Martin-Hou Equation Of State Research Articles

Modified Martin-Hou Equation of State Used in the Liquid Region for Pure Substances

Modified Martin-Hou Equation of State Used in the Liquid Region for Pure Substances

Computation of Ecological Properties, Flammability Properties and Thermodynamic Properties of Sustainable Refrigerant Dimethylether (RE170) Using Martin Hou Equation of State (MHEOS)

Computation of Ecological Properties, Flammability Properties and Thermodynamic Properties of Sustainable Refrigerant Dimethylether (RE170) Using Martin Hou Equation of State (MHEOS)

R-410A and R-404A real gas thermodynamic relations and their application for predicting exergy efficiency in vapor compression heat pumps

Enthalpy and entropy equations, as these resulted from the Martin-Hou Equation of State, are presented for the promising mixtures R-404A and R-410A that replace the HCFC-22 in refrigerator and heat pump systems. Based on these equations, a model was developed to simulate the relevant thermodynamic heat pump cycle for vapour compression systems. The variation of exergy efficiency factor, COP and exergy flow is outlined. Moreover focusing on the partial derivatives of pressure, on the real gas heat capacity at constant volume and on real gas heat capacity at constant pressure, useful characteristics such as sound velocity and isentropic exponents are derived and plotted in charts, for a wide area of state conditions.

Investigation of the scroll compressor porting process. Part I: global flow physics and behaviour of gas pockets

The three-dimensional time-dependent porting process of a scroll compressor is investigated numerically. In the first part of the investigation, the porting flow is examined in the background of an integrated compressor working process. The compressor studied includes the upper bearing housing, scrolls, check valve, and discharge plenum. The Navier-Stokes equations with a k-ɛ turbulence model are solved at the standard operating condition of the scroll compressor. Refrigerant-22 is used as the working fluid. The thermodynamic and transport properties of the refrigerant gas are modelled by the Martin-Hou equation of state and power laws, respectively. Global flow physics is investigated first to lay a foundation to understand the working mechanisms that control the porting process before averaging techniques are applied. The behaviour of the gas pockets in the porting process is characterized in both geometric and dynamic nature. The time-dependent variation of volume, mass, energy, and volume-averaged field quantities inside the gas pockets is studied throughout the porting process. The performance of the given compressor design during the porting process is defined.

Unsteady flow around suction elbow and inlet guide vanes in a centrifugal compressor

Suction elbow and inlet guide vanes (IGVs) are typical upstream components in front of the first-stage impeller in a centrifugal compressor. As the flow field in the front of the impeller is subsonic, the flow motion induced by the rotating impeller interacts with the elbow and IGVs. These interactions induce turbulent unsteady flows inside compressors. The resulting unsteadiness affects efficiency, vibration, and noise generation of the compressor. To understand the mechanism controlling the interactions between upstream components and to optimize the compressor design for better efficiency and reliability, the turbulent unsteady flow inside the first stage of the compressor was simulated. The model included the suction elbow, IGV housing, and firststage impeller. HFC 134a was used as the working fluid. The thermodynamic and transport properties of the refrigerant gas were modelled by the Martin-Hou equation of state and power laws, respectively. The three-dimensional unsteady flow field was numerically simulated. The overall performance parameters were obtained by integrating the field quantities. The force, torque, and the arm of moments acting on the IGVs were then calculated. The results can be used to design IGVs and their motion control system to achieve higher efficiency and improve reliability.

Exergy modelling of vapour compression heat pumps using refrigerant mixtures

Our work outlines the variation of exergy efficiency factor, COP and exergy flow related to the replacement of R22 in vapour compression heat pumps with the mixtures R407C and R410A. A mathematical model was developed to simulate the relevant thermodynamic cycles and an attempt was made for our results (efficiency and exergy losses) to be presented. Furthermore, particular attention has been given to the presentation of the equations of enthalpy and entropy of the substitute refrigerants, as these resulting from the Martin-Hou Equation of State. The results of this paper will enhance the design philosophy because exergy analysis contributes in the minimisation of losses and improves the systems operational cost.

