Underground Heat Storage And Flat Broad Irrigation Seedling System In Greenhouse

It is a considerable problem that water resources and energy consumption is too excessive in greenhouse production. In order to reduce energy consumption for greenhouse heating, increase utilizing rate of irrigation water in protected agriculture and realize purification and recycling usage of irrigation water, an underground heat storage and flat broad irrigation seedling system in greenhouse was designed based on plant physiology. The design method of every part of the system was investigated. Simultaneously, theoretic analysis and experiments were performed on the effect of energy saving and water saving of the system.(1) It was indicated from the theoretic analysis that the utilizing rate of irrigation water, transportation and precipitation of the flat broad irrigation system were 97.5%, 100%, and 67% respectively. The heat saved is more than the electric energy consumption in the heat storage system with significant heat saving effects.(2) In the experiments, parameters, including the air temperature, humidity, the soil temperature and airflow rates inlet and outlet of the heat system, were measured during heat saving and heat releasing in greenhouse. At the same time, the air enthalpy, the heat saved and the heat for heating were calculated. It was showed that the air flux was distributed equally in heat exchanging pipes and the flux of ventilator was chosen reasonably. When the hot air flowing through the exchanging pipes was cooled during heat saving in the day, the air temperature and the enthalpy were decreased 5.4~12.8℃ and 1.04~25.36kJ/kg dry air respectively and the average heat flux for heat saving is 23~81 W/m2. The superfluous heat was storied underground in the greenhouse in the day, which was more than electric energy consumption of the system. Moreover, the running time of ventilator for heat saving was less than 4.5h. At night, the cold air was heated while flowing through exchanging pipes in greenhouse, during which the air temperature and enthalpy in greenhouse increased 6.8~7.7℃ and 10.7~18.2kJ/kgd.yair respectively and heat flux for heating was 82~96W/m2, Heat saved underground in the day can be released for heating at night. Which is more than electric consumption of the ventilator, therefore the system is ascendant in the performance of heat exchanging, heat saving and heating.(3) The air temperature, humidity and the soil temperature inside and outside of greenhouse were measured in the underground heat storage system during heating in winter. It was observed that the temperature of the underground heat storage system was risen 9℃ during heat saving in the clear day and the difference between inside and outside greenhouse was 7~14℃, while the running time of ventilator should be adjusted due to effects of heat saving was limited in the overcast and rainy day. At night, the soil temperature difference between inside and outside greenhouse were 5.5~7.5℃ and 3~4℃, air temperature differences 3.5~4.5℃,2~2.5℃ inthe clear day and in the cloudy sky respectively. The system can satisfy 35% of energy consumption for heating in winter. The ventilator promotes the mixing of cold and hot air in greenhouse, so the air temperature and soil temperature were distributed equally during heat saving and heating in greenhouse.(4) During heat saving and insulation in winter, the air temperature, humidity and the seedling bed temperature inside and outside greenhouse were tested in the underground heat storage system in the double-film greenhouse. The experiment results showed that seedling bed temperature of the system with double-film was risen 12, 9.2, 5.3 and the average temperature difference between inside and outside greenhouse were 6.9, 5.4 and 5.3 during insulation at night in the clear day, cloudy sky and over cloudy sky respectively after heat storage. The performance of heat saving and insulation of the system is fine. However, the humidity in the greenhouse is high at night owing to air temperature decrease, so it is not helpful for plant growing and pre...