This study investigated different underground bulk air heat exchanger (>100 m3/s) design criteria. It was found that no single document exist covering these heat exchangers and therefore the need was identified to generate a guideline with decision analyser steps to arrive at a technical specification. The study investigated the factors influencing the heat exchanger designs (spray chambers, towers and indirect-contact heat exchangers) and the technical requirements for each. The decision analysers can be used to generate optimised user-friendly fit-for-purpose bulk air heat exchanger (air cooler and heat rejection) designs. The study was tested against a constructed air cooler and heat rejection unit at a copper mine. It was concluded that the decision analysers were used successfully. It is recommended design engineers use these decision analysers to effectively design other heat exchangers. / Dissertation (MEng)--University of Pretoria, 2013. / gm2014 / Mining Engineering / unrestricted

<p>The latent-heat-storage capacity in Phase-Change Materials can be used for storing or releasing energy within a small temperature interval. Upon the phase transition taking place in a narrow temperature span, the material takes up or releases more energy compared to sensible heat storage. For an ideal phase-change material, the transition temperature is a single value, but for the most common phase-change materials on the market, used in building applications, the transition temperature is distributed within a temperature range of several degrees.</p><p>Integration of phase-change materials in building applications can be effected in several ways, for example by impregnating phase-change materials into porous building materials like concrete, wallboards, bricks or complements of the building structure. Integrating storages filled with phase-change materials makes other implementations, for instance accumulating tanks or envelopes as presented in this thesis, in an air heat exchanger. An appropriate phasetransition temperature of the supposed application is critical to the functionality of the material. For example, in cooling applications, the transition temperature of the material should be a few degrees lower than the requested comfort temperature in the building, and the opposite for heating applications.</p><p>In order to assess the thermal properties and the durability of the material, a watercalorimetric equipment was developed and employed in an accelerated testing programme. The heat capacity of the material and in particular possible change in the heat capacity over time, after thermal cycling of the material, were measured. In the thermal cycling of the material from solid to liquid phase, the temperature rise and required energy supply were recorded. The testing programme was undertaken according to control procedures and documents. In order to be able to utilize the heat-storage capacity in the best way, it is necessary to gain knowledge about thermal properties of the material, especially the long-term behaviour of the material and the deterioration rates of the thermal properties.</p><p>A semi-full-scale air heat exchanger based on phase-change material was developed and tested under real temperature conditions during the summer of 2004. The test results were used to compare and verify computer simulations made on a similar plant. The air heat exchanger utilises the ambient diurnal temperature swing to charge and discharge the phasechange material. The material tested in the calorimeter and in the air heat exchanger has an estimated phase-change temperature of about 24 °C.</p>

The latent-heat-storage capacity in Phase-Change Materials can be used for storing or releasing energy within a small temperature interval. Upon the phase transition taking place in a narrow temperature span, the material takes up or releases more energy compared to sensible heat storage. For an ideal phase-change material, the transition temperature is a single value, but for the most common phase-change materials on the market, used in building applications, the transition temperature is distributed within a temperature range of several degrees. Integration of phase-change materials in building applications can be effected in several ways, for example by impregnating phase-change materials into porous building materials like concrete, wallboards, bricks or complements of the building structure. Integrating storages filled with phase-change materials makes other implementations, for instance accumulating tanks or envelopes as presented in this thesis, in an air heat exchanger. An appropriate phasetransition temperature of the supposed application is critical to the functionality of the material. For example, in cooling applications, the transition temperature of the material should be a few degrees lower than the requested comfort temperature in the building, and the opposite for heating applications. In order to assess the thermal properties and the durability of the material, a watercalorimetric equipment was developed and employed in an accelerated testing programme. The heat capacity of the material and in particular possible change in the heat capacity over time, after thermal cycling of the material, were measured. In the thermal cycling of the material from solid to liquid phase, the temperature rise and required energy supply were recorded. The testing programme was undertaken according to control procedures and documents. In order to be able to utilize the heat-storage capacity in the best way, it is necessary to gain knowledge about thermal properties of the material, especially the long-term behaviour of the material and the deterioration rates of the thermal properties. A semi-full-scale air heat exchanger based on phase-change material was developed and tested under real temperature conditions during the summer of 2004. The test results were used to compare and verify computer simulations made on a similar plant. The air heat exchanger utilises the ambient diurnal temperature swing to charge and discharge the phasechange material. The material tested in the calorimeter and in the air heat exchanger has an estimated phase-change temperature of about 24 °C. / QC 20101123

