Properties Of Working Fluid Research Articles

Reverse design of molecule‐process‐process networks: A case study from HEN‐ORC system

AbstractThe integrated design of the heat exchanger network (HEN) and organic Rankine cycle (ORC) system with new working fluids is a complex optimization problem. It involves navigating a vast design space across working fluid molecules, ORC processes, and networks. In this article, a new two‐stage reverse strategy is developed. The optimal HEN‐ORC configurations and operating conditions, and the thermodynamic properties of the hypothetical working fluid are identified by an equation of state (EOS) free HEN‐ORC model in the first stage. With two developed group contribution‐artificial neural network thermodynamic property prediction models, working fluid molecules are screened out in the second stage from a database containing more than 430,000 hydrofluoroolefins (HFOs). The presented method is employed in two cases, where new working fluids are found. The total annual cost of Case 1 is 12%–22% lower than the literature, and the power output of Case 2 is 5%–8% higher than the literature.

Comparative performance analysis of recuperative helium and supercritical CO₂ Brayton cycles for high-temperature energy systems

This study presents a comprehensive comparative analysis of recuperative Brayton cycles utilizing helium (He) and supercritical carbon dioxide (sCO2) as working fluids for high-temperature power generation, focusing on applications in next-generation concentrated solar power (CSP) systems. Thermodynamic cycle simulations were conducted across a temperature range of 1000 K–2000 K, exploring the effects of low-side pressure (1 bar–100 bar) and expansion ratio (1–5) on key performance indicators. These indicators included thermal efficiency, net specific work output, mass flow rate, volumetric flow rate, and system irreversibilities. Results demonstrate that helium-based Brayton cycles exhibit superior thermal efficiency at high temperatures, reaching up to 65 %, compared to sCO2 cycles, which achieve efficiencies up to 55 %. This advantage stems from helium's higher specific heat capacity and lower pressure drops within the cycle. Conversely, sCO2 cycles demonstrate higher net specific work output due to the fluid's higher density, leading to more compact turbomachinery. The study further investigates the impact of irreversibilities, including pressure losses, leakage losses, and heat transfer losses, on cycle performance. A detailed analysis of multi-stage Brayton cycles incorporating intercoolers and reheaters reveals the potential for further efficiency enhancements in both helium and sCO2 systems. This research provides valuable insights for the design and optimization of high-temperature power generation systems, particularly for next-generation CSP plants. The findings highlight the trade-offs between working fluid properties and cycle configurations, guiding the selection of optimal solutions based on specific application requirements and operating conditions.

500 kW closed cycle gas turbine unit with different working fluids

This article considers a 500 kW closed cycle gas turbine unit. In contrast to open or semi-closed cycles, a closed cycle implies a working fluid circulating continuously within a closed loop. In other words, a working fluid (any working fluid) with the required initial parameters depending on the properties of the selected working fluid is injected into a closed circuit consisting of a compressor, heat exchangers of various purposes and a turbine. A unit with recirculation of combustion products at high pressure can be created based on existing units with minor modifications. Instead of emission into the atmosphere, the exhaust gases enter the high-temperature heat exchanger, where it gives heat to the closed-cycle gas turbine unit. First of all, the application of such units is relevant at compressor stations in conjunction with the gas turbine drive of the blower. The study involved thermal calculation of a closed-cycle gas turbine unit with different working fluids: carbon dioxide, helium and argon. The main objective is to study the advantages and disadvantages of alternative working fluids with their subsequent comparison. Since the main chemical and physical properties of alternative working fluids differ from the classical ones, there is a possibility of obtaining higher parameters of the unit. According to the results of calculations it is established that the most promising working fluid is carbon dioxide, because this can be used at a wide range of temperatures and pressures. It should also be noted that the consumption of carbon dioxide is the lowest compared to other working fluids. The efficiency of such an installation is 28%, but there is a possibility of improvement if regeneration is added.

