Frost Prevention Measures For Red Plum And Apricot Sheds And Numerical Simulation Based On CFD

The temperature of the shed is one of the important factors that affect the growth and development of crops.Frost is one of the most important low-temperature disasters in my country.Ningxia is also a frost-prone zone.The constants and quality of crops are seriously threatened by frost disasters.Therefore,explore economic rationality and science Effective frost prevention measures have always been one of the hot spots in the field of frost prevention in orchards.Among the many anti-frost measures(such as irrigation,smoke,air disturbance,heating,etc.),the anti-frost shed increases the guidance of human factors by establishing the shed microclimate and adding heat sources,reducing the dependence on environmental factors,so it has Unique superiority.At the same time,due to the characteristics of the shed environment,the microclimate change in the shed is not completely consistent with the external environmental climate change.Therefore,this study uses four different shed heating measures,including no heating,coal-fired boiler heating,organic fume heating and diesel hot air heating,and analyzes the thermal environment in the shed under different working conditions and compares its heating Effect,establish energy consumption prediction model,and use CFD to numerically simulate the thermal environment in the shed.The results showed that:(1)The change trend of the temperature inside and outside the shed at night was basically the same.The average temperature inside the shed was 0.4 ℃ higher than that outside the shed,and the minimum temperature was 2.5℃ higher.The non-heated shed has a certain anti-frost effect,but its heating effect is poor;(2)The radiation heat exchange at night is the main method of heat exchange in the non-heated shed,and the outer surface of the covering material is radiant heat exchange without heating The main ways of heat loss in the shed;(3)The three different heating methods in the shed,namely,coal-fired boiler,organic fume,and diesel hot air blower,all have a certain heating effect,of which the hot air blower has a more obvious heating effect It can increase the average temperature in the shed by 9.7℃ and the lowest temperature of 11.2℃,followed by the organic matter heating measures in the shed,which can increase the average temperature in the shed by 2.8℃ and the lowest temperature by 3.9℃.Finally,the coal-fired boiler in the shed can be heated Increase the average temperature by 2℃,and the lowest temperature by 4.5℃;(4)According to the statistics of the lowest temperature in April of the past 26 years,the use of coal-fired boilers in the shed for heating during the night frost period of the red plum and apricot has an anti-frost effect guarantee rate of 50%.The use of organic smoke for heating during the night frost period of red plum and apricot has an anti-frost effect guarantee rate of 62%,and the use of organic smoke for heating during the night frost period of red plum and apricot has an anti-frost effect guarantee rate of 96%;(5)Based on The prediction error of the energy consumption of the hot fan heating the greenhouse established by the heat transfer mechanism of the greenhouse is within 10%,which can provide practical engineering guidance for further greenhouse energy saving and consumption reduction;(6)The simulation results and actual measurement of the three-dimensional model of the greenhouse established by CFD The results are relatively consistent,and the model is established,which can provide a basis for the simulation of the thermal environment in the shed and the optimal management of the shed under other boundary conditions;In the past 26 years,a single hot air blower heating in the shed under the extreme temperature(-13.8℃)in April of the past 26 years cannot meet the anti-frost requirements of a 60m shed,and it is necessary to add a diesel hot air blower in the shed..