{"id":47479,"date":"2019-11-05T04:02:51","date_gmt":"2019-11-05T03:02:51","guid":{"rendered":"https:\/\/www.thermal-engineering.org\/o-que-e-externo-x-interno-numero-nusselt-definicao\/"},"modified":"2020-01-23T14:46:21","modified_gmt":"2020-01-23T13:46:21","slug":"o-que-e-externo-x-interno-numero-nusselt-definicao","status":"publish","type":"post","link":"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-externo-x-interno-numero-nusselt-definicao\/","title":{"rendered":"O que \u00e9 Externo x Interno &#8211; N\u00famero Nusselt &#8211; Defini\u00e7\u00e3o"},"content":{"rendered":"<div class=\"su-quote su-quote-style-default\">\n<div class=\"su-quote-inner su-clearfix\">Externo vs Interno &#8211; N\u00famero Nusselt &#8211; C\u00e1lculo do coeficiente de transfer\u00eancia de calor por convec\u00e7\u00e3o.\u00a0Deste ponto de vista, distinguimos: Fluxo Interno, Fluxo Externo.\u00a0Engenharia T\u00e9rmica<\/div>\n<\/div>\n<div class=\"su-divider su-divider-style-dotted\"><\/div>\n<div class=\"lgc-column lgc-grid-parent lgc-grid-100 lgc-tablet-grid-100 lgc-mobile-grid-100 lgc-equal-heights lgc-first lgc-last\">\n<div class=\"inside-grid-column\">\n<div class=\"su-spacer\"><\/div>\n<h2>Classifica\u00e7\u00e3o dos regimes de fluxo<\/h2>\n<p>O\u00a0<a title=\"Regime de fluxo\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/flow-regime\/\"><strong>regime de fluxo<\/strong><\/a>\u00a0tamb\u00e9m pode ser classificado de acordo com a\u00a0\u00a0<strong>geometria de um condu\u00edte<\/strong>\u00a0\u00a0ou \u00e1rea de fluxo.\u00a0Deste ponto de vista, distinguimos:<\/p>\n<ul>\n<li><a title=\"Fluxo Interno\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/internal-flow\/\"><strong>Fluxo Interno<\/strong><\/a><\/li>\n<li><a title=\"Fluxo externo\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/external-flow\/\"><strong>Fluxo externo<\/strong><\/a><\/li>\n<\/ul>\n<p><strong>Fluxo interno<\/strong>\u00a0\u00a0\u00e9 um fluxo para o qual o fluido \u00e9 confinado por uma superf\u00edcie.\u00a0O conhecimento detalhado do comportamento dos regimes de fluxo interno \u00e9\u00a0\u00a0<strong>importante na engenharia<\/strong>\u00a0, porque os tubos circulares podem suportar altas press\u00f5es e, portanto, s\u00e3o usados \u200b\u200bpara transportar l\u00edquidos.\u00a0Por outro lado,\u00a0\u00a0<strong>o fluxo externo<\/strong>\u00a0\u00a0\u00e9 um fluxo no qual as camadas limite se desenvolvem livremente, sem restri\u00e7\u00f5es impostas pelas superf\u00edcies adjacentes.\u00a0O conhecimento detalhado do comportamento dos\u00a0\u00a0\u00a0regimes de\u00a0<strong>fluxo externo<\/strong>\u00a0\u00e9\u00a0\u00a0<strong>importante, especialmente em aeron\u00e1utica<\/strong>\u00a0\u00a0e\u00a0\u00a0<strong>aerodin\u00e2mica<\/strong> .<\/p>\n<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<div class=\"lgc-column lgc-grid-parent lgc-grid-100 lgc-tablet-grid-100 lgc-mobile-grid-100 lgc-equal-heights  lgc-first lgc-last\">\n<div class=\"inside-grid-column\">\n<h2><span>Fluxo externo<\/span><\/h2>\n<p><span>Na\u00a0<\/span><a title=\"Din\u00e2mica de Fluidos\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/\"><span>din\u00e2mica de fluidos<\/span><\/a><span>\u00a0,\u00a0\u00a0<\/span><a title=\"Fluxo externo\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/external-flow\/\"><strong><span>o fluxo externo<\/span><\/strong><\/a><span>\u00a0\u00a0\u00e9 um fluxo no qual\u00a0\u00a0<\/span><a title=\"Camada limite\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-camada-de-limite-definicao\/\"><strong><span>as camadas limite se<\/span><\/strong><\/a><span>\u00a0\u00a0desenvolvem livremente, sem restri\u00e7\u00f5es impostas pelas\u00a0\u00a0<\/span><strong><span>superf\u00edcies adjacentes<\/span><\/strong><span>\u00a0.