CFD elucidation of high-pressure subcooled boiling flow towards effects of variable refrigerant properties using OpenFOAM empirical closures

Boiling flow presents a significant concern, especially when a liquid surpasses its boiling point, potentially leading to catastrophic consequences. This research utilizes a two-phase code in the OpenFOAM software to investigate bubble formation during flow boiling. The well-established empirical models for calculating wall heat components were selected based on the operating conditions. The study incorporates experimental data from high-pressure boiling flow (10–30 bars) with variable properties of refrigerant R-12. The predictions reveal underpredictions in void fraction and liquid temperature compared to experimental observations. Significantly, the impact of the subcooling degree on void fraction behaviour is emphasized, and a potential underprediction of the evaporation portion is highlighted, particularly near the wall. Challenges in modelling bubble size distribution are evident through discrepancies in bubble diameter and velocity data, indicating the necessity for further advancements in the code. In summary, this numerical study provides valuable insights into the intricate dynamics of high-pressure subcooled boiling flow, especially when considering variable working fluid properties. Future efforts will focus on refining models for nucleation site density, bubble departure size, and lift-off frequency to enhance prediction accuracy.

Study on the productivity and mechanism of physical field evolution of enhanced geothermal systems under different working fluid types and properties

The injected working fluid conditions directly affect the heat generation efficiency of a stimulated hot dry rock reservoir. Taking exploration well GR1 in the Gonghe Basin of Qinghai as the research object, a stochastic discrete fracture reservoir model was established around the main injection channel, and the productivity variation pattern of the enhanced geothermal system (EGS) and the spatiotemporal evolution mechanism of the reservoir fields were analyzed for CO2 and H2O working fluids. The interaction mechanism between the upper and lower rock formations and the reservoir during the heat mining process was discussed. This study obtained the following findings: (1) when the working fluid was CO2, after 20 years of heat recovery, the injection flow rate, output flow rate, and heat generation efficiency with a working fluid temperature of 60 °C reached 1.22 times, 1.18 times, and 1.92 times those with a working fluid temperature of 35 °C, respectively. The average subsidence and average geostress with the working fluid temperature of 60 °C were low, at only 90.61% and 95.96% of those with the working fluid temperature of 35 °C, respectively. However, high-temperature fluid injection increased flow loss. The changes in the various laws of H2O-EGS were similar to those of CO2-EGS. (2) When the working fluid temperature was 35 °C, after 20 years of heat recovery, the output flow rate and heat generation efficiency with the CO2-EGS reached 12.66 times and 1.28 times those with the H2O-EGS, respectively. However, the flow loss, average subsidence, and average geostress were higher with the CO2-EGS, reaching 6.58 times, 1.14 times, and 1.06 times those with the H2O-EGS, respectively. The patterns in these parameters observed at the other temperatures were similar to those observed at 35 °C. (3) The temperature decrease of the cushion layer was higher than that of the caprock, while the subsidence of the caprock was higher, and this phenomenon was more obvious when the working fluid temperature was lower. The conclusions obtained have important reference significance for the rational selection of working fluids.

Influence of the Anderson Transition on Thermoelectric Energy Conversion in Disordered Electronic Systems

So far, the efficiency of thermoelectric energy conversion remains low compared to traditional technologies, such as coal or nuclear. This low efficiency can be explained by connecting the thermoelastic properties of the electronic working fluid to its transport properties. Such connection also shows that operating close to electronic phase transitions can be an efficient way to boost the thermoelectric energy conversion. In this paper, we analyze themoelectric efficiency close to the metal-insulator Anderson transition. Our results reveal the direct link between the thermoelectric and thermoelastic properties of Anderson-type systems. Moreover, the role of the conductivity critical exponent in the thermoelectric energy conversion is analysed. Finally, we show that relatively large values of the thermolectric figure of merit may be obtained in the vicinity of the Anderson transition.

