Este trabalho apresenta a otimização de sistemas de acumulação sensível de energia térmica, submetidos a fontes de energia intermitentes (solar). Este tipo de sistema de acumulação é definido pelo seu material de acumulação e pelo fluido de trabalho, que realiza o transporte da energia. A metodologia empregada consiste em aplicar o modelo da capacitância global para descrever o comportamento dinâmico do material de acumulação, disposto na forma de placas planas paralelas, enquanto que o fluido de trabalho foi modelado via balanço de energia. O material de acumulação foi dividido em diversas seções menores, de modo a satisfazer a condição de validade do modelo da capacitância global, resultando em números de Biot menores ou iguais a 0,1, para cada seção. Os parâmetros identificados para a otimização foram a geometria do material de acumulação (número de placas e volume), propriedades do material de acumulação (massa específica e calor específico) e vazão do fluido de trabalho. Definiu-se a função a ser minimizada como o módulo da diferença entre a taxa de energia de saída do sistema de acumulação e a taxa de energia de saída alvo. Os resultados para duas geometrias e materiais distintos (aço AISI304 e granito), foram comparados com simulações efetuadas com o software comercial COMSOL, e os desvios encontrados ficaram na faixa de 10,16% a 8,88% para o aço e de 1,45% a 0,25% para o granito. A formulação proposta neste trabalho foi implementada no programa Engineering Equation Solver (EES), e otimizada com algoritmos genéticos. Observou-se que a massa específica e o calor específico são parâmetros que podem ser avaliados pelo seu produto (capacidade térmica volumétrica), quando a massa do material de acumulação não foi fixada. Para os casos nos quais a massa foi definida, o calor específico e a massa específica devem ser considerados parâmetros independentes, pois cada um atuou de forma diferente sobre o sistema. Observou-se que aumentando a quantidade de parâmetros de otimização, a diferença entre a taxa de energia na saída e a mesma taxa alvo diminuiu. Na simulação com dois parâmetros de otimização, a diferença relativa máxima entre estas taxas foi de 50%, enquanto que para quatro parâmetros de otimização, este valor caiu para 24%. / This work presents the optimization of sensible heat storage system, subjected to intermittent energy sources (solar). This type of storage system is defined by its storage material and the working fluid, which transports the energy. The methodology consists of using the global capacitance method to describe the dynamic behavior of the storage material, disposed in the form of parallel flat plates, while the working fluid was modeled via an energy balance. The storage material was divided into several smaller sections in order to satisfy the validity condition of the global capacitance model, resulting in Biot numbers smaller or equal than 0.1 for each section. The optimized parameters were the geometry of the storage material (number of plates and volume), the storage material properties (mass and specific heat) and flow rate of the working fluid. The minimized objective function is the difference between the output energy rate of the storage system and the target output energy rate. The results for two different geometries and materials (steel AISI304 and granite), were compared to simulations performed with the commercial software COMSOL, and the deviations were found in the range of 10.16% to 8.88% for steel and 1,45% to 0.25% for granite. The formulation proposed in this paper is implemented in the Engineering Equation Solver (EES), and optimized with genetic algorithm. It was observed that the density and specific heat are parameters that can be evaluated for its product (volumetric heat capacity) when the mass of the storage material was not defined. For the cases where the mass was defined, the specific heat and the density should be considered independent parameters, as each one act differently in the system. It was observed that increasing the number of optimized parameters, the difference between the output energy rate and the same target rate decreased. In the simulation with two optimized parameters, the maximum relative difference between these rates was 50%, while for four optimized parameters, this value dropped to 24%.

