The high energy density and stable temperature fields of latent heat thermal storage devices (LHTSD) make them promising in a range of applications, including solar energy storage, solar cooking, home heating and cooling, and thermal buffering. The chief engineering challenge in building an effective LHTSD is to find a way to complement the storage capabilities provided by the low-conductivity phase-change material with a suitable enhanced heat transfer mechanism. The principal aim of this project is to develop a tool to improve the design of a small-scale LHTSD, such as one that might be used in solar cooking for a family. An effective small-scale storage device would need to absorb solar energy quickly, release the energy at a high temperature, be affordable, and be manageable within a small household. An LHTSD using solar salts fulfills the latter two requirements: solar salts, a near-eutectic mixture of NaNO3 and KNO3 (60/40% by mass) commonly used in thermal storage applications, are inexpensive and widely available, and the use of latent heat storage means a relatively small chamber can hold enough energy to cook a family meal. The challenge, however, is to design a device that absorbs and releases energy from the solar salts, which have a very low thermal conductivity. The most practical tool to improve the spread of heat through the salts is a finned metal core within the LHTSD. This project uses numerical simulation to determine the most effective design of this finned core. A Cartesian grid solver is developed that is capable of simulating the convection-dominated melting processes within the storage device. The phase boundary is tracked using the enthalpy method, and conjugate heat transfer is calculated with a strongly coupled implicit scheme. A number of techniques are then used to with this solver in order to better understand the factors that affect the performance of a LHTSD and to improve the design of such devices. The thesis is organized as an introductory section followed by three case studies. In the first section, the project is introduced, and the governing equations and core numerical methods are described. In addition, a set of test simulations demonstrate that results using the developed numerical scheme match those of a range of experimental and numerical benchmarks. Each of the case studies aims to adapt the numerical scheme to a more specific problem concerning LHTSDs. In the first, the performance of four fin designs are compared over long-term (48 hour) simulations; the aim is to test the potential performance of the four LHTSDs given realistic solar conditions in New Delhi, India. In the second case study, a set of physical experiments are performed in an empty and a finned LHTSD, and matched 3-dimensional numerical simulations are used to explore the thermal, melt, and flow behavior of the solar salts with the chambers. The final study uses the computational scheme to optimize the design of the finned core of an LHTSD over a large parameter space. To optimize the best design, the key parameters are first prescreened to find which three parameters have the largest effect on the objective equation. A machine-learning optimization code using the dynamic Kriging method (DKG) is then used to build a response surface from which the optimized design can be determined. These three cases demonstrate the potential of the numerical scheme to explore the performance of finned LHTSD designs in a range of ways: the scheme can be used to predict behavior of devices in realistic conditions, to explore the behavior of solar salts during the melting and solidification process, and to determine an optimal design within a large parameter space. In doing so, they show the potential of this tool to help improve the performance and practicality of small-scale LHTSDs.

No description available.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / Extensive research and development activities have been conducted to explore opportunities for sustainable and viable methods of producing potable water using solar energy. This project included a new configuration for the solar cooker with indirect heating, which also operates as a desalination unit. The objective was to develop a new cooking pan which could be coupled with a three-stage desalination tower. Thus, the pan could be used for cooking or as the storage tank of the desalination tower. This new pan was installed in a solar cooker with indirect heating and the complete system was tested under field conditions. The sealing was improved, and the system produced more than 5.7L, with electrical conductivity lower than 10ÂS/cm, COP, 1.77 and GOR, 0,35, values consistent with the literature and above the values obtained with the original pan. / Extensivas atividades de pesquisa e desenvolvimento vÃm sendo conduzidas para explorar oportunidades de mÃtodos sustentÃveis e viÃveis de produÃÃo de Ãgua potÃvel utilizando energia solar. Este projeto abrange uma nova configuraÃÃo para o fogÃo solar com aquecimento indireto operar tambÃm como dessalinizador. O objetivo foi desenvolver uma nova panela que pode ser acoplada com uma torre de trÃs estÃgios de dessalinizaÃÃo. Assim, a panela pode ser utilizada tanto para cozinhar ou como o tanque de armazenamento da torre de dessalinizaÃÃo. Esta nova panela foi instalada em um fogÃo solar com aquecimento indireto e todo o sistema foi testado em condiÃÃes de campo. O acoplamento foi otimizado, aumentando a produÃÃo total em relaÃÃo ao projeto anterior. O sistema produziu mais de 5,7L de Ãgua dessalinizada, com condutividade elÃtrica mÃdia abaixo de 10ÂS/cm, COP, 1,77 e GOR 0,35, valores compatÃveis com a literatura e acima dos valores obtidos com a panela original.