Design and Analyses of Miniature, Submersible Annular Linear Induction Pump for Test Loops Supporting Development of Advanced Nuclear Reactors

A submersible annular linear induction pump (ALIP) design with an outer diameter of 66.8 mm with appropriate materials is developed for circulating molten lead and alkali liquid metals of sodium and sodium-potassium-78 (NaK-78) alloy in test loops at temperatures up to 500°C. These loops investigate the compatibility of these liquid coolants with nuclear fuel and structure materials to support the development of advanced, Generation IV nuclear reactors. The present ALIP, which employs high-temperature ceramic-insulated coil wires and Hiperco-50 center core and stators, fits in Type 316 stainless steel, 2.5-in. standard schedule 5 pipe. This pipe, considered for the riser tube of the Versatile Test Reactor (VTR) in-pile test cartridge loop, has an inner diameter of 68.8 mm permitting 1.0-mm radial clearance for the present ALIP. An improved equivalent circuit model (ECM) is developed to analyze the performance of the present ALIP design. The accuracy of the model predictions is successfully validated using reported experimental measurements by other investigators for a low liquid sodium flow ALIP at 200°C and 330°C. The improved ECM calculates the performance characteristics of the present ALIP design and investigates the effects of varying the terminal voltage, current frequency, winding wire diameter, center core length, width of the liquid flow annulus, and working fluid properties and temperature on the pump operation. For circulating molten lead, the calculated peak efficiency of the present ALIP design of 6.7% occurs at a flow rate of 9.5 kg/s and pumping pressure of 263 kPa. The calculated peak efficiency for circulating liquid sodium is much higher, 26.3%, and occurs at a lower flow rate of 2.2 kg/s but a higher pumping pressure of 364 kPa. The calculated peak efficiency for circulating NaK-78 (23%) is lower than for sodium and occurs at a lower flow rate and pumping pressure of 1.9 kg/s and 310 kPa, respectively.

Thermo-hydrodynamical optimization of direct absorption solar collector from Stokes to low Reynolds numbers regimes of nanofluid flow

It has been proven that optical properties of base working fluids are significantly enhanced, where very small amount of nanoparticles are exploited. In the current study, numerical investigation of microchannel-based direct absorption flat solar collector (DAFSC) filled with graphite water based nanofluids at various volume fractions in an independent-scattering regime map of nanofluids were taken into account to evaluate thermo-hydrodynamical performance of DAFSC. Furthermore, multi-response optimization of DAFSC including thermodynamics second law efficiency (ηII), thermal efficiency (η(th)), heat loss rate (Q̇(out)), dimensionless temperature difference (θ), pressure drop (Δp), and also cost function (Cost) was carried out by response surface methodology. Fifty four numerical designs proposed by face-centred central composite designs (FCCD) have been used to provide sufficient data to obtain mathematical regression models of response functions in which the significant model's terms were evaluated by analysis of variance. Furthermore, composite desirability function approach was taken into account for multi-response optimization of direct absorption solar collector to maximize ηII, η(th), θ, and to minimize Q̇(out),Δp and Cost functions. Strikingly, the CFD results unveiled that maximum thermal efficiency of DAFSC with black back absorber surface, which was enhanced up to 18% compare to base case, is mainly shape-dependent rather than to that of nanoparticles volume fractions, which can be justified by presence of different dominant heat absorption mechanisms transforming from volumetric absorption for nanofluids to surface one for pure water.

A mechanistic model to predict saturated pool boiling Critical Heat Flux (CHF) in a confined gap

