Research On Regulation Characteristics Of Humidity And Optimization Of Humidifying Equipment For Fresh-keeping Transport

Fresh-keeping transportation with controlled atmosphere is an advanced and effective way to transport fruits and vegetables. Fresh-keeping system with controlled atmosphere can simultaneously regulating the temperature, concentration of oxygen and carbon dioxide, relative humidity and other parameter, to inhibit the respiration and prolong the storage period of fruits and vegetables. The key to the technology of fresh-keeping transportation with controlled atmosphere is providing suitable fresh-keeping environment for fruits and vegetables. Relative humidity is one of the important parameters in the fresh-keeping transportation environment for fruits and vegetables, which has important influence on the fresh-keeping quality of fruits and vegetables, and the humidity control directly affects the quality of storage for fruit and vegetable.In this paper, based on the characteristics of fresh-keeping environment for fruits and vegetables, the ultrasonic humidification device was selected as the research object. In order to improve the evenness of humidification, the pipe type ultrasonic humidifier is designed, and the mathematical model of the pipeline type humidification device is established, which including computational model of total atomizing quantity, pipeline resistance, droplet evaporation and diffusion. The mathematical model was used to predict the humidification effect of the humidification device, and provide a theoretical reference for the optimization design of humidification device. Combined with previous research results, theoretical analysis of the flow field of fresh-keeping transportation carriage with controlled atmosphere for fruits and vegetables had been done, including the analysis of basic governing equations of flow field for carriage, porous media model, component transport model, buoyancy force model, humidity control model.Three-dimensional model of fresh-keeping transport compartment was established by Pro/E. The unstructured mesh was generated by ICEM CFD and analyzed by Fluent. Through the simulation of humidity field, the relative humidity contour of longitudinal and cross section of compartment and goods surface is obtained. To study the effect of pipe diameter, number of holes, speed of air duct on humidity distribution of goods surface by established model. The distribution of humidity field of pipeline type and original deflector type humidification device were compared.The experimental platform of pipeline ultrasonic humidifing device for fresh-keeping transportation with controlled atmosphere was established. In order to evaluate the performance of the humidifing device, the humidification rate and uniformity and the quantity of humidification overshoot were used as evaluation indexes, carry out the single-factor experiment of pipe diameter, the number of holes, the voltage of fan and the wind speed of the air duct. To study the effect of different parameter on the performance characteristics of pipeline type humidification device. The orthogonal optimization experiment of humidification uniformity and comparison experiment were carried out to obtain the optimum parameters of the pipeline humidification device.In the fresh-keeping storage of fruits and vegetables, fungus is one of the important factors that influencing the decay of fruits and vegetables, and ozone has good killing effect on fungi. Adding ozone to ultrasonic humidification tank, apart from giving the tank water sterilization disinfection and improving water quality, zone water diffusion to the compartment can kill moulds of storage environment and improve the preservation quality of fruits and vegetables. To study the variational laws of ozone concentration in tank water and fresh-keeping transportation compartment when the ozone generator works, the effect of different ozone export form and water temperature on variational laws of ozone concentration, the effect of ozone on oxygen concentration of fresh-keeping compartment by experiments. The study can provide theory basis for the design of sterilizing device for fresh-keeping transportation with controlled atmosphere of fruit and vegetable, and determine the optimal structure parameters and operation time, ensure sterilization effect and reduce the consumption of operation energy.