Resumo: Foi estudada a eliminação de calor latente e estimado o fluxo térmico total ao sol e à sombra em cabras da raça Saanen mantidas em ambiente tropical, visando determinar importância da termólise evaporativa para esses animais e proporcionar subsídios para o estabelecimento de métodos de manejo em ambiente tropical. A evaporação total foi determinada por processo gravimétrico, usando-se um sistema de pesagem de precisão. A evaporação cutânea foi obtida por determinação direta através de uma cápsula ventilada; e a evaporação respiratória estimada a partir do fluxo térmico entre aparelho respiratório e o ambiente; determinaram-se ainda a estocagem térmica e as trocas convectivas e radiativas. Por ocasião de cada determinação, foram registradas a temperatura retal, a freqüência respiratória e a temperatura da superfície corporal, bem como variáveis ambientais: temperatura e umidade do ar, velocidade do vento e temperatura do globo negro. Foram avaliadas as características morfológicas do pelame (espessura da capa, comprimento médio, densidade numérica e ângulo dos pêlos) para cada animal. As análises estatísticas basearam-se no método dos quadrados mínimos para dados não-balanceados, tendo o modelo linear geral proposto incluído os efeitos: ambiente (fixo), animal (aleatório), interação animal x ambiente e regressão sobre a temperatura do ar, a umidade relativa, a temperatura radiante média, a temperatura da superfície corporal, a temperatura retal, a freqüência respiratória e a idade do animal, além das características morfológicas do pelame, no caso da evaporação cutânea. A termólise evaporativa compreendeu 61,5% da perda de calor para o ambiente, sendo a única via de perda térmica possível ao sol sob temperaturas radiante média acima de 35ºC...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The present work aimed at to study the elimination of latent heat and esteem the total thermal flow to the sun and the shade in Saanen goats in tropical environment, to determine importance of evaporative heat loss these animals and to provide subsidies for the establishment of methods of handling in tropical environment. The total evaporation was determined by means of gravimetrical process, for a weighing system of precision. The cutaneous evaporation was gotten by direct determination, by means of a ventilated capsule; the respiratory evaporation gotten by calculations of heat flow of respiratory device for environment. It was determined still the heat storage and the convective and radiative exchanges. For occasion of each determination, the rectal temperature, respiratory rate and surface temperature of the animal, as well as meteorological data: air temperature, relative humidity, wind speed and black globe temperature were register. The morphologic characteristics of the hair coat (coat thickness, hair length, numerical density and hair angle to skin) had been evaluated for each animal. The statistical analyses were carried through by the lest-squares method for not-balanced data. The considered model included the effect of environment and animal and the covariates: air temperature, relative humidity, mean radiating temperature, surface temperature, rectal temperature, respiratory rate and age of animal, beyond the morphologic characteristics of the hair coat for cutaneous evaporation. Heat loss evaporative understands 62.2% of the heat carried for environment exchange, being the way possible to the sun under radiant temperatures above of 35º...(Complete abstract, click electronic access below) / Orientador: Roberto Gomes da Silva / Coorientador: Danísio Prado Munari / Banca: Iran Jose Oliveira da Silva / Banca: Orlando Rus Barbosa / Banca: Isabel Cristina Boleli / Banca: Renato Luis Furlan / Doutor

Este trabalho apresenta a otimização de sistemas de acumulação sensível de energia térmica, submetidos a fontes de energia intermitentes (solar). Este tipo de sistema de acumulação é definido pelo seu material de acumulação e pelo fluido de trabalho, que realiza o transporte da energia. A metodologia empregada consiste em aplicar o modelo da capacitância global para descrever o comportamento dinâmico do material de acumulação, disposto na forma de placas planas paralelas, enquanto que o fluido de trabalho foi modelado via balanço de energia. O material de acumulação foi dividido em diversas seções menores, de modo a satisfazer a condição de validade do modelo da capacitância global, resultando em números de Biot menores ou iguais a 0,1, para cada seção. Os parâmetros identificados para a otimização foram a geometria do material de acumulação (número de placas e volume), propriedades do material de acumulação (massa específica e calor específico) e vazão do fluido de trabalho. Definiu-se a função a ser minimizada como o módulo da diferença entre a taxa de energia de saída do sistema de acumulação e a taxa de energia de saída alvo. Os resultados para duas geometrias e materiais distintos (aço AISI304 e granito), foram comparados com simulações