Experimental Enthalpy Increments from the Solid Phases to the Liquid Phase of Homologous n-Alkane Series (C₁₈ to C₃₈ and C₄₁, C₄₄, C₄₆, C₅₀, C₅₄, and C₆₀)

Abstract

Measurements of enthalpy increments from the temperature of the ordered phases of low temperatures at 293.4 K and 298.3 K up to the liquid phase above the melting point were carried out by differential scanning calorimetry using a discontinuous mode of temperature programming on the n-alkanes from C 18 to C 38 and C 41 , C 44 , C 46 , C 50 , C 54 , and C 60 . The temperatures and enthalpies of the solid-solid transitions and of the fusion were also determined and compared with the values of the literature.

Temperature-dependent thermal properties of solid/liquid phase change even-numbered n-alkanes: n-Hexadecane, n-octadecane and n-eicosane

“…It must be pointed out that the presence of two peaks for C 20 is characteristic of odd-numbered n-alkanes and hydrocarbons with carbon number greater or equal to 19 (i.e., nnonadecane, C 19 H 40 ). Triclinic structure (i.e., crystalline I) has been confirmed by X-ray Diffraction (XRD) at lower temperatures than T r while rotator crystal was reported for higher temperatures up to T m [47,48].…”

Analysis of Thermal Transients in an Asymmetric Silicon-Based Heat Dissipation Stage

“…Presently, a paraffin with a melting temperature between 80 and 83 C [13], [14] and an LMA with a melting temperature of 60 C (bismuth-tin-indium [15], [16]) are used. …”

“…1 has been developed and will be presented in this section together with the heat transfer characteristics of the three main constituent parts-the silicon structure part, the thermal storage part, and the heat switch part. Throughout this section the heat conduction law (13) for constant cross section and homogenous material is used where is the heat conductance, the thermal conductivity, the cross section area, and the length (13) …”

“…Given the linear materials parameters (Table II), the physical sizes (Table III), a melting temperature and enthalpy a model can be established. Based on the selection of the alkane with a melting temperature of 81.65 C [13] and a total transition enthalpy of 149.2 kJ/mol [14], the heat sink is modeled with the linear sensible heat over all temperatures with an additional transition enthalpy linearly distributed over a melting range of 80-83 C. Stability of the model is also facilitated by a 3 C span of the transition enthalpy. The total paraffin weight of 6.31 g gives a total transitional enthalpy of 1.63 kJ.…”

“…This temperature dependance appears almost linear with a tendency to rise quickly for very high values on the solar absorbtivity and very low values of IR emissivity. Since the graphs plot the maximum (after [13] and [14]). temperatures, the step in Fig.…”