Orientador: Prof. Dr. João Batista de Aguiar / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Mecânica, 2016. / No Haiti, bem como em regiões do norte e nordeste do Brasil, os recursos florestais são utilizados como lenha ou transformado em carvão vegetal para fins de cocção, principalmente pela população de baixa renda. Através desta ideia, este trabalho é desenvolvido apresentando um conceito de um fogão solar acessível de tipo caixa, utilizando materiais de baixo custo e técnicas simples de construção. A fim de desenvolver uma primeira análise de ordem do fogão, o problema de transferência de calor transiente é formulado e o sistema de equações diferenciais são escritos e resolvidos. Diferentes cenários e parâmetros são considerados para compreender a importância do problema. Foram utilizadas dimensões, formas e materiais alternativos ao apresentado na literatura. Um modelo físico do fogão solar foi construído no local em questão "Haiti" e medições de temperaturas realizadas e comparadas com as previsões numéricas. A partir da analise dos resultados, chegou-se às conclusões. Outras adições à solução também foram incluídas, a resposta obtida foi demostrada, de forma a apresentar se os resultados são aceitáveis. / In Haiti as well as in northern and northeastern of Brazil, forest resources are used as wood or transformed into charcoal for cooking, mostly by poor people. Through this idea, this work presents a concept of an affordable box type solar oven, using cheap materials and easy construction techniques. In order to develop a first order analysis of the oven, the transient heat transfer problem is formulated, the system of differential equations written and solved. Different scenarios and parameters are used to understand the importance to the problem. Variations range from dimensions, forms and materials. A physical model of the oven is constructed in locus "Haiti" and temperature measurements performed and compared to numerical predictions. The results are analyzed and conclusions drawn. Other additions to the solution are included, obtained answer is presented in order to show whether it is acceptable.

CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior / This work presents two new prototypes of a circular desalinator operation in a solar cooker for indirect heating. The first prototype, called Type A, produces desalinated water from brackish water deposited in the pan solar cooker. In the second prototype, the Type B, the brackish water pan is used only as a means of transfering heat to the first tray tower desalination. These prototypes were fabricated and tested in LESGN (Solar Energy Laboratory and Natural Gas). Its structure consists of stainless steel plates, trays with circular and inclined downwards (with circular trays to facilitate the flow of condensed water) and "pipes" (that harvest desalinated water and take out the stages and side rails, harvesting the water that condenses the side walls). The desalting tower was formed by a set of trays to facilitate the handling and operation. The experiments were conducted between 7.00am and 5.00pm and the maximum number of stages was three. Experiments with 2 and 3 stages confirmed the heat recovery process, in other words, the repeated use of the heat stored in the desalinated water in a lower stage by stage above. The experimental results showed that the maximum production were daily for the Type A, 4.72 L with 3 stages, and the desalinator Type B 3.50 L also with 3 stages. It was found that the efficiency of desalination type A was greater than that of Type B, which explains why Type B has a further resistance to heat transfer. On the other hand, Type B prototype allows continued operation of the desalination tower, not requiring the dismantling after each emptying process of the water in the pan / Este trabalho apresenta dois novos protÃtipos de um dessalinizador circular para operaÃÃo em um fogÃo solar de aquecimento indireto. O primeiro protÃtipo, denominado Tipo A, produz Ãgua dessalinizada a partir da Ãgua salobra depositada na