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The organic Rankine cycle (ORC) is an effective way for engine waste heat recover (WHR). The selection of the working fluid is crucial. In recent years, low GWP and ODP working fluid have been invented. For R123, which is commonly used in engine ORC-WHR system, the alternative working fluid is R1233zd(E). In order to explore the performance of R123 and R1233zd(E) when applied to ORC-WHR system, this study conducted experimental studies of R123 and R1233zd(E) under a wide range of engine working conditions. The experiments were carried out under seven sets of engine working conditions with gradually increasing loads. Variable operating parameter experiments were carried out for R123 and R1233zd(E) at each engine load. The selected operating parameters include expander speed and superheat degree. The experimental results show that R123 has higher output power and thermal efficiency compared to R1233zd(E) at all engine conditions.The maximum output power and thermal efficiency of R123 are 1.55 kw and 5.81% respectively.The maximum output power and thermal efficiency of R1233zd(E) are 1.43 kw and 5.29% respectively. Taking the net output power as the evaluation index, the optimal expander speed of R123 is higher than that of R1233zd(E) under the same engine working condition, and the superheat degree has little effect on the net output power. [ABSTRACT FROM AUTHOR]

Various working fluids are applied during geothermal reservoir development, and geothermal reservoir damage induced by contacts between working fluids and reservoir formations are inevitable. Reservoir damage mechanisms, including solid and colloidal plugging, fluid sensitivity, stress sensitivity, and water locking, provide guidance for designing reservoir protection working fluids. In this paper, based on the design principles of reservoir protection working fluids applied in oil–gas reservoirs, four design principles of reservoir protection working fluids are proposed to eliminate potential geothermal reservoir damage for geothermal reservoirs, containing solid-free, facilitated flowback, temporary plugging, and inhibition. Solid-free is achieved by replacing solids with polymers in working fluids. Surfactant and materials with low affinity towards rock surfaces are applied for the facilitated flowback of working fluids from reservoir formations. Temporary plugging is achieved by using temporary plugging materials, some of which are polymers that also apply to solid-free working fluids. Besides, some of the temporary plugging materials, such as surfactant, are applicable for both the facilitated flowback and inhibition of working fluids. The inhibition of working fluids include the inhibition of clay minerals, which can be attributed to clay mineral inhibitors or activity regulators in working fluids, as well as the inhibition of mineral precipitations. This review aims to provide insights for geothermal reservoir protection working fluids, contributing to achieving an efficient development of geothermal resources. [ABSTRACT FROM AUTHOR]

• Ammonia condensation has been experimentally studied in 8 mm and 11 mm tubes. • A new phenomenological model has been proposed for ammonia condensation. • The lowest condensation HTCs characterise the downstream flow. The paper proposes the experimental study of ammonia condensation in aluminium tubes with 8 mm and 11 mm internal diameters. The new study aimed to compare and extend the existing ammonia in-tube condensation data. The lines were tested mainly in horizontal configuration at mass velocities of 20 to 160 kg·m−2s−1, saturation temperature of 35 to 65 °C and inlet vapour quality of 0.1 to 0.9. Shah (1979), laminar-laminar Dobson and Chato (1998), and Cavallini et al. (2001) models predict well ammonia condensation HTCs at mass velocities of 120 to 160 kg·m−2s−1. A new phenomenological model has been proposed for the mass velocities of 20 to 120 kg·m−2s−1, predicting the test data with an accuracy of ±20 %. Similar ammonia condensation HTCs have been obtained for horizontal and upstream flows at a mass velocity above 120 kg·m−2s−1. The lowest condensation HTCs at the considered boundary conditions characterise the downstream configuration of an in-tube condenser at a mass velocity below 120 kg·m−2s−1. However, inclining the ID 8 mm tube by 15° from the normal substantially increases the condensation HTCs by 10 to 30 %, depending on vapour quality. At the inclinations of 15 to 45° from the horizontal line toward the downstream flow, the condensation HTCs exceed the ones of horizontal flow by 10 to 15 % at the vapour quality of <0.5 and low mass velocity of 80 kg·m−2s−1. [ABSTRACT FROM AUTHOR]

Horizontal well drilling and multi-stage hydraulic fracturing technologies are at the root of commercial shale gas development and exploitation. During these processes, typically, a large amount of working fluid enters the formation, resulting in widespread water-rock interaction. Deeply understanding such effects is required to optimize the production system. In this study, the mechanisms of water-rock interaction and the associated responses of shale fabric are systematically reviewed for working fluids such as neutral fluids, acid fluids, alkali fluids and oxidative fluids. It is shown that shale is generally rich in water-sensitive components such as clay minerals, acid-sensitive components (like carbonate minerals), alkali-sensitive components (like quartz), oxidative-sensitive components (like organic matter and pyrite), which easily lead to change of rock fabric and mechanical properties owing to water-rock interaction. According to the results, oxidizing acid fluids and oxidizing fracturing fluids should be used to enhance shale gas recovery. This study also indicates that an aspect playing an important role in increasing cumulative gas production is the optimization of the maximum shut-in time based on the change point of the wellhead pressure drop rate. Another important influential factor to be considered is the control of the wellhead pressure considering the stress sensitivity and creep characteristics of the fracture network. [ABSTRACT FROM AUTHOR]

This paper investigates scaled Thermo-Compressors for Multi-Effect Distillation with Thermal Vapor Compression (MED-TVC) desalination plants using Computational Fluid Dynamics (CFD). Initial validation compared CFD predictions with a real MED-TVC plant. Scaled-down Thermo-Compressors exhibited constant entrainment and pressure ratios, validating design scalability. The study expanded to test with compressed air as a practical substitute for steam under identical conditions. Results showed minimal deviation in entrainment and pressure ratios, affirming the feasibility of air testing. To account for temperature differences, a correction factor was introduced for accurate prediction when testing with air. Crucially, we explored substituting hightemperature steam with compressed air for testing. Lowering the air temperature allowed a reduced pressure of 13.12 bar while maintaining equivalent performance ratios compared to steam at 16 bar and 474.7 K. These findings are pivotal for developing small-scale Thermo-Compressor prototypes, facilitating testing with steam or air, and reducing risks and costs associated with full-scale fabrication. The study contributes practical insights for optimizing Thermo-Compressor designs in MED-TVC desalination, presenting compressed air as a viable alternative for efficient and cost-effective testing. [ABSTRACT FROM AUTHOR]