efetuadas com o software comercial COMSOL, e os desvios encontrados ficaram na faixa de 10,16% a 8,88% para o aço e de 1,45% a 0,25% para o granito. A formulação proposta neste trabalho foi implementada no programa Engineering Equation Solver (EES), e otimizada com algoritmos genéticos. Observou-se que a massa específica e o calor específico são parâmetros que podem ser avaliados pelo seu produto (capacidade térmica volumétrica), quando a massa do material de acumulação não foi fixada. Para os casos nos quais a massa foi definida, o calor específico e a massa específica devem ser considerados parâmetros independentes, pois cada um atuou de forma diferente sobre o sistema. Observou-se que aumentando a quantidade de parâmetros de otimização, a diferença entre a taxa de energia na saída e a mesma taxa alvo diminuiu. Na simulação com dois parâmetros de otimização, a diferença relativa máxima entre estas taxas foi de 50%, enquanto que para quatro parâmetros de otimização, este valor caiu para 24%. / This work presents the optimization of sensible heat storage system, subjected to intermittent energy sources (solar). This type of storage system is defined by its storage material and the working fluid, which transports the energy. The methodology consists of using the global capacitance method to describe the dynamic behavior of the storage material, disposed in the form of parallel flat plates, while the working fluid was modeled via an energy balance. The storage material was divided into several smaller sections in order to satisfy the validity condition of the global capacitance model, resulting in Biot numbers smaller or equal than 0.1 for each section. The optimized parameters were the geometry of the storage material (number of plates and volume), the storage material properties (mass and specific heat) and flow rate of the working fluid. The minimized objective function is the difference between the output energy rate of the storage system and the target output energy rate. The results for two different geometries and materials (steel AISI304 and granite), were compared to simulations performed with the commercial software COMSOL, and the deviations were found in the range of 10.16% to 8.88% for steel and 1,45% to 0.25% for granite. The formulation proposed in this paper is implemented in the Engineering Equation Solver (EES), and optimized with genetic algorithm. It was observed that the density and specific heat are parameters that can be evaluated for its product (volumetric heat capacity) when the mass of the storage material was not defined. For the cases where the mass was defined, the specific heat and the density should be considered independent parameters, as each one act differently in the system. It was observed that increasing the number of optimized parameters, the difference between the output energy rate and the same target rate decreased. In the simulation with two optimized parameters, the maximum relative difference between these rates was 50%, while for four optimized parameters, this value dropped to 24%.

Energy storage with the help of different materials is something that has been around for a long time. Structures such as concrete or brick use their high thermal mass to store energy in the form of temperature increase, sensible heat, of the respective material. Energy storage in the form of sensible heat is relatively small in capacity, which means that large masses of building material are required to give a significant effect. Concrete, for example, requires 4 kJ/kg to increase in temperature by 1 °C. Now society has begun to look more closely at other materials that can be used for energy storage and temperature stabilization in buildings. Phase change materials are unique materials that use the change in phases between different aggregation states to store energy in the form of latent heat. It is mainly phase change between solid and liquid that is used since gaseous form would involve large volume changes. An everyday example of a material that undergoes a phase change is water. Water requires 334 kJ/kg to go from 0 ˚C ice (solid) to 0 ˚C water (liquid).  Water is a very powerful phase change material but cannot be used in buildings as it melts at 0 ˚C. Therefore, other materials have been developed to meet the requirement that the melting take place at the desired temperature, usually room temperature. The different phase change materials can be divided into three different groups: organic, inorganic and eutetic materials. All groups come with their own advantages and disadvantages. Organic materials are stable materials in the sense that they can phase change in repeated cycles which makes them the popular choice when it comes to buildings. One disadvantage that most organic materials possess is that they are flammable. The choice of phase change material will affect the quality of the building and it is therefore important that the knowledge about these materials is adopted before they become more widespread.

