scholarly journals Entropy and Entransy Dissipation Analysis of a Basic Organic Rankine Cycles (ORCs) to Recover Low-Grade Waste Heat Using Mixture Working Fluids

Entropy ◽  
2018 ◽  
Vol 20 (11) ◽  
pp. 818 ◽  
Author(s):  
Yong-qiang Feng ◽  
Qian-hao Luo ◽  
Qian Wang ◽  
Shuang Wang ◽  
Zhi-xia He ◽  
...  
Keyword(s):  
Entropy Generation ◽  
Mass Fraction ◽  
Waste Heat ◽  
Low Grade ◽  
Outlet Temperature ◽  
Entransy Dissipation ◽  
Minimum Entropy ◽  
Pinch Point ◽  
Working Fluids ◽  
Condenser Temperature

Mixture working fluids can reduce effectively energy loss at heat sources and heat sinks, and therefore enhance the organic Rankine cycle (ORC) performance. The entropy and entransy dissipation analyses of a basic ORC system to recover low-grade waste heat using three mixture working fluids (R245fa/R227ea, R245fa/R152a and R245fa/pentane) have been investigated in this study. The basic ORC includes four components: an expander, a condenser, a pump and an evaporator. The heat source temperature is 120 °C while the condenser temperature is 20 °C. The effects of four operating parameters (evaporator outlet temperature, condenser temperature, pinch point temperature difference, degree of superheat), as well as the mass fraction, on entransy dissipation and entropy generation were examined. Results demonstrated that the entransy dissipation is insensitive to the mass fraction of R245fa. The entropy generation distributions at the evaporator for R245/pentane, R245fa/R152a and R245fa/R227ea are in ranges of 66–74%, 68–80% and 66–75%, respectively, with the corresponding entropy generation at the condenser ranges of 13–21%, 4–17% and 11–21%, respectively, while those at the expander for R245/pentane, R245fa/R152a and R245fa/R227ea are approaching 13%, 15% and 14%, respectively. The optimal mass fraction of R245fa for the minimum entropy generation is 0.6 using R245fa/R152a.

scholarly journals Entropy generation analysis for the design of a flat plate solar collector with fins

DYNA ◽  
2020 ◽  
Vol 87 (212) ◽  
pp. 199-208
Author(s):  
Milton Muñoz ◽  
Manuel Roa ◽  
Rodrigo Correa
Keyword(s):  
Flat Plate ◽  
Entropy Generation ◽  
Solar Collector ◽  
Entropy Generation Rate ◽  
Design Parameters ◽  
Outlet Temperature ◽  
Minimum Entropy ◽  
Airflow Velocity ◽  
Collector Plate ◽  
Flat Plate Solar Collector

This article describes the optimal design of a flat-plate solar collector with fins, based on the minimum entropy generation criterion. The design parameters were optimized, considering entropy generation due to heat transfer and airflow. The latter has not been considered in previous works. The flat plate in the collector is assimilated to a finned heat sink. The dimensionless entropy generation variation is analyzed to increase values of the number of fins, as well as for different plate thicknesses and heights. We also considered variations in airflow velocity. Our data shows that airflow velocity greatly influences entropy generation. Values other than the optimum found, caused a considerable growth of total entropy. For a collector area of 4 m2, and an outlet temperature of 50°C, the optimum parameters that minimize the entropy generation rate were: 9 fins on each side of the collector plate, a height of 5 x10-2 m, a thickness of 25x10-3m, and an air velocity variable between 0.015 and 0.046 m/s. This development is relevant to the design of flat plate solar collectors, for grain drying applications.

scholarly journals Thermo-Economic Analysis of a Hybrid Ejector Refrigerating System Based on a Low Grade Heat Source

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 562 ◽  
Author(s):  
Gianluca Lillo ◽  
Rita Mastrullo ◽  
Alfonso William Mauro ◽  
Raniero Trinchieri ◽  
Luca Viscito
Keyword(s):  
Heat Transfer ◽  
Economic Analysis ◽  
Energy Demand ◽  
Alternative Energy ◽  
Waste Heat ◽  
Plant Size ◽  
Low Grade ◽  
Two Phase ◽  
Pinch Point ◽  
Cost Of Energy

