| Solar greenhouse is surrounded by roof and walls on three sides,The roof is composed by north slope and lighting roof,vegetable production is normal in no heating or a little heating conditions in winter, and it not only to promote the increase of farmer’s income, to solve the problem of supply of vegetable, but also improve the efficient use of the solar energy in winter and in spring.According to statistics,the area of China’s greenhouse up to 900,000 hm2 till 2013,and it has become a pillar industry in some areas.Solar greenhouse not only widely used in domestic northern area but also introduced to some developed countries such as Japan,Canada and carried out related research. The third generation energy-saving solar greenhouse can realize the normal production of vegetables in areas without heating with the winter’s minmum temperature above-28 ℃ so far.Color plate assembled heat Preservation greenhouse by water cycle is modern thermal storage greenhouse,it will be achieved normal production of vegetables in areas without heating with the winter’s minmum temperature above-30℃ in the future, the greenhouse will has more attention in the world. At present, the ability of environment control in most of solar greenhouse is poor, affected by the enclosure structure, the distribution research of meteorological elements in solar greenhouse is less and the research about energy budget allocation in greenhouse is not enough.Therefore, The’boundary-air’system is make up by envelope surface, soil surface and indoor air and total energy balance equation of’boundary-air’system is constructed in this article.The net energy (B) is defined as the difference of net solar radiation and envelope and soil heat fluxdifference.A new energy balance equation is composed by energy of B, enthalpy variation,heating, ventilation heat loss and condensation heat.This article construct main components model of energy balance equation, and also analyses meteorological elements distribution in order to provide a theoretical reference for improving the ability of environment control in solar greenhouse.The results are as follows:l.The shadowing effect of solar greenhouse enclosure structure on solar radiation was analyzed, the’preventing-view’s angle’of any points within solar greenhouse were calculated by using main parameters of solar greenhouse and solar azimuth. Any point which could be obtained direct solar radiation if the’preventing-view’s angle’is smaller than solar altitude. A hypothesis is that any point obtains isotropic diffuse solar radiation form the sky, diffuse solar radiation was calculated by accumulating the’non-preventing-view’s angle’.Based on these analyses, the direct solar radiation, diffuse radiation and total solar radiation at any points within solar greenhouse in sunny days were estimated.The estimated values at certain point within solar greenhouse were compared with measured values at that point, which were measured within LiaoShenⅡ type solar greenhouse, the estimated values were higher than measured values by about 6% and 9% respectively for scatter radiation and total radiation.2.Film line formed eastward or westward dip add southward dip can effect’solar altitude angle on the film’and make a complex lighting distribution in solar greenhouse.The’solar altitude angle on the film’is calculated in this paper. It shows that westward or eastward dip changed the slope, slope-exposure and solar elevation of film. Eastward dip can increase the solar elevation of righting film and increase the transmittance before 10:00am. The transmittance adheres to Logarithmic curve with’solar altitude angle on the film’, the transmittance remained a stable value at 75% ± 10% when’solar altitude angle on the film’is bigger than 45°.3.According to the heat transfer principle, the heat change between cylinder ektexine of hot-blast stove and space air were simulated for understanding the heat distribution principle during hot-blast stove heating time in greenhouse. It showed that the cylinder ektexine temperature and the exchange between cylinder ektexine of hot-blast stove and space air decreasing with unequal slope with the distance to the hot-blast stove.4.Approximate calculation method of wet enthalpy is derived by temperature and humidity in solar greenhouse. Latent heat is significantly larger than sensible heat either at nightime or daytime in winter. in spring,the same regular at nightime,but on the contrary at daytime; The value of enthalpy is fluctuated around zero at daytime and nightime in winter and at daytime in spring, but negative at nighttime in spring.5.Based energy balance the time and location model of uncovering the curtain are constructed. The earlist uncovering time is when the radiation received is the same as lossed on the cover matials. The exposing time is mainly related to the radiation and the temperature difference of inside and outside, and the time is determined by the amount of solar radiation reaching the indoor when the temperature difference is stable. Shenyang eara can be exposed to 2.5 meters first and then open up to 3.4 meters is 20min earlier than direct expose to 3.4m after sunrise.6.The value of net energy B is negative in winter night amd partial is positive during daytime; net energy value is positive during the nightime and daytime in winter and spring; The heat flux flow to the north wall and slope is smaller than greenhouse film during night in winter and spring; The heat flux flow to the film is largest in winter and flow to the soil in spring during daytime.7.The up vent is opened in winter and spring the theoretic energy balance equation of up vent ventilation is studied and wind speed is measured.lt shows that the upward vertical wind frequency is greater than the downward,and the energy to the outside is greater than from outside. By using CFD method,the wind speed and wind directions are simulated, the flow enters the greenhouse form up vent, arrive at the bottom of the greenhouse and divided into 2 two vortices.The maximum relative wind speed is near the up vent, the minimum of wind speed is in the canopy.8.At night-time in winter,the air temperature of the side which was near the hot-blast stove was higher obviously than that in the other side, air temperature at upside was higher than that at bottom in the same section.The difference of temperature between five sections is about 3 ℃-4℃,and the difference is about 2℃-5 ℃ in the same section. But on the conditions of none heating,the difference of temperature is 1℃-2 ℃ in the same section.9. The largest humidity is at upper part and 5%～10% in different part in the same section... |
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