scholarly journals Modeling of thermodynamic processes using the properties of matter presented in the form of spreadsheets

2021 ◽  
Vol 2057 (1) ◽  
pp. 012050
Author(s):  
E R Ramazanov ◽  
A A Kosoy
Keyword(s):  
Combustion Chamber ◽  
Ideal Gas ◽  
Pure Oxygen ◽  
Working Fluid ◽  
Thermodynamic Cycles ◽  
Ideal Gases ◽  
Other Substances ◽  
Polytropic Equation ◽  
Computing Module ◽  
Thermodynamic Processes

Abstract New thermodynamic cycles are developed in which the working fluid used cannot be considered as an ideal gas. This applies to oxy-fuel combustion cycles. In these cycles, oxygen is separated from the air prior to combustion. The combustion chamber is supplied with fuel and pure oxygen. The required temperature at the outlet of the combustion chamber is achieved by supplying some other substances from which it is easy to separate the CO2 formed during the combustion of the fuel. Commonly, CO2, or H2O, or their mixture is used as such substances. Thus, there are no exotic substances in the composition of the working fluid, but such a range of parameters is chosen for such cycles that the working fluid at certain points of the cycle can be both gaseous and liquid, or in a supercritical state. To model thermodynamic processes in such cycles, it is unacceptable to use the polytropic equation of ideal gases. A technique for integrating differential equations describing the state of the working fluid is proposed. This technique is based on the presentation of the thermodynamic properties of pure substances that make up the working fluid in the form of spreadsheets. The proposed technique is implemented in a software-computing module.

scholarly journals Large Eddy Simulations of Strongly Non-Ideal Compressible Flows through a Transonic Cascade

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 772
Author(s):  
Jean-Christophe Hoarau ◽  
Paola Cinnella ◽  
Xavier Gloerfelt
Keyword(s):  
Compressible Flows ◽  
Flow Behavior ◽  
Pressure Ratio ◽  
Organic Rankine Cycle ◽  
Ideal Gas ◽  
Operating Conditions ◽  
Large Eddy Simulations ◽  
Working Fluid ◽  
Viscous Effects ◽  
Large Eddy

Transonic flows of a molecularly complex organic fluid through a stator cascade were investigated by means of large eddy simulations (LESs). The selected configuration was considered as representative of the high-pressure stages of high-temperature Organic Rankine Cycle (ORC) axial turbines, which may exhibit significant non-ideal gas effects. A heavy fluorocarbon, perhydrophenanthrene (PP11), was selected as the working fluid to exacerbate deviations from the ideal flow behavior. The LESs were carried out at various operating conditions (pressure ratio and total conditions at inlet), and their influence on compressibility and viscous effects is discussed. The complex thermodynamic behavior of the fluid generates highly non-ideal shock systems at the blade trailing edge. These are shown to undergo complex interactions with the transitional viscous boundary layers and wakes, with an impact on the loss mechanisms and predicted loss coefficients compared to lower-fidelity models relying on the Reynolds-averaged Navier–Stokes (RANS) equations.

A Numerical Study of Unsteady Natural Convection in a Rectangular Enclosure: The Effect of Compressibility

2004 ◽  
Author(s):  
K. M. Akyuzlu ◽  
Y. Pavri ◽  
A. Antoniou
Keyword(s):  
Mathematical Model ◽  
Stokes Equations ◽  
Numerical Study ◽  
Vertical Wall ◽  
Ideal Gas ◽  
Working Fluid ◽  
Two Dimensional ◽  
Algebraic Equations ◽  
Rectangular Enclosure ◽  
Circulation Patterns