<p>Rapporten handlar om ett examensarbete omfattande 20 p som är utfört för Thermia AB i Arvika. Uppdragsgivaren ville få fram förslag på möjliga åtgärder som kan minska ljudnivån från en luftvärmeväxlare. För bra helhetsbild av projektet, läs även kapitel: 6.</p><p>Värmeväxlaren ingår som en komponent i ett värmepumpssystem, Thermia Aer 5, som använder uteluften som värmekälla. Huvudmålet med projektet blev alltså att undersöka och utvärdera ljudbildningen från värmeväxlaren samt att komma fram till olika förslag på möjliga åtgärder som har potential att sänka ljudnivån. Värmeväxlarens förmåga att uppta energi fick ej heller försämras.</p><p>I projektets slutskede tillverkades det också en enkel prototyp på ett av designförslagen där den störande ljudnivån blev lägre. Läs mer om detta längre ner.</p><p>Ett delmål som vi själva formulerade, var också att undersöka olika möjligheter att öka värmepumpssystemets totala kapacitet för energiupptagning genom att kombinera systemet med någon form av solfångare. Kombinationen solfångare och luftvärmeväxlare innebär också en lägre ljudnivå eftersom fläkten i värmeväxlaren mer sällan behöver gå på full effekt. I viss mån har även estetiska aspekter på formgivningen beaktats.</p><p>Nedan presenteras fyra olika förslag på idéer för att öka luftvärmeväxlarens prestanda:</p><p>Av det första förslaget tillverkades en prototyp där luftvärmeväxlarens utblås är riktat uppåt, istället för som nu åt sidan, vilket minskar risken att omgivningen nås av högfrekvent ljud. Högfrekvent ljud sprids nämligen inte så mycket i sidled.</p><p>Batteridelen på värmeväxlaren har fått en större area, vilket möjliggör ett minskat volymflöde av luft, utan att den tappar i effekt, jämfört med nuvarande värmeväxlare.</p><p>Dessa två åtgärder reducerar det avgivna ljudet med ca10 dB.</p><p>En större batteriarea är även positivt ur energisynpunkt då värmefaktorn (COP) ökar på grund av ett minskat antal nödvändiga avfrostningar.</p><p>Förslag nummer två inbegriper en solfångarlösning som, tack vare avsaknaden av direktförångning, även går att direktkoppla till köldbäraren (brinen) eller direkt mot värmepumpens ackumulatortank.</p><p>Solfångaren täcker hela effektbehovet på sommaren och ger ett tillskott resten av året.</p><p>Det tredje förslaget är en s.k. väggplacerad luftsolfångare som förvärmer insugsluften till värmeväxlaren. Den uppenbara fördelen med detta alternativ är den synnerligen enkla konstruktionen vilket gör att kostnaden kan hållas nere, se bild 4.4.4-2.</p><p>Det fjärde förslaget, är att låta hela husets tak fungera som en solfångare som bilderna 6-1 visar. Inströmmande luft till värmeväxlaren förvärms av de soluppvärmda takpannorna som kan vara av tegel, betong eller ännu hellre av glas. Dessutom tillvaratas förlustvärme från hustak och ventilation. Detta förslag ger ett mycket gott energiutbyte.</p><p>Ytterligare ett intressant sätt att sänka ljudbildningen är att driva fram luften genom värmeväxlaren, helt eller delvis, med hjälp av en hög elektrisk spänning, se kapitel: 6.6.</p> / <p>This report is a candidate degree and the assignment is done in the interest of Thermia AB in Arvika, Sweden. The company wanted proposals of preventive measures aiming to reduce sound emission from a heat exchanger. For a good general impression of the project, see chapter 6. The heat exchanger forms a part of a component in a heat pump system, called Thermia Aer 5, which uses air from outside as a heat source.</p><p>The main target of the project was to examine and evaluate sound emission from the heat exchanger and to get different proposals on possible preventive measures in order to lower sound emission. It was not allowed to reduce the heat exchangers ability to collect energy.</p><p>In the end of the project a simple prototype was built which took advantage of some of the design proposals. The sound emission from the prototype was reduced.</p><p>Another target, formulated by ourselves, was to examine different possibilities to increase the capacity of the heat pump system by combining it with solar collectors. The heat pump system combined with solar collectors also produces reduced sound emission.</p><p>Even some aesthetic aspects have been taken into consideration.</p><p>Below, four different proposals of ideas are introduced that can increase the performance of the heat exchanger:</p><p>The first solution was to direct the air exhaust upwards instead of the tangential exhaust on the present heat exchanger. This makes it more improbable that a high frequency sound wave should reach the surrounding area. Sound with high frequency doesn’t spread so much in a sideways direction. An increase of the battery area makes it possible to lower the air volume flow, because of the increased potential for energy output. These two measures reduced the sound level with a proximal amount of about 10 dB. In addition, an increased exchange battery area increases the heat factor (COP) due to the frost distribution on the battery.</p><p>Solution number two include a solar panel that, due to the lack of direct vaporization in the heat pump system, is possible to serial connect direct on the brine or indirectly to the water accumulation tank. The solar panel gives hot water in the summer and an additional energy output the rest of the year.</p><p>The third solution is a wall mounted air solar panel which gives the air a higher input temperature to the air heat exchanger. This is a very simple and cost effective solution.</p><p>The fourth solution is to let the whole roof of the house act as a solar collector as the pictures 6-1 describes. The sun heats the roofing tile which, in turn, heats streaming air that reaches the heat exchanger. The tile can been made of tiling, concrete - or preferably - transparent glass. Furthermore heat loss from the roof and ventilation is prevented.</p><p>Another interesting solution that reduces sound emission is to force air through the exchanger with a high electric voltage field. Further information chapter: 6.6.</p>

