{"id":51834,"date":"2020-02-01T09:29:04","date_gmt":"2020-02-01T08:29:04","guid":{"rendered":"https:\/\/www.thermal-engineering.org\/o-que-e-padrao-de-fluxo-fluxo-bifasico-definicao\/"},"modified":"2020-02-01T09:36:02","modified_gmt":"2020-02-01T08:36:02","slug":"o-que-e-padrao-de-fluxo-fluxo-bifasico-definicao","status":"publish","type":"post","link":"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-padrao-de-fluxo-fluxo-bifasico-definicao\/","title":{"rendered":"O que \u00e9 padr\u00e3o de fluxo &#8211; fluxo bif\u00e1sico &#8211; defini\u00e7\u00e3o"},"content":{"rendered":"<div class=\"su-quote su-quote-style-default\">\n<div class=\"su-quote-inner su-clearfix\">As estruturas de fluxo observadas s\u00e3o definidas como padr\u00f5es de fluxo bif\u00e1sicos e possuem caracter\u00edsticas de identifica\u00e7\u00e3o particulares.\u00a0Padr\u00f5es de fluxo &#8211; fluxo bif\u00e1sico<\/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>Padr\u00f5es de fluxo &#8211; fluxo bif\u00e1sico<\/h2>\n<p>Um dos aspectos mais desafiadores de lidar com o\u00a0<strong><a title=\"Fluxo de fluido bif\u00e1sico\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-fluxo-de-fluido-bifasico-definicao\/\">fluxo bif\u00e1sico<\/a>\u00a0ou multif\u00e1sico<\/strong>\u00a0\u00e9 o fato de que ele pode assumir\u00a0<strong>muitas formas diferentes<\/strong>\u00a0.\u00a0<strong>As distribui\u00e7\u00f5es espaciais e as velocidades<\/strong>\u00a0das\u00a0<strong>fases l\u00edquida e de vapor<\/strong>\u00a0no canal de fluxo s\u00e3o aspectos muito importantes em muitos ramos da engenharia.\u00a0<strong>Quedas de press\u00e3o<\/strong>\u00a0e tamb\u00e9m\u00a0<strong>coeficientes de transfer\u00eancia de calor<\/strong>\u00a0dependem fortemente da\u00a0<strong>estrutura do fluxo local<\/strong>\u00a0e, portanto, \u00e9 importante na engenharia de\u00a0<a title=\"Reator nuclear\" href=\"https:\/\/www.nuclear-power.com\/nuclear-power-plant\/nuclear-reactor\/\"><strong>reatores nucleares<\/strong><\/a>\u00a0.\u00a0As estruturas de fluxo observadas s\u00e3o definidas como\u00a0<strong>padr\u00f5es de fluxo bif\u00e1sicos<\/strong>e estes t\u00eam caracter\u00edsticas de identifica\u00e7\u00e3o particulares.\u00a0Esses diferentes padr\u00f5es de fluxo foram\u00a0<strong>categorizados de<\/strong>\u00a0acordo com a\u00a0<strong>dire\u00e7\u00e3o do fluxo em<\/strong>\u00a0rela\u00e7\u00e3o \u00e0 acelera\u00e7\u00e3o gravitacional.<\/p>\n<ul>\n<li><strong>Padr\u00f5es de fluxo em tubos verticais<\/strong><\/li>\n<li><strong>Padr\u00f5es de fluxo em tubos horizontais<\/strong><\/li>\n<\/ul>\n<figure id=\"attachment_14848\" class=\"wp-caption alignright\" aria-describedby=\"caption-attachment-14848\"><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/flow-patterns-table.png\"><img loading=\"lazy\" class=\"size-medium wp-image-14848 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/flow-patterns-table-300x198.png\" alt=\"padr\u00f5es de fluxo\" width=\"300\" height=\"198\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/flow-patterns-table-300x198.png\" \/><\/a><figcaption id=\"caption-attachment-14848\" class=\"wp-caption-text\">Tabela de padr\u00f5es b\u00e1sicos de fluxo em tubos verticais.