Considering the global fuel crisis, countries have made it imperative to exploit solar energy correctly, which has emerged as the most significant renewable energy source in recent times. Utilizing solar energy to heat the water appropriately to reduce global energy consumption is a challenge most countries face. Research has, therefore, been done extensively to maximize the performance of solar water heating through various applications. Several methods were enumerated and applied in this review study to determine how to enhance the performance of solar water heaters. Eleven techniques for improvement were identified. They are as follows: using nanofluid with phase change material; improving the collector design; coating; lowering the inlet water temperature; switching to a combined system in place of the conventional gas heating system; utilizing a dual glass cover; utilizing the upstream delta wing; utilizing the evacuated tube collector; utilizing the heat exchanger; utilizing the photovoltaic glass unit; and integrating the solar water heater and tubular lighting device into one unit. According to the essential results, using an absorption cooling system with solar power resulted in 34% electricity savings. The absorption system was enhanced, and the COP was raised to 2.75 by implementing the solar water heating system. Solar heating systems combined with PCM achieved the highest efficiency rating of 65%. The dryer system's CO2 emissions were lowered by about 34% when adding a solar collector. The solar water heater's thermal efficiency was increased by 22.53% by a CuO/H2O nanofluid. [ABSTRACT FROM AUTHOR]

Abstract The organic Rankine cycle (ORC) has received a lot of attention in recent years due to its wide application in energy recovery and the use of low‐temperature energy sources. In this article, the energy, exergy, and economic analyses of a high‐temperature ORC (HTORC) in combined heat and power production mode have been performed. In this system, the heating water at 90°C for domestic or industrial purposes is provided in the HTORC condenser. Two working fluids, hexamethyldisiloxane (MM) and siloxane mixture (MDM), have been evaluated and compared in HTORC. The system has been modeled in engineering equation solver software and key parameters such as energy efficiency and exergy of the system, output power, heat‐to‐power ratio, and levelized cost of electricity (LCOE) have been calculated. The energy and exergy efficiency of the system for the two working fluids MM and MDM are equal to 40.8%, 45.6%, 22.45%, and 19.3%, respectively. From the point of view of energy and exergy, the working fluid MM performs better. The LCOE of the system with MM working fluid is equal to 0.5946 US$/kWh, which is slightly higher than MDM working fluid (0.5702 US$/kWh).

This study aims to explore additional fluids beneficial for coastal thermal energy converter (CTEC) operation. Ammonia's thermodynamic properties, characterized by higher condensation temperatures and pressures, demand significantly elevated operating pressures, resulting in a substantial energy load for efficient operation. Thus, exploring alternatives such as R134a becomes crucial, particularly considering its potential as a better working fluid for power generation in a Rankine cycle. The research methodology involves employing computational fluid dynamics (CFD) simulations alongside experimental investigations to examine the performance of an axial turbine concept under different working fluids. The results obtained indicate that R134a is the most appropriate working fluid for an axial turbine within a CTEC, outperforming ammonia, thereby implying significantly better operational efficiency. [ABSTRACT FROM AUTHOR]

We examined how working-fluid properties impact the organic Rankine cycle (ORC) and bottoming cycle in a cogeneration system, and compared the sizes of turbines according to different working fluids. Working fluids R123, R245fa, and R245ca were selected based on factors such as the T-s diagram slope, environmental impact, and safety. The latent heat for vaporization significantly impacted ORC and bottoming-cycle performance. R123 produced the lowest bottoming cycle output of 38.49 MW and an ORC output of 1.95 MW. R245ca required a bigger turbine size, leading to the largest volume flow rate of 20 m3/s at the ORC turbine outlet. The bottoming-cycle output was 38.68 MW and the ORC generated 2.61 MW, which were the highest. R245fa showed promise in terms of compact turbine size due to its smallest volume flow of 14.96 m3/s at the ORC turbine outlet, even though the overall output was 250 kW lower than that of R245ca. [ABSTRACT FROM AUTHOR]

Heat pumps have the potential for several applications across various industrial sectors, showcasing significant promise, especially in sectors such as pulp and paper, food and beverage, chemical, non-metallic minerals, and machinery. Envisioning the near future, there is confidence that heat pumps can achieve temperatures above 200 °C, offering substantial potential for utilization in these sectors. Nevertheless, a crucial aspect for the advancement of high-temperature heat pumps is the selection of the fluid. Fluid selection involves considerations of both thermodynamic efficiency and environmental impact, requiring fluids with zero ODP, negligible GWP, and no PFAS. Moreover, it is essential to consider the risks to human health associated with a specific fluid. Despite extensive research, particularly in the realm of vapour compression heat pumps, choosing the most suitable working fluid for these applications is a complex undertaking. Therefore, this paper conducts a theoretical analysis to evaluate potential fluids with suitable thermodynamic properties for high-temperature heat pumps (HTHPs). The comparative results gleaned from this study provide valuable insights for the comprehensive analysis of fluids, showing promise within temperature ranges dictated by specific applications. The metrics employed in the comparison emphasise the merits of fluids in terms of the overall performance, dimensions, and operating ranges of applicable compressor, heat exchange capacity, transport properties, and safety. One noteworthy finding from the analysis is that maintaining a constant HTHP lift (at 40 K) results in having the highest COP across all fluids when the condensing temperature ranges between 85% and 90% of their respective critical temperatures. According to the results of the analysis, natural fluids, including water and alcohols like ethanol or methanol, emerge as particularly compelling candidates. [ABSTRACT FROM AUTHOR]

