You will very likely encounter technical Thermodynamics Interview questions in the industry. If you’re only barely getting by in class, you’re going to struggle. Make sure you understand concepts in this class, because they will be relevant when you work as an engineer.
Don’t understand power cycles? You’re not gonna make it as an engineer.
Luckily for you, in the industry, they don’t expect you to know all of the in depth stuff. They really only expect a basic understanding of each class.
The questions below are simple thermodynamics interview questions you may encounter during an interview. If you not only memorize the questions below, but understand them, you will do great as an engineer.
Answers should be quick and to the point, while maintaining eye contact with your interviewer. This applies both in person and through a Zoom Interview. Body language can also be difficult to communicate through a Zoom Interview. See 5 quick tips and 5 Zoom Interview Questions for Employers that you’ll need to be ready for.
February 29, 2024Basic Thermodynamics Interview Questions
What is the first law of thermodynamics?
Conservation of energy, basically energy cannot be created or destroyed, only converted.
What is the second law of thermodynamics?
Entropy in a given system must always increase. If I were to provide an example, let’s picture a cube of ice. Consider all of the particles in the cube of ice. If the cube of ice were to melt and remelt, the particles in the cube of ice would not be arranged in the same manner. This is because entropy is always increasing. Entropy is another word for disorganization.
What is the third law of themodynamics?
Entropy of a given system approaches an absolute value as its temperature approaches zero, meaning that the “disorganization” becomes finite.
Explain what the Rankine Power Cycle is.
“The Rankine Cycle is a 4 process cycle where you take your working fluid, water, pump it up, then add heat from the boiler. Once the fluid gets heated, it turns into steam, which drives the turbine to generate work. Upon exit of the turbine, the working fluid goes through a condenser, and the cycle continues again”
How do we calculate efficiency of a system that utilizes the Rankine Cycle?
Efficiency is what you get over what you pay. What we get is the work generated from the turbine, what we pay is for the heat that goes into then boiler.
What is the Otto Cycle?
The Otto Cycle is the ideal thermodynamic cycle describing the function of a spark ignited piston engine.
What is the Diesel Cycle?
The diesel cycle is also a thermodynamic cycle that describes a combustion engine. Fuel is ignited by heat generated during air compression into the combustion chamber.
What is more efficient – the Otto Cycle or the Diesel Cycle?
The Otto Cycle, being more ideal is more efficient. However, the Diesel engine would be more efficient at high compression ratio applications.
What is R-134a?
R-134a is a gas used as a refrigerant for refrigeration and air conditioners.
Can you draw me a Temperature – Entropy Diagram?
See below, but don’t go too in-depth on this.
A really good approach to this type of question is, to walk your interviewer through what you’re doing. Explain each step of what you’re drawing. Also, if you get stuck or don’t know right off the bat, you are fine. An interviewer will want to see how you rationalize the problem.
What is the meaning of saturated liquid?
A liquid in which temperature and pressure are set so that any decrease in pressure without a change in temperature will cause the liquid to boil.
What is the meaning of superheated vapor?
Any liquid that exist in liquid form, past its boiling point, is considered superheated.
Thermodynamics Interview Questions Summary
The above are all basic questions you need to know for a thermodynamics interview. Along with knowing the answers to the above, make sure you physically understand what is going on. As an engineer, you should know how power cycles, car engines, and refrigerators work.
The questions above are linked to being able to understand how the engineering systems work.
This knowledge will ensure you won’t have tunnel vision.
A common problem in the industry is that engineers develop tunnel vision. They look at one problem too long, and forget everything else, and as a result end up making mistakes or forgetting a crucial detail.
About the author
Kazuyoshi Fujimoto, PE
Founder | Engineering Career Coach | Principal Mechanical Engineer
Kazu oversees all of ultmeche’s engineering services. He provides consulting such as resume reviews, rewrites, mock interviews, and all services career related. Additionally, Kazu performs consulting work regarding Oil & Gas, Automotive, and Aerospace & Defense. Kazu is licensed as a professional engineer in the state of California and has 9+ years of experience in Oil & Gas, Automotive, and Aerospace & Defense.