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 which was located at the DOE Geothermal Test Facility, East Mesa, California is presently being conducted to meet this objective. The testing effort discussed in this interim report involves a supercritical vaporization and counterflow in-tube condensing system with a near horizontal tube orientation. A previous report explored the supercritical heating, supersaturated turbine expansions and the condenser performance in the vertical orientation. This report presents a description of the test facility and results from a part of the program in which the condenser was oriented in a nearly horizontal orientation. Results of the experiments for the in-tube condenser in a nearly horizontal orientation are given for both pure and mixed-hydrocarbon working fluids. Although most of the data is for a completely active condenser in countercurrent flow, some data is available for a configuration in which half of the tubes were plugged and some data for cocurrent (parallel) flow is analyzed. The horizontal-oriented condenser behavior predicted by the Heat Transfer Research Institute computermore » codes used for correlation of the data was not in agreement with experimental results at this orientation. Some reasons for this difference are discussed. A special series of tests, conducted with propane and up to approximately 40% isopentane concentration, indicated that a close approach to integral'' condensation has occurred as was the case with the horizontally oriented condenser (similar results were obtained for the vertical condenser). 18 refs., 37 figs., 15 tabs.« less