• The physical properties of work fluid-lubricant mixture systems were reviewed. • An overview of the classification and characteristics of existing lubricants was presented. • The experimental methods of the physical properties were summarized. • The efficiency and safety improvement studies were compared and summarized. As countries prioritize climate change concerns, promoting the use of new environmentally friendly working fluids has become a common goal for the industry. In thermal systems, lubricants come into contact with these working fluids and directly affect their utilization efficiency. Therefore, investigating the effect of lubricant mixing on the physical properties of process media is essential to promote the adoption of new environmentally friendly working fluids. This paper categorizes and organizes recent research literature on working fluids and lubricants. It was aimed to comprehend the effect of lubricants on the operating characteristics of working fluids. By comparing the research methods and experimental equipment utilized in previous studies, this work analyzes the variation of basic physical properties, including miscibility, solubility, viscosity, and gas-liquid phase equilibrium. In addition, the effects of lubricant mixing in terms of heat exchange characteristics, additives, and material compatibility are also summarized. These findings provide a reference for achieving optimal performance matching of new environmentally friendly working fluid-lubricant combinations. And it will be beneficial for future experimental studies investigating the physical properties associated with working fluid-lubricant mixing systems. [ABSTRACT FROM AUTHOR]

The article discusses the special features of operation of hydroejector vacuum-creating systems. The flow diagram of a two-stage hydroejector vacuum-creating system is described and a calculation algorithm is given. The dependence of the yield of the components of the vapor-gas mixture on the temperature of the working fluid was analyzed and the required heating temperature of the working fluid was determined. A two-stage hydroejector vacuum-creating system was calculated and the dependence of the flow rate of the working fluid on the pressure and power consumption of the pumps was determined. [ABSTRACT FROM AUTHOR]

Energy systems that rely on non-renewable sources like fossil fuels are contributing to climate change by emitting more carbon dioxide. It is crucial to shift towards renewable energy sources such as solar, wind, biomass, and geo-thermal to meet our energy needs. Organic Rankine Cycle (ORC) is a thermodynamic cycle which utilizes an organic fluid with higher molecular mass and lower vaporization temperature than water-like organic fluids such as refrigerants. ORC technology powered by solar energy and waste heat plays an essential role in reducing carbon emission impact. It is becoming one of the most promising approaches to recovering waste heat using regenerative cycles. In this work, ORC driven by solar energy was performed in CYCLE tempo. The heat from solar panels was given as an input to run the ORC power system in the primary circuit. The system involves an evaporator, steam turbines (high pressure and low pressure), a condenser, a feed pump, a waste heat source and R134a as the working fluid for the primary ORC. In the secondary circuit, R245fa was used to produce additional power. Hence, the total power produced by the integration of these two circuits was 5.114 MW and a share of total electricity was utilized for hydrogen production by reversible fuel cells (i) Solid Oxide Electrolysis Fuel Cell (SOEFC) and (ii) Proton Exchange Membrane Fuel Cell (PEMFC). They also compared the results of these fuel cells. The net power of 3.114 MW was available to meet local energy demands as well. [ABSTRACT FROM AUTHOR]

The organic Rankine cycle (ORC) has received a lot of attention in recent years due to its wide application in energy recovery and the use of low‐temperature energy sources. In this article, the energy, exergy, and economic analyses of a high‐temperature ORC (HTORC) in combined heat and power production mode have been performed. In this system, the heating water at 90°C for domestic or industrial purposes is provided in the HTORC condenser. Two working fluids, hexamethyldisiloxane (MM) and siloxane mixture (MDM), have been evaluated and compared in HTORC. The system has been modeled in engineering equation solver software and key parameters such as energy efficiency and exergy of the system, output power, heat‐to‐power ratio, and levelized cost of electricity (LCOE) have been calculated. The energy and exergy efficiency of the system for the two working fluids MM and MDM are equal to 40.8%, 45.6%, 22.45%, and 19.3%, respectively. From the point of view of energy and exergy, the working fluid MM performs better. The LCOE of the system with MM working fluid is equal to 0.5946 US$/kWh, which is slightly higher than MDM working fluid (0.5702 US$/kWh). [ABSTRACT FROM AUTHOR]

A novel thermal integration approach is introduced for a biomass-driven gas turbine power plant that generates electricity, coolant, and liquefied hydrogen. The designed scheme encompassed an organic flash cycle, a bi-evaporator ejector refrigeration unit, a high-temperature water electrolyzer for hydrogen production, a multi-effect desalination cycle for supplying water for electrolysis process, and a Claude cycle for hydrogen gas liquefaction. The designed system's importance comes back to using biomass feedstock as the input fuel and utilizing the hydrogen liquefaction method. In addition to the possibility of deploying the system in remote areas, it provides the opportunity for hydrogen storage in a smaller volume for more accessible storage and transportation. On the other hand, using a comparative method for selecting an environmentally friendly fluid for the heat recovery subsystem is another crucial aspect of the present study from the environmental aspect. It is found that R161 is the appropriate choice among the seven studied working fluids. Subsequently, a comprehensive evaluation of the entire system's thermodynamic and environmental aspects is performed using an intelligent process. By considering energy and exergy efficiencies along with CO2 emissions as the objective functions, a thorough sensitivity analysis and a triple-objective optimization are carried out. Hence, artificial neural networks for the objectives are developed and integrated into the NSGA-II optimization method. Employing LINMAP decision-making, the values of objective are attained, exhibiting 39.6 % for energy efficiency, 36.1 % for exergy efficiency, and 631.7 kg/MWh for CO2 emissions. Considering the optimum solution, the proposed system is capable of producing electricity, cooling, and liquefied hydrogen with capacities of 4526 kW, 1875 kW, and 21.22 m3/day, respectively. Additionally, the scenario yields an exergoenvironmental index of 0.579 and an exergetic stability index of 0.61. and a liquefied hydrogen generation rate of 21.22 m3/day.

This study presents a thermo-economic assessment of three low-global-warming-potential (GWP) substitutes, R1233zd(E), R1234ze(Z) and R1234ze(E), for R245fa used in organic Rankine cycle (ORC) systems, considering two models with different heat sources. The exhaust heat from a diesel generator is served as heat source of Model I, while the waste heat of exhaust and jacket cooling water are used as heat source of Model II. It is noted that the working pressure of R1234ze(E) is much higher than that of R1233zd(E), R1234ze(Z) and R245fa in a fixed evaporation-temperature range. Furthermore, the system using R1234ze(E) has the minimum net power output for Model I, while it turns into the maximum net power output for Model II. In addition, both R1234ze(Z) and R1233zd(E) can be used as good alternative working fluids for R245fa because R1234ze(Z), R1233zd(E) and R245fa have close working pressures, maximum net power outputs, and minimum levelized energy costs. Compared to Model I, LECmin of R1233ed(E) and R1234ze(Z) are reduced by 10.8 % and 9.9 % and PBmin of R1233ed(E) and R1234ze(Z) are reduced by 11.5 % and 10.1 %, respectively, in Model II. However, R1233zd(E) has the highest minimum payback period for both Model I and Model II among the four working fluids investigated.