Rapporten handlar om ett examensarbete omfattande 20 p som är utfört för Thermia AB i Arvika. Uppdragsgivaren ville få fram förslag på möjliga åtgärder som kan minska ljudnivån från en luftvärmeväxlare. För bra helhetsbild av projektet, läs även kapitel: 6. Värmeväxlaren ingår som en komponent i ett värmepumpssystem, Thermia Aer 5, som använder uteluften som värmekälla. Huvudmålet med projektet blev alltså att undersöka och utvärdera ljudbildningen från värmeväxlaren samt att komma fram till olika förslag på möjliga åtgärder som har potential att sänka ljudnivån. Värmeväxlarens förmåga att uppta energi fick ej heller försämras. I projektets slutskede tillverkades det också en enkel prototyp på ett av designförslagen där den störande ljudnivån blev lägre. Läs mer om detta längre ner. Ett delmål som vi själva formulerade, var också att undersöka olika möjligheter att öka värmepumpssystemets totala kapacitet för energiupptagning genom att kombinera systemet med någon form av solfångare. Kombinationen solfångare och luftvärmeväxlare innebär också en lägre ljudnivå eftersom fläkten i värmeväxlaren mer sällan behöver gå på full effekt. I viss mån har även estetiska aspekter på formgivningen beaktats. Nedan presenteras fyra olika förslag på idéer för att öka luftvärmeväxlarens prestanda: Av det första förslaget tillverkades en prototyp där luftvärmeväxlarens utblås är riktat uppåt, istället för som nu åt sidan, vilket minskar risken att omgivningen nås av högfrekvent ljud. Högfrekvent ljud sprids nämligen inte så mycket i sidled. Batteridelen på värmeväxlaren har fått en större area, vilket möjliggör ett minskat volymflöde av luft, utan att den tappar i effekt, jämfört med nuvarande värmeväxlare. Dessa två åtgärder reducerar det avgivna ljudet med ca10 dB. En större batteriarea är även positivt ur energisynpunkt då värmefaktorn (COP) ökar på grund av ett minskat antal nödvändiga avfrostningar. Förslag nummer två inbegriper en solfångarlösning som, tack vare avsaknaden av direktförångning, även går att direktkoppla till köldbäraren (brinen) eller direkt mot värmepumpens ackumulatortank. Solfångaren täcker hela effektbehovet på sommaren och ger ett tillskott resten av året. Det tredje förslaget är en s.k. väggplacerad luftsolfångare som förvärmer insugsluften till värmeväxlaren. Den uppenbara fördelen med detta alternativ är den synnerligen enkla konstruktionen vilket gör att kostnaden kan hållas nere, se bild 4.4.4-2. Det fjärde förslaget, är att låta hela husets tak fungera som en solfångare som bilderna 6-1 visar. Inströmmande luft till värmeväxlaren förvärms av de soluppvärmda takpannorna som kan vara av tegel, betong eller ännu hellre av glas. Dessutom tillvaratas förlustvärme från hustak och ventilation. Detta förslag ger ett mycket gott energiutbyte. Ytterligare ett intressant sätt att sänka ljudbildningen är att driva fram luften genom värmeväxlaren, helt eller delvis, med hjälp av en hög elektrisk spänning, se kapitel: 6.6. / This report is a candidate degree and the assignment is done in the interest of Thermia AB in Arvika, Sweden. The company wanted proposals of preventive measures aiming to reduce sound emission from a heat exchanger. For a good general impression of the project, see chapter 6. The heat exchanger forms a part of a component in a heat pump system, called Thermia Aer 5, which uses air from outside as a heat source. The main target of the project was to examine and evaluate sound emission from the heat exchanger and to get different proposals on possible preventive measures in order to lower sound emission. It was not allowed to reduce the heat exchangers ability to collect energy. In the end of the project a simple prototype was built which took advantage of some of the design proposals. The sound emission from the prototype was reduced. Another target, formulated by ourselves, was to examine different possibilities to increase the capacity of the heat pump system by combining it with solar collectors. The heat pump system combined with solar collectors also produces reduced sound emission. Even some aesthetic aspects have been taken into consideration. Below, four different proposals of ideas are introduced that can increase the performance of the heat exchanger: The first solution was to direct the air exhaust upwards instead of the tangential exhaust on the present heat exchanger. This makes it more improbable that a high frequency sound wave should reach the surrounding area. Sound with high frequency doesn’t spread so much in a sideways direction. An increase of the battery area makes it possible to lower the air volume flow, because of the increased potential for energy output. These two measures reduced the sound level with a proximal amount of about 10 dB. In addition, an increased exchange battery area increases the heat factor (COP) due to the frost distribution on the battery. Solution number two include a solar panel that, due to the lack of direct vaporization in the heat pump system, is possible to serial connect direct on the brine or indirectly to the water accumulation tank. The solar panel gives hot water in the summer and an additional energy output the rest of the year. The third solution is a wall mounted air solar panel which gives the air a higher input temperature to the air heat exchanger. This is a very simple and cost effective solution. The fourth solution is to let the whole roof of the house act as a solar collector as the pictures 6-1 describes. The sun heats the roofing tile which, in turn, heats streaming air that reaches the heat exchanger. The tile can been made of tiling, concrete - or preferably - transparent glass. Furthermore heat loss from the roof and ventilation is prevented. Another interesting solution that reduces sound emission is to force air through the exchanger with a high electric voltage field. Further information chapter: 6.6.