Boiling enables high rates of heat transfer from a surface made possible at a relatively low thermal resistance motivating the use of two-phase cooling for increasingly compact thermal management solutions. However, extreme geometrical confinement of the liquid above the boiling surfaces is known to have detrimental effects on maximum heat transfer rate by inducing premature onset of film boiling. Moreover, previously developed critical heat flux (CHF) models for confined geometries focused on triggering mechanisms associated with unconfined pool boiling and, thus, are not generalizable. This work proposes a new mechanistic model for predicting CHF during boiling within in narrow gap, specifically developed to account for confinement effects on the triggering mechanism. The model postulates that occurrence of CHF coincides with the irreversible growth of a dry spot on the boiling surface. Three competing forces govern the two-phase interface dynamics, namely vapor momentum, surface tension, and hydrostatic forces. Dryout is triggered when the vapor momentum force due to vaporization at the two-phase interface balances the combined surface tension and hydrostatic forces leading to irreversible growth of the dry spot. The present work offers a predictive confined CHF model that accounts for confined boiling surface shape, size, orientation, confinement gap spacing, and working fluid properties, with a single fluid-specific fitting coefficient that represents the ratio of vapor area to the confinement opening area near CHF conditions. Notably, the developed CHF model is also effective in predicting the threshold gap below which confinement reduces pool boiling CHF. The model is compared to 197 experimentally measured confined CHF data points available from 10 studies in the literature that represent 7 different working fluids and a range of boiling surface inclinations and shapes. The model predicts the confinement-reduced CHF values with a root mean square error of 21%, which is less than half of the error compared to all other available predictive models. This clarification of the triggering mechanism and improved prediction accuracy of CHF, as offered by the current study, will enable broader practical system implementation of compact two-phase cooling technologies.

Desorption properties of the R600, R134a and their mixtures in several MOF structures: A molecular dynamics study

The efficiency of organic Rankine cycle is expected to be enhanced via using metal organic heat carriers. Thus, it is important to investigate the properties of organic working fluid in metal organic frameworks (MOFs). In this paper, molecular dynamics method was employed to study the desorption properties of R600, R134a, and their mixtures in MOF-5, IRMOF-16, and MOF-200 structures. The results show that the desorption capacity of pure working fluids are negatively correlated with their molecular size. In mixed refrigerant systems, the desorption of the working medium is competitive, and the higher the proportion of fluorine atoms in the system, the greater the desorption heat in IRMOF-16. It is noteworthy that the behavior of the desorption heat in the other two MOFs is diametrically opposed to this result. The desorption capacity is positively correlated with the average pore size, specific surface area, and porosity of the MOF. The self-diffusion coefficient of the working medium in MOF is inversely proportional to its molecular weight, but directly proportional to its molecular size and to the pore size of MOF.

Study on heat transfer characteristics of ultra-thin flat heat pipes at different liquid filling rates and heat loads

The boiling characteristics of flat heat pipes greatly affect their heat transfer performance, but the research on micro-scale ultra-thin steam chamber is still unclear. The heat transfer performance of ultra-thin plate heat pipe (UTFHP) was investigated by analyzing the boiling heat transfer characteristics under various operating conditions through both theoretical analysis and visualization experiments. The findings demonstrate that the heat transfer process of UTFHP can be classified into three stages based on changes in bubble behavior and heat transfer characteristics. Additionally, we conducted a comprehensive examination of the heat transfer mechanism. The study identifies key factors that affect bubble heat transfer in UTFHP, including temperature, pressure, working fluid properties, and gas–liquid interface area. The impact of heating power on the merging point and turning point of the UTFHP is discussed, while the liquid filling rate is found to have an insignificant effect. The start-up time of the UTFHP is delayed by the liquid bridge, which can be improved by introducing multiple air bubbles and liquid bridges. The study also investigates factors affecting the heat transfer capacity of UTFHP during stable operation, revealing that as heating power increases, the temperature of the evaporator and condenser increases linearly, while the thermal resistance initially increases, decreases, and then increases.

Research and Development of the Oxy-Fuel Combustion Power Cycle for the Combined Production of Electricity and Hydrogen