<\/figcaption><\/figure>\n<p>Os principais regimes de fluxo\u00a0<strong>em tubos verticais<\/strong>\u00a0s\u00e3o mostrados na tabela.\u00a0Deve-se observar que os valores de\u00a0<a title=\"Qualidade est\u00e1tica - Qualidade do fluxo\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/two-phase-fluid-flow\/static-quality-flow-quality\/\"><strong>qualidade<\/strong><\/a>e\u00a0<strong>vaz\u00e3o<\/strong>\u00a0dependem do fluido e da press\u00e3o.\u00a0<strong>Nos tubos horizontais<\/strong>\u00a0, tamb\u00e9m pode haver\u00a0<strong>fluxo estratificado<\/strong>\u00a0(especialmente em vaz\u00f5es baixas), nas quais as duas fases se\u00a0<strong>separam<\/strong>\u00a0sob o efeito da gravidade.<\/p>\n<p>Para uma vaz\u00e3o constante de l\u00edquido, a fase de vapor \/ g\u00e1s tende a ser distribu\u00edda como\u00a0<strong>pequenas bolhas<\/strong>\u00a0a baixas vaz\u00f5es de vapor.\u00a0<strong>O aumento da fra\u00e7\u00e3o de vazio<\/strong>\u00a0causa\u00a0<strong>aglomera\u00e7\u00e3o<\/strong>\u00a0de bolhas em\u00a0<strong>plugues e lesmas maiores<\/strong>\u00a0.\u00a0A aglomera\u00e7\u00e3o adicional de lesmas, causada pelo\u00a0<strong>aumento da fra\u00e7\u00e3o de vazio,<\/strong>\u00a0causa a separa\u00e7\u00e3o das fases em\u00a0<strong>padr\u00f5es anulares,<\/strong>\u00a0em que o l\u00edquido se concentra na parede do canal e o\u00a0<strong>vapor flui no n\u00facleo central<\/strong>\u00a0do canal vertical.<\/p>\n<p><strong>Para o canal horizontal<\/strong>\u00a0, a for\u00e7a gravitacional tende a drenar o anel l\u00edquido em dire\u00e7\u00e3o \u00e0 parte inferior do canal, resultando em\u00a0<strong>fluxo estratificado<\/strong>\u00a0.\u00a0A for\u00e7a gravitacional que atua na fase l\u00edquida pode ser superada por for\u00e7as cin\u00e9ticas a altas taxas de fluxo, fazendo com que fluxos estratificados voltem a fluxos anulares.\u00a0<strong>Em vaz\u00f5es muito altas<\/strong>\u00a0, o filme anular \u00e9 dilu\u00eddo pelo cisalhamento do n\u00facleo de vapor e todo o l\u00edquido \u00e9 arrastado como got\u00edculas na fase de vapor.\u00a0Esse regime de fluxo \u00e9 geralmente conhecido como\u00a0<strong>fluxo de n\u00e9voa<\/strong>\u00a0.<\/p>\n<p>Veja tamb\u00e9m:\u00a0\u00a0<strong>Livro de Dados de Engenharia III, Thome, JR, Wolverine Tube Inc, 2004.<\/strong><\/p>\n<\/div>\n<div class=\"lgc-column lgc-grid-parent lgc-grid-50 lgc-tablet-grid-50 lgc-mobile-grid-100 lgc-equal-heights  lgc-first\">\n<div class=\"inside-grid-column\">\n<h2><\/h2>\n<h2><span>Padr\u00f5es de Fluxo &#8211; Tubos Verticais<\/span><\/h2>\n<div class=\"su-spoiler su-spoiler-style-default su-spoiler-icon-plus su-spoiler-closed\">\n<ul>\n<li class=\"su-spoiler-title\" tabindex=\"0\" role=\"button\"><span>Fluxo borbulhante<\/span><\/li>\n<li class=\"su-spoiler-title\" tabindex=\"0\" role=\"button\">Fluxo de lesmas<\/li>\n<li class=\"su-spoiler-title\" tabindex=\"0\" role=\"button\">Fluxo de rotatividade<\/li>\n<li class=\"su-spoiler-title\" tabindex=\"0\" role=\"button\">Fluxo anular<\/li>\n<li class=\"su-spoiler-title\" tabindex=\"0\" role=\"button\">Fluxo de n\u00e9voa<\/li>\n<\/ul>\n<\/div>\n<div class=\"su-spoiler su-spoiler-style-default su-spoiler-icon-plus su-spoiler-closed\">\n<div class=\"su-spoiler-content