Objetivos: Este trabalho, abrangendo a área da transferência de calor e da mecânica dos fluidos, em seu desenvolvimento envolveu métodos analíticos, numéricos computacionais e experimentais (em ambiente de campo), com a finalidade de analisar o uso de trocadores de calor solo-ar, como estratégia para diminuir o consumo de energia convencional, no aquecimento ou resfriamento de ambientes construídos. Assim, um dos objetivos do estudo foi avaliar, com base em resultados experimentais, a performance do solo como um reservatório de energia, derivada da radiação solar. Buscou-se, pois, identificar parâmetros, procedimentos e condições favoráveis envolvendo esta estratégia. O outro objetivo do estudo foi, usando os softwares GAMBIT e FLUENT, modelar computacionalmente o escoamento do ar no trocador de calor solo-ar. Método: O estudo experimental e numérico foi precedido pela construção de uma edificação, especificamente concebida para a pesquisa, identificada como Casa Ventura. Em continuidade, foram enterrados dutos no solo, que conduziriam ar exterior e água (esta última por um período limitado) ao ambiente interno. No caso da condução de ar, o solo funcionaria como um reservatório de energia, aquecendo ou resfriando a ar. Já, no caso da condução de água, prevista com duto de baixa condutividade térmica, o solo funcionaria apenas como um protetor à radiação solar, para preservar as características térmicas da água, desde um reservatório, de onde a mesma era bombeada, até o interior da casa. Na Casa Ventura foram construídos dois ambientes centrais com características dimensionais e de envolvente equivalentes, constituindo os ambientes monitorados no processo, sendo um, na condição natural, referencial, sem renovação de ar, e o outro, com renovação de ar. Na parte experimental, o ar foi captado do ambiente externo e insuflado por um ventilador nos dutos enterrados, renovou o ar no interior deste último ambiente. Com ajuda de um fan-coil, colocado neste ambiente, o ar renovado trocou calor com a água. Por questões de dificuldades operacionais, o bombeamento de água funcionou por um período muito curto. Durante o experimento, que se desenvolveu por todo o ano de 2007, foram monitoradas e registradas, além da temperatura do solo e da água, a temperatura e a umidade: do ar externo, do ar nos ambientes internos e do ar em escoamento nos dutos enterrados, bem como a velocidade de escoamento nos mesmos. Resultados: De forma geral, o potencial do solo para aquecer foi maior do que o de resfriamento do ar injetado nos dutos enterrados. O potencial de aquecimento foi mais destacado nos meses de maio, junho, julho e agosto, e se mostrou maior que 3K. Para profundidades entre 2 e 3m, estima-se que o potencial possa ser superior a 8K. Por outro lado, o potencial de resfriamento foi maior nos meses de janeiro, fevereiro e dezembro, mas foi baixo para pequenas profundidades (menos de um metro). Para resfriamento, este potencial pode chegar a 4K. Contribuições da pesquisa: Face aos resultados da pesquisa, diversas foram as suas contribuições, dentre as quais se destacam: a construção de um banco de dados experimentais sobre as propriedades e características do solo (índices físicos, difusividade térmica, capacidade térmica volumétrica, condutividade térmica, temperatura e umidade) e do ar ambiente (temperatura e umidade) para o município de Viamão, localizado na região sul do Brasil, e que pode ser usado para a continuidade desta pesquisa ou para a elaboração de novas pesquisas e projetos; e o desenvolvimento de uma metodologia para a modelagem computacional de trocadores de calor solo-ar, validada através dos dados experimentais citados acima, possibilitando, assim, o emprego deste procedimento numérico, para a elaboração de projetos ou novas pesquisas nesta área. / Purpose: The development of the present work, comprising the area of heat transfer and fluids mechanics involved analytical, numerical computational and experimental (in field environment) methods, with the purpose of analyzing the use of earth-to-air heat exchanger, as a strategy to reduce conventional energy consumption, for the heating or cooling of built environments. Thus, one of the study purposes was to evaluate, based on experimental results, the earth performance as an energy reservoir, derived from solar radiation incidence on the surface of the ground. We aimed, then, at identifying favorable parameters, procedures and conditions involving this strategy. The other study purpose was, using the GAMBIT and FLUENT softwares, computationally modeling the air flow in the earth-to-air heat exchanger. Method: The experimental and numerical study was preceded by the construction of a building, specially planned for the research, called Casa Ventura. As a follow-up, ducts were buried on the ground, to conduct external air and water (the latter one for a limited period) to the internal environment of the house. In terms of air conduction, the earth would work as an energy reservoir, heating or cooling the air. Concerning the water conduction, planned to use a duct of low thermal conductivity, the earth would only work as a protector from solar radiation, to preserve the water thermal characteristics, when flowing from the water reservoir, where it would be taken from, to the inside of the house. At Casa Ventura two central environments were built with similar dimensional and envelope characteristics, constituting the environments monitored in the process, in which, one in the natural and referential condition, without air renovation, and the other, with air renovation. In the experimental part, the air was captured from the external environment and inflated by a fan in the buried ducts, and it renovated the air inside this latter environment. With the help of a fan-coil, placed in this environment, the renovated air exchanged heat with the water flowing through the ducts. Due to some operational difficulties, the pumping of water lasted for a very short period. During the experiment, which lasted through the whole year of 2007, besides the water and earth temperature, the temperature and humidity of the following were also monitored and registered: the external air, the air in the internal environments and the air flowing in the buried ducts, as well as the flowing speed of the different fluids. Results: In a general way, the earth potential to heat was higher than the cooling of air injected in the buried ducts. The heating potential was higher in the months of May, June, July and August, doing so by more 3K. For depths between 2 and 3m, it is estimated that the potential might be over 8K. On the other hand, the potential for cooling was higher in the months of January, February and December, but it was low for low depths (less than a meter). For cooling, this potential may reach 4K. Research contributions: Considering the research results, several were the contributions, among which we highlight: the construction of an experimental database on the earth properties and characteristics (physical indexes, thermal diffusivity, volumetric heat capacity, thermal conductivity, temperature and humidity) and the environmental characteristics of the air (temperature and humidity) for the city of Viamão, located in Southern Brazil, and that may be used for the continuation of this research or for the elaboration of new researches and projects; and the development of a methodology for computational modeling of earth-to-air heat exchangers, validated through the experimental data mentioned before, enabling, therefore, the use of this numerical procedure for the elaboration of projects or new researches in this area.

