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Regulace teploty mikrovlnného reaktoru. / Temperature controller of microwave reactorPokorný, Ondřej January 2008 (has links)
Simple low-cost temperature feedback control loop was created, using personal computer as control and data acquisition element. It controlled the temperature inside mircowave pressure reactor. Medium in reactor tank (volume about 600 ml) was calorified by 1,8 kW magnetron, which power was driven by PSD controller. The PC- process interface was made by USB data acquisition modul UD128A8D. The utility program was written. It implemented PSD controller and data acquisition function. Furhtermore it implemented interface which enabled user to set the technological curve (time-temperature relation). The protocol of experiment was automatically stored to Micosoft Excel file before the program’s termination.
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Experimental investigations and finite element analyses of interface heat partition in a friction brake system. New modelling paradigm for describing friction brake systems to support studies of interface temperature, contact pressure, heat flux distribution and heat partition ratio by experiment and FE simulationQui, Le January 2018 (has links)
Operating temperature range is one of the primary design considerations for
developing effective disc brake system performance. Very high braking
temperatures can introduce effects detrimental to performance such as
brake fade, premature wear, brake fluid vaporization, bearing failure, thermal
cracks, and thermally-excited vibration [2].
This project is concerned with investigating deficiencies and proposing
improvements in brake system Finite Element (FE) models in order to
provide high quality descriptions of thermal behaviour during braking events.
The work focuses on brake disc/pad models and the degree of rotational
freedom allowed for the pad. Conventional models [10] allow no motion/or
free motion of the pad. The present work investigates the effect on disc/pad
interface temperature and pressure distributions of limited relaxations of this
rotational restriction. Models are proposed, developed and validated that
facilitate different rotational degrees of freedom (DoF) of the pad.
An important influencing factor in friction brake performance is the
development of an interface tribo-layer (ITL). It is reasonable to assume that
allowing limited rotational motion of the pad will impact the development of
the ITL (e.g. due to different friction force distributions) and hence influence
temperature. Here the ITL is modelled in the numerical simulations as a
function of its thickness distribution and thermal conductivity. Different levels
of ITL thermal conductivity are defined in this work and results show that
conductivity significantly a1qwffects interface temperature and heat partition
ratio.
The work is based around a set of test-rig experiments and FE model
developments and simulations. For the experimental work, a small-scale test
rig is used to investigate the friction induced bending moment effect on the
pad/disc temperature. Significant non-uniform wear is observed across the
friction surface of the pad, and reasons for the different wear rates are
proposed and analyzed together with their effect on surface temperature.
Following on from experiment a suite of models is developed in order to
evidence the importance of limited pad motion and ITL behaviours.
A 2D coupled temperature-displacement FE model is used to quantify the
influence of different pad rotational degrees of freedom and so provide
evidence for proposing realistic pad boundary settings for 3D models.
Normal and high interface thermal conductance is used in 2D models and
results show that the ITL thermal conductivity is an important factor
influencing the maximum temperature of contact surfaces and therefore
brake performance. The interface heat partition ratio is calculated by using
the heat flux results and it is confirmed that this value is neither constant nor
uniform across the interface surfaces.
Key conclusions from the work are (i) that ITL thermal conductivity is an
important factor influencing the interface temperature/heat flux distribution
and their maximum values, (ii) that allowed motion of the pad significantly
affects the interface pressure distribution and subsequently the temperature
distribution, (iii) that the transient heat partition in friction braking is clearly
quite different to the conventional friction-pair steady heat partition (the heat
partition ratio is not uniformly distributed along the interface) and (iv) that the
thickness of the ITL increases through braking events, reducing the heat
transfer to the disc, and so providing a possible explanation for increasing
pad temperature observed over the life time of a brake pad.
