Energy Consumption Analysis And Energy Conservation Research On Refrigeration System Of Large Scale Cold Store For Meat Reserve

With the improvement of people’ living,the food quality and food safety catch more and more attentions.Due to improper storage and transportation,the loss caused by food spoilage are about 680 billion CNY per year.Cold chain is the important technologies and equipment to improve food quality and ensure food safety,and cold store are the basic and key facilities of the the cold chain.Cold stores get a fast increase in the passed decades and its energy comsumption problem is increasingly serious.Therefore,a large scale cold store for meat reserve is selected for investigation.The simulation model of air distribution with CFD method and refrigeration model with distributed-parameter method are developed and validated to analyze the system optimization and cold storage operation for energy saving.The main work concludes:It is set up the identification method with rough set theory for the energy consumption of the compressor in the refrigeration system for the cold store.Ten parameters of air dry-bulb temperature,air relative humidity,air dew point temperature discharge pressure,discharge temperature,suction pressure,suction temperature,oil pressure,oil temperature,currency with about 4000 set of data are reducted to two parameters of suction pressure and discharge pressure to represent the performance of the compressor.This work is much helpful to analyze the energy consumption items and energy saving solutions.The CFD simulation model of the coldhouse is built and validated with temperature maps of 39 test points with the average difference of 3.04% and the max difference of 9.76%,which is accurate enough for analysis of air orgnization inside the coldhouse.The supplied air speeds of the evaporators are optimal within 7.32m/s and 8.32m/s(optional 7.32 m/s)to improve the cold storage quality.The evaporators are better to be installed at center and supply air to the wall to make even air speed distribution and air temperature distribution.And the goods should be placed in a decentralized fashion,far to the wall and not in the returning air zone of the evaporators.It is established the CFD simulation model for thermal natural ventilation through the door of the coldhouse,which is validated the temperatures maps of test point and infrared thermal imaging.It is investigated on the influence to the air speed distribution and air temperature distribution caused by the ventilation driven the indoor and the outdoor air temperature difference at different opening rate and opening time of the door.The results show that,the opening rate and opening time of the door have no influence on the air flow path and the formation of the initial neutral plane.While,the decrease of the opening rate and opening time of the door will make less hot and humid air go into the coldhouse,which is one of the important solutions to decrease thermal and humidity load and then decrease the energy consumption.The simulation model of the refrigeration system is built based on the compressor model with graphic method the fin-tube heat exchanger model with distributed-parameter method.Compared with the experimental data,the compressor model can predict the refrigerant flowrate and the compressor power input with the error less than ±1% and the heat exchanger model can predict the heat transfer rate with the error less than ±5%,and the refrigeration system model can also predict the refrigeration capacity and power consumption with the error less than ±5% under different ambient temperature and indoor temperature.The validated model can be an effect tool for the performance analysis and optimization of the main components and the refrigeration system.Based on the thermal balance analysis,the operation strategy is proposed for the refrigeration system for the cold store with cold storage according to the hourly price of electricity.The annual energy power consumption of the refrigeration system with the cold storage operation is compared with that without cold storage based on the thermal balance of the coldhouse and the simulation of the refrigeration system.According to the climate data of 2015,the refrigeration system with cold storage operation can reduce 18.11% of power consumption and 47.48% of electricity cost than that without cold storage operation.The reduction of power consumption is mainly due to the refrigeration system in the cold storage mode,which is mainly opened during the night low temperature,and the energy efficiency of the refrigeration system is improved.While,the saving of electricity cost is mainly due to the policy of hourly electricity price.So the cold storage operation strategy should be optimized acoording to the hourly electricity policy of different cities and the characteristic of the cold store and its refrigeration system,which can achieve a better effect of energy saving and cost reduction.The research of this paper provides a practical simulation tool for the optimization design and operation of the refrigeration system,and provides the basis for the research on the energy saving and cost reduction measures of the cold store.