The growing demand for the development of efficient miniature cooling systems has led to stimulating numerous investigations on two-phase flow boiling in small to microscale tubes. Because of the variation in properties of synthetic cooling fluids, this causes an inaccuracy of existing flow boiling prediction models or correlations in the literature to interpolate or extrapolate the two-phase flow boiling heat transfer and pressure drop. The purpose of this investigation was to study experimentally the parametric aspects of flow boiling characteristics inside vertical stainless-steel tubes with four different internal diameters (1.1, 2.01, 2.88 and 4.26 mm). The R245fa (1,1,1,3,3-pentafluoropropane, HFC-245fa) was used as working fluid. The experiments were carried out under a system pressure range of 185 - 310 kPa (which correspond to a saturation temperature range of 31 - 46 °C), mass flux range of 200 - 500 kg/m²s, heat flux range of 3 - 188.5 kW/m², vapour quality up to the onset of dryout and 5 K inlet subcooling. Flow pattern visualisations, two-phase pressure drops and saturated flow boiling heat transfer coefficients were presented. The experimental data of R134a employed for comparison is acquired from the previous studies of Huo et al. (2007), Shiferaw et al. (2011) and Mahmoud et al. (2014a). These studies were carried out in the same experimental facility and under the similar operating conditions. The Two-phase flow regimes inside four tubes were visualised in a borosilicate glass tube located at the heated section outlet to capture the dominant flow patterns which assist to elucidate the heat transfer results. The flow boiling visualisation was recorded by a high-speed camera with experiments of increasing and decreasing heat flux. The four observed flow regimes are identified as bubbly flow, slug flow, churn flow and annular flow. In increasing heat flux experiments, the churn and annular flows were only the dominant patterns in all four tubes. The slug flow was often discerned at lower mass flux except for the tube of 1.1 mm where it was not observed at all. This is contrary to decreasing heat flux experiments where all flow patterns including the bubble flow were observed in all the tubes. This shows a strong impact of hysteresis, which is a result of nucleation sites remained active as the heat flux is reduced. The flow patterns and transition boundaries for R245fa are affected by mass flux, system pressure, and tube diameter. The vapour quality corresponding to flow pattern transition boundary tends to decrease with increasing mass flux and tends to increase with increasing system pressure and decreasing tube diameter. Except for the bubbly-slug boundary, its vapour quality decreases with decreasing tube diameter. The experimental flow pattern maps of R245fa were fairly predicted with the predictive models developed for mini- and micro-channels by Tibiriçá et al. (2017). The two-phase pressure drop of R245fa is affected by mass flux, heat flux, system pressure, tube diameter and surface topography. The two-phase pressure drop increases with increasing mass flux and heat flux (vapour quality) and decreases with increasing system pressure and tube diameter. The two-phase pressure drop of the coated tube is higher than that of the uncoated tube. This is attributed to the coated tube having a higher surface roughness compared to the uncoated tube. The comparison between R245fa and R134a shows that the measured two-phase pressure drop of R245fa is dramatically higher than that of R134a. This arises from the difference in physical properties of the two fluids. The experimental data of two-phase pressure drop for 4.26 mm tube were reasonably predicted by Müller-Steinhagen and Heck (1986) correlation. Further, the experimental data of 2.88 mm and 2.01 mm tubes were well predicted by Chisholm (1973a), and Kim and Mudawar (2013), respectively. The experimental data of 1.1 mm tube were not well predicted by any of the selected predictive methods. The local heat transfer coefficient of all tubes increases with increasing heat flux for low and intermediate vapour qualities. After this vapour qualities, the heat flux effect diminishes. Then, the local heat transfer coefficient increased slightly with vapour quality, especially for higher heat flux near the outlet of the tube. However, the dryout inception in the 1.1 mm tube occurs after the intermediate vapour quality value and expands along the high vapour quality region. The behaviour of the local heat transfer coefficients of 1.1 and 2.88 mm tube is slightly dependent on the mass flux and vapour quality. Contrarily, there is insignificant effect of mass flux along 2.01 and 4.26 mm tube. This gives an indication of the contribution of nucleate boiling in the heat transfer process at lower and medium heat fluxes and nucleate boiling plus convective evaporation at higher heat fluxes near the tube outlet. Further, the local heat transfer coefficient increases as the system pressure increases. The tube diameter has a strong influence on the enhancement of local heat transfer coefficient. The enhancement in average heat transfer coefficient approaches 83% when the tube diameter is reduced from 4.26 to 1.1 mm. The trend of the local heat transfer coefficient of R134a was almost similar to that of R245fa with the exception of local dryout. The average heat transfer coefficient of R134a is about 106-151% larger than that of R245fa for the operational range studied. The dominant heat transfer mechanism is also represented by nucleate boiling for both fluids, particularly for 4.26 mm tube tested in this study. Also, the average heat transfer coefficient was enhanced by 33% when the inner tube surface coated with a copper coating. Finally, the correlation of Fang et al. (2017) predicted all experimental data for the four tubes with fair and similar accuracy.

