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There are many ways to visualize flow, either for laminar or turbulent flows. A very convincing way to show laminar and turbulent flows is by the perturbations on the surface of a beam of water coming out of a cylindrical tube. Photographs, taken with a flash, show the nature of the flow of water in pipes. They clearly show the difference between turbulent and laminar flow, and let, in an accessible way, data be taken to analyse the conditions under which both flows are present. We found research articles about turbulence measurements, using sophisticated equipment, but they do not use the perturbation of the free surface of the flowing liquid to show or measure the turbulence.

In the present work, the optical design of a new high radiative flux solar furnace is described. Several optical configurations for the concentrator of the system have been considered. Ray tracing simulations were carried out in order to determine the concentrated radiative flux distributions in the focal zone of the system, for comparing the different proposals. The best configuration was chosen in terms of maximum peak concentration, but also in terms of economical and other practical considerations. It consists of an arrangement of 409 first surface spherical facets with hexagonal shape, mounted on a spherical frame. The individual orientation of the facets is corrected in order to compensate for aberrations. The design considers an intercepted power of 30 kW and a target peak concentration above 10,000 suns. The effect of optical errors was also considered in the simulations.

J. Am. Soc. Brew. Chem. 72(1):12-21, 2014 Gushing is the vigorous overfoaming of carbonated beverages when the bottle is opened. Primary gushing in beer is mostly caused by a group of proteins called hydrophobins secreted by filamentous fungi, which contaminate CO2 gaseous molecules during carbonation and form nanobubbles. The influence of hop oil antifoam on primary gushing showed a complete suppressing effect in sparkling water, a decreasing effect in wort, and no influence on gushing-positive beers. This shows the importance of the critical point of addition of this product in the brewing process. GC and GC-MS analysis show that commercial available lipophilic hop extract comprises fatty acids, either saturated fatty acids (SFA) or unsaturated fatty acids (UFA) (both free and incorporated in mono-, di-, and triglycerides), waxes (long-chain alkanes), and steroid compounds. Gushing analysis of each compound showed that SFA and UFA behave in a different manner regarding gushing. In contrast to SFA and trans-form UFA, cis-form UFAs do not induce gushing. Long-chain alkanes provide sufficient hydrophobic structures to interact with gaseous CO2 molecules and induce gushing. Because hop antifoam molecules are hydrophobic, they interact with hydrophobins and prevent interaction with CO2 and, consequently, inhibit the possibilities of development of the explosive nanobubble structure.

El propósito de este trabajo fue el estudio de los aerosoles atmosféricos en el Noroeste de México mediante el parámetro conocido como Espesor Óptico del Aerosol (AOT). Este parámetro representa uno de los coeficientes de extinción de la radiación solar y un indicador de partículas suspendidas en la atmósfera . Para la determinación del AOT recurrimos al uso de sensores remotos localizados fuera de la atmósfera. En particular, el Espectroradiómetro de Imágenes de Media Resolución (MODIS), el cual es capaz de obtener mediciones del AOT atmosférico . La información proporcionada por MODIS debe ser validada antes de considerarse fiable; para esta tarea, se obtuvieron mediciones desde la superficie para establecer una correlación con los datos derivados del sensor remoto. El artículo describe el proceso de validación que fue aplicado a los datos del sensor MODIS en contraste con mediciones obtenidas por uno de los fotómetros de la Red Robótica para medición de Aerosoles (AERONET) ubicado en la ciudad de Hermosillo, Sonora. Adicionalmente, se presenta un análisis temporal basado en el comportamiento de las gráficas del AOT, así como un análisis espacial derivado de la información contenida en los mapas de distribución del AOT.

The measurement of solar B band Ultraviolet radiation (UVB) should be considered a priority in Mexico due to implications on public health throughout the country (total population, 108 million), but this is not carried out at present. Installed sensors cover only 0.12% of the country. However, there are alternative methods for estimating UVB radiation to overcome the lack of surface data. The most successful of these are based on the use of satellites for environmental monitoring. In the present work, UVB maps are constructed for the entire country using a single, daily satellite measurement of UVB at solar noon from 1978-2003. Satellite-derived values are compared with the ground measurements by a surface station located in Mexico City in order to validate the former. Wavelet spectrum analysis is employed to this end. A close correlation is observed between the two sets of data. Moreover, there is qualitative correspondence between the spatial distribution of the satellite-derived data and the surface topography. The difference resulting throughout the period mentioned is

Heliostat image drift is defined as the wandering of the irradiance spot produced by a heliostat on a receiver or observation screen. Two factors producing heliostat image drift have been analyzed theoretically in the present paper: errors in reference position, and time delay. Some regular behavior is found in the drift curves. Maximum deviations from target tend to be linearly dependent with either angular error, or time delay. In particular, the curves produced by this later effect are circular or elliptical. Heliostats at different distances from a tower have been analyzed. For heliostats far from the tower the drift curves due to errors in reference position also have a more or less elliptical shape. Results are presented as dimensionless quantities. Some practical implications of these results are discussed.

