Thermal/ Heat Reservoir

A thermal reservoir is also known as "Thermal Energy Reservoir Or Thermal Bath". As the name suggests that it stores an infinite amount of energy. And whenever energy is needed, it provides energy. Also, whenever energy needs to be stored, it absorbs and stores energy. 
Thus, it gives energy as well as it absorbs energy. Its temperature does not change whether energy is removed or energy is absorbed. 

Thermal Reservoir/Heat Reservoir
.........We define the thermal reservoir as follows- "A thermal reservoir, or simply a reservoir, is a special type of thermodynamic system that always remains at a constant temperature, regardless of whether energy is added or removed by heat transfer when it is in thermal contact with another system or surrounding".........
Since the interaction of energy in these is only in the form of heat. Therefore, they are sometimes called "Heat Reservoir". Their heat holding capacity is very high or infinite.
For Example- 
1) Expansive bodies of water such as Oceans, Lakes or Rivers are considered thermal energy reservoirs because of their large masses and high heat capacities. 
2) Sun is the best example of thermal energy reservoir that gives us large amount of energy in the form of heat at a constant temperature.
The atmosphere is also considered a thermal energy reservoir.
While other examples are- Boiler furnace, Combustion chamber, Lakes, Rivers, Oceans, Atmosphere ,etc.
NOTE
➛ Thermal reservoirs either provide heat energy or absorb heat energy, but their temperature does not change during this time.
➛ A thermal reservoir or Heat reservoir
• Heat holding capacity is infinite.
• Temperature does not change, whether energy is added or removed.
 
Types of Heat Reservoir
There are two types of heat reservoir (or thermal energy reservoir) based on providing or absorbing energy in the form of heat and these are heat/energy source and heat/energy sink. 
Heat Sources- 
A heat reservoir is considered as a heat source if it is at a high temperature and is capable of transferring heat to the system or surroundings with which it has thermal contact.
For example- Sun, electric heater, burning fuel, etc. 
Heat Sink- 
A heat reservoir is considered as a heat sink if it is at a low temperature and is capable of absorbing heat from the system or surroundings with which it has thermal contact. 
For example- earth, lakes, etc.


........The thermal reservoirs with unlimited thermal capacities are what sink and source should ideally be. This indicates that you can use them to supply(source) or reject(sink) heat without affecting their temperature. These are merely notions to make studying thermodynamics simpler; in practise, such devices do not exist.......
NOTE
➛ "The Sun and the Earth can be thought of as a pair of heat sources and heat sinks". Because the sun is at a very high temperature while the earth is at a low temperature and we know that heat always transfers from an object with a higher temperature to an object with a lower temperature. Therefore, energy in the form of heat is transferred from the Sun (heat source) while this energy is absorbed by the Earth (heat sink). Thus, here the Sun acts as an energy source and the Earth as an energy sink.
➛ We can understand this with another example like when we "Boil Water With Electric Heater". Because heat is needed to boil water. Hence, here the electric heater acts as the heat source and provides heat to boil the water. Whereas the water acts as a heat sink, absorbing the heat received from the electric heater.
➛ High temperature reservoir- Heat Source
     Low temperature reservoir- Heat Sink


FAQs
What is the Source and Sink in thermodynamics???
The source in thermodynamics is exactly what you would expect it to be. It serves as the supplier of heat. And the supply is intended to be limitless in a perfect/ideal system. On the other hand, a system that can receive heat is the sink. A sink in a perfect/ideal system is able to absorb any amount of heat from the source. Its capacity is therefore likewise supposed to be limitless.

How does a definite body differ from a sink and source in thermodynamics????
We want to study a body as a system. The body has the ability to both absorb and release heat energy. However, the size and number of atoms in a body are finite. The body's temperature fluctuates as a result of the addition or subtraction of energy. However, the temperature of the source and sink are infinite and do not changed.


Hope you have found this article helpful!!
Let me know what you think about THERMAL RESERVOIR. Feel free to comment if you have any queries.!!

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