scholarly journals Thermodynamic Efficiency Maximum of Simple Organic Rankine Cycles

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 307
Author(s):  
Aram Mohammed Ahmed ◽  
László Kondor ◽  
Attila R. Imre
Keyword(s):  
Heat Source ◽  
Hybrid Systems ◽  
Thermodynamic Efficiency ◽  
Temperature Function ◽  
Working Fluids ◽  
Temperature Heat ◽  
Efficiency Increase ◽  
Organic Rankine Cycles ◽  
Cycle Temperature ◽  
Maximal Cycle

The increase of the maximal cycle temperature is considered as one of the best tools to increase cycle efficiency for all thermodynamic cycles, including Organic Rankine Cycles (ORC). Technically, this can be done in various ways, but probably the best solution is the use of hybrid systems, i.e., using an added high-temperature heat source to the existing low-temperature heat source. Obviously, this kind of improvement has technical difficulties and added costs; therefore, the increase of efficiency by increasing the maximal temperature sometimes has technical and/or financial limits. In this paper, we would like to show that for an ideal, simple-layout ORC system, a thermodynamic efficiency-maximum can also exist. It means that for several working fluids, the thermodynamic efficiency vs. maximal cycle temperature function has a maximum, located in the sub-critical temperature range. A proof will be given by comparing ORC efficiencies with TFC (Trilateral Flash Cycle) efficiencies; for wet working fluids, further theoretical evidence can be given. The group of working fluids with this kind of maximum will be defined. Generalization for normal (steam) Rankine cycles and CO2 subcritical Rankine cycles will also be shown. Based on these results, one can conclude that the increase of the maximal cycle temperature is not always a useful tool for efficiency-increase; this result can be especially important for hybrid systems.

Working fluids for low-temperature heat source

2010 ◽  
Vol 30 (10) ◽  
pp. 1262-1268 ◽  
Author(s):  
Amlaku Abie Lakew ◽  
Olav Bolland
Keyword(s):  
Low Temperature ◽  
Heat Source ◽  
Working Fluids ◽  
Temperature Heat

Selection of Working Fluids for Different Temperature Heat Source Organic Rankine Cycle

2012 ◽  
Vol 614-615 ◽  
pp. 195-199
Author(s):  
Guang Lin Liu ◽  
Jin Liang Xu ◽  
Bing Zhang
Keyword(s):  
Power Generation ◽  
Heat Source ◽  
Flue Gas ◽  
Thermal Power ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Source Power ◽  
Working Fluids ◽  
Cycle System ◽  
Temperature Heat

In the current paper, under the condition of different flue gas temperatures and constant flue gas thermal power, the influence of different organic working fluids on the efficiency of sub-critical organic Rankine cycle system were studied. The efficiency and other parameters of the simple system were calculated. The results show that the efficiency of sub-critical organic Rankine cycle system could reach maximum when the parameters of the working fluids in the expander inlet are dry-saturation. Flammability, toxicity, ozone depletion and other factors of the working fluids should be considered in the organic Rankine cycles. R245fa is considered a better choice for low-temperature heat source power generation, and the efficiency of the system is about 10.2%; for the high-temperature heat source, R601a can be considered; however, due to its high flammability, novel working fluids should be further discovered for power generation.

scholarly journals The design of CO 2 -based working fluids for high-temperature heat source power cycles

2017 ◽  
Vol 129 ◽  
pp. 947-954 ◽  
Author(s):  
S. Lasala ◽  
D. Bonalumi ◽  
E. Macchi ◽  
R. Privat ◽  
J.-N. Jaubert
Keyword(s):  
High Temperature ◽  
Heat Source ◽  
Source Power ◽  
Working Fluids ◽  
Power Cycles ◽  
Temperature Heat

scholarly journals Analysis and Comparison of Some Low-Temperature Heat Sources for Heat Pumps

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1853 ◽  
Author(s):  
Pavel Neuberger ◽  
Radomír Adamovský
Keyword(s):  
Heat Transfer ◽  
Low Temperature ◽  
Heat Source ◽  
Heat Pump ◽  
Heat Exchangers ◽  
Ambient Air ◽  
Heat Transfer Fluid ◽  
Heat Sources ◽  
Ground Heat Exchangers ◽  
Temperature Heat

The efficiency of a heat pump energy system is significantly influenced by its low-temperature heat source. This paper presents the results of operational monitoring, analysis and comparison of heat transfer fluid temperatures, outputs and extracted energies at the most widely used low temperature heat sources within 218 days of a heating period. The monitoring involved horizontal ground heat exchangers (HGHEs) of linear and Slinky type, vertical ground heat exchangers (VGHEs) with single and double U-tube exchanger as well as the ambient air. The results of the verification indicated that it was not possible to specify clearly the most advantageous low-temperature heat source that meets the requirements of the efficiency of the heat pump operation. The highest average heat transfer fluid temperatures were achieved at linear HGHE (8.13 ± 4.50 °C) and double U-tube VGHE (8.13 ± 3.12 °C). The highest average specific heat output 59.97 ± 41.80 W/m2 and specific energy extracted from the ground mass 2723.40 ± 1785.58 kJ/m2·day were recorded at single U-tube VGHE. The lowest thermal resistance value of 0.07 K·m2/W, specifying the efficiency of the heat transfer process between the ground mass and the heat transfer fluid, was monitored at linear HGHE. The use of ambient air as a low-temperature heat pump source was considered to be the least advantageous in terms of its temperature parameters.

scholarly journals Comparative investigation of working fluids for an organic Rankine cycle with geothermal water

2015 ◽  
Vol 36 (2) ◽  
pp. 75-84
Author(s):  
Yan-Na Liu ◽  
Song Xiao
Keyword(s):  
Power Generation ◽  
Pressure Ratio ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Comparative Investigation ◽  
Geothermal Water ◽  
Thermodynamic Investigation ◽  
Working Fluids ◽  
Temperature Heat ◽  
Input Pressure

AbstractIn this paper, the thermodynamic investigation on the use of geothermal water (130 °C as maximum) for power generation through a basic Rankine has been presented together with obtained main results. Six typical organic working fluids (i.e., R245fa, R141b, R290, R600, R152a, and 134a) were studied with modifying the input pressure and temperature to the turbine. The results show that there are no significant changes taking place in the efficiency for these working fluids with overheating the inlet fluid to the turbine, i.e., efficiency is a weak function of temperature. However, with the increasing of pressure ratio in the turbine, the efficiency rises more sharply. The technical viability is shown of implementing this type of process for recovering low temperature heat resource.

Evaluation of isopentane, R-245fa and their mixtures as working fluids for organic Rankine cycles

2013 ◽  
Vol 51 (1-2) ◽  
pp. 292-300 ◽  
Author(s):  
Pardeep Garg ◽  
Pramod Kumar ◽  
Kandadai Srinivasan ◽  
Pradip Dutta
Keyword(s):  
Working Fluids ◽  
Organic Rankine Cycles
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