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A novel combined cooling, heating and power (CCHP) system is proposed based on mixture consisting of CO2 and organic fluids to meet the seasonal energy demand in buildings. Thermodynamic model was constructed based on the laws of thermodynamics, and seasonal operation modes were also established. Techno-economic performance was analyzed and the performance of mixture consisting of CO2 and organic fluids compared with CO2 and pure organic fluids. Results show that the temperature of the turbine inlet in trans-critical power cycle should be 10 °C lower than the heat source temperature, with the turbine inlet pressure being approximately 1.4 times as large as critical pressure. Turbine inlet temperature is negatively correlated to the payback period and levelized energy cost while turbine inlet pressure is positively correlated to the system economic performance. The carbon dioxide content is negatively correlated to net power output, thermal efficiency and exergy efficiency, while coefficient of performance will hit the bottom with the carbon dioxide content, except CO2/Propane. For the carbon dioxide content is between 5 % and 10 %, the system overall performance is also close to optimal value. In general, CO2/R134a (0.10/0.90) and CO2/R1234ze(E) (0.10/0.90) is recommendable.

In this study, the solar Organic Rankine Cycle (ORC) system was analyzed to meet some of the electrical energy needed in large and medium-sized buildings and large enterprises such as hotels from solar energy. A simulation study was conducted for different districts in Türkiye that are rich in solar energy potential. These counties and the provinces they are affiliated with; Silifke-İçel, Alanya-Antalya, Bodrum-Muğla, Çeşme-İzmir. The power value transferred to the ORC was determined by considering the instantaneous radiation values and sunshine durations for the districts. The performance of solar ORC was determined by comparing fluids from three different organic fluid types. Organic fluids and types used in design; benzene-aromatic hydrocarbon, cyclohexane-alkane, octamethylcyclotetrasiloxane (D4)-siloxane. Considering the maximum electrical energy values obtained from Solar ORC in the summer months, it was seen that 205 MWh electricity generated was obtained for Silifke with benzene at a heat source temperature of 223 oC in July. Maximum solar parabolic trough collector (PTC) specific electric power value was determined as 59.52 W/m² in Alanya district with benzene in June. When the four districts are evaluated together, it has been determined that benzene performs better than cyclohexane by 3.8% on average and 23% better than D4. When the annual electrical energy values are examined, the highest production was determined as 1625 MWh with benzene fluid in Alanya district. [ABSTRACT FROM AUTHOR]

Poly-generation systems are a feasible alternative to conventional energy production techniques in buildings. A poly-generation system allows for the concurrent production of electricity, heat, cold, and fresh water, with considerable advantages regarding technology, finances, energy recovery, and the environment. In the present study, the organic Rankine cycle (ORC), the humidification–dehumidification desalination system (HDH), and the desiccant cooling system (DCS) are merged with three unique solar-driven poly-generation systems (BS, IS-I, and IS-II) and numerically examined. The proposed options provide energy, space cooling, domestic heating, and potable water to buildings of small/medium scale. Using n-octane ORC working fluid, the impact of operational circumstances on system productivity and execution characteristics was considered. The findings show that (i) the suggested poly-generation systems can provide electrical power, conditioned space cooling, local heating, and fresh water, whereas keeping the conditioned area pleasant, (ii) the IS-I system achieves the best system performance among all compared arrangements (BS and IS-II); (iii) the attained extreme values of W ˙ n e t , m ˙ f r e s h , Q ˙ c o o l i n g , Q ˙ h e a t i n g , and TGOR are 102.0 kW (all systems), 214.70 kg/h (IS-II), 29.940 kW (IS-II), 225.6 kW (IS-I), and 0.6303 (IS-I), respectively. [ABSTRACT FROM AUTHOR]

Poly-generation systems are an exciting new technology that provide an alternative to separating existing energy production methods in buildings. A poly-generation system enables the efficient simultaneous production of heating, cooling, fresh water, and electricity, resulting in many technological, economic, energy recovery, and environmental advantages. This study numerically investigates three proposed novel solar-driven poly-generation systems (BS, IS-I, and IS-II) integrated with organic Rankine cycle (ORC), humidification-dehumidification desalination system (HDH), and desiccant cooling system (DCS) with different heat recovery system arrangements. The suggested systems supply residential structures with energy, space conditioning, domestic heating, and fresh water. The effects of system operating circumstances on productivity and performance characteristics and several organic working fluid types (n-octane, R245fa, R113, isopentane, and toluene) on optimum system performance have been investigated. The results show that (i) the average enhancement percentage of TGOR using integrated poly-generation systems over the separated ones is 68.5%, 68.5%, and 95.5% for BS, IS-I, and IS-II systems, respectively; (ii) when comparing the three systems, the IS-I system outperforms the other systems (BS & IS-II); and (iii) the maximum values of W•net, m•fresh, Q•cooling, and Q•heating, obtained for different proposed systems using n-octane are 102 kW (all systems), 214.7 kg/h (IS-II), 29.94 kW (IS-II), and 225.6 kW (IS-I); (iv) R113 has the highest TGOR of 0.6924 (IS-I) compared to other organic fluids. (v) The improvements in W n e t • , m f r e s h • , Q c o o l i n g • and Q h e a t i n g • with using toluene instead of R113 at tf1 = 40 °C are 177.5%, 105.8%, 389.25%, and 79%, respectively. [ABSTRACT FROM AUTHOR]

