Determining the elastic constants of hydrocarbons of heavy oil products using molecular dynamics simulation approach

Abstract

We have performed a molecular dynamics study in order to verify the assumption that saturated hydrocarbons can be characterized by generalized Hook's law using the fourth rank tensor of elastic constants. In this study normal paraffins were treated as crystals of hexagonal symmetry. Thus, we obtained original numerical values of Young's modulus and Poisson's ratio in both anisotropic and isotropic planes and the values of the shear modulus at three different temperatures. Negative Poisson's ratio of n-paraffins is of a particular interest. The author believes that auxetic behavior of saturated hydrocarbons is the result of their liquid-crystalline nature. Another remarkable point is the non-linear elasticity of n-paraffins detected in a wide temperature range. This provides an additional experimental confirmation of the phase transition process of hydrocarbons earlier reported in scientific works. We have shown that the matrix of elasticity of a particular heavy petroleum product can be estimated using the elastic parameters of the n-paraffins obtained. The numerical values of five independent elastic constants are directly proportional to the composition of a heavy petroleum product. The simplified representation of the composition can be defined by a few saturated hydrocarbons with different carbon numbers. The numerical results obtained in this research may be useful for those interested in heavy petroleum fractions rheology as well as those who perform numerical studies in petroleum hydrodynamics and acoustics.

Restrained shrinkage cracking of cementitious composites containing soft PCM inclusions: A paste (matrix) controlled response

“…Expectedly, on account of their soft nature (e.g., typically, the paraffin-based core and polymer shell materials display an elastic modulus on the order of 50 MPa, and 600 MPa ‡ ‡ , respectively [10][11][12][13][14][15][16]) -the dosage of PCMs into cementitious materials has been shown to result in reductions in the effective compressive strength of the composite [3,10,17,18] (e.g., see Figure 1b [10]). If such "strength reductions" are considered in terms of their implications on cracking risk; from a strength of materials perspective (i.e., cracking occurs when the strength of the material is exceeded) -it may be suspected that PCM additions may result in concretes being at a higher ‡ ‡ For a typical PCM microcapsule (median diameter ≈ 20 µm; see Figure 1), the shell makes up 5-to-10 volume %, with the remaining fraction occupied by the core.…”

Mixed‐Mode Multidirectional Poisson's Ratio Modulation in Auxetic 3D Lattice Metamaterials

“…[20,21] are some natural examples showing negative behavior like negative stiffness, negative compressibility, and most importantly, what we intend to deal with here, negative Poisson's ratio. Recent research activities revealed that organic crystals like nparaffins [22] and similar to them may demonstrate an auxetic behavior. Moreover, there are auxetic materials and models at various levels from the atomic scale to macroscale.…”

The effect of bitumen molecular fractions on diffusivity and rheology of bitumen under high‐temperature conditions: Molecular dynamics (MD) simulation study

“…Molecular dynamics (MD) simulation has effectively been applied to predict a wide range of parameters in heavy oil and bitumen systems, for example, interfacial behaviour between mineral aggregates and bitumen, [ 36–38 ] elastic constants of hydrocarbons, [ 39 ] heavy oil sticking behaviour on pipe walls, [ 40 ] dissolution behaviour of heavy oil in supercritical water, [ 41,42 ] density, solubility parameters, and surface energy. [ 43,44 ]…”

“…[33,34] There are two types of diffusions [34] : (i) mass transfer driven by a spatial concentration gradient and described by a transport diffusion coefficient and (ii) Brownian motion of molecules because of thermal fluctuations and considered by a self-diffusion coefficient. [35] Molecular dynamics (MD) simulation has effectively been applied to predict a wide range of parameters in heavy oil and bitumen systems, for example, interfacial behaviour between mineral aggregates and bitumen, [36][37][38] elastic constants of hydrocarbons, [39] heavy oil sticking behaviour on pipe walls, [40] dissolution behaviour of heavy oil in supercritical water, [41,42] density, solubility parameters, and surface energy. [43,44] Chen et al [45] applied MD simulations in a molecular model of waxy oil to calculate its transport properties, for example, the viscosity and self-diffusion coefficients of representative molecules.…”