Made available in DSpace on 2014-06-11T19:33:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-10-24Bitstream added on 2014-06-13T20:05:37Z : No. of bitstreams: 1 oliveira_al_dr_jabo.pdf: 487509 bytes, checksum: 21986f8f6599c47af5da518d2f78570b (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Foi estudada a eliminação de calor latente e estimado o fluxo térmico total ao sol e à sombra em cabras da raça Saanen mantidas em ambiente tropical, visando determinar importância da termólise evaporativa para esses animais e proporcionar subsídios para o estabelecimento de métodos de manejo em ambiente tropical. A evaporação total foi determinada por processo gravimétrico, usando-se um sistema de pesagem de precisão. A evaporação cutânea foi obtida por determinação direta através de uma cápsula ventilada; e a evaporação respiratória estimada a partir do fluxo térmico entre aparelho respiratório e o ambiente; determinaram-se ainda a estocagem térmica e as trocas convectivas e radiativas. Por ocasião de cada determinação, foram registradas a temperatura retal, a freqüência respiratória e a temperatura da superfície corporal, bem como variáveis ambientais: temperatura e umidade do ar, velocidade do vento e temperatura do globo negro. Foram avaliadas as características morfológicas do pelame (espessura da capa, comprimento médio, densidade numérica e ângulo dos pêlos) para cada animal. As análises estatísticas basearam-se no método dos quadrados mínimos para dados não-balanceados, tendo o modelo linear geral proposto incluído os efeitos: ambiente (fixo), animal (aleatório), interação animal x ambiente e regressão sobre a temperatura do ar, a umidade relativa, a temperatura radiante média, a temperatura da superfície corporal, a temperatura retal, a freqüência respiratória e a idade do animal, além das características morfológicas do pelame, no caso da evaporação cutânea. A termólise evaporativa compreendeu 61,5% da perda de calor para o ambiente, sendo a única via de perda térmica possível ao sol sob temperaturas radiante média acima de 35ºC... / The present work aimed at to study the elimination of latent heat and esteem the total thermal flow to the sun and the shade in Saanen goats in tropical environment, to determine importance of evaporative heat loss these animals and to provide subsidies for the establishment of methods of handling in tropical environment. The total evaporation was determined by means of gravimetrical process, for a weighing system of precision. The cutaneous evaporation was gotten by direct determination, by means of a ventilated capsule; the respiratory evaporation gotten by calculations of heat flow of respiratory device for environment. It was determined still the heat storage and the convective and radiative exchanges. For occasion of each determination, the rectal temperature, respiratory rate and surface temperature of the animal, as well as meteorological data: air temperature, relative humidity, wind speed and black globe temperature were register. The morphologic characteristics of the hair coat (coat thickness, hair length, numerical density and hair angle to skin) had been evaluated for each animal. The statistical analyses were carried through by the lest-squares method for not-balanced data. The considered model included the effect of environment and animal and the covariates: air temperature, relative humidity, mean radiating temperature, surface temperature, rectal temperature, respiratory rate and age of animal, beyond the morphologic characteristics of the hair coat for cutaneous evaporation. Heat loss evaporative understands 62.2% of the heat carried for environment exchange, being the way possible to the sun under radiant temperatures above of 35º...(Complete abstract, click electronic access below)

Master of Science / Department of Agronomy / Jay Ham / The exchange of water, carbon, and energy between grasslands and the atmosphere is an important biogeochemical pathway affecting ecosystem productivity and sustainability. The eddy covariance (EC) technique directly measures this mass and energy exchange. However, questions remain regarding the accuracy of EC-derived H[subscript]2O and CO[subscript]2 fluxes in landscapes with irregular topography and variable vegetation. These concerns stem from the "energy balance (EB) closure problem" (i.e., measured energy in does not equal measured energy out). My main objectives were to examine EB closure at two topographical positions within an annually burned tallgrass prairie watershed and to examine the effect of landscape position and woody encroachment on carbon and water exchanges. In tallgrass prairie, 14 km south of Manhattan, KS, USA, EC towers were deployed at three sites in 2007 and 2008. One upland and lowland tower were within an annually burned watershed dominated by C[subscript]4 grasses. Another lowland tower was deployed in a separate quadrennial-burned watershed where significant woody vegetation occupied the tower's sampling area. All towers measured EB components (net radiation, R[subscript]n; soil