Research On Cooling Technology Of Internal Thermal Environment Of Solar Intelligent Irrigator

It is of strategic significance to develop and popularize water-saving irrigation equipment and technology for alleviating the water resources crisis and realizing the long-term and stable development of agriculture under the situation of the increasing shortage of water resources.Under the summer solar radiation,the internal air temperature of water-saving irrigation equipment operating outdoors is too high,forming a harsh thermal environment,leading to the failure of internal devices.As a result,water-saving irrigation equipment wastes water resources due to over-irrigation or crops are damaged due to drought due to lack of irrigation.Based on solar energy intelligent irrigators internal thermal environment as the research object,this paper analyzes theoretically the solar device inside heating process of thermal environment,intelligent irrigation based on thermal analysis,using COMSOL software of irrigation under the solar radiation,the temperature field of the internal thermal environment simulation,experimental study provides a reference for subsequent cooling,And completed the preparation of paraffin/expanded graphite composite phase change materials,puts forward the composite phase change material was applied to irrigation device internal cooling thermal environment experiment study,through the way of combined with silica aerogel blanket,can maintain the temperature of the internal environment within the scope of the phase change temperature,greatly improve the solar energy intelligent irrigation implement internal thermal environment,It promotes the engineering application of solar energy intelligent irrigation device,and provides a certain idea and basis for the combination of phase change temperature control technology and heat insulation technology to apply to the internal thermal environment cooling of outdoor water-saving irrigation equipment.The main contents and conclusions of this paper are as follows:Based on the thermal analysis of the internal thermal environment of the solar intelligent irrigator,the temperature field of the internal thermal environment of the irrigator under solar radiation was simulated by COMSOL software.Through the simulation calculation,the temperature cloud map of the internal thermal environment of the irrigator was obtained from 6 a.m.to 6 p.m.in a day.The simulation results show that:from 12:00 to 15:00,the internal ambient temperature of the irrigator all exceeds 50?,and the highest temperature distribution area in this period is concentrated near the inner top.The main heat source of the internal thermal environment temperature rise comes from the top,and the change of sunlight incidence direction affected the regional distribution of the maximum temperature in internal environment of the irrigator.The simulation of the temperature field provided a reference for the subsequent cooling experiments.Irrigation device in order to make the internal thermal environment air temperature to maintain under 50?,selected the NO.46 paraffin as phase change material,the use of expanded graphite for substrate,the melting mix method,respectively,the preparation of the expanded graphite content is 3%,6%,9%,12% and 15% of the composite phase change materials,by differential scanning calorimetry analysis,determination of thermal conductivity and prevent leakage test,The results show that the phase transition of the composite with 12% expanded graphite is 43.31? and 47.87?,and the latent heat of phase transition is 180.969,which still maintains a high latent heat.The higher the proportion of expanded graphite is,the greater the thermal conductivity of the composite PCM is.The thermal conductivity of the composite PCM with 12% expanded graphite is 4.801,which is about 11.8 times that of paraffin.After the leakage test,when the expanded graphite proportion is 12%,almost no leakage phenomenon occurs.A composite phase change material(PCM)with an expanded graphite ratio of 12% was selected to be used in the cooling experiment of the internal thermal environment of the irrigator.From June 26,2020 to August 12,2020,an experimental study on the cooling of the internal thermal environment of the solar intelligent irrigation device was carried out.The experimental results show that: the combined cooling method,that is,silica aerogel blanket is arranged on the top of the irrigator and the compound phase change material is filled around,has better cooling effect than the compound phase change material group and the inner top heat insulation group.During the test time,the maximum temperature of the internal air in the irrigator using the combined cooling method is 44.8?.The internal air temperature was maintained within the phase change temperature range of the composite phase change material,which was decreased by 9.2?,6.4? and 3.8? compared with the blank group,the inner top insulation group and the composite phase change material group,respectively.