Almost
everyone uses a water heater in day to day life. But how many of us have the
exact idea of how it works and how the cold water is converted to hot water?
What are the elements that are used for this process?
● We use hot water for
various purposes in daily life. For domestic purposes like cooking, bathing,
etc. or for industrial purposes, we require hot water. Water heating is a
thermodynamic process where a source of energy is used to heat water. The
energy source may be natural gas, liquefied petroleum gas, propane, oil, or
electricity. Now-a-days solar energy is also used for the water heating process.
● For the process of
heating water we need three main components. They are:
○ Dip Tube (Inlet
tube): Cold water enters the tank through this tube.
○ Outlet Tube: Hot water goes out
of the tank through this tube.
○ Heating
element: This element helps in heating the cold water.
● There are various
other parts used in a water heater.
○ Steel tank: This unit holds the
water. The steel tank has to be constructed in such a way that it should be
able to withstand the pressure of water inside the tank.
○ Temperature and
Pressure relief valve: These valves are specially placed for safety purposes. This valve
prevents the heater from explosion during abnormal conditions like high
pressure and temperature. It can be mounted either at the top of the tank or at
the sides of the tank.
○ Drain Valve: The drain valve is
used for cleaning and maintenance.
○ Thermostat: A thermostat is
generally used to control or maintain the temperature within the tank.
○ Anticorrosion
Anode Rod: This rod, also known as a sacrificial anode rod, aids in keeping
the steel tank free from corrosion. This rod is made up of magnesium, which
attracts corrosive elements and thus prevents the tank from corroding. This rod
can be replaced when it becomes eroded.
● Apart from this
there is insulation provided that surrounds the steel tank of the heater.
● The steel tank is
internally coated with an epoxy or glass lining to prevent corrosion (in
addition to anticorrosion rod).
● Generally electric
water heaters have two heating elements each wired with a thermostat. Both the
heating elements do not function simultaneously. First the top heating element
functions until the upper tank is hot and then the function is transferred to the
bottom heating element, which has its own thermostat. Usually the water in the
upper tank is heated from 120-140 F before the control is transferred to the
lower heating element.
● But some heaters
have only one heating element which makes maintenance easier. In case of
heating element failure it can be detected and replaced easily when there is
only one heating element.
● When the hot water
is consumed, once again cold water enters through the dip tube and the process
is repeated.
● The gas water heater
is very similar in construction to the electric water heater. Here instead of
electric supply, there is a gas supply. Instead of heating elements, there is a
burner and burner control. The burner is used for heating the water in gas
water heaters.
● The working
principle is based on law of convection. The cold water always remains at the
bottom as it is denser than the hot water. As the water gets heated up it
expands and moves to the top of the tank. If you look at the construction, we
can see that the outlet tube is always smaller than the dip tube (inlet tube).
This is to ensure that cold water is not supplied and only hot water is
supplied through the tube. There is also a flue exhaust in gas type water
heater which acts as heat exchanger as well as is used in exhausting the
combustion gasses.