The Potential Function for Double Square—Well Model and Its Application to Calculation of the Second Virial Coefficient

In the present paper, the mechanism of molecular aggregation and the character of potential function for square-well model have been investigated with the principle of molecular thermodynamics, leading to the potential function for double square-well (DSW) model. In addition, the equation of second virial coefficient for DSW model is derived from the statistical mechanics method. The above equation obtained has been verified by tests and the test results are excellent. It is concluded that this equation can well represent the behaviour of fluid molecules.     

Calculation of Volume Properties for Saturated Vapour by Using the Modified Truncated Virial Equation

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Calculation of NARM‘s Equilibrium with Peng—Robinson Equation of State

The liquid molar volumes of nonazeotropic refrigerant mixtures (NARM), calculated with Peng Robinson (PR) equation, were compared with vapor -liquid equilibrium experimental data in this paper. Provided with co-reaction coefficient k _ij , the discrepancies of liquid molar volume data for R22+R114 and R22+R142b using PR equation are 7.7% and 8.1%, respectively. When HBT (Hankinson-Brobst-Thomson) equation was joined with PR equation, the deviations are reduced to less than 1.5% for both R22+R114 and R22+R142b.     

Calculation of NARM's Equilibrium with Peng-Robinson Equation of State

IntroductionThere are mainly tWo well-known methods for thecalculation of fluid Phase equilibriUm, the method ofusing equation of state (EOS) or achvity coeffident.The later needs a plenty Of vapor-liquid equilibriumexperimental data in Order tO regress the calculatingmodel's parameters (such as non-random tWo liquidequation, (NRTL) etc). All means to describethermodynndc prOPelties are theoretically fonddedwith the equation Of state. If the EOS is suitable for theentire thermodyntalc …     

An Equation of State for Fluids by Applying the Tower—Well Potential Model

A simple theoretical equation of state is derived by applying the Tower-Well potential model about the molecular distribution based on the generalized van der Waals partition function. It needs only three molecular parameters which have distinct physical meanings. The resulting equation of state predicts rather well the vapor pressures, saturated liquid volumes, saturated vapor volumes and PVT thermodynamic properties of polar and structurally complex molecules over a wide temperature and pressure range.     

An Equation of State for Fluids by Applying the Tower-Well Potential Model

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Effect of the angle of attack on the wind convection coefficient

In this study the effect of the positive angle of attack (angle between flat plate surface and incoming uniform flow) on the convective heat transfer coefficient was investigated numerically. In the case of inviscid flow, this effect was also presented analytically and was found to be in good agreement with the corresponding numerical results. From the obtained numerical data, an accurate correlation equation of Nusselt number was proposed by introducing the effect of the angle of attack in terms of a new factor A_f. The variation of the convective heat transfer coefficient as a function of the angle of attack was found not behaves in the same manner for both small and large values of Prandtl number at small angles of attack.     

Performance test of a box‐type solar cooker: effect of load on the second figure of merit

In this paper thermal performance test experiments for first figure of merit (without load) and second figure of merit (with load) of a box‐type solar cooker were conducted as per Bureau of Indian Standards. The values of second figure of merit (F₂) were determined for different loads of water and the results show that F₂ depends on the quantity of water loaded in a solar cooker. Therefore, it is recommended that the performance test method should specify the amount of water which is to be taken. Copyright © 1999 John Wiley & Sons, Ltd.     

基于热力学第二定律的燃气轮机故障性能研究

本文利用热力学第二定律的功势转化指标标之一的推力功势转化性能指标。对燃气轮机在故障状态下的推力功势性能进行分析。对比用传统的部件效率来衡量的故障性能变化,分析并量化了几种典型故障下功势的转化性能的变化程度。结果表明：推力功势转化性能指标从能源转化为有用功的角度更好地衡量燃气轮机的故障性能,为进一步研究各种故障下燃气轮机的能源转化性能奠定了基础。     

喷水减温对热经济性的影响分析

给出通用型系统热经济性方程,并针对国产300MW机组,分析了过热器、再热器不同喷水位置对其热经济性的影响。结果表明,无论是过热器还是再热器,其减温水从最高加热器出口分流的影响较小,而再热器喷水对机组经济性的影响远大于过热器。     

