In a temple kitchen or any other traditional setup where pots are placed on top of each other and cooked, the reason the contents in the top pot get cooked first is due to the principle of heat distribution and convection.
When heat is applied to the bottom pot, it creates a temperature gradient within the stack of pots. The bottom pot, being in direct contact with the heat source, receives the most intense heat, and its contents start cooking faster. As the heat travels upward, it gradually loses intensity with each pot it encounters, resulting in slightly lower temperatures in the pots above.
This phenomenon is known as convection. Hot liquids and gases, in this case, the heated air, tend to rise while cooler ones sink. As the air is heated at the bottom, it becomes less dense and rises, carrying the heat with it. As a result, the pots above receive a gentler, indirect heat.
The order of cooking in the stacked pots would typically be from bottom to top, with the bottom pot getting the hottest and the top pot receiving the coolest heat. Cooks take advantage of this heat distribution to ensure that different dishes or ingredients can be cooked simultaneously in the same setup, with each pot offering a different cooking temperature. This allows for efficient use of the heat source and saves time and effort in the kitchen.
It's worth noting that while this traditional method works well for certain types of cooking, modern kitchens often use more advanced and precise heating methods to ensure even cooking throughout multiple pots or pans.