Various working fluids are applied during geothermal reservoir development, and geothermal reservoir damage induced by contacts between working fluids and reservoir formations are inevitable. Reservoir damage mechanisms, including solid and colloidal plugging, fluid sensitivity, stress sensitivity, and water locking, provide guidance for designing reservoir protection working fluids. In this paper, based on the design principles of reservoir protection working fluids applied in oil–gas reservoirs, four design principles of reservoir protection working fluids are proposed to eliminate potential geothermal reservoir damage for geothermal reservoirs, containing solid-free, facilitated flowback, temporary plugging, and inhibition. Solid-free is achieved by replacing solids with polymers in working fluids. Surfactant and materials with low affinity towards rock surfaces are applied for the facilitated flowback of working fluids from reservoir formations. Temporary plugging is achieved by using temporary plugging materials, some of which are polymers that also apply to solid-free working fluids. Besides, some of the temporary plugging materials, such as surfactant, are applicable for both the facilitated flowback and inhibition of working fluids. The inhibition of working fluids include the inhibition of clay minerals, which can be attributed to clay mineral inhibitors or activity regulators in working fluids, as well as the inhibition of mineral precipitations. This review aims to provide insights for geothermal reservoir protection working fluids, contributing to achieving an efficient development of geothermal resources.

In this study, 143 different working fluids have been analyzed for Rankine and Brayton cycles in terms of performance characteristics such as power, thermal and exergy efficiency, and EFECWOD. The selection of working fluid is a significant consideration in the design of both these cycles, as it can importantly affect the performance and efficiency of the system. As of late, there has been growing interest in investigating the effects of various working fluids on the performance characteristics of these cycles. This article aims to determine the ten best among different working fluids according to the determined criteria using the Technique for Order of Preference by Similarity to Ideal Solution, which is a multi-criteria decision method. In the decision-making process, the importance scale of the analytical hierarchy process was used to determine the weight values of the criteria to be used in the TOPSIS analysis to obtain more accurate results. Artificial Neural Network method is employed to identify the optimal working fluid as well. As a conclusion of this thermodynamic analysis of the performance characteristics for Rankine and Brayton cycles using various working fluids, the Rankine cycle achieved the maximum power of 12,277 kW, the maximum efficiency of 93 %, and the maximum EFECWOD value of 9962 kJ/m3 with hydrogen, helium, and dimethylcarbonate as the respective working fluids. Furthermore, hydrogen exhibits the highest power output of 2493 kW in the Brayton cycle. Nitrogen demonstrates the highest efficiency at 44 %, while R141b achieves the highest exergy efficiency at 98 %. Lastly, the fluid with the highest EFECWOD value is R13, with a measurement of 4932 kJ/m3. • The choice of working fluid is an important consideration in the design of both Rankine and Brayton cycles. • 143 different working fluids have been analyzed for Rankine and Brayton cycles in terms of performance characteristics. • This article aims to determine the ten best among different business fluids according to the determined criteria using TOPSIS. • Artificial Neural Network method is employed to identify the optimal working fluid. • TOPSIS and ANN methods can be used in thermodynamic analysis to find the best working fluids for the performance. [ABSTRACT FROM AUTHOR]

In this research, a modified organic Rankine cycle (ORC) system has been presented and examined. This system incorporates a gas turbine as an additional subsystem to boost the enthalpy of geothermal brine. The primary objective of this study is to perform an economic evaluation of the modified ORC system, wherein a gas turbine is utilized to enhance the quality of geothermal steam. The suggested modified ORC system is particularly well-suited for areas abundant in geothermal resources with low to medium temperatures. It offers a more effective utilization of such resources, resulting in improved efficiency. The study considered 10 different working fluids and 8 types of gas turbines used to heat the geothermal water brine witch, the temperature vary of which varies between 80–130 °C. Various flue gas temperatures behind the heat exchanger, as well as temperatures of the return of the geothermal water to the injection hole, were examined. Based on that, 990 variations of configuration have been analyzed. The research showed that the lowest simple payback time (SPBT) values were achieved for the SGT-800 gas turbine and the working fluid R1336mzz(Z), for example, for an electricity price equal 200 USD/MWh and a natural gas price equal to 0.4 USD/hg, resulting in a SPBT value of 1.45 years. Additionally, for this variant, the dependence of SPBT on the price of electricity and the depth of the geothermal well was calculated; assuming the depth of the geothermal well is 2000 m, SPBT changes depending on the adopted gas prices and so for 150 USD/MWh it is 2.2 years, while at the price of 100 USD/MWh it is 5.5 years. It can be concluded that a decrease in SPBT is observed with an increase in the price of electricity and a decrease in the depth of the geothermal well. The findings of this study can help us to better understand the need to utilize low and medium temperature geothermal heat by using combined cycles (including gas turbines), also from an economic point of view. [ABSTRACT FROM AUTHOR]

The use of wickless heat pipe heat exchangers has been improving a wide range of thermal applications such as solar water heaters. Therefore, more scientific research needs to be conducted to improve its performance. In the present study, a wickless heat pipe heat exchanger test rig has been designed and fabricated to investigate the effect of different parameters on its performance. Two different heat pipe working fluids have been used namely pure water and water with nanoparticles (Al2O3) using different fluid volume ratios (20%,40%,60%,80%, and 100%). The concentrations of the nanoparticles in water range between 1.3 and 7 % wt. For the heat exchanger, various inlet hot air temperatures (50, 55, and 60 ℃) have been tested at the hot side (heat pipe evaporator) whereas the inlet temperature of the cold side (heat pipe condenser) has been maintained at 20 ℃. The effect of airflow Reynolds number has also been examined with a range of 2583-20664. Results showed that the best heat exchanger effectiveness is achieved at a Reynolds number of 10332 and nanoparticles concentration of 7% wt. Also, the use of nanoparticles reduced the thermal resistance in the heat pipe due to the significant reduction in its surface temperature compared to that of pure water. [ABSTRACT FROM AUTHOR]