\u00a0Em compara\u00e7\u00e3o ao fluxo interno, os fluxos externos apresentam\u00a0\u00a0<\/span><strong><span>efeitos altamente viscosos,<\/span><\/strong><span>\u00a0\u00a0confinados a \u201c\u00a0<\/span><strong><span>camadas limite<\/span><\/strong><span>\u00a0\u201d em\u00a0r\u00e1pido crescimento\u00a0na regi\u00e3o de entrada ou a camadas finas de cisalhamento ao longo da superf\u00edcie s\u00f3lida.\u00a0Assim, sempre haver\u00e1 uma regi\u00e3o do fluxo fora da camada limite.\u00a0Nessa regi\u00e3o, a velocidade, a temperatura e \/ ou a concentra\u00e7\u00e3o n\u00e3o mudam e seus gradientes podem ser negligenciados.<\/span><\/p>\n<p><span>Esse efeito faz com que a\u00a0\u00a0<\/span><strong><span>camada limite<\/span><\/strong><span>\u00a0\u00a0se expanda e a espessura da camada limite se relaciona com a viscosidade cinem\u00e1tica do fluido.<\/span><\/p>\n<p><span>Isso \u00e9 demonstrado na figura a seguir.\u00a0Longe do corpo, o fluxo \u00e9 quase inv\u00edscido, pode ser definido como o fluxo de um fluido em torno de um corpo que est\u00e1 completamente submerso nele.<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Boundary-layer-on-flat-plate.png?d484e7\"><img loading=\"lazy\" class=\"aligncenter size-large wp-image-14390 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Boundary-layer-on-flat-plate-1024x357.png?d484e7\" alt=\"Camada limite na placa plana\" width=\"669\" height=\"233\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Boundary-layer-on-flat-plate-1024x357.png?d484e7\" \/><\/a><\/p>\n<\/div>\n<\/div>\n<div class=\"lgc-column lgc-grid-parent lgc-grid-100 lgc-tablet-grid-100 lgc-mobile-grid-100 lgc-equal-heights  lgc-first lgc-last\">\n<div class=\"inside-grid-column\">\n<div class=\"su-spacer\"><\/div>\n<h2><span>Fluxo externo &#8211; placa plana<\/span><\/h2>\n<p><span>O\u00a0<\/span><a title=\"O que \u00e9 o n\u00famero Nusselt\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/heat-transfer\/introduction-to-heat-transfer\/characteristic-numbers\/what-is-nusselt-number\/\"><strong><span>n\u00famero<\/span><\/strong>\u00a0<\/a><span>m\u00e9dio de\u00a0<a title=\"O que \u00e9 o n\u00famero Nusselt\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/heat-transfer\/introduction-to-heat-transfer\/characteristic-numbers\/what-is-nusselt-number\/\"><strong>Nusselt<\/strong><\/a>\u00a0em toda a placa \u00e9 determinado por:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/laminar-flow-flat-plate-nusselt-number.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20504 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/laminar-flow-flat-plate-nusselt-number.png\" alt=\"fluxo laminar - placa plana - n\u00famero nusselt\" width=\"626\" height=\"235\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/laminar-flow-flat-plate-nusselt-number.png\" \/><\/a><\/p>\n<p><span>Essa rela\u00e7\u00e3o fornece o\u00a0<\/span><strong><a title=\"Coeficiente de transfer\u00eancia de calor por convec\u00e7\u00e3o\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-coeficiente-de-transferencia-de-calor-por-conveccao-definicao\/\"><span>coeficiente<\/span><\/a><\/strong><span>\u00a0m\u00e9dio de\u00a0<strong><a title=\"Coeficiente de transfer\u00eancia de calor por convec\u00e7\u00e3o\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-coeficiente-de-transferencia-de-calor-por-conveccao-definicao\/\">transfer\u00eancia de calor<\/a><\/strong>\u00a0para toda a placa quando o fluxo \u00e9\u00a0<\/span><a title=\"Fluxo Laminar - Fluxo Viscoso\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-fluxo-laminar-fluxo-viscoso-definicao\/\"><span>laminar<\/span><\/a><span>\u00a0sobre toda a placa.