Investigation of current wind lobby layout on energy consumption within food supermarkets

Energy consumption due to constant opening and closing of external doors is a source of heat loss in food supermarkets. With the emphasis on energy efficiency in buildings increasing rapidly through various government's legislations and rise in energy prices, reducing heat loss through the doorways by constructing a wind lobby has become the norm. The aims of this thesis were to investigate the current wind lobby layout in supermarkets and their benefits for energy consumption through in-situ measurement, analysis and numerical modelling of a wind lobby. Measurements over one year in an operational supermarket wind lobby showed that electric energy consumption of the air curtain significantly increased from 19% of the total HVAC's electric energy consumption for the whole year to 61 % between October and January. The electric energy consumption of the air curtain was found to increase month on month in winter whilst the average temperature across the doorway decreased for the same period. Although cold snaps in winter months were detected, a correlation between the electric energy consumption of the air curtain and temperature did not exist. To estimate heat flow across a sliding doorway, a controlled experiment was undertaken in a different building without footfall to provide boundary conditions and validation for a numerical model of the wind lobby. The steady state CFD model results showed that the factors affecting the increase in heat loss were the door's opening size, indoor I outdoor temperature difference and the inlet wind speed which were the same whether the air curtain was switched off or on. This meant that the air curtain did not function as intended to contain heat in the lobby. However the air flow pattern was more complex when the air curtain was on and it dominated the air flow near the top of the doorway. A door to the back of the wind lobby was introduced in the CFD model to test cross ventilation. When the air curtain was switched on, it did not function as intended and failed to contain heat inside the lobby. When the indoor outdoor temperature difference and inlet air velocity increased, the volumetric temperature in the lobby was reduced by over 70%. Findings from the CFD model suggest that reducing the impact of the outdoor wind speed on the air curtain will reduce heat loss at the doorway. A system to shield the doors and yet allow easy access to customers such as baffles needs to be tested and assessed