Articles
PREDICTION OF PLANT SHOOT-TIP TEMPERATURE ON A PENMAN-MONTEITH MODEL
Article number
580_21
Pages
169 – 176
Language
English
Abstract
Plant temperature closely tracks ambient air temperature; however, shoot-tip temperature frequently deviates positively from air temperature under high solar radiation combined with low air velocity.
Conversely, it deviates negatively under low glazing temperatures combined with low air velocity in the winter.
These deviations indicate that climate control based on plant temperature should be better than that based on air temperature alone.
To reveal the difference between plant shoot-tip temperature and ambient temperature under any environmental conditions, a model that predicts plant shoot-tip temperature was developed.
The inputs to the model were dry-bulb, wet-bulb and glazing temperatures, shortwave radiation, and air velocity.
The model was constructed by using an energy balance equation and the Penman-Monteith model.
The input variables and shoot-tip temperature were measured in a commercial greenhouse every 10 seconds for model validation.
Simulations of shoot-tip temperature were performed under three glazing material conditions: clear glass, glass sprayed with whitewash, and glass sprayed with whitewash combined with an internal shading screen.
The simulated results agreed well with the measured shoot-tip temperatures under all glazing conditions.
We believe this model will provide a useful means of estimating plant shoot-tip temperature for climate control based on plant temperature.
Conversely, it deviates negatively under low glazing temperatures combined with low air velocity in the winter.
These deviations indicate that climate control based on plant temperature should be better than that based on air temperature alone.
To reveal the difference between plant shoot-tip temperature and ambient temperature under any environmental conditions, a model that predicts plant shoot-tip temperature was developed.
The inputs to the model were dry-bulb, wet-bulb and glazing temperatures, shortwave radiation, and air velocity.
The model was constructed by using an energy balance equation and the Penman-Monteith model.
The input variables and shoot-tip temperature were measured in a commercial greenhouse every 10 seconds for model validation.
Simulations of shoot-tip temperature were performed under three glazing material conditions: clear glass, glass sprayed with whitewash, and glass sprayed with whitewash combined with an internal shading screen.
The simulated results agreed well with the measured shoot-tip temperatures under all glazing conditions.
We believe this model will provide a useful means of estimating plant shoot-tip temperature for climate control based on plant temperature.
Authors
H. Shimizu, R.D. Heins
Keywords
shoot tip, temperature, model, energy balance
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