Cocción de Alimentos con Energía Solar: Resultados de una década de experiencia intensiva de utilización y de diseminación.

Resumen de la experiencia del autor en la cocción de alimentos con energía solar, así como de sus tareas de diseminación de esta tecnología.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.Plan Propio de Investigación de la UM

Experimental thermal performance evaluation of different configurations of Copenhagen solar cooker

In this work, four different configurations of Copenhagen solar cookers were tested experimentally at the same time under the same weather conditions. First tests were carried out using pots without water load. Secondly, tests were performed with the equal amount of water in each pot. Thirdly, tests were carried out with different amounts of water for one of the configurations. From the results of the first set of tests, it was found that the performance of one of the configurations depends more significantly on the solar altitude angle than the others. A large number of experiments for each set of tests were conducted covering a wide range of solar altitude angles. A thermal performance analysis based on the ASAE S580.1 standard was performed with the measured data of the second and third sets of tests. The obtained plots with the observation points of each configuration evidence that the linear trend of the standardised power is not universal. The observed trends are very dependent on the solar altitude angle. Thus, the procedure for evaluating standardised power recommended by the standard for cooker performance comparison should be improved

Experimental characterization of the thermal performance of the Haines 2 solar cooker

This work presents the most exhaustive experimental characterization of the thermal performance of the Haines 2 solar cooker available to date. Two Haines 2 solar cookers were tested side-by-side in Malaga, Spain, 36.7°N, between May 2021 and December 2021. A novel test procedure using empty pots and a tilted plane with variable inclination gave useful information about the influence of the solar altitude angle on cooker performance, and allowed identification of the best range for each of the two available reflector configurations for this cooker. Some suggestions are given to improve the cooker design for low solar altitude angles. In addition, a large number of water heating tests partly based on the ASAE S580.1 standard protocol were conducted to i) determine the standardised power, ii) examine the influence of the solar altitude angle, and iii) investigate the impact of using partial loads. All these results provide a complete characterization of the performance of this cooker in a wide range of operating conditions of practical interest. It is recommended that future versions of ASAE S580.1 standard consider the influence of both solar altitude angle and partial loads.Funding for open access charge: Universidad de Málaga / CBU

Structural and numerical identifiability of thermal resistances in plate fin-and-tube heat exchangers using manufacturer catalog data

Plate fin-and-tube heat exchangers, commonly known as heating/cooling coils, are widely used in HVAC systems to transfer heat to or from air. A problem of practical interest in coil simulation is to identify the thermal resistances on the air and liquid sides using manufacturer catalog data. Manufacturers rarely provide detailed information (geometry and circuitry) of the coils they sell or install in factory-made equipment such as air handling units or fan-coils; they just report the performance of the coil at a few typical operating conditions. This paper examines whether it is mathematically possible to back-calculate the thermal resistances on the air and liquid sides using a set of performance data that is disturbed by noise (e.g. measurement errors) and consists of operating cases in which none of the two thermal resistances can be neglected. The first part of the paper discusses the structural identifiability problem, that is, the mathematical possibility of fitting Nusselt-type correlations for air and liquid, as well as a constant resistance for the wall. The second part of the paper discusses the possibility of calculating the numerical value of the parameters of the Nusselt correlations (constant or constant and exponent) using noisy data. The analysis is applied to a typical coil, which is simulated by means of a mathematical modelUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

The effect of partial loads on the performance of a funnel solar cooker

Several solar cooker designs have been proposed over the last decades. The funnel cooker is a well-known model, representative of the category of panel-type solar cookers. From the empirical experience of real practice, it is known that the use of partial loads has an impact on the performance of the cooker. However, this effect has not yet been investigated rigorously. This work aims to fill this lack. Extensive experimental work was performed to determine the effect of partial loads on a funnel cooker thermal performance. Tests were conducted on two identical funnel cookers, in Malaga, Spain, with low sun elevation. Cookers were tracked only azimuthally. Experimental protocol was based on ASAE 580.1 Standard for better replicability. Results showed that the standardised power drops by about 15% of the original value when the water volumetric load fraction drops by 25%, for both cooker operations, with and without glass enclosure. This important reduction is explained on how the fill level of the cooking vessel affects its function as a thermal radiation receiver. Results from experimental tests were correlated into a simple formula of practical interest. Finally, a new cooking vessel design, that improves performance at partial loads, i.e., a 25.4% increase in cooker power, was proposed and testedFunding for open access charge: Universidad de Málaga / CBU

Experimental evaluation of the performance of new Copenhagen solar cooker configurations as a function of solar altitude angle

The Copenhagen cooker is a panel-type solar cooker that uses four flexible reflective panels to redirect solar radiation to a cooking vessel. Its concept design allows adjustment of the four panels to create new geometries that can adapt to the solar altitude angle. Originally, three geometrical configurations were presented by its creators. In this work, building upon these originals, new configurations are proposed to improve performances. To quantify performance improvement, experimental tests are performed. First, stagnation tests are carried out to identify the best configuration for different solar altitude angles. Then, the most promising new configurations and the original ones are tested, side-by-side, heating a water load and for different ranges of altitude angle: low (35 ), medium (66 ◦ ) and high (75 ◦ ). Results show that performance significantly improves. Results across the entire solar altitude angle range help general users to set the most effective configuration based on their specific conditions. Last, our experimental study suggests that tests without load can be a good predictor of the behaviour of solar cookers with load. This qualitative conclusion would allow solar cookers to be tested in shorter periods for all ranges of solar altitude angle, which is of great value for general users.Funding for open access charge: Universidad de Málaga / CBU