<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/turbulent-flow-flat-plate-nusselt-number.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20505 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/turbulent-flow-flat-plate-nusselt-number.png\" alt=\"fluxo turbulento - placa plana - n\u00famero de nusselt\" width=\"565\" height=\"243\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/turbulent-flow-flat-plate-nusselt-number.png\" \/><\/a><\/p>\n<p><span>Essa rela\u00e7\u00e3o fornece o\u00a0<\/span><a title=\"Coeficiente de transfer\u00eancia de calor por convec\u00e7\u00e3o\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-coeficiente-de-transferencia-de-calor-por-conveccao-definicao\/\"><strong><span>coeficiente<\/span><\/strong><\/a><span>\u00a0m\u00e9dio de\u00a0<a title=\"Coeficiente de transfer\u00eancia de calor por convec\u00e7\u00e3o\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-coeficiente-de-transferencia-de-calor-por-conveccao-definicao\/\"><strong>transfer\u00eancia de calor<\/strong><\/a>\u00a0para a placa inteira somente quando o fluxo \u00e9\u00a0<\/span><a title=\"Fluxo turbulento\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-fluxo-turbulento-definicao\/\"><strong><span>turbulento<\/span><\/strong>\u00a0<\/a><span>sobre a placa inteira ou quando a\u00a0regi\u00e3o de\u00a0<\/span><a title=\"Fluxo Laminar - Fluxo Viscoso\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-fluxo-laminar-fluxo-viscoso-definicao\/\"><span>fluxo laminar<\/span><\/a><span>\u00a0da placa \u00e9 muito pequena em rela\u00e7\u00e3o \u00e0 regi\u00e3o do fluxo turbulento.<\/span><\/p>\n<\/div>\n<\/div>\n<div class=\"lgc-column lgc-grid-parent lgc-grid-100 lgc-tablet-grid-100 lgc-mobile-grid-100 lgc-equal-heights  lgc-first lgc-last\">\n<div class=\"inside-grid-column\">\n<div class=\"su-spacer\"><\/div>\n<h2><span>Fluxo Interno<\/span><\/h2>\n<figure id=\"attachment_14394\" class=\"wp-caption alignright\" aria-describedby=\"caption-attachment-14394\"><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Internal-Flow.png\"><img loading=\"lazy\" class=\"size-medium wp-image-14394 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Internal-Flow-300x269.png\" alt=\"Fluxo Interno\" width=\"300\" height=\"269\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Internal-Flow-300x269.png\" \/><\/a><figcaption id=\"caption-attachment-14394\" class=\"wp-caption-text\"><span>Fonte: White Frank M., Mec\u00e2nica dos Fluidos, McGraw-Hill Education, 7\u00aa edi\u00e7\u00e3o, fevereiro de 2010, ISBN: 978-0077422417<\/span><\/figcaption><\/figure>\n<p><span>Na\u00a0<\/span><a title=\"Din\u00e2mica de Fluidos\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/\"><span>din\u00e2mica de fluidos<\/span><\/a><span>\u00a0,\u00a0<\/span><a title=\"Fluxo Interno\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/internal-flow\/\"><strong><span>o fluxo interno<\/span><\/strong><\/a><span>\u00a0\u00e9 um fluxo para o qual o fluido \u00e9\u00a0\u00a0<\/span><strong><span>confinado por uma superf\u00edcie<\/span><\/strong><span>\u00a0.\u00a0O conhecimento detalhado do comportamento dos regimes de fluxo interno \u00e9 importante na engenharia, porque os tubos circulares podem suportar altas press\u00f5es e, portanto, s\u00e3o usados \u200b\u200bpara transportar l\u00edquidos.