The Stirling engine, renowned for its high theoretical efficiency, is capable of partaking an active role in the current energy transition. Given its closed-cycle operation, the choice of the working fluid is pivotal in designing the Stirling engine. Dinitrogen tetroxide N2O4 has been extensively investigated in the past, based on the ideal gas thermodynamic model, as a chemically reactive working fluid for Stirling cycles. This molecule reversibly and rapidly dissociates into nitrogen dioxide NO2–and recombines into N2O4–under the influence of thermodynamic transformations throughout the cycle, in accordance with chemical equilibrium. Addressing discrepancies in previous studies, this work aims at assessing a wide range of theoretical chemically reactive gases as working fluids in a Stirling cycle, employing the ideal gas mixture model. The behavior of each reactive fluid is examined throughout the cycle, and the thermodynamic performance is evaluated. Therefore, this work quantifies and analyzes the thermodynamic performance of a chemically reactive Stirling engine. Results indicate a slight increase in the net specific work output with certain reactive fluids, offering a thermal efficiency comparable to that of inert working fluids. In addition, it is emphasized that for chemically reactive working fluids, the isochoric heat exchange within the internal regenerator is incomplete due to chemical reactions, in contrast to the case of inert fluids. To address this, either a supplementary heat source, heat sink, or both are required during the isochoric processes. Furthermore, chemically reactive fluids in the Stirling engine induce irreversibility in the internal regenerator, stemming from heat exchange across a finite temperature difference, penalizing the thermal efficiency of the engine for the majority of reactive fluids studied.

The present study is significant because it can contribute to developing sustainable energy strategies and expanding knowledge about renewable energies in Ecuador, specifically by modeling two modules: the thermal module (parabolic solar collectors and energy storage tank) and the Organic Rankine Cycle (ORC) module. The objective was to determine a region in Ecuador where the thermal module exhibits the highest efficiency for solar collectors. Subsequently, a detailed analysis of the ORC module was conducted, considering the working fluid, boiling temperature, condensation temperature, pinch point temperature, solar collector area, and the collector area-to-energy storage volume ratio (Ac/V). Finally, an economic analysis was performed based on the Net Present Value (NPV), Internal Rate of Return (IRR), and payback period of implementing this type of system. After conducting all the respective analyses in the thermal module, while considering the yearly average meteorological data of ten years (2012–2022), it was determined that due to its meteorological conditions, ambient temperature (14.7 ℃) and solar beam radiation (184.5 W/m2), the efficiency of the collectors in the Andean region of Ecuador is higher. This efficiency is further enhanced by using Therminol VP-1 as the thermal fluid, as it possesses better thermodynamic properties than the other fluids analyzed. Similarly, the ORC module analysis results determined that cyclohexane is the working fluid for the ORC, thereby leading to a higher ORC efficiency (25%) and overall system efficiency (20%). Finally, the system was optimized to maximize the IRR and minimize the Ac/V of the collector for a nominal power of 92 kW. As a result, the optimal operating conditions of the system include a solar collector area of 1600 m2, an energy storage tank volume of 54 m3, an electricity production of 23757 MW/year, a total system efficiency of 22%, an IRR of 15.65% and a payback period of 9.81 years.

The organic Rankine cycle (ORC) power plant is derived from a centrifugal chiller air conditioning system as an alternative to a diesel replacement modular power plant due to its low cost compared to ORC’s manufacture. Biomass is used as a heat source for the power plant to utilize a vast amount of biomass in Indonesia. Research is performed by designing an ORC with biomass that produces around 200 kWe. Simulation done by Microsoft Excel and Reference Fluid Thermodynamic and Transport Properties Database (Lemmon et al., 2013) add-on from the National Institute of Standard Technology (NIST) is used to simulate operating conditions and performance parameters to find a suitable specification of an HVAC system to be modified as an ORC with biomass fuel. Furthermore, based on input from the simulation result and assumptions, other simulation is performed to define operating conditions and types of working fluids, giving the lowest purchase equipment cost. The operating condition analysis of working fluids shows that R123 and R245fa are suitable to be utilized as a potential working fluid for ORC power plants with biomass fuel.

Efficient thermal energy storage and transmission are considered as two of the most significant challenges for decarbonisation in thermal energy utilization. The liquid-gas absorption thermal energy storage/transmission system is promising approach to tackle these challenges, owing to the long-term stability, flexibility in heat/cooling output, and liquid medium. At present, the shortcomings of conventional absorption working fluids have triggered considerable interest in searching for novel working pairs, such as ionic liquids (ILs). However, it is still unknown whether ILs can work effectively in thermal energy transmission with long distance. In this study, the absorption thermal energy storage/transmission systems using IL absorbents are theoretically investigated. modeling frameworks for working pairs screening and performance evaluation are proposed. Results show that the IL-based working pairs present better or comparable performance than conventional working pairs (including H2O/Salts and NH3/Salts). Among the investigated IL-based working pairs, H2O/[EMIM][EtSO4] presents highest COP (around 0.62) and exergy efficiency (around 0.32), and is relatively close to H2O/LiBr. As for energy storage density, H2O/[EMIM][Ac] performs better than H2O/LiBr, presenting 137.4 kWh/m3 with a desorption temperature of 115 °C. The present work provides a straightforward screening of IL absorbents for thermal energy storage and transmission purposes.

This study conducts a thorough analysis of an integrated system that has been specifically engineered to generate power and hydrogen concurrently by utilizing biomass and an Organic Rankine Cycle (ORC). Under its feed fluid heater and heat recovery exchanger, the ORC exhibits a dual-generation capability and is powered by biomass combustion. This research investigates a range of ORC configurations that utilize unique working fluids specifically designed for hydrogen production. A comprehensive thermodynamic model is applied to each fluid. An essential goal is to perform a parametric analysis, wherein the impact of critical parameters on the overall performance of the system is thoroughly examined. In addition, an innovative system comprising an integrated proton membrane exchange electrolyzer and biomass in ORC is presented in this study. An evaluation of the energy and exergy efficiencies of five distinct working fluids (R113, R114, R218, RC318, and R236fa) is conducted. The R113 working fluid exhibited the highest energy and exergy efficiencies, whereas the other fan working fluids were found to possess noteworthy characteristics. The R113 working fluid exhibits exergy and energy efficiencies of 67.15 % and 3.69 %, respectively. In addition, the study reveals valuable information regarding exergy losses in the electrolyzer and evaporator, emphasizing their impact on the generation of electricity. This study clarifies the correlation between fluctuations in temperature within the biomass fluid and the subsequent alterations in power and hydrogen generation, uncovering a compromise characterized by a reduction in energy and exergy efficiency. Furthermore, the research illustrates how escalating the mass flow rates of biomass fluids results in a decline in energy and exergy efficiency while concurrently generating power and hydrogen.