su-clearfix\"><\/div>\n<\/div>\n<div class=\"su-divider su-divider-style-dotted\"><\/div>\n<\/div>\n<\/div>\n<div class=\"lgc-column lgc-grid-parent lgc-grid-50 lgc-tablet-grid-50 lgc-mobile-grid-100 lgc-equal-heights  lgc-last\">\n<div class=\"inside-grid-column\">\n<figure id=\"attachment_14791\" class=\"wp-caption alignleft\" aria-describedby=\"caption-attachment-14791\"><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Bubbly-Slug-Churn-Annular-Mist-Flow.png\"><img loading=\"lazy\" class=\"wp-image-14791 size-medium lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Bubbly-Slug-Churn-Annular-Mist-Flow-300x191.png\" alt=\"Borbulhante - Lesma - Batedeira - Anular - N\u00e9voa - Fluxo\" width=\"300\" height=\"191\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Bubbly-Slug-Churn-Annular-Mist-Flow-300x191.png\" \/><\/a><figcaption id=\"caption-attachment-14791\" class=\"wp-caption-text\"><span>Esbo\u00e7os de regimes de fluxo para fluxo bif\u00e1sico em um tubo vertical.\u00a0Fonte: Weisman, J. Padr\u00f5es de fluxo bif\u00e1sicos.\u00a0Cap\u00edtulo 15 do Manual de Fluidos em Movimento, Cheremisinoff NP, Gupta R. 1983, Ann Arbor Science Publishers.<\/span><\/figcaption><\/figure>\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<figure aria-describedby=\"caption-attachment-14788\"><\/figure>\n<figure aria-describedby=\"caption-attachment-14788\"><\/figure>\n<figure aria-describedby=\"caption-attachment-14788\"><\/figure>\n<figure aria-describedby=\"caption-attachment-14788\"><\/figure>\n<figure aria-describedby=\"caption-attachment-14788\"><\/figure>\n<figure aria-describedby=\"caption-attachment-14788\"><\/figure>\n<figure aria-describedby=\"caption-attachment-14788\"><\/figure>\n<figure aria-describedby=\"caption-attachment-14788\"><\/figure>\n<figure id=\"attachment_14788\" class=\"wp-caption aligncenter\" aria-describedby=\"caption-attachment-14788\"><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/flow-patterns-vertical-flow-Hewitt.png\"><img loading=\"lazy\" class=\"wp-image-14788 size-full lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/flow-patterns-vertical-flow-Hewitt.png\" alt=\"padr\u00f5es de fluxo - fluxo vertical - Hewitt\" width=\"428\" height=\"397\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/flow-patterns-vertical-flow-Hewitt.png\" \/><\/a><figcaption id=\"caption-attachment-14788\" class=\"wp-caption-text\"><span>O mapa do regime de fluxo vertical de Hewitt e Roberts (1969) para fluxo em um tubo de 3,2 cm de di\u00e2metro, validado para fluxo de ar \/ \u00e1gua \u00e0 press\u00e3o atmosf\u00e9rica e fluxo de vapor \/ \u00e1gua a alta press\u00e3o.\u00a0Fonte: Brennen, CE, Fundamentos de fluxos multif\u00e1sicos, Cambridge University Press, 2005, ISBN 0521 848040<\/span><\/figcaption><\/figure>\n<div class=\"su-spacer\"><\/div>\n<\/div>\n<\/div>\n<div class=\"lgc-column lgc-grid-parent lgc-grid-50 lgc-tablet-grid-50 lgc-mobile-grid-100 lgc-equal-heights  lgc-first\">\n<div class=\"inside-grid-column\">\n<div class=\"su-spacer\"><\/div>\n<h2><\/h2>\n<h2><span>Padr\u00f5es de Fluxo &#8211; Tubos Horizontais<\/span><\/h2>\n<div class=\"su-spoiler su-spoiler-style-default su-spoiler-icon-plus su-spoiler-closed\">\n<ul>\n<li