Objetivos: Este trabalho, abrangendo a área da transferência de calor e da mecânica dos fluidos, em seu desenvolvimento envolveu métodos analíticos, numéricos computacionais e experimentais (em ambiente de campo), com a finalidade de analisar o uso de trocadores de calor solo-ar, como estratégia para diminuir o consumo de energia convencional, no aquecimento ou resfriamento de ambientes construídos. Assim, um dos objetivos do estudo foi avaliar, com base em resultados experimentais, a performance do solo como um reservatório de energia, derivada da radiação solar. Buscou-se, pois, identificar parâmetros, procedimentos e condições favoráveis envolvendo esta estratégia. O outro objetivo do estudo foi, usando os softwares GAMBIT e FLUENT, modelar computacionalmente o escoamento do ar no trocador de calor solo-ar. Método: O estudo experimental e numérico foi precedido pela construção de uma edificação, especificamente concebida para a pesquisa, identificada como Casa Ventura. Em continuidade, foram enterrados dutos no solo, que conduziriam ar exterior e água (esta última por um período limitado) ao ambiente interno. No caso da condução de ar, o solo funcionaria como um reservatório de energia, aquecendo ou resfriando a ar. Já, no caso da condução de água, prevista com duto de baixa condutividade térmica, o solo funcionaria apenas como um protetor à radiação solar, para preservar as características térmicas da água, desde um reservatório, de onde a mesma era bombeada, até o interior da casa. Na Casa Ventura foram construídos dois ambientes centrais com características dimensionais e de envolvente equivalentes, constituindo os ambientes monitorados no processo, sendo um, na condição natural, referencial, sem renovação de ar, e o outro, com renovação de ar. Na parte experimental, o ar foi captado do ambiente externo e insuflado por um ventilador nos dutos enterrados, renovou o ar no interior deste último ambiente. Com ajuda de um fan-coil, colocado neste ambiente, o ar renovado trocou calor com a água. Por questões de dificuldades operacionais, o bombeamento de água funcionou por um período muito curto. Durante o experimento, que se desenvolveu por todo o ano de 2007, foram monitoradas e registradas, além da temperatura do solo e da água, a temperatura e a umidade: do ar externo, do ar nos ambientes internos e do ar em escoamento nos dutos enterrados, bem como a velocidade de escoamento nos mesmos. Resultados: De forma geral, o potencial do solo para aquecer foi maior do que o de resfriamento do ar injetado nos dutos enterrados. O potencial de aquecimento foi mais destacado nos meses de maio, junho, julho e agosto, e se mostrou maior que 3K. Para profundidades entre 2 e 3m, estima-se que o potencial possa ser superior a 8K. Por outro lado, o potencial de resfriamento foi maior nos meses de janeiro, fevereiro e dezembro, mas foi baixo para pequenas profundidades (menos de um metro). Para resfriamento, este potencial pode chegar a 4K. Contribuições da pesquisa: Face aos resultados da pesquisa, diversas foram as suas contribuições, dentre as quais se destacam: a construção de um banco de dados experimentais sobre as propriedades e características do solo (índices físicos, difusividade térmica, capacidade térmica volumétrica, condutividade térmica, temperatura e umidade) e do ar ambiente (temperatura e umidade) para o município de Viamão, localizado na região sul do Brasil, e que pode ser usado para a continuidade desta pesquisa ou para a elaboração de novas pesquisas e projetos; e o desenvolvimento de uma metodologia para a modelagem computacional de trocadores de calor solo-ar, validada através dos dados experimentais citados acima, possibilitando, assim, o emprego deste procedimento numérico, para a elaboração de projetos ou novas pesquisas nesta área. / Purpose: The development of the present work, comprising the area of heat transfer and fluids mechanics involved analytical, numerical computational and experimental (in field environment) methods, with the purpose of analyzing the use of earth-to-air heat exchanger, as a strategy to reduce conventional energy consumption, for the heating or cooling of built environments. Thus, one of the study purposes was to evaluate, based on experimental results, the earth performance as an energy reservoir, derived from solar radiation incidence on the surface of the ground. We aimed, then, at identifying favorable parameters, procedures and conditions involving this strategy. The other study purpose was, using the GAMBIT and FLUENT softwares, computationally modeling the air flow in the earth-to-air heat exchanger. Method: The experimental and numerical study was preceded by the construction of a building, specially planned for the research, called Casa Ventura. As a follow-up, ducts were buried on the ground, to conduct external air and water (the latter one for a limited period) to the internal environment of the house. In terms of air conduction, the earth would work as an energy reservoir, heating or cooling the air. Concerning the water conduction, planned to use a duct of low thermal conductivity, the earth would only work as a protector from solar radiation, to preserve the water thermal characteristics, when flowing from the water reservoir, where it would be taken from, to the inside of the house. At Casa Ventura two central environments were built with similar dimensional and envelope characteristics, constituting the environments monitored in the process, in which, one in the natural and referential condition, without air renovation, and the other, with air renovation. In the experimental part, the air was captured from the external environment and inflated by a fan in the buried ducts, and it renovated the air inside this latter environment. With the help of a fan-coil, placed in this environment, the renovated air exchanged heat with the water flowing through the ducts. Due to some operational difficulties, the pumping of water lasted for a very short period. During the experiment, which lasted through the whole year of 2007, besides the water and earth temperature, the temperature