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[en] STUDIES ON WAX DEPOSIT FORMATION IN PIPELINES / [pt] ESTUDOS SOBRE A FORMAÇÃO DE DEPÓSITOS DE PARAFINA EM DUTOSJOAO CLAUDIO BASTOS LIMA 21 January 2019 (has links)
[pt] O entendimento do fenômeno de deposição de parafina em linhas submarinas de produção e transporte de petróleo é importante para a construção de modelos de previsão que auxiliem no projeto e operação destas linhas. No presente trabalho, foram realizados experimentos controlados em escala de laboratório com o objetivo de obter informações sobre alguns aspectos relevantes da deposição de parafina. Para isso, foi utilizada uma seção de testes anular, com condições de contorno bem controladas, operando com um fluido de testes com propriedades bem conhecidas, e apresentando uma distinção marcada entre a composição do solvente e aquela das parafinas. A seção de testes era equipada com uma sonda de temperatura de pequenas dimensões acoplada a um micrômetro, o que permitiu a medição de perfis de temperatura dentro do depósito para condições de escoamento. A sonda também possibilitou a obtenção da temperatura da interface depósito-líquido ao longo da formação do depósito. Os testes incluíram a variação do número de Reynolds do escoamento anular, da temperatura da parede fria, e da taxa de resfriamento da parede. Uma câmera de vídeo de alta taxa de aquisição de imagens acoplada a lentes de aproximação foi utilizada para determinar a posição da sonda de temperatura em relação à interface do depósito. Os resultados mostraram que a temperatura da interface se mantém estável em um valor intermediário entre a TIAC (Temperatura Inicial de Aparecimento de Cristais) e a TDC (Temperatura de Desaparecimento de Cristais), desde quando a deposição de inicia até quando depósito atinge sua espessura de regime permanente. A câmera de vídeo forneceu imagens originais sobre a formação dos depósitos, notadamente sobre uma região acima do depósito em formação onde cristais de parafina são carregados pelo escoamento, sem que um número significativo destes cristais depositasse ou fosse aprisionado no depósito. As imagens revelaram também que estes cristais não são oriundos de cristais arrancados do depósito em posições a montante no início do duto, mas têm origem no seio do fluido adjacente à interface do depósito. A sonda de temperatura foi também utilizada na medição da temperatura nesta região de líquido acima da interface do depósito onde, por um período de tempo, cristais de parafina escoavam. / [en] The proper understanding of the wax deposition phenomena in subsea oil pipelines is relevant to the development of more accurate models to aid in the design and operation of these lines. In the present work, laboratory-scale experiments under well-controlled conditions were conducted to study some relevant aspects of wax deposition. To this end, an annular deposition test section was employed, using a test fluid with known properties, and displaying a marked distinction between the solvent and the wax chemical components. The test section was equipped with a temperature probe of small dimensions, driven by a micrometer head. This probe allowed the measurement of temperature profiles within the wax deposit, under flowing conditions, and also the temperature of the deposit-liquid interface as the deposit was formed. The tests encompassed the variation of the annular flow Reynolds number, the cold wall temperature and the wall cooling rate. A high-frame-rate video camera coupled to magnifying lenses was used to provide images of the temperature probe and of the deposit interface. The results showed that that temperature of the interface remains stable in an intermediate value between the WAT (Wax Appearance Temperature) and the WDT (Wax Disappearance Temperature), since the first moments of the deposition until the deposit reaches its steady state configuration. The video camera captured original images on the deposit formation, especially on a region above the deposit where wax crystals are carried by the flow for a period of time. Only an insignificant number of carried crystals were observed to deposit over the immobile interface, or to be captured at the interface. The images also revealed that the carried crystals do not originate from crystals sloughed from upstream positions in the annular duct. The temperature probe
was also employed to measure the temperature of the liquid region above the deposit interface where the crystals existed for a period of time.
