Browsing by Author "Chopra, Sangeeta"
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ThesisItem Open Access Design of control system for improving cooling efficiency of solar refrigerated evaporatively cooled (SREC) structure for safe storage of vegetables(DIVISION OF AGRICULTURAL ENGINEERING ICAR- INDIAN AGRICULTURAL RESEARCH INSTITUTE NEW DELHI, 2021) CHANDULAL, MONPARA MILAN; Chopra, SangeetaIndia is the world's greatest producer of fruits and the world's second-biggest producer of vegetables. Horticulture production was finally estimated at 320.77 million tonnes in 2019-20. Horticulture production is expected to reach 326.58 million tonnes in 2020- 21. Fruits and vegetables are perishable foods that degrade quickly. An estimated 30% of food produced for human use is lost or wasted owing to issues ranging from poor input usage to a lack of adequate post-harvest storage, processing, or transportation facilities. In India, up to 30% to 40% of the entire fruit and vegetable production is thrown away due to spoilage. Refrigerated storage is often considered to be the best method for preserving fresh fruits and vegetables. To maintain a pre-set room temperature, a refrigeration system typically has a coil thermistor and an air thermistor which automatically cuts off the compressor. The minimum temperature that can be achieved is 16°C, which is a pre-set temperature by the manufacturer of the refrigeration system. In order to improve the efficiency of the refrigeration system, the control system is connected to a coil thermistor and an air thermistor of the refrigeration system. The SREC structure operated on on-grid and hybrid types of inverters with a coil thermistor resistance of 45 kΩ and 39.4 kΩ and an air thermistor resistance of 21 kΩ, 18.91 kΩ and 16.94 kΩ. There were twelve treatments with a combination of inverter, coil and air thermistor resistance performed on the SREC structure. The cooling capacity was measured and a storage study of spinach and lettuce was conducted in the best storage conditions. The connection of the control system helped to lower the temperature of the SREC structure from 16℃ to 4°C. Hence, the cooling efficiency of the refrigeration system improved by 1.61 times. The highest cooling efficiency improvement of 2.29 times was found in the off-grid/ hybrid inverter with coil and air thermistor resistances of 39.4 kΩ and 21 kΩ, respectively. The secondhighest improvement almost doubled to 1.98 times in an on-grid inverter with coil and air thermistor resistances of 45 kΩ and 18.91 kΩ, respectively. The leafy vegetables were stored when the SREC structure was operated at the highest cooling efficiency. Physiological weight loss in spinach varied from 0 to 22.80% and for lettuce, it varied from 0 to 20.52% during 14 days of storage. The maximum bursting strength of the spinach and lettuce was recorded at 1.74 N and 1.73 N, respectively. The control system has proven to be very useful in enhancing the cooling performance of the SREC structure and increasing the storage life of agricultural produce. The leafy vegetables can be stored for up to 14 days and the control system with an off-grid inverter refrigeration system is very helpful for establishing cold storage at remote locations.