Organic Rankine Cycle (ORC) is an electricity generation system in which organic fluid is used instead of water in the low temperature range. ORC is used in power plants to use waste heat to generate electricity. In this study, thermophysical, environmental and thermodynamic performance comparisons of the ORC model were made using dry and isentropic fluids. Within the scope of geothermal applications, the heat source temperature was determined as 110 °C. The effect of changing the evaporation temperature between 65-100 °C on system performance was determined. As performance parameters, pump work, turbine work, input heat, irreversibility values, thermal efficiency and exergy efficiency have been determined for ORC. Thermodynamic analysis was performed using Engineering Equation Solver (EES). As a result of this study, it was observed that the highest values in terms of turbine work and thermal efficiency with R601 fluid were 54.72 kJ/kg and 11.34%, respectively, and 32.84 kJ/kg and 11.91% with R141b fluid, respectively. A fluid that performs best from dry and isentropic fluids has been proposed for ORC. [ABSTRACT FROM AUTHOR]

• Boiling behavior and mechanism between liquid sodium and organic fluid is compared. • Liquid sodium endures longer period of nucleate boiling, with vigorous bubble motion. • Bubble within the risen liquid film of sodium will generate during explosive boiling. • Total thermal resistance of liquid sodium is four orders smaller than that of R134a. Boiling characteristics of fluid is of significant importance for the efficient cooling of high-power devices, where liquid metal and low-boiling-point organic fluid are often used. In this work, the boiling heat transfer characteristics and bubble behavior of liquid sodium (Na) is numerically studied by molecular dynamics simulations, and comparison with a conventional fluid 1,1,1,2-tetrafluoroethane (R134a) is performed. In the simulation, the initial temperature of the liquid sodium is set to 600 K, the initial thickness is 8 nm, and the surface superheat of the solid substrate is 1000 K. The results indicate that, compared to R134a, during the nucleate boiling stage, liquid sodium exhibits a longer duration of nucleate boiling, accompanied by more vigorous bubble motion within the liquid film. The heat flux of liquid Na is three orders higher in magnitude than that of R134a. For liquid sodium, total thermal resistance (R tot) at the onset of nucleate boiling (ONB) is 2.28 × 10−11 K‧m2/W, while for R134a, R tot at ONB is 7.15 × 10−7 K‧m2/W. During explosive boiling, there are noticeable bubbles generation within liquid film of Na, while there are no bubbles inside the liquid film of R134a. Liquid-vapor phase transition involves a competition between kinetic energy and potential energy. For liquid sodium, there exists a critical range of the total energy that triggers the phase transition. [ABSTRACT FROM AUTHOR]

The use of organic Rankine cycles (ORCs) is a viable solution for the recovery of waste heat. For an air separation unit (ASU) with a production of V ˙ O 2 = 58300 m N 3 / h operating in Romania, the value of utilization of the heat transferred to the cooling system of the compression area represents 21% of the global system electrical energy input. To recover this thermal energy and transform it into mechanical energy, an ORC system was proposed. To maximize the production of mechanical power, an exergy analysis was performed. Exergy analysis was used to choose the most suitable organic fluid and find the optimum constructive structure of the Rankine cycle. The calculation of the exergy destruction in the key apparatuses of the system allowed investigation into the optimization search procedure. The large exergy destruction in the liquid preheater suggested the decrease in the temperature difference in this part of the evaporator by increasing the inlet temperature of the liquid; and an internal recuperative heat exchanger was used for this purpose. When permitted, the overheating of the vapors also reduced the temperature difference between the heat source and the organic fluid during the heat transfer process. The analysis was comparatively performed for several organic fluids such as R-245fa, R123, n-pentane and R717. The use of ammonia, that offered the possibility of superheating the vapors at the turbine inlet, brought a gain of mechanical power corresponding to 6% economy in the electrical energy input of the global plant. [ABSTRACT FROM AUTHOR]

