Passive Solar Greenhouse Heating Modeling with Watering Polyethylene Tubes نمذجة التدفئة السلبية للأنابيب البلاستيک المملوءة بالماء فى الصوب الزراعية

A simplified mathematical model based on heat, math transfer and energy balance has been developed which integrate each of solar collector (polyethylene tubes “PE” filled with water), energy storage, and the greenhouse parameters (cover material/ plants/ soil/ air). This model may be useful for understanding the extreme complexity of the heat and mass transfer that influenced by above designing parameters. The model are included temperatures for each of; air inside the greenhouse, soil surface, plant, greenhouse cover, water in PE and relative humidity. Consequently, it can be used to estimate the energy stored in the water and energy fluxes between greenhouse components. The simulation results were compared with those of the experiment depending on the bias error of main and the coefficient of determination. A good agreement was found between measured and expected values. In a greenhouse with height of cucumber plants (Cucumis Sativus l.) 2.2 m and under passive solar collector (water tubes), the minimum average of inside temperature was found in between 3–7°C higher than the outside air temperature and with about 4°C higher than control greenhouse. At January, the collection factor of solar energy for greenhouse with solar tubes increased up to 1.1 times relative to traditional. It can be decided that the current model can be used for an estimate temperatures, energy stored and energy fluxes in the greenhouse use PE filled with water. The developed thermo dynamic model can be further used for optimizing the thermal storage sizes.