The rising of the global energy demand requires the use of alternative energy conversion systems employing renewable sources. In the refrigeration and air conditioning fields, heat driven ejector systems represent a promising way to produce the cooling effect by using available low-grade temperature sources. In this paper, a thermo-economic analysis of a waste heat recovery hybrid ejector cycle (WHRHEC) was carried out. A thermodynamic model was firstly developed to simulate a WHRHEC able to obtain chilled water with a cooling load of 20 kW, by varying the working fluids and the pinch point values in the heat exchangers. Specific single- and two-phase heat transfer correlations were used to estimate the heat transfer surface and therefore the investment costs. The operative ranges that provide a reasonable compromise between the set-up costs and the cycle performances were then defined and compared to the current waste heat-driven technologies, such as absorption chillers and organic Rankine cycles (ORCs) coupled with vapor compression cycles (VCCs). The last part of the paper presents an economic analysis providing the map of the design (plant size) and contingent (specific cost of energy, waste heat availability) variables that lead to the economic convenience of a WHRHEC system when integrated to a conventional VCC plant.

Integration of Low-Grade Heat from Exhaust Gases into Energy System of the Enterprise

2021 ◽  
Author(s):  
Petro Kapustenko ◽  
Olga Arsenyeva ◽  
Olena Fedorenko ◽  
Sergiy Kusakov
Keyword(s):  
Heat Exchanger ◽  
Process Integration ◽  
Waste Heat ◽  
Gaseous Mixture ◽  
Energy System ◽  
Low Grade ◽  
Two Phase ◽  
Pinch Point ◽  
Exhaust Gases ◽  
Composite Curve

Abstract In the paper is presented the way of Process Integration application for waste heat utilisation from exhaust gases streams with partial condensation. It is based on the construction of Hot Composite Curve representing the gaseous mixture cooling with accounting for the gas-liquid equilibrium of condensable vapour part. With Cold Composite Curve for streams requiring heating, the Pinch Point is determined. Then the structure of Heat Exchanger Network (HEN) for utilised Heat Integration into the energy system of the factory is developed accounting for the possible splitting of two-phase flow on gas and liquid streams and selection of plate heat exchanger (PHE) types for specific positions in HEN. The method is illustrated by a case study of heat utilisation from exhaust gases after superheated steam tobacco drying and flue gases from natural gas-fired boiler. The heat transfer areas of PHEs in HEN are optimised with the total annualised cost as an objective function. The payback period of the received solution is less than four months with a substantial saving of energy, reduction of greenhouse gases and other harmful emissions of combustion processes.

Supercritical Fluids and Their Applications in Power Generation

2021 ◽  
pp. 566-599
Author(s):  
Huijuan Chen ◽  
Ricardo Vasquez Padilla ◽  
Saeb Besarati
Keyword(s):  
Power Generation ◽  
Supercritical Fluids ◽  
Waste Heat ◽  
Electrical Power ◽  
Rankine Cycle ◽  
Low Grade ◽  
Heat Sources ◽  
Working Fluids ◽  
Low Grade Heat ◽  
Selection Of

Supercritical fluids have been studied and used as the working fluids in power generation system for both high- and low-grade heat conversions. Low-grade heat sources, typically defined as below 300 ºC, are abundantly available as industrial waste heat, solar thermal, and geothermal, to name a few. However, they are under-exploited for power conversion because of the low conversion efficiency. Technologies that allow the efficient conversion of low-grade heat into mechanical or electrical power are very important to develop. First part of this chapter investigates the potential of supercritical Rankine cycles in the conversion of low-grade heat to power, while the second part discusses supercritical fluids used in higher grade heat conversion system. The selection of supercritical working fluids for a supercritical Rankine cycle is of key importance. This chapter discusses supercritical fluids fundamentals, selection of supercritical working fluids for different heat sources, and the current research, development, and commercial status of supercritical power generation systems.

“Entransy,” and Its Lack of Content in Physics

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Adrian Bejan
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Entropy Generation ◽  
Solid Body ◽  
Thermodynamic Temperature ◽  
Entransy Dissipation ◽  
Minimum Entropy ◽  
Constructal Law ◽  
Minimum Entropy Generation ◽  
False Claim

Here, I show that “entransy” has no meaning in physics, because, at bottom, it rests on the false claim that in order to transfer heat to a solid body of thermodynamic temperature T, the heat transfer must be proportional to T. Entransy “dissipation” is a number proportional to well known measures of irreversibility such as entropy generation and lost exergy (destroyed available work). Furthermore, the “principle of entransy dissipation minimization” adds nothing to existing work based on minimum entropy generation, minimum thermal resistance, and constructal law. The broader trend illustrated by the entransy hoax is that it is becoming easy to take an existing idea, change the keywords, and publish it as new.