Diaphragm pumps are a sort of leakage-proof reciprocating pumps with low flow rate but high head and better efficiency, and can potentially find their applications in organic Rankine cycle (ORC) systems as the feed-pump of organic fluid to the evaporator. A diaphragm pump in an ORC system may suffer from cavitation in the pump suction chamber inevitably when the pump delivers an organic fluid. However, the cavitation performance of the pump has been a little known for organic fluids so far. In the article, the performance of a specific diaphragm pump was determined based on the existing performance charts provided by the pump manufactory in terms of pump rotating speed and inlet liquid pressure for cold water. The net positive suction head required (NPSHr) was predicted by involving thermodynamic effect in cavitation when the pump feeds the organic liquid R245fa to the evaporator in an ORC system at 480rpm rotational speed. The net positive suction head available (NPSHa) was calculated at 100 kPa and 141 kPa inlet liquid pressures, and the corresponding cavitation safety margins were addressed. The subcooling for the NPSHr and NPSHa as well as the safety margin were figured out. Two one-dimensional (1D) mechanical models for motion of the suction valve were built and solved at 480rpm and 100 kPa and 141 kPa inlet pressures. A preliminary experiment was performed to verify the analytical results. It turned out that the NPSHr is reduced to 2.02m from 3.02m NPSHr of cold water due to the thermodynamic effect in cavitation, and the corresponding subcooling is lowered to 8.28 °C from 12.38 °C. 100 kPa but 141 kPa inlet pressure can result in cavitation in the pump. The 1D mechanical models are subject to a rough spatial resolution for the flow field in the suction chamber, hence three-dimensional(3D) numerical simulations of the flow field are desirable.

In this paper, modeling and analysis of a hybrid solar power plant are presented. Within a theoretical framework, thermodynamic modeling of several components of the cycles has been conducted through simultaneous consideration of energy, exergy, and emissions. The energy and exergy of the combined cycle of the solar-gas turbine and organic Rankine cycle (ORC) have been investigated. Heat loss from the solar receiver has been studied considering essential factors such as wind speed, air pressure, and ambient temperature. The emissions, mass flow rate of working fluids, pressure ratio, and concentration ratio are evaluated and compared with a standard fossil-fueled power plant. The results show that the energy efficiency and exergy of the overall system are substantially improved as the solar radiation intensity increases. Furthermore, the output power of the ORC is reported to be higher than that of the Rankin steam cycle. Consequently, when solar energy is used, the carbon dioxide emission is reduced by 150%.

Poly-generation systems are a feasible alternative to conventional energy production techniques in buildings. A poly-generation system allows for the concurrent production of electricity, heat, cold, and fresh water, with considerable advantages regarding technology, finances, energy recovery, and the environment. In the present study, the organic Rankine cycle (ORC), the humidification–dehumidification desalination system (HDH), and the desiccant cooling system (DCS) are merged with three unique solar-driven poly-generation systems (BS, IS-I, and IS-II) and numerically examined. The proposed options provide energy, space cooling, domestic heating, and potable water to buildings of small/medium scale. Using n-octane ORC working fluid, the impact of operational circumstances on system productivity and execution characteristics was considered. The findings show that (i) the suggested poly-generation systems can provide electrical power, conditioned space cooling, local heating, and fresh water, whereas keeping the conditioned area pleasant, (ii) the IS-I system achieves the best system performance among all compared arrangements (BS and IS-II); (iii) the attained extreme values of W˙net, m˙fresh, Q˙cooling, Q˙heating, and TGOR are 102.0 kW (all systems), 214.70 kg/h (IS-II), 29.940 kW (IS-II), 225.6 kW (IS-I), and 0.6303 (IS-I), respectively.

Poly-generation systems are an exciting new technology that provide an alternative to separating existing energy production methods in buildings. A poly-generation system enables the efficient simultaneous production of heating, cooling, fresh water, and electricity, resulting in many technological, economic, energy recovery, and environmental advantages. This study numerically investigates three proposed novel solar-driven poly-generation systems (BS, IS-I, and IS-II) integrated with organic Rankine cycle (ORC), humidification-dehumidification desalination system (HDH), and desiccant cooling system (DCS) with different heat recovery system arrangements. The suggested systems supply residential structures with energy, space conditioning, domestic heating, and fresh water. The effects of system operating circumstances on productivity and performance characteristics and several organic working fluid types (n-octane, R245fa, R113, isopentane, and toluene) on optimum system performance have been investigated. The results show that (i) the average enhancement percentage of TGOR using integrated poly-generation systems over the separated ones is 68.5%, 68.5%, and 95.5% for BS, IS-I, and IS-II systems, respectively; (ii) when comparing the three systems, the IS-I system outperforms the other systems (BS & IS-II); and (iii) the maximum values of W•net, m•fresh, Q•cooling, and Q•heating, obtained for different proposed systems using n-octane are 102 kW (all systems), 214.7 kg/h (IS-II), 29.94 kW (IS-II), and 225.6 kW (IS-I); (iv) R113 has the highest TGOR of 0.6924 (IS-I) compared to other organic fluids. (v) The improvements in Wnet•, mfresh•, Qcooling• and Qheating• with using toluene instead of R113 at tf1 = 40 °C are 177.5%, 105.8%, 389.25%, and 79%, respectively.