A directly irradiated cavity solar reactor devoted to the thermal reduction of SnO2 particle-cloud is studied numerically by using the Monte Carlo method. The steady-state model solves the radiation and convection heat transfers in the semitransparent particle suspension and the chemical reaction. It was used to predict the temperature distribution and the reaction extent inside the cavity, as well as the theoretical thermochemical efficiency for different operational conditions. The simulations assume that the reactor contains a nonuniform size suspension of radiatively participating reacting SnO2 particles. The model takes into account the radiative characteristics of the particles, as well as the directional characteristics of the power distribution of the incoming concentrated solar energy. The particle concentration, the particle size, and the length of the reactor are varied. Results show that the particle temperature and the yield of the endothermic reaction are higher when the reactor is fed with a cloud of particles with average diameter of 20 μm. The maximal thermochemical efficiency reached is 10%, which corresponds to an optimal optical thickness of around 2.

In order to improve the durability of receivers used in solar concentrating systems, it is necessary to minimize thermal stress during their operation. A possible way to do that is to design receivers in which the radiative flux density is homogeneous at the surface. For this reason, a detailed 3D study has been carried out for the distribution of concentrated solar radiation in the focal zone of a parabolic concentrator. A computer program has been developed to obtain isosurfaces of solar irradiance and achieve a homogeneous radiation flux on the receiver surface. The algorithm of the program proposes a methodology to obtain flux isosurfaces for a great variety of optical configurations. The effect of the optical errors on the mirror surface has been studied, as well as the effect of the shape of the mirror, e.g., round, square, or faceted. The numerical calculations were made using the convolution ray tracing technique.

Drift is ubiquitous in heliostat fields, and may be caused by diverse geometrical inaccuracies during heliostat installation and operation. This phenomenon is studied for three important primary errors in the present paper: Angular offset in the drive mechanism, pedestal tilt, and canting error. Each error produces characteristic signatures, but there is a diversity of behavior depending on the error parameters and location of the heliostat. The variation of the extent of drift curves is studied as a function of distance, for fixed error parameters. It is found that, in general, this extent is not proportional to distance, except for far heliostats, and depends on a complicated manner on the different parameters involved. Moreover, even though the extent of drift curves becomes proportional to distance for far heliostats, the convergence is very slow, and very variable with the error parameters.

A methodology for the evaluation of the specularity error of a polymeric film optical coating is presented. The methodology is based on the comparison of images from the sun produced by two high quality spherical mirrors, one covered with a highly specular evaporated aluminum film, and the second one with the polymeric film under study. This film is a commercial product known as Reflectech®. To determine the specularity error, both images are reproduced by means of ray tracing optical simulations. Those simulations use the angular brightness distribution from the sun as input, which were recorded by means of a specially developed solar scope. Significant differences are obtained between images of the sun generated by both mirrors. However, the specularity error of the coating under consideration is found to be just 0.71 mrad. This error is quite small making the polymeric coating highly appropriate for point focus concentration systems. This is illustrated by calculations for a parabolic dish concentrator.

Radiative heat transfer in a 1 kW cavity-type solar reactor devoted to the thermal reduction of compressed ZnO and SnO2 powders is analyzed by a Monte Carlo ray tracing simulation. The developed model takes into account the radiative properties of the reactant particles and of the ceramic cavity walls, as well as the angular intensity distribution of the incoming concentrated solar irradiation. The model also includes the conduction heat losses through the lateral walls and the energy consumed by the endothermic chemical reaction. It is used to predict the temperature and the absorbed flux density profiles on the inner cavity walls for different main features of the reactor, concerning the dimensions of the cavity and the type of reactant. Results show that the absorbed flux density profile and the theoretical thermochemical efficiency change with the cavity aspect ratio and with the oxide reactant. The cavity with an aspect ratio of 3 and a SnO2 pellet undergoing dissociation presents the highest thermochemical efficiency. Additionally, a different configuration of the reactor design is considered, which consists in implementing a layer of reactive particles on the inner lateral cavity wall. The model highlights that this type of reactor operation with a reactant layer on the lateral cavity wall results in an improved thermochemical efficiency.

Since August 2011, the 30 kWt Solar Furnace for Higher Radiative Fluxes (HoSIER) of the Renewable Energy Institute (former Center for Energy Research) of the National University of Mexico (IER-UNAM) is in operation. The optical design of the HoSIER-UNAM includes a total of 409 spherical facets, divided into 5 different focal length groups [1]. A ray-tracing simulation was carried out to realize a three-dimensional analysis of the concentrated solar radiation distribution at the focal area of the HoSIER. In this way, theoretical profiles of the radiative flux were obtained. To get the experimental profiles of the concentrated solar irradiance of the HoSIER, a Lambertian screen was placed in the focal zone, normal to the optical axis of the concentrator. The screen was moved along 10 cm on the focus with each flat separated 5 mm of distance and in front of a CCD 8-bit digital camera. With the CCD was possible to obtain several experimental radiative flux distributions and thus it was possible to validate the ray-tracing simulation. This comparison shows a very good agreement between experimental and theoretical distribution.