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Tribological investigation of electrical contactsBansal, Dinesh Gur Parshad 19 October 2009 (has links)
The temperature rise at the interface of two sliding bodies has significant bearing on the friction and wear characteristics of the bodies. The friction heat generated at the interface can be viewed as "loss of exergy" of the system, which also leads to accelerated wear in the form of oxidation, corrosion, and scuffing. This has a direct impact on the performance of the components or the machinery. If the sliding interface is also conducting electric current then the physics at the interface becomes complicated. The presence of electrical current leads to Joule heat generation at the interface along with other effects like electromotive, electroplasticity, stress relaxation and creep.
The interface of an electrical contact, either stationary or dynamic, is a complex environment as several different physical phenomena can occur simultaneously at different scales of observations. The main motivation for this work stems from the need to provide means for accurate determination or prediction of the critical contact parameters viz., temperature and contact resistance. Understanding the behavior of electrical contacts both static and dynamic under various operating conditions can provide new insights into the behavior of the interface. This dissertation covers three major topics: (1) temperature rise at the interface of sliding bodies, (2) study on static electrical contacts, and (3) study of factors influencing behavior of sliding electrical contacts under high current densities.
A model for determining the steady-state temperature distribution at the interface of two sliding bodies, with arbitrary initial temperatures and subjected to Coulomb and/or Joule heating, is developed. The model applies the technique of least squares regression to apply the condition of temperature continuity at every point in the domain. The results of the analysis are presented as a function of non-dimensional parameters of Peclet number, thermal conductivity ratio and ellipticity ratio. This model is first of its kind and enables the prediction of full temperature field. The analysis can be applied to a macro-scale contact, ignoring surface roughness, between two bodies and also to contact between two asperities. This analysis also yields an analytical expression for determining the heat partition between two bodies, if the Jaeger's hypothesis of equating average temperatures of both the bodies is being implemented.
In general for design purposes one is interested in either the maximum or the average temperature rise at the interface of two sliding bodies. Jaeger had presented simple equations, based on matching the average temperatures of both bodies, for square and band shaped contact geometries. Engineers since then have been using those equations for determining the interface temperature for circular and elliptical shaped contact geometries. Curve fit equations for determining the maximum and the average interface temperature for circular and elliptical contact with semi-ellipsoidal form of heat distribution are presented. These curve fit equations are also applicable for the case when both the bodies have dissimilar initial bulk temperatures. The equations are presented in terms of non-dimensional parameters and hence can easily be applied to any practical scenario.
The knowledge of electrical contact resistance between two bodies is important in ascertaining the Joule heat generation at the interface. The prediction of the contact resistance thus becomes important in predicting the performance of the contact or the machinery where the contact exists. The existing models for predicting ECR suffer from the drawback of ambiguity of the definition of input parameters as they depend on the sampling resolution of the measuring device. A multi-scale ECR model which decomposes the surface into its component frequencies, thus capturing the multi scale nature of rough surfaces, is developed to predict the electrical contact resistance. This model, based on the JS multi-scale contact model, overcomes the sensitivity to sampling resolution inherent in many asperity based models in the literature. The multi-scale ECR model also offers orders of magnitude of savings in computation time when compared to deterministic contact models. The model predictions are compared with the experimental observations over a wide range of loads and surface roughness of the specimens, and it is observed that the model predictions are within 50% of the experimental observations.
The effect of current cycling through static electrical contact is presented. It is observed that, the voltage drop across the contact initially increases with current until a certain critical voltage is increased. Beyond this critical point any increase in the current causes essentially no increase in steady-state contact voltage. This critical voltage is referred to as "saturation voltage." The saturation voltage for Al 6061 interface is found to be in the range of 160 - 190 mV and that for Cu 110 interface is in the range of 100 - 130 mV. The effect of load and surface roughness on voltage saturation is also demonstrated experimentally. An explanation based on the softening of the interface, due to temperature rise, is proposed rather than more widely referred hypothesis of recrystallization.