Investigación en comportamiento térmico de cocinas solares en el sur de la península ibérica 2020-2022

Esta comunicación resume el desarrollo de dos años de colaboración entre la Universidad de Málaga y la Universidad del Algarve en la investigación del comportamiento térmico de cocinas solares. Se han puesto a punto unas instalaciones experimentales en Málaga (36.7°N 4.4°W) que permiten el ensayo simultáneo de varias cocinas solares. Se han ensayado hasta la fecha, de forma extensiva, varios modelos de cocina solar tipo panel: Funnel, Copenhague y Haines, mientras que otros modelos están previstos en un futuro cercano. El trabajo experimental, que es fundamental, se ha complementado con estudios teóricos y numéricos sobre trazado de rayos (ray-tracing), procedimientos de ensayo, etc. Como resultado se han publicado diversos artículos científicos hasta la fecha. Esta comunicación recapitula algunos resultados interesantes que contribuyen a una mejor compresión del comportamiento térmico de las cocinas solares

Experimental method to study the evolution of the performance of solar cookers as a function of solar altitude

The performance of solar cookers, mainly box cookers and panel cookers, depends on the solar altitude. To study the effect of solar altitude, using the ASAE S580.1 standard or another method that uses liquids. Many tests are required, at different times of the year (different solar altitudes). For this reason, a study method was developed that does not use liquids as study fluid. Leaving only the pot full of air. When the pot is without liquid inside, the pot is operating with small inertia because the measure air temperature achieves much higher values, with short delay, than the ones obtained with liquids. Moreover, the registered evolutions can represent also how the stagnation temperature depends on the solar altitude angle. Thus, the plots provide valuable information about what is the most suitable ranges of solar altitude angle for each solar cooker. This method has been validated and has been improved with several experimental tests in different solar cookers.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Modelação numérica dos fenómenos de transferência de calor e de massa em rodas higroscópicas

Tese de doutoramento em Engenharia Mecânica (Transmissão de Calor) apresentada à Fac. de Ciências e Tecnologia da Univ. de CoimbraApresenta-se um estudo de índole numérica sobre os fenómenos de transferência de calor e de massa em rodas higroscópicas. A modelação fez-se, numa primeira fase, para um domínio de um canal tomando como base uma formulação detalhada em ambos os sub-domínios, do escoamento e da parede, tendo as equações de conservação sido discretizadas através do método dos volumes finitos e resolvidas num domínio bidimensional. Numa segunda fase, analisou-se a resposta transiente de um canal de placas paralelas e implementaram-se modelos com simplificações ao nível da formulação no domínio do escoamento e compararam-se os resultados destes com os dos modelos detalhados. A modelação simplificada do escoamento e das trocas convectivas com a parede apresentou uma boa concordância de resultados, pelo que foi adaptada à simulação do comportamento de um canal com configuração real em regime cíclico estacionário, como se o canal a uma roda higroscópica pertencesse. Utilizou-se uma versão unidimensional deste último modelo para a simulação da resposta transiente de um elemento de canal, com vista ao estudo da validade de algumas hipóteses de simplificação na modelação do meio poroso exsicante. Os cálculos foram estendidos à análise do comportamento do elemento de canal em condições de regime cíclico estacionário. Os estudos realizados quer sobre a configuração de elemento de canal, quer sobre o desempenho da roda higroscópica, puseram em evidência a existência de condições de desempenho óptimas, nomeadamente no que respeita à duração total do ciclo de adsorção/desadsorção, à duração de cada um dos modos, bem como à constituição da parede da matriz. Os modelos desenvolvidos revelaram ser ferramentas de cálculo úteis na concepção e na simulação do comportamento de rodas higroscópicas, podendo ser utilizados no desenvolvimento de módulos de simulação de rodas higroscópicas mais simplificados

Indoor climate quality assessment in civil aircraft cabins: A field study

Indoor Climate Quality is the way to assess how much thermal and indoor air quality conditions might influence people's comfort indoors. Passengers traveling on commercial airplanes are increasingly demanding comfort inside the cabin. So, creating a comfortable environment is a relevant requirement to be considered. Although indoor climate standards cover mainly buildings, other indoor environments may use the same concepts. This study aimed to present a multiprobe device for indoor climate quality assessment and a methodology to cate-gorize thermal comfort and indoor air quality levels in twenty-five flights between 2019 and the beginning of 2020. Data were collected in two distinct seasons, Heating and Cooling, regarding the mode of use of HVAC systems, depending on the predominant passengers' clothing set, for different aircraft types and routes. It was analyzed how much thermal comfort and indoor air quality parameters are in accordance with the categories established in the EN 16798-1 standard. As the main findings, it can be concluded that the environmental pa-rameters analyzed on flights were mostly within the comfort range. However, there is a possibility of improvement in thermal comfort since the predominance of values in the best comfort category is still marginal, focusing on the study of air cleaning and air distribution flow to improve people's comfort and energy saving.info:eu-repo/semantics/publishedVersio