The given diagram depicts the process of a central heating system in a house.
Overall, it is clearly seen that this process is composed of several stages which start with filling the storage tank with water and the final stage is heating water that goes through small tubes.
According to the diagram, at the first stage, the cold water enters into the house and is stored in a water storage tank. After that the water is flowed down to the boiler, located on the ground floor of the house. In the third phase, water is boiled by petroleum and gas, heats up the water as it passes through it.
At the next stage, the hot water is then pumped round the house through a system of pipes and flows into the radiators, located in different rooms. On top of that the hot water radiators which have small tubes inside them to help distribute the heat and this warms each of the room. The final stage of this process, the water is returned to the boiler to be reheated and circulated around the house again.