Numerical Simulation of Gas Exchange in Fresh-keeping Transportation Containers with a Controlled Atmosphere

Maintaining a suitable gas composition in a transportation container with controlled atmosphere is important. When O-2 concentration is below the suitable value, gas exchange is activated to improve O-2 concentration. Computational fluid dynamics was used to compute the effects of exhaust valve location, driving speed, and valve diameter on the gas exchange process. Gas exchange time can be reduced by relocating the exhaust valve to a lower area and by improving driving speed and valve diameter. Moreover, running the fan can shorten gas exchange time and enhance the distribution uniformity of the O-2 volume fraction in a container. The influence of gas exchange on temperature in the container can be reduced by shortening processing time, but this reduction significantly affects the distribution uniformity of O-2 volume fraction. A test was conducted to verify the accuracy of the numerical models. A good agreement was found between the simulation and test values of O-2 volume fraction during gas exchange. Results reveal the rules and characteristics of gas exchange in fresh-keeping transportation containers with a controlled atmosphere.