From Langenberg Award to Journal Publication: Gregory Behrendt's Research on Heat Engine Efficiency

Every undergraduate student has learned that the maximal efficiency any heat engine can achieve is given by the Carnot efficiency, which describes the Carnot cycle and which is independent of the work medium. However, for any other heat engine cycle, what is the optimal working medium that results in the highest efficiency? While one might jump to the conclusion that it must surely be the ideal gas, the situation is actually more intricate. 

Gregory Behrendt (BS, 2026) researched this question supported by the Donald N. Langenberg Undergraduate Research Award in Physics. Starting with a general Helmholtz potential that depends polynomially on molar volume and temperature, he derived exact expressions for the ideal Stirling, Otto, and Brayton cycles. He found that for the thermodynamic systems described by his ansatz for the Helmholtz potential, the maximal efficiency is achieved if the working medium has a fundamental relation that is linear in temperature. This includes the ideal gas, but also classical harmonic oscillators and phenomenological models of the rubber band.

His findings were published in the peer-reviewed journal Entropy (https://www.mdpi.com/1099-4300/28/9/1033). 

Greg is now a graduate student in physics at the University of Maryland, College Park.