\u00a0Dutos n\u00e3o circulares s\u00e3o usados \u200b\u200bpara transportar gases de baixa press\u00e3o, como ar em sistemas de refrigera\u00e7\u00e3o e aquecimento.\u00a0A configura\u00e7\u00e3o do fluxo interno \u00e9 uma geometria conveniente para fluidos de aquecimento e resfriamento usados \u200b\u200bem tecnologias de convers\u00e3o de energia, como\u00a0\u00a0<\/span><a title=\"Usina nuclear\" href=\"https:\/\/www.nuclear-power.com\/nuclear-power-plant\/\"><span>usinas nucleares<\/span><\/a><span>\u00a0.<\/span><\/p>\n<p><span>Para\u00a0\u00a0<\/span><a title=\"Fluxo Interno\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/internal-flow\/\"><span>o regime de fluxo interno,<\/span><\/a><span>\u00a0\u00a0uma\u00a0\u00a0<\/span><strong><span>regi\u00e3o de entrada<\/span><\/strong><span>\u00a0\u00a0\u00e9 t\u00edpica.\u00a0Nesta regi\u00e3o, um fluxo a montante quase inviscido a montante converge e entra no tubo.\u00a0Para caracterizar esta regi\u00e3o, o\u00a0\u00a0<\/span><strong><span>comprimento da entrada hidrodin\u00e2mica<\/span><\/strong><span>\u00a0\u00a0\u00e9 introduzido e \u00e9 aproximadamente igual a:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/hydrodynamic-entrance-length.png?d484e7\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-14416 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/hydrodynamic-entrance-length.png?d484e7\" alt=\"comprimento hidrodin\u00e2mico da entrada\" width=\"365\" height=\"69\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/hydrodynamic-entrance-length.png?d484e7\" \/><\/a><\/p>\n<p><span>O comprimento m\u00e1ximo de entrada hidrodin\u00e2mica, em\u00a0\u00a0<\/span><strong><span>Re\u00a0<\/span><sub><span>D, crit<\/span><\/sub><span>\u00a0\u00a0= 2300<\/span><\/strong><span>\u00a0\u00a0(\u00a0<\/span><strong><span>fluxo laminar<\/span><\/strong><span>\u00a0), \u00e9 L\u00a0<\/span><sub><span>e<\/span><\/sub><span>\u00a0\u00a0= 138d, onde D \u00e9 o di\u00e2metro do tubo.\u00a0Esse \u00e9 o maior comprimento de desenvolvimento poss\u00edvel.\u00a0Em\u00a0\u00a0<\/span><strong><span>escoamento turbulento<\/span><\/strong><span>\u00a0, as camadas limite crescer mais rapidamente, e L\u00a0<\/span><sub><span>e<\/span><\/sub><span>\u00a0\u00a0\u00e9 relativamente mais curto.\u00a0Para qualquer problema,\u00a0\u00a0<\/span><strong><span>L\u00a0<\/span><sub><span>e<\/span><\/sub><span>\u00a0\u00a0\/ D<\/span><\/strong><span>\u00a0\u00a0deve ser\u00a0\u00a0<\/span><strong><span>verificado<\/span><\/strong><span>\u00a0\u00a0para ver se L\u00a0<\/span><sub><span>e<\/span><\/sub><span>\u00a0\u00a0\u00e9 insignificante quando comparado ao comprimento do tubo.\u00a0A uma dist\u00e2ncia finita da entrada, os efeitos da entrada podem ser negligenciados, porque as camadas de fronteira se fundem e o n\u00facleo inv\u00edscido desaparece.\u00a0O fluxo do tubo \u00e9 ent\u00e3o\u00a0\u00a0<\/span><strong><span>totalmente desenvolvido<\/span><\/strong><span>\u00a0.<\/span><\/p>\n<\/div>\n<\/div>\n<div class=\"lgc-column lgc-grid-parent lgc-grid-100 lgc-tablet-grid-100 lgc-mobile-grid-100 lgc-equal-heights  lgc-first lgc-last\">\n<div class=\"inside-grid-column\">\n<div class=\"su-spacer\"><\/div>\n<h2><span>Fluxo Laminar Interno &#8211; N\u00famero de Nusselt<\/span><\/h2>\n<p><strong><span>Temperatura constante da superf\u00edcie<\/span><\/strong><\/p>\n<p><span>No\u00a0<\/span><a title=\"Fluxo Laminar - Fluxo Viscoso\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-fluxo-laminar-fluxo-viscoso-definicao\/\"><strong><span>fluxo laminar<\/span><\/strong><\/a><span>\u00a0em um tubo com temperatura constante da superf\u00edcie, o fator de atrito e o\u00a0<\/span><a title=\"Coeficiente de transfer\u00eancia de calor por convec\u00e7\u00e3o\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-coeficiente-de-transferencia-de-calor-por-conveccao-definicao\/\"><strong><span>coeficiente de transfer\u00eancia de calor<\/span><\/strong><\/a><span>\u00a0permanecem constantes na regi\u00e3o totalmente desenvolvida.