En vista de la preocupación mundial por el aumento del consumo energético, así como, la aplicación de alternativas viables que permitan un mejor aprovechamiento de las fuentes energéticas disponibles, los residuos térmicos surgen como una alternativa energética en aplicaciones industriales en las cuales se generan. En este sentido, el presente trabajo analiza el potencial energético de los gases de combustión emitidos por una estación de compresión, los cuales pueden utilizarse como fuente de calor para un ciclo Rankine de potencia el cual opera con varios fluidos de trabajo incluyendo nueve de tipo orgánico y el dióxido de carbon (CO2). Las simulaciones demostraron la capacidad de los fluidos de trabajo para incrementar la eficiencia energética de la instalación a partir de los gases de escape de la estacion de compresión, siendo que el tolueno y el CO2 se destacan por presentar los mayores niveles de eficiencia, 21 y 20%, respectivamente. Con el objetivo de generación de potencia del ciclo, se concluye que los fluidos refrigerantes considerados en el análisis no son aptos para el ciclo en los niveles de temperatura evaluados.

The use of organic Rankine cycles (ORCs) is a viable solution for the recovery of waste heat. For an air separation unit (ASU) with a production of V˙O2=58300mN3/h operating in Romania, the value of utilization of the heat transferred to the cooling system of the compression area represents 21% of the global system electrical energy input. To recover this thermal energy and transform it into mechanical energy, an ORC system was proposed. To maximize the production of mechanical power, an exergy analysis was performed. Exergy analysis was used to choose the most suitable organic fluid and find the optimum constructive structure of the Rankine cycle. The calculation of the exergy destruction in the key apparatuses of the system allowed investigation into the optimization search procedure. The large exergy destruction in the liquid preheater suggested the decrease in the temperature difference in this part of the evaporator by increasing the inlet temperature of the liquid; and an internal recuperative heat exchanger was used for this purpose. When permitted, the overheating of the vapors also reduced the temperature difference between the heat source and the organic fluid during the heat transfer process. The analysis was comparatively performed for several organic fluids such as R-245fa, R123, n-pentane and R717. The use of ammonia, that offered the possibility of superheating the vapors at the turbine inlet, brought a gain of mechanical power corresponding to 6% economy in the electrical energy input of the global plant.

SUMMARY In this article, the application of a hybrid phosphoric acid fuel cell and organic Rankine cycle (PAFC/ORC) system was thermo‐economically investigated for sulfuric acid production in Sarcheshmeh copper complex (SCC); the second largest copper deposit worldwide. The electricity that is produced by the system is consumed by electrolyzer to produce the hydrogen and sulfuric acid. Two scenarios were considered for applying the PAFC thermal energy as thermal source of the ORC to produce further power. The performance of the system was investigated considering various important parameters such as organic fluid type, PAFC current density (IPAFC), fuel & air consumption factors as well as the ORC turbine inlet pressure (Pi, ORC). The unit cost of sulfuric acid and the hybrid system simple payback period were obtained as 0.0215$/kg and 3.65 years, respectively. [ABSTRACT FROM AUTHOR]

In this paper, modeling and analysis of a hybrid solar power plant are presented. Within a theoretical framework, thermodynamic modeling of several components of the cycles has been conducted through simultaneous consideration of energy, exergy, and emissions. The energy and exergy of the combined cycle of the solar-gas turbine and organic Rankine cycle (ORC) have been investigated. Heat loss from the solar receiver has been studied considering essential factors such as wind speed, air pressure, and ambient temperature. The emissions, mass flow rate of working fluids, pressure ratio, and concentration ratio are evaluated and compared with a standard fossil-fueled power plant. The results show that the energy efficiency and exergy of the overall system are substantially improved as the solar radiation intensity increases. Furthermore, the output power of the ORC is reported to be higher than that of the Rankin steam cycle. Consequently, when solar energy is used, the carbon dioxide emission is reduced by 150%. [ABSTRACT FROM AUTHOR]