Located in north western Mexico, the State of Sonora has an excellent quality solar resource, with the highest solar irradiation levels in the country. In less than 1% of its vast arid territory, it receives enough solar power to satisfy the energy demand of the entire country. In spite of its huge solar potential, there has been little work on the measurement of solar radiation in this area. At a few locations, global solar radiation has been measured for some years. Also there have been some works reporting evaluation of solar irradiation based on empirical models or satellite images. Because of the very small amount of precipitation on most of its territory, Sonora is ideal for the implementation of concentrated solar power (CSP). Beam solar radiation data is necessary for the sizing and assessment of CSP plants. Unfortunately, very little information is available on this solar radiation component for Sonora. The present work reports on the results of recent measurements of beam and solar global radiation for the area of the city of Hermosillo, in the center of the state. The obtained results are compared with other available information obtained by indirect methods, such as satellite based or empirical climate data based models. The yearly available energy as well as the utilizable energy for certain irradiance levels is evaluated.

In the last decade, the energy industry has been taken a big impact socially, ambiently, and economically due to the exponential increment in the use of fossil energetics, energy resources that have several problems due to low energetic efficiency, high-level pollution in storage and use. With the oscillations of the current price of petroleum and other fossil energetics, glo bal governments have determined the necessity to develop the research of renewable energy technologies, for global exploitation. The energetic potential of the Sun has shown as an alternative with a higher level of adaptation for domestic and industrial use; said potential due to their variable nature de pending on the time of the day, the season of the year, and the atmospheric situation shows an energetic constant of 1360 W/m2 . In this section is important to clarify the importance of quantification of the solar radiation that reaches the terrain surface, the main issue in the exploitation of renewable energetic, since the beginning of the XX century has approached widely. Several mathematic models of direct solar radiation have made using different strategies in solar tracking; the main importance of these solar tracking methods consists of the necessity to optimize the amount of solar radiation in any solar collector system. This research work proposes the mathematical analysis of the incident solar radiation on a flat surface through MATLAB programming language of several solar tracking schemes on clear sky conditions to geographical coordinates and climate conditions of Zacatecas (Latitude 22.7725 N, length 102.6436 E and altitude of 2,240 m). In this paper, programming routines have been written for the next tracking schemes: Continous tracking in the form of heliotrope, tilted with latitude and with azimuthal angular rotation. Tilted tracking with latitude. Continous tracking that rotates in the horizontal axis West-East according to the solar altitude. Fixed tracking. The main purpose is to find an efficient solar tracking method for the study location. This manner follows with step tracking analysis to 1, 30, 60, 120, and 240 minutes respectively. Clear sky model developed by the European Solar Radiation Atlas, Linke turbidity factor, total diffuse radiation by the change of a solid angle, Albedo parameter and, relative optical mass are concepts that have been worked to develop the analyzed modeling method on this thesis. Obtained data of the average monthly diary solar irradiation calculations are shown in form of tables and graphs to perform the corresponding analysis. Data comparison is ma de for each of the months of the 2019 year, to the different solar tracking schemes. Data analysis has been work and is shown as monthly percentual values, control case is defined as the continuous solar tracking heliotrope type with 100 %, due to the natural behavior of the scheme which provides the maximum value of solar energy possible. Shown for validation different comparations with the calculated data, regarding the mea sured data by the solar station Zacatecas 04 located at the UAZ Siglo XXI Campus in Zacatecas in the sixth building of the Universidad Aut´onoma de Zacatecas. In the same way, were analyzed and compared data obtained with a similar model develop in Mexico City presented by Ram´ırez in the 2017 year in her bachelors’ degree thesis, at the Facultad de Ciencias de la UNAM. Making a comparison of the different cases of solar tracking, the following is observed: (a) More solar radiation reaches each month, to the surfaces that comply with some scheme of sun-tracking, with respect to those surfaces that do not move.