In this work we include, for the Carnot cycle, irreversibilities of linear finite rate of heat transfers between the heat engine and its reservoirs, heat leak between the reservoirs and internal dissipations of the working fluid. A first optimization of the power output, the efficiency and ecological function of an irreversible Carnot cycle, with respect to: internal temperature ratio, time ratio for the heat exchange and the allocation ratio of the heat exchangers; is performed. For the second and third optimizations, the optimum values for the time ratio and internal temperature ratio are substituted into the equation of power and, then, the optimizations with respect to the cost and effectiveness ratio of the heat exchangers are performed. Finally, a criterion of partial optimization for the class of irreversible Carnot engines is herein presented.

The design and assembly of a mechanism to bend schedule 80 stainless steel pipe up to 1½ in nominal diameter is presented. The use of a relatively small hydraulic actuator, coupled with a toothed wheel to produce the bending torque, is a novel approach to the process. The bending method uses two arms and a radius block in order to accomplish the bending. The hydraulic power consumption in the machine is very small (750 W, 3.4 MPa, 11.4 in/min). The strongest restriction upon the design is that it could be manufactured in small shops, with a cost low enough to be profitable even for a small production volume.

Se presenta el diseño y construcción de un mecanismo para doblar tubo de acero inoxidable, hasta de 1½ pulg de diámetro nominal y cédula 80. El sistema fue ideado para pequeñas industrias, que requieren una producción moderada con bajo costo. Emplea una unidad de potencia hidráulica muy reducida (750 W, 3.4 MPa, 11.4 in/min). Para doblar el tubo se emplea el método de doblado guiado. El par torsor se genera con un mecanismo novedoso de rueda dentada y un actuador lineal hidráulico. El tubo se sujeta a un dado de sujeción y un dado guía permanece fijo; el doblado se forma sobre el perímetro de este dado.