Made available in DSpace on 2014-06-11T19:25:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-07-13Bitstream added on 2014-06-13T20:33:04Z : No. of bitstreams: 1 sales_fb_me_bauru.pdf: 1185139 bytes, checksum: ba8e8304a72e250dcb73d00e64d9a913 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / As discussões recentes sobre sustentabilidade tem destacado os sistemas de aquecimento solar como alternativa adequada para aquecimento de água. Estes sistemas tem ganho notoriedade tanto para uso doméstico como no aquecimento de piscinas. Um dos aspectos que é frequentemente destacado como principal dificuldade para a sua popularização, entretanto é o custo de sua implantação. Uma das formas de reduzir este custo é minimizando o número de componentes e simplificando o sistema. Nesta linha de desenvolvimento muito tem se discutido sobre o uso de sistemas integrados coletor-armazenador (ICS). Baseando-se nestas avaliações, este trabalho pretende estudar diferentes configurações geométricas de coletores solares com armazenador integrado do tipo cubóide e verificar a influência sobre o aproveitamento de energia térmica quando se utiliza diferentes dispositivos para direcionar o fluxo de água quente. A partir de simulações numérico-computacionais é possível identificar as geometrias que apresentam melhor estratificação térmica no armazenador. A estratificação da temperatura em um armazenador é um fator extremamente importante no estudo de coletores solares, pois determina a porção de temperatura mais elevada. O modelo base, validado experimentalmente na literatura, foi utilizado com condições de fluxos de calor incidente e de perda por resfriamento constantes com boa concordância de resultados. Modificações geométricas foram implementadas e avaliadas para otimizar os parâmetros de projeto deste tipo de coletores solares integrados. Outras análises alterando o volume do sistema coletor-armazenador foram realizadas: um com 200 litros de capacidade e outro com 300 litros, de maneira a estabelecer um tamanho ótimo do sistema. Para visualizar a estratificação do armazenador... / Recent discussions highlighted the sustainability of solar heating systems as an apropriate alternative for heating water. These systems has gained prominence for both household and swimming pool heating. One aspect that is often highighted as the main obstacle to its popularity is the cost of its implementation. One way to reduce this cost is to minimize the number of components and simplifying the system. In this field of development has long been discussed about the use of integrated collector-storage (ICS). Based on these evaluations, this work analyzes different geometrical configurations of integrated solar collector-storage with storage type cuboid and the influence on the use of thermal energy when you use different devices to direct the flow of hot water. From numerical-computational simulations, the geometry with better thermal stratification in the storage can be identified. the stratification of temperature in a storage is an extremely important factor in the study of solar collectors, because it determines the portion of higher temperature. The base model, experimentally validated in the literature, was used with constant conditions of incident head flux and loss for cooling. Geometric changes were implemented and evaluated to optimize the design parameters of this type of integrated solar collectors. Further analysis by changing the volume of the collector-storage system were carried out: a 200 liter capacity and another with 300 liters, in order to establish and optimum size of the system. To view the stratification of the storage, images with the temperature profile are shown at the end of the heating and cooling periods and the following graphics show the stratification coefficient. The CFD method allowed to obtain results with good agreement with those used as the basis from the literature. Results... (Complete abstract click electronic access below)

Solar energy is increasingly being considered a promising solution to reduce the emissions of CO2 and green house gas. The performance of solar collectors largely depends on the ability to absorb incoming solar radiation with minimal thermal radiation losses. To weigh the potential absorbed energy to thermal losses, the performance criterion (PC) can be used, calculated as PC =α−xε, where α is absorptance, ε is emittance and x is a scaling factor < 1. It has been shown by G. Vargas et al. that Co-Cr alloys excibit great potential (α = 0.98 and ε = 0.03) for use in solar concentrators. The main goal of this project is to quantify the impact of key factors (controlled input variables) on an electroplating process of Co-Cr alloys, using the design of experiment (DOE) methodology. It is part of an ongoing collaboration between Absolicon and the physics department at Umeå university. Six factors were investigated using a fractional factorial (FrF) design. Data