Experimental study on parameters affecting grape pressure pre-cooling

The vent hole size and the pressure drop are the important parameters which affect cooling rate and cooling uniformity in pressure pre-cooling of fruit and vegetable. Experimental investigations of grape pressure pre-cooling were conducted with different vent hole sizes and pressure drop. The effect of parameters on cooling rate and cooling uniformity were analyzed. The results show that horizontal diffusion of cooling air enhances with the increasing of vent hole size, and the increasement of pressure drop benefits the improvement of the vertical permeability of the air flow. The increasement of vent hole size and the pressure drop both shorten the 7/8 cooling time in varying degrees. The cooling uniformity is also improved in the same conditions. It is reasonable for the grape carton provided in this experiment to choose the vent hole diameter about 28 mm and the pressure drop about 100 Pa, considering the pre-cooling experiment results and other factors.