Packaging design is an essential factor to be considered when evaluating the cooling efficiency all along the cold chain. A heat transfer study is crucial to understand better the effect of different package designs on the cooling rate. This experimental study was conducted to characterize the impact of tray design on the local convective heat transfer coefficient (CHTC) within trays representing a half pallet level during cooling. These trays were filled with empty airtight clamshells (AC) representing Modified Atmosphere Packages (MAP). These measurements were performed on two tray designs (existing and optimized designs). The experimental results showed different levels of heterogeneity: along the airflow direction, in the width positions, and between the different sides of the AC. By comparing the performance of different designs, it was found that adding vent holes to the trays improves the uniformity of the average CHTC within the tray but increases the heterogeneity between the different sides of one AC.