Modern trends in improving environmental safety have determined the urgency in creating innovative technologies that allow the production of electricity and hydrogen without the emission of harmful substances. However, at the moment, there are not so many technical solutions offering the combined production of these useful products with a high degree of efficiency and environmental friendliness. The transition to oxy-fuel combustion power cycles for the co-production of electricity and hydrogen is a prospective way to decrease carbon dioxide emissions into the atmosphere from the energy sector. To achieve zero emissions, the semi-closed oxy-fuel combustion cycle is combined with a steam methane reformer, which has a high energy efficiency through reducing losses in the steam turbine condenser. The modeling methodology has been described in detail, including the approaches to defining the working fluid properties and mathematical models of the different steam methane reforming plants and the oxy-fuel combustion power plant. According to the results of the thermodynamic analysis of the steam methane reforming plant, it was found that an increase in the temperature from 850 to 1000 °C leads to a decrease in the mass flow fuel by 16.3% due to the shift towards a direct reaction. Moreover, the optimal temperature in the reformer lies in the range of 900–950 °C. A comparison of the energetic and ecological characteristics of various steam methane reformer units showed that the scheme with oxy-fuel combustion is better compared to the scheme with CO2 capture by absorption in monoethanolamine; the efficiency is 6.9% higher and emissions of carbon dioxide are 22 times lower. According to the results of the thermodynamic analysis of a novel oxy-fuel combustion power cycle, it was found that its performance varied regarding the range of electricity production (123.6–370 MW) and hydrogen production (0–10.8 kg/s). The efficiency of the oxy-fuel combustion power cycle varies in the range of 47.2–70.1%. Based on the results of the operation regimes analysis, the energy complex performance map has been developed, allowing identification of the efficiency and working fluid massflow by net power and produced hydrogen massflow.

Thermal performance of a radial-rotating oscillating heat pipe and its application in grinding processes with enhanced heat transfer

Grinding difficult-to-machining materials can generate massive heat. The heat generated by grinding easily accumulates in the grinding zone (the contact area between workpiece and wheel), leading to high temperatures, which harms the grinding quality and efficiency. Radial-rotating oscillating heat pipe (RR-OHP) can achieve high thermal performance and can potentially to apply in grinding with enhanced heat transfer. The RR-OHP is supposed to be designed in the grinding wheel to improve the heat transport ability, in this case, grinding heat can transfer out directly via the grinding wheel. RR-OHP needs to obtain high thermal performance under radial rotations, while the related research is still insufficient. In this paper, the influence of centrifugal acceleration (0 – 1620 m/s2), working fluid properties (methanol, DI water), and heat flux (1.5 × 104 – 4 × 104 W/m2) on the heat transport capacity are studied. A prototype of a grinding wheel combined with RR-OHPs is developed. A grinding simulation by the wheel is built to demonstrate the enhanced heat transfer of RR-OHPs in grinding process. Results show that the increment of heat flux and centrifugal acceleration can improve the thermal performance of RR-OHPs. The thermal resistance of RR-OHP filled with methanol is smaller than that of RR-OHP filled with DI water. In addition, under the condition that grinding speed of 12 m/s, infeed speed of 360 mm/min, and 1 mm depth of cut, the grinding wheel embedded with 16 RR-OHPs can transfer out 79% of total heat and control the temperature under 262 °C, based on the grinding simulation. On the contrary, the grinding wheel without RR-OHPs transfers only 34% of the total grinding heat, and the temperature reaches up to 766 °C.

Thermo-economic performance limit analysis of combined heat and power systems for optimal working fluid selections

In previous works, we have proposed the thermodynamic performance limit analysis methodology for the organic Rankine cycle for analyzing the impact of working fluid properties on system performance. Here the concept is extended to the thermo-economic performance limits, and is applied to a combined heat and power system based on an organic Rankine cycle. Working fluids are characterized with 8 characteristic thermodynamic and transport properties based on a corresponding state model and a residual entropy scaling approach. The 8 fluid characteristic properties along with 3 system operational parameters are optimized using a multi-objective genetic algorithm; a Monte Carlo algorithm is further adopted to avoid sub-optimal convergences. As the result, the performance limits could be well represented by the trade-off (Pareto front) between the maximized thermal efficiency and minimized payback period. The impact of the fluid characteristic properties on both thermodynamic and economic targets is investigated and ultimately guided the choice of working fluids: low molar mass, low thermal conductivity scaling factor, high viscosity scaling factor and high critical pressure are always preferred. "Wet" working fluid is preferred for a high thermal efficiency while "dry" working fluid is favored for a short payback period. Critical temperature has the most profound impact, while ideal gas isobaric heat capacity and acentric factor have negligible impacts. The choice of working fluid, system design (e.g., recuperative effectiveness) and system operational parameters (e.g., evaporation temperature) highly depends on the given hot sources and the preferences to the thermodynamic and economic targets.