Comparative Study of Unsteady Flows in a Transonic Centrifugal Compressor with Vaneless and Vaned Diffusers

To reduce vibration and noise level, the impeller and diffuser blade numbers inside an industrial compressor are typically chosen without common divisors. The shapes of volutes or collectors in these compressors are also not axis‐symmetric. When impeller blades pass these asymmetric structures, the flow field in the compressor is time‐dependent and three‐dimensional. To obtain a fundamental physical understanding of these three‐dimensional unsteady flow fields and assess their impact on the compressor performance, the flow field inside the compressors needs to be studied as a whole to include asymmetric and unsteady interaction between the compressor components. In the current study, a unified three‐dimensional numerical model was built for a transonic centrifugal compressor including impeller, diffusers, and volute. HFC 134a was used as the working fluid. The thermodynamic and transport properties of the refrigerant gas were modeled by the Martin‐Hou equation of state and power laws, respectively. The three‐dimensional unsteady flow field was simulated with a Navier‐Stokes solver using the k − ε turbulent model. The overall performance parameters are obtained by integrating the field quantities. Both the unsteady flow field and the overall performance are analyzed comparatively for each component. The compressor was tested in a water chiller system instrumented to obtain both the overall performance data and local flow‐field quantities. The experimental and numerical results agree well. The correlation between the overall compressor performance and local flow‐field quantities is defined. The methodology developed and data obtained in these studies can be applied to the centrifugal compressor design and optimization.

Calculation of thermodynamic properties of R407C and R410A by the Martin–Hou equation of state — part I: theoretical development

A theoretical development of the thermodynamic properties of two mixtures of hydrofluorocarbon (HFC) refrigerants, i.e. R407C and R410A (in the superheated vapour state), is carried out. The modelling is based on the Martin-Hou equation of state, which has long been used for pure hydrofluorocarbons (e.g. R134a) with good results. Since R407C and R410A are very well investigated refrigerants, the analytical procedure here derived concerns with those thermodynamic properties of R407C and R410A (in the superheated state) that are not published in the current specialised literature. They are: compressibility factor, isentropic and isothermal compressibility, volume expansivity, isentropic and isothermal exponent, speed of sound and Joule–Thomson coefficient. These properties may be used as a theoretical basis for research into the optimal HFC-mixture for compressor efficiency and for performing cycle calculations in the vapour-phase region for systems working with R407C and R410A.

Retention behaviour of polycyclic aromatic hydrocarbons during supercritical fluid chromatography with 1,1,1,2-tetrafluoroethane

The retention behaviour of polynuclear aromatic hydrocarbons on packed columns, with supercritical 1,1,1,2-tetrafluoroethane (KLEA) as the mobile phase, has been investigated. The variation of density of KLEA with pressure was calculated from the Martin-Hou equation of state, and comparisons made of k′ for the polycyclic aromatic hydrocarbons (PAHs) in isopyknic KLEA and CO 2. There is little evidence of specific interactions of KLEA with PAHs, although the molecular weight range of supercritical fluid chromatography (SFC) for PAHs should be extended.

Thermodynamic properties of R410B

The thermal properties of the refrigerant R410B have been investigated by the constant volume piezometer method at temperatures 279-385K and pressures 0.9-6MPA. Results of the measurement of critical parameters and the capillary constant are presented. The Martin-Hou equation of state was proposed for the calculation of thermodynamic properties. Data on thermophysical properties on the saturation line are presented

Vapor Pressure and Gas Phase PVT Data and Correlation for 1,1,1-Trifluoroethane (R143a)

A constant volume apparatus has been used to measure the vapor pressure and single phase densities (PVT) for 1,1,1-trifluoroethane (R143a), an ozone friendly refrigerant. The sample has a purity greater than 99.91% by mass. The measurements were done from 244 to 365 K at pressures up to 4.4 MPa and at densities ranging from 5% to 99% of the critical density. The uncertainties involved in the measurement of temperature, pressure, mass, volume, and specific volume are explicitly given. Thirty-three values for the vapor pressure and sixty-three densities along six isochores are presented and have been compared with previously published data and correlations. A Wagner type correlation for the vapor pressure and a Martin-Hou equation of state have been used to fit the measured data, which have been analyzed using the average absolute deviation, bias, and standard deviation. The gas phase densities have been used to determine the second virial coefficients.

Thermodynamic Properties of five Halogenated Hydrocarbon Vapour Power Cycle Working Fluids

Thermodynamic properties of five halogenated hydrocarbons, of importance as working fluids for small vapour power units, have been studied. The compounds are monochlorobenzene, hexafluorobenzene, o-dichlorobenzene, perfluoro-2-butyltetrahydrofuran and perfluorodecalin. With the aid of the Martin-Hou equation of state the properties of each compound, including sonic velocities and specific heat ratios, have been correlated. By comparison with the well established data for steam the accuracy of the sonic velocity and specific heat ratio values has been indicated. The information is presented in a manner which facilitates either the production of saturation and superheat tables or diagrams, or direct inclusion of the data in computer design and simulation studies of Rankine plant.