Submitted by Renan Luis Fragelli null (renan.fragelli@gmail.com) on 2017-03-28T15:54:09Z No. of bitstreams: 1 Dissertação de Mestrado - Renan Fragelli.pdf: 5490064 bytes, checksum: 80c3b38563331cc9ef7e88ff192c5c8b (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-03-29T20:46:29Z (GMT) No. of bitstreams: 1 fragelli_rl_me_bauru.pdf: 5490064 bytes, checksum: 80c3b38563331cc9ef7e88ff192c5c8b (MD5) / Made available in DSpace on 2017-03-29T20:46:29Z (GMT). No. of bitstreams: 1 fragelli_rl_me_bauru.pdf: 5490064 bytes, checksum: 80c3b38563331cc9ef7e88ff192c5c8b (MD5) Previous issue date: 2017-03-16 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho surgiu a partir da necessidade de produzir avanços em projeto que trata do desenvolvimento de um porta-ferramentas refrigerado internamente através de um fluido em mudança de fase e, na tentativa de minimizar a alta temperatura na ferramenta de corte através desse sistema de circulação. A utilização de nanofluidos surgiu como uma alternativa para a otimização da transferência térmica entre fluido e ferramenta de corte. A pesquisa consiste em avaliar a influência da adição de nanopartículas de prata numa solução de etilenoglicol e água deionizada, e também, da adição de nanopartículas de hematita (Fe2O3) no fluido refrigerante R141b. Em ambos os casos, as nanopartículas possuíam formato esférico, diâmetro médio de 30nm e foram avaliadas em concentrações. Além disso, as duas soluções foram submetidas a um campo elétrico na região de transferência térmica para analisar a influência do efeito eletrohidrodinâmico e, por fim, considerando as propriedades magnéticas da hematita, este nanofluido foi testado sob influência de um campo magnético. Os testes mostraram que as nanopartículas realmente influenciaram as propriedades dos fluidos e, por consequência, a quantidade de calor transferido. O nanofluido Ag/ETG+H2O(l) (0,023 vol%) resultou num incremento de 11% no valor do coeficiente de transferência térmica convectivo (h) quando sujeito ao campo elétrico. Para o caso do nanofluido Fe2O3/R141b, o valor de h aumentou em 30,3%, porém, quando sob efeito do campo magnético ou elétrico, o coeficiente foi prejudicado, resultando num valor menor que o do controle. Ao final, tem-se a proposta de um possível modelo desse porta-ferramentas. / This work arose from the need to produce advances in design development of an internally cooled toolholder through a phase change fluid. In order to minimize the high temperature in the cutting tool by this circulation system, using nanofluids emerged as an alternative to optimize heat transfer between the fluid and the cutting tool. The research consists in evaluate the influence of addition of silver nanoparticles in an ethylene glycol and deionized water solution, and also the addition of hematite nanoparticles (Fe2O3) in the refrigerant R141b. In both cases, nanoparticles had spherical shape, diameter of 30nm, and they were evaluated in different concentrations. Moreover, both nanofluids were subjected to an electric field in the heat transfer region to evaluate the influence of electrohydrodynamic effect and, finally, considering the magnetic properties of hematite, this nanofluid was tested under the influence of a magnetic field. The tests have shown that the nanoparticles really influence the properties of the fluids and, therefore, the amount of heat transferred. The nanofluid Ag/ETG+H2O(l) also presented a positive influence of the electric field, further enhancing the value of the convective heat transfer coefficient (h) in 11% (0,039 vol%). In the case of Fe2O3/R141b nanofluid, the h value increased 30.3%. However, when the nanofluid was under magnetic or electric effect, the value of h was deteriorated, resulting in a lesser value than the control. As conclusion, a new toolholder prototype is presented.