Summary: Radial inflow turbine is one of the crucial components of organic Rankine cycle (ORC) system, which has great impact on the performance of system. R245fa was selected as the working fluid to recycle the waste heat source with a temperature of 350 to 400 K. The genetic algorithm (GA) was employed in thermodynamic design to optimize the 10 key design parameters, which are needed in aerodynamic design of the ORC turbine. Isotropic efficiency was the fitness function of 10 key variables in GA. The three‐dimensional geometry model was built based on the thermodynamic and aerodynamic design and then was imported into the commercial software ANSYS‐CFX to conduct viscous numerical simulation. Based on the three‐dimensional simulation, the off‐design performance in different mass flow rate, static inlet temperature coupled with different rotational speed was investigated respectively. The results show that at design condition, the maximum efficiency deviation is only 2.5% with the rotational speed variations among the range of 10%, so the radial inflow turbine designed in this research possesses great off‐design performance. An improved thermodynamic and aerodynamic design method is presented.The off‐design performance of the designed turbine is analyzed.The maximum efficiency deviation is 2.5% with the rotational speed variations. [ABSTRACT FROM AUTHOR]

• Branched exchangers. Three different branched exchangers were studied and designed. The heat exchangers is characterized by a specific requirement. The first by keeping the fluid efflux speed constant, the second by keeping the fluid Re number constant and the third according to constructal. • Experimental tests. The branched exchangers were evaluated. The attention focused on the heat transfer and pressure losses. A proper test bench has been realized. All instruments data are considered and provided. Different fluids were used in tests. • Fluids. In the first phase different fluids were studied such as water, oil, high density, and glycol. In the second phase an organic fluid is used. The organic fluid circuit is vacuum made. All tests assessed the thermal efficiency and pressure losses. • Results. In addition to the results of the tests Nusselt, Prandtl and Reynolds dimensionless numbers were calculated. This has allowed to define the phenomena that regulate the thermal exchange. • Comparative evaluation. Once all data have been available, the optimal exchanger configuration has been identified. Future developments concern the achievement of scale 1:5 exchangers and test consequential campaign. The aim of this work is to continue the experimental evaluation of three different compact branched heat exchangers. To complete the previous study, additional experimental tests were carried out, using a commercial automotive refrigerant (Glycol) at different concentrations (50%, 100%). Finally, in order to have a deeper knowledge of this phenomenon and to identify the parameters regulating the heat transfer, an organic fluid has also been used and tested. The use of such a fluid has required a re-elaboration and design of the test bench. In fact, a vacuum circuit has been realized to properly use the organic fluid. As a result, the equipment used has been changed and inserting more sophisticated sensors. Finally, once all the tests have been completed, the various dimensionless parameters, characterizing the heat exchange, have been calculated and a comparative evaluation has been carried out, to determine and propose the optimal configuration of the branched heat exchanger. [ABSTRACT FROM AUTHOR]

The present work deals with the thermodynamic analysis of a solar-powered triple combined power cycle to generate emission-free power. The triple combined cycle comprises one topping cycle as Brayton cycle and two bottoming cycles, namely, steam Rankine cycle (SRC) and organic Rankine cycle (ORC). The Brayton cycle employs double-stage compression with intercooling. During intercooling, heat energy rejected by the compressed air was further utilized in the ORC. The energy carried away after the turbine exit was used in the SRC. The proposed cycle performance is investigated for three working fluids to use with the bottoming ORC. Results showed that the maximum overall thermal efficiency and work output of solar energy-based triple combined cycle are found 21.89% and 218.98 kJ/kg air, respectively, for organic fluid R245fa at the topping cycle pressure ratio of 31. [ABSTRACT FROM AUTHOR]

Abstract Significant amount of energy is wasted in engine systems as waste heat. In this study, the use of supercritical Brayton cycles for recovering exhaust gas heat of large-scale engines is investigated. The aim of the study is to investigate the electricity production potential with different operational conditions and working fluids, and to identify the main design parameters affecting the cycle power production. The studied process configurations are the simple recuperated cycle and intercooled recuperated cycle. As the performance of the studied cycle is sensitive on the turbomachinery design and efficiencies, the design of the process turbine and compressor were included in the analysis. Cycles operating with CO2 and ethane resulted in the highest performances in both the simple and intercooled cycle configurations, while the lowest cycle performances were simulated with ethylene and R116. 18.3 MW engine was selected as the case engine and maximum electric power output of 1.76 MW was simulated by using a low compressor inlet temperature, intercooling, and high turbine inlet pressure. It was concluded that working fluid and the cycle operational parameters have significant influence not only on the thermodynamic cycle design, but also highly affects the optimal rotational speed and geometry of the turbomachines. Highlights • Exhaust heat recovery of large engine by using supercritical Brayton cycle was investigated. • Different low critical temperature working fluids and two cycle configurations were considered. • CO 2 was evaluated as the most suitable fluid and it resulted in highest performances. • System has extremely compact turbomachines in respect to the system power scale. [ABSTRACT FROM AUTHOR]

