Description of wet-to-dry transition in model ORC working fluids

Groniewsky, Axel; Györke, Gábor; Imre, Attila R.

doi:10.1016/j.applthermaleng.2017.07.074

Cited by 39 publications

(35 citation statements)

References 24 publications

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“…No correlation between the fluid categories (wet, dry, and isentropic) and the isochoric specific heat capacity values can be seen here. On the other hand, a strong correlation between categories and the isochoric "molar" specific heat capacity was reported for model fluids [7,30].…”

Section: Application and Correlationsmentioning

confidence: 99%

“…Another very significant issue relates to the isentropic category. It is not proven, but neither real fluid properties available in the NIST Chemistry Webbook database (NIST) Chemistry Webbook database [29] nor theoretical analyses of model fluids [7,30] confirm the existence of any fluids with a perfectly isentropic saturation vapor curve. It means that, for real or even model fluids, entropy cannot be constant in a finite temperature range.…”

Section: Deficiencies In Traditional Classificationmentioning

confidence: 99%

“…The database (Table S1, Supplementary Materials) contains 74 working fluids with their saturation curve properties, but no examples of ACZM and ACNZM sequences could be found. Theoretical analyses of the shape of the saturation curve using two equations of state, namely van der Waals [7] and Redlich-Kwong [29], also indicate that there is no working fluid which can be sorted into sequences ACZM or ACNMZ.…”

Section: Sequences (Categories)mentioning

confidence: 99%

“…After introducing the novel classification, our research turned to finding a simple, measurable physical property with the help of which it is possible to easily differentiate the eight sequences or at least the traditional categories (dry, wet, and isentropic). Based on the results of studies on model fluids [7], isochoric molar specific heat capacity (c V ) seemed to be a proper candidate to establish some correlation with the novel classes. Therefore, our research focused on examining the c V of the saturated vapor curve of real working fluids [32] from the NIST database.…”

Section: Application and Correlationsmentioning

confidence: 99%

“…Obviously, using different working fluids would also influence the actual layout. In some cases, it requires a superheater, a recuperator, or other auxiliary units [7]. Also, the type of expander in use depends on the fluid properties [8][9][10][11], but this problem is not addressed in this paper.…”

Section: Introductionmentioning

confidence: 99%

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A Simple Method of Finding New Dry and Isentropic Working Fluids for Organic Rankine Cycle

2019

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One of the most crucial challenges of sustainable development is the use of low-temperature heat sources (60–200 °C), such as thermal solar, geothermal, biomass, or waste heat, for electricity production. Since conventional water-based thermodynamic cycles are not suitable in this temperature range or at least operate with very low efficiency, other working fluids need to be applied. Organic Rankine Cycle (ORC) uses organic working fluids, which results in higher thermal efficiency for low-temperature heat sources. Traditionally, new working fluids are found using a trial-and-error procedure through experience among chemically similar materials. This approach, however, carries a high risk of excluding the ideal working fluid. Therefore, a new method and a simple rule of thumb—based on a correlation related to molar isochoric specific heat capacity of saturated vapor states—were developed. With the application of this thumb rule, novel isentropic and dry working fluids can be found applicable for given low-temperature heat sources. Additionally, the importance of molar quantities—usually ignored by energy engineers—was demonstrated.

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Section: Application and Correlationsmentioning

confidence: 99%

Section: Deficiencies In Traditional Classificationmentioning

confidence: 99%

Section: Sequences (Categories)mentioning

confidence: 99%

Section: Application and Correlationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Simple Method of Finding New Dry and Isentropic Working Fluids for Organic Rankine Cycle

2019

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Assessment of the thermal efficiency of subcritical power generation cycles using environmentally friendly fluids at various heat source temperatures

Ahmed

2022

Energy Science & Engineering

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This study aims to investigate the effect of the various heat source temperature (T max ) on thermal efficiency (η th ) for the organic rankine cycle (ORC), trilateral flash cycle (TFC), and partial evaporator (PE-ORC). For this purpose, HFE7000, HFE7100, and HFE7500 were used as working fluids (WFs). The results indicate that by using HFE7000, the maximum η th was obtained for all used power cycles and temperature ranges. Compared to HFE7100, HFE7500 has higher η th at TFC, and PE-ORC at low T max , while HFE7100 has the maximum value at high T max . The η th at T max = 353 K for TFC were 8.71%, 8.34%, and 8.59%, while for ORC 12.38%, 11.82%, and 11.71% for HFE7000, HFE7100, and HFE7500, respectively. At T max = 423 K for TFC were 17.65%, 16.26%, and 16.52%, while for ORC were 18.56%, 17.38%, and 16.59% for HFE7000, HFE7100, and HFE7500, respectively. The η th results indicate that the maximum improvement at TFC by using HFE7000, and the minimum was at HFE7100, while for ORC, the maximum was at HFE7000, and the minimum was at HFE7500. Therefore, the HFE7000 fluid behaves as normal dry fluids at any used temperature, while HFE7100 as normal dry WFs at low T max while behaving as very dry WFs at T max extremely close to its T cr . HFE7500 behaves as very dry working fluids. The η th intersections temperature was at T max = 425.2 K and T max = 455.9 K for HFE7500 and HFE7100, respectively. However, there is no η th intersection for HFE7000.

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Investigation of thermal efficiency for subcritical ORC and TFC using super dry working fluids

Ahmed

Imre

2022

Energy Science & Engineering

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Efficiency is a crucial factor for power cycles. Generally, in the same temperature range, the cycle efficiency for a basic organic Rankine cycle (ORC) is higher than a similar trilateral flash cycle (TFC) for almost all working fluids and heat source/heat sink temperature pairs. According to some recent results, by using super dry working fluids, the thermal efficiency of TFC can outperform its ORC counterpart at high temperatures. This study performed the thermodynamics analysis using three dry working fluids with subcritical basic ORC and TFC with zero to partial recuperated heat ratio. The results showed that using recuperative heat exchange effectively contributes to increasing the efficiency of ORC and TFC. However, the rate of efficiency increase in ORC is higher than the TFC, which can be clearly seen, especially at high maximal cycle temperatures. Using super dry working fluids, the recuperator‐free TFC has favorable cycle efficiency at high heat source temperatures. In contrast, by adding heat recovery for both systems, the ORC can outperform the TFC at 0.4, 0.2, and 0.1 recuperated heat effectiveness for Dodecane, Decane, and Nonane, respectively.

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Description of wet-to-dry transition in model ORC working fluids

Cited by 39 publications

References 24 publications

A Simple Method of Finding New Dry and Isentropic Working Fluids for Organic Rankine Cycle

A Simple Method of Finding New Dry and Isentropic Working Fluids for Organic Rankine Cycle

Assessment of the thermal efficiency of subcritical power generation cycles using environmentally friendly fluids at various heat source temperatures

Investigation of thermal efficiency for subcritical ORC and TFC using super dry working fluids

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