The phenomenon of voltage saturation is also demonstrated in sliding electrical contacts. The behavior of sliding interfaces of aluminum-copper (Al-Cu) and aluminum-aluminum (Al-Al) are analyzed under high current densities. Experimental results are presented that demonstrate the influence of load, speed, current and surface roughness on coefficient of friction, contact voltage, contact resistance, interface temperature and wear rate. The experimental results reveal that thermal softening of the interface is the primary reason for accelerated wear under the test conditions. The results from the experiments presents an opportunity to form constitutive equations which could be used to predict the performance of the contact based on input parameters.
The fusion of the findings of this dissertation provide methodologies along with experimental tools and findings to model, study and interpret the behavior of electrical contacts.
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Estudo da influência do material do porta-ferramenta sobre temperaturas de usinagem no torneamento / Study on the influence of toolholder material on the cutting temperatures in turning machiningKaminise, Almir Kazuo 19 December 2012 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The main objective of this work is the experimental investigation of the effect that the material
of the toolholder has on the temperature at tool-chip interface and on the surface
temperatures of the cutting tool and toolholder. The study was conducted in dry turning of
gray iron with uncoated cemented carbide inserts, using the same cutting parameters. Five
toolholders had been confectioned in materials having different thermal conductivity, these
being: copper, brass, aluminum, stainless steel and titanium alloy. The toolholders are
identical and have the constructive aspects obtained from a commercial toolholder for turning
that material. The temperature at the tool-chip interface was measured using the toolworkpiece
thermocouple method and the surface temperatures in the tools and the
toolholders, by conventional type T thermocouples. The system was modified in order to
develop an experimental procedure for the physical compensating of the secondary and
parasites thermoelectric signals (emf). Also, modifications was carried out in a conventional
tailstock for use in driving the emf signal between the workpiece and a stationary conductor,
but without significantly altering the stiffness of the system. The tailstock was electric
insulated and a mercury bearing was mounted inside it and their internal connections were
turned in reference junctions at room temperature because on otherwise it could act as
secondary junctions. The calibration of the tool-workpiece thermocouple was developed in
the same experimental apparatus using the modifications implemented in this system.
Besides the results obtained with the investigation of the effects of the toolholder material on
the surface temperatures of the tool and the tool holder and on the tool-chip interface
temperature, this research also presents contributions to the use and performance of the
tool-workpiece thermocouple method. / O objetivo principal deste trabalho é a investigação experimental do efeito que o material do
porta-ferramenta exerce sobre a temperatura na interface ferramenta/cavaco e sobre as
temperaturas superficiais da ferramenta de corte e do próprio porta-ferramenta. O estudo foi
desenvolvido com a operação de torneamento cilíndrico externo de ferro fundido cinzento, a
seco, com insertos de metal duro, em parâmetros de corte fixos. Cinco portas-ferramentas
foram confeccionados em materiais com condutividades térmicas diferentes, sendo esses:
cobre, latão, alumínio, aço inoxidável e liga de titânio. Os portas-ferramentas são
geometricamente idênticos e têm as características construtivas de um porta-ferramenta
comercial próprio ao torneamento daquele material. Mediu-se a temperatura na interface
ferramenta/cavaco usando o método do termopar ferramenta-peça e as temperaturas
superficiais na ferramenta e nos suportes, por meio de termopares convencionais do tipo T.
O sistema termopar ferramenta-peça foi modificado no sentido de se desenvolver um
procedimento experimental para a compensação física de forças eletromotrizes secundárias
e parasitas. Destaca-se a execução de modificações em uma contra ponta rotativa
convencional para o seu uso na condução do sinal da força eletromotriz entre a peça e um
condutor estacionário sem, contudo, alterar significativamente a sua rigidez na fixação da
peça. Nessas modificações, aplicou-se uma isolação elétrica permanente, implantou-se um
mancal de mercúrio no seu interior e promoveu-se mudanças nas suas conexões internas,
que poderiam agir como junções secundárias, transformando-as em junções de referência à
temperatura ambiente. A calibração do sistema termopar ferramenta-peça foi desenvolvida
sobre o próprio aparato experimental usando as modificações implantadas nesse sistema.
