Which of the following shows the correct heat transfer?
Two bodies brought in thermal contact will change their temperature until they are at the same temperature. In the process of reaching thermal equilibrium, heat is transferred from one body to the other.
Suppose we have a system of interest at temperature 250ºF surrounded by an environment with temperature 70ºF. Since TS > TE heat flows from the system to the environment. If TS < TE heat flows from the environment into the system. Heat flow is a result of a temperature difference between two bodies. Heat flow is considered to be positive when heat flows into the system, negative if heat flows out of the system, and the flow of heat is zero if TS = TE.