Abstract
In recent years, horticultural plants have frequently suffered significant heat damage due to excessive temperatures. In this study, a horticultural spray cooling system was designed, consisting mainly of a jet fan and spraying system. CFD simulation technology and response surface methodology were used to optimize the design of the jet fan, which improved the thrust of the fan. The length of the inlet section was 300 mm, the length of the outlet section was 300 mm, the length of the cone section was 450 mm, and the diameter of the outlet was 950 mm, where the thrust of the jet fan was 225.06 N. By establishing the CFD model of spray cooling in a tea field and designing a L9 (34) orthogonal experiment, the effect of the spray parameters on the maximum temperature drop and effective cooling distance was studied, and the best parameters were selected. The simulation results show that the optimum parameters are a spray flow rate of 4.5 kg/s, a droplet diameter of 15–45 μm, a droplet temperature of 298.15 K, and a nozzle double circle layout. Based on the simulation results of the optimized jet fan and spray parameters selected, a spray cooling test bench was established. Field test results show that when the initial ambient temperature was 310.05 K–310.95 K, the maximum temperature drop of the spray cooling fan was 9.1 K, and the cooling distance was approximately 36.0 m. The temperature drop decreased with increasing distance from the fan. This study is of great significance to protect horticultural plants from extremely high temperatures.
Highlights
In the context of global warming, extremely high-temperature climates occur frequently
Through patent searches and literature reviews, the authors have conducted a large number of investigations and analyses of cooling technology in the field of horticulture at home and abroad and found that the main cooling measures are traditional shading, natural ventilation, mechanical ventilation, and spray evaporation and cooling [3,4,5,6,7,8]
For extremely high-temperature climates, the effect of natural ventilation and shading is limited and not sufficient to protect the normal growth of plants [9]
Summary
In the context of global warming, extremely high-temperature climates occur frequently. For extremely high-temperature climates, the effect of natural ventilation and shading is limited and not sufficient to protect the normal growth of plants [9]. Mechanical ventilation and spray evaporative cooling are relatively effective cooling methods, but in outdoor extremely high temperature conditions, there is only one way to achieve the desired cooling effect [7], and this method remains difficult. The principle is that negative pressure is formed in the room through the fixed installation of the fan, and the external air enters the greenhouse after cooling through a wet pad, so as to achieve the effect of cooling [10,11,12]. Due Agriculture 2021, 11, 566 enters the greenhouse after cooling through a wet pad, so as to achieve the effect of coo2loinf 1g8.
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