Saturday, 27 August 2016

WHAT IS STEADY FLOW PROCESS IN THERMODYNAMICS?

WHAT IS STEADY FLOW PROCESS IN THERMODYNAMICS?

We were discussing various important topics such as “Quasi static or quasi equilibrium process”, “Work and heat transfer in thermodynamics”, “Enthalpy” and “Specific heat of a substance” in our recent posts.

Today we will see here another very important topic i.e. Steady flow process with the help of this post.

So let us see, what is steady flow process

Steady word indicates that there will not be any changes with respect to time and if we will see the opposite of steady then that will be termed as unsteady or transient. When we talk about steady flow then we must understand here that we are talking about constant flow rate of mass and energy throughout the control volume with respect to time.

We can also say that rate of flow of mass and energy throughout the control volume will be constant with respect to time.

For a steady flow process, thermodynamic property of the system will be constant and will not vary with respect to time. Thermodynamic property of the system for a steady flow process may change with respect to space co-ordinate but will always constant with respect to time.

We have used here one term that is “Control volume”. Control volume system is basically defined as one fixed area in space upon which the study will be focused and mass or matter will enter in to the system and will leave the system continuously. For more detail about the control volume, please find the post i.e. “what is control volume system in thermodynamics?

In most engineering applications, engineering equipments or devices (turbines, pumps, heat exchangers, boilers condensers etc) are operated under identical condition for long duration of time and those engineering equipments could be considered as steady flow equipments or steady flow devices.
Let us see here few steady flow engineering equipment's or devices
So, let us define the steady flow process in quite simple way. A process where fluid is flowing through a control volume and thermodynamic properties of the fluid remains constant with respect to time while thermodynamic properties of the fluid may vary with respect to space co-ordinates then that process will be termed as steady flow process.

So, what we have concluded here?

In case of steady flow system, mass and energy of the system throughout the control volume will be remaining constant with respect to time.


We will see another topic i.e. “Mass balance and energy balance in steady flow process” in category of thermal engineering in our next post.

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Reference:

Engineering thermodynamics by P. K. Nag
Image Courtesy: Google

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