and humidity of the following were also monitored and registered: the external air, the air in the internal environments and the air flowing in the buried ducts, as well as the flowing speed of the different fluids. Results: In a general way, the earth potential to heat was higher than the cooling of air injected in the buried ducts. The heating potential was higher in the months of May, June, July and August, doing so by more 3K. For depths between 2 and 3m, it is estimated that the potential might be over 8K. On the other hand, the potential for cooling was higher in the months of January, February and December, but it was low for low depths (less than a meter). For cooling, this potential may reach 4K. Research contributions: Considering the research results, several were the contributions, among which we highlight: the construction of an experimental database on the earth properties and characteristics (physical indexes, thermal diffusivity, volumetric heat capacity, thermal conductivity, temperature and humidity) and the environmental characteristics of the air (temperature and humidity) for the city of Viamão, located in Southern Brazil, and that may be used for the continuation of this research or for the elaboration of new researches and projects; and the development of a methodology for computational modeling of earth-to-air heat exchangers, validated through the experimental data mentioned before, enabling, therefore, the use of this numerical procedure for the elaboration of projects or new researches in this area.

Objetivos: Este trabalho, abrangendo a área da transferência de calor e da mecânica dos fluidos, em seu desenvolvimento envolveu métodos analíticos, numéricos computacionais e experimentais (em ambiente de campo), com a finalidade de analisar o uso de trocadores de calor solo-ar, como estratégia para diminuir o consumo de energia convencional, no aquecimento ou resfriamento de ambientes construídos. Assim, um dos objetivos do estudo foi avaliar, com base em resultados experimentais, a performance do solo como um reservatório de energia, derivada da radiação solar. Buscou-se, pois, identificar parâmetros, procedimentos e condições favoráveis envolvendo esta estratégia. O outro objetivo do estudo foi, usando os softwares GAMBIT e FLUENT, modelar computacionalmente o escoamento do ar no trocador de calor solo-ar. Método: O estudo experimental e numérico foi precedido pela construção de uma edificação, especificamente concebida para a pesquisa, identificada como Casa Ventura. Em continuidade, foram enterrados dutos no solo, que conduziriam ar exterior e água (esta última por um período limitado) ao ambiente interno. No caso da condução de ar, o solo funcionaria como um reservatório de energia, aquecendo ou resfriando a ar. Já, no caso da condução de água, prevista com duto de baixa condutividade térmica, o solo funcionaria apenas como um protetor à radiação solar, para preservar as características térmicas da água, desde um reservatório, de onde a mesma era bombeada, até o interior da casa. Na Casa Ventura foram construídos dois ambientes centrais com características dimensionais e de envolvente equivalentes, constituindo os ambientes monitorados no processo, sendo um, na condição natural, referencial, sem renovação de ar, e o outro, com renovação de ar. Na parte experimental, o ar foi captado do ambiente externo e insuflado por um ventilador nos dutos enterrados, renovou o ar no interior deste último ambiente. Com ajuda de um fan-coil, colocado neste ambiente, o ar renovado trocou calor com a água. Por questões de dificuldades operacionais, o bombeamento de água funcionou por um período muito curto. Durante o experimento, que se desenvolveu por todo o ano de 2007, foram monitoradas e registradas, além da temperatura do solo e da água, a temperatura e a umidade: do ar externo, do ar nos ambientes internos e do ar em escoamento nos dutos enterrados, bem como a velocidade de escoamento nos mesmos. Resultados: De forma geral, o potencial do solo para aquecer foi maior do que o de resfriamento do ar injetado nos dutos enterrados. O potencial de aquecimento foi mais destacado nos meses de maio, junho, julho e agosto, e se mostrou maior que 3K. Para profundidades entre 2 e 3m, estima-se que o potencial possa ser superior a 8K. Por outro lado, o potencial de resfriamento foi maior nos meses de janeiro, fevereiro e dezembro, mas foi baixo para pequenas profundidades (menos de um metro). Para resfriamento, este potencial pode chegar a 4K. Contribuições da pesquisa: Face aos resultados da pesquisa, diversas foram as suas contribuições, dentre as quais se destacam: a construção de um banco de dados experimentais sobre as propriedades e características do solo (índices físicos, difusividade térmica, capacidade térmica volumétrica, condutividade térmica, temperatura e umidade) e do ar ambiente (temperatura e umidade) para o município de Viamão, localizado na região sul do Brasil, e que pode ser usado para a continuidade desta pesquisa ou para a elaboração de novas pesquisas e projetos; e o desenvolvimento de uma metodologia para a modelagem computacional de trocadores de calor solo-ar, validada através dos dados experimentais citados acima, possibilitando, assim, o emprego deste procedimento numérico, para a elaboração de projetos ou novas pesquisas nesta área. / Purpose: The development of the present work, comprising the area of heat transfer and fluids mechanics involved analytical, numerical computational and experimental (in field environment) methods, with the purpose of analyzing the use of earth-to-air heat exchanger, as a strategy to reduce conventional energy consumption, for the heating or cooling of built environments. Thus, one of the study purposes was to evaluate, based on experimental results, the earth performance as an energy reservoir, derived from solar radiation incidence on the surface of the ground. We aimed, then, at identifying favorable parameters, procedures and conditions involving this strategy. The other study purpose was, using the GAMBIT and FLUENT softwares, computationally modeling the air