heat flux, G; sensible heat flux, H; and latent heat flux, [lambda]E). In the annually burned watershed, landscape position had little effect on G, H, and R[subscript]n with differences [less than] 2% between sites. However lowland [lambda]E was 8% higher, owing to larger plant biomass/leaf area and greater soil moisture. Energy balance closure (i.e., [[lambda]E + H] / [R[subscript]n - G]) was 0.87 and 0.90 at the upland and lowland sites, respectively. A nearby large-aperture scintillometer provided good validation of EC-derived H in 2007. Data suggested that underestimates of [lambda]E may have accounted for the closure problem; sample calculations showed that increasing [lambda]E by 17% would have resulted in near prefect closure. Data from this study suggests that EB closure does not strongly correlate with topographical position; however these data raise questions regarding accuracy of the [lambda]E term. Mass exchange analysis shows that the prairie carbon cycle is highly dependent on burning. The lowland and upland annually burned sites saw carbon gains of 281 to 444 g C m[superscript]-[superscript]2 yr[superscript]-[superscript]1 before burning with the shrub lowland showing the least (e.g. 159 and 172 g C m[superscript]-[superscript]2 yr[superscript]-[superscript]1). After the prescribed burn, the upland and lowland sites remained slight carbon sinks (68 to 191 g C m[superscript]-[superscript]2 yr[superscript]-[superscript]1), whereas the unburned shrub site was a carbon sink in 2007 (159 g C m[superscript]-[superscript]2 yr[superscript]-[superscript]1, because no carbon loss was incurred via burning) and a large carbon source in 2008 when it was burned the following year (336 g C m[superscript]-[superscript]2 yr[superscript]-[superscript]1 loss). Evapotranspiration (ET) was highest at the shrub lowland where greater soil moisture and abundance of deep-rooted C[subscript]3 shrub vegetation allowed greater uptake and loss of water.

<p>Knowledge of the turbulent fluxes at the sea surface is important for understanding the interaction between atmosphere and ocean. With better knowledge, improvements in the estimation of the heat exchange coefficients can be made and hence models are able to predict the weather and future climate with higher accuracy.</p><p>The exchange coefficients of latent and sensible heat during stable stratification vary in the literature. Therefore it is necessary to investigate the processes influencing the air-sea exchange of water vapour and heat in order to estimate these values. With measurements from a tower and a directional waverider buoy at the site Östergarnsholm in the Baltic Sea, data used in this study have been sampled from the years 2005-2007. This site represents open-ocean conditions during most situations when the wind comes from the south-east sector. The neutral exchange coefficients, CEN and CHN, have been calculated along with the non-dimensional profile functions for temperature and wind to study the dependence of stability and other parameters of relevance.</p><p>It was found that CEN increased slightly with wind speed and reached a mean value of approximately 1.45×10-3. The highest values of CEN were observed during near neutral conditions and low wave ages. CHN attained a mean value of approximately 0.77×10-3 and did not show any relation to wind speed or to wave age. No significant dependence with wind or wave direction could be shown for either CEN or CHN in the sector 80-220°. The stability correction, performed to reduce the dependence on stratification for CEN and CHN, was well performed for stabilities higher than 0.15. The stability is represented by a relationship between the height and the Obukhov-length (z/L).</p><p>Validity of the non-dimensional profile functions for temperature and wind showed that, for smaller stabilities, these functions gave higher values than the corresponding functions recommended by Högström (1996). The profile funtions for temperature was shown to have a larger scatter while the profile functions for wind was less scattered and deviated more from the functions given by Högström</p> / <p>Kunskap om turbulenta flöden i det marina gränsskiktet är viktigt för att förstå växelverkan mellan atmosfär och hav. Med bättre kunskap kan förbättringar i bestämningen av utbyteskoefficienterna för latent och sensibelt värme erhållas. Det medför att modeller kan prognostisera väder och framtida klimat med högre noggrannhet.</p><p>Utbyteskoefficienterna för latent och sensibelt värme har för stabil skiktning olika värden i litteraturen. Detta gör det nödvändigt att undersöka de processer som påverkar utbytet av vattenånga och värme mellan luft och hav för att kunna bestämma dessa värden. Data som har använts i den här studien insamlades mellan år 2005 och 2007 från en boj och ett torn vid mätplatsen Östergarnsholm i Baltiska havet. För det flesta situationer, när vinden blåser från syd-ost, representerar mätplatsen ett förhållande likvärdigt det över öppet hav. De neutrala utbyteskoefficienterna, CEN och CHN, och de dimensionslösa profilfunktionera för temperatur och vind, och , har beräknats för att studera beroendet av stabilitet samt andra relevanta parametrar.