Experimental and numerical studies for the air cooling of fresh cauliflowers

The fresh vegetable farm produce needs to be cooled after the harvest before the shipment and the sale. The cooling duration is very sensitive to several parameters: foodstuffs nature (size, weight, properties), harvest period, packaging shapes, climatic conditions … In this paper, experimental and numerical investigations focused on forced air-cooling and room cooling of fresh cauliflowers are presented. For this vegetable, the optimal storage conditions are 4-7 °C and 90-98% relative humidity. As cauliflower is a voluminous (15-20 cm diameter) and heavy vegetable (600 g to more than 2000 g), the cooling process lasts generally several hours (>10 h) in the case of conventional room cooling. In order to apprehend the cooling kinetics of these products, some experiments carried out on a laboratory experimental set-up and on industrial site are presented. A 1D numerical model is firstly implemented to predict the temperature field and the mass loss of a single product. Several heat transfer mechanisms occur at the surface: convection, evaporation and long-wavelength infrared radiation. Based on in-situ experiments during which product temperature, air temperature and hygrometry were monitored, a second model is developed to simultaneously determine the temperature and the mass loss of several products placed in conventional room cooling. Comparisons between simulations and experiments show relevant results.