OPTIMAL OPERATION OF FINITE-TIME TRICYCLES WITH HEAT-CONDUCTION LOSSES

We consider the issue of in-principle limits to the finite-time operat ion of a cycling working fluid acting as an agent in the transfer of h eat among three heat reservoirs. The set of feasible operations of suc h a heat engine is explicitly described and its boundary is characteri zed as the set of operations which allocate time optimally among the h eat conduction branches for a wide variety of cost functions. One poin t on this boundary represents the operation that maximizes the heat ou tput at the high-temperature heat reservoir. There is a natural notion of efficiency for such an operation and the result in this case gener alizes the well known result of Curzon and Ahlborn for the efficiency of a Carnot-like heat engine at maximum power.