The use of hydrothermal geothermal methods in Enhanced Geothermal Systems (EGS) presents challenges like reduced thermal storage life and high external energy consumption. Due to its stable heat production time and lower external energy demand, CO2 has the potential to be substituted for H2O. The research zone for this study was chosen to be located in the HDR reservoir in the Gonghe Basin of Qinghai. A three-dimensional discrete fracture model based on a thermal-hydraulic-mechanical coupling method is established, where numerical simulations are conducted using COMSOL software. The discussion focuses on the comparison of heat production effects between H2O-EGS and CO2-EGS in different injection and extraction scenarios are discussed. The results indicate that by lowering the injection temperature and increasing the injection rate, the EGS net heat production rate can be increased, but it also accelerates the heat breakthrough time and shortens the reservoir life. Although CO2-EGS has a lower heat extraction rate in the early stage of thermal recovery than H2O-EGS, it has a longer stable heat production time and a more energy-efficient heat production process. Therefore, compared to H2O-EGS, CO2-EGS has more economic and social benefits.

The present study is significant because it can contribute to developing sustainable energy strategies and expanding knowledge about renewable energies in Ecuador, specifically by modeling two modules: the thermal module (parabolic solar collectors and energy storage tank) and the Organic Rankine Cycle (ORC) module. The objective was to determine a region in Ecuador where the thermal module exhibits the highest efficiency for solar collectors. Subsequently, a detailed analysis of the ORC module was conducted, considering the working fluid, boiling temperature, condensation temperature, pinch point temperature, solar collector area, and the collector area-to-energy storage volume ratio (Ac/V). Finally, an economic analysis was performed based on the Net Present Value (NPV), Internal Rate of Return (IRR), and payback period of implementing this type of system. After conducting all the respective analyses in the thermal module, while considering the yearly average meteorological data of ten years (2012-2022), it was determined that due to its meteorological conditions, ambient temperature (14.7 ℃) and solar beam radiation (184.5 W/m²), the efficiency of the collectors in the Andean region of Ecuador is higher. This efficiency is further enhanced by using Therminol VP-1 as the thermal fluid, as it possesses better thermodynamic properties than the other fluids analyzed. Similarly, the ORC module analysis results determined that cyclohexane is the working fluid for the ORC, thereby leading to a higher ORC efficiency (25%) and overall system efficiency (20%). Finally, the system was optimized to maximize the IRR and minimize the Ac/V of the collector for a nominal power of 92 kW. As a result, the optimal operating conditions of the system include a solar collector area of 1600 m², an energy storage tank volume of 54 m2, an electricity production of 23757 MW/year, a total system efficiency of 22%, an IRR of 15.65% and a payback period of 9.81 years. [ABSTRACT FROM AUTHOR]

This paper uses second-order software for evaluating five Stirling engine parameter's effect on its performance to select an appropriate configuration with optimal dimensions for its use in a concentrated solar power plant. Appropriate configuration, heater shape, bundle tube heat exchanger size, and regenerator type and geometry are studied. Results show that alpha type Stirling engine is the most suitable for high temperature differences, U-shaped tubes are advantageous in combining good efficiency and fewer pressure losses. Shortening inner diameter and increasing U-shaped tubes number is a good strategy to increase engine efficiency also an increase in tubes length generates a reduction in engine efficiency. Regarding the regenerator, the wire mesh regenerator presents a good compromise between minimum pressure drop and heat losses and provides better engine efficiency. For its size, better efficiency is obtained for a thicker mesh. [ABSTRACT FROM AUTHOR]

Recovering the waste heat of a marine main engine (M/E) to generate electricity was an environmental way to minimize the carbon dioxide emissions for ships, especially with organic Rankine cycle (ORC) technology. The M/E had variable loads and operating times during voyage cycle, which directly affected the ORC thermodynamic potential. In this paper, a voyage cycle-based waste heat utilization from the M/E was introduced to provide reliable evaluation for proposing and designing ORC. The effect of various M/E loads and operating times on ORC performance among three dry-type substances was analyzed. The environmental impact was presented based on the data from one voyage cycle navigation of objective container ship. The results showed that Cyclohexane was capable of net power while Benzene was more suitable for thermal efficiency. The evaporator and condenser were the main irreversible components of the ORC system and required further optimization. Taking the operational profile into consideration, the evaporation pressures were 922–1248 kPa (Cyclohexane), 932–1235 kPa (Benzene) and 592–769 kPa (Toluene), respectively. During the voyage cycle, the carbon dioxide emissions were 99.68 tons (Cyclohexane), 96.32 tons (Benzene) and 60.99 tons (Toluene), respectively. This study provided certain reference for the design and investigation of ORC application to further improve the energy efficiency for container ship. [ABSTRACT FROM AUTHOR]

A new method is proposed for activating the vibrojet mixing of heterogeneous components in computer-controlled machines that include a two-rotor vibrational drive with kinematic self-excitation of vibration. Simulation of the phase flows in FlowVision software indicates that the two-rotor vibrational mixer is more effective than a single-rotor system. The velocities of the phase flows are determined, and their topological pattern in mixing is presented. [ABSTRACT FROM AUTHOR]

A loop gravity-assisted heat pipe (LGHP) is characterized by passive heat dissipation and extensive application prospect. Dissimilar working fluids give rise to noticeable differences in their working performance (Critical heat flux (CHF)). Consequently, it is of great significance to evaluate the performance of LGHP working fluid for its design. In accordance with the basic theories of CHF and hydrodynamics, the pressure drop models of laminar, smooth turbulence, and completely rough turbulence flows were established, and an extensible two-phase composite property parameter was obtained. On this basis, the physical property parameter of transitional rough turbulent flow was also derived. Finally, as persuasively illustrated by the experimental results, there was almost a linear association between CHFs and the derived physical parameter. As a result, the physical parameters derived in this paper can be employed as favorable criteria for the selection of LGHP working fluid. [ABSTRACT FROM AUTHOR]