Os óleos essenciais cítricos possuem uma ampla variedade de aplicações em diversos ramos das indústrias químicas, farmacêuticas, de alimentos, entre outras. Na indústria de cosméticos, mais precisamente no ramo de perfumaria, os ativos naturais cítricos (provenientes dos óleos de bergamota, limão, lima, mandarina, laranja, etc) são empregados nas formulações de colônias, cremes hidratantes e loções. Além disso, estes compostos são largamente utilizados como agentes aromatizantes nas indústrias alimentícias e farmacêuticas e empregados como matéria-prima para as indústrias de aromas. Com o objetivo de melhorar a qualidade dos óleos essenciais e sua capacidade aromatizante, alguns processos têm sido desenvolvidos para enriquecer a mistura com compostos oxigenados, os quais são reportados como os principais responsáveis pelo aroma característico da fruta. Tal processo é comumente conhecido como desterpenação e consiste na concentração destes compostos pela retirada de hidrocarbonetos terpênicos do óleo e pode ser realizado por meio da extração líquida ou extração por solvente. Neste contexto, esta dissertação de mestrado teve como finalidade estudar da viabilidade técnica do processo de desterpenação de óleo essencial cítrico modelo composto por limoneno e linalol. Os experimentos foram conduzidos em coluna de discos rotativos perfurados (PRDC) sob condição de temperatura controlada e pressão ambiente local. O equipamento operou de modo contínuo e contracorrente, utilizado como solventes soluções de etanol com teores de água de 30 e 40% (em massa), velocidade de rotação dos discos de 150, 200 e 250 rpm e razão entre a vazão mássica de solvente e alimentação de 0,5; 1,25; 2,5 e 3,0. Avaliou-se, também, o comportamento da densidade e viscosidade das fases extrato e rafinado oriundas da coluna de extração. Através deste estudo foi possível verificar que a tecnologia de desterpenação de óleos essenciais por meio da extração líquido-líquido é viável podendo ser aplicada à processos contínuos utilizando equipamento PRDC, por exemplo, sendo possível a obtenção de frações enriquecidas do composto oxigenado (linalol). / Citrus essential oils are used in a wide variety of applications in various branches of the chemical, pharmaceutical, food and other industries. In the cosmetics industry, specifically in the field of perfumery, natural citrus assets (from the essential oils of bergamot, lemon, lime, mandarin, orange, etc.) are used in the formulations of colonies, moisturizing creams and lotions. Furthermore, these compounds are widely used as flavoring agents in food and pharmaceutical industries and as raw material for the flavor industry. With the aim to improve the quality of essential oils and its flavoring ability, some processes have been developed to enrich the mixture with oxygenated compounds, which are reported as the main responsible for the characteristic aroma of the fruit. Such process is commonly known as deterpenation, and consists in concentration of these compounds by the removal of terpene compounds from the essencial oil and can be performed by liquid or solvent extraction. In this context, the purpose of this dissertation of master\'s degree was to carry out a study of the technical feasibility of deterpenation process of a citrus essential oil model composed by a mixture of limonene and linalool. The experiments of deterpenation were conducted in a perforated rotating discs contactor (PRDC) under controlled conditions of temperature and local environment al pressure. The equipment was operated in continuously and countercurrently mode, using as solvents ethanol solutions with 30 and 40% of water contents (by mass), rotation of discs speed of 150, 200 and 250 rpm and the mass flow rate of the solvent and feed ratio of 0.5, 1.25, 2.5 and 3.0. The behavior of the density and viscosity of the extract and raffinate phases from the extraction column was also evaluated. It was found that the deterpenation of essential oils by liquid-liquid extraction technology is feasible and can be applied to continuous processes using PRDC column extraction type, for instance, being possible to obtain enriched fractions of oxygenated compounds (linalool).

