HOW TO APPROCH THE OTTO CYCLE THEORY DURING THE UNDERGRADUATE THERMODYNAMICS COURSE IN CMU

The approach presented in this paper refers to the study of the effect of specific heat of working fluid and heat loss on the performance of an Otto cycle, using finite time thermodynamics- as a powerful thermodynamic tool in the hand of specialists. Traditionally, Otto cycle performance issue was presented to the students in the case of constant specific heat, available only if it is assumed that the working fluid behaves as a perfect gas, meaning for relatively small temperature differences. Since in the practice are met large temperature differences, should be considered the case of variable specific heat, in this paper the adiabatic exponent being taken as a liniar function of temperature. For the both situations discussed in the paper are given formula for the calculation of the total energy of the fuel, the heat added to the working fluid, the heat leakage, the compression and expansion efficiencies, the work output and the thermal efficiency. The calculus is based on the cycle shown in temperature- entropy diagram, in which are also indicated the irreversible adiabatic compression and expansion.