(b) The surface to which the least collection of solar radiation affects monthly is the horizontal surface. The solar irradiation per month estimated for this case is approximately 25 % below the maximum calculated value corresponding to the monitoring of heliotrope-type solar collection. Regarding the comparative analysis of the data obtained, it can be seen that: (a) The clear sky model prepared by ESRA has a behavior very close to reality for the geographical location Latitude 22.7725 N, longitude 102.6436 E and altitude 2,240 m related to the UAZ Siglo XXI Campus in Zacatecas, having a difference with the data obtained by the station Solarimetric Zacatecas 04 with a maximum value of 0.13 % for the month of January of the same year. En la última década la industria de los energéticos ha tomado un gran impacto social, ambiental y económico debido al aumento exponencial del uso de los energéticos fósiles, fuentes energéticas que poseen variados problemas en su uso los cuales van desde baja eficiencia energética, alto nivel de contaminación en su uso y reserva. Con las actuales oscilaciones del precio del petróleo y el de otros combustibles fósiles, los gobiernos mundiales han llegado a la conclusión de que es necesario fomentar la investigación y desarrollo de tecnologías de energías renovables, para su explotación global. El potencial energético del Sol, se muestra como una de la alternativas con mayor adaptabilidad para los usos domésticos e industriales; dicho potencial aun en su naturaleza variable de acuerdo a la hora del día, época del año y situación atmosférica, presenta como constante energética 1360 W/m2. En este apartado es de suma importancia el cuantificar la radiación solar que alcanza la superficie terrestre, principal problema en el aprovechamiento del energético renovable, que desde principios del siglo XX se ha abordado ampliamente. Varios modelos matemáticos de la radiación solar directa se han realizado utilizando diversas estrategias de seguimiento solar; la importancia de estos sistemas radica en la necesidad de optimizar la cantidad de radiación solar en cualquier tipo de colector. En este trabajo de investigación se plantea el análisis matemático de la radiación solar incidente en una superficie plana mediante el lenguaje MATLAB de diversos esquemas de seguimiento solar en condiciones de cielo claro para las coordenadas geográficas y condiciones 12climatológicas de Zacatecas (Latitud 22.7725 N, longitud 102.6436 E y altitud 2,240 m). Se escribieron rutinas de cáculo para los esquemas de seguimiento: Seguimiento continuo de tipo heliotropo, inclinada con latitud y rotación según el ángulo acimutal.Seguimiento inclinado con la latitud. Seguimiento inclinado con la latitud. Seguimiento continuo que rota sobre el eje horizontal Este-Oeste según la altura solar. Seguimiento fijo. La finalidad principal es encontrar el método de seguimiento solar mas eficiente para el lugar de estudio, de esta manera continuar con el análisis del seguimiento escalonado a 1, 30, 60, 120 y 240 minutos respectivamente. El modelo de cielo claro desarrollado por el Atlas Europeo de la Radiación Solar (ESRA por sus siglas en inglés), el factor de turbidez de Linke, la irradiación total difusa por el cambio de angulo sólido, el parámetro de Albedo y la masa óptica relativa son conceptos que se trabajaron para desarrollar el modelo analizado en esta tesis. Los datos obtenidos de los cálculos de irradiación solar promedio diaria mensual, se presentan en forma de tablas y gráficas con la finalidad de realizar el análisis correspondiente. Se hace una comparación de los datos obtenidos para cada uno de los meses del año 2019, para los diferentes esquemas de seguimiento solar. Se analizaron los datos y también se presentan en los valores en forma de porcentaje mensual, a manera de control, se considera el esquema de seguimiento continuo al sol de tipo heliotropo con el 100 %, esto se hace debido a la naturaleza del mismo esquema, el cual proporciona la máxima energía solar posible. Se muestra a manera de validación, diferentes comparaciones con los datos calculados con las rutinas elaboradas, con respecto a los datos obtenidos de mediciones de la estaciónsolarimétrica Zacatecas 04 ubicada en el Campus UAZ Siglo XXI, edificio 6 de la Universidad Autónoma de Zacatecas. De la misma manera se analizaron y compararon los datos obtenidos mediante un modelo similar en al Ciudad de México presentados por Ramírez en el año 2017 en su tesis de licenciatura, en la Facultad de Ciencias de la UNAM. Al hacer la comparación de los diferentes casos de seguimiento solar se observa lo siguien te: (a) Llega más cantidad de radiación solar por mes, a las superficies que cumplen con algún esquema de seguimiento del sol, con respecto a aquellas superficies que no se mueven. (b) La superficie a la que menos captación de radiación solar incide mensualmente es la superficie horizontal. La irradiación solar, por mes estimada para este caso se encuentra aproximadamente en un 25 % por debajo del máximo valor calculado correspondiente al seguimiento de captación solar de tipo heliotropo. Respecto al an´alisis comparativo de los datos obtenidos se puede apreciar que: (a) El modelo de cielo claro elaborado por ESRA tiene un comportamiento muy cercano a la realidad para la ubicación geográfica Latitud 22.7725 N, longitud 102.6436 E y altitud 2,240 m relacionado con el Campus UAZ Siglo XXI en Zacatecas teniendo una diferencia con los datos obtenidos por la estación solarimétrica Zacatecas 04 con un valor máximo de 0.13 % para el mes de Enero del mismo año.