panela do fogÃo solar. No segundo protÃtipo, o Tipo B, a Ãgua salobra da panela à usada apenas como meio de transferÃncia de calor para a primeira bandeja da torre de dessalinizaÃÃo. Estes protÃtipos foram fabricados e testados no LESGN (LaboratÃrio de Energia Solar e GÃs Natural). Sua estrutura à formada por chapas de aÃo inoxidÃvel com bandejas circulares e inclinadas para baixo, com bandejas circulares para facilitar o escoamento da Ãgua condensada, âcachimbosâ, que colhem a Ãgua dessalinizada e levam para fora dos estÃgios e calhas laterais, que colhem a Ãgua que condensa pelas paredes laterais. A torre de dessalinizaÃÃo foi formada por um conjunto de bandejas para facilitar o manuseio e operaÃÃo. Os experimentos foram realizados entre 7 e 17 hs e o nÃmero mÃximo de estÃgios foi trÃs. Os experimentos com 2 e 3 estÃgios confirmaram o processo de recuperaÃÃo de calor, ou seja, a utilizaÃÃo repetida do calor armazenado na Ãgua dessalinizada em um estÃgio inferior pelo estÃgio superior. Os resultados experimentais mostraram que as mÃximas produÃÃes diÃrias foram, para o Tipo A, de 4,72 L com 3 estÃgios, e para o dessalinizador Tipo B, 3,50 L com 3 estÃgios. Verificou-se que a eficiÃncia do dessalinizador Tipo A era superior ao do Tipo B, o que se explica por o Tipo B ter uma resistÃncia a transferÃncia de calor a mais. Por outro lado, o protÃtipo Tipo B permite uma operaÃÃo continuada da torre de dessalinizaÃÃo, nÃo sendo necessÃrio a sua desmontagem apÃs cada esvaziamento da Ãgua na panela.

M.Tech. (Industrial Design) / This study investigated the user’s perspective with reference to the regular use of the WonderbagTM retained-heat cooker in low-income communities in a South African context. This research addresses the limitations of the literature available to support the investigation of the design of a fabric retained-heat cooker from a user’s perspective. As with the WonderbagTM retained-heat cooker, products aimed at underserved low-income communities are often designed without the participation of the end-user. This research focuses on the user’s experience of the fabric retained-heat cooker and seeks to include the user in the process of improving the design of these products. Participatory action research and user-centred design were utilised as the chosen methodologies for this study. The history of retained-heat cookers has been reflected upon when considering the use of insulation materials and alternative fabric improvements. Methods of manufacture, material cost and usage have been considered as critical elements of the design process as well as the skill level of the existing users. Participants indicated their personal interest in the design and development of the prototype retained-heat cooker. They were intensively involved in the design process from the focus group discussion where their perceptions were elicited, right through to their testing of the final prototype. A final workshop concluded the last of three workshops where participants provided individual feedback in terms of their personal experiences of using the prototype retained-heat cooker. Participants were able to selectively customise their prototypes, which brought about a sense of ownership and pride that was not evident in their use of previous retained-heat cookers. Participants indicated personal interest in creating their own retained-heat cookers from the experience that they acquired during the research process. As a result of this experience, the participants believed that they could manufacture their own retained-heat cookers to sell within their community, which could provide income for themselves and other members of their community. The saving of energy in terms of the fuel required to complete the cooking process translated into a direct saving of money, which was highlighted as a recurring theme and identified benefit of retained-heat cooking. By encouraging the use of energy-efficient retained-heat cookers, low-income communities could directly benefit from spending less on fuel costs and more on other essentials.