class=\"su-spoiler-title\" tabindex=\"0\" role=\"button\"><span>Fluxo borbulhante<\/span><\/li>\n<li class=\"su-spoiler-title\" tabindex=\"0\" role=\"button\">Fluxo estratificado<\/li>\n<li class=\"su-spoiler-title\" tabindex=\"0\" role=\"button\">Fluxo da tomada e fluxo da lesma<\/li>\n<li class=\"su-spoiler-title\" tabindex=\"0\" role=\"button\">Fluxo anular<\/li>\n<li class=\"su-spoiler-title\" tabindex=\"0\" role=\"button\">Fluxo de n\u00e9voa<\/li>\n<\/ul>\n<\/div>\n<div class=\"su-spoiler su-spoiler-style-default su-spoiler-icon-plus su-spoiler-closed\">\n<div class=\"su-spoiler-content su-clearfix\"><\/div>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"lgc-column lgc-grid-parent lgc-grid-50 lgc-tablet-grid-50 lgc-mobile-grid-100 lgc-equal-heights  lgc-last\">\n<div class=\"inside-grid-column\">\n<figure id=\"attachment_14790\" class=\"wp-caption alignleft\" aria-describedby=\"caption-attachment-14790\"><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Bubbly-Slug-Plug-Annular-Stratified-Mist-Wavy.png\"><img loading=\"lazy\" class=\"wp-image-14790 size-medium lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Bubbly-Slug-Plug-Annular-Stratified-Mist-Wavy-300x252.png\" alt=\"bolha, plug, lesma, anular, n\u00e9voa, fluxo estratificado ou ondulado\" width=\"300\" height=\"252\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Bubbly-Slug-Plug-Annular-Stratified-Mist-Wavy-300x252.png\" \/><\/a><figcaption id=\"caption-attachment-14790\" class=\"wp-caption-text\"><span>Esbo\u00e7os de regimes de fluxo para fluxo bif\u00e1sico em um tubo horizontal.\u00a0Fonte: Weisman, J. Padr\u00f5es de fluxo bif\u00e1sicos.\u00a0Cap\u00edtulo 15 do Manual de Fluidos em Movimento, Cheremisinoff NP, Gupta R. 1983, Ann Arbor Science Publishers.<\/span><\/figcaption><\/figure>\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<figure aria-describedby=\"caption-attachment-14789\"><\/figure>\n<figure aria-describedby=\"caption-attachment-14789\"><\/figure>\n<figure aria-describedby=\"caption-attachment-14789\"><\/figure>\n<figure aria-describedby=\"caption-attachment-14789\"><\/figure>\n<figure aria-describedby=\"caption-attachment-14789\"><\/figure>\n<figure aria-describedby=\"caption-attachment-14789\"><\/figure>\n<figure aria-describedby=\"caption-attachment-14789\"><\/figure>\n<figure aria-describedby=\"caption-attachment-14789\"><\/figure>\n<figure aria-describedby=\"caption-attachment-14789\"><\/figure>\n<figure aria-describedby=\"caption-attachment-14789\"><\/figure>\n<figure aria-describedby=\"caption-attachment-14789\"><\/figure>\n<figure id=\"attachment_14789\" class=\"wp-caption aligncenter\" aria-describedby=\"caption-attachment-14789\"><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/flow-patterns-horizontal-flow.png\"><img loading=\"lazy\" class=\"wp-image-14789 size-full lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/flow-patterns-horizontal-flow.png\" alt=\"padr\u00f5es de fluxo - fluxo horizontal\" width=\"436\" height=\"416\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/flow-patterns-horizontal-flow.png\" \/><\/a><figcaption id=\"caption-attachment-14789\" class=\"wp-caption-text\"><span>Um mapa de regime de fluxo para o fluxo de uma mistura ar \/ \u00e1gua em um tubo horizontal de 2,5 cm de di\u00e2metro a 25 \u00b0 C e 1 bar.