in thermodynamics; certain equilibrium state of the system and that system undergoing certain heat or work interaction the system goes from current equilibrium state to another equilibrium state and this is describe by temperature, pressure etc.
now in this process we are not asking the question how much time goes in that process also we never concern ourselves with the rate at which that heat interaction takes place.
on the other hand
in HEAT TRANSFER
we ask rate of heat transfer because there is a temperature difference heat flow occurs; what is the rate at which this heat flow occurs?
And at a certain point if we want only certain temperature to be attained,how much time would it take-that is the type of questions ask in heat transfer,it is necessary because in study of heat transfer some laws that governs the process of heat transfer on the basis of this rate design equipment ,size equipment in which heat transfer process occurs.