Temperature performance of unsymmetrical multi-span energy-saving greenhouse in wintertime.

摘要

A new type of greenhouse named unsymmetrical multi-span energy-saving greenhouse was designed according to the climate situation of North China. This type of greenhouse was moderated scale, east-west oriented. For reducing the shading between spans the height of columns in the greenhouse was increased gradually from south to north. On the northern side there was a brick wall. In the present experiment, the temperature situation in this type of greenhouse especially during wintertime was measured by using corrected Celsius thermometers, which was shaded around the sensitive ball but opened below the ball for the natural ventilation. Hourly instantaneous temperature records from thermometers were made by trained men. The results from the measurements showed that in the north-south direction temperature distribution during night was higher in north and lower in south and changed linearly with a rate approximately 0.08-0.09 degrees C m-1, especially with a clear day before. Temperature during daytime was also higher on the north wall, and at the place of 6 and 12-14 m beyond the north wall, but it was not linear. The results identified the effect of the northern wall on the heat conservation for the greenhouse. In the east-west direction, temperature distribution had a trend of lower in east and higher in west during nighttime with a rate approximately 0.02-0.03 degrees C m-1. During daytime the difference of temperature in east-west direction was relatively small, and high temperature sometimes occurred in the middle of the greenhouse in a clear day. The temperature in the vertical direction was mainly affected by light intensity during the day and was higher with the increase in height. During nighttime, higher temperature was evident at a height of 1.5-2 m above the ground neither at the highest place nor near ground. Compared with solar greenhouse, the differences of greenhouse temperature in both horizontal and vertical direction tended to be mitigated. The distribution of temperature in the greenhouse was more even..