23 research outputs found
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General method for prediction of thermal conductivity for well-characterized hydrocarbon mixtures and fuels up to extreme conditions using entropy scaling
A general and efficient technique is developed to predict the thermal conductivity of well-characterized hydrocarbon mixtures, rocket propellant (RP) fuels, and jet fuels up to high temperatures and high pressures (HTHP). The technique is based upon entropy scaling using the group contribution method coupled with the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) equation of state. The mixture number averaged molecular weight and hydrogen to carbon ratio are used to define a single pseudo-component to represent the compounds in a well-characterized hydrocarbon mixture or fuel. With these two input parameters, thermal conductivity predictions are less accurate when the mixture contains significant amounts of iso-alkanes, but the predictions improve when a single thermal conductivity data point at a reference condition is used to fit one model parameter. For eleven binary mixtures and three ternary mixtures at conditions from 288 to 360 K and up to 4,500 bar, thermal conductivities are predicted with mean absolute percent deviations (MAPDs) of 16.0 and 3.0% using the two-parameter and three-parameter models, respectively. Thermal conductivities are predicted for three RP fuels and three jet fuels at conditions from 293 to 598 K and up to 700 bar with MAPDs of 14.3 and 2.0% using the two-parameter and three-parameter models, respectively
Modeling the Thermal Conductivity of Pure and Mixed Heavy n-Alkanes Suitable for the Design of Phase Change Materials
Development of a new rate-type constitutive equation for viscoelastic fluid in the wiggle flow channel [Daralip-genişleyen kanalda viskoelastik bir akişkan için türev tipli yeni bir modelin geliştirilmesi]
In this study using some constitutive equations present in the literature, a rate-type constitutive equation is developed which is successful with the experimental results. The method being used is a nonlinear regression method that is known as Marquardt Method. Studies were done considering flow along the centerline of the flow channel. In this study the general form of the proposed constitutive equation was reduced on the centerline by using the flow kinematics and derivative operator for cartesian coordinates. Developing the difference of the normal stress components in the 1 - and 2- directions a nonlinear ordinary differential equation was obtained for the normal stress difference. When this differential equation that was reduced on the centerline was solved by this nonlinear regression method, model parameters, normal stress difference values along the centerline and sum of squares were determined simultaneously. When the proposed constitutive equation was compared with the existing equations, the proposed equation was found to be more successful in the flow along the centerline