נגישות
menu      
חיפוש מתקדם
תחביר
חפש...
הספר "אוצר וולקני"
אודות
תנאי שימוש
ניהול
קהילה:
אסיף מאגר המחקר החקלאי
פותח על ידי קלירמאש פתרונות בע"מ -
Effect of ceiling height on the natural ventilation of an 'Infinite' Screenhouse: Model predictions
Year:
2014
Source of publication :
Acta Horticulturae
Authors :
טייטל, מאיר
;
.
Volume :
1037
Co-Authors:
Seginer, I., Civil and Environmental Engineering Technion, Israel Institute of Technology, Haifa, Israel
Teitel, M., Agricultural Engineering, Volcani Center, Agricultural Research Organization, Bet Dagan, Israel
Facilitators :
From page:
337
To page:
344
(
Total pages:
8
)
Abstract:
Ventilation is essential to maintaining proper temperature and humidity levels in greenhouses. In small greenhouses both roof and wall openings contribute to the exchange of air, and increasing the height of such structures contributes to both forced and free ventilation processes. In particular, a higher wall reduces the resistance to flow through the structure, thus improving cross ventilation. As the area of individual greenhouses expands over the years, the contribution of ventilation through the walls diminishes and most of the exchange of heat and vapor is taking place through the roof. Here we report on a study of the expected effect of roof height of a large screenhouse on the ventilation rate. On the one hand we use a one-dimensional (vertical) computational model, based on the mixing-length concept, which at this preliminary stage covers only forced turbulent transfer. On the other hand we present preliminary measurements in two screenhouses of different heights. Both computation and measurement indicate that under windy noon-time conditions, increasing roof height by 2 m is expected to increase the indoors temperature by about 1K. The explanation for the increase in temperature is that when the exchange process is mostly by vertical turbulent transport, adding an air layer between the canopy and the roof increases the resistance to transfer and thus increases the temperature and humidity levels in the canopy layer.
Note:
Related Files :
energy balance
Mixinglength
One-dimensional profiles
Roof height
screenhouse
Ventilation
עוד תגיות
תוכן קשור
More details
DOI :
Article number:
Affiliations:
Database:
סקופוס
Publication Type:
מאמר
;
.
Language:
אנגלית
Editors' remarks:
ID:
29511
Last updated date:
02/03/2022 17:27
Creation date:
17/04/2018 00:47
Scientific Publication
Effect of ceiling height on the natural ventilation of an 'Infinite' Screenhouse: Model predictions
1037
Seginer, I., Civil and Environmental Engineering Technion, Israel Institute of Technology, Haifa, Israel
Teitel, M., Agricultural Engineering, Volcani Center, Agricultural Research Organization, Bet Dagan, Israel
Effect of ceiling height on the natural ventilation of an 'Infinite' Screenhouse: Model predictions
Ventilation is essential to maintaining proper temperature and humidity levels in greenhouses. In small greenhouses both roof and wall openings contribute to the exchange of air, and increasing the height of such structures contributes to both forced and free ventilation processes. In particular, a higher wall reduces the resistance to flow through the structure, thus improving cross ventilation. As the area of individual greenhouses expands over the years, the contribution of ventilation through the walls diminishes and most of the exchange of heat and vapor is taking place through the roof. Here we report on a study of the expected effect of roof height of a large screenhouse on the ventilation rate. On the one hand we use a one-dimensional (vertical) computational model, based on the mixing-length concept, which at this preliminary stage covers only forced turbulent transfer. On the other hand we present preliminary measurements in two screenhouses of different heights. Both computation and measurement indicate that under windy noon-time conditions, increasing roof height by 2 m is expected to increase the indoors temperature by about 1K. The explanation for the increase in temperature is that when the exchange process is mostly by vertical turbulent transport, adding an air layer between the canopy and the roof increases the resistance to transfer and thus increases the temperature and humidity levels in the canopy layer.
Scientific Publication
You may also be interested in