Research On The Operation Strategy Of Natural Cold Source Food Refrigerated Display Cabinet And The Temperature Response Of Stored Food

In order to solve the problem of high energy consumption of refrigerated display cabinets,the operation characteristics of natural cold source refrigerated display cabinets are studied by means of experiment and theoretical analysis,and the design method and operation strategy of energy storage natural cold source display cabinets are discussed.In view of the large temperature fluctuation in the refrigerated display cabinet,the theoretical and numerical research is carried out,and the periodic pulse function equation method is used to establish the instantaneous temperature change model including the temperature fluctuation characteristics of frosting and defrosting.The law of air curtain and food temperature change of refrigerated display cabinet caused by periodic defrosting and start-up and shutdown was tested and simulated.The specific research contents and results are as follows:1.The natural cold source refrigerated display cabinet system is designed,and the operation strategy of the natural cold source refrigerated display cabinet system under the four typical design days of the Spring Equinox,the Summer Solstice,the Autumn Equinox and the Winter Solstice is analyzed.The results show that under different operation modes,the temperature of food in the refrigerated display cabinet can be maintained between-1 ℃ and7 ℃,which can meet the requirements of food refrigeration.The energy consumption of the designed natural cold source food refrigerated display cabinet in the four typical design days of the Spring Equinox,the Summer Solstice,the Autumn Equinox and the Winter Solstice decreased by 24.79%,33.40%,35.46% and 16.67% respectively compared with the traditional refrigerated display cabinet system.2.The simulation process of the natural cold source refrigerated display cabinet system was established,and the annual energy consumption was used as the assessment index to optimize the operation of the natural cold source food refrigerated display cabinet system.The optimization results show that when the air supply temperature of the refrigerated display cabinet is-1.5C and the cooling temperature of the refrigerant is-3 ℃,the energy consumption of the system is the lowest,which is 40.8% lower than that of the traditional food refrigerated display cabinet system.The total operating time of the natural cold source cold storage and cooling mode alone with the natural cold source is 3739 h,accounting for 42.7% of the total running time of the whole year;the average COP of the system is 3.9.3.The parameters such as defrosting time,defrosting interval time and start-up and shutdown conditions of refrigeration system were studied to study the air curtain performance,cold storage performance and energy consumption of food refrigerated display cabinets under6 defrosting conditions for 12 hours.The results show that under the operating conditions of defrosting interval 4 h and defrosting time 30 min,the performance of return air temperature and food package temperature is better,and the overall energy consumption is lower.With the decrease of defrosting time or the increase of defrosting interval time,the energy consumption of the system increases,and with the increase of on-stop ratio,the temperature fluctuation time and peak height of food bags in each layer of the display cabinet also increase.4.The numerical model of food refrigerated display cabinet was established,and the effects of defrosting period and start-stop temperature were comprehensively considered.the transient model of food temperature fluctuation,the transient equation of air curtain and the change of food temperature in food refrigerated display cabinet were established by using periodic pulse function equation.The results show that the periodic pulse function can basically reflect the variation law of supply air temperature during the operation of refrigerated display cabinets,and the fluctuation range of food package temperature under defrosting cycle is much larger than that under refrigeration cycle.and with the increase of defrosting interval time and defrosting time,the temperature fluctuation time and peak height of food bags in each layer of the display cabinet also increase.