was collected through a series of experiments where stainless steel substrates were electroplated with Co-Cr alloys. The resulting samples were analyzed in terms of α and ε as well as the quality of deposition (QD). Using the experimental results, three models were made in a DOE-software called MODDE. Models are used to correlate the factors with each response, i.e. α, ε and QD. Ideally the predictive power of the models (Q2) should be as high as possible, and at least > 0.5. The analysis of variance (ANOVA) test was used to determine the significance of the models. Based on the models, the ’Optimizer’ tool in MODDE was used to predict two set of optimum factor settings, producing two samples, S1 and S2. S1 and S2 were evaluated in terms of α, ε and QD as well as chemical composition and structural properties of the coatings. The predictive power of the models was 0.49 for α, 0.38 for ε and 0.53 for QD. The predictive power of the models were therefore limited. ANOVA-test showed that the models for α and QD were statistically significant. For all three responses the significant effects were mostly two factor interactions. All three models showed significant lack of fit (model error) as a result of high reproducibility. S1 had the best PCAbsolicon (performance criterion for Absolicons solar collectors) of all samples with 0.858. S2 was not as good, even though it was predicted to have a higher value of PCAbsolicon by MODDE. EDS, XPS and SEM measurements of samples S1 and S2 showed that the two samples were very similar in terms of chemical composition. The main difference was that the coating of S1 was more porous, and also thicker than S2, 0.81 μm compared to 0.26 μm. Even though the models showed some predictive capabilities, the impact of the factors could not be fully determined. That is due to the nature of the FrF-design, which cannot accurately determine two-factor interactions.

Made available in DSpace on 2014-06-11T19:24:42Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-01-25Bitstream added on 2014-06-13T19:11:16Z : No. of bitstreams: 1 bentivenha_lc_me_botfca.pdf: 1314612 bytes, checksum: 253e63a1300e0c3946bf45baca1a4fba (MD5) / Universidade Estadual Paulista (UNESP) / Os coletores solares comumente utilizados no aquecimento de água, para o consumo doméstico, possuem a placa de aquecimento solar plana do tipo chapa - tubo. Devido à crescente utilização desses equipamentos, buscou-se, através deste trabalho, modificar um equipamento convencional, o qual recebeu, na placa solar, aletas de vidro, instaladas no plano vertical em relação à tampa de vidro, dividindo a mesma em diversas áreas, propiciando um aumento, tanto da reflexão dos raios infravermelhos em seu interior, quanto do efeito estufa. O objetivo do ensaio foi estudar o comportamento térmico desse equipamento, trabalhando a determinada vazão e obtendo as temperaturas com o emprego de termopares instalados em vários pontos do sistema, buscando a determinação da eficiência térmica da placa solar modificada. Para a determinação da eficiência, foram considerados o calor útil, o calor absorvido e as perdas de calor. As equações empregadas na determinação da eficiência térmica foram trabalhadas no programa Excel.Verificou-se que o equipamento apresentou um bom rendimento, atendendo as especificações definidas pelo INMETRO. A temperatura média de saída da água do equipamento apresentou valor superior a de equipamento similar, o mesmo não ocorreu com seu rendimento, embora as diferenças registradas tenham sido pequenas. A eficiência do equipamento não depende apenas dos parâmetros do projeto, mas também de outros fatores que levam a perda de energia. / The solar collectors commonly used in the water heating for domestic consumption possess the flat plate solar heating of plate type - tube. Due to increasing applications of those equipments the purpose was to modify the conventional, which received glass fins in the solar plate, installed in the vertical plan in relation to the glass cover, dividing the same in several areas, enabling reflection increase of the infrared rays in its interior as well as greenhouse effect. The thermal performance of the equipment has been studied analyzing the certain flow and obtaining the temperatures with the thermopairs installed in several points of the system and determining the thermal efficiency of the modified solar plate. The useful heat, the absorbed heat and the losses of heat were considered. The equations of the thermal efficiency were obtained in the Excel program. The equipment presented a good performance according to INMETRO specifications. The medium temperature of the water exit presented superior value when compared to a similar equipment. The same didn't occur with its performance, although the registered differences have been small. The efficiency of the equipment doesn't depend only on the parameters of the project, but also on other factors which lead to energy loss.