Experimental data on SuperCritical-Water (SCW) cooled bundles are very limited. Major problems with performing such experiments are: 1) small number of operating SCW experimental setups and 2) difficulties in testing and experimental costs at very high pressures, temperatures and heat fluxes. However, SuperCritical Water-cooled nuclear Reactor (SCWRs) designs cannot be finalized without such data. Therefore, as a preliminary approach experiments in SCW-cooled bare tubes and in bundles cooled with SC modeling fluids can be used. One of the SC modeling fluids typically used is Freon-12 (R-12) where the critical pressure is 4.136 MPa and the critical temperature is 111.97ºC. These conditions correspond to a critical pressure of 22.064 MPa and critical temperature of 373.95ºC in water. A set of experimental data obtained in a Freon-12 cooled vertical bare bundle at the Institute of Physics and Power Engineering (IPPE, Obninsk, Russia) was analyzed. This set consisted of 20 cases of a vertically oriented 7-element bundle installed in a hexagonal flow channel. To secure the bundle in the flow channel 3 thin spacers were used. The dataset was obtained at equivalent parameters of the proposed SCWR concepts. Data was collected at pressures of about 4.65 MPa for several different combinations of wall and bulk-fluid temperatures that were below, at, or above the pseudocritical temperature. Heat fluxes ranged from 9 kW/m2 to 120 kW/m2 and mass fluxes ranged from 440 kg/m2s to 1320 kg/m2s. Also inlet temperatures ranged from 70ºC – 120ºC. The test section consisted of fuel elements that were 9.5 mm in diameter with the total heated length of 1 m. Bulk-fluid and wall temperature profiles were recorded using a combination of 8 different thermocouples.The data was analyzed with respect to its temperature profile and heat transfer coefficient along the heated length of the test section. In a previous study it was confirmed that there is the existence of three distinct regimes for forced convention with supercritical fluids. (1) Normal heat transfer; (2) Deteriorated heat transfer, characterized by higher than expected temperatures; and (3) Improved heat transfer, characterized by lower than expected temperatures. All three regions were observed for the 7 rod bundle experiments. This work compares the experimental data to predictions based upon current 1-D correlations for heat transfer in supercritical fluids. Results show that no current 1-D correlation was able to accurately predict heat transfer coefficients within ±50%. A parametric analysis of the data was also completed to determine if continuity in the experiment was present. Results of this study show that two distinct regions are present in the data. For cases with a mass flux below 1200 kg/m2s wall temperature profiles appear to be normal while in cases with mass flux above 1200 kg/m2s temperature given by the wall thermocouples were higher than normal. This phenomenon occurred regardless of heat flux-to-mass flux ratios. / UOIT

Recombinant Pichia pastoris is one of the important methylotropic yeast due to its robustness and ability to produce hormones like human chorionic gonadotropin (hCG), luteinizing hormone (LH) extracellularly. High growth on glycerol and strong protein expression on methanol by insertion of alcohol oxidase (AOX) promoter demand the fermentation to be a multistage operation. Methylotropic pathway demands more oxygen as methanol has to be converted to formaldehyde with half mole of oxygen. Moreover as fermentation progresses cell density in the reactor also increases. In case of Pichia pastoris fermentation cell density usually reaches very high (above 100 gm/lit) at the end of fermentation. Both these contribute in the increased oxygen demand in the fermentation and oxygen transfer turns out to be a limiting step. The present study focuses on the oxygen transfer process and its improvement in the fermentation. Oxygen transfer in bioreactor is a multistep process and involves different kinetic as well as mass transfer steps. In case of fermentation especially at high cell densities, oxygen transfer from bubbles to the broth becomes limiting step. The interface transport is governed by many physical as well as kinetic parameters. It is essential to screen these parameters from the whole set to identify the key parameters. Sensitivity analysis is carried out by using Metabolic Control Analysis (MCA) to quantify