The thermal wave amplitude method is used to determine soil thermal diffusivity in situ for a sandy soil in Mexico (Coatzacoalcos, Veracruz). Soil diurnal temperature fluctuations were measured from depths of 0.05 to 0.65 m, in 0.01 m increments, during the months of April and August. Five mean diffusivity values were obtained experimentally, corresponding to the different depths combination. The soil thermal diffusivity ranged between 2.26 × 10-7 and 8.71 × 10-7 m 2 s-1. The diffusivity values obtained are within the absolute ranges reported in the literature. A positive linear effect between the diffusivity values and depth was observed on a homogeneous sandy soil. These increments are due to the soil moisture variations and the volumetric calorific capacity of the soil. An uncertainty analysis was made to validate our results, resulting in a relative standard deviation with values in the range of 4.51 to 27.37 %. The uncertainties of 0.49 to 26.66 % RSD in the amplitude of the thermal wave are the factor that contributes most to the propagation of errors of the diffusivity.

This paper presents the study of a simple effect absorption refrigeration system (SRA) using the ammonia-water working couple, with the incorporation of three economizers and their analysis of the first and second law of thermodynamics, emphasizing the effect of the operating temperatures and the efficiency of the exchangers on the refrigerant circulation ratio (RC), the coefficient of performance (COP) of the system and the destruction of exergy. In order to determine the thermodynamic properties at each point of the system and evaluate the performance of the SRA, was programmed a tool in MATLAB with the governing equations. The results show that: the exergy efficiency increases when the temperature in the evaporator decreases; and RC decreases with increasing temperature in the generator. As conclusion, an increase in the effectiveness of heat exchangers cannot only decrease the refrigerant circulation rate, but also increase the inlet temperature of the solution to the generator, so that the temperature difference between the solution and the heat source decreases, causing a decrease in the rate of exergy destruction in the generator and the increase in COP.

Among the various factors that affect the energy produced a detailed numerical simulation of a ground heat exchanger assuming the mathematical formulacion of the governing ecuations (continuity, momentum and energy) and the energy balance in the wall has been carried out. This formulation requires the use of termo-physical properties, material properties and the ground; in this case, the experimental temperature profile in the ground were measured at Universidad Veracruzana, Coatzacoalcos campus (latitude 18°08’39” N, longitude west 94°28'36” and altitude 10 msnm).

The contribution of this research is to determine the change in the heat flow by the axial torsion in a tube of square cross section. The tube studied is part of a prototype heat exchanger designed and built by the research group in "Engineering and simulation of energy processes" of the Universidad Veracruzana, Coatzacoalcos region, Veracruz. The experimental prototype was designed and constructed with PVC pipe and the test section with aluminum tubes. The heat transfer of equipment was from 5 to 60 kJ with volumetric flows from 3 to 20 l/min and water as a working fluid. The tube without axial torsion (0°) is compared with three other tubes with 180°, 360° and 540° torsion. The experimental results reported in this study show the preliminary experimental tests where four levels of water flow are configured, using flow and temperature measurement instruments. The preliminary experimental results reveal an increase in the heat transfer in the equipment as the degree of axial torsion in the square section tubes is increased.

This work makes a comparative study of two methods to determine deflection in steel beams: (a) Theoretical and (b) Finite element. For method (a) the solution of the differential equation associated with the modeling of the deflection of a beam is found, while for method (b) a simulation is made in Solidworks. Both methods are compared with experimental data in order to analyze which of the methods presents less uncertainty and show the usefulness of the theoretical part in the modeling of physical systems.