The efficiency of multistage filters of the main oil tank (MOT) is analyzed. The efficiency of sequentially installed filters is determined by a power function in which the base is the stage skip factor Win (assuming Win = const for all filtering stages) and the exponent is the number of filtering stages n. Under the operating conditions of the hydraulic system, contaminants continuously enter the system and are removed by the filter. How the change in the transmittance Wi in the process of multistage filtration affects the purity of the oil in the operating system is analyzed. Oil tank filters were upgraded at the K-200-12.8 LMZ turbine unit (station no. 9) at Yuzhnouralskaya GRES. Instead of brass woven meshes, a filter material made of polyamide monofilaments (polyamide filter material) was installed. After the modernization of the coarse and fine filters, the oil became cleaner in the oil-supply system of the K-200-130 turbine unit (station no. 9), the amount of solid particles in it (in samples from the clean compartment of the MOT) with sizes of more than 10 microns decreased by 68 times, and the amount of water in the oil decreased by approximately three times; industrial purity corresponds to the eighth class of GOST 17216-2001. In practice, the operation of coarse and fine filters in one and two stages was also analyzed. When switching from single-stage to two-stage filtration, the purity of the oil became higher, and the amount of solid particles in it with sizes of more than 5 microns decreased by three times, while the amount of water in the oil by approximately 12 times. Increasing the number of filtration stages significantly increases the purity of the filtrate. [ABSTRACT FROM AUTHOR]

This study aims to explore additional fluids beneficial for coastal thermal energy converter (CTEC) operation. Ammonia’s thermodynamic properties, characterized by higher condensation temperatures and pressures, demand significantly elevated operating pressures, resulting in a substantial energy load for efficient operation. Thus, exploring alternatives such as R134a becomes crucial, particularly considering its potential as a better working fluid for power generation in a Rankine cycle. The research methodology involves employing computational fluid dynamics (CFD) simulations alongside experimental investigations to examine the performance of an axial turbine concept under different working fluids. The results obtained indicate that R134a is the most appropriate working fluid for an axial turbine within a CTEC, outperforming ammonia, thereby implying significantly better operational efficiency.

Heat pumps have the potential for several applications across various industrial sectors, showcasing significant promise, especially in sectors such as pulp and paper, food and beverage, chemical, non-metallic minerals, and machinery. Envisioning the near future, there is confidence that heat pumps can achieve temperatures above 200 °C, offering substantial potential for utilization in these sectors. Nevertheless, a crucial aspect for the advancement of high-temperature heat pumps is the selection of the fluid. Fluid selection involves considerations of both thermodynamic efficiency and environmental impact, requiring fluids with zero ODP, negligible GWP, and no PFAS. Moreover, it is essential to consider the risks to human health associated with a specific fluid. Despite extensive research, particularly in the realm of vapour compression heat pumps, choosing the most suitable working fluid for these applications is a complex undertaking. Therefore, this paper conducts a theoretical analysis to evaluate potential fluids with suitable thermodynamic properties for high-temperature heat pumps (HTHPs). The comparative results gleaned from this study provide valuable insights for the comprehensive analysis of fluids, showing promise within temperature ranges dictated by specific applications. The metrics employed in the comparison emphasise the merits of fluids in terms of the overall performance, dimensions, and operating ranges of applicable compressor, heat exchange capacity, transport properties, and safety. One noteworthy finding from the analysis is that maintaining a constant HTHP lift (at 40 K) results in having the highest COP across all fluids when the condensing temperature ranges between 85% and 90% of their respective critical temperatures. According to the results of the analysis, natural fluids, including water and alcohols like ethanol or methanol, emerge as particularly compelling candidates.

The Organic Rankine Cycle (ORC), Supercritical Rankine Cycle (SRC), and Supercritical Brayton Cycle (SBC) are three power cycles that are systematically investigated in the present paper, with particular emphasis on the different types of working fluids that are employed in each cycle and their influence as well as potential opportunities for enhancing the efficiency and thermal performance of power generation systems. The Organic fluids, the refrigerants, and the gasses are all taken into consideration as prospective working fluids in the study. The results demonstrate the distinct advantages and disadvantages of each cycle, with the ORC being best suited for low-temperature recuperation of waste heat, the SRC for operations requiring medium temperatures, and the SBC for high-temperature energy production. This research provides valuable insights regarding the selection of working fluids, considering various factors such as system parameters, environmental impacts, and thermodynamic efficiency. This study also discusses the recent findings on the utilization of organic working fluids, zeotropic mixtures, and nanofluids in these cycles, as well as provides a detailed summary of current trends and developments made in the field. Optimization of different working variables and the utilization of certain changes of working fluids for improving cycle efficiency is also reviewed. This study is motivated by the ongoing energy crisis and the necessity for alternate energy sources, particularly for the transformation of low-quality heat sources. Finally, the potential impact of this research on the scientific community lies in its ability to assist researchers and engineers in making well-informed decisions regarding the selection of the optimal operational fluid for a specific power cycle. Furthermore, this connection between power industries and working fluid selection highlights the relevance of this study to practical applications within the field.