</p><p>Beräkningarna visade att CEN ökade något med vindhastighet och hamnade på ett medelvärde av ungefär 1.45×10-3. De högsta värdena på CEN observerades vid nära neutrala förhållanden och låga vågåldrar. CHN uppmättes till att ha ett medelvärde på ungefär 0.77×10-3 och uppvisade inget beroende med vindhastighet eller vågålder. Inget märkbart beroende med vind- eller vågriktning kunde visas för CEN eller CHN i sektorn 80-220°. Stabilitetskorrektionen, utförd för att reducera beroendet av atmosfärens skiktning för CEN och CHN, var bra för stabiliteter högre än 0.15. Stabiliteten representeras av förhållandet mellan höjden och Obukhov-längden (z/L).</p><p>Utvärdering av de dimensionslösa funktionerna för temperatur och vind visade att dessa funktioner, för små stabiliteter, gav högre värden än motsvarande funktioner som rekommenderas av Högström (1996). Värdena på profilfunktionerna för temperatur hade större spridning än värdena på profilfunktionerna för vind och avvek mer från funktionerna givna av Högström.</p>

<p>Oceans cover about 70% of the earth’s surface. They are the largest source of the atmospheric water vapour and act as enormous heat reservoirs. Thus in order to predict the future weather and climate it is of great importance to understand the processes governing the exchange of water vapour and heat between the ocean and atmosphere. This exchange is to a large extent mediated by turbulent eddies. Current numerical climate and weather forecast models are unable to resolve the turbulence, which means that the turbulent exchange needs to be simplified by using parameterizations. </p><p>Tower based measurements at the Östergarnsholm Island in the Baltic Sea have been used to study the air-sea turbulent exchange of latent and sensible heat and the heat flux parameterizations. Although the measurements are made at an island, data obtained at this site is shown to represent open ocean conditions during most situations for winds coming from the east-south sector. It is found that during conditions with small air-sea temperature differences and wind speeds above 10 m s^-1, the structure of the turbulence is re-organized. Drier and colder air from aloft is transported to the surface by detached eddies, which considerably enhance the turbulent heat fluxes. The fluxes where observed to be much larger than predicted by current state-of-the-art parameterizations. The turbulence regime during these conditions is termed the Unstable Very Close to Neutral Regime, the UVCN-regime.</p><p>The global increase of the latent and sensible heat fluxes due to the UVCN-regime is calculated to 2.4 W m^-2 and 0.8 W m^-2 respectively. This is comparable to the current increase of the radiative forcing due to anthropogenic emissions of greenhouse gases, reported in Intergovernmental Panel on Climate Change fourth assessment report (IPCC AR4). Thus the UVCN-effect could have a significant influence when predicting the future weather and climate.</p>

Oceans cover about 70% of the earth’s surface. They are the largest source of the atmospheric water vapour and act as enormous heat reservoirs. Thus in order to predict the future weather and climate it is of great importance to understand the processes governing the exchange of water vapour and heat between the ocean and atmosphere. This exchange is to a large extent mediated by turbulent eddies. Current numerical climate and weather forecast models are unable to resolve the turbulence, which means that the turbulent exchange needs to be simplified by using parameterizations. Tower based measurements at the Östergarnsholm Island in the Baltic Sea have been used to study the air-sea turbulent exchange of latent and sensible heat and the heat flux parameterizations. Although the measurements are made at an island, data obtained at this site is shown to represent open ocean conditions during most situations for winds coming from the east-south sector. It is found that during conditions with small air-sea temperature differences and wind speeds above 10 m s-1, the structure of the turbulence is re-organized. Drier and colder air from aloft is transported to the surface by detached eddies, which considerably enhance the turbulent heat fluxes. The fluxes where observed to be much larger than predicted by current state-of-the-art parameterizations. The turbulence regime during these conditions is termed the Unstable Very Close to Neutral Regime, the UVCN-regime. The global increase of the latent and sensible heat fluxes due to the UVCN-regime is calculated to 2.4 W m-2 and 0.8 W m-2 respectively. This is comparable to the current increase of the radiative forcing due to anthropogenic emissions of greenhouse gases, reported in Intergovernmental Panel on Climate Change fourth assessment report (IPCC AR4). Thus the UVCN-effect could have a significant influence when predicting the future weather and climate.

