 Good morning, I am Upendra Bandarkar from the Department of Mechanical Engineering and I will be occupying you for the next two weeks on the topic of open systems. All this while we have been discussing closed systems and this is typically how it is taught in thermodynamics. Open systems as you have already been defined are systems which allow mass to transfer across its boundaries. Most engineering systems one realizes are open systems and what we will do is we will take a very specific example, a very simplified example which we will use to analyze and then we will generalize it to engineering systems. So before we go ahead and start analyzing open systems, let us have a few illustrations on what open systems are all about. Typically if you take a power plant, you will realize that most subsystems in this power plant can be analyzed as open systems. For example, turbines in gas and steam power plants have an inlet and outlet for mass and one extracts work out of this system. So, this is an open system or one could analyze compressors, fans and pumps where again there is an inlet and outlet for mass, but work is actually input into the system. There could be other systems where rather than work one is interested in heat transfer and in a power plant one can observe boilers where mass comes in and goes out and the water is converted into steam or one could look at heat exchangers or one could look at condensers. One could also be analyzing open systems where there is only a change in velocity that is expected such as nozzles or one could also be looking at flow through pipes and ducts where one is primarily interested in the pressure drop in such systems. Such components also will be seen in refrigerators, in engines and many other systems which are typically of interest to mechanical engineers. One could also think of complex systems. For example, the entire automobile as a whole is a reasonably complex open system. Similarly, human beings are a perfect example of a complex open system. Human beings take in mass in the form of solids, liquids and gases and eject them out likewise. There is energy being created, work is being output and it is a reasonably complex open system. So, these are various illustrations of open systems. We will be primarily dealing with open systems that are of interest to us, that is mechanical engineers and we will take this up in the next lecture. Thank you.