The Study Of The Influence On Different Volume Opening Rate To The Effect Of Fruits And Vegetables Pressure Pre-cooling

After picking fruits and vegetables in the metabolism is still quite strong, pre-cooling of fruits and vegetables can remove field heat as soon as possible and effectively control their respiration rate, is one of the key steps to maintain the quality of fresh fruits and vegetables. Pressure pre-cooling is the fast, uniform and energy-efficient pre-cooling process, in the industry and academia, also is the focus of the study. Extensive literature shows that when the opening rate constant, changes in fruit and vegetable varieties, changes in the volume of transport box, will make the transport box uneven distribution of pre-cold, which will affect fruit and vegetable's pre-cooling. In this paper, in order to know the effect of different volume opening ratio on pre-cooling fruits and vegetables, pressure pre-cooling test bed is built, and conducted a series of experimental studies and numerical simulations, which will provides a reliable differential basis for the fruit and vegetable pre-cooling technology.1) In this paper, the physical model of transport boxes (include fruits and vegetables) for different volume opening ratio and different wind speed is established, and using FLUENT software to simulate the distribution of transport box internal air space and the flow field changes with time at the different volume opening ratio and different pre-cooling wind speed, during the fruits and vegetables pressure pre-cooling process. The results showed that the small or large opening ratio and wind speed would lead to dead ends of the temperature inside, resulting in uneven temperature distribution inside; so that there exist an optimal volume open ratio and wind speed. When the volume opening ratio is 42.3%, imports of wind speed is 2m/s, the average wind speed inside the center is 0.86m/s, the more uniform temperature distribution inside the transport boxes and the effect more better for fruit and vegetable pressure pre-cooling.2) According to the theory of fruits and vegetables pressure pre-cooling to build a pressure pre-cooling test bed, and whose performance be test. The results show that flow field inside the flow channel and transport box are more stable, which meet the requirement of fruits and vegetables pressure pre-cooling experiments.3) Tomato and cabbage pressure pre-cooling experimental study, in different volume opening ratio, was done by the pressure pre-cooling test bed. The results show that: with the volume opening ratio increases, the cooling Rate of the fruits and vegetables take on increases first and then decreases; when the volume opening ratio is 42.3%, everywhere of the fruits and vegetables almost the same cooling rate, the temperature distribution in the transport box was more uniform, and the pre-cooling effect have the best results.Tomato and cabbage pressure pre-cooling experimental study, in different pre-cooling wind speed, was done by the pressure pre-cooling test bed. The results show that: pre-cooling time of the fruits and vegetables decreases with the wind speed increases, but when the wind speed in the tunnel more than 0.35m/s, the changes of pre-cooling time is no longer obvious; what is more, the fan frequency increases, inevitably lead to the increase in power consumption, so in the single box of tomatoes and cabbage pressure pre-cooling, the wind speed inside transport box recommend the use of 0.86m/s and 0.69m/s.4) The experiments results are consistent with the simulation results, which demonstrates the correctness of the model and the reliability of the calculation methods, and provides a theoretical basis for the system design of the volume opening way pressure pre-cooling.