Os resultados obtidos no trabalho mostram que os materiais usados nos suportes
influenciam nas temperaturas superficiais da ferramenta e do porta-ferramenta, porém, que
tais materiais não tem efeito significativo sobre as temperaturas da interface
ferramenta/cavaco. Além disso, o trabalho apresenta, também, contribuições ao uso e
calibração do método do termopar ferramenta-peça. / Doutor em Engenharia Mecânica
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[en] STUDY OF WAX DEPOSITS IN PIPELINES / [pt] ESTUDO DE DEPÓSITOS DE PARAFINA EM DUTOSHELENA MARIA BORJA VEIGA 08 August 2017 (has links)
[pt] O presente trabalho forneceu informações originais para auxiliar o entendimento dos fenômenos básicos que governam a deposição de parafina em dutos. O programa de pesquisa estudou questões relevantes, ainda em aberto na literatura, relacionadas à formação, crescimento e envelhecimento de depósitos
de parafina. Com este objetivo, foi desenvolvido um programa experimental seguindo a estratégia de conduzir experimentos simples, empregando seções de teste em escala de laboratório, com condições de contorno e iniciais bem definidas, e empregando fluidos de teste simples e com propriedades conhecidas.
As medidas foram realizadas em seções de testes retangular e anular, ambas especialmente projetadas para permitir medidas ópticas da evolução temporal e espacial da espessura dos depósitos. As seções de testes foram equipadas com um sensor de fluxo de calor, sondas de temperatura móveis e janelas
para amostragem de depósitos, que permitiram a medição de grandezas importantes como, condutividade térmica do depósito sob condições de escoamento, perfis de temperatura dentro do depósito, evolução da temperatura da interface depósito-líquido, e composição do depósito. A variação espacial e temporal da espessura do depósito foi medida para diferentes valores do número de Reynolds laminar. Excelente concordância foi obtida entre os valores medidos e previsões de um modelo numérico desenvolvido previamente em nosso grupo de pesquisa. Medidas da evolução temporal da temperatura da interface depósito-líquido mostraram que a temperatura da interface evolui de um valor igual à temperatura inicial de aparecimento de cristais da solução, TIAC, até a temperatura de desaparecimento de cristais, TDC, a medida que o depósitos cresce até sua espessura de regime permanente. A sonda de temperatura
foi utilizada na medição de perfis transversais de temperatura dentro do depósitos sob condições de escoamento. A comparação destes perfis com soluções teóricas apontaram para a possibilidade de ocorrência de escoamento dentro da matriz porosa do depósitos. As medições da condutividade térmica
do depósitos sob condições de escoamento não apresentaram qualquer efeito da taxa de cisalhamento imposta, para a faixa de número de Reynolds investigada. Variações transversais da condutividade térmica do depósitos indicaram a presença de líquido próximo à parede fria. Amostras do depósitos foram obtidas e analisadas por cromatografia gasosa de alta temperatura para a faixa de número de Reynolds laminares investigadas, e para diferentes durações dos experimentos de deposição. As análises indicaram que as distribuições de carbono das amostras de depósitos apresentaram um deslocamento em direção
aos maiores números de carbono com o aumento do Reynolds e do tempo de deposição, caracterizando o processo de envelhecimento do depósito. As distribuições do número de carbono apresentaram um comportamento assintótico com o número de Reynolds, para amostras obtidas dos trechos finais dos comprimentos de deposição da seção de testes anular. / [en] The present research provided original information to aid the understanding of the physical mechanisms governing wax deposition in pipelines. The research program addressed a number of relevant open questions in the literature regarding the formation, growth and aging of the wax deposit layer. To this end, an experimental program was devised, following a strategy of conducting simple experiments, employing lab-scale test sections with well-defined boundary and initial conditions, and using simple test uids with known properties. Measurements were performed in a rectangular and in an annular test section, both especially designed to allow for optical measurements of the time evolution of the spatial distribution of the wax deposit thickness. The test sections were equipped with heat ux sensor, temperature traversing probes and deposit sampling ports that allowed the measurement of relevant local information on the deposit, such as, thermal conductivity under owing conditions, temperature profiles within the deposit, deposit-liquid interface temperature, and deposit