Modification of Energy Equation for Homogeneous Cavitation Simulation With Thermodynamic Effect

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Anh Dinh Le ◽  
Junosuke Okajima ◽  
Yuka Iga
Keyword(s):  
Thermodynamic Model ◽  
Saturated Vapor ◽  
Homogeneous Model ◽  
Industrial Applications ◽  
Working Fluid ◽  
Suppression Effect ◽  
Evaporation And Condensation ◽  
Thermodynamic Effect ◽  
Cavitation Region ◽  
Cryogenic Liquids

In industrial applications, cryogenic liquids are sometimes used as the working fluid of fluid machineries. In those fluids, the thermodynamic suppression effect of cavitation, which is normally ignored in water at room temperature, becomes obvious. When evaporation occurs in the cavitation region, the heat is supplied from the surrounding liquid. Hence, the liquid temperature is decreased, and cavitation is suppressed due to the decrease in saturated vapor pressure. Therefore, the performance of the fluid machinery can be improved. Computational fluid dynamics, which involves the use of a homogeneous model coupled with a thermal transport equation, is a powerful tool for the prediction of cavitation under thermodynamic effects. In this study, a thermodynamic model for a homogeneous model is introduced. In this model, the source term related to the latent heat of phase change appears explicitly, and the degree of heat transfer rate for evaporation and condensation can be adjusted separately to suit the homogeneous model. Our simplified thermodynamic model coupled with the Merkle cavitation model was validated for cryogenic cavitation on a two-dimensional (2D) quarter hydrofoil. The results obtained during the validation showed good agreement (in both pressure and temperature profiles) with the experimental data and were better than existing numerical results obtained by other researchers.

Study of Thermodynamic Effect On the Mechanism of Flashing Flow Under Pressurized Hot Water by a Homogeneous Model

2021 ◽  
Author(s):  
Anh Dinh Le
Keyword(s):  
Numerical Method ◽  
Saturated Vapor ◽  
Homogeneous Model ◽  
Temperature Drop ◽  
Numerical Data ◽  
Hot Water ◽  
Two Phase ◽  
Suppression Effect ◽  
Flow Parameters ◽  
Thermodynamic Effect

Abstract The flashing flow in a Moby_Dick converging-diverging nozzle under pressurized hot water from 460.5 K to 483.5 K is simulated using a homogeneous compressible water-vapor two-phase flow model. The kinematic and thermodynamic mass transfer are accessed using the cavitation model based on the Hertz-Knudsen-Langmuir equation. Our simplified thermodynamic model is coupled with the governing equations to capture the phase-change heat transfer. This numerical method proved its reliability through a comparison with available experimental data of flow parameters inside the nozzle. Consequently, the present numerical method shows good potential for simulating the flashing flow under pressurized hot water conditions. The satisfying prediction of averaged flow parameters with a slight improvement compared to reference numerical data is reproduced. The results confirm a noticeable impact of the thermodynamic effect on the mechanism of flashing flow, resulting in a considerable decrease in the flow temperature and the saturated vapor pressure. The flashing non-equilibrium is significantly decreased, forcing the flashing flow to be classified as the usual cavitation behavior and better suited to homogeneous model. While the temperature drop is highly dependent on evaporation, the thermodynamic suppression is influenced by the condensation. The suppression effect, unobserved in water at a lower temperature in previous studies, is noticeable for the pressurized hot water flow characterized by the cavitation mechanism. The vapor void fraction decreased considerably in the radial and axial directions as the water temperature rose to 483.5 K in this study.

Preliminarily Design of Supercritical CO2 Compression Test System

2021 ◽  
Author(s):  
Geng Teng ◽  
Laijie Chen ◽  
Xin Shen ◽  
Hua Ouyang ◽  
Yubo Zhu ◽  
...  
Keyword(s):  
Simulation Model ◽  
Compression Test ◽  
Thermodynamic Model ◽  
Supercritical Co2 ◽  
Operating Performance ◽  
Test System ◽  
Operating Conditions ◽  
Working Fluid ◽  
Stable Operation ◽  
Test Loop