the effects of different parameters. It is found that bubble size and oxygen partial pressure are two such key parameters which can be manipulated. Use of pure oxygen to increase partial pressure and thereby solubility of oxygen in broth is a common approach. This work focuses on bubble size manipulation to increase the oxygen transfer rates.The idea behind this work is on to generate micron sized bubbles and utilize them effectively in the fermentation. There are many techniques reported to generate microbubble dispersions. In this work ’Spinning Disc microbubble Generator’ is fabricated to generate microbubbles. A flat disc surrounded by baffles with 5 mm gap in between, when subjected to 5000 rpm generates microbubbles. Some modifications are done to the set up to achieve desired properties of the bubbles. The bubbles generated fall in the range of 30-300 micron with mean size of about 60 micron. Use of Tween-20 surfactant stabilize the bubbles and hence offer a good resistance to coalescence and breakage. The liquid fraction in the bubbles can be as high as 40%. Contineous addition of this dispersion unnecessarily can dilute the fermentation broth. To overcome this volume constrain, a recirculation system is designed. Microbubble dispersion is added contineously to the reactor and equivalent fermentation broth is pumped back to the microbubble generator to achieve steady state to the liquid volume in both the vessels. Mass transfer studies with microbubbles show the potential of microbubble dispersion (MBD) to enhance mass transfer significantly. Decrease in volumetric mass transfer coefficient (KLa) due to surfactant is overcompensated by the increase in the interfacial area and net effect is, potential enhancement in KLa. The enhance- ment factor, that is, ratio of mass transfer coefficient with MBD to mass transfer coefficient with conventional sparging, is obtained to be about 4 to 5. Prior to utilization of bubbles in the recirculation system, cells are checked for the shear sensitiveness. Negligible lysis losses and almost no effect on growth patterns in shake flask culture confirm that the cells used are mechanically stable at operating conditions. Better growth patterns in shake flask are observed when microbubbles are pumped for predetermined duration in the broth. It shows possible use of MBD as oxygen carriers. Glycerol batch phase with MBD and conventional sparging is studied at different initial cell densities. Conventional sparging fails to grow the cells and Dissolved Oxygen (DO) levels close to zero suggest high oxygen demands which can not be sustained by conventional sparging. The same batch is run using MBD. Reasonably good growth patterns are observed. DO levels are well above 70% for most of the time during operation. High oxygen demand which can not be sustained by conventional sparging alone can be sustained by MBD. In this way in high den- sity cultures utilization of MBD can be a good alternative to fulfill required oxygen demand in fermentation.

Phase-change heat transfer is an important process used in many engineering thermal designs. Boiling is an important phase change phenomena as it is a common heat transfer process in many thermal systems. Phase change processes are critical to thermodynamic cycles as most closed loop systems have an evaporator, in which the phase change process occurs. There are many applications/processes in which engineers employ the advantages of boiling heat transfer, as they seek to improve heat transfer performance. Recent research efforts have experimentally shown that nanofluids can have significantly better heat transfer properties than those of the pure base fluids, such as water. The objective of this study is to improve the boiling curve of de-ionized water by adding aluminum oxide nanopthesiss in 0.1%, 0.2%, 0.3% and 0.4% wt concentrations in a sub-cooled pool boiling apparatus. Enhancement to the boiling curve can be quantified in two ways: (i) the similar heat fluxes of de-ionized water at smaller excess temperature, indicating similar quantity of heat removal at lower temperatures and (ii) greater heat fluxes than de-ionized water at similar excess temperatures indicating better heat transfer at similar excess temperatures. In the same fashion, the secondary objective is to increase the convective heat transfer coefficient due to boiling by adding different concentrations of aluminum oxide nanopthesiss.

