23 Octobre – Thesis defense - Maria De Los Angeles Ortega Del Rosario

14 h Amphi LRL ENSAM (Esplanade des Arts et Métiers / Talence)

Customizable latent heat thermal energy storage and transfer system for air-cooling in buildings: design and thermal analysis.

The present work aims to design and study an air-PCM heat exchanger unit as a passive solution for thermal comfort assessment in buildings during summertime, providing design guidelines and easy integration to buildings. PCM present a large storage capacity per volume unit whereby, they can contribute to the reduction of the energy consumption related to cooling applications. Although, they show some drawbacks, as a low thermal conductivity in commercial PCM, so a well-thought design is necessary to achieve adequate thermal performances.
The first part of this thesis surveys the existing systems through a literature review, highlighting the geometry relation with the physics and thermal performance. This search provided the bases for the development of an air-PCM unit design, following a problem-solving methodology developed by the I2M laboratory.  A keyword matrix was obtained from the physical phenomena and functional analysis of the unit. From this matrix, the patents analysis provided inspiration for the design resulting in a tube bundle air-PCM heat exchanger with vertical tubes aligned perpendicular to the airflow. The design guidelines were achieved by following experimental and modeling approaches. Local and global experimental approaches delved into an understanding of the physics associated with charging and discharging cycles in the unit. For this, a test bench was installed, measuring temperature and airflow under different inlet conditions, accompanied by a visual tracking through digital images. Image and data processing were used to obtain thermal performance indicators and equivalent correlations using known dimensionless numbers for convective-conductive heat transfer mechanisms in the PCM. These findings allowed the development of thermal resistance and enthalpy models that accounted the complexity of phenomena involved in the unit for performance prediction. Finally, the thermal performance of the system was tested in two buildings applications: as a mobile unit in a PEH house in Gandingan and as an active façade in a building in Talence.

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