Thermodynamic models for two district heating, cogeneration steam cycles were developed in this study. These cycles are an extraction-condensing turbine cycle and a back-pressure turbine cycle. Heat and electrical outputs of these cycles were calculated for inlet conditions ranging from 580 psi, 752° F, to 1740 psi, 995° F (4 MPa, 400°C to 12 MPa, 535°C), and district heat supply temperatures ranging from 194° F to 248° F (90°C to 120°C). Furthermore, the performance of these cycles from 0 to 100% of their maximum heat outputs were examined.

A simple method of economic analysis based on annual costs was developed, which can take part-load operations into consideration. An extraction-condensing system and a backpressure system were compared using this method.

Units: Dual