No description available.

This thesis investigates the cooling behaviour of polymers during the microinjection moulding process. The work included bespoke experimental mould design and manufacturing, material characterisation, infra-red temperature measurements, cooling analysis and cooling prediction using commercial simulation software. To measure surface temperature of the polymers, compounding of polypropylene and polystyrene with carbon black masterbatch was performed to make materials opaque for the IR camera. The effects of addition of carbon black masterbatch were analysed using differential scanning calorimetry and Fourier transform infrared spectroscopy. Sapphire windows formed part of the mould wall and allowed thermal measurements using an IR camera. They were laser machined on their inside surfaces to generate a range of finishes and structures. Their topographies were analysed using laser confocal microscope. The surface energy of sapphire windows was measured and compared to typical mould steel, employing a contact angle measurement technique and calculated using Owens-Wendt theory. A heating chamber was designed and manufactured to study spreading of polymer melts on sapphire and steel substrates. A design of experiments approach was taken to investigate the influence of surface finish and the main processing parameters on polymer cooling during microinjection moulding. Cooling curves were obtained over an area of 1.92 by 1.92 mm of the sapphire window. These experiments were conducted on the Battenfeld Microsystem 50 microinjection moulding machine. A simulation study of polymer cooling during the microinjection moulding process was performed using Moldflow software. Particular interest was paid to the effect of the values of the interfacial heat transfer coefficient (HTC) on the simulated cooling predictions. Predicted temperature curves were compared to experimentally obtained temperature distributions, to obtain HTC values valid for the material and processing parameters.

Este trabalho trata de um estudo experimental da transferência de calor e de massa de um condensador evaporativo, bem como, da relação existente entre as grandezas envolvidas durante a sua operação. Para o desenvolvimento da pesquisa foi construído um condensador evaporativo de pequeno porte com dimensões proporcionais a condensadores comercialmente fabricados no Brasil para operar com R-22 como fluido refrigerante. Este condensador tem 35 colunas e 12 fileiras de tubos de cobre de 6,35 mm de externo e opera junto a uma instalação que proporciona o escoamento de R-22 por termossifao. O distribuidor de água também foi construído em cobre e o eliminador de gotas em alumínio, assim como a estrutura do condensador. As laterais e a bandeja de recolhimento de água foram construídas em vidro para permitir a visualização do escoamento da água que e aspergida sobre os tubos. A fim de variar as condições operacionais, este condensador foi acoplado a um ventilador centrifugo acionado por um conversor de freqüência e a um circuito que permitiu a variação da vazão de água aspergida sobre os tubos. Dos ensaios resultaram 79 amostras de medição, que serviram para verificar a relação existente entre grandezas, bem como avaliar os coeficientes de transferência de calor e massa. Foram determinados os coeficientes de transferência de calor médio e local para o R-22. Alem disso, foram verificadas as regiões onde ocorrem o dessuperaquecimento, a mudança de fase e o subresfriamento do fluido refrigerante, e foram confrontados os coeficientes globais de transferência de calor obtidos a partir dos dados experimentais com aqueles obtidos por correlações para as regiões de condensação e subresfriamento. Destas investigações, resultou uma correlação para o coeficiente global de transferência de calor que visa determinar esta grandeza através das condições operacionais e das características geométricas do condensador. O Maximo desvio encontrado entre os valores provenientes dos dados experimentais e aqueles calculados pela correlação foi inferior a 10%. / This work presents an experimental heat and mass transfer study of an evaporative condenser, as well as, the relationship between measured quantities obtained during its operation. A small scale evaporative condenser was built in agreement to the real size equipment geometric similarity. The small scale condenser has a bundle of 210 copper tubes, with the outer diameter equal to ¼ inch, which were arranged in 35 columns and 6 rows and operating connected to the thermosifon facility that promote R-22 flow. The spray water distributor is also built on copper and the drift eliminator on aluminum, as well as the evaporative condenser structure. This condenser bounds were constructed as a glass enclosure to allow for the spray water flow visualization. To evaluate the operational conditions, the equipment was attached to a centrifugal fan controlled by a frequency inverter and a spray water circuit which allows for water quantity changing. From the carried out tests, 79 measuring samples were obtained and used to verify the quantities relationship, as well as, to evaluate the heat and mass transfer coefficients For the R-22 were determined the local and average heat transfer coefficients. Furthermore, the dessuperheating, condensation and subcooling regions were verified and compared both, the experimental overall heat transfer coefficient and those calculated by correlations at condensation and subcooling zones. From these investigations a correlation for the overall heat transfer coefficient is proposed. Its application allows determining the coefficient using the operational conditions and the geometric condenser features. The higher deviation found between the experimental data and the presented correlation is lower to 10%.

