Isobaric Heat Capacity of Propane over a Wide Range of Temperature and Pressure.

1952 ◽  
Vol 44 (12) ◽  
pp. 2894-2897 ◽  
Author(s):  
John H. SeiFarth ◽  
Joseph Joffe
Keyword(s):  
Heat Capacity ◽  
Isobaric Heat Capacity ◽  
Wide Range ◽  
Temperature And Pressure

scholarly journals АНАЛИТИЧЕСКОЕ ОПРЕДЕЛЕНИЕ ИСТИННОЙ УДЕЛЬНОЙ ИЗОБАРНОЙ ТЕПЛОЁМКОСТИ КОМПОНЕНТ ВОЗДУХА И ПРОДУКТОВ СГОРАНИЯ С УЧЁТОМ ВЛИЯНИЯ ТЕМПЕРАТУРЫ И ДАВЛЕНИЯ И ЭФФЕКТА ТЕРМИЧЕСКОЙ ДИССОЦИАЦИИ

2019 ◽  
pp. 4-17
Author(s):  
Майя Владимировна Амброжевич ◽  
Михаил Анатольевич Шевченко
Keyword(s):  
Heat Capacity ◽  
Gas Turbine ◽  
Pressure Ratio ◽  
Thermal Dissociation ◽  
Combustion Products ◽  
Heat Capacities ◽  
Isobaric Heat Capacity ◽  
Working Fluid ◽  
Gas Temperature ◽  
Temperature And Pressure

The basic thermophysical parameter of the working fluid of all thermal machines without exception is isobaric heat capacity (specific heat at constant pressure). Traditionally, in engineering calculations of isobaric heat capacity are determined as a tabular value for average heat capacities, or approximated with a square parabola within a given temperature range. Isobaric heat capacity is a function of temperature only. At the current level of GTE development, when the overall compressor pressure ratio is already up to 50 and the tendency of its increase remains it is unacceptable to neglect the pressure. However, the turbine inlet gas temperature also rises that will inevitably lead to the effect of thermal dissociation in the combustion products of the gas turbine engine. The studies of the thermal dissociation effect influence on the parameters of the working process of advanced GTE show that this ignoring leads to computational errors. At the present time, there are mathematical models that allow calculating the isobaric heat capacity as a function of temperature and pressure (taking into account the effect of thermal dissociation) but they are laborious, which is not always practical when estimate calculations performing and program algorithms writing. Consequently, the authors posed the problem of obtaining of simple analytic relationships that make it possible to calculate the isobaric heat capacity as a function of temperature and pressure (taking into account the effect of thermal dissociation). Based on the tabular data for the main components of the gas turbine combustion products within a given range of pressures and temperatures (nitrogen: p = 1 ... 200 bar, T = 150 ... 2870 K, oxygen: p = 1 ... 200 bar, T = 210 ... 2870 K, argon: p = 1 ... 200 bar, T = 190 ... 1300 K, the water vapor: p = 0.1 ... 200 bar, T = 640 ... 1250 K and p = 0.1 ... 400 bar and T = 1250 ... 3200 K, carbon dioxide: p = 1 ... 200 bar, T = 390 ... 2600 K), analytical dependencies were obtained for the calculation of isobaric heat capacities as functions of temperature and pressure taking into account the effect of thermal dissociation. The results of the calculations were compared with tabulated experimental data.

scholarly journals EQUATIONS OF AVERAGE ISOBARIC HEAT CAPACITY OF AIR AND COMBUSTION GASES WITH INFLUENCE OF PRESSURE AND EFFECT OF THERMAL DISSOCIATION

2019 ◽  
pp. 18-29
Author(s):  
Maya Vladimirovna Ambrozhevich ◽  
Mikhail Anatol'evich Shevchenko
Keyword(s):  
Heat Capacity ◽  
Thermophysical Properties ◽  
Thermal Dissociation ◽  
Heat Capacities ◽  
Isobaric Heat Capacity ◽  
Information Storage ◽  
Working Fluid ◽  
Saturation Curve ◽  
Functional Dependencies ◽  
Temperature And Pressure

All properties of thermomechanical systems working substance are two-parameter that is determined by two parameters, the most often they are temperature and pressure which are easily measured by experiment. Representing the isobaric heat capacity as a function of temperature cp = f(T) become a thing of the past. Analytical and tabular ways are used to represent dependencies as a function of temperature and pressure. The tabular method is convenient for single calculations, but the analytical one is more convenient for a series of calculations. The advantages of an analytical description in comparison with a tabular one are obvious, namely, compactness of information storage without reference to node points, the ability to integrate and differentiate, dependencies can be embedded directly in the program body and don’t require special subroutines to access to the tables. Developers of the programs for calculating thermophysical properties, as a rule, use functional dependencies which may have a different appearance for temperature and pressure intervals of the same substance. This is explained by the fact that in the region close to the saturation curve, there is a steep change in all the thermophysical properties of substances including the isobaric heat capacity. In thermogasdynamic calculations of heat machines, the main physical parameter of the working fluid is its heat capacity, both true and average. The article presents the analytical dependencies of the average specific isobaric heat capacities of the main components of air and combustion products of hydrocarbon fuels which are united throughout the specified range of pressures and temperatures (nitrogen: p = 1 ... 200 bar, T = 150 ... 2870 K, oxygen: p = 1 ... 200 bar, T = 210 ... 2870 K, argon: p = 1 ... 200 bar, T = 190 ... 1300 K, the water vapor: p = 0,1 ... 200 bar, T = 700 ... 2600 K, carbon dioxide: p = 1 ... 200 bar, T = 390 ... 2600 K). The analytical dependencies were derived on the basis of previously obtained analytical expressions for the specific isobaric heat capacities of these gases. The average specific isobaric heat capacities of gases are also functions of temperature and pressure cp = f(T, P) and take into account the effect of thermal dissociation. Formulas for average specific isobaric heat capacities are obtained by integrating expressions for specific isobaric heat capacities. Verification of the obtained dependencies for different temperature ranges was done.

