Articles
STUDY BY SONIC-ANEMOMETRY OF THE EFFECTS OF SURROUNDING BUILDINGS ON NATURAL VENTILATION IN A MEDITERRANEAN GREENHOUSE
Article number
927_89
Pages
715 – 722
Language
English
Abstract
Greenhouse ventilation is affected not only by the steady mean effect of air pressures and temperatures around its structure, but also by the turbulent nature of wind.
The aim of this study is to increase the available information concerning the influence of surrounding buildings on turbulence characteristics of the ventilation airflow in greenhouses.
In the side opening the airflow was mainly horizontal, while in the roof vent it was upward or downward.
The vicinity of obstacles to the greenhouse side openings reduced the incoming mean flow and increased turbulence.
Larger ventilation rates were observed for the leeward roof vent, since the wind impacts directly with the windward side opening without obstacles.
However, when the roof vent is on the windward side, the wind is partially blocked by another similar greenhouse located upwind, as the outside air enters through the roof vent and exits through the two side openings.
Natural ventilation was more effective in the experimental greenhouses, eliminating heat from the part of the greenhouse with a crop when the air entered through the side openings and came out through the roof vent; in this case the ventilation efficiency for temperature ηT was higher than 1. Higher values of turbulence intensity were observed at the opening where air enters the greenhouse.
The maximum turbulence levels were associated with low air speeds, and were observed mainly at the points located close to the side openings influenced by surrounding buildings.
The turbulent energy levels of the airflow, represented by means of the turbulent kinetic energy and the energy spectra, were higher in the windward openings without obstacles.
The aim of this study is to increase the available information concerning the influence of surrounding buildings on turbulence characteristics of the ventilation airflow in greenhouses.
In the side opening the airflow was mainly horizontal, while in the roof vent it was upward or downward.
The vicinity of obstacles to the greenhouse side openings reduced the incoming mean flow and increased turbulence.
Larger ventilation rates were observed for the leeward roof vent, since the wind impacts directly with the windward side opening without obstacles.
However, when the roof vent is on the windward side, the wind is partially blocked by another similar greenhouse located upwind, as the outside air enters through the roof vent and exits through the two side openings.
Natural ventilation was more effective in the experimental greenhouses, eliminating heat from the part of the greenhouse with a crop when the air entered through the side openings and came out through the roof vent; in this case the ventilation efficiency for temperature ηT was higher than 1. Higher values of turbulence intensity were observed at the opening where air enters the greenhouse.
The maximum turbulence levels were associated with low air speeds, and were observed mainly at the points located close to the side openings influenced by surrounding buildings.
The turbulent energy levels of the airflow, represented by means of the turbulent kinetic energy and the energy spectra, were higher in the windward openings without obstacles.
Authors
A. López, F.D. Molina-Aiz, D.L. Valera, A.J. Álvarez
Keywords
greenhouse, natural ventilation, turbulence, insect-proof screens, tri-sonic anemometry
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