Chauffage, ventilation et climatisation

thumb|Un système de refroidissement. Le chauffage, ventilation et climatisation (en abrégé CVC), équivalent en France de l'anglais (en abrégé HVAC, diffusé mondialement) est un ensemble de domaines techniques regroupant les corps d'état traitant du confort aéraulique. Ce qualificatif s'applique à tous types de bâtiments (habitat, tertiaire, industriel) et de véhicules. Il regroupe les spécialités et spécialistes du chauffage, de la ventilation et de la climatisation. On trouve également, en particulier au Québec, la locution chauffage, ventilation et conditionnement d'air, abrégé en CVCA. Objectifs Le but d'un système de CVC est d'assurer aux usagers des conditions d'hygiène et de sécurité respectant la réglementation en vigueur, ainsi qu'un certain niveau de confort. Les sciences et les techniques mobilisées pour la conception et la réalisation d'un système de CVC permettent de maîtriser dans un bâtiment :

le niveau d'hygiène (, polluants, particules, odeurs) ;
le ni

District energy network potentials in a city territory

Raphaël Briguet

Following the Covid crisis and the war in Ukraine, the rise of fossil fuels prices demonstrates the insecurity of the supply in addition to the adverse impact it has on the environment. These crises could lead to a global shift in the strategy of building heating. Renewable systems are promising alternatives to fossil fuel heating system. One of them is the District Heating Network that has the advantages of recovering the waste heat from the industry. In the context of a neutral carbon objective set by the aluminium factory Novelis, the city of Sierre is interested in investigating the possibility of develop- ing a District Heating Network (DHN). This study develops a method to design a network between a heat source and a city, based only on open data building’s inventory. The method, applied to the case study of Sierre, shows that, coupled with heat pumps, the DHN could reduce the heating emissions of the connected buildings, between 88% and 96 % and that 50% of the Novelis’ heat is recovered when half of the city is connected to the network. In addition to that, using new generation of DHN, like CO2 based network makes possible to supply cold with the same infrastructure.

2022

Impact of the ventilated air-space behind traditional (passive) and BIPV (active) façades on the thermo-hydrodynamic performance of the building wall structures

Mohammad Rahiminejad

For many decades, ventilated cavities in wall assemblies of buildings have been essential for creating moisture-resilient constructions by allowing airflow within the air gap to promote drying. In addition to that, the airflow in the cavity can contribute to the overall performance of the wall structure. Similar to the wall assemblies with traditional claddings, photovoltaic (PV) panels in the Building-integrated photovoltaic (BIPV) façades can be separated from the building envelope by an air gap that is created for ventilation purposes. In this study, the impact of the thermo-hydrodynamic behavior of the airflow in the naturally ventilated cavity behind traditional (passive) and BIPV (active) façades on the performance of the entire wall assembly is numerically and experimentally investigated. Due to the complexity of the problem caused by the contribution of several parameters, as a first step, a comprehensive literature review is performed to specify the effective factors on the air change rate in the ventilated cavity behind common wall assemblies. As the second step, the steady-state analysis is carried out within the framework of a research project ASHRAE 1759-RP funded by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), in which the plausible definitions of the thermal resistance of a vertical ventilated air-space behind external cladding systems are defined using theoretical and applied formulations. Moreover, based on the uncertainty analysis of measurements, the modifications of the relevant standardized method (ASTM C1363-19) to account for the airflow effects on the thermal performance of the wall assembly are proposed. In the third step, the problem is further explored in the transient conditions by developing a 2D numerical in-house code validated against experimental measurements. Accordingly, the performance of wall structures with different thermal inertia having passive (traditional) and active (BIPV) external claddings are numerically investigated. In the last step of this thesis, the problem is experimentally discovered, and the thermo-hydrodynamic performance of ventilated wall structures of the test facility is investigated using data collected during a full-year measuring campaign. The results of this study show that the thermo-hydrodynamic behavior of the airflow behind external claddings is a complex phenomenon. The results of the steady-state analysis reveal that, under some conditions, the air-space could be able to resist the heat flux passing the wall assembly even more than the external cladding. Moreover, the uncertainty analysis sheds light on the fact that accurate instruments are needed to reduce the uncertainty of measuring the thermal resistance of the cavity. The results of the transient numerical analysis show that the overall performance of a ventilated wall structure dynamically changes depending on the diurnal variation of the outdoor/indoor conditions. Moreover, it is shown that replacing the passive cladding with an active façade could strongly affect the hydrodynamic and thermal performances of the entire wall assembly. The results of the experimental measurements pointed out that the airflow in the ventilated cavity has a major impact on the yearly performance of a wall structure; therefore, further investigations are required in future studies to evaluate the possibility of controlling the air change rate in the cavity using a fan-assisted system.

EPFL2022

Impact of the ventilated air-space behind traditional (passive) and BIPV (active) façades on the thermo-hydrodynamic performance of the building wall structures

Mohammad Rahiminejad

EPFL2022

Chauffage, ventilation et climatisation

District energy network potentials in a city territory

Impact of the ventilated air-space behind traditional (passive) and BIPV (active) façades on the thermo-hydrodynamic performance of the building wall structures

Universal Dynamics of Kerr-Frequency Comb Formation in Microresonators

District energy network potentials in a city territory

Impact of the ventilated air-space behind traditional (passive) and BIPV (active) façades on the thermo-hydrodynamic performance of the building wall structures

Universal Dynamics of Kerr-Frequency Comb Formation in Microresonators