Influence of thermodynamic models on the prediction of pool boiling heat transfer coefficient of dilute binary mixtures

In this paper, large number of experiments has been performed on saturated pool boiling heat transfer to three different dilute binary mixtures at various heat fluxes (up to 100 kW/m²) and five different concentrations (1–5 vol.% of heavier component). The test mixtures include water/glycerol, water/mono‐ethylene glycol (MEG), and water/di‐ethylene glycol (DEG). The effects of the main operating parameters such as heat flux, concentration, and bubble dynamics on the pool boiling heat transfer coefficient are also investigated. Furthermore, it is shown that physical properties of the mixtures have a considerable effect on the prediction of pool boiling heat transfer coefficients using the available correlations. In almost all of the existing correlations, some physical properties are strongly involved which can be estimated using different thermodynamic models. These models for the calculation of specific heat, density, heat of vaporization, and surface tension do not give exactly similar results and consequently, the heat transfer coefficient obtained from a specified predictive correlation can be tolerated according to the method used for the calculation of the physical properties. This point is usually ignored by investigators and they compare their experimental data with the correlations without reporting which thermodynamic models have to be used for the calculation of the physical properties. In this study, the prediction of Schlünder correlation has been compared with the present experimental data. Results show that the prediction ability of the Schlünder correlation is strongly dependent on the method used for the estimation of the required physical properties.     

Modeling the phase equilibria of the HIx mixture using the SAFT-VRE equation of state: Binary systems

The design and optimization of the separation units of the sulfur-iodine (SI) cycle process for hydrogen production requires a comprehensive analysis of the phase behavior of complex electrolyte solutions. Here, we apply the SAFT-VRE equation of state for electrolyte solutions to represent the phase equilibria of the HIx mixture (HI + H₂O + I₂) encountered in the reactive distillation column of the SI process. The phase equilibria of the binary mixtures (I₂ + H₂O, HI + I₂ and H₂O + HI) are accurately represented with the SAFT-VRE model. One key advantage of the SAFT-VRE model is the possibility to predict phase equilibria at high pressures and the densities of the coexistent phases, as well as the mean activity and osmotic coefficients of HI.     

热电厂热经济指标的简化算法

热电联产是提高能源有效利用率的重要途径,但其热经济指标的计算并不容易.其中,热化发电率和分项热经济指标是评价热电联产技术完善程度的指标,在所有热经济指标中占有重要地位.拟将热电联产机组的热力循环分为凝汽循环和供热循环,对两种循环利用热力系统状态方程原理,得出其各自的热状态参数,在此基础上计算供热机组的热化发电率及分项热经济性指标,使这两类的指标计算得以简化,并能方便地应用于工程实际之中.     

Equation of state for fluid mixtures based on the principle of corresponding states with a two‐fluid model: Application to fluid mixtures of water + ammonia

We propose an equation of state for fluid mixtures of water + ammonia which is expressed in Helmholtz free energy as a function of temperature, molar volume, and mole fraction. IAPWS Formulation 1995 for water and the equation of state by Tillner‐Roth and colleagues for ammonia should be used for each pure component with the present equation. We applied the principle of corresponding states with a two‐fluid model to the present equation for fluid mixtures. On comparison with experimental data, the uncertainty in property calculations by the present equation was evaluated: within ±0.03 · x for bubble point curve, within ±0.04 · x for dew point curve, within ±0.02 · ρ^L for saturated liquid density, and within ±0.02 · ρ for PVTX properties. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 131(4): 320–330, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10023     

Development of engineering design data for new refrigerants I: Pure fluids and azeotropic mixtures

It is important to correlate thermodynamic data for replacements for CFCs and HCFCs and present it in a form that will allow industry to design equipment from charts rather than complicated thermodynamic equations. This paper outlines the development of such equations for the more popular of these fluids. Sample pressure-enthalpy diagrams are then given for the pure fluids. In addition, since replacements for CFCs and HCFCs can be formed from both zeotropic and azeotropic mixtures of these fluids, the use of a typical mixing rule is discussed and initial results presented.     

