To optimize the cooling efficiency of a cooler, it is generally recommended to put the ice at the top of the cooler. This is because cold air tends to sink, and by placing the ice at the top, it allows the cold air to flow downward and keep the contents of the cooler chilled.
When you open the cooler, the cold air generated by the ice will naturally flow down and cool the items in the cooler from the top to the bottom. Additionally, placing the ice at the top forms a barrier that helps prevent warm air from entering the cooler when the lid is opened, further maintaining the internal temperature.
By placing the ice at the bottom, you may risk the cold air escaping through the top of the cooler, making it less effective in keeping the contents cold. The items at the bottom may not receive sufficient cooling, and the ice may melt more quickly.
However, it's worth noting that the specific design and insulation properties of the cooler can also affect the cooling performance. It's a good idea to follow the manufacturer's instructions or recommendations for optimal ice placement in your particular cooler model.