抽气方式与充气压力对盒式气调包装气体置换性能的影响

Effects of gas-exhausting type and gas-charging pressure on gas replacement properties for modified atmosphere packaging with trays

基于不同条件的气体置换流场分析是实现气体置换工艺参数与结构优化的基础。针对盒式气调包装机的关键装置—气体置换装置的物理模型进行流场分析,采用RNGk-ξ湍流模型对进行气流流场数值模拟,建立盒式气调包装气体置换结构内部三维流场;比较等效面积下3种抽气方式对包装内部气体置换性能的影响,确定抽气孔的优化布置方式;分析不同压差工况下的气体置换速度,确定充气压力适宜的工作范围。结果表明,当压强相对于极限真空处于粗真空时(0.04～0.1MPa),3种抽气方式的气体置换效率差异不显著,随着压强的减小(小于0.04MPa),中间抽气方式优于两边抽气方式;同时,采用中间抽气,两边四孔充气方式时,充气压力大于0.5MPa,有利于获得较高的气体置换精度与置换效率。

Gas replacement device is one of the key parts for modified atmosphere packaging（MAP） machine. It is meaningful for investigation and optimization design of the gas replacement device by computer to simulate the gas flow field under different gas-exhausting types and gas-charging pressures. A physical model of MAP with trays was established to analyze gas replacement process depending on the gas replacement mechanism. The RNG k-ε turbulence mode was used to establish the three-dimension turbulent gas flow field during the gas exchange process. With the equivalent area,effect of the gas-exhausting type on gas replacement properties was analyzed,the optimum layout of exhausting mode was determined,and then an appropriate working range of gas-charging pressure was acquired. For three gas-exhausting types,the difference of gas replacement properties was no notable within the vacuum degree range of 0.04-0.1 MPa. Along with the decrease of vacuum degree,the gas-exhausting type of centre hole possessed the best properties. For the exhausting type of centre hole and gas-charging of four holes around the centre hole,the high precision and efficiency of gas replacement could be obtained above 0.5 MPa of the gas-charging pressure.