The difficulty in opening a refrigerator just after closing it is due to the build-up of pressure inside the refrigerator's sealed compartment. When you close the refrigerator door, it creates a relatively airtight seal, and as the cold air inside the fridge cools down, it contracts, leading to a slight decrease in pressure.
This decrease in pressure can create a partial vacuum inside the refrigerator, making it challenging to open the door immediately after closing it. The greater the temperature difference between the inside and outside of the refrigerator, the more significant this pressure difference becomes, resulting in a stronger vacuum effect.
On the other hand, if you open and close the refrigerator several times in a row, you allow some air to exchange between the inside and outside each time you open the door. This process helps equalize the pressure inside the fridge with the external atmosphere, reducing the vacuum effect. As a result, it becomes easier to open the door after multiple cycles of opening and closing.
To make it easier to open a refrigerator after just closing it, you can wait for a few seconds before attempting to open the door. This allows the pressure to stabilize and equalize, making it easier to break the seal and open the refrigerator without facing much resistance.