Study On The Effect Of Reflective Thermal Screen Used In Multi-span Greenhouse

Multi-span greenhouse is an effective way to develop equipped agriculture in ourcountry for it can bring products with higher quantity and better quality, save landsignificantly and raise working efficiency. But the huge heating cost of greenhouse inwinter brings the heavy economic burden to producer and slows down the developmentspeed of greenhouse industry, so it is very urgent to enhance energy-saving techniques ingreenhouse.Reflective thermal screen can reduce the radiation and convection heat loss ofgreenhouse so much with a low emissivity and high reflectivity of its aluminized surfacethat this kind of thermal screen can save energy effectively. Moreover, Reflective thermalscreen has become an important branch of energy saving research in greenhouse since it ischeap and can be operated easily.A mathematical model of heat environment in greenhouse was developed based onenergy balance principles with the use of effective radiation method. With this model, allcomponents of heat losses in greenhouse are calculated, including radiation, convection,conduction and infiltration of cool air. The energy conserving potential of thermal screen isestimated by comparing the total heat loss of greenhouse with and without a thermalscreen.The heat-transfer coefficients of several materials with different radiometric propertieswere measured through a heat-stabilizing model box. After this measurement, aluminizedmaterial was recommended as the best energy-conserving material as thermal screen. Inaddition, the influence of aluminum amount on energy-saving efficiency of aluminizedthermal screen was determined by measuring heat transfer coefficients of screens withdifferent aluminum amount.Moreover, this thesis analyzed the practical energy saving efficiency of reflectivethermal screen and its influence on plants' environment by experiments in real greenhouse.And the experiment result was used to test the mathematical model.Reflective thermal screen will be used more widely in greenhouses for its highefficiency and economy. Finally, some suggestions were proposed about the further studyon reflective thermal screen.