Review on Mono and Hybrid Nanofluids: Preparation, Properties, Investigation, and Applications in IC Engines and Heat Transfer

Nano fluids are widely used today for various energy-related applications such as coolants, refrigerants, and fuel additives. New coolants and design modifications are being explored due to renewed interest in improving the working fluid properties of heat exchangers. Several studies have investigated nanofluids to enhance radiator and heat exchanger performance. A new class of coolants includes single, binary, and tertiary nanoparticle-based hybrid nano-coolants using ethylene glycol/deionized water combinations as base fluids infused with different nanoparticles. This review article focuses on the hydrothermal behavior of heat exchangers (radiators for engine applications) with mono/hybrid nanofluids. The first part of the review focuses on the preparation of hybrid nanofluids, highlighting the working fluid properties such as density, viscosity, specific heat, and thermal conductivity. The second part discusses innovative methodologies adopted for accomplishing higher heat transfer rates with relatively low-pressure drop and pump work. The third part discusses the applications of mono and hybrid nanofluids in engine radiators and fuel additives in diesel and biodiesel blends. The last part is devoted to a summary of the research and future directions using mono and hybrid nanofluids for various cooling applications.

DESIGN OF HELICAL TYPE STEAM GENERATOR FOR EXPERIMENTAL POWER REACTOR

Reaktor Daya Eksperimental (RDE) is a high-temperature gas-cooled reactor (HTGR) for electricity generation, heat generation, and hydrogen production by Batan. Empirical and numerical calculations are needed to strengthen the existing design. The numerical method by computational fluid dynamic (CFD) analyzes temperature distribution and pressure drop along the pipe. The Batan RDE steam generator design has a seven-layer helical pipe model, while this research uses a one-layer helix pipe. In empirical calculations, the heat transfer region has three sections; single-phase liquid, two-phase, and single-phase vapor heat transfer. In numerical calculations, apply the assumption of constant heat flux and constant working fluid properties. The results of empiric calculations data showed that the helical pipe height was 3.98 m, shorter than the Batan design, which is 4.97 m. This considerable difference due to empirical calculations did not cover the safety factor. The results of numerical calculations show that in the single-phase, empiric calculation data were acceptable since the different values of numerical calculations for empiric calculations data were below 10%. Meanwhile, the case of the two-phase numerical calculations is not satisfactory and needs further research to obtain optimal results.

Review of the State of the Art for Radial Rotating Heat Pipe Technology Potentially Applicable to Gas Turbine Cooling

Improvements in the efficiency of gas turbine engines over the decades have led to increasing turbine inlet temperatures. This, in turn, has resulted in the need to cool the turbine blades themselves to avoid damage to them. While air-cooling and film-cooling methods have been adopted as the primary methods of gas turbine blade cooling, the heat pipe cooling method shows greater potential in terms of temperature uniformity, maximum allowable gas temperature, reliability, and durability. This paper reviews the state-of-the-art research activities on the radial rotating heat pipes (RRHP) potentially applicable to gas turbine cooling. The emergence of the heat-pipe-cooled turbine blade concept, designs, and variants will be described at the beginning. Then the paper will review the literature addressing the heat transfer performance of RRHPs, and the effects on them of rotational forces, working fluid properties, and geometry, as well as operational limits they may be subject to. Additionally, the effects of secondary flow and numerical simulation of RRHPs will be reviewed and discussed. It can be concluded that fundamental studies are still needed for the understanding of the RRHP, as well as the improvement of numerical models.