The main objective of this study was to develop the supercritical heat transfer correlation applicable for organic fluids when flowing upward in smooth tubes based on the available experimental data. The organic fluids contain R-22, R-134a, R-245fa and Ethanol and the associated heat transfer characteristics were compared with non-organic fluids like water and carbon-dioxide (CO2). It was found that the limit heat flux may result in heat transfer deterioration (HTD) of organic fluid and the corresponding values are much smaller than water or CO2. A new criterion to predict the HTD was developed and this criterion yields the best predictive ability against database. It was found that HTD occurs can be well described by the acceleration parameter evaluated at the wall condition rather than at bulk condition. For estimation of the supercritical heat transfer coefficient (HTC) for organic fluid, the present study proposes a new correlation with a physically based correction factor, which gives satisfactory predictions against the HTC of supercritical organic fluid. The new correlation can offer the smallest average deviation of 0.007 and standard deviation of 0.181 among the existing correlations.

In this paper, thermodynamic and thermoeconomic analyses, and also optimization of an organic Rankine cycle (ORC) were performed. The system was adapted to an existing solid waste power plant with a 5.66 MW installed power capacity in order to produce additional power from the exhaust gas. The actual operating data of the plant were utilized during all stages of the analyses. The originality of this paper is based on the analysis of the possibility of the energy conversion of an exhaust gas with a temperature of 566 °C into the electricity by utilizing an ORC system in the concept of waste-to-energy. Four different working fluids: toluene, octamethyltrisiloxane (MDM), octamethyl cyclotetrasiloxane (D4) and n-decane were considered and analyzed for the current system. This is also another novelty of this study due to lack of such a study, in the open literature, that deals with an ORC utilized for a typical municipal solid waste power plant. According to the thermoeconomic analyses, toluene was found to be the optimum working fluid with the maximum power output of 584.6 kW and the exergy efficiency of 15.69%. The optimization of the cycle was performed by using the non-dominated sorting genetic algorithm method (NSGA-II) in MATLAB software environment. The optimization results were compared and the deviations of the net power output and the total cost rate were evaluated as −5.89%, −3.51 $/h for toluene; 0.96%, −3.60 $/h for MDM; 8.45%, −2.04 $/h for D4 and 2.00%, −5.54 $/h for n-decane, respectively. [ABSTRACT FROM AUTHOR]

Power conversion systems based on Organic Rankine Cycles have been identified as a potential technology especially in converting low-grade waste heat into electricity as well as in small-scale biomass, solar, or geothermal power plants. One of the most important steps in designing such a system is the selection of the working fluid and the optimal fluids are highly dependent on the cycle heat source and condenser cooling fluid temperature levels as well as on the power scale. In this study, the use of different types of working fluids in subcritical organic Rankine cycles is investigated thoroughly by means of thermodynamic analysis. The studied fluid groups are hydrocarbons, fluorocarbons, and siloxanes. The impacts of the specific features related to different fluid groups as well as of the relation between the critical temperature and molar mass of the fluid on the cycle design and operational parameters are investigated. As a result of the study, guidelines and recommendations are generated that can be used in the preliminary evaluation of potential fluid candidates and cycle configurations. In general, the results of the study show that the higher the critical temperature of the fluid, the higher the obtainable cycle efficiency if the evaporation pressure slightly below the critical pressure of the fluid can be obtained. On the other hand, the high critical temperature of the fluid typically leads to significantly high expansion ratios over the process expander and to low condensing pressures. The high pressure ratios are especially present when considering the use of complex siloxanes and high critical temperature hydrocarbons as the working fluids. Based on the results, the studied fluorocarbons and low critical temperature hydrocarbons were evaluated as the most suitable fluids for low-temperature applications whereas siloxanes and hydrocarbons with a high critical temperature were evaluated as the most promising fluid candidates for high-temperature ORC applications. [ABSTRACT FROM AUTHOR]

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The goal of this research is to study a cogeneration plant for combined heat & power (CHP) production that utilises the low-temperature waste energy in the power plant of a Suezmax-size oil tanker for all heating and electricity requirements during navigation. After considering various configurations, a standard propulsion engine operating at maximum efficiency and a CHP Plant with R245fa fluid using a supercritical organic Rankine cycle (ORC) is selected. All the ship heat requirements can be covered by energy of organic fluid after expansion in the turbine, except feeder-booster heating. Hence, an additional quantity of working fluid may be heated using an after Heat Recovery Steam Generator (HRSG) directed to the feeder-booster module. An analysis of the obtained results shows that the steam turbine plant does not yield significant fuel savings. However, a CHP plant with R245fa fluid using supercritical ORC meets all of the demands for electrical energy and heat while burning only a small amount of additional fuel in HRSG at the main engine off-design operation.