\u00a0Linhas e pontos s\u00f3lidos s\u00e3o observa\u00e7\u00f5es experimentais das condi\u00e7\u00f5es de transi\u00e7\u00e3o, enquanto as zonas tracejadas representam previs\u00f5es te\u00f3ricas.\u00a0Fonte: Mandhane, JM, Gregory, GA e Aziz, KA (1974).\u00a0Um mapa de padr\u00f5es de fluxo para fluxo g\u00e1s-l\u00edquido em tubos horizontais.\u00a0Int.\u00a0J. Fluxo multif\u00e1sico<\/span><\/figcaption><\/figure>\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><\/h2>\n<h2><span>Padr\u00f5es de fluxo durante a evapora\u00e7\u00e3o<\/span><\/h2>\n<p><span>A se\u00e7\u00e3o anterior descreve v\u00e1rios\u00a0<\/span><strong><span>padr\u00f5es de fluxo<\/span><\/strong><span>\u00a0e descreve brevemente seu comportamento.\u00a0Esses padr\u00f5es de fluxo foram considerados\u00a0<\/span><strong><span>em fra\u00e7\u00e3o de vazio constante<\/span><\/strong><span>\u00a0e\u00a0<\/span><strong><span>em velocidades superficiais constantes<\/span><\/strong><span>\u00a0.\u00a0Mas existem muitas aplica\u00e7\u00f5es industriais que precisam considerar uma\u00a0<\/span><strong><span>fra\u00e7\u00e3o de vazio<\/span><\/strong><span>\u00a0vari\u00e1vel e velocidades superficiais vari\u00e1veis.\u00a0Na ind\u00fastria nuclear, temos que lidar com os padr\u00f5es de fluxo durante a\u00a0<\/span><strong><span>evapora\u00e7\u00e3o<\/span><\/strong><span>\u00a0(isto \u00e9, durante mudan\u00e7as na\u00a0<\/span><a title=\"Fra\u00e7\u00e3o de Vazio - Fluxo de Duas Fases\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/two-phase-fluid-flow\/void-fraction-two-phase-flow\/\"><span>fra\u00e7\u00e3o de vazio<\/span><\/a><span>\u00a0).<\/span><\/p>\n<p><span>O conhecimento detalhado das\u00a0<\/span><strong><span>mudan\u00e7as<\/span><\/strong><span>\u00a0de\u00a0<strong>fase<\/strong>\u00a0e o comportamento do fluxo durante a mudan\u00e7a de fase \u00e9 uma das considera\u00e7\u00f5es mais importantes no projeto de um\u00a0<\/span><a title=\"Reator nuclear\" href=\"https:\/\/www.nuclear-power.com\/nuclear-power-plant\/nuclear-reactor\/\"><strong><span>reator nuclear<\/span><\/strong><\/a><span>\u00a0, especialmente nas seguintes aplica\u00e7\u00f5es:<\/span><\/p>\n<ul>\n<li><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/convective-evaporation-vertical-channel-fig.png\"><img loading=\"lazy\" class=\"alignright size-full wp-image-14854 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/convective-evaporation-vertical-channel-fig.png\" alt=\"evapora\u00e7\u00e3o convectiva - canal vertical\" width=\"262\" height=\"633\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/convective-evaporation-vertical-channel-fig.png\" \/><\/a><a title=\"BWR - Reator de \u00e1gua fervente\" href=\"https:\/\/www.nuclear-power.com\/bwr-boiling-water-reactor\/\"><span>BWR &#8211; Reatores de \u00e1gua fervente<\/span><\/a>\n<ul>\n<li><span>Um\u00a0<\/span><strong><span>reator de \u00e1gua fervente<\/span><\/strong><span>\u00a0\u00e9 resfriado e\u00a0<\/span><a title=\"Moderador de n\u00eautrons\" href=\"https:\/\/www.nuclear-power.com\/neutron-moderator\/\"><span>moderado<\/span><\/a><span>\u00a0por \u00e1gua como um PWR, mas a uma\u00a0<\/span><strong><span>press\u00e3o mais baixa<\/span><\/strong><span>\u00a0(7MPa), que permite que a \u00e1gua\u00a0<\/span><strong><span>ferva dentro do vaso de press\u00e3o<\/span><\/strong><span>\u00a0produzindo o vapor que aciona as turbinas.