This paper presents the experimental testing of relatively cost-effective expanders in an organic Rankine cycle (ORC) to produce power from low-grade energy. Gerotor and scroll expanders were the two types of expanders tested to determine their applicability in producing power from low-grade energy. The results of the experimental testing showed that both types of expanders were good candidates to be used in an ORC. The gerotor and scroll expanders tested produced 2.07 kW and 2.96 kW, and had isentropic efficiencies of 0.85 and 0.83, respectively. Also the paper presents results of an analytical model produced that predicted improved cycle efficiency with certain changes. One change was the flow rate of the working fluid in the cycle was properly matched with the inlet pocket volume and rotational speed of the expander. Also, the volumetric expansion ratio of the expander was matched to the specific volume ratio of the working fluid (R-123) across the expander. The model incorporated the efficiencies of the expanders and pump obtained during experimental testing, and combined two expanders in series to match the specific volume ratio of the working fluid. The model determined the power produced by the expanders, and subtracted the power required by the working fluid pump and the condenser fan. From that, the model calculated the net power produced to be 6271 W and the overall energy efficiency of the cycle to be 7.7%. When the ORC was simulated to be integrated with the exhaust of a stationary engine, the exergetic efficiency, exergy destroyed, and reduction in diesel fuel while still producing the same amount of power during 2500 h of operation were 22. 1%, 22,169 W, and 4,012 L (1060 U.S. gal), respectively. Consequently, the model presents a very realistic design based on results from experimental testing to cost-effectively use low-grade energy.
This research effort involved experimentally testing an advanced-cycle, ammonia-water absorption chiller with a cooling capacity of 17.6 kW (5 refrigeration tons (RT)). The system was a generator-absorber heat exchange (GAX) cycle and was sized for residential and light commercial use, where very little absorption equipment is currently used. The components of the cycle were assembled with instrumentation, including flow meters, pressure transducers, and thermocouples. The findings of the research were cycle cooling load and coefficient of performance (COP), as well as many component heat duties and working fluid state points throughout the cycle. The COP of the chiller at essentially full load was measured at 0.68. A simulation of the GAX cycle was performed with a computer program that predicted the heat duties of each component and the cooling load of the cycle. The simulation of the GAX cycle and experimental testing compared closely. Existing market research shows that significant business opportunities exist for a GAX heat pump or chiller with a cooling COP of 0.70 or greater. The work performed in this study consisted of testing a GAX cycle with a COP that approached the target value of 0.70 and identified improvements that must be made to reach the target COP value.
This research effort involved experimentally testing an advanced-cycle, ammonia-water absorption chiller with a cooling capacity of 17.6 kW (5 refrigeration tons (RT)). The system was a Generator-Absorber Heat Exchange (GAX) cycle and was sized for residential and light commercial use, where very little absorption equipment is currently used. The components of the cycle were assembled with instrumentation, including flow meters, pressure transducers, and thermocouples. The findings of the research were cycle cooling load and Coefficient of Performance (COP), as well as many component heat duties and working fluid state points throughout the cycle. The COP of the chiller at essentially full load was 0.68. Existing market research shows that significant business opportunities exist for a GAX heat pump or chiller with a cooling COP of 0.70 or greater. The work performed in this study provides a breadboard cycle with performance approaching the target value and identifies improvements that must be made to achieve a packaged unit operating with a cooling COP of 0.70.
Two-phase flow patterns in spirally fluted tubes were investigated through visual observation. Both straight (horizontal) and coiled fluted tubes were studied using adiabatic flow of air and water in transparent castings. The same types of patterns which occur in smooth tubes (i.e. annular, stratified, wave, plug, slug, and bubble) were observed in both the straight and coiled fluted tubes. For these tubes, experimental data support the use of a flow regime map of the type proposed by Breber et al. (1980), which was developed for condensation in smooth tubes. Based on results of the testing of two straight and three coiled fluted tubes, a generalized, modified Breber-style map is proposed for the prediction of flow regimes in spirally fluted tubes.
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