Development of Geothermal Binary Cycle Working Fluid Properties Information and Analysis of Cycles
The research discussed in this report was performed at the University of Oklahoma during the period January 1, 1978 through December 31, 1978. Efforts were directed to the following tasks: (1) documentation of the GEO4 cycle simulator, (2) modification of GEO4 for fixed heat transfer area, (3) initial comparisons of mixture and pure fluid cascade cycles, (4) development of guidelines for working fluid selection for single boiler cycles, (5) continued evaluation of mixtures as working fluids, (6) specification of commercial isobutane composition requirements for isobutane cycles, (7) identification of working fluid thermophysical property data needs, (8) working fluid thermophysical property correlation and presentation of properties information, (9) effects of using different isobutane thermodynamic correlation parameters in single boiler cycle calculations. Some of the conclusions from this research are: (1) mixture dual boiler cascade cycles can be designed to yield approximately as much work per unit mass of brine as pure fluid triple boiler cascade cycles, indicating mixture cascade cycles are attractive when high brine utilization of low temperature georesources is desired, (2) the specifications by suppliers of a number of presently available commercial isobutanes will perform to yield net plant power for 300 F georesource cycles within one percent of the design value based on pure isobutane as the working fluid, (3) in binary cycles, mixtures have advantages over pure fluids which can be exploited through the use of available heat exchanger types in which essentially countercurrent flow can be maintained, (4) although thermodynamic property data recently obtained by the National Bureau of Standards has lessened data needs for isobutane, the use of other fluids (e.g., isopentane and mixtures) in major geothermal projects will create needs for new experimental work to remove data deficiencies for these fluids, (5) the levels of accuracy of presently available isobutane thermodynamic data and correlations leads to property predictions accurate enough for engineering design calculations for virtually all geothermal binary cycle operating conditions, with the exception of the critical region, which is avoided in most designs due to potential control problems.
- Research Organization:
- DOEEEGTP (USDOE Office of Energy Efficiency and Renewable Energy Geothermal Tech Pgm)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- EW-78-S-07-1719
- OSTI ID:
- 893421
- Report Number(s):
- OU/ID-1719-2; TRN: US200701%%12
- Country of Publication:
- United States
- Language:
- English
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