Abstract The centrifugal compressor is the core component of the supercritical carbon dioxide (SCO2) power cycle. It is essential to carry out component-level experimental research on it and test the working characteristics of the compressor and its auxiliary equipment. Building an accurate closed-loop simulation model of closed SCO2 compression loop is a necessary preparation for selecting loop key parameters and establishing system control strategy, which is also an important prerequisite for the stable operation of compressor under test parameters. In this paper, the thermodynamic model of compressor, pre-cooler, orifice plate and other components in supercritical CO2 compression test system is studied, and the simulation model of compression test system is established. Moreover, based on the system enthalpy equations and physical property model of real gas, the compressor, pre-cooler and other components in the test loop are preliminarily designed by using the thermodynamic model of components. Since the operating conditions are in the vicinity of the critical point, when the operating conditions change slightly, the physical properties of the working fluid will change significantly, which might have a greater impact on the operating performance of the system. So the operating performance and the parameter changes of key nodes in the test loop under different operating conditions are calculated, which will provide theoretical guidance for the construction of subsequent experimental loops.

scholarly journals Thermodynamic model for solution behavior and solid-liquid equilibrium in Na-Al(III)-Fe(III)-Cr(III)-Cl-H2O system at 25°C

2018 ◽  
Vol 5 (1) ◽  
pp. 6-16
Author(s):  
Laurent André ◽  
Christomir Christov ◽  
Arnault Lassin ◽  
Mohamed Azaroual
Keyword(s):  
Thermodynamic Model ◽  
Specific Interaction ◽  
Soil Formation ◽  
Ternary Systems ◽  
Industrial Applications ◽  
Mineral Dissolution ◽  
Solution Behavior ◽  
Data Limitations ◽  
Pitzer Formalism ◽  
Solid Liquid

AbstractThe knowledge of the thermodynamic behavior of multicomponent aqueous electrolyte systems is of main interest in geo-, and environmental-sciences. The main objective of this study is the development of a high accuracy thermodynamic model for solution behavior, and highly soluble M(III)Cl3(s) (M= Al, Fe, Cr) minerals solubility in Na-Al(III)-Cr(III)-Fe(III)-Cl-H2O system at 25°C. Comprehensive thermodynamic models that accurately predict aluminium, chromium and iron aqueous chemistry and M(III) mineral solubilities as a function of pH, solution composition and concentration are critical for understanding many important geochemical and environmental processes involving these metals (e.g., mineral dissolution/alteration, rock formation, changes in rock permeability and fluid flow, soil formation, mass transport, toxic M(III) remediation). Such a model would also have many industrial applications (e.g., aluminium, chromium and iron production, and their corrosion, solve scaling problems in geothermal energy and oil production). Comparisons of solubility and activity calculations with the experimental data in binary and ternary systems indicate that model predictions are within the uncertainty of the data. Limitations of the model due to data insufficiencies are discussed. The solubility modeling approach, implemented to the Pitzer specific interaction equations is employed. The resulting parameterization was developed for the geochemical Pitzer formalism based PHREEQC database.

CFD Simulation of a Supersonic Steam Ejector for Refrigeration Application

2016 ◽  
Author(s):  
Liju Su ◽  
Ramesh K. Agarwal
Keyword(s):  
Flow Field ◽  
Cfd Simulation ◽  
Fluid Pressure ◽  
Turbulence Models ◽  
Industrial Applications ◽  
Operating Conditions ◽  
Working Fluid ◽  
Entrainment Ratio ◽  
Ansys Fluent ◽  
Entrainment Velocity

Supersonic steam ejectors are widely used in many industrial applications, for example for refrigeration and desalination. The experimental evaluation of the flow field inside the ejector is relatively difficult and costly due to the occurrence of shock after the velocity of the steam reaches over the sonic level in the ejector. In this paper, numerical simulations are conducted to investigate the detailed flow field inside a supersonic steam (water vapor being the working fluid) ejector. The commercial computational fluid dynamics (CFD) flow solver ANSYS-Fluent and the mesh generation software ANSYS-ICEM are used to predict the steam performance during the mixing inside the ejector by employing two turbulence models, the k-ω SST and the k-ε realizable models. The computed results are validated against the experimental data. The effects of operating conditions on the efficiency of the ejector such as the primary fluid pressure and condenser pressure are studied to obtain a better understanding of the mixing process and entrainment. Velocity contours, pressure plots and shock region analyses provide a good understanding for optimization of the ejector performance, in particular how to increase the entrainment ratio.

