V Sharadha is a III year mechanical engineering student at Indian Institute of Technology, Chennai. This work was done when she was JNCASR summer fellow in 2003 at IISc.

 

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In the previous part 1, we saw that the boat is made up of a small shallow chamber, covered by a thin copper diaphragm connected to the water astern of the boat by two pipes, that need to be initially primed. As the base of the chamber is heated, the diaphragm vibrates and the boat putt-putts its way through the water as long as the flame glows.
   
An analysis of the hydrodynamic forces involved in the working of the putt-putt boat was presented earlier.  As a continuation, this part will deal with the thermodynamics of the toy’s working.
   
An experiment done by Finnie and Curl [1] using a glass model, revealed the mechanism. Steam was found to be generated in the chamber as soon as water came in contact with the hot metal surface. The water boils almost instantaneously and the pressure of steam drives out some of the water in the pipes. Meanwhile, the steam in the cooler pipes condenses and the pressure drop in the chamber draws in water from the surroundings, ready for the next cycle to start.

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Address for Correspondence
V Sharadha
III Year
Mechanical Engineering Student
Indian Institute of Technology
Chennai 600 036