\u00a0Portanto, a evapora\u00e7\u00e3o ocorre diretamente nos canais de combust\u00edvel.\u00a0Portanto, os BWRs s\u00e3o o melhor exemplo para esta \u00e1rea, porque a evapora\u00e7\u00e3o do l\u00edquido refrigerante ocorre na opera\u00e7\u00e3o normal e \u00e9 um fen\u00f4meno muito desejado.<\/span><\/li>\n<li><span>Nos BWRs, h\u00e1 um fen\u00f4meno que \u00e9 da\u00a0<\/span><strong><span>maior import\u00e2ncia na seguran\u00e7a do reator<\/span><\/strong><span>\u00a0.\u00a0Esse fen\u00f4meno \u00e9 conhecido como\u00a0<\/span><strong><span>\u201cseca\u201d<\/span><\/strong><span>\u00a0e est\u00e1 diretamente associado a\u00a0<\/span><strong><span>altera\u00e7\u00f5es no padr\u00e3o de fluxo<\/span><\/strong><span>\u00a0durante a evapora\u00e7\u00e3o.\u00a0Normalmente, a superf\u00edcie do combust\u00edvel \u00e9 efetivamente resfriada com l\u00edquido de ebuli\u00e7\u00e3o fervente.\u00a0No entanto, quando o fluxo de calor excede um\u00a0<\/span><strong><span>valor cr\u00edtico<\/span><\/strong><span>\u00a0(CHF &#8211; fluxo de calor cr\u00edtico), o padr\u00e3o de fluxo pode atingir as\u00a0<\/span><strong><span>condi\u00e7\u00f5es de secagem<\/span><\/strong><span>\u00a0(a pel\u00edcula fina de l\u00edquido desaparece).\u00a0A transfer\u00eancia de calor da superf\u00edcie do combust\u00edvel para o refrigerante \u00e9 deteriorada, com o resultado de um\u00a0<\/span><strong><span>aumento dr\u00e1stico da temperatura da superf\u00edcie do combust\u00edvel<\/span><\/strong><span>\u00a0.<\/span><\/li>\n<\/ul>\n<\/li>\n<li><a title=\"PWR - Reator de \u00e1gua pressurizada\" href=\"https:\/\/www.nuclear-power.com\/pwr-pressurized-water-reactor\/\"><span>PWR &#8211; Reatores de \u00e1gua pressurizada<\/span><\/a>\n<ul>\n<li><span>Em\u00a0<\/span><strong><span>PWRs<\/span><\/strong><span>\u00a0em\u00a0<\/span><strong><span>opera\u00e7\u00e3o normal,<\/span><\/strong><span>\u00a0o fluxo \u00e9 considerado monof\u00e1sico.\u00a0Por\u00e9m, muitos estudos foram realizados sobre a natureza do\u00a0<\/span><strong><span>fluxo bif\u00e1sico<\/span><\/strong><span>\u00a0em caso de\u00a0<\/span><strong><span>transientes e acidentes<\/span><\/strong><span>\u00a0(como o\u00a0<strong>acidente<\/strong>\u00a0com\u00a0<\/span><strong><span>perda de l\u00edquido refrigerante &#8211; LOCA ou disparo de RCPs<\/span><\/strong><span>\u00a0), que s\u00e3o importantes para a seguran\u00e7a do reator e deve ser comprovado e declarado no\u00a0<\/span><strong><span>Relat\u00f3rio de An\u00e1lise de Seguran\u00e7a<\/span><\/strong><span>\u00a0(SAR).\u00a0No caso de PWRs, o fen\u00f4meno problem\u00e1tico n\u00e3o \u00e9 a seca.\u00a0No caso de PWRs, o fluxo cr\u00edtico \u00e9 o\u00a0<\/span><strong><span>fluxo anular invertido<\/span><\/strong><span>\u00a0.\u00a0Esse fluxo ocorre quando uma superf\u00edcie de revestimento da barra de combust\u00edvel \u00e9 superaquecida, o que causa a forma\u00e7\u00e3o de uma\u00a0<\/span><strong><span>camada de vapor local<\/span><\/strong><span>, causando uma redu\u00e7\u00e3o dr\u00e1stica na capacidade de transfer\u00eancia de calor.