This thesis introduces an analysis and dimensioning of a solar powered solution for enabling clean and sustainable cooking in developing areas. Access to clean cooking is a great  challenge  hindering human development, with significant health, environmental, and economic implications. The proposed solution is analysed and modelled in this work. Recommendations are given on the development of the project, reviewing the critical factors for its success. The solution is a novel approach for providing power for cooking through solar energy. Targeted market segment is institutional cooking, where current cooking fuels are commonly based on firewood and charcoal. The system integrates a solar trough collector array, an oil heat storage,     a heating unit for the cooking recipient, and two thermosiphons for transporting the heat between each component. The technology is under development, requiring an accurate analysis and further work in the design. The work presented analyses the solution and its implementation in a specific case study. A modelling software was built as a tool for dimensioning the technology and observing its behaviour. Moreover, specific values were obtained on the dimensions for the case study. A structured critic of the system through a deep review allowed for observations on risks, future work, and additional recommendations. Simulations for the case study enabled the first values on the dimensions of the system. Flexibility of the model was provided to repeat this exercise for future case studies. The analysis unexpected critical factors for the solution such as user behaviour and reviewed expected ones such as the insulation or the size of the heat storage. There are still many challenges to overcome for the success of the analyzed project. This thesis gives a basis for future work and strong guidance for the development of the solution.

The non-profit organization Project Vita has recently built a maternity clinic in Linga Linga, where the medical instruments to be sterilized are boiled in water for an hour. The fuel needed to boil the water is wood, which is a scarce resource. This is why, according to the healthcare worker that was interviewed in Mozambique, it is desirable to have an electric-powered solution to sterilise the medical instruments. After research on the different sterilization techniques that exist, the conclusion was drawn that the safest way to sterilise is by the use of an autoclave. However, it would be difficult to implement and maintain an autoclave in Linga Linga. Therefore, it was proposed to build an autoclave using a pressure cooker. Through experimentation, different programs, times and pressures were tested to find out if a pressure cooker could sterilise a common object. It could be concluded that theoretically, it seems that the pressure cooker reached a temperature of over 121 degrees Celsius. However, the pressure could not be measured nor was a biological indicator, that could indicate if an autoclave or pressure cooker does sterile, used.  This project was to be done in Mozambique, but because of COVID-19, a travel ban was set in motion and universities and laboratories had limited access, thus limiting the project. As a result, it is still unclear if a pressure cooker can be used to sterilize medical instruments. / Detta arbete ingår som en del av Project Vitas arbete med en förlossningsklinik i Linga Linga, Moçambique.

Detta projekt är ett samarbete mellan Hampus Nilsson och Joto Solutions, projektet är ett examensarbete för Högskoleingenjörsexamen i innovationsteknik och design, MSGC12 vid fakulteten för hälsa, natur- och teknikvetenskap på Karlstads universitet. Studenten ska tillsammans med Joto Solutions utveckla kokenheten på deras solkokare. Projektet motsvarar 22.5 hp och utförs under vårterminen 2017. Handledare i projektet är Lennart Wihk, universitetsadjunkt, och examinator är Leo De Vin, professor. Joto Solutions AB startades våren 2015 i samband med två examensarbeten som initierades av Adam Fjaestad i Arvika. Under 2016/2017 avser Joto Solutions att göra en satsning på att utveckla och produktifiera solkokaren som sedan ska testas i fält. Målet med projektet att utveckla en design på solkokarens kokenhet som är väl anpassad för slutanvändaren. Frågeställningen som behandlas i rapporten är ”Hur ska solkokarens kokenhet utformas för att tillfredsställa slutanvändarens behov”. Projektet följer ett ingenjörs- och industridesignmässigt arbetssätt och grundar sig i produktutvecklingsprocessen. De faser som behandlas i detta projekt är projektplanering, förstudie, produktspecifikation, konceptgenerering, konceptval och layoutkonstruktion. Projektet resulterade i tre stycken kokenheter med varierande design som redovisas i layoutkonstruktionsfasen. Det finns utrymme för framtida vidareutveckling av de tre variationerna av kokenheten i form av konstruktionsförbättringar och säkerhetstillhörigheter. / This project is a collaboration between a student and the company Joto Solutions and is a degree work for a degree of bachelor in the field of innovation and design, MSGC12 at Karlstad University, Faculty of Health, Science and Technology. The student, together with Joto Solutions, will develop the cooking unit on their solar cooker. The project is equivalent to 22.5 ECTS credits and is being executed in the spring of 2017. Supervisor of the project is Lennart Wihk, a university lecturer, and the examiner is Leo De Vin, the professor. Joto Solutions AB was founded in the spring of 2015 in connection with two degree projects initiated by Adam Fjaestad in Arvika. In 2016/2017, Joto Solutions intends to make an effort to develop their solar cooker which will then be tested in the field. The aim of the project is to develop a design on the solar cooker's cooking unit that is well adapted to the end user needs. The question discussed in the report is "How should the solar cooker's cooking unit be designed to satisfy the end user's needs in a cultural and functional perspective." The project follows an engineering and industrial design practice and is based on the product development process. The phases covered in this project are project planning, preliminary study, product specification, concept generation, concept selection, layout design and risk analysis. The project resulted in three cooking units with varying designs that are presented in the layout design phase. There is room for further development of the three variations of cooking units in the form of design improvements and safety issues.

