presents the influence of synthetic oil (POE ISO 68) on flow boiling of refrigerants R134a (pure fluid) and R410A (R32/R125 50%/50%). Local and average heat transfer coefficients and pressure drops have been measured for a smooth horizontal tube. The distribution of the heat transfer coefficient at the inner walI has been obtained from solving the inverse heat conduction problem (IHCP) and resulted in a local combination of nucleate and convective contributions to flow boiling. Local heat transfer coefficients have been averaged and displayed as a function of the vapour quality. For R134a: small amounts of oil (1 % to 6% in the liquid phase) increased the heat transfer coefficient at low and intermediate vapour qualities (Iess than 0.60) compared to pure fluid. However a hugh reduction of the heat transfer has been observed at higher vapour qualities. For R410A: oil dramatically decreases the heat transfer coefficient compared to pure fluid. Pressure drops are also affected by small amounts of lubricant: an important increase has been noted for both fluids. Available design methods for flow boiling heat transfer coefficient (superposition, enhancement, asymptotic) badly predict the experimental results. Nevertheless a new design method accounting for flow patterns has shown good agreements. The influence of the lubricant on the heat transfer is discussed and a new proposition is made to calculate pressure drops.
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http://docnum.univ-lorraine.fr/prive/SCD_T_1999_0287_MERMOND.pdf
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https://hal.univ-lorraine.fr/tel-01747262
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Submitted on : Thursday, March 29, 2018 - 10:55:58 AM
Last modification on : Wednesday, January 13, 2021 - 11:04:42 AM

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  • HAL Id : tel-01747262, version 1

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Yannick Mermond. Transferts de chaleur dans un mélange constitué de fluide frigorigène et d'huile. Autre [cond-mat.other]. Université Henri Poincaré - Nancy 1, 1999. Français. ⟨NNT : 1999NAN10287⟩. ⟨tel-01747262⟩

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