Nolwenn Le Pierrès

Innovative low-energy evaporative cooling system for buildings: study of the porous evaporator wall

To face the current increase of building cooling demand and the concerns related to climate changes, an energy-efficient evaporative cooling system using porous material has been developed. This article presents the innovative cooling system and a detailed hygrothermal analysis of its main element: the porous evaporator. A mathematical model and an experimental set-up are presented, which enable to determine the suitable material properties for the evaporator and its impact on the overall cooling system performance, focusing on the optimal use of both energy and water. A good agreement is observed between numerical and experimental results, and the evaporative cooling power is estimated from 12 to 72 W/m² of evaporator wall, depending on the evaporator characteristics. A parametric analysis is conducted to select the best material for the evaporative cooling system. An intrinsic permeability of the material of 4 × 10−17 m2 is recommended for this new cooling system.

Numerical and experimental analysis of falling-film exchangers used in a LiBr–H2O interseasonal heat storage system

ABSTRACT This paper investigates heat and mass transfer occurring in an interseasonal absorption heat storage system using LiBr/H2O as the sorption couple. It focuses on the poor performances of the falling film exchangers with vertical tubes, which are characterized by low flow rate compared to conventional absorption machines. A numerical model was developed for the study and validated with specific experimental results. Comparison of the numerical model to experimental results from the heat storage prototype shows the presence of abnormally high thermal resistance between the falling films and the exchanger surfaces. The deterioration in performance appears to originate in the low wetting rate of the surfaces. A new design of the exchangers is proposed to solve this problem and thus attain the desired performance.