Study Of Dynamic Cooling Load Characteristics And Temperature Prediction In Apple Cold Room

With environmental problems and energy crisis increasing seriously,energy conservation and emission reduction have become an important trend in the cold storage.Unscientific management of cold room throughout the year leads to unnecessary energy consumption.Cooling load is the basis for studying the energy consumption.Temperature is one of the important factors affecting the quality of fruits and vegetables.Studying the dynamic cooling load and predicting the temperature in the cold room are valuable in good design and efficient maintenance of cold storages to reduce energy consumption and improving the storage quality of fruits.A cold room filled with 230 t apples in Xi'an is taken as the research subject.According to the actual operation management of the cold room,the dynamic cold load model and the temperature prediction model are established to study the dynamic cold load and changes of temperature in the cold room.The main work and research results are as follows:According to the actual operation of the cold room,the calculation model of annual dynamic cooling load has been established to analyze the variation of cooling load.The research results show that the cold load of the cargo is the major cold load in the whole year.During loading period,the cooling load of cargo accounts for 53% to 70% of the design load at the cargo initial temperature of 15? and daily input 10% of the stored capacity,For the normal storing period,the cooling load of cargo accounts for 52% to 86%.The annual load rate is concentrated in the range of 10% to 20% and the time frequency is 63.6%.It can be seen that,except for the loading period,the refrigeration equipment is in low-load operation for fruits and vegetables cold room throughout the year.According to the first law of thermodynamics,the temperature prediction model of cargo and the air in the warehouse are established.And the influence of wind speed,initial temperature and loading quantity were carefully studied on apple cooling rate for the first batch of cargo entered.The results show that the apple cooling rate is greatly affected by the cargo wind speed and initial temperature.The higher the wind speed,the faster the apple cools down.At the wind speed of 0.3 m/s,the cooling time was 116 h,which increased by 1.03 times and 2.41 times respectively compared with the wind speed of 0.5 m/s and 1m/s.The cooling time is 194 h at the temperature of 15?,which is 2.46 times longer than the cooling time of 4?.The cooling time for the cargo quantity of 20% is 72.1% longer than that of 5%.However,the amount of the cargo affects the selection of the refrigeration equipment.Therefore,the cargo should be put into storage in small quantity after pre-cooled to ensure the quality of fruits and vegetables.Based on the apple temperature model,the influence of storage temperature,outdoor temperature and cargo quantity on the operation of the cooling fan were studied during the normal storing period.Under the requirements of apple storage temperature,the higher storage temperature cause the longer running time of the cooling fan.Outdoor temperature has little effect on the running time of the cooling fan.At the storage temperature of 2? and the temperature fluctuation of ± 0.1 ?,the outdoor temperature increased from 1.3? to 14.7?,and the average operating hours of cooling fan increased by 26.3% in a day.When the storage quantity increased from 30% to 100%,the running time is increased by 33.2%.