Dynamic thermal modeling of a commercial greenhouse in Quebec with a new TRNSYS type to estimate evapotranspiration

Abstract: This paper proposes a dynamic thermal model for a commercial greenhouse in Quebec, Canada, used for tomato cultivation. The study aims to improve the accuracy and efficiency of greenhouse simulations by considering the impact of plants' complex internal gains on the sensible and latent loads of the greenhouse. A new TRNSYS type is developed to account for latent and sensible gains/losses from evapotranspiration and evapotranspiration rates. A co-simulation approach is employed between TRNSYS for transient energy simulations and CONTAM for airflow rate calculations. One span out of eight is modeled. The span is 121.9 × 7.6 m² and 6.7 meters high. The model is able to estimate indoor temperature and relative humidity and the evapotranspiration rate. The evapotranspiration rates obtained in this study are consistent with those reported in the literature.Communication présentée lors du congrès international tenu conjointement par Canadian Society for Mechanical Engineering (CSME) et Computational Fluid Dynamics Society of Canada (CFD Canada), à l’Université de Sherbrooke (Québec), du 28 au 31 mai 2023

Étude de l'écoulement et de l'instabilité de Dean dans les conduites à section rectangulaire

Nous présentons un travail expérimental et numérique dans le but d'étudier l'écoulement laminaire et l'instabilité de Dean dans les conduites courbes à 180, de section rectangulaire, lors du passage de fluides newtonien et non-newtoniens. L'étude concerne l'effet des paramètres géométriques et rhéologiques sur l'apparition et le développement de l'instabilité de Dean. L'étude numérique est rendue possible par l'intégration d'un sous programme, qui tient compte du comportement rhéologique des fluides à seuil, dans le code de calcul Fluent. Des visualisations expérimentales et numériques de l'écoulement ont été effectuées dans le cas de fluides newtonien, pseudoplastique et à seuil. Nous avons développé un critère précis pour la détection du début de l'instabilité, basé sur le gradient de vitesse axiale, applicable expérimentalement et numériquement. La précision de ce critère permet de déterminer des nombres de Dean critiques faibles comparés à ceux trouvés dans la littérature qui sont basés sur des critères qualitatifs de visualisations.We present an experimental and numerical work on Dean instability in Newtonian and non-Newtonian fluids in laminar flow inside 180 curved channels, of rectangular cross-section. The study concerns the effects of the geometrical and the rheological behavior parameters on the appearance and development of Dean instability. The numerical study was carried out by integrating in Fluent CFD code a subroutine to take into account the rheological behavior of a yield fluid. Experimental and numerical visualizations of the flow have been carried out in the case of Newtonian, pseudoplastic and yield fluids. An accurate criterion, based on the axial velocity gradient, was defined that allows detection of the instability threshold experimentally and numerically. Prediction of the critical Dean number by this criterion lets us to detect the instability closer to its onset than in previous work based on the qualitative criterions of visualization.NANTES-BU Sciences (441092104) / SudocNANTES-Ecole Centrale (441092306) / SudocSudocFranceF

Frost formation over a cold plate with icephobic coatings

Abstract: In this study, a new experimental set-up has been developed to investigate by flow visualizations the frost formation and growth on a cold plate. Seven environmental conditions, varying the air temperature, relative humidity, and velocity and the plate temperature, are considered. For the uncoated plate, the experimental data on the temporal evolution of the frost layer thickness enable to validate a pseudo 1D model formerly developed. Three bioinspired icephobic surfaces including superhydrophobic, SLIPS and self-lubricant coatings are then compared to the base case without coating for five environmental conditions. Superhydrophobic coating provides the highest retardation time for the formation and growth of frost compared to the SLIPS and self-lubricant coatings whatever the environmental conditions. It appears as a valuable way to delay the formation of frost and improve the performance of refrigeration systems based on eutectic plates, used for the transport of food products.Communication présentée lors du congrès international tenu conjointement par Canadian Society for Mechanical Engineering (CSME) et Computational Fluid Dynamics Society of Canada (CFD Canada), à l’Université de Sherbrooke (Québec), du 28 au 31 mai 2023