Fluid Flow and Boiling Heat Transfer in Mini Channels

2010 ◽  
Author(s):  
M. Venkatesan ◽  
M. Aravinthan ◽  
Sarit K. Das ◽  
A. R. Balakrishnan
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Boiling Heat Transfer ◽  
Industrial Applications ◽  
Tube Diameter ◽  
Working Fluid ◽  
Phase Flow ◽  
Two Phase ◽  
Mini Channels ◽  
Micro Propulsion

Two phase flows in mini channels occur in many industrial applications such as electronic cooling, compact heat exchangers, compact refrigeration systems and in micro propulsion devices. Due to its significance, research on two phase flow in mini channels has become attractive. However, in recent times a controversy exists whether flow in minichannel is different from macro flow because there are still substantial disagreements among various experimental results. In the present study an experimental investigation is carried out for fluid flow and boiling heat transfer characteristics of mini channels with tube diameters ranging from 1–3mm. The tubes were made of SS with water as the working fluid. The variation in friction factor and Nusselt number with decrease in tube diameter for single phase flow was systematically studied. The point of Onset of Nucelate Boiling (ONB) was identified based on wall temperature profile. The effect of heat flux and mass flux on two phase pressure drop with three different tube diameters during sub cooled boiling were investigated. The results reveal that there is an unmistakable effect of tube diameter on fluid friction and onset of boiling during sub cooled boiling in tubes of mini channel dimensions.

Exergy Analyses Applied to an AP-X Process for the Liquefaction of Natural Gas

2012 ◽  
Author(s):  
M. N. Bin Omar ◽  
T. Morosuk ◽  
G. Tsatsaronis
Keyword(s):  
Middle East ◽  
Natural Gas ◽  
Industrial Applications ◽  
Working Fluid ◽  
Total Cost ◽  
Exergetic Analysis ◽  
Liquefaction Process ◽  
The 1960S ◽  
Exergy Analyses ◽  
Thermodynamic Processes

LNG technology has been in use since the 1960s and is constantly evolving. During the last 20 years the total cost of LNG technology has decreased by approximately 30% due to improvements of the liquefaction process and shipping. One of the last developed processes for the liquefaction of the natural gas is the so-called AP-X process that is patented by Air Products and Chemicals, Inc. (US Patent No. 6308521), and is now used for industrial applications in the Middle East. The thermodynamic processes within the components of the AP-X process are complex because a mixture is used as a working fluid. This paper discusses the exergetic analysis of the AP-X process.

Analysis of Energetic, Design and Operational Criteria When Choosing an Adequate Working Fluid for Small ORC Systems

2009 ◽  
Author(s):  
Jorge Faca˜o ◽  
Armando C. Oliveira
Keyword(s):  
Thermal Stability ◽  
Low Temperature ◽  
Heat Source ◽  
Specific Volume ◽  
Saturated Vapor ◽  
Saturation Pressure ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Turbine Inlet ◽  
Cycle Efficiency

Small cogeneration (CHP) systems may lead to a significant reduction of primary energy consumption and harmful emissions. Low temperature Rankine cycles, that can be assisted by solar energy, are a possible solution for producing combined electricity and useful heat. These cycles usually use an organic working fluid. This study presents an analysis of the energetic, design and operational features, that have to be taken into account when choosing an adequate working fluid for these Organic Rankine Cycles (ORC). When using renewable energies as a heat source, like solar or geothermal, the cycles may operate at temperatures between 120°C and 230°C. A system producing 5 kW of electricity was considered as a basis of comparison. Several fluids were analysed: n-dodecane, water, toluene, cyclohexane, n-pentane, HFE7100, R123, isobutane and R245fa. The organic dry fluids, with a positive slope of the saturated vapor curve in a T-s diagram, are in principle desirable for low temperature applications, simplifying turbine design. The degree to which the fluids are drying, is generally related to their molecular weight or molecular complexity. Practical issues, like thermal stability, toxicity, flammability and cost are considered. The thermodynamic cycle efficiency is also important. The saturated vapor specific volume gives an indication of condenser size, which is related to system initial cost. A super-atmospheric (>100 kPa) saturation pressure eliminates infiltration gases, which is important for operational reasons, because infiltration reduces system efficiency. The degree of superheating was optimized for maximum cycle efficiency, with a quadratic approximation method. This optimization makes it possible to decide if it is better to have saturated vapor or superheated vapor at turbine inlet, for a fixed turbine inlet temperature. For a heat source temperature of 120°C, only toluene and isobutane present a small advantage in superheating. It is difficult to find the best fluid, which has simultaneously: high cycle efficiency, low vapor specific volume at turbine outlet, super-atmospheric saturation pressure, good thermal stability, small environmental impact, small toxicity and no flame propagation. From the point of view of cycle efficiency, n-dodecane presents the best performance. However, this fluid presents the highest saturated vapor specific volume (resulting in a larger condenser) and the smallest condenser saturation pressure (resulting in infiltration of gases). The best candidates for the cycle regarding all the aspects are: toluene, cyclohexane and n-pentane. Comparing the three fluids, toluene presents the highest efficiency, the highest impact in environment and the biggest vapor specific volume. N-pentane presents the smallest cycle efficiency and smallest vapor specific volume, but is the unique fluid with super-atmospheric saturation pressure. Cyclohexane is the fluid with lowest impact in environment.