This publication deals with the draft of measurement chain for application of synthetic organic liquid Hydros Uni in agricultural tractor Zetor Proxima 7441. The used organic liquid was evaluated on the basis of its effect on the technical condition of hydrostatic converter UD 20. By the drafted measurement chain, it was performed individual measurements which were realized by specific engine speed and prescribed temperature. Then, the flow values ​​were statistically analyzed. From the obtained results, it could be concluded that the proposed measurement chain meets the requirements for measuring the flow characteristics of liquids. Based on the results show, organic synthetic transmission hydraulic fluid does not negatively affect the technical condition of the tractor hydraulic pump.

Liquid-separated condensation is an emerging enhanced heat transfer method that simultaneously increases the condensation heat transfer coefficient and reduces the pressure drop. This method was applied to shell-and-tube condensers used in organic Rankine cycle systems. The optimized liquid-separated thermodynamic states of organic fluids which maximize the average condensation heat transfer coefficients were studied for the single-stage and two-stage liquid-separated condensations. Effects of the heat exchange tube diameter, organic fluid mass flux and cooling water temperature rise on the optimized liquid-separated thermodynamic states and heat transfer enhancement effects were also analyzed. Results show that the minimized condenser area decreases by 10.2%–18.1% for the single-stage liquid-separated condensation and 14.5%–25.0% for the two-stage, compared to the conventional condensation. Optimized liquid-separated thermodynamic states of nine organic fluids were also obtained. Reducing the heat exchange tube diameter, organic fluid mass flux and cooling water temperature rise, the decrement in the condenser area increases. Increasing the liquid-separation stage is beneficial for reducing the condenser area. The optimized vapor quality at the liquid-separated unit inlet remains constant as the heat exchange tube diameter and organic fluid mass flux decrease. While, it decreases as the cooling water temperature rise decreases. [ABSTRACT FROM AUTHOR]

In recent years, the use of small-scale organic Rankine cycles (ORC) in exhaust gas heat recovery of reciprocating engines has been intensively studied. In this paper, the working fluid selection and experimental results of a small-scale ORC unit utilizing exhaust heat of a diesel engine are presented and discussed. Based on the working fluid selection study, siloxane MDM was evaluated as the most suitable fluid for the experimental system. The experiments were conducted with the aim of studying and analyzing the capability of the ORC process of recovering heat from the diesel engine exhaust. The high pressure MDM vapor was expanded through an expansion valve; thus, no power was extracted from the experimental setup and the main focus was on studying the performance of the process heat exchangers. The system under study was identified to be capable of efficiently recovering the waste heat of the exhaust gases, and the potential of using high molecular weight and high critical temperature fluids as the working fluids in high-temperature, small-scale ORC applications was confirmed. It was concluded that when using siloxane MDM as the working fluid, the requirements for the process sealing to withstand low vacuum conditions as well as the effective removal of non-condensable gases during the operation can be identified as one of the major challenges in achieving the targeted power output from this type of ORC systems. [ABSTRACT FROM AUTHOR]

• Cavitation model with thermodynamic effect in multiple regimes was proposed. • Vapour bubble growth rate and vapour bubble number density were formulated. • Model was validated with test data on R114, liquid nitrogen, hydrogen and water. • Model underestimates temperature depression by (18.6–43)%. • Model leads to reasonable flow rate-net positive suction head curve for pump. Mechanical feed pumps in organic Rankine cycle (ORC) power plants can suffer from cavitation to lose their normal feeding performance or even damage. Cavitation models for organic fluids in ORC systems are lacking presently. Hence, a new cavitation model with thermodynamic effect was proposed. Surface tension-controlled, inertia-controlled, intermediate and heat transfer-controlled cavitation regimes, and two key elements: vapour bubble growth rate and vapour bubble number density are included in the model. A known air or non-condensable gas concentration in the liquid was employed to determine cavitation nuclei number density. The model was coded in ANSYS CFX as user defined model and validated with cavitating flows of organic fluid R114 in a venturi, liquid nitrogen and liquid hydrogen on a tapered hydrofoil and warm water around a hydrofoil NACA 0015 in cavitation tunnels based on visualised cavity length. Two model constants, temperature depression, and minimal cavitation number were correlated to bulk liquid temperature, Reynolds number, and Jakob number. The temperature and pressure profiles of liquid nitrogen and hydrogen on hydrofoil surface were examined against the experimental data. The model was applied to simulate unsteady cavitating flows of organic fluid R245fa in a diaphragm pump. It was shown that the temperature depression and minimal cavitation number cannot be correlated to bulk liquid temperature, Reynolds number and Jakob number. Two model constants can be correlated fairly to Reynolds number. The model underestimates the thermodynamic effect by 43% for R114, 18.6% for liquid nitrogen and 32.6% for liquid hydrogen based on temperature depression. The predicted temperature and pressure profiles on hydrofoil surface agree with the experimental data for liquid nitrogen. The model can produce an expected curve of mean pump flow rate against net positive suction head available. [ABSTRACT FROM AUTHOR]