Medium-shallow borehole ground heat exchangers (BGHEs) utilize a burial depth ranging from 200 to 600 m. The heat exchange capacity of a single medium-shallow BGHE is higher than that of a single shallow BGHE. Compared to medium-deep BGHEs, the cost of medium-shallow BGHEs is lower, and both heating and cooling can be achieved, while the former can only be used for heating. However, there is a relative lack of research on the heat transfer characteristics of medium-shallow BGHEs, especially on the influence of the working fluid type on the heat transfer performance of BGHEs. This study aimed to investigate the impact of different working fluids on the performance of medium-shallow BGHEs. First, a heat transfer model for medium-shallow BGHEs was established considering the ground temperature gradient and geothermal heat flow, and its accuracy was validated using experimental test data. Second, the model was used to compare and analyze the effects of various working fluids on the heat transfer performance, pressure loss, and potential environmental benefits of BGHEs. Based on economic analysis, CO2 was determined to be the most suitable working fluid among the organic fluids considered. Finally, the influence of the number of boreholes and the type of working fluid on the heat transfer performance of borehole clusters consisting of 2 and 4 boreholes was analyzed using the superposition principle. The results indicated that CO2 could provide the highest heat transfer among the various working fluids selected in this study, as its heat extraction and heat dissipation were approximately 15% and 12% higher than those achieved by water. Isobutane (R600a) achieved the highest net heat and emission reduction, surpassing water by 66.7% and 73.6%, respectively. Regarding the four boreholes, the outlet temperature of the BGHEs gradually decreased at the end of each heating season. After 10 years of operation, the value decreased by approximately 2 °C. The results in this paper provide a theoretical basis and technical guidance for the rational selection of working fluids and improvements in the heat transfer performance of BGHEs, which could promote the development and application of medium-shallow geothermal energy sources. [ABSTRACT FROM AUTHOR]

The Stirling engine is an external combustion engine that can be utilized in electricity generation. Existing literature indicates that air is less expensive than helium as the working fluid but has the low power and efficiency. Hence, the present updated MATLAB code attempts to use a mixture of air and helium as working fluids or other mixtures of other gases. To this end, this software proposes an experimentally validated nonideal thermodynamic model for a Gama‐type Stirling engine. After validation, a mixing gas of air and helium was used instead of an operating fluid in the thermodynamic model. Finally, three examples were run to demonstrate the software outputs for a hybrid engine. [ABSTRACT FROM AUTHOR]

In this work, we analyzed the operation of oil tank frame filters with baffle plates made of brass nets (GOST 6613–86). Monitoring results showed that when filtering water-cut oil, its strength and corrosion resistance were found to be insufficient, and they do not provide the required oil purity. An appropriate filter material was selected for the frame filters of the oil tanks in the turbine units. For the T-180-210 LMZ turbine unit, the frame filters for fine and coarse cleaning were modernized. For the T-200-130 LMZ turbine unit, the coarse frame filters were modernized. The upgradation of the frame filters brought about a significant improvement in the purity of the turbine oil. Using the method of express analysis of the industrial purity of oils and the water content in them, the diagnostics of the operation of the bearings in the T-200-130 LMZ and T-180-210 LMZ turbine units was performed. Solid contamination curves of the turbine oil were plotted. The source of the large number of mechanical particles in the working fluid in the T-200-130 LMZ turbine unit was found. Turbine oil flooding sources in the T-180-210 LMZ turbine unit were detected. A set of measures was established to improve the efficiency of turbine oil filtration, regular monitoring of cleanliness, and timely diagnostics of power equipment failures, in a bid to significantly increase the service life of turbine units. [ABSTRACT FROM AUTHOR]

The high-temperature heat pump, as a low-carbonization technology, has broad application prospects in replacing boiler heating, reducing carbon dioxide emissions, and improving the energy utilization efficiency. In this paper, the working fluid, cycle process, key equipment (compressor), and application scenarios of high-temperature heat pumps are introduced in detail. Firstly, the research direction of the working fluid is introduced and the existing working fluid substitution is analyzed and summarized. Then, the characteristics of different heat pump cycles such as compression, absorption, and hybrid heat pumps are introduced. In the aspect of key equipment, the application range and research status of different types of compressors are emphatically introduced. Finally, the application scenario of high-temperature heat pumps is prospected. In addition to the application of industrial heating, it is often used for heat storage to improve the regulatory characteristics of the system. The new heat pump electricity storage system has great application potential in the field of renewable energy consumption. Based on the above analysis of high-temperature heat pumps, four development prospects are put forward: low-Global-Warming-Potential (GWP) working fluid; cycles of temperature lift greater than 80 °C; a compressor with better high-temperature performance; and circulation characteristics of heat pump electricity storage. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• Ammonia void fraction in smooth tubes of 8.5 and 15.0 mm has been measured at different orientations and boundary conditions. • No existing single correlation predicts void fraction well for every orientation of the tube. • New single correlation has been proposed for slug and annular two-phase patterns at any orientation. Ammonia is an environment-friendly natural refrigerant and working fluid with negligible global warming and ozone depletion. Nowadays, ammonia is widely used in industrial refrigeration systems, heat pumps and thermal control systems, including heat pipes, loop heat pipes and two-phase mechanically pumped loops. In perspective, "green" ammonia is considered an energy carrier and carbon-free fuel. In two-phase systems, the void fraction is one of the critical factors determining the frictional and local pressure losses, boiling and condensation heat transfer and phase separation. The experimental study of ammonia void fraction in tubes with inner diameters of 8.5 mm and 15 mm is proposed in this paper. The quick-closing valve method has been chosen. Three flow configurations are considered: vertical downward, vertical upward and horizontal. The tests were provided for the two-phase ammonia at a mass velocity of 50...500 kg· m −2s−1, saturation pressure of 15...30 bar, and vapour quality of 0.05...0.30. One hundred and five points have been tested. No existing single correlation predicts the ammonia void fraction well at the considered boundary conditions for at least two orientations in the gravity field. A new single correlation has been proposed based on the Rouhani drift model with the tube inclination angle-dependent distribution parameter allowing the adequate prediction of void fraction in a tube with ammonia flow at horizontal, upward and downward orientations. [ABSTRACT FROM AUTHOR]

A dedicated heat exchanger model is introduced for the optimization of heavy-duty diesel engines. The model is a prerequisite for the execution of CFD simulations, which are used to improve waste heat recovery in these systems. Several optimization methods coupled with different types of working fluids are compared in terms of exergy efficiency and heat exchanger complicity. The three considered optimization methods all lead to significant improvements in the R245fa and R1233zd systems with a comparatively low evaporation temperature. The optimal R245fa system has the highest efficiency increase (77.49%). The cyclopentane system displays the highest efficiency among the optimized ORC (Organic Rankine Cycle) systems, yet achieved by using a much heavier evaporator HEC (Heat Exchanging Core). In contrast, the 96.84% efficiency increase for the optimized R1233zd is achieved with only 68.96% evaporator weight. [ABSTRACT FROM AUTHOR]

Copyright of Journal of South China University of Technology (Natural Science Edition) is the property of South China University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)