CBE 30356 - Lecture Notes - January 24, 2023
Announcements
Class notes
Read through pages 25-38 of the notes and view the online narration below. Don't forget to complete the quiz in Canvas!
The main points of the lecture were
- Heat transfer coefficients in cylinders
- Heat transfer with generation
Goals:
After this class you should be able to:
- Determine the rate of heat transfer from an insulated pipe.
- Calculate the temperature distribution at steady-state resulting from a heat source per unit volume.
Reading
- The class notes.
- BS&L, 10.2, 10.3, 10.6
Problem of the Day
Energy sources for space missions have always been a problem: solar panels are great, but if the sun is very distant or you are in shade they won't do much good! One solution has been the RTG, a radioisotope thermoelectric generator. In this system a radioactive fuel (often Plutonium 238) radioactively decays via alpha emission, releasing heat and not much else (that penetrates, anyway). This heat source is coupled with a heat sink and the resulting temperature gradient is directly converted to electricity via the Seebeck effect. It's not very efficient, but it is very reliable - pretty important when you are in deep space! In this problem we will examine the design of the SNAP-27 reactors which were used to power instruments on all the manned lunar missions. A description of the device may be found here. The "back of the envelope" analysis of heat transfer in the unit is given here.
Demonstration:
Today we'll be demonstrating the ever-popular can crushing technique. It's a nice example of just how fast heat transfer occurs in a condensing film, as well as the effect of fluid inertia.
David.T.Leighton.1@nd.edu