A two-dimensional, mathematical model is adopted to investigate the development of buoyancy driven circulation patterns and temperature contours inside a rectangular enclosure filled with a compressible fluid (Pr=1.0). One of the vertical walls of the enclosure is kept at a higher temperature then the opposing vertical wall. The top and the bottom of the enclosure are assumed insulated. The physics based mathematical model for this problem consists of conservation of mass, momentum (two-dimensional Navier-Stokes equations) and energy equations for the enclosed fluid subjected to appropriate boundary conditions. The working fluid is assumed to be compressible through a simple ideal gas relation. The governing equations are discretized using second order accurate central differencing for spatial derivatives and first order forward finite differencing for time derivatives where the computation domain is represented by a uniform orthogonal mesh. The resulting nonlinear equations are then linearized using Newton’s linearization method. The set of algebraic equations that result from this process are then put into a matrix form and solved using a Coupled Modified Strongly Implicit Procedure (CMSIP) for the unknowns (primitive variables) of the problem. A numerical experiment is carried out for a benchmark case (driven cavity flow) to verify the accuracy of the proposed solution procedure. Numerical experiments are then carried out using the proposed compressible flow model to simulate the development of the buoyancy driven circulation patterns for Rayleigh numbers between 103 and 105. Finally, an attempt is made to determine the effect of compressibility of the working fluid by comparing the results of the proposed model to that of models that use incompressible flow assumptions together with Boussinesq approximation.

scholarly journals Thermodynamic Analysis of Irreversible Desiccant Systems

Entropy ◽  
2018 ◽  
Vol 20 (8) ◽  
pp. 595 ◽  
Author(s):  
Niccolò Giannetti ◽  
Seiichi Yamaguchi ◽  
Andrea Rocchetti ◽  
Kiyoshi Saito
Keyword(s):  
Control Volume ◽  
Ideal Gas ◽  
Maximum Efficiency ◽  
Working Fluid ◽  
Specific System ◽  
Equilibrium Relationship ◽  
Working Medium ◽  
Vapour Mixture ◽  
Energy Balances ◽  
Relationship Of

A new general thermodynamic mapping of desiccant systems’ performance is conducted to estimate the potentiality and determine the proper application field of the technology. This targets certain room conditions and given outdoor temperature and humidity prior to the selection of the specific desiccant material and technical details of the system configuration. This allows the choice of the operative state of the system to be independent from the limitations of the specific design and working fluid. An expression of the entropy balance suitable for describing the operability of a desiccant system at steady state is obtained by applying a control volume approach, defining sensible and latent effectiveness parameters, and assuming ideal gas behaviour of the air-vapour mixture. This formulation, together with mass and energy balances, is used to conduct a general screening of the system performance. The theoretical advantage and limitation of desiccant dehumidification air conditioning, maximum efficiency for given conditions constraints, least irreversible configuration for a given operative target, and characteristics of the system for a target efficiency can be obtained from this thermodynamic mapping. Once the thermo-physical properties and the thermodynamic equilibrium relationship of the liquid desiccant mixture or solid coating material are known, this method can be applied to a specific technical case to select the most appropriate working medium and guide the specific system design to achieve the target performance.

Using Excel for the Thermodynamic Analysis of Air-Standard Cycles and Combustion Processes

2009 ◽  
Author(s):  
Amir Karimi
Keyword(s):  
Engineering Students ◽  
Solution Process ◽  
Ideal Gas ◽  
Power Cycles ◽  
Thermodynamic Cycles ◽  
Specific Heats ◽  
Property Evaluation ◽  
Difficult Time ◽  
Parametric Studies ◽  
Combustion Processes

In an undergraduate course or a course-sequence in thermodynamics mechanical engineering students are introduced to air-standard power cycles, refrigeration cycles, and the fundamentals of combustion processes. The analysis of air-standard thermodynamic cycles or solving problems involving combustion processes requires the evaluation of thermodynamic properties either from ideal gas tables or equations developed based on the assumption of constant specific heats. Many students have a difficult time to distinguish the differences between the two property evaluation methods. Also, solving problems involving power and refrigeration cycles or parametric studies of combustion processes involve several steps of property evaluation and some steps require interpolation of data listed in the thermodynamic property tables. Also solution to problems requiring trial and error iterative procedure makes the solution process tedious and time consuming, if it is done manually. This paper provides several examples to demonstrate the effectiveness of Excel in solving problems involving air-standard cycles and combustion processes.

