An Ingenious Engine CHRIS LANGENFELD CHAPTER 20 Summary

An Ingenious Engine CHRIS LANGENFELD CHAPTER 20

Summary Chris Langenfeld, an engineer at Deka Research, � Tells the story of how his team of engineers redesigned an external combustion engine, called a Stirling engine, so that it could power a wheelchair quietly. � The Stirling engine illustrates how a different engine design harnesses energy to do work. � Describes the Stirling cycle, then explains how advances in battery technologty eventually led his team to choose a battery over the Stirling engine for the wheelchair. � The team plans to use the Stirling engine to power a water purification system for developing countries, and they are considering using it to provide electrical power for truckers who spend the nigh in their cabs.

Rubric � 100%; 3 items+ � 95%; 3 items � 80%; 2 items � 65%; 1 item � 60%; 0 item

The Stirling engine �Is a closed system, which means that the working fluid remains inside the system. It is also a external combustion engine, which means that fuel is burned outside the engine. �The hot side of the Stirling engine is the energy or heat source. �The cool side of the engine is an energy or heat sink. �It does not make sense to say that the cool side is a cool source, because energy moves from a high to a lower concentration.

Question 1 Question �Why is the Stirling engine considered a closed system? Answer �Because the working fluid remains inside the engine. Only energy crosses the system boundary.

Question 2 Question �What were the desiging requirements for the wheelchair engine? �Why did Stirling engine seem like it might meet the criteria? Answer �The engine had to be quiet and had to deliver a lot of power. Because the Stirling engine is an external combustion engine, there are no explosions inside of the combustion chamber. Therefore, the engine is very quiet.

Question 3 Question �Why wasn’t the engine that Chris’s team redesigned used in the wheelchair? How might it be used? Answer �The engine was not used in the wheelchair because battery technology improved, and batteries met the requirements even better than the Stirling engine did. The engine could be used to power water purification systems in developing countries or to provide electrical power to diesel truck cabs.

Question 4 Question �Chris describes the cooling source as and “energy sink. ” Why is the term “energy sink” more appropriate? Answer �Energy does not move from cold to hot objects, only from hot to cold. Nothing is flowing from the cooling source, so “source” is not really and accurate description. “Sink” is more appropriate term.