In this paper we use a variational approach to study an endoreversible Curz
on-Ahlborn-Novikov (CAN) heat engine under both maximum power and maximum e
cological function conditions. By means of this procedure we analyze the pe
rformance of a CANheat engine with a nonlinear heat transfer law (the Dulon
g-Petit law) to describe the heat exchanges between the working substance a
nd its thermal reservoirs. Our results are consistent with previous ones ob
tained by means of other procedures. In addition, we obtain expressions for
the temperatures of the isothermal branches of the working fluid under max
imum power conditions. Finally, we present an expression for a kind of none
ndoreversible Carnot efficiency. (C) 1999 Elsevier Science Ltd, All rights
reserved.