Este trabalho trata de um estudo experimental da transferência de calor e de massa de um condensador evaporativo, bem como, da relação existente entre as grandezas envolvidas durante a sua operação. Para o desenvolvimento da pesquisa foi construído um condensador evaporativo de pequeno porte com dimensões proporcionais a condensadores comercialmente fabricados no Brasil para operar com R-22 como fluido refrigerante. Este condensador tem 35 colunas e 12 fileiras de tubos de cobre de 6,35 mm de externo e opera junto a uma instalação que proporciona o escoamento de R-22 por termossifao. O distribuidor de água também foi construído em cobre e o eliminador de gotas em alumínio, assim como a estrutura do condensador. As laterais e a bandeja de recolhimento de água foram construídas em vidro para permitir a visualização do escoamento da água que e aspergida sobre os tubos. A fim de variar as condições operacionais, este condensador foi acoplado a um ventilador centrifugo acionado por um conversor de freqüência e a um circuito que permitiu a variação da vazão de água aspergida sobre os tubos. Dos ensaios resultaram 79 amostras de medição, que serviram para verificar a relação existente entre grandezas, bem como avaliar os coeficientes de transferência de calor e massa. Foram determinados os coeficientes de transferência de calor médio e local para o R-22. Alem disso, foram verificadas as regiões onde ocorrem o dessuperaquecimento, a mudança de fase e o subresfriamento do fluido refrigerante, e foram confrontados os coeficientes globais de transferência de calor obtidos a partir dos dados experimentais com aqueles obtidos por correlações para as regiões de condensação e subresfriamento. Destas investigações, resultou uma correlação para o coeficiente global de transferência de calor que visa determinar esta grandeza através das condições operacionais e das características geométricas do condensador. O Maximo desvio encontrado entre os valores provenientes dos dados experimentais e aqueles calculados pela correlação foi inferior a 10%. / This work presents an experimental heat and mass transfer study of an evaporative condenser, as well as, the relationship between measured quantities obtained during its operation. A small scale evaporative condenser was built in agreement to the real size equipment geometric similarity. The small scale condenser has a bundle of 210 copper tubes, with the outer diameter equal to ¼ inch, which were arranged in 35 columns and 6 rows and operating connected to the thermosifon facility that promote R-22 flow. The spray water distributor is also built on copper and the drift eliminator on aluminum, as well as the evaporative condenser structure. This condenser bounds were constructed as a glass enclosure to allow for the spray water flow visualization. To evaluate the operational conditions, the equipment was attached to a centrifugal fan controlled by a frequency inverter and a spray water circuit which allows for water quantity changing. From the carried out tests, 79 measuring samples were obtained and used to verify the quantities relationship, as well as, to evaluate the heat and mass transfer coefficients For the R-22 were determined the local and average heat transfer coefficients. Furthermore, the dessuperheating, condensation and subcooling regions were verified and compared both, the experimental overall heat transfer coefficient and those calculated by correlations at condensation and subcooling zones. From these investigations a correlation for the overall heat transfer coefficient is proposed. Its application allows determining the coefficient using the operational conditions and the geometric condenser features. The higher deviation found between the experimental data and the presented correlation is lower to 10%.