David Jaramillo

Laws of Thermodynamics and Auxiliary Functions

Thermodynamics developed from studying the efficiency of early steam engines. Thermodynamics deals with energy exchange or energy transformation in a given system without considering any molecular mechanism. At its core, thermodynamics relates heat and temperature to energy and mechanical work.

Phase Equilibria I

In the previous chapter, it was discussed the thermodynamics principles that are the basis of thermochemistry. It was shown how to calculate the energy involved in any chemical or physical transformation. Additionally, it was established the Gibbs free energy as a criterion to know whether or not such transformations would take place under a given set of conditions.

Phase Equilibria II

In the last chapter, interactions between components forming mixtures were discussed. As more constituents were added to the system, the equations describing the thermodynamic quantities become more complex. However, it was shown in the examples section that graphical representation of such equations is very useful in determining those quantities.

Mixing and Solution Thermodynamics

In nature, we rarely find pure components or elements. We live in a world made of mixtures; therefore, we should shift our attention to mixtures components in solids, liquids, and gases. Because of this, we are more interested in the thermodynamics of mixing.

Effect of the Pt Addition on the Ni-Alloy Powder during Spark Plasma Sintering

Spark plasma sintering was carried out to densify Ni-alloy doped with Pt powder at temperatures ranging between 1273 and 1323 K in order to obtain a variety of microstructures. Homogeneous distribution Pt and full densification were achieved in a short time, and the overall processing time not was exceeding 30 min via SPS process. Phase constitutions and microstructures and porosity evaluation were investigated by using scanning electron microscopy, chemical analysis and X-ray diffraction. It was found that two new phases ζ-PtAl2 and α-NiPt (Al). The set conditions are very promising from an energy-saving viewpoint; total powder consolidation was obtained per a decrease of 200 °C in the sintering temperature by using spark plasma sintering.

Estimation of the Rate of Hydrogen Penetration in a Welded API 5L Steel Pipe

Hydrogen embrittlement is a common problem for the integrity of oil conducting pipes. In this work, we estimate the rate of hydrogen penetration into an API 5L steel pipe welded by electric arc. The hydrogen penetration was estimated by means of data taken from ultrasonic measurements. As expected, the steel pipe becomes more brittle as the hydrogen penetration rate does so. A simple diffusion model was developed. The model confirms the strong dependency between the rate of penetration and the mechanical damage to the material.

Estimation of the Heat Flux Through Furnace Side Walls Protected with Water Cooled Cooling Devices

A three dimensional numerical heat transfer model has been developed to estimate the heat flux trough furnace side walls protected with water cooled cooling fingers. The model was set up by means of the finite element method. Materials with different thermal conductivity were modelled and the results obtained with the mathematical model were compared with experimental data. In every case, it was found excellent agreement between the experimental data and the model computations.

Numerical Model to Describe the Growth of the Internal Oxidation Layer in Binary Alloys

Several analytical models have been developed through the years to describe the formation and growth of the internal oxidation layer in binary alloys. Such models are often complex and their validity strongly rely on precise measurements of molar fluxes of the different species involved in the oxidation process. The main disadvantage of such measurements is that they are difficult to made and present a high degree of uncertainties, thus some assumptions are needed to ease understanding and the applicability of them. In this paper we set up a numerical scheme (finite differences) to describe the growth of the internal oxidation layer in binary Cu-Al alloys oxidized in air at different temperatures. There is good agreement between the experimental results and the values calculated with the aid of our numerical approach.