Design and Analysis of Ejector Powerplant System

2013 ◽  
Author(s):  
Menandro S. Berana ◽  
Edward T. Bermido
Keyword(s):  
High Pressure ◽  
Ambient Temperature ◽  
Waste Heat ◽  
Temperature Drop ◽  
Working Fluid ◽  
Low Grade ◽  
Heat Sources ◽  
Two Phase ◽  
Evaporator Temperature ◽  
Working Fluids

An ejector is a device with no moving components and is made up of four main parts: converging-diverging nozzle, suction chamber, mixing section and diffuser. It has become popular in refrigeration system as it gives the advantage of recovering expansion energy from high pressure difference into compression energy. In this study, the potential use of ejector in powerplants that use low-grade or low temperature heat sources was conceptualized and analytically investigated. A novel combination of the ejector and the organic Rankine cycle (ORC) was proposed. The driving fluid in the ejector of the proposed powerplant cycle is the high-pressure liquid in the separator that is just circulated back to the evaporator in the ORC. Further increase in turbine temperature drop (TTD), which can increase the power output and efficiency of the plant, can be achieved through expansion, mixing and recompression processes in the ejector. Ocean thermal energy conversion (OTEC), solar-boosted OTEC (SOTEC), solar-thermal, waste-heat driven, biomass and geothermal powerplants were considered in the analysis. Mathematical models in our previous studies were developed and used to calculate for nozzle and ejector parameters. The geometric profile of the ejector for optimization with categorized heat sources was determined. Isentropic, internally reversible, and irreversible two-phase nozzle expansions were analyzed. Two-phase flow calculations were continued in the mixing section. It was assumed that the constant-pressure mixing of the primary and secondary fluids occur at the hypothetical throat inside the constant-area section. Calculation for shock wave in the mixing section was also done. The diffuser was analyzed in a similar manner with the nozzle. Calculation for other components and plant efficiencies was finally conducted. Ammonia and propane which are both natural working fluids were used in the analysis. Evaporator temperature range from 293.15 K to 393.15 K and condenser and ambient temperatures range from 283.15 K to 308.15 K were used in the analysis. The lowest ambient temperature of 283.15 K was used for the OTEC and SOTEC powerplants. It was shown that ammonia and propane can operate up to 11 K and 12 K below the ambient temperature, respectively. Ejector efficiency ranged from 90 to 95% for both working fluids. The maximum efficiencies of the ejector powerplant were 19.2% for ammonia and 14.9% for propane, compared to 11.7% and 9.8% of the conventional ORC. It was analytically determined that the efficiency of the ejector powerplant is higher than that of the ORC powerplant for the same working fluid and conditions of the evaporator, condenser and the ambient.

Effect of Working Fluids on Organic Rankine Cycle for the Recovery of Low-Grade Waste Heat

2017 ◽  
Author(s):  
Edwin Santiago Rios Escalante ◽  
João Andrade Carvalho Júnior ◽  
José Antônio Perrella Balestieri
Keyword(s):  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Low Grade ◽  
Working Fluids

Electric Power Generation From Low-Enthalpy Heat Recovery in FPSOs Using Kalina Cycle

2016 ◽  
Author(s):  
Carlos Eymel Campos Rodríguez ◽  
Thiago Gotelip Correa Veloso ◽  
Cesar Adolfo Rodríguez Sotomonte ◽  
Antônio Alves de Moura Junior ◽  
Christian Jeremi Coronado Rodríguez ◽  
...  
Keyword(s):  
Power Output ◽  
Mass Fraction ◽  
Heat Recovery ◽  
Waste Heat ◽  
Second Law ◽  
Water Mixture ◽  
Temperature Differential ◽  
Working Pressure ◽  
Pinch Point ◽  
Kalina Cycle

The present work aims to study, by mean of the First and Second Law the Thermodynamic, the performance of a Kalina Cycle (KCS-34) using low-temperature waste heat recovery in the fourth stage of compression in the CO2 Compression Unit on a Floating Production, Storage and Offloading System (FPSO). Different parameters are evaluated associated with the evaporator to improve the heat absorption of the cycle and taking into account the area of the system too. Three different concentrations of ammonia water mixture are studied, between 65% and 85% of ammonia mass fraction, the CO2 acting as a hot fluid, entry to the evaporator of the Kalina Cycle at 135.2 °C. Some other parameters taking into account in this work are: evaporation pressure, pinch point temperature and terminal temperature differential (TTD) to reach the maximum power production and first and second law efficiency. The Aspen-Hysys software V. 8.6 is used as a tool to simulate the thermal system and Peng-Robinson Stryek-Vera (PRSV) equations of state (EoS). A power output gain in the cycle is obtained with a higher ammonia mass fraction, reaching a maximum net power output of 598 kW using 85% of ammonia mass fraction, a pinch point of 2 °C, a terminal temperature differential of 10 °C and 3500 kPa of the working pressure. Ending, a total heat exchange area calculation is determined in order to have an idea of how big the system is for the different design projects.