Knowledge of the turbulent fluxes at the sea surface is important for understanding the interaction between atmosphere and ocean. With better knowledge, improvements in the estimation of the heat exchange coefficients can be made and hence models are able to predict the weather and future climate with higher accuracy. The exchange coefficients of latent and sensible heat during stable stratification vary in the literature. Therefore it is necessary to investigate the processes influencing the air-sea exchange of water vapour and heat in order to estimate these values. With measurements from a tower and a directional waverider buoy at the site Östergarnsholm in the Baltic Sea, data used in this study have been sampled from the years 2005-2007. This site represents open-ocean conditions during most situations when the wind comes from the south-east sector. The neutral exchange coefficients, CEN and CHN, have been calculated along with the non-dimensional profile functions for temperature and wind to study the dependence of stability and other parameters of relevance. It was found that CEN increased slightly with wind speed and reached a mean value of approximately 1.45×10-3. The highest values of CEN were observed during near neutral conditions and low wave ages. CHN attained a mean value of approximately 0.77×10-3 and did not show any relation to wind speed or to wave age. No significant dependence with wind or wave direction could be shown for either CEN or CHN in the sector 80-220°. The stability correction, performed to reduce the dependence on stratification for CEN and CHN, was well performed for stabilities higher than 0.15. The stability is represented by a relationship between the height and the Obukhov-length (z/L). Validity of the non-dimensional profile functions for temperature and wind showed that, for smaller stabilities, these functions gave higher values than the corresponding functions recommended by Högström (1996). The profile funtions for temperature was shown to have a larger scatter while the profile functions for wind was less scattered and deviated more from the functions given by Högström / Kunskap om turbulenta flöden i det marina gränsskiktet är viktigt för att förstå växelverkan mellan atmosfär och hav. Med bättre kunskap kan förbättringar i bestämningen av utbyteskoefficienterna för latent och sensibelt värme erhållas. Det medför att modeller kan prognostisera väder och framtida klimat med högre noggrannhet. Utbyteskoefficienterna för latent och sensibelt värme har för stabil skiktning olika värden i litteraturen. Detta gör det nödvändigt att undersöka de processer som påverkar utbytet av vattenånga och värme mellan luft och hav för att kunna bestämma dessa värden. Data som har använts i den här studien insamlades mellan år 2005 och 2007 från en boj och ett torn vid mätplatsen Östergarnsholm i Baltiska havet. För det flesta situationer, när vinden blåser från syd-ost, representerar mätplatsen ett förhållande likvärdigt det över öppet hav. De neutrala utbyteskoefficienterna, CEN och CHN, och de dimensionslösa profilfunktionera för temperatur och vind, och , har beräknats för att studera beroendet av stabilitet samt andra relevanta parametrar. Beräkningarna visade att CEN ökade något med vindhastighet och hamnade på ett medelvärde av ungefär 1.45×10-3. De högsta värdena på CEN observerades vid nära neutrala förhållanden och låga vågåldrar. CHN uppmättes till att ha ett medelvärde på ungefär 0.77×10-3 och uppvisade inget beroende med vindhastighet eller vågålder. Inget märkbart beroende med vind- eller vågriktning kunde visas för CEN eller CHN i sektorn 80-220°. Stabilitetskorrektionen, utförd för att reducera beroendet av atmosfärens skiktning för CEN och CHN, var bra för stabiliteter högre än 0.15. Stabiliteten representeras av förhållandet mellan höjden och Obukhov-längden (z/L). Utvärdering av de dimensionslösa funktionerna för temperatur och vind visade att dessa funktioner, för små stabiliteter, gav högre värden än motsvarande funktioner som rekommenderas av Högström (1996). Värdena på profilfunktionerna för temperatur hade större spridning än värdena på profilfunktionerna för vind och avvek mer från funktionerna givna av Högström.