Made available in DSpace on 2014-12-17T14:58:07Z (GMT). No. of bitstreams: 1 MiguelCMN_DISSERT.pdf: 16186905 bytes, checksum: 2eff0d12f0947aff6c9902b788587ee5 (MD5) Previous issue date: 2011-05-30 / It is presented a solar cooker made with a parabolic reflector composed by a composite material. For this purpose, it was utilized a cast concrete with a parabolic profile obtained by means of modeling. It will be demonstrated the manufacturing process and settings, as well as tests results, in order to determine the contact temperature and cooking time of some foods. This solar cooker presents the following main characteristics: the concentration method, low cost and easy manufacturing process. It was performed by employing recycled materials such as cement, plaster, crushed polystyrene and wheels. The captation area measures 1 square meter and its parabole was covered with a mirrors measuring 25 cm2. A temperature higher than 650?C was obtained. Furthermore, it has been demonstrated that the cooking viability for several type of foods such as beans, potatoes, rice, yams and pasta can be used in two meals for a family of four. In addition, the advantages of this cooker were analysed in comparison with others described in literature as well as those operating on gas. Especially in Northeast of Brazil, where there is a potential for solar energy, this prototype is an important tool, because it avoids not only desertification, but also pollutants from burning firewoods which cause ecological imbalance / Apresenta-se um fog?o solar a concentra??o com par?bola refletora constru?da com um material comp?sito. Foi utilizado um molde de concreto com perfil parab?lico obtido atrav?s da modelagem. Ser?o apresentados os processos de fabrica??o e montagem bem como os resultados de testes para determinar a temperatura de contacto e os tempos de cozedura de certos tipos de alimentos. O fog?o solar a concentra??o tem como principal caracter?stica seu custo baixo, sendo produzidos a partir de uma composi??o de materiais reutiliz?veis, como cimento, gesso e EPS triturado e pneus. Apresenta ?rea de capta??o de 1,0 metro quadrado e sua par?bola foi coberto com segmentos de espelhos de 25 cm?. As principais carracter?sticas do fog?o solar ? concentra??o propostas s?o seus f?ceis processos de fabrica??o, montagem e seu baixo custo. Obteve-se temperatura de foco superioor a 650?C. Demonstrou-se a viabilidade de coc??o desse fog?o solar para v?rios tipo de alimentos como feij?o, batata, arroz, inhame e macarr?o e podendo ser usado em duas refei??es para uma fam?lia de quatro pessoas. A competitividade do fog?o solar estudado com outros apontados pela literatura solar para coc??o de alimentos e at? mesmo com o fog?o a g?s para excelentes condi??es solarim?tricas. Este prot?tipo pode representar uma importante contribui??o para o uso de fog?es solares, especialmente no Nordeste, para o combate ? desertifica??o, e emiss?o de poluentes pelo uso massivo de lenha, que causa desequil?brio ecol?gico nessa regi?o