Plug flow (original) (raw)
Propstroom of propstroming (Engels: plug flow) is een benadering van het stromingsprofiel in een buis bij hogere snelheden. Bij deze snelheden is het stromingsprofiel niet meer parabolisch zoals in laminaire stroming, maar is de snelheid in het midden van de buis ongeveer constant, en valt ze pas vlak bij de wand snel af naar nul (de zogeheten grenslaag). Bij de beschrijving als propstroming neemt men aan dat de snelheid volledig constant is over de gehele doorsnede van de buis. Deze benadering wordt onder meer toegepast in de chemische technologie bij het ontwerp van reactoren.
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| dbo:abstract | Eine Pfropfenströmung (engl.: plug flow, auch Kolbenströmung) ist in der Strömungslehre eine Strömung in einem Rohr, bei der die Strömungsgeschwindigkeit fast überall im Strömungsquerschnitt gleich hoch ist. Lediglich direkt an der Rohrwand weist sie einen sprunghaften Geschwindigkeitsabfall auf. Das Medium bewegt sich dann bildlich gesprochen wie ein Pfropfen im Rohr. Die Pfropfenströmung steht im Gegensatz zum parabolischen Strömungsprofil, das sich in der laminaren Strömung einer idealviskosen (newtonschen) Flüssigkeit ausbildet. In einem solchen parabolischen Strömungsprofil geht die lokale Scherung in der Rohrmitte gegen null und wird an der Wand maximal. Ein Übergang von der Pfropfen- zur parabolischen Strömung erfolgt, wenn die Viskosität des Materials in Richtung der Wand abnimmt, z. B. durch Scherverdünnung. (de) In fluid mechanics, plug flow is a simple model of the velocity profile of a fluid flowing in a pipe. In plug flow, the velocity of the fluid is assumed to be constant across any cross-section of the pipe perpendicular to the axis of the pipe. The plug flow model assumes there is no boundary layer adjacent to the inner wall of the pipe. The plug flow model has many practical applications. One example is in the design of chemical reactors. Essentially no back mixing is assumed with "plugs" of fluid passing through the reactor. This results in differential equations that need to be integrated to find the reactor conversion and outlet temperatures. Other simplifications used are perfect radial mixing and a homogeneous bed structure. An advantage of the plug flow model is that no part of the solution of the problem can be perpetuated "upstream". This allows one to calculate the exact solution to the differential equation knowing only the initial conditions. No further iteration is required. Each "plug" can be solved independently provided the previous plug's state is known. The flow model in which the velocity profile consists of the fully developed boundary layer is known as pipe flow. In laminar pipe flow, the velocity profile is parabolic. (en) Propstroom of propstroming (Engels: plug flow) is een benadering van het stromingsprofiel in een buis bij hogere snelheden. Bij deze snelheden is het stromingsprofiel niet meer parabolisch zoals in laminaire stroming, maar is de snelheid in het midden van de buis ongeveer constant, en valt ze pas vlak bij de wand snel af naar nul (de zogeheten grenslaag). Bij de beschrijving als propstroming neemt men aan dat de snelheid volledig constant is over de gehele doorsnede van de buis. Deze benadering wordt onder meer toegepast in de chemische technologie bij het ontwerp van reactoren. (nl) Em mecânica dos fluidos, fluxo em pistão é um modelo simples do perfil de velocidade de um fluido fluindo em um tubo. Em um fluxo em pistão, a velocidade do fluido é suposto ser constante através de qualquer seção transversal do tubo perpendicular ao eixo do tubo. O modelo do fluxo em pistão supõe não existir camada limite adjacente à parede interna do tubo. O modelo do fluxo em pistão tem muitas aplicações práticas. Um exemplo é no projeto de reatores químicos. Essencialmente nenhuma mistura com o volume de fluido da retaguarda do pistão é suposto com "pistões" passando através do reator (noutras palavras, no fluxo em pistão ideal não há intercâmbios entre as seções de jusante e de montante). Isto resulta em equações diferenciais que necessitam ser integradas para encontrar-se a conversão do reator e temperaturas de saída. Outras simplificações usadas são mistura axial perfeita ("dentro" do pistão) e uma estrutura de leito homogênea. Uma vantagem do modelo do fluxo em pistão é que nenhuma parte da solução do problema pode ser perpetuada "a montante" (do ponto do pistão a corrente adiante). Isto permite calcular-se a solução exata em equações diferenciais conhecendo-se somente as condições iniciais. Nenhum iteração adicional é necessária. Cada "pistão" pode ser resolvido independentemente dado que o estado do pistão prévio seja conhecido. O modelo de fluxo em que o perfil de velocidade consiste no pleno desenvolvimento de camada limite é conhecido como fluxo tubular. Em fluxo tubular laminar, o perfil de velocidade é parabólico. (pt) |
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| rdfs:comment | Propstroom of propstroming (Engels: plug flow) is een benadering van het stromingsprofiel in een buis bij hogere snelheden. Bij deze snelheden is het stromingsprofiel niet meer parabolisch zoals in laminaire stroming, maar is de snelheid in het midden van de buis ongeveer constant, en valt ze pas vlak bij de wand snel af naar nul (de zogeheten grenslaag). Bij de beschrijving als propstroming neemt men aan dat de snelheid volledig constant is over de gehele doorsnede van de buis. Deze benadering wordt onder meer toegepast in de chemische technologie bij het ontwerp van reactoren. (nl) Eine Pfropfenströmung (engl.: plug flow, auch Kolbenströmung) ist in der Strömungslehre eine Strömung in einem Rohr, bei der die Strömungsgeschwindigkeit fast überall im Strömungsquerschnitt gleich hoch ist. Lediglich direkt an der Rohrwand weist sie einen sprunghaften Geschwindigkeitsabfall auf. Das Medium bewegt sich dann bildlich gesprochen wie ein Pfropfen im Rohr. Ein Übergang von der Pfropfen- zur parabolischen Strömung erfolgt, wenn die Viskosität des Materials in Richtung der Wand abnimmt, z. B. durch Scherverdünnung. (de) In fluid mechanics, plug flow is a simple model of the velocity profile of a fluid flowing in a pipe. In plug flow, the velocity of the fluid is assumed to be constant across any cross-section of the pipe perpendicular to the axis of the pipe. The plug flow model assumes there is no boundary layer adjacent to the inner wall of the pipe. The flow model in which the velocity profile consists of the fully developed boundary layer is known as pipe flow. In laminar pipe flow, the velocity profile is parabolic. (en) Em mecânica dos fluidos, fluxo em pistão é um modelo simples do perfil de velocidade de um fluido fluindo em um tubo. Em um fluxo em pistão, a velocidade do fluido é suposto ser constante através de qualquer seção transversal do tubo perpendicular ao eixo do tubo. O modelo do fluxo em pistão supõe não existir camada limite adjacente à parede interna do tubo. O modelo de fluxo em que o perfil de velocidade consiste no pleno desenvolvimento de camada limite é conhecido como fluxo tubular. Em fluxo tubular laminar, o perfil de velocidade é parabólico. (pt) |
| rdfs:label | Pfropfenströmung (de) Plug flow (en) Propstroom (nl) Fluxo em pistão (pt) |
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