## 6 Conclusions  
In this study, a novel spray hydrocooler based on TES (thermal energy storage) was developed, manufactured, and tested. A simple mathematical model was used to determine the hydrocooler parameters, including TES capacity, ice-on-coil thermal resistance, and refrigeration system. Litchi spray hydrocooling experiments were conducted at different charging times (3-6 h), spray flow rates (30-60 L min\({}^{-1}\)), and litchi loads (8-28 kg) with one-third TES capacity, and the following conclusions were drawn:  
(1) A theoretical model of direct evaporative ice storage heat transfer was established. The fruit and vegetable spray hydrocooler, designed based on ice coil thermal storage, can convert electrical energy into latent heat storage and release cooling capacity at specific times for precooling fruits and vegetables. The model was validated, and the cooling capacity target was achieved, thus proving the reliability of the heat transfer mathematical model.  
(2) The spray precooling equipment can be transported to fruit and vegetable production areas to precool freshly harvested litchi, achieving rapid precooling within 15 min after harvesting. This significantly reduces the precooling time of litchi after harvest and reduces litchi loss. The parameters of the device, including charging times, spray flow rates, and litchi loads, can be adjusted. Different charging times, spray flow rates, and litchi loads were studied to analyse the precooling capacity and precooling rate of litchi. The results showed that charging time was the most important factor influencing precooling capacity and average power consumption. Increasing the charging time effectively increased the precooling capacity and reduced the average power consumption.  
Figure 13: Variation of total power consumption and average power consumption of spray hydrocooler under different (**a**) charging times, (**b**) litchi loads, and (**c**) spray flow rates.  
(3) The optimal precooling parameters for the device in the litchi precooling process were identified. When the litchi load is 23 kg and the spray flow rate is 30 L min\({}^{-1}\), the spray hydrocooler achieves the largest precooling capacity and the smallest average power consumption in litchi spray precooling.  
Overall, the precooler provides a feasible solution for precooling litchi in small orchards. Additionally, utilizing the valley value electricity price for TES can significantly reduce operating costs. In the future, improving the energy efficiency of ice-on-coil, the utilization rate of thermal storage tanks, and the cooling uniformity of litchi can further enhance the performance of the spray hydrocooler.  
Conceptualization, H.H. and E.L.; methodology, H.H. and J.G.; validation, H.H.; formal analysis, J.G.; investigation, H.H.; resources, E.L.; writing--original draft preparation, H.H.; writing--review and editing, J.G.; supervision, E.L. and H.L.; project administration, H.H.; project administration, J.G.; funding acquisition, E.L., H.L. and J.G. All authors have read and agreed to the published version of the manuscript.  
This study was funded by the National Natural Science Foundation of China (Grant No. 31971806), the National industrial technology system of litchi and longan Program of China (Grant No. CARS-32-11), the Guangdong Provincial Agricultural Technology Innovation and Promotion Project in 2019 (Grant No. 2023 KJ101), the Research and Development and Innovation Team of Common Key Technologies for Agricultural-Product Preservation Logistics (Grant No. 2023 KJ145), and the Guangdong Province Agricultural scientific research projects and agricultural technology promotion Program (Grant No. 44000021000000086860). All of this support is gratefully acknowledged.  
The data that support the findings of this study are available from the corresponding author upon reasonable request.  
No conflict of interest exists in the submission of this manuscript.  
No. conflict of interest exists in the submission of this manuscript.