composition. The temporal and spatial evolution of the deposit layer were measured for different values of the laminar ow Reynolds number. Excellent agreement was obtained between measured values of the deposit thickness and predictions from a numerical model developed previously in our research group. Measurements of the evolution of the deposit-liquid interface temperature have shown that the interface temperature evolves from a value equal to the solution wax appearance temperature, WAT, to the wax disappearance temperature, WDT, as the deposit grows to attain its steady state thickness. The temperature traversing probe was employed to obtain information on the temperature profiles within the wax deposit layer under owing conditions. A comparison of the measured temperature profiles within the deposit with the theoretical solutions, indicated the possibility of convective transport in the deposit. Measurements of the deposit thermal conductivity under owing conditions did not reveal any effects of the imposed shear rate, for the range of Reynolds numbers investigated. Local variations of the thermal conductivity across the deposit layer indicated the presence of liquid close to the cold wall. Deposit samples were obtained and analyzed by high temperature gas chromatography, for the range of the laminar Reynolds numbers tested and for different durations of the deposition experiments. The analyzes revealed that the carbon distributions of the deposit samples presented a shift toward higher carbon numbers both, with increasing deposition time and Reynolds number, characterizing the aging process of the deposit. The carbon number distributions were seen to display an asymptotic behavior with Reynolds number, for samples obtained from the final portion of the longer deposition lengths of the annular test section.
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[pt] FORMAÇÃO DE DEPÓSITOS DE PARAFINA EM LINHAS DE PETRÓLEO: INVESTIGAÇÃO SOBRE AS CARACTERÍSTICAS DA INTERFACE DEPÓSITO-LÍQUIDO / [en] WAX DEPOSITS FORMATION IN PETROLEUM PIPELINES: INVESTIGATION OF THE DEPOSIT-LIQUID INTERFACE CHARACTERISTICSRICARDO CAVALCANTI LINHARES 24 May 2021 (has links)
[pt] Deposição de parafina em linhas de produção e transporte de petróleo é um problema relevante para a indústria. Perdas significativas de produção e com operações de limpeza, desobstrução ou substituição de linhas ocorrem devido à formação de depósitos das frações mais pesadas do petróleo sobre a superfície interna dos dutos operando nas águas frias típicas da produção em águas profundas. A formação de depósitos de parafina nas superfícies dos dutos pode ocorrer quando o petróleo quente proveniente dos poços é resfriado abaixo de uma temperatura crítica onde há o início da formação de cristais de parafina. Esta temperatura é denominada TIAC – temperatura inicial de aparecimento de cristais. A previsão da deposição de parafina através de modelos de simulação é uma ferramenta fundamental para o projeto e operação das linhas de forma economia e segura. Diversos modelos de deposição de parafina vêm sendo desenvolvidos ao longo dos anos, incorporando diferente propostas para o fenômeno de deposição de parafina. No presente trabalho o fenômeno da deposição de parafina foi estudado utilizando um fluido modelo escoado em uma seção de testes anular construída de modo a oferecer condições de contorno e iniciais bem definidas. Acesso óptico ao interior da seção de testes permitiu a obtenção de imagens de qualidade da formação de cristais de parafina. Uma sonda de temperatura de pequenas dimensões foi utilizada para obter informações originais sobre perfis de temperatura no depósito durante sua formação. Também foram obtidas informações sobre a evolução temporal da temperatura da interface do depósito para diferentes vazões e taxas de resfriamento. A formação transitória de nuvens de cristais sobre a interface do depósito e carregados pelo escoamento foi registrada em imagens de alta frequência. A temperatura no interior dessas nuvens foi registrada pela sonda de temperatura. Os resultados mostraram que a interface do depósito evolui a partir da TIAC da solução medida por microscopia, atingindo rapidamente uma temperatura constante de valor intermediário entre a TIAC e a temperatura termodinâmica de mudança de fase da solução. Esta informação contraria umas das hipóteses fundamentais do mecanismo de difusão molecular, base dos modelos acadêmicos e industriais mais utilizados. A presença de cristais de parafina em solução em temperaturas acima da TIAC indica que, localmente, o valor da TIAC difere daquele obtida por microscopia, e que as taxas locais de resfriamento são inferiores às impostas junto à parede