natural convection

Open joint ventilated façade (OJVF) is a passive constructive system widely used to ameliorate envelop of buildings, improving their energy efficiency. A laboratory model of a ventilated façade with horizontal and vertical open joints was used to study thermal and fluid-dynamic behaviour of this system. Experimental Stereo Particle Image Velocimetry (Stereo-PIV 2D-3C) was applied to study the fluid dynamic performance of this model. In addition, thermal analyses were performed applying infrared thermography and air temperature monitoring inside the ventilated cavity.

The paper at hand collects research findings on the impact of air flow on the thermal performance of pitched roof assemblies. Air flows in these components are typically a mixture of: 1) in/exfiltration, 2) natural convection and 3) wind-washing. In the current building practice the necessity of an air barrier to guarantee the thermal and hygric performance of roofs is well established. Yet the need for a continuous wind barrier to avoid wind-washing of the insulation layer is still often underestimated in practice.

This paper describes CFD modelling of Double Skin Façades (DSF) with venetian blinds inside the façade cavity. The 2-D modelling work investigates the coupled convective, conductive and radiative heat transfer through the DSF system. The angles of the venetian blind can be adjusted and a series of angles (0, 30, 45, 60 and 80 degrees) has been modelled. The modelling results are compared with the measurements from a section of façade tested within a solar simulator and with predictions from a component based nodal model. Agreement between the three methods is generally good.

A double population Lattice Boltzmann is used to solve the problem of the diffrentially heated cavity The use of a non-uniform grid makes it possible to validate the approach for laminar and transitional flows and (10³≤R_a≤10⁸). The results obtained, concerning the heat and mass transfers are in concordance with those of the literature. This comparison makes it possible to validate this type of approach for the prediction of anisothermal flows.

A mathematical model for simulating airflow in solar channel of the insulated Trombe solar wall system is proposed. It is assumed the glazing is isothermal and the solar heat absorbed by the wall is transferred to  the air in the channel with a constant flux by natural convection. The mass, momentum and energy  conservation equations are discretized and solved using the finite difference control volume method. An experimental study of solar chimney was used to validate the proposed mathematical model.

Recently, the requirements regarding global building airtightness to reduce the exfiltration losses became more severe as result of the trend towards very low energy buildings and Passive Houses. These very strict requirements regarding airtightness are currently achieved with an interior air barrier, which is labour intensive and consequently expensive. At the same time it is observed that new wind barrier solutions - to reduce windwashing of the insulation - can have a major contribution to the global airtightness of timber frame constructions.

The Aluminerie Alouette Inc. (AAI) smelter in northern Quebec, Canada recently completed a major plant expansion that includes a new casthouse for the continuous production of low-profile, air-cooled aluminium sows. The radiation and convection heat release of 15 MW to the workplace from the aluminium metal solidification and cooling is significantly higher than that experienced in the traditional water-cooled casting process where the majority of the heat is removed by the cooling water.

In the practical applications, roofs of buildings can be in different shapes depending onarchitectural design of building or climate. Some of these building roofs can be classified asgambrel, saltbox and gable roofs. In the present study, we investigated the natural convectionheat transfer and fluid flow inside the gambrel, gable and saltbox roofs for winter boundaryconditions. With this aim, the identified roofs are compared with each other from the heattransfer and flow field point of view.

In this study, a numerical analysis has been performed to examine the natural convection heattransfer and flow field inside a saltbox roof with eave in winter day conditions. This analysisis important for applications since it shows the effective parameters on natural convectionheat transfer. The governing equations of natural convection in streamfunction-vorticity formwere solved using central difference method to obtain flow and temperature fields inside theroof. Also, the Successive Under Relaxation (SUR) technique was used to solve linearalgebraic equations.

Unsteady natural convection in a rectangular enclosure with a vertical saturated porous wall is studiednumerically. The governing equations using Boussinesq approximation for the treatment of buoyancyterm in the momentum equation and the Darcy model are expressed using the stream functionvorticityformulation. Equations are discretized with the implicite finite-difference method. Thomasalgorithm and Gauss-Seidel method are used to solve the resultant algebraic system equations.Results are presented in terms of streamlines, isotherms and isoconcentrations.