אסיף מאגר המחקר החקלאי

Greenhouse heating and determination of nocturnal heat loss

Year:

2006

Source of publication :

Authors :

Volume :

718

Co-Authors:

Teitel, M., Institute of Agricultural Engineering, A.R.O., Volcani Center, P.O.B. 6, Bet Dagan 50250, Israel
Barak, M., Institute of Agricultural Engineering, A.R.O., Volcani Center, P.O.B. 6, Bet Dagan 50250, Israel
Antler, A., Institute of Agricultural Engineering, A.R.O., Volcani Center, P.O.B. 6, Bet Dagan 50250, Israel

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Abstract:

Experiments were done in a heated greenhouse, in which roses were grown. The hot air was applied only during night and distributed to the crop by perforated polyethylene sleeves that were placed on the ground between the garden beds. A 20% aluminized thermal screen was automatically deployed every night between 18:00 and 06:00, at a height of about 2.5 m above the ground in order to compare the heating energy consumption and the resulting greenhouse microclimate with and without a thermal screen. The screen was used during only two of the four weeks of data collection. The air temperature in the greenhouse at night was usually maintained at 16-18°C by an on-off controller. The global heat transfer coefficient from the greenhouse was determined by two different models: the first assumed a quasi steady-state condition; the second used a transient approach in which heat storage in the greenhouse air and crop were taken into account. It is shown that there is a small difference between the results of the two models. The temperature of upper leaves at the center of the greenhouse was measured with an infrared thermometer to check the effect of the screen on leaf temperature. When the aluminized thermal screen was deployed above the plants it did not reduce the heat loss from the greenhouse but it kept the canopy temperature slightly higher than that without it.

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