In this communication, new experimental data are reported for the water content of methane and two synthetic gas mixtures in equilibrium with hydrates at pressures range from 5 to 40 MPa and temperature down to 251.65 K. The measurements have been made on equilibrated samples taken from a high-pressure variable volume hydrate cell using a new analyser based upon tuneable diode laser absorption spectroscopy (TDLAS) technology. A statistical thermodynamic approach, with the Cubic-Plus-Association equation of state, is employed to model the phase equilibria. The hydrate-forming conditions are modelled by the solid solution theory of van der Waals and Platteeuw. The thermodynamic model was used to predict the water content of methane and synthetic gases in equilibrium with gas hydrates. 相似文献
From a thermal point of view, zeotropic mixtures are likely to be more efficient than azeotropic fluids in low-temperature power cycles for reduction in exergy destruction occurring during heat absorption/rejection processes due to their suitable boiling characteristics. In this study, comprehensive energetic and exergetic analyses are mathematically performed for an organic Rankine cycle (ORC) system employing a potential binary zeotropic working fluid, namely R717/water. For this purpose, initially mass, energy, and exergy balance equations are derived. With regard to the similarity in molar mass of R717 (17.03 g mol?1) and water (18.01 g mol?1), there is no need to alter the size of the ORC components such as turbine and pump. In order to achieve the optimal thermal and exergy efficiencies of the ORC system, modified version a powerful and relatively new optimization algorithm called artificial bee colony (ABC) is used taking into account different effective constraints. The main motivation behind using ABC lies on its robustness, reliability, and convergence rate speed in dealing with complicated constrained multi-objective problems. Convergence rates of the algorithm for optimal calculation of the efficiencies are presented. Subsequently, due to the importance of exergy concept in ORC systems, exergy destructions occurring in the components are computed. Finally, the impacts of pressure, temperature, mass fraction, and mass flow rate on the ORC thermal and exergy efficiencies are discussed.
We investigate the problem with perturbed periodic boundary values
with a2, a1, a0C[0, T] for some arbitrary positive real number T, by transforming the problem into an integral equation with the aid of a piecewise polynomial and utilizing the Fredholm alternative theorem to obtain a condition on the uniform norms of the coefficients a2, a1 and a0 which guarantees unique solvability of the problem. Besides having theoretical value, this problem has also important applications since decay is a phenomenon that all physical signals and quantities (amplitude, velocity, acceleration, curvature, etc.) experience. 相似文献
We derive many new formulas for the approximation of π. The formulas make use of a sequence of iteration functions called
the basic family; a nontrivial determinantal generalization of Taylor's theorem; other ingredients; as well as several new
results presented in the present paper. In one scheme, one evaluates members of the basic family, for an appropriately selected
function, all at the same input. This scheme generates almost a fixed and preselected number of digits in each successive
evaluation. The computation amounts to the evaluation of a homogeneous linear recursive formula and is equivalent to the computation
of special Toeplitz matrix determinants. The approximations of π obtained via this scheme are within simple algebraic extensions
of the rational field. In a second scheme, the fixed-point iteration is applied to any fixed member of the basic family, while
selecting an appropriate function. In this scheme for each natural number
we prove convergence of order m, starting from the initial point. We report on some preliminary computational results obtained via Maple. Analogous formulas
can be used to approximate other transcendental numbers. For instance, we also give a formula for the approximation of e.
In fact, our results give new formulas and arbitrary high-order methods for the approximation of roots of certain analytic
functions.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
Plasma Chemistry and Plasma Processing - This research explored the capability of seed priming with the non-thermal plasma to modify reactions of Melissa officinalis, an important medicinal plant,... 相似文献
In this paper, we first give a characterization of Cayley graphs of rectangular groups. Then, vertex-transitivity of Cayley graphs of rectangular groups is considered. Further, it is shown that Cayley graphs Cay(S,C) which are automorphism-vertex-transitive, are in fact Cayley graphs of rectangular groups, if the subsemigroup generated by C is an orthodox semigroup. Finally, a characterization of vertex-transitive graphs which are Cayley graphs of finite semigroups is concluded. 相似文献