scholarly journals Experimental Study and Optimization of the Organic Rankine Cycle with Pure NovecTM649 and Zeotropic Mixture NovecTM649/HFE7000 as Working Fluid

2019 ◽  
Vol 9 (9) ◽  
pp. 1865 ◽  
Author(s):  
Quentin Blondel ◽  
Nicolas Tauveron ◽  
Nadia Caney ◽  
Nicolas Voeltzel
Keyword(s):  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Mass Composition ◽  
Low Grade ◽  
Working Fluids ◽  
Replacement Fluid ◽  
Pure Fluid ◽  
Zeotropic Mixture

The Organic Rankine Cycle (ORC) is widely used in industry to recover low-grade heat. Recently, some research on the ORC has focused on micro power production with new low global warming potential (GWP) replacement working fluids. However, few experimental tests have investigated the real performance level of this system in comparison with the ORC using classical fluids. This study concerns the experimental analysis and comparison of a compact (0.25 m3) Organic Rankine Cycle installation using as working fluids the NovecTM649 pure fluid and a zeotropic mixture composed of 80% NovecTM649 and 20% HFE7000 (mass composition) for low-grade waste heat conversion to produce low power. The purpose of this experimental test bench is to study replacement fluids and characterize them as possible replacement fluid candidates for an existing ORC system. The ORC performance with the pure fluid, which is the media specifically designed for this conversion system, shows good results as a replacement fluid in comparison with the ORC literature. The use of the mixture leads to a 10% increase in the global performance of the installation. Concerning the expansion component, an axial micro-turbine, its performance is only slightly affected by the use of the mixture. These results show that zeotropic mixtures can be used as an adjustment parameter for a given ORC installation and thus allow for the best use of the heat source available to produce electricity.

scholarly journals Thermoeconomic Modelling and Parametric Study of a Simple ORC for the Recovery of Waste Heat in a 2 MW Gas Engine under Different Working Fluids

2019 ◽  
Vol 9 (21) ◽  
pp. 4526 ◽  
Author(s):  
Guillermo Valencia Ochoa ◽  
Carlos Acevedo Peñaloza ◽  
Jhan Piero Rojas
Keyword(s):  
Waste Heat ◽  
Sensitivity Analyses ◽  
Working Fluid ◽  
Pump Efficiency ◽  
Total System ◽  
Pinch Point ◽  
Working Fluids ◽  
Gas Engine ◽  
Specific Investment ◽  
Turbine Efficiency

This paper presents a thermo-economic analysis of a simple organic Rankine cycle (SORC) as a waste heat recovery (WHR) systems of a 2 MW stationary gas engine evaluating different working fluids. Initially, a systematic methodology was implemented to select three organic fluids according to environmental and safety criteria, as well as critical system operational conditions. Then, thermodynamic, exergy, and exergo-economic models of the system were developed under certain defined considerations, and a set of parametric studies are presented considering key variables of the system such as pump efficiency, turbine efficiency, pinch point condenser, and evaporator. The results show the influence of these variables on the combined power of the system (gas engine plus ORC), ORC exergetic efficiency, specific fuel consumption (∆BSFC), and exergo indicators such as the payback period (PBP), levelized cost of energy (LCOE), and the specific investment cost (SIC). The results revealed that heat transfer equipment had the highest exergy destruction cost rates representing 81.25% of the total system cost. On the other hand, sensitivity analyses showed that acetone presented better energetic and exergetic performance when the efficiency of the turbine, evaporator, and condenser pinch point was increased. However, toluene was the fluid with the best results when pump efficiency was increased. In terms of the cost of exergy destroyed by equipment, the results revealed that acetone was the working fluid that positively impacted cost reduction when pump efficiency was improved; and toluene, when turbine efficiency was increased. Finally, the evaporator and condenser pinch point increased all the economic indicators of the system. In this sense, the working fluid with the best performance in economic terms was acetone, when the efficiency of the turbine, pinch condenser, and pinch evaporator was enhanced.

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