Spectrophotometry of Aqueous HNO3, H2SO4, and DCIO4 from 25° to 250°C

1968 ◽  
Vol 22 (5) ◽  
pp. 545-548 ◽  
Author(s):  
W. C. Waggener ◽  
A. J. Weinberger ◽  
R. W. Stoughton
Keyword(s):  
Cell Wall ◽  
Corrosion Products ◽  
Spectral Measurements ◽  
Wide Range ◽  
General Program ◽  
Cell Window ◽  
Temperature And Pressure

Dilute nitric, sulfuric, and perchloric acids are applicable as solvents for spectrophotometry up to 250°C over the following ranges: 0 to 1.0 f HNO3 from 0.6 to 1.2 μ; 0 to 0.2 f H2SO4 from 0.25 to 1.2 μ; and 0 to 1.0 f DClO4 from 0.25 to 1.8 μ. Each of these acids reacts measurably with the titanium cell wall and the sapphire windows at rates which increase with acidity and temperature. This corrosion affects the spectral measurements as a function of time and is associated with deterioration of cell window surfaces and the presence in the sample of dissolved and suspended corrosion products. These results are part of our more general program for the development of equipment and technique for routine spectrophotometry of pure liquids and solutions over a wide range of temperature and pressure.

Thermodynamic Properties of Pure and Mixed Thermal Plasmas Over a Wide Range of Temperature and Pressure

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Omid Askari
Keyword(s):  
Thermodynamic Properties ◽  
Specific Heat ◽  
Fluid Dynamic ◽  
Thermal Plasmas ◽  
Statistical Thermodynamic ◽  
Reference Source ◽  
Degree Of Ionization ◽  
Wide Range ◽  
Self Consistent ◽  
Temperature And Pressure

Chemical composition and thermodynamics properties of different thermal plasmas are calculated in a wide range of temperatures (300–100,000 K) and pressures (10−6–100 atm). The calculation is performed in dissociation and ionization temperature ranges using statistical thermodynamic modeling. The thermodynamic properties considered in this study are enthalpy, entropy, Gibbs free energy, specific heat at constant pressure, specific heat ratio, speed of sound, mean molar mass, and degree of ionization. The calculations have been done for seven pure plasmas such as hydrogen, helium, carbon, nitrogen, oxygen, neon, and argon. In this study, the Debye–Huckel cutoff criterion in conjunction with the Griem’s self-consistent model is applied for terminating the electronic partition function series and to calculate the reduction of the ionization potential. The Rydberg and Ritz extrapolation laws have been used for energy levels which are not observed in tabulated data. Two different methods called complete chemical equilibrium and progressive methods are presented to find the composition of available species. The calculated pure plasma properties are then presented as functions of temperature and pressure, in terms of a new set of thermodynamically self-consistent correlations for efficient use in computational fluid dynamic (CFD) simulations. The results have been shown excellent agreement with literature. The results from pure plasmas as a reliable reference source in conjunction with an alternative method are then used to calculate the thermodynamic properties of any arbitrary plasma mixtures (mixed plasmas) having elemental atoms of H, He, C, N, O, Ne, and Ar in their chemical structure.

scholarly journals Internal volumetric heat generation and heat capacity prediction during a material electromagnetic treatment process using hybrid algorithms

2018 ◽  
Vol 38 (1) ◽  
pp. 74-82
Author(s):  
Edgar García-Morantes ◽  
Iván Amaya-Contreras ◽  
Rodrigo Correa-Cely
Keyword(s):  
Inverse Problem ◽  
Heat Capacity ◽  
Electromagnetic Field ◽  
Heat Generation ◽  
Initial Conditions ◽  
Limited Range ◽  
First Case ◽  
Realistic Situation ◽  
Wide Range ◽  
Volumetric Heat Generation

This work considers the estimation of internal volumetric heat generation, as well as the heat capacity of a solid spherical sample, heated by a homogeneous, time-varying electromagnetic field. To that end, the numerical strategy solves the corresponding inverse problem. Three functional forms (linear, sinusoidal, and exponential) for the electromagnetic field were considered. White Gaussian noise was incorporated into the theoretical temperature profile (i.e. the solution of the direct problem) to simulate a more realistic situation. Temperature was pretended to be read through four sensors. The inverse problem was solved through three different kinds of approach: using a traditional optimizer, using modern techniques, and using a mixture of both. In the first case, we used a traditional, deterministic Levenberg-Marquardt (LM) algorithm. In the second one, we considered three stochastic algorithms: Spiral Optimization Algorithm (SOA), Vortex Search (VS), and Weighted Attraction Method (WAM). In the final case, we proposed a hybrid between LM and the metaheuristics algorithms. Results show that LM converges to the expected solutions only if the initial conditions (IC) are within a limited range. Oppositely, metaheuristics converge in a wide range of IC but exhibit low accuracy. The hybrid approaches converge and improve the accuracy obtained with the metaheuristics. The difference between expected and obtained values, as well as the RMS errors, are reported and compared for all three methods.

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