Consider a bathtub holding a system of water (where the boundaries of the tub are the boundaries of the system) under the following conditions:
(a) the bathtub has a closed drain and is already full of water at the start of analysis. no steam rises from the water. you want to examine heat transfer loss from the water contained in the tub over time.
(b) the bath tub drain is partially open and hot water is continually added to keep the tub filled and the temperature constant. you want to examine the flow rates required to maintain the temperature of the water in the tub.
for each system (a) and (b), determine if it is characterized as open or closed and state your reasoning.