fria, permitindo a formação dos cristais acima dos depósitos. Os dados experimentais de qualidade obtidos no presente trabalho são uma importante referência para o teste de modelos de simulação do processo de deposição. / [en] Wax deposition in petroleum production and transportation lines is one of the most relevant problems faced by the industry in order to assure the flow of oil and gas at the designed economical rates. Significant losses occur due to decreased production, line replacements and maintenance costs associated with cleaning operations. Wax deposit formation on the inner wall of the pipes might occur when the warm oil from the well loses heat to the cold environment, typical of deep water production operations, and its temperature reaches a critical value at which wax crystal formation occurs. This critical temperature is the WAT, wax appearance temperature. The prediction of wax deposit formation by simulation models is of fundamental importance for the proper design and operation of petroleum lines. Several wax deposition models have been developed and employed over the years, incorporating different wax deposition mechanisms. In the present work, the wax deposition phenomenon was studied employing a model fluid flowing through an annular test section, built to offer simple and well-defined boundary and initial conditions for the deposition process. Optical access to the interior of the test section allowed for the registration of images of the wax deposit formation. A miniature temperature probe was designed and employed to obtain original information on the temperature profiles within the deposit as it was formed. Also, the probe registered the transient evolution of the deposit interface temperature for different flow rates and cooling rates. The transient formation of a cloud of wax crystals over the deposit interface and carried by the flow was registered by a high frame rate camera. The temperature within this cloud was measured by the temperature probe. The results have shown that the deposit interface temperature evolves from a value equal to the WAT of the fluid measured by microscopy, rapidly reaching a constant value which is intermediate between the WAT and the solution thermodynamic phase change temperature. This information contradicts one of the key assumptions included in the molecular diffusion deposition mechanism, and widely employed in academic and industrial simulation models. Wax deposition in petroleum production and transportation lines is one of the most relevant problems faced by the industry in order to assure the flow of oil and gas at the designed economical rates. Significant losses occur due to decreased production, line replacements and maintenance costs associated with cleaning operations. Wax deposit formation on the inner wall of the pipes might occur when the warm oil from the well loses heat to the cold environment, typical of deep water production operations, and its temperature reaches a critical value at which wax crystal formation occurs. This critical temperature is the WAT, wax appearance temperature. The prediction of wax deposit formation by simulation models is of fundamental importance for the proper design and operation of petroleum lines. Several wax deposition models have been developed and employed over the years, incorporating different wax deposition mechanisms. In the present work, the wax deposition phenomenon was studied employing a model fluid flowing through an annular test section, built to offer simple and well-defined boundary and initial conditions for the deposition process. Optical access to the interior of the test section allowed for the registration of images of the wax deposit formation. A miniature temperature probe was designed and employed to obtain original information on the temperature profiles within the deposit as it was formed. Also, the probe registered the transient evolution of the deposit interface temperature for different flow rates and cooling rates. The transient formation of a cloud of wax crystals over the deposit interface and carried by the flow was registered by a high frame rate camera. The temperature within this cloud was measured by the temperature probe. The results have shown that the deposit interface temperature evolves from a value equal to the WAT of the fluid measured by microscopy, rapidly reaching a constant value which is intermediate between the WAT and the solution thermodynamic phase change temperature. This information contradicts one of the key assumptions included in the molecular diffusion deposition mechanism, and widely employed in academic and industrial simulation models.
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