Orientador: José Roberto Corrêa Saglietti / Banca: Angelo Cataneo / Banca: Alessandro Torres Campos / Resumo: Os coletores solares comumente utilizados no aquecimento de água, para o consumo doméstico, possuem a placa de aquecimento solar plana do tipo chapa - tubo. Devido à crescente utilização desses equipamentos, buscou-se, através deste trabalho, modificar um equipamento convencional, o qual recebeu, na placa solar, aletas de vidro, instaladas no plano vertical em relação à tampa de vidro, dividindo a mesma em diversas áreas, propiciando um aumento, tanto da reflexão dos raios infravermelhos em seu interior, quanto do efeito estufa. O objetivo do ensaio foi estudar o comportamento térmico desse equipamento, trabalhando a determinada vazão e obtendo as temperaturas com o emprego de termopares instalados em vários pontos do sistema, buscando a determinação da eficiência térmica da placa solar modificada. Para a determinação da eficiência, foram considerados o calor útil, o calor absorvido e as perdas de calor. As equações empregadas na determinação da eficiência térmica foram trabalhadas no programa Excel.Verificou-se que o equipamento apresentou um bom rendimento, atendendo as especificações definidas pelo INMETRO. A temperatura média de saída da água do equipamento apresentou valor superior a de equipamento similar, o mesmo não ocorreu com seu rendimento, embora as diferenças registradas tenham sido pequenas. A eficiência do equipamento não depende apenas dos parâmetros do projeto, mas também de outros fatores que levam a perda de energia. / Abstract: The solar collectors commonly used in the water heating for domestic consumption possess the flat plate solar heating of plate type - tube. Due to increasing applications of those equipments the purpose was to modify the conventional, which received glass fins in the solar plate, installed in the vertical plan in relation to the glass cover, dividing the same in several areas, enabling reflection increase of the infrared rays in its interior as well as greenhouse effect. The thermal performance of the equipment has been studied analyzing the certain flow and obtaining the temperatures with the thermopairs installed in several points of the system and determining the thermal efficiency of the modified solar plate. The useful heat, the absorbed heat and the losses of heat were considered. The equations of the thermal efficiency were obtained in the Excel program. The equipment presented a good performance according to INMETRO specifications. The medium temperature of the water exit presented superior value when compared to a similar equipment. The same didn't occur with its performance, although the registered differences have been small. The efficiency of the equipment doesn't depend only on the parameters of the project, but also on other factors which lead to energy loss. / Mestre

Orientadores: Marlene Rita de Queiroz, Thomaz Penteado de Freitas Borges / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agricola / Made available in DSpace on 2018-08-04T17:44:33Z (GMT). No. of bitstreams: 1 Santos_BrenoMonteirodos_M.pdf: 1088354 bytes, checksum: 34b6badc189dd2dfeafa1a3c5f41515c (MD5) Previous issue date: 2005 / Resumo: Uma metodologia para o projeto de coletores solares visando a secagem de grãos em silo foi implementada utilizando-se correlações empíricas previamente determinadas para o cálculo da fração solar fornecida pelo sistema. Foi realizado um estudo de caso de uma secagem de milho em silo, na cidade de Campinas ¿ SP, com pré-aquecimento do ar através de um coletor solar e aquecimento complementar com fonte energética convencional (GLP ou lenha). O coletor solar utilizado possui área de 1,80m2, foi construído com materiais de baixo custo e, devido ao material constituinte de seu leito (pedras britadas), apresenta elevada inércia térmica e capacidade de armazenar energia. A caracterização do coletor foi feita com o levantamento da sua curva de eficiência e com a determinação de sua constante de tempo. De maneira semelhante ao observado em coletores solares convencionais, a curva característica levantada apresentou comportamento linear. A capacidade de armazenar energia térmica foi constatada no elevado valor da constante de tempo obtida e pelas defasagens entre as curvas de calor útil fornecido ao ar e radiação solar incidente na superfície do equipamento. Na secagem de 1,20t de milho considerada no estudo de caso, utilizando-se uma vazão volumétrica específica de ar igual a 1,20 m3/m3.min à temperatura de 50°C, obteve-se uma economia de 31% na energia demandada para o aquecimento de ar. Através da análise de ciclo de vida econômico, para a utilização conjunta de energia solar e GLP no aquecimento de ar, foi determinada uma área coletora ótima de 7,50m2 a uma taxa de interesse de 0,12a.a., proporcionando o máximo retorno financeiro durante o ciclo de vida do equipamento. Aumentos nas taxas de interesse diminuem tanto os valores de área coletora ótima como do retorno financeiro durante o ciclo de vida econômico. Foi demonstrada, para as condições fixadas no estudo de caso, a viabilidade econômica da conversão de sistemas que