Day 5: Heat Engines and Cycles

Thermodynamic Processes

At the beginning of the class, we pointed out some state variables of Thermodynamics. They are four vectors that can influence: pressure, volume, temperature, number of moles or number of atoms. 

Top left graph shows a isobaric process, top right shows isochoric process, and the bottom graph shows isothermal process

This is a example problem using different types of processes.

These four graphs match the processes. Ever though isothemal process looks similar with adiabatic, isothermal has gradual change of volume while adiabatic has a sudden change of volume. 

The Working Rubber Band Activity

When we heated the rubber band, the rubber band will actually shrink which we predicted that it would elongate.

Can Lifter Cycle

The can lifter cycle was introduced to us and the four steps of how a can lifter cycle works  were load, heat, unload, cool.

We also discussed that not all heat energy converts to work in this cycle, and the engine wouldn't work if environment temperature is as heat gun's temperature because there is no temperature change.

Then we found the relationship between ΔEint, W, and Q, and figure out the efficiency.

We started to analyse the cycle which has four points and different states. We need to find Eint at each point and find ΔEint.

Finally, we calculated the W to be equal to Q which ΔE = 0. 

We did the mass lifter heat engine experiment to practice analyzing the engine cycle type of problem. We also need to find ΔEint

Conclusion

Today in class we learned some state variables and processes for thermodynamics. We also discussed the engine cycle problems to know the relationship between  ΔEint, Q, and W in different thermodynamic processes.