The study presents a mathematical investigation on the potential to provide electricity of different solar Organic Rankine Cycle systems and of a photovoltaic system. As input data for all the systems, were considered multiannual climatic data for Cluj-Napoca, Romania. The solar field was considered in three configurations based on flat collectors, on evacuated tubes collectors and on parabolic trough collectors. The Organic Rankine Cycle was modelled for three working fluids considering the thermal regime typical for each type of solar collectors. It was found that the maximum electric power for the solar thermal systems was situated in the range of (58.57 … 86.57) W/m 2 of solar collector and for the photovoltaic system was of 103.06 W/m 2 of photovoltaic collector. The maximum global efficiencies of the investigated solar thermal systems was situated in the range of (6.73 … 10.23)% while for the photovoltaic system was of 10.81%. Between the solar thermal systems, the most efficient proved to be the one based on evacuated tubes collectors. Additionally it was investigated an existing solar thermal system based on heat pipes solar collectors, located in the vicinity of Timişoara, Romania which left without consumers and in need to be converted into an electrical system. [ABSTRACT FROM AUTHOR]

The paper presents a literature review on the topic of vapour power plants working according to the two-phase thermodynamic cycle with supercritical parameters. The main attention was focused on a review of articles and papers on the vapour power plants working using organic circulation fluids powered with low- and medium-temperature heat sources. Power plants with water-steam cycle supplied with a high-temperature sources have also been shown, however, it has been done mainly to show fundamental differences in the efficiency of the power plant and applications of organic and water-steam cycles. Based on a review of available literature references a comparative analysis of the parameters generated by power plants was conducted, depending on the working fluid used, the type and parameters of the heat source, with particular attention to the needs of power plant internal load. [ABSTRACT FROM AUTHOR]

The goal of this research is to study a cogeneration plant for combined heat & power (CHP) production that utilises the low-temperature waste energy in the power plant of a Suezmax-size oil tanker for all heating and electricity requirements during navigation. After considering various configurations, a standard propulsion engine operating at maximum efficiency and a CHP Plant with R245fa fluid using a supercritical organic Rankine cycle (ORC) is selected. All the ship heat requirements can be covered by energy of organic fluid after expansion in the turbine, except feeder-booster heating. Hence, an additional quantity of working fluid may be heated using an after Heat Recovery Steam Generator (HRSG) directed to the feeder-booster module. An analysis of the obtained results shows that the steam turbine plant does not yield significant fuel savings. However, a CHP plant with R245fa fluid using supercritical ORC meets all of the demands for electrical energy and heat while burning only a small amount of additional fuel in HRSG at the main engine off-design operation. [ABSTRACT FROM AUTHOR]

Abstract: Solar thermoelectric, even for small sizes, is continuing to garner more attention, by virtue of maturation of small size organic Rankine cycle generators, and of small size absorption chiller even if cost and reliability are still not optimal. Indeed, solar thermal power technology improvement would consent to stimulate an ambit already present in Europe and Italy with a well-known tradition and established leadership and efforts focused on a single solar technology would bring to positive effects concerning controllable electric and thermal energy uses. In this context, the present work tries to summarize the possible cycles and fluids that can be applied in a small solar thermal power plant. Despite a plethora of simulated and experimental cycles and fluids, the simplest cycle using near isentropic fluids seems to be the best choice for a small ORC-based CHP system, even if particular attention has to be done to all the sizing parameters (electricity, heating and cooling demand; area and type of solar collector; flow and temperature of the thermal carrier; flow, temperature and pressure of the working fluid; storage volumes; etc.). Indeed, efficiency and reliability of the reported systems are very different, but, it seems that global efficiency of even more than 10% and global cost of even less than 10,000 €/kW can be obtained even at size of few kW if adequate systems are constructed and managed. [Copyright &y& Elsevier]