utilizam GLP como fonte energética para sistemas assistidos por energia solar, proporcionando redução nos impactos ambientais da atividade e economia para o produtor rural. Nas mesmas condições foi verificada a inviabilidade econômica da utilização de energia solar em conjunto com a lenha / Abstract: A solar collector design procedure was proposed for sizing solar assisted crop-drying systems using empiric correlations, previously found, to determine the solar fraction supplied by the system. A case study of an in-bin crop drying was accomplished in the city of Campinas - SP with pre-heating of the air through a solar collector complemented by conventional energy source (LPG or firewood). The used solar collector had an area of 1,80m2, it was built with low cost materials and, due to its pebble bed, it presented a high thermal inertia and storing energy capacity. The collector was characterized by determining its efficiency curve and its time constant. As observed in conventional solar collectors, the characteristic curve presented linear behavior. The capacity to store thermal energy was confirmed by the high value of the time constant and by the delay between the useful heat and the incident solar radiation curves. In the studied case of drying 1,20 tons of corn, using a specific air flow rate equal to 1,20 m3/m3.min and a temperature of 50°C, it was saved 31% of the demanded energy for air heating. For a solar-assisted drying using LPG as the conventional source of energy, an optimum collector area of 7,50m2 was found through the life cycle saving analysis calculated with an annual interest rate of 0,12, providing the maximum saves during the equipment life cycle. Increasing the interest rate reduced both optimum collector areas and life cycle savings. For the crop drying case, it was demonstrated the economical viability of the conversion of LPG based to solar-assisted systems, providing reduction in the environmental impacts of the activity and savings for the rural producer. In the same conditions was demonstrated there is no economical viability in the conversion of firewood based to solar-assisted systems / Mestrado / Tecnologia Pós-Colheita / Mestre em Engenharia Agrícola

Orientador: Jose Antonio Siqueira Dias / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-14T11:25:46Z (GMT). No. of bitstreams: 1 Ormenese_Marcela.pdf: 17981897 bytes, checksum: c7b7714358950bc575686565e846f762 (MD5) Previous issue date: 2009 / Resumo: Os sistemas de aquecimento solar disponíveis comercialmente, embora proporcionem boa economia de energia elétrica, não apresentam bom desempenho em dias com baixa radiação, pois o boiler é automaticamente preenchido com água fria toda vez que ocorre consumo de água quente. Neste trabalho é proposto e estudado um sistema de aquecimento solar que é otimizado para proporcionar uma mínima utilização da energia elétrica no auxílio ao aquecimento de água. Um controlador fuzzy analisa a intensidade da radiação solar, a temperatura da água dentro do boiler, a quantidade de água dentro do boiler e controla a entrada de água fria no boiler, otimizando o sistema. Foram modelados dois sistemas de aquecimento: um convencional e este sistema com o controlador fuzzy; e, através de simulações, suas eficiências foram comparadas. Os resultados obtidos em simulação mostram que o sistema proposto com controlador fuzzy apresenta eficiência superior aos sistemas convencionais. Para um período de três dias de inverno, com baixa radiação solar, o sistema convencional consumiu uma energia elétrica de 10,08 kWh enquanto que o sistema proposto consumiu apenas 1,86 kWh. / Abstract: Although significant savings in electrical energy are achieved with commercially available solar water heaters, they do not present a good performance in days that the radiation is not good, because the boiler is filled with cold water whenever the hot water is used. In this work, a new solar heating system, which minimizes the use of electrical energy, is proposed. The proposed system uses a fuzzy controller that analyzes the intensity of solar radiation, the temperature of the water inside the boiler and the volume of water inside the boiler, to actuate on a On/Off valve which controls the boiler's input of cold water. Two solar heating systems were modeled: a conventional system and the new proposed system with the fuzzy controller; and their efficiencies were compared using computer simulations. The obtained results show that the proposed system with the fuzzy controller presents a much higher performance when compared to the traditional system. Simulation results indicate that for a three winter days period, with low intensity solar radiation, the conventional system consumed 10.08 kwh of electrical energy while the proposed system needed only 1.86 kwh to achieve the same performance. / Universidade Estadual de Campi / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica

The diploma thesis studies the elaboration of project about optimization of solar system for all- season service. The aim of the work was to make a proportioning, choosing the right parts and finding the economic and ecologic balance.