\u00a0Esse fen\u00f4meno \u00e9 conhecido como\u00a0<\/span><strong><span>afastamento da ebuli\u00e7\u00e3o nucleada &#8211; DNB<\/span><\/strong><span>\u00a0.\u00a0A diferen\u00e7a no regime de fluxo entre o fluxo p\u00f3s-secagem e o fluxo p\u00f3s-DNB \u00e9 mostrada na figura.<\/span><\/li>\n<li><span>Nos PWRs, a evapora\u00e7\u00e3o ocorre tamb\u00e9m em geradores de vapor.\u00a0Geradores de vapor s\u00e3o\u00a0<\/span><strong><span>trocadores de calor<\/span><\/strong><span>\u00a0usados \u200b\u200bpara converter\u00a0<\/span><strong><span>\u00e1gua de alimenta\u00e7\u00e3o em vapor a<\/span><\/strong><span>\u00a0partir do calor produzido no\u00a0<\/span><a href=\"https:\/\/www.reactor-physics.com\/what-is-reactor-core-definition\/\"><span>n\u00facleo de<\/span><\/a><span>\u00a0um\u00a0<a href=\"https:\/\/www.reactor-physics.com\/what-is-reactor-core-definition\/\">reator nuclear<\/a>\u00a0.\u00a0O vapor produzido aciona a turbina.<\/span><\/li>\n<\/ul>\n<\/li>\n<\/ul>\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-divider su-divider-style-dotted\"><\/div>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/convective-evaporation-horizontal-channel-fig.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-14855 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/convective-evaporation-horizontal-channel-fig.png\" alt=\"evapora\u00e7\u00e3o por convec\u00e7\u00e3o - canal horizontal\" width=\"587\" height=\"226\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/convective-evaporation-horizontal-channel-fig.png\" \/><\/a><\/div>\n<\/div>\n<div class=\"inside-grid-column\">\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<\/div>\n<\/div>\n<div class=\"lgc-column lgc-grid-parent lgc-grid-50 lgc-tablet-grid-50 lgc-mobile-grid-100 lgc-equal-heights lgc-first\">\n<div tabindex=\"0\" role=\"button\">\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","protected":false},"excerpt":{"rendered":"<p>As estruturas de fluxo observadas s\u00e3o definidas como padr\u00f5es de fluxo bif\u00e1sicos e possuem caracter\u00edsticas de identifica\u00e7\u00e3o particulares.\u00a0Padr\u00f5es de fluxo &#8211; fluxo bif\u00e1sico Padr\u00f5es de fluxo &#8211; fluxo bif\u00e1sico Um dos aspectos mais desafiadores de lidar com o\u00a0fluxo bif\u00e1sico\u00a0ou multif\u00e1sico\u00a0\u00e9 o fato de que ele pode assumir\u00a0muitas formas diferentes\u00a0.\u00a0As distribui\u00e7\u00f5es espaciais e as velocidades\u00a0das\u00a0fases l\u00edquida &#8230; <a title=\"O que \u00e9 padr\u00e3o de fluxo &#8211; fluxo bif\u00e1sico &#8211; defini\u00e7\u00e3o\" class=\"read-more\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-padrao-de-fluxo-fluxo-bifasico-definicao\/\" aria-label=\"More on O que \u00e9 padr\u00e3o de fluxo &#8211; fluxo bif\u00e1sico &#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 padr\u00e3o de fluxo - fluxo bif\u00e1sico - defini\u00e7\u00e3o<\/title>\n<meta name=\"description\" content=\"As estruturas de fluxo observadas s\u00e3o definidas como padr\u00f5es de fluxo bif\u00e1sicos e possuem caracter\u00edsticas de identifica\u00e7\u00e3o particulares. 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