scholarly journals Mixedness Measurement in Gaseous Jet Injection

2017 ◽  
Author(s):  
Martia Shahsavan ◽  
John Hunter Mack
Keyword(s):  
Combustion Chamber ◽  
Direct Injection ◽  
Premixed Combustion ◽  
Working Fluid ◽  
Scalar Dissipation ◽  
Jet Injection ◽  
Direct Injection Engines ◽  
Comprehensive Method ◽  
Mixture Homogeneity ◽  
Crucial Parameter

In turbulent non-premixed combustion applications, such as diesel and direct injection engines, the mixedness of the injected fuel with oxygen and the working fluid inside the combustion chamber is a crucial parameter since it can significantly affect the ignition behavior. In this study, a comprehensive method for investigating mixedness, defined by spatial variation and scalar dissipation, is implemented to assess the turbulent injection of hydrogen into mixture of oxygen with nitrogen, argon, and xenon. Evaluating both criteria reflects the mixture homogeneity as well as local gradients, which aids in discriminating scalar distributions with identical homogeneity and different patterns. The results indicate that replacing nitrogen with argon as the working fluid can provide more suitable ignition conditions for the hydrogen jet.

scholarly journals Equation of state in form which relates mol fraction and molarity of two (or more) component thermodynamic system consisted of ideal gases, and it’s applications

2010 ◽  
Vol 14 (3) ◽  
pp. 859-863
Author(s):  
Marko Popovic
Keyword(s):  
Equation Of State ◽  
Special Relativity ◽  
Mole Fraction ◽  
Relativistic Effects ◽  
Thermodynamic System ◽  
Ideal Gases ◽  
Other Substances ◽  
Temperature And Pressure ◽  
Insight Into

Most people would face a problem if there is a need to calculate the mole fraction of a substance A in a gaseous solution (a thermodynamic system containing two or more ideal gases) knowing its molarity at a given temperature and pressure. For most it would take a lot of time and calculations to find the answer, especially because the quantities of other substances in the system aren?t given. An even greater problem arises when we try to understand how special relativity affects gaseous systems, especially solutions and systems in equilibrium. In this paper formulas are suggested that greatly shorten the process of conversion from molarity to mole fraction and give us a better insight into the relativistic effects on a gaseous system.

Thermal Model of a Thin Film Pulsed Pyroelectric Generator

2016 ◽  
Author(s):  
Nicholas R. Jankowski ◽  
Andrew N. Smith ◽  
Brendan M. Hanrahan
Keyword(s):  
Thin Film ◽  
Power Generation ◽  
Energy Conversion ◽  
High Speed ◽  
High Energy ◽  
High Energy Density ◽  
Working Fluid ◽  
Film Material ◽  
Thermodynamic Cycles ◽  
The Impact

Recent high energy density thin film material development has led to an increased interest in pyroelectric energy conversion. Using state-of-the-art lead-zirconate-titanate piezoelectric films capable of withstanding high electric fields we previously demonstrated single cycle energy conversion densities of 4.28 J/cm3. While material improvement is ongoing, an equally challenging task involves developing the thermal and thermodynamic process though which we can harness this thermal-to-electric energy conversion capability. By coupling high speed thermal transients from pulsed heating with rapid charge and discharge cycles, there is potential for achieving high energy conversion efficiency. We briefly present thermodynamic equivalent models for pyroelectric power generation based on the traditional Brayton and Ericsson cycles, where temperature-pressure states in a working fluid are replaced by temperature-field states in a solid pyroelectric material. Net electrical work is then determined by integrating the path taken along the temperature dependent polarization curves for the material. From the thermodynamic cycles we identify the necessary cyclical thermal conditions to realize net power generation, including a figure of merit, rEC, or the electrocaloric ratio, to aid in guiding generator design. Additionally, lumped transient analytical heat transfer models of the pyroelectric system with pulsed thermal input have been developed to evaluate the impact of reservoir temperatures, cycle frequency, and heating power on cycle output. These models are used to compare the two thermodynamic cycles. This comparison shows that as with traditional thermal cycles the Ericsson cycle provides the potential for higher cycle work while the Brayton cycle can produce a higher output power at higher thermal efficiency. Additionally, limitations to implementation of a high-speed Ericsson cycle were identified, primarily tied to conflicts between the available temperature margin and the requirement for isothermal electrical charging and discharging.