Klimatet och samhället förändras hela tiden och medvetenheten för konsekvenserna ökar. Genom att utnyttja alla tillgängliga delar i en energieffektivisering blir det möjligt att minska den tillförda energin till fastigheten. Detta arbete kommer belysa den potentiella energin i solen som kan utnyttjas för att värma upp fastigheter och andra resurser som har ett värmebehov. Rapporten kommer titta på hur solfångare kan bidra med värmeenergi till Hedlunda förskola. Med hjälp av beräkningar kommer lutningen på solfångarna visa vilka skillnader som framkommer gällande energimängd samt när energin går att nyttja. För att kunna besvara syftet med projektet kommer tre frågeställningar besvaras:  ·       Är det möjligt att minska energibehovet med 2,5 kWh/m2 med hjälp av solfångare? ·       Är det ekonomiskt lönsamt att använda solfångare för att minska energibehovet? ·       Hur löser man ett eventuellt problem med överhettning när energin inte utnyttjas under sommaren? Den metod som har använts för att undersöka solfångarnas tillförda energi är främst via beräkningar i Excel. För att få en ökad förståelse har litteraturstudier och informativa webbplatser använts. Avslutningsvis så visade resultatet att det är fullt möjligt att minska energibehovet årligen med 2,5 kWh/m2 eller 4 625 kWh totalt med solfångare.  Det framkommer att det inte är ekonomiskt lönsamt att använda sig av solfångare i den undersökta fastigheten. Detta beror till stor del på att den nuvarande uppvärmningen uppnås med relativt billig fjärrvärme. Att fjärrvärmen dessutom är billigast under sommaren då solfångarna är mest produktiva försvårar lönsamheten ytterligare. Det finns ett antal tekniska lösningar som gör det möjligt att undvika överhettning och kokning i systemet vilket möjliggör för en installation av solfångare. Sammanfattningsvis är det möjligt att använda sig av solfångare för att komma ner till energinivåer för ett internationellt certifierat passivhus. Solfångare kan vara intressant för Umeå Kommun trots att det inte är ekonomiskt lönsamt. En installation av solfångare kan ge Umeå Kommun mer kunskap om hur solfångare fungerar i praktiken samt vara ett budskap att man satsar på innovativitet och framtiden. / The climate and society are constantly changing, and awareness of the consequences of both is increasing. By utilizing energy efficient solutions, it will be possible to reduce the energy supplied to the system. This work will highlight the potential energy in the sunlight that can be used to heat structures and other facilities that have a heating demand. The report will look at how solar collectors can contribute thermal energy to Hedlunda preschool. By means of various calculations, the tilt angle of the solar collectors will show what differences appear in the current amount of energy and when the energy can be used. To fulfill the purpose of the project, three questions will be answered: ·        Is it possible to reduce the energy demand by 2.5 kWh/m2 with the help of solar collectors? ·        Is it economically profitable to use solar collectors to reduce external energy demand? ·        How do you solve a possible problem with overheating when the energy is not used during summer?  The method that has been used to investigate the solar energy supply is primarily calculations in Excel. To gain a better understanding, literature studies and informational websites have been used. In conclusion, the results showed that it is quite possible to reduce the yearly energy demand by 2.5 kWh/m2 living space or 4,625 kWh total with solar collectors. However, using solar panels in the investigated property is not financially profitable. This is largely because the heating is currently managed by a cheap district heating. Furthermore, the fact that district heating is at its cheapest during summer when solar collectors are most productive further complicates profitability. There are several technical solutions that make it possible to avoid overheating and boiling in the system, which allows for the installation of solar panels. In summary, it is possible to use solar collectors to reduce energy levels to an international certified passive house standard. Solar collectors can be interesting for Umeå Kommun even though it is not financially profitable. An installation of solar collectors can give Umeå Kommun more knowledge about how solar collectors work in practice and be a message that they are investing in innovation and the future.