<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Laminar-Flow-Circular-Tube-temperature.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20508 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Laminar-Flow-Circular-Tube-temperature.png\" alt=\"Fluxo Laminar - Tubo Circular - temperatura\" width=\"560\" height=\"187\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Laminar-Flow-Circular-Tube-temperature.png\" \/><\/a><\/p>\n<p><strong><span>Fluxo de calor de superf\u00edcie constante<\/span><\/strong><\/p>\n<p><span>Portanto, para\u00a0<\/span><strong><span>fluxo laminar<\/span><\/strong><span>\u00a0totalmente desenvolvido\u00a0em um tubo circular sujeito a constante\u00a0<\/span><a title=\"Densidade do fluxo de calor - Fluxo t\u00e9rmico\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/heat-transfer\/introduction-to-heat-transfer\/heat-flux-density-thermal-flux\/\"><span>fluxo de calor na<\/span><\/a><span>\u00a0superf\u00edcie\u00a0, o n\u00famero de Nusselt \u00e9 uma constante.\u00a0N\u00e3o h\u00e1 depend\u00eancia\u00a0dos\u00a0<a title=\"O que \u00e9 o n\u00famero Prandtl\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/heat-transfer\/introduction-to-heat-transfer\/characteristic-numbers\/what-is-prandtl-number\/\">n\u00fameros de\u00a0<\/a><\/span><a title=\"N\u00famero de Reynolds\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/reynolds-number\/\"><span>Reynolds<\/span><\/a><span>\u00a0ou\u00a0<\/span><a title=\"O que \u00e9 o n\u00famero Prandtl\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/heat-transfer\/introduction-to-heat-transfer\/characteristic-numbers\/what-is-prandtl-number\/\"><span>Prandtl<\/span><\/a><span>\u00a0.<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Laminar-Flow-Circular-Tube-flux.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20507 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Laminar-Flow-Circular-Tube-flux.png\" alt=\"Fluxo Laminar - Tubo Circular - fluxo\" width=\"532\" height=\"191\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Laminar-Flow-Circular-Tube-flux.png\" \/><\/a><\/p>\n<\/div>\n<\/div>\n<div class=\"lgc-column lgc-grid-parent lgc-grid-100 lgc-tablet-grid-100 lgc-mobile-grid-100 lgc-equal-heights  lgc-first lgc-last\">\n<div class=\"inside-grid-column\">\n<div class=\"su-spacer\"><\/div>\n<h2><span>Fluxo Turbulento Interno &#8211; N\u00famero Nusselt<\/span><\/h2>\n<p><span>Veja tamb\u00e9m:\u00a0<\/span><a title=\"Equa\u00e7\u00e3o de Dittus-Boelter\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/heat-transfer\/convection-convective-heat-transfer\/dittus-boelter-equation\/\"><span>Equa\u00e7\u00e3o de Dittus-Boelter<\/span><\/a><\/p>\n<p><span>Para\u00a0\u00a0um\u00a0<\/span><a title=\"Fluxo turbulento\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-fluxo-turbulento-definicao\/\"><span>fluxo turbulento<\/span><\/a><span>\u00a0totalmente desenvolvido (hidrodinamicamente e termicamente)\u00a0\u00a0em um tubo circular liso, o\u00a0<\/span><a title=\"O que \u00e9 o n\u00famero Nusselt\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/heat-transfer\/introduction-to-heat-transfer\/characteristic-numbers\/what-is-nusselt-number\/\"><span>n\u00famero<\/span><\/a><span>\u00a0local de\u00a0\u00a0<a title=\"O que \u00e9 o n\u00famero Nusselt\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/heat-transfer\/introduction-to-heat-transfer\/characteristic-numbers\/what-is-nusselt-number\/\">Nusselt<\/a>\u00a0\u00a0pode ser obtido a partir da conhecida\u00a0\u00a0<\/span><strong><span>equa\u00e7\u00e3o de Dittus-Boelter<\/span><\/strong><span>\u00a0.