Supercritical Power Cycle Research Articles

Performance of supercritical cycles for geothermal binary design

Supercritical cycles for geothermal power generation systems are studied to raise the power output and thermal efficiency by selecting natural fluids and new organic working fluids as the working fluids and optimizing the cyclic parameters, especially the condensing temperature or pressure. For a given liquid dominated geothermal resource, thermodynamic parameters, using propane, R-125 and R-134a as the working fluids, respectively, are calculated to show the features of supercritical power cycles and compare to other design results shown in references. Greater power output shows that propane and R-134a are appropriate working fluids of supercritical cycles for geothermal binary design.

Optimization of cyclic parameters of a supercritical cycle for geothermal power generation

A supercritical power cycle with a regenerative process is studied to reach the maximum thermal efficiency by the choice of an appropriate working fluid and optimization of the cyclic state parameters, especially the condensing temperature or pressure. For given geothermal resources, the thermodynamic state parameters are calculated to show the features of the supercritical power cycle compared to other design results. The criteria for the choice of working fluids are also set up.

Critical behavior in fluids and fluid mixtures

The presence of large fluctuations near a critical point leads to thermodynamic anomalies not present in classical, i.e., analytic equations, such as that of van der Waals. We introduce the concepts of universality, critical exponents, scaling laws, “field” and “density” variables, “strong” and “weak” directions. Experimental evidence for the presence of nonclassical critical behavior in fluids and fluid mixtures is presented. A scaled thermodynamic potential represents the thermodynamic data of steam, ethylene and isobutane accurately. It is valid up to 1.07 T c, and within ±30% from ρ c. Methods for joining it to an analytic equation are discussed. The generalization to a nonclassical description of fluid mixtures is described, and applications are given. The engineer may require the nonclassical description in custody transfer, design of supercritical power cycles and supercritical extraction. The classical approach is used here to explain peculiarities of dilute mixtures recently reported by several experimenters.