scholarly journals Mathematical Model of Small-Volume Air Vessel Based on Real Gas Equation

Water ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 530 ◽  
Author(s):  
Weixiang Ni ◽  
Jian Zhang ◽  
Lin Shi ◽  
Tengyue Wang ◽  
Xiaoying Zhang ◽  
...  
Keyword(s):  
Water Depth ◽  
Small Volume ◽  
Pressure Oscillation ◽  
State Equation ◽  
Ideal Gas ◽  
Pipeline System ◽  
Real Gas ◽  
Polytropic Equation ◽  
Real Gas Equations ◽  
Ideal Gas Model

The gas characteristics of an air vessel is one of the key parameters that determines the protective effect on water hammer pressure. Because of the limitation of the ideal gas state equation applied for a small-volume vessel, the Van der Waals (VDW) equation and Redlich–Kwong (R–K) equation are proposed to numerically simulate the pressure oscillation. The R–K polytropic equation is derived under the assumption that the volume occupied by the air molecules themselves could be ignored. The effects of cohesion pressure under real gas equations are analyzed by using the method of characteristics under different vessel diameters. The results show that cohesion pressure has a significant effect on the small volume vessel. During the first phase of the transient period, the minimum pressure and water depth calculated by a real gas model are obviously lower than that calculated by an ideal gas model. Because VDW cohesion pressure has a stronger influence on the air vessel pressure compared to R–K air cohesion pressure, the amplitude of head oscillation in the vessel calculated by the R–K equation becomes larger. The numerical results of real gas equations can provide a higher safe-depth margin of the water depth required in the small-volume vessel, resulting in the safe operation of the practical pumping pipeline system.

Energy storage analysis of CO2 in MOF-74 and UIO-66 nanoparticles: A molecular simulation study

2019 ◽  
Vol 33 (18) ◽  
pp. 1950196 ◽  
Author(s):  
Qiang Wang ◽  
Shengli Tang
Keyword(s):  
Energy Storage ◽  
Adsorption Capacity ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Working Fluid ◽  
Thermodynamic Cycles ◽  
Different Temperatures ◽  
Energy Storage Properties ◽  
Metal Organic ◽  
Adsorption Of Co

Adding porous nanoparticles into fluid can modify the energy storage properties of working fluid in the thermodynamic cycles. The adsorption capacity and thermal energy storage of CO2 in MOF-74 and UIO-66 at different temperatures and pressures are investigated in this paper via molecular simulations. The results denote that the adsorption of CO2 in the two studied metal organic frameworks (MOFs) differ from each other due to the different structures. The adsorption capacity of CO2 in MOF-74 is larger than that in UIO-66. However, the desorption heat of CO2 in MOF-74 is lower than that in UIO-66. Also, UIO-66 impacts more than MOF-74 on the thermal energy storage property of CO2.

scholarly journals Towards Thermodynamics with Generalized Uncertainty Principle

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Ahmed Farag Ali ◽  
Mohamed Moussa
Keyword(s):  
Quantum Gravity ◽  
Uncertainty Principle ◽  
Generalized Uncertainty Principle ◽  
Ideal Gas ◽  
Considerable Change ◽  
Heisenberg Uncertainty Principle ◽  
Ideal Gases ◽  
Quantum Gravity Effect ◽  
Photon Gas ◽  
Heisenberg Uncertainty

Various frameworks of quantum gravity predict a modification in the Heisenberg uncertainty principle to a so-called generalized uncertainty principle (GUP). Introducing quantum gravity effect makes a considerable change in the density of states inside the volume of the phase space which changes the statistical and thermodynamical properties of any physical system. In this paper we investigate the modification in thermodynamic properties of ideal gases and photon gas. The partition function is calculated and using it we calculated a considerable growth in the thermodynamical functions for these considered systems. The growth may happen due to an additional repulsive force between constitutes of gases which may be due to the existence of GUP, hence predicting a considerable increase in the entropy of the system. Besides, by applying GUP on an ideal gas in a trapped potential, it is found that GUP assumes a minimum measurable value of thermal wavelength of particles which agrees with discrete nature of the space that has been derived in previous studies from the GUP.

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