flow in the earth-to-air heat exchanger. Method: The experimental and numerical study was preceded by the construction of a building, specially planned for the research, called Casa Ventura. As a follow-up, ducts were buried on the ground, to conduct external air and water (the latter one for a limited period) to the internal environment of the house. In terms of air conduction, the earth would work as an energy reservoir, heating or cooling the air. Concerning the water conduction, planned to use a duct of low thermal conductivity, the earth would only work as a protector from solar radiation, to preserve the water thermal characteristics, when flowing from the water reservoir, where it would be taken from, to the inside of the house. At Casa Ventura two central environments were built with similar dimensional and envelope characteristics, constituting the environments monitored in the process, in which, one in the natural and referential condition, without air renovation, and the other, with air renovation. In the experimental part, the air was captured from the external environment and inflated by a fan in the buried ducts, and it renovated the air inside this latter environment. With the help of a fan-coil, placed in this environment, the renovated air exchanged heat with the water flowing through the ducts. Due to some operational difficulties, the pumping of water lasted for a very short period. During the experiment, which lasted through the whole year of 2007, besides the water and earth temperature, the temperature and humidity of the following were also monitored and registered: the external air, the air in the internal environments and the air flowing in the buried ducts, as well as the flowing speed of the different fluids. Results: In a general way, the earth potential to heat was higher than the cooling of air injected in the buried ducts. The heating potential was higher in the months of May, June, July and August, doing so by more 3K. For depths between 2 and 3m, it is estimated that the potential might be over 8K. On the other hand, the potential for cooling was higher in the months of January, February and December, but it was low for low depths (less than a meter). For cooling, this potential may reach 4K. Research contributions: Considering the research results, several were the contributions, among which we highlight: the construction of an experimental database on the earth properties and characteristics (physical indexes, thermal diffusivity, volumetric heat capacity, thermal conductivity, temperature and humidity) and the environmental characteristics of the air (temperature and humidity) for the city of Viamão, located in Southern Brazil, and that may be used for the continuation of this research or for the elaboration of new researches and projects; and the development of a methodology for computational modeling of earth-to-air heat exchangers, validated through the experimental data mentioned before, enabling, therefore, the use of this numerical procedure for the elaboration of projects or new researches in this area.

La conception des bâtiments à faible consommation d'énergie est devenue un enjeu très important à travers le monde afin de minimiser la consommation d'énergie et les émissions de gaz à effet de serre associés. Au Maroc, le secteur du bâtiment représente 25% de la consommation énergétique finale du pays avec 18% réservée au résidentiel et 7% pour le tertiaire (ADEREE 2011). L'intégration de systèmes passifs ou semi-passifs de rafraîchissement/chauffage dans le bâtiment est désormais indispensable pour la réduction de la consommation énergétique tout en améliorant le confort thermique. Un de ces systèmes est l’échangeur air-sol (EAHX). Le principe du rafraîchissement à l'aide de l’échangeur air-sol est bien établi, mais le comportement d'un tel système dépend des conditions climatiques et de la nature du sol. L’échangeur air-sol étudié est installé dans une maison type villa située dans la banlieue de Marrakech. Un monitoring de ce système a été réalisé durant l’été 2013 à travers un suivi des températures et de l'humidité durant 39 jours. Les résultats montrent que l’échangeur air-sol est un système adapté pour le rafraîchissement de l’air dans les bâtiments à Marrakech, puisqu’il procure une température de soufflage quasi-constante d’environ 22°C pour le débit 244 m3/h et 25°C pour le débit de 312m3/h, avec une humidité relative autour de 50 % alors que la température extérieure dépasse 40°C. Le modèle mathématique choisi et l’outil de simulation associé, Type 460 opérant sous le logiciel commercial TRNSYS, sont analysés et validés par confrontation avec les résultats expérimentaux. Cette confrontation a montré une excellente concordance, avec un écart absolu moyen entre la mesure et la simulation toujours inférieur à 0,5°C et décroit à 0,2°C à la sortie de tube enterré. La validation de l’outil de simulation avec un échangeur air-sol enterré dans un sol soumis à conditions météorologiques extérieures n’a pas été réalisée auparavant. D'autre part, les simulations dynamiques de l’échangeur air-sol sont réalisées en fonctionnement continu, avec 1 et 3 tubes durant la période chaude de l’année (mai-septembre). Les résultats montrent que le système procure une température à la sortie de tube enterré de 25,1°C (1 tube) et 26 °C (3 tubes). Il en résulte une capacité de refroidissement de 58w/m2 (1 tube) et 55w/m2 (3 tubes) pour une température à l’entrée de 44,6°C. Une étude de sensibilité, utilisant la méthode de Sobol, de la performance thermique de l'échangeur durant la saison chaude (mai-septembre) a permis de dégager les paramètres les plus influents. Par la suite, une étude paramétrique complète sur l’énergie sensible totale perdue par l’air lors dans son passage dans l’échangeur air-sol est réalisée en fonction des paramètres les plus influents déterminés auparavant. / The low energy buildings tendency has become a major worldwide key to minimize energy consumption and greenhouse gas emissions issues. In Morocco, the building sector represents 25% of the total final energy consumption, whereas 