\u00a0A\u00a0\u00a0<\/span><strong><span>equa\u00e7\u00e3o Dittus\u00ae Boelter<\/span><\/strong><span>\u00a0\u00a0\u00e9 f\u00e1cil de resolver, mas \u00e9 menos precisa quando existe uma grande diferen\u00e7a de temperatura no\u00a0\u00a0<\/span><a title=\"Din\u00e2mica de Fluidos\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/\"><span>fluido<\/span><\/a><span>\u00a0\u00a0e \u00e9 menos precisa para tubos \u00e1speros (muitas aplica\u00e7\u00f5es comerciais), pois \u00e9 adaptada para tubos lisos.<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Dittus-Boelter-Equation-Formula.png?d484e7\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20409 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Dittus-Boelter-Equation-Formula.png?d484e7\" alt=\"Equa\u00e7\u00e3o de Dittus-Boelter - F\u00f3rmula\" width=\"556\" height=\"278\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Dittus-Boelter-Equation-Formula.png?d484e7\" \/><\/a><\/p>\n<p><span>A\u00a0\u00a0<\/span><a title=\"Equa\u00e7\u00e3o de Dittus-Boelter\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/heat-transfer\/convection-convective-heat-transfer\/dittus-boelter-equation\/\"><strong><span>correla\u00e7\u00e3o de Dittus-Boelter<\/span><\/strong><\/a><span>\u00a0\u00a0pode ser usada para diferen\u00e7as de temperatura pequenas a moderadas, T\u00a0<\/span><sub><span>wall<\/span><\/sub><span>\u00a0\u00a0&#8211; T\u00a0<\/span><sub><span>avg<\/span><\/sub><span>\u00a0, com todas as propriedades avaliadas a uma temperatura\u00a0<\/span><sub><span>m\u00e9dia<\/span><\/sub><span>\u00a0T\u00a0<sub>avg<\/sub>\u00a0.<\/span><\/p>\n<p><span>Para fluxos caracterizados por grandes varia\u00e7\u00f5es de propriedades, as corre\u00e7\u00f5es (por exemplo, um fator de corre\u00e7\u00e3o de viscosidade\u00a0\u00a0<\/span><strong><span>\u03bc \/ \u03bc de\u00a0<\/span><\/strong><strong><sub><span>parede<\/span><\/sub><\/strong><span>\u00a0) devem ser levadas em considera\u00e7\u00e3o, por exemplo, como\u00a0recomendam\u00a0<\/span><a title=\"Equa\u00e7\u00e3o de Sieder-Tate\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/heat-transfer\/convection-convective-heat-transfer\/sieder-tate-equation\/\"><span>Sieder e Tate<\/span><\/a><span>\u00a0.<\/span><\/p>\n<\/div>\n<\/div>\n<div class=\"lgc-column lgc-grid-parent lgc-grid-100 lgc-tablet-grid-100 lgc-mobile-grid-100 lgc-equal-heights  lgc-first lgc-last\">\n<div class=\"inside-grid-column\">\n<div class=\"su-spacer\"><\/div>\n<h2><span>C\u00e1lculo do n\u00famero de Nusselt usando a equa\u00e7\u00e3o de Dittus-Boelter<\/span><\/h2>\n<p><span>Para um fluxo turbulento totalmente desenvolvido (hidrodinamicamente e termicamente) em um tubo circular liso, o\u00a0<\/span><strong><span>n\u00famero<\/span><\/strong><span>\u00a0local de\u00a0<strong>Nusselt<\/strong>\u00a0pode ser obtido a partir da conhecida\u00a0<\/span><strong><span>equa\u00e7\u00e3o Dittus\u00ae Boelter<\/span><\/strong><span>\u00a0.