Numerical investigation of working fluid properties impacting performance of magnetocaloric cooling device

This paper presents a virtual experiment test stand of a magnetocaloric cooling device that utilizes the magnetocaloric effect (MCE). The virtual test stand is based on a comprehensive and novel numerical model that integrates pumps, check valves, tanks, and a gadolinium porous bed in a time-dependent system. The MCE is achieved by cyclic stages of magnetization and demagnetization of the porous bed of an active magnetic regenerator (AMR) and is synchronized with flow of a working fluid. The virtual test stand is utilized to investigate the influence of the properties of the working fluid on the performance of the cooling device. The isolated and combined effects of the density, specific heat, viscosity, and thermal conductivity of the working fluid are analyzed using the Design of Experiments (DOE) approach. The response variables considered are the temperature span between the cold and hot tanks and the available cooling load of the cold tank. The conducted study has revealed that the temperature span is majorly influenced by the isolated effects of thermal conductivity, specific heat, and density, whereas the cooling power is influenced by isolated and combined effects of most of the properties of the working fluid. The virtual test stand developed and the results achieved can be used to define an optimal working fluid and operational setting, such as the cycle frequency, mass flow, and bed structure of a real device. • Virtual test stand of a magnetocaloric cooling device was developed. • The influence of thermophysical properties of the working fluid was investigated. • DOE was used to study their isolated and coupled effects. • Temperature span was mostly influenced by the isolated effects of thermal properties. • Cooling performance was also influenced by the coupled effects.

Расчет конструктивных параметров мультицилиндрового теплового генератора на основе течения Куэтта–Тэйлора

Direct conversion of wind energy into heat is a relevant direction for the development of alternative heat power engineering. The paper considers an efficient wind heat generator that consists of two rotors nested in each other's annular gaps and forming a system of cylindrical coaxial annular channels filled with a viscous working fluid. Depending on the properties of the working fluid, the velocity of the rotors, the number of annular channels and their geometry, there are combinations of parameters for the optimal design of the heat generator. The proposed method for selecting the design parameters of coaxial rotors makes it possible to directly select the optimal design of rotors for a given power of the heat generator and the properties of a viscous working fluid. The design of the multi-cylinder system of the heat generator, which uses the annular Couette–Taylor flow, is presented in the form of an equivalent single annular gap, which made it possible to generalize the results of investigations carried out with different working fluids under various conditions, in the form of a single dependence of the dimensionless power of the heat generator on the number Reynolds. The obtained dependence is well approximated by a linear function in the experimentally studied range of Reynolds numbers. An algorithm for calculating the geometric design parameters of a multi-cylinder annular system is proposed. As an example, calculations of the structural dimensions of nine variants of heat generators for three power values are given: 10 kW, 20 kW and 50 kW.

The role and impact of costing methods in determining the viability of energy systems

• The concept and influnce of choosing a costing mehod is put forward. • The BCR method is compared with the LCOE method to familiarize with a sustainable energy economics approach. • Case study of a heat pump was carried out to choose a suitable working fluid. • The results have shown that the BCR method is more feasible and adaptable as compared to LCOE. Costing method plays a vital role in assuring the feasibility of any project. When we talk about energy systems, many factors influence the decision making process, which are directly or indirectly associated with socio-enviro-economic benefits. While talking about the associated benefits, appropriate costing approach can significantly absorb the concerned factors. In this context, economics is one of the relevant factors which comes to mind while choosing a right working fluid for thermodynamic cycles if consider this as a test case. Although a wide variety of relevant approaches is available. However, the literature points out the shortcomings, validity and limitations of available costing methods. Out of them, levelized cost of energy (LCOE) is considered a well-known costing method, which has received many criticisms in this regard. On the other hand, this work proposes the concept of employing benefit-cost ratio (BCR) analysis as an alternative costing tool to select suitable working fluids for thermodynamic cycles. This work compares and evaluates the effectiveness, openness and understanding of both methods. For in-depth analysis, a heat pump system as a case study is adopted to select the suitable working fluid. The study is further supported by considering multiple scenarios. Results of this study have shown very interesting outcomes, where one method lagging the other and vice versa. The results have shown the impact of thermophysical properties of different working fluids and their influence on overall economics of the system.