Thermodynamics

Description of Course Goals and Curriculum

This course aims to teach students the basics of thermodynamics including open and closed systems, heat and energy transfer, thermodynamic tables, entropy, and eventually building to gas, vapor, and combined power cycles. Instruction begins with energy balance, which is largely a review from physics courses. Next is finding properties of a system such as temperature, pressure, and specific volume using ideal gas law for ideal gases and thermodynamic tables for pure substances. As the course progresses students will apply these principles to analyze refrigeration cycles, heat engines, and find the efficiency of these cycles by comparing them to their idealized versions. The final two weeks of the course teach students Otto and Diesel cycles (the types used in car engines), jet propulsion cycles, and cycles that consist of both working gases and pure substances which require attention to detail and many steps to solve. Overall, this course builds on concepts taught in physics and demonstrates how thermodynamic principles govern everyday life in ways students may not have realized before taking the course.

Learning From Classroom Instruction

The course moves slowly before midterms, spending lots of time on the 1st and 2nd laws of thermodynamics which allow students to gain a deep understand of how energy flows in and out of working systems. After midterms, the course moves at a faster pace teaching many cycles and students will be expected to dedicate more time studying outside of class. Lectures teach all the material students will need for exams and assignments, however reading the textbook first is very helpful and effective for this specific course. Some professors also post condensed textbook chapter notes and it is certainly worth the time to skim through these before lectures. There are lots of example questions solved in lecture that help students understand the thermodynamic concepts explained earlier in the lecture. Precepts review new concepts learned in class and go over additional example problems which are often similar to or slightly harder than homework problems. Attempting the precept problems beforehand will greatly help students to recognize where their intuition differs from the correct method and allows students to listen more to what the preceptor is saying rather than rushing to copy notes. Exams are largely focused on problem solving so it is important to look for patterns early in the course and continue to mentally sort new cycles into these patterns. Preceptors will often make note of these patterns and it is very important to listen when they are synthesizing material in this way.

Learning For and From Assignments

Homework assignments consist of simple problems that ensure students understood the basic concepts of the previous week’s lectures, however do not prepare students for exam type questions. While homework questions will make sure students know the general strategies for finding unknowns in cycles and systems, exam questions often have one or two values in each question that are tricky to find. This is what makes exams difficult. On tests if a student is unable to find one of these unknowns in the given time, the student should solve the remainder of the problem symbolically and then return and attempt to find this unknown if there is time. Furthermore, exams will combine multiple topics into single problem so it is beneficial to do practice problems that also combine topics to prepare. The grading for solutions in this class is similar to most other Princeton stem courses. There is a logical way to solve each problem starting with energy and mass balance equations, plugging in known values, solving for unknowns, and finding the final value that the question asks for. This is what is expected on exams. If a student has trouble approaching exam questions, it is helpful to start by writing out identification words such as “ideal gas” or “pure substance” and then begin solving from there. The old exams are useful to learn the format of exams and can give a general idea on what concepts are most important, but anything learned in the course is fair game and just because there was a long question on entropy one year does not mean that there will be a long question on entropy in the current year. A comprehensive formula sheet is given on exams that will provide equations and cycle diagrams. As long as a student can read the diagrams, there is no need to memorize the cycles processes. For the equations on the formula sheet, it is important to know when certain equations can be used. For example, some equations may only be used on open systems or for ideal gases, and this is not stated on the formula sheet.

External Resources

Thermodynamics is a course taught at many universities so there are lots of resources on the internet that may help students. In particular, MIT’s Open Courseware website has lots of well written notes on the topics discussed in MAE221. Past exams and lecture recordings from other universities can be helpful tools, however, the professors for this course often post a surplus of resources and practice problems so most students in the course do not utilize these external resources.

What Students Should Know About This Course For Purposes Of Course Selection

Many students find this to be the most challenging course in their semester. Almost all of the students in the course are MAE majors or studying a different type of engineering. This means professors expect most students to have taken physics courses and may move quickly through energy balances and some early topics. This course is extremely backloaded as the entire course builds up to the final two weeks, in which students will be expected to learn to analyze many kinds of cycles very quickly. Keeping up early is not difficult and worth the effort to ensure a student is going into the final few weeks with a solid foundation. The textbook is often posted online by the professor so it may not be necessary to purchase it. Furthermore, the professor is happy to share any answers to textbook questions with students who want to do extra practice problems. Overall, there are lots of resources to learn thermodynamics and do well in the course. It will be very challenging, but it is worthwhile and is certainly relevant to engineering which excites many students who choose to take this class. For me personally, learning about jet propulsion cycles allowed me to see how thermodynamics is relevant in the real world and this course, although challenging, made me even more excited to be an engineer.