An experimental study on static solid-liquid phase equilibrium in the pores of a porous medium

The so-called Clausius-Clapeyron equation, that is, the static equation of state for “solid-liquid-porous media” systems without liquid flow through the pores, has been experimentally examined by measuring the pore liqiud pressure at the solid-liquid interface in order to verify the accuracy of our method of measuring unfrozen pore liquid pressure. Several series of experiments have been carried out using water-saturated Ohya-Tuff as a porous medium specimen cooled from the top down. In these experiments, the solid-liquid interface was always fixed at the top surface of the specimen. The experimental results imply that the measurement method should be useful in determining the relative value of the unfrozen pore water pressure. © 1998 Scripta Technica, Inc. Heat Trans Jpn Res, 26(2): 69–83, 1997     

Simulation of the impact of internal pressure on the integrity of a hydrogen-charged Type-316L stainless steel during slow strain rate tensile test

A hydrogen-charged Type-316L austenitic stainless steel represents a slight loss of tensile ductility and cup-and-cone fracture accompanied by small-sized dimple. The reduction in the dimple size is interpreted to be attributed to void sheets caused by localized slip deformations by hydrogen. This paper aims to clarify the contribution of an internal pressure to the characteristic void growth of a hydrogen-charged Type-316L stainless steel during slow strain rate tensile (SSRT) test in air at room temperature. The internal pressure of pre-existing voids in the specimen charged by 100 MPa hydrogen gas at 270 °C for 200 h was simulated by diffusion-desorption analysis of hydrogen with the finite differential method (FDM). The subsequent impact of the internal pressure on the void growth was simulated by fracture-mechanics approach with the finite element method (FEM). The simulations performed under various void morphologies and fracture toughness suggested that the internal pressure in the voids was significantly low, hardly affecting the void growth.     

Recent researches in indirect evaporative cooler III: optimization of the cooling potential of a room–coupled indirect evaporative cooler

A mathematical model based on heat transfer principles, for characterizing the cooling performance of a room coupled indirect evaporative cooler (tube type) has been developed. Two dimensionless parameters, i.e. environment factor, ϕ and cooling factor, CF have been defined to characterize the performance of IEC coupled with a room. The optimum values of these parameters have been obtained for different environmental and thermal load conditions. In addition to this, a linear relationship has been obtained for the optimum size of a cooler to remove maximum heat from a room of given size. © 1998 John Wiley & Sons, Ltd.     

Studies of the pulse charge of lead-acid batteries for photovoltaic applications: Part IV. Pulse charge of the negative plate

The paper discusses the influence of the state of charge and pulse charge frequency on the mechanism of the lead-acid battery recharge with pulse current. The data from the pulse charge transients of the negative plate potential at various frequencies show that a decrease of the pulse charge frequency keeping constant average pulse current can impede the charge reaction leading to earlier start of the hydrogen evolution reaction. The dependence of the electrochemical double layer (EDL) capacitance on the state of charge was estimated both during the charge and the discharge using electrochemical impedance spectroscopy measurements at open circuit, followed by equivalent circuit modelling. These data were used to derive the dependence of the average double layer current on SOC and pulse charge frequency. The results show that in the end of the charge almost all of the charge proceeds with the participation of EDL in a certain pulse frequency domain. Using the data from the impedance measurements the optimal pulse charge frequencies were predicted, considering the existence of “electrochemical resonance”. The latter appears when the pulse charge frequency approaches the characteristic frequency of the Pb electrodeposition process, given by the product between EDL capacitance and the charge transfer resistance.     

On the ‘reaction in chain’ in the thermoelectric conversion of energy through thermocouples: Theoretical implications of the phenomenon

It is shown, experimentally, that in certain initial conditions of temperature, and for certain parameters, a ‘reaction in chain’ may start in a thermocouple, and produce a ‘permanent regime’, through which heat from a single course is converted into electrical energy. It is shown, theoretically, that the phenomenon occurs when compensation of heat losses due to thermal conduction, through Peltier and Thomson heat is realized, so that the efficiency is affected only by the Joule effect, and may attain much higher values than through conventional operation of these thermoelectric devices, conventional peration requiring two heat sources, a hot and a cold one.