Solutions of the Ortvay Rudolf International Competition in Physics: Exploding Refrigerator (2016/10 Problem)

The Ortvay Rudolf international competition was first organized in 1970. The focus is usually not on routine school-level problems but rather on problem-solving relying on physical reasoning and skills in recognizing the fundamental character and “heart” of the problem. Some problems lead the contestants to so-far unsolved, open questions, while some are accessible to first-year students. However, only for a relatively small number of problems do official solutions exist. The intention of this paper is to be the first in a series of published solutions discussing the competition problems. The problem treated below is a simple exercise about heat transfer in a thermodynamic system, which highlights the limitations and consequences of accepting seemingly intuitive approximations, and gives a didactical example of “explosive” dynamics. The calculation does not use mathematical techniques beyond those commonly expected of high school students.