scholarly journals Numerical Investigation to Asses and Optimize Performance of Flat Plate Solar Collector by Using Different Working Fluid

2021 ◽  
Vol 87 (2) ◽  
pp. 44-55
Author(s):  
Yussra Malalah Abdula ◽  
Gadeer Salim ◽  
Salman K
Keyword(s):  
Numerical Model ◽  
Flat Plate ◽  
Solar Collector ◽  
Current Model ◽  
Effective Means ◽  
Industrial Applications ◽  
Working Fluid ◽  
Literature Study ◽  
Maximum Temperatures ◽  
Flat Plate Solar Collector

Sustainable energy becomes an optimal alternative to overcome environmental pollution economical cost of fossil fuel. One of the most effective means to invest solar radiation is flat plate solar collectors. A study carried out to optimize and assess the performance of flat plate solar collector (FPSC) for domestic and industrial applications in the Iraq climate. A 3D numerical model of FPSC has modeled by ANSYS19, CFD tool has been used to investigate thermal transfer through FPSC based on different working fluid. Water, and nanofluid of water/copper nanomaterials were used as working fluid with three different concentrations levels, 0.011 %, 0.055%, and 0,101 %. The velocity of water was 0.3, and 0.5 m/sec respectively. The result of the numerical model was compared with a literature study to prove the reliability of the current model. The result of the current study indicated that, adding Cu nanoparticular to the working fluid enhanced temperatures outlet of FPSC. Also, maximum temperatures can be achieved by reducing the velocity value.

scholarly journals Investigation of heat transfer enhancement in an annular conduit with angled fins using functionalized GNP colloidal suspension

2021 ◽  
Vol 945 (1) ◽  
pp. 012058
Author(s):  
Sayshar Ram Nair ◽  
Cheen Sean Oon ◽  
Ming Kwang Tan ◽  
S.N. Kazi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Power Plants ◽  
Colloidal Suspension ◽  
Industrial Applications ◽  
Point Of View ◽  
Solid Particles ◽  
Working Fluid

Abstract Heat exchangers are important equipment with various industrial applications such as power plants, HVAC industry and chemical industries. Various fluids that are used as working fluid in the heat exchangers such as water, oil, and ethylene glycol. Researchers have conducted various studies and investigations to improve the heat exchanger be it from material or heat transfer point of view. There have been attempts to create mixtures with solid particles suspended. This invention had some drawbacks since the pressure drop was compromised, on top of the occurrence of sedimentation or even erosion, which incurs higher maintenance costs. A new class of colloidal suspension fluid that met the demands and characteristics of a heat exchanger was then created. This novel colloidal suspension mixture was then and now addressed as “nanofluid”. In this study, the usage of functionalized graphene nanoplatelet (GNP) nanofluids will be studied for its thermal conductivity within an annular conduit with angled fins, which encourage swirling flows. The simulation results for the chosen GNP nanofluid concentrations have shown an enhancement in thermal conductivity and heat transfer coefficient compared to the corresponding base fluid thermal properties. The data from this research is useful in industrial applications which involve heat exchangers with finned tubes.

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