A review of Stall Delay Models and their Application on Hybrid Methods

This paper is a review on the stall delay phenomenon that Horizontal Axis Wind Turbines (HAWT) encounter under typical flow conditions and its numerical modelling.  Aerodynamic performance predictions of HAWT have been often carried out through Computational Fluid Dynamics method with the combination of the concept of actuator disk  i.e. hybrid method. For this purpose, the hybrid method is presented in details together with the   numerical modelling  of such stall delay phenomenon. Despite modern wind turbines are equipped with sophisticated control systems for  avoiding stall, nevertheless, stall is still inevitable in the near root region of the rotor blade. This paper focuses on recent research development materials which have been undertaken on the stall delay phenomenon where the engineering models (stall delay models) of the literature being presented and criticized based on the predictions obtained from the NREL Phase VI wind turbine experiments

“Parametric study on the age of air in a full-scale office room using perforated duct diffusers.”

Following the recent pandemic of COVID-19, scientists have made many efforts to devise a workable solution for it, worldwide. However, it was shown that the protective effect of a well-conditioning system is as high as five times in comparison to the face-covering and other proposed procedures. In this context, the age of air and the type of filtration systems in closed spaces became the critical criteria for comparing the capability of ventilation systems. In this paper, a validated numerical model for the perforated duct diffusers is used to study the behaviour of the local age of air at the full-scale office with 8 feet (2.44 [m]) height, under various initial conditions like initial velocity and air change per hour. Also, different geometries for the ducts have been investigated under the same initial condition, as well as the effect of direction, ventilation effectiveness, and flow pattern. Finally, the volume average of the age of air at different zones has been nominated to perform the sensitivity analysis of each variable based on the variation of the airflow. The results show that diffusers with vertical perforations would be more effective during the pandemic than the other types in airborne mitigation. Moreover, the highest available airflow shall be set until such time there is no windy area in the breathing zone. Within these modifications, the residence time of the infectious nuclei in the breathing zone may decrease by up to 30%

Design and Optimization of a Double-intake and Rotor Squirrel Cage Fan Using OpenFoam and Metamodels

The range hood is crucial in kitchens during cooking activities. Inside the residential houses, cooking activities are one of the main sources of particle emission, which decreases the air quality level. Furthermore, multiple studies found a strong correlation between the particles emitted from cooking activity and chronic obstructive pulmonary disease (COPD), lung cancer and diabetes. The use of an efficient range hood is essential to maintain a healthy air quality level inside the house. The fan is the main component inside a range hood. Most of the range hoods are equipped with an axial fan or a one rotor squirrel cage fan. In the present study, a powerful double-intake and rotor squirrel cage fan is designed and optimized by using a developed optimization process loop based only on open source libraries. Dakota is used to achieve the sampling and build the surrogate surfaces, Salome to generate the geometry and the mesh grid and OpenFoam for the calculations. More than eleven design parameters are selected in the impellers, blades and volute regions. The two objective functions: total efficiency and the generated noise are improved by maximizing and minimizing their values, respectively. The Latin Hypercube Sampling (LHS) method is selected to achieve sampling over more than 363 design parameters set. In order to model the turbulent flow, a 3D incompressible simpleFoam solver is used and coupled to the Multiple Reference Frame (MRF) approach. The Kriging and the quadratic polynomial response surface are used to expand the design space and improve the objective functions. The total efficiency is improved by 12 % and the noise is reduced by 2 sones compared to the initial design. The Kriging Metamodel predicts with less than 2 % the total efficiency and 1% the generated noise compared to the OpenFoam calculation. A large 3D coherent structure is observed in the volute region with a scattered turbulent region near the outlet. The optimal design is validated at the design point against the produced prototype, with an error of 2.8 % and 1.3 % on the total efficiency and generated noise, respectively