The energy consumption of a fridge depends on what it takes to cool the entire contents within a fridge, because heat from center of the food will travel to the surface when the surface cools down. Till the temperature of the entire food item matches the set temperature of the fridge, the fridge will be running. When you open the fridge, warm air enters the fridge, and the contents of the fridge gain heat.
Then there's variability depending on thermal conductivity and specific heat capacity of various foods. So what you're trying to calculate is heavily dependent on the actual contents, not just surface area.
Of course, fridges have cycling behavior similar to an AC that turns on as soon as temp dips below a set temp, but has a window of sorts. Making the above math even more complicated.
> The energy consumption of a fridge depends on what it takes to cool the entire contents within a fridge, because heat from center of the food will travel to the surface when the surface cools down.
This assumes that the dominant energy expenditure of the fridge is bringing new food down to fridge temperature.
But almost all of the contents of a fridge have been in there for a while and are already at fridge temperature. Most of what the fridge is doing is maintaining the internal temperature against the outside environmental temperature.
Biggest factor for many people is that the fridge is wedged in an alcove with insufficient gaps for air flow, so it drowns in it's own waste heat and efficiency plummets.
Then there's variability depending on thermal conductivity and specific heat capacity of various foods. So what you're trying to calculate is heavily dependent on the actual contents, not just surface area.
Of course, fridges have cycling behavior similar to an AC that turns on as soon as temp dips below a set temp, but has a window of sorts. Making the above math even more complicated.