Thesis (MEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: This study investigates the implementation of the finite volume numerical method applicable to non-orthogonal control volumes and the application of the method to calculate the thermo-flow field within the collector area of a solar chimney power generating plant. The discretisation of the governing equations for the transient, Newtonian, incompressible and turbulent fluid flow, including heat transfer, is presented for a non-orthogonal coordinate frame. The standard k - E turbulence model, modified to include rough surfaces, is included and evaluated in the method. An implicit solution procedure (SIP-semi implicit procedure) as an alternative to a direct solution procedure for the calculation of the flow field on nonstaggered grids is investigated, presented and evaluated in this study. The Rhie and Chow interpolation practice was employed with the pressurecorrection equation to eliminate the presence of pressure oscillations on nonstaggered grids. The computer code for the solution of the three-dimensional thermo-flow fields is developed in FORTRAN 77. The code is evaluated against simple test cases for which analytical and experimental results exist. It is also applied to the analysis of the thermo-flow field of the air flow through a radial solar collector. KEYWORDS: NUMERICAL METHOD, FINITE VOLUME, NON-ORTHOGONAL, k+-e TURBULENCE MODEL, SIP / AFRIKAANSE OPSOMMING: Die studie ondersoek die implementering van 'n eindige volume numeriese metode van toepassing op nie-ortogonale kontrole volumes asook die toepassing van die metode om die termo-vloei veld binne die kollekteerder area van 'n sonskoorsteen krag aanleg te bereken. Die diskretisering van die behoudsvergelykings vir die tyd-afhanlike, Newtonse, onsamedrukbare en turbulente vloei, insluitende hitteoordrag, word beskryf vir 'n nie-ortogonale koordinaatstelsel. Die standaard k - E turbulensiemodel, aangepas om growwe oppervlakrandvoorwaardes te hanteer, is ingesluit en geevalueer in die studie. 'n Implisiete oplossings metode (SIP-semi implisiete prosedure) as alternatief vir 'n direkte oplossingsmetode is ondersoek en geimplimenteer vir die berekening van die vloeiveld met nie-verspringde roosters. 'n Rhie en Chow interpolasie metode is gebruik tesame met die drukkorreksie-vergelyking ten einde ossilasies in die drukveld in die nie-verspringde roosters te vermy. Die rekenaarkode vir die oplossing van die drie dimensionele termo-vloeiveld is ontwikkel in FORTRAN 77. Die kode is geevalueer teen eenvoudige toetsprobleme waarvoor analitiese en eksperimentele resultate bestaan. Die kode IS ook gebruik om die termo-vloeiveld binne 'n radiale son kollekteerder te analiseer. SLEUTELWOORDE: NUMERIESE METODE, EINDIGE VOLUME, NIE-ORTOGONAAL, k - E TURBULENSIE MODEL, SIP

Tyrimų tikslas – nustatyti saulės kolektoriaus orui šildyti panaudojimo galimybes ruošiant džioviklį, vaistiniams ir prieskoniniams augalams džiovinti. Darbe apžvelgti vaistinių ir prieskoninių augalų džiovinimo rėžimai, šiuo metu Lietuvoje ir pasaulyje žinomi konservavimo būdai, saulės kolektorių konstrukcijos ir saulės energijos parametrai. Tyrimai atlikti džiovykloje su saulės kolektoriumi ir nustatyta temperatūros pokyčiai pučiant orą per saulės kolektorių orui šildyti ir saulės energijos kiekis krentantis į saulės kolektoriaus orui šildyti absorberį, esant įvairioms klimatinėms sąlygoms. / Purpose of the study – the solar collector to heat air drying potential in the preparation, medicinal herbs and dried. Review the work of medicinal herbs and drying modes, now in Lithuania and the world-known preservation techniques, solar design and solar energy parameters. Investigations were carried out with the dryer and the solar collector temperature changes by blowing air through the solar air heating and solar energy entering the solar collector to heat air absorbers under various climatic conditions.