<\/span><\/p>\n<p><span>Para calcular o\u00a0<\/span><strong><span>n\u00famero de Nusselt<\/span><\/strong><span>\u00a0, precisamos saber:<\/span><\/p>\n<ul>\n<li><span>o\u00a0<\/span><a title=\"N\u00famero de Reynolds\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/reynolds-number\/\"><span>n\u00famero de Reynolds<\/span><\/a><span>\u00a0, que \u00e9\u00a0<\/span><strong><span>Re\u00a0<\/span><sub><span>Dh<\/span><\/sub><span>\u00a0= 575600<\/span><\/strong><\/li>\n<li><span>o\u00a0<\/span><a title=\"O que \u00e9 o n\u00famero Prandtl\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/heat-transfer\/introduction-to-heat-transfer\/characteristic-numbers\/what-is-prandtl-number\/\"><span>n\u00famero Prandtl<\/span><\/a><span>\u00a0, que \u00e9\u00a0<\/span><strong><span>Pr = 0,89<\/span><\/strong><\/li>\n<\/ul>\n<p><span>O\u00a0<\/span><strong><span>n\u00famero de Nusselt<\/span><\/strong><span>\u00a0para a convec\u00e7\u00e3o for\u00e7ada dentro do canal de combust\u00edvel \u00e9 ent\u00e3o igual a:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/nusselt-number-example.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20413 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/nusselt-number-example.png\" alt=\"n\u00famero nusselt - exemplo\" width=\"387\" height=\"58\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/nusselt-number-example.png\" \/><\/a><\/p>\n<\/div>\n<\/div>\n<div class=\"lgc-column lgc-grid-parent lgc-grid-100 lgc-tablet-grid-100 lgc-mobile-grid-100 lgc-equal-heights lgc-first lgc-last\">\n<div class=\"inside-grid-column\">\n<div class=\"su-accordion\">\n<div class=\"su-spoiler su-spoiler-style-default su-spoiler-icon-plus su-spoiler-closed\">\n<div class=\"su-spoiler-content su-clearfix\">\n<p>&nbsp;<\/p>\n<\/div>\n<\/div>\n<p>&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;.<\/p>\n<p>Este artigo \u00e9 baseado na tradu\u00e7\u00e3o autom\u00e1tica do artigo original em ingl\u00eas. Para mais informa\u00e7\u00f5es, consulte o artigo em ingl\u00eas. Voc\u00ea pode nos ajudar. Se voc\u00ea deseja corrigir a tradu\u00e7\u00e3o, envie-a para: translations@nuclear-power.com ou preencha o formul\u00e1rio de tradu\u00e7\u00e3o on-line. Agradecemos sua ajuda, atualizaremos a tradu\u00e7\u00e3o o mais r\u00e1pido poss\u00edvel. Obrigado.<\/p>\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>Externo vs Interno &#8211; N\u00famero Nusselt &#8211; C\u00e1lculo do coeficiente de transfer\u00eancia de calor por convec\u00e7\u00e3o.\u00a0Deste ponto de vista, distinguimos: Fluxo Interno, Fluxo Externo.\u00a0Engenharia T\u00e9rmica Classifica\u00e7\u00e3o dos regimes de fluxo O\u00a0regime de fluxo\u00a0tamb\u00e9m pode ser classificado de acordo com a\u00a0\u00a0geometria de um condu\u00edte\u00a0\u00a0ou \u00e1rea de fluxo.\u00a0Deste ponto de vista, distinguimos: Fluxo Interno Fluxo externo Fluxo &#8230; <a title=\"O que \u00e9 Externo x Interno &#8211; N\u00famero Nusselt &#8211; Defini\u00e7\u00e3o\" class=\"read-more\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-externo-x-interno-numero-nusselt-definicao\/\" aria-label=\"More on O que \u00e9 Externo x Interno &#8211; N\u00famero Nusselt &#8211; Defini\u00e7\u00e3o\">Ler mais<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[14],"tags":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v15.4 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>O que \u00e9 Externo x Interno - N\u00famero Nusselt - Defini\u00e7\u00e3o<\/title>\n<meta name=\"description\" content=\"Externo vs Interno - N\u00famero Nusselt - C\u00e1lculo do coeficiente de transfer\u00eancia de calor por convec\u00e7\u00e3o. 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