Overview of Recent Supercritical Binary Geothermal Cycle Experiments from the Heat Cycle Research Program

Abstract

The Heat Cycle Research Program, which is being conducted for the Department of Energy, has as its objective the development of the technology for effecting improved utilization of moderate temperature geothermal resources. Testing at the Heat Cycle Research Facility located at the DOE Geothermal Test Facility East Mesa, California involves supercritical vaporization and counter flow in tube condensing in an organic Rankine cycle. Results of the experiments are given for both pure and mixed hydrocarbon working fluids. The heater and condenser behavior predicted by the Heat Transfer Research, Inc. computer codes used for correlation of the data was in excellent agreement with experimental results. A special series of tests, conducted with propane and up to approximately 40% isopentane concentration, indicated that a close approach to "integral" condensation was occurring in the vertically oriented condenser. Preliminary results of tests in which the turbine expansion "passed through the two phase region" did not indicated efficiency degradation assignable to these metastable expansion processes.