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Modelling and experimemental study of frost formation and development on a cold plane plate.

Étude expérimentale et modélisation de la formation et du développement du givre sur une plaque refroidie.

Author(s) : LEONI A., HABERSCHILL P., REVELLIN R.

Type of monograph: Thesis

Summary

In the energy consumption and environmental impact reduction goal, heat pumps emerged as an alternative to fossil fuel systems for space heating and hot water production in residential and tertiary sectors. Manufacturers still try to improve energy performance of heat pumps. However, a non-controlled phenomenon is limiting progress: frosting. Indeed, in some outdoor air
temperature and relative humidity conditions, frost can form on the heat pump evaporator surface, leading to performance reduction. On the French market, almost 98 % of the heat pumps are using outdoor air as heat source and are thus affected. Despite more and more sophisticated defrosting strategies, the frosting/defrosting cyclic operation strongly reduces heat pump performance. For optimizing defrosting strategies, there is a need understanding frost appearance and growth mechanisms. This PhD work thus proposes to study frost formation and development on a cold plane plate. An in-depth bibliography study helped establishing databases gathering experimental points on frost thickness and frost density. Models and correlations of frost formation available in the literature have been reproduced and applied to the databases in order to evaluate their prediction capacity. The most performing models have been identified. Meanwhile, an experimental bench allowing visualization of frost formation and development on a cold plane plate has been set up. The sensitivity analysis on air temperature, cold plate temperature, air velocity and relative humidity allowed an evaluation of these parameters impact on frost formation, and more particularly on three of its properties: thickness, density and thermal conductivity. Relative humidity and cold plate temperature have been identified as the leading parameters. One of the main results of this work was to highlight the frost crystal structure role on properties (i.e. density and thermal conductivity). Experimental data points obtained with the test bench have been compared to the results provided by literature models. Predictive methods identified as satisfying in the bibliography study gave similar results (from a statistical point of view). Perspectives for future work have also been proposed.

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  • Original title: Étude expérimentale et modélisation de la formation et du développement du givre sur une plaque refroidie.
  • Record ID : 30021294
  • Languages: French
  • Publication: Insa - lyon (institut national des sciences appliquées de lyon) - France/France
  • Publication date: 2017/02/17

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