Thermal Engineering Systems Exam

Today is the first day of our Term End Examinations(Final Assessment Test) for my 6th semester at VIT University. My subject is Thermal Engineering Systems. 

I have started studying for this exam two days ago as many of my friends told me that it is one of the toughest subject a mechanical Engineer will face. And yes I too felt the toughness of the question paper. Even though I was confident before I went into the examination hall, my confidence was shattered after I have received the question paper. 

I tried my level best. After my exam was over I asked my friend, Sai Ram, how he had done. I saw a smile on his face and understood that he had done well. I don't know the reason for his confidence. There may be two reasons. One reason might be that, he would have performed well really when not compared to others. Other reason might be that he would have performed well when compared to others. Anyways I am not concerned about his performance in the exam. 

I tried attempting each and every question in the question paper. Only one question was out of the concepts which I had learned. All the others were within the concept, but as it was the first exam and being motivated that the question paper will be tough, I was not able to solve any question perfectly except one question. And one question 6a, I have solved the same example problem two days ago. But when I tried to solve the question in the examination my mind didn't respond and was just taking the input and didn't give any output. Just like a computer which gets freezed. This was because it took me around 2 hours for me to solve just two questions and I was left with 1 hour.

Thermal Engineering Systems FAT question Paper - Page 1

Thermal Engineering Systems FAT Question Paper - Page 2

At one point of time after the exam I wanted to stop studying these subjects and do something on which I had. But a simple question was, if I was not able to face a small problem in my life, then can I handle the problems which  I will face in the future doing something else? May be no. So I decided to challenge myself to take all the exams and face each and every question paper. Putting the effort is my part and the results are left to the GOD. May be god will give me good results in this exam.

 Afternoon I evaluated myself whether I had learned anything completing this subject. I can say yes. This exam is not going to decide my future. 

At the end of Thermal Engineering systems I would like to share, the basic principle of refrigeration. Before I will tell you, there are a few things which you should know about. 

When air is expanded from high pressure to low pressure it cools down. Also it gains more velocity.

Similarly when the air is compressed from low pressure to high pressure it gains some temperature. 

We can cool air without changing its pressure, but when the pressure is constant when cooling, also called as isobaric process, the volume of the air decreases. 

These points are valid for any fluid which can be used as refrigerant. 

I think this is sufficient and we can add few other points if necessary in the description. Now see the following image:

Refrigeration Cycle

 Before we continue, for now forget about the Air conditioner and the Refrigerator you use in your home. 

We will start with the compressor. Now here the pressure of the air is increased and as we know the temperature also increases. Now to reduce the temperature we will send it through the condenser and the temperature of the air is reduced. This will be slightly greater than the room temperature. Now as the pressure is high we can cool the same air by expanding it so that the temperature still reduces. We do the same in expander. We send the air through the evaporator which is a high temperature body, as the air is at a lower temperature air grabs some heat from the evaporator and then goes back to compressor and the cycle continues.

Coming back to real world Evaporator is the room in which summer air conditioning is installed. The air coming from the expander cools the room and goes back to the compressor and then to the condenser. The same principle is used but in a different way depending on the requirements.

Now a days instead of using air, manufacturers are using some refrigerants which are better useful in this cycle when compared to ordinary air. There are some important properties which govern their usage which are out of the scope of this post.

Finally thanks for reading on. Hope you had some fun reading my post.

If you can solve or have solved the above question paper then you can post your solution in the comment box below.

You can also add some Thermal Engineering System related concepts in the comment box below if you want to.

Have a nice day!