Natural Ventilation Efficacy Study for a Refurbished public Market

In this study the efficacy of natural ventilation through the existing openings in a refurbished market is checked. The openings are 7 doors in the ground level, along with 2 layers of windows in the 1st level of the market and openings below the skylight of the market ceiling (figure 1). In the ground level there are shops (flea market style), while in the 1st level there are restaurants and coffee shops. The symmetry plane (x-z plane) is in a 33o angle to the north direction.

Market's geometry

Market's openings

The market’s corridors are assumed to be occupied with 2.5 people/m2 corresponding to a cooling load of 180W/m2. In the shops/restaurants the cooling load is assumed to be 80W/m2 because of the existing people and the equipment operation. Additionally, in all other surfaces either a cooling load is applied or they are assumed to be adiabatic. The cooling loads are gathered in table 1. Regarding the openings the flow direction is not known before the simulation but it is left to develop. The ambient temperature is 30oC.

The problem is simulated by using CFD techniques for 3D, incompressible, unsteady, turbulent flows and taking into account heat transfer phenomena in the air.

Cooling loads (W/m2)

Skylight (200)

Closed Windows (20)

Closed Wind. 1st level (40)

Closed Wind. 2nd level (60)

External Walls (4)

Ceilings (10)

Walkable areas (180)

Shops/Restaurants (80)

Other adiabatic walls (0)

Numerical Methodology

Estimation of spatial and temporal discretization

Unsteady Navier-Stokes equations along with the Radiative Transfer Equation

k-ω SST URANS turbulence model

Opening boundary conditions at all openings

Results independence study

Spatial Discretization

The numerical mesh composed of tetrahedral elements (161800 nodes, 947669 cells) of a mean size of 20-30cm.

Surface numerical mesh

Results

The estimated fresh air inflow rate is equivalent to at least 7,1 Air Changes per Hour (ACH) that is deemed sufficient for the natural ventilation of the market without any additional mechanical ventilation installation.

Temperature field in the symmetry plane

Temperature field in the y-z mid-plane

Surface temperature

Velocity magnitude at openings

Closed space natural ventilation (absolute moisture field)

Closed space natural ventilation 1 (temperature field)

Closed space natural ventilation 2 (temperature field)