18% is dedicated for residential and 7% for the tertiary sector (ADEREE 2011). The integration of passive or semi-passive for cooling/heating purposes into buildings is an essential act for reducing energy consumption while improving thermal comfort. One of these systems is the Earth to Air Heat Exchanger (EAHX). Its principle to use the ground-coupled heat exchanger for cooling is well established, but the behavior of such a system depends on the climate and the soil, which influences the choice of design parameters of this system. We performed a numerical and experimental study on the thermal performance of an Earth to air heat exchanger installed in a villa type house in the suburbs of Marrakech. A monitoring survey was conducted during the summer period of 2013, to acquire temperature and humidity measurements for 39 days. The results show that the earth to air heat exchanger is a system more adapted to refresh the air in buildings in Marrakech, as it provides a quasi constant air temperature of approximately 22°C for flow 244 m3/h and 25°C for flow of 312 m3/h, with relative humidity that is around 50% when the outside temperature exceeds 40°C. The mathematical model chosen and the associated simulation tool used is Type 460 operating under the TRNSYS commercial software, analyzed and validated by comparison with experimental results. This comparison showed excellent agreement, with an average absolute difference between the measurement and simulation that is always lower than 0.5°C and 0.2°C as it decreases at the output of the buried pipe. On the other hand, dynamic simulations of the EAHX using TRNSYS software (TYPE 460) were performed with one pipe or three pipes continuously running. The achieving specific cooling capacity is 58 W/m2 (one pipe) and 55 W/m2 (three pipes) obtained for air temperatures of 25 °C and 26 °C respectively, at the EAHX outlet and 44.6 °C at its inlet. A sensitivity analysis, using the method of Sobol, of the thermal performance of the earth air heat exchanger (EAHX) in the hot season (May-September) has identified the most influential parameters. Thereafter, a complete parametric study on the total sensible energy lost through the air when in passing through the air-ground heat exchanger is made based on the most influential parameters determined previously.

Cette thèse porte sur l’analyse thermique et énergétique d’une fondation géothermique ventilée. A l’instar des échangeurs air-sol classiques (EAHE), celle-ci permet de rafraichir ou préchauffer selon la saison l’air destiné au renouvellement sanitaire des bâtiments. Face aux contraintes de rationalisation des consommations et aux exigences de confort thermique croissantes, ces systèmes passifs apparaissent comme étant prometteurs. Le principe de cette fondation est simple et similaire à celui des EAHE : faire circuler de l’air dans une conduite enterrée dans le sol (un à trois mètres) pour qu’il bénéficie - via convection - de l’inertie thermique du sol. La différence réside dans le fait que le canal dans lequel circule l’air n’est pas un tube en PVC ou aluminium mais fait partie intégrante de la structure du bâtiment, à savoir la fondation en béton armé. Ceci présente comme avantage majeur le gain de place lié à l’espace requis pour l’enfouissement des tuyaux. D’un point de vue thermique, la fondation échange non seulement de la chaleur avec le sol exposé aux sollicitations météorologiques mais aussi, et simultanément, aux sollicitations venant du bâtiment. De plus, la profondeur de la fondation – imposée par des raisons structurelles et économiques – est moindre que pour un EAHE traditionnel. Additionné au fait que le béton est poreux, la présence d’humidité peut fortement influencer la performance thermique de la fondation. Le présent travail propose donc d’étudier le comportement thermique complexe de cette fondation par deux approches. La première est expérimentale : un EHPAD équipé de deux fondations a été lourdement instrumenté et des données ont été accumulées sur plus d’un an. L’autre est numérique : deux modèles validés par comparaison avec les données expérimentales ont été développés. Le premier a vocation d’outil de dimensionnement, l’autre de compréhension fine des phénomènes physiques et prends en compte les transferts couplés de chaleur et de masse. / This thesis deals with the thermal and energy analysis of a geothermal ventilated fonudation. Similarly to earth-to-air heat exchangers (EAHE) this foundation enables, according to the season, to preheat or to cool down the air for the hygienic air change. Considering the energy consumption constraints and the buildings users thermal comfort desire, these systems appears to be relevant. The principle of this foundation is simple: to force the air to circulate in a hollowed beam buried into the ground (1 to 3m depth) so that it takes advantage - via convection - to the thermal inertia of the ground. The difference lays on the fact that the channel is not a plastic or aluminium pipe but it a part of the building structure, namely the reinforced concrete foundation. This induces a significant space gain, usually devoted to the pipe burying. From a thermal point of view, the foundation exchanges heat with both the soil beneath the building, and with the soil exposed to the weather thermal loads. Furthermore, the depth - imposed by structural and economical purposees - is lower than that of traditional EAHE. In addition to the fact that concrete is a porous material, the humidity content may strongly influence the thermal performance of the foundation. The current work thus proposes to study the complex thermal behaviour of this foundation in two ways. The first is experimental: an retirement home equipped with two foundation has been intensively instrumented and data recorded over more than one year. The other is numerical: two models validated against the experimental data have been developed. The first is intended to be a designing tool, the second a tool to allow a fine comprehension of the physical phenomenon and take into account coupled heat and moisture transfers.