Modélisation et caractérisation expérimentale d'un évaporateur à mini-canaux de climatisation automobile fonctionnant au CO2

Abstract : This work deals with the use of carbon dioxide as refrigerant for automotive air conditioning systems in replacement of HFC-134a. The objective is to provide the right design of evaporators. For that, it is necessary to study the vaporization of CO2 inside minichannels and to characterize the heat and mass transfer on the air-side. CO2 vaporization is characterized by a predominant nucleate boiling, leading to high heat transfer coefficients, and an early dryout (disappearance of liquid film in contact with the wall). From experimental data found in the literature, a predictive method of heat transfer coefficient according to the vapor quality has been developed. This method combines heat transfer models of nucleate boiling, convective evaporation and post-dryout. On the air-side of the evaporator, an experimental work has been performed to study the impact of absolute humidity on the thermal-hydraulic performance of louvered fins. We noted that from a relatively low value of Reynolds number, in dehumidifying conditions, the increase in absolute humidity degrades the sensible heat transfer coefficient, while the fin efficiency remains almost unchanged. Finally, all these results allowed us to develop a numerical model of minichannels evaporator based on a fine discretization of the heat exchanger; it is a valuable tool for the design and optimization of such heat exchangers.
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Theses
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http://docnum.univ-lorraine.fr/prive/SCD_T_2007_0155_AYAD.pdf
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https://hal.univ-lorraine.fr/tel-01747015
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Submitted on : Thursday, March 29, 2018 - 10:49:33 AM
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Mohamed Fadil Ayad. Modélisation et caractérisation expérimentale d'un évaporateur à mini-canaux de climatisation automobile fonctionnant au CO2. Autre. Université Henri Poincaré - Nancy 1, 2007. Français. ⟨NNT : 2006NAN10155⟩. ⟨tel-01747015⟩

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