When we open the horizontally hung door, cold air remains in the refrigerator and energy loss can be minimized. Therefore, the horizontally hung door has an uncoupled design and is a better design than the vertically hung door. Is the horizontally hung door always better? As far as the functional requirements defined here are kept, it is correct. Suppose that constraints are proposed for the amount of stored food or convenience to access items. Then the problem will be different. If a refrigerator with a horizontally hung door violates the constraints, it
cannot be accepted regardless of the satisfaction of the Independence Axiom. When constraints exist, they should be checked first.