การศึกษาการถ่ายเทความร้อนในดินเพาะกล้าไม้โดยใช้น้ำร้อนที่ได้จากพลังงานรังสีอาทิตย์

Abstract

The objective of this research was to study heat transfer in fertile soil for seedlings using solar energy to heat water for curbing the growth of microorganisms in soil and cultivate seedlings. The efficiency of various solar collectors including an asymmetric compound parabolic concentrator, a heat pipe evacuated tube solar collector, and a flat plate solar collector were determined. Then, the solar collectors were connected in a series circuit to create hot water system. Four arranged patterns of solar collectors were studied. The pattern that could produce the highest water temperature was used to drip hot water into the soil to study heat transfer in the seedling soil. The results showed that the efficiency of the asymmetric compound parabolic concentrator, the heat pipe evacuated tube solar collector, and the flat plate solar collector were 79.45%, 72.25%, and 21.53%, respectively. When the three solar collectors were connected in a series circuit and produced hot water from solar energy system, the ambient temperature was heated with a large asymmetric compound concentrator to increase the water temperature. The heated water was put into a flat plate solar collector that placed between a large and a small asymmetric compound concentrator to receive solar energy. Then, the water produced with the flat plate solar collector was put into the heat pipe and evacuated tube solar collector to increase the water temperature. It was found that the last pattern could produce hot water of 100 oC at the flow rate of 0.004 kg/s with solar radiation of 991 W/m2. As the result, the temperature of the fertile soil for seedlings could rise at the depth level of 0, 5, 10, 15, 20, 25, and 30 cm, respectively. The water temperature was at 75.5 oC, 75.3 oC, 75.1 oC, 74.9 oC, 74.7 oC, 74.5 oC, and 74.1 oC, respectively. The rise of water temperature could curb R. solanacearum which caused the plant diseases.