Thermodynamic - System, Surrounding, Boundary

If we want to do analysis properly on thermodynamic related things, we must devid the thing in three part. They are as below....

1. System

2. Surrounding

3. Boundary

1. System :

Thermodynamic system is a specified region in which we are concentrated for thermodynamic analysis. Or we can say that system is a volume of space containing the item chosen for thermodynamic analysis. The system and its boundary are always chosen by us while doing analysis. A system does not have to be fixed in space. It can move, deform and increase or decrease in size with time. Basically there are three different types of system...
1. Close System
2. Open System
3. Isolated System.

1.1  Close System :

It is a part of system in which mass does not cross the system boundary. But energy may cross system boundary.

This fundamental diagram shows the property of closed system. i.e. in this system only energy can transfer across boundary of system.

 

                             

                                       Closed System (a)

             Closed System (b)

These are the examples of closed system of thermodynamics. fig (a) shows one testing tube in which hot water takes about 75 degree. and in that we knows that glass is good conductor of heat, so in that heat is transfer from water to glass. but the volume of water is constant in test tube. So (Heat) Energy transfer without transfer of mass. Fig (b) shows one plastic jar. also plastic is a good conductor of heat. In this case also (Heat) energy can transfer without transfer of mass.

1.2  Open System :

It is a system in which, both mass and energy may cross system boundary.

This fundamental diagram shows the property of open system. i.e. In this system energy as well as mass can cross boundary of system.

           

Open System (a)

Open System (b)

These are some example of Open System of thermodynamics. Fig (a) shows one cup filled with hot coffee. Here we consider coffee mug with hot coffee as a system. In this case heat is transferred from coffee mug in to atmosphere as well as steam is evaporated from coffee. So heat as well as mass is transferred from system. Thus it called open system. Fig (b) shows a part of steam power plant i.e. Turbine. In this case mass is entering from one side and leaving from other side, and also heat enery is exchang between turbine and surrounding atmosphere. Thus is also called a Open System.

1.3  Isolated System :

It is a system in which, both mass and energy may not cross system boundary.

                        

                                     Isolated System (a)

   Isolated System (b)

Fig (a) shows fundamental diagram of the property of open system. i.e. In this system energy as well as mass cannot cross boundary of system. Fig (b) shows perfectly insulated Thermos. Which is the perfect example of Isolated System. In this case mass as well as energy are not crossing the system boundry. Thus it is called as Isolated System.

2. Surrounding :

If we want to learn simply about surrounding, then remember one thing, "OUTSIDE THE SYSTEM IS SURROUNDING".  But we have to remember one thing that surrounding also has one limited boundary.

For ex :
Suppose we performing an experiment of boiling water in properly air-conditioned room. Then our system is water, and surrounding for this system is cool air. we cannot consider outside room air as a surrounding. So Surrounding itself has boundary.

3. Boundary :

Boundary is nothing but an imaginary line which separates system and surrounding. Boundary is always shown by dotted lines across system. Heat and mass can cross this line to do some useful work.

Or if you understand more about system surrounding boundary you can watch the video (link given below) to understand more about it.

       https://www.youtube.com/watch?v=7BKllTsXhm0&feature=youtu.be

Thank You.