{"id":47292,"date":"2019-11-03T22:23:08","date_gmt":"2019-11-03T21:23:08","guid":{"rendered":"https:\/\/www.thermal-engineering.org\/o-que-e-ebulicao-por-fluxo-ebulicao-por-conveccao-forcada-definicao\/"},"modified":"2020-01-23T10:29:35","modified_gmt":"2020-01-23T09:29:35","slug":"o-que-e-ebulicao-por-fluxo-ebulicao-por-conveccao-forcada-definicao","status":"publish","type":"post","link":"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-ebulicao-por-fluxo-ebulicao-por-conveccao-forcada-definicao\/","title":{"rendered":"O que \u00e9 ebuli\u00e7\u00e3o por fluxo &#8211; ebuli\u00e7\u00e3o por convec\u00e7\u00e3o for\u00e7ada &#8211; Defini\u00e7\u00e3o"},"content":{"rendered":"<div class=\"su-quote su-quote-style-default\">\n<div class=\"su-quote-inner su-clearfix\">Na ebuli\u00e7\u00e3o do fluxo (ou ebuli\u00e7\u00e3o por convec\u00e7\u00e3o for\u00e7ada), o fluxo de fluido \u00e9 for\u00e7ado sobre uma superf\u00edcie por meios externos, como uma bomba, bem como por efeitos de flutuabilidade.\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>Ebuli\u00e7\u00e3o por fluxo &#8211; fervura por convec\u00e7\u00e3o for\u00e7ada<\/h2>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Flow-Boiling-Boiling-Modes.png\"><img loading=\"lazy\" class=\"alignright size-medium wp-image-20784 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Flow-Boiling-Boiling-Modes-117x300.png\" alt=\"Ebuli\u00e7\u00e3o do fluxo - modos de ebuli\u00e7\u00e3o\" width=\"117\" height=\"300\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Flow-Boiling-Boiling-Modes-117x300.png\" \/><\/a>Na\u00a0<strong>ebuli\u00e7\u00e3o do fluxo<\/strong>\u00a0(ou ebuli\u00e7\u00e3o por convec\u00e7\u00e3o for\u00e7ada), o fluxo de fluido \u00e9 for\u00e7ado sobre uma superf\u00edcie por meios externos, como uma bomba, bem como por efeitos de flutuabilidade.\u00a0Portanto, a\u00a0<strong>ebuli\u00e7\u00e3o do fluxo<\/strong>\u00a0\u00e9 sempre acompanhada por outros efeitos de convec\u00e7\u00e3o.\u00a0As condi\u00e7\u00f5es dependem fortemente da geometria, que pode envolver fluxo externo sobre placas e cilindros aquecidos ou fluxo interno (duto).\u00a0Nos reatores nucleares, a maioria dos regimes de ebuli\u00e7\u00e3o \u00e9 apenas\u00a0<strong>fervura de convec\u00e7\u00e3o for\u00e7ada<\/strong>\u00a0.\u00a0A ebuli\u00e7\u00e3o do fluxo tamb\u00e9m \u00e9 classificada como ebuli\u00e7\u00e3o externa e interna, dependendo de o fluido ser for\u00e7ado a fluir sobre uma superf\u00edcie aquecida ou dentro de um canal aquecido.<\/p>\n<p>A ebuli\u00e7\u00e3o do fluxo interno \u00e9 muito mais complicada por natureza do que a ebuli\u00e7\u00e3o do fluxo externo, porque n\u00e3o h\u00e1 superf\u00edcie livre para o vapor escapar e, portanto, o l\u00edquido e o vapor s\u00e3o for\u00e7ados a fluir juntos.\u00a0O\u00a0<a title=\"Fluxo de fluido bif\u00e1sico\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-fluxo-de-fluido-bifasico-definicao\/\"><strong>fluxo de duas fases<\/strong><\/a>\u00a0em um tubo exibe diferentes regimes de ebuli\u00e7\u00e3o do fluxo, dependendo das quantidades relativas das fases l\u00edquida e de vapor.\u00a0Portanto, a ebuli\u00e7\u00e3o por convec\u00e7\u00e3o for\u00e7ada interna \u00e9 comumente referida como\u00a0<strong>fluxo bif\u00e1sico<\/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\"><span>Todos os problemas de fluxo de duas fases t\u00eam caracter\u00edsticas que s\u00e3o caracteristicamente diferentes daquelas encontradas em problemas de fase \u00fanica.<\/span><\/p>\n<ul>\n<li><span>No caso de vapor e \u00e1gua l\u00edquida, a\u00a0<\/span><strong><span>densidade<\/span><\/strong><span>\u00a0das duas fases\u00a0<\/span><strong><span>difere por um fator de cerca de 1000<\/span><\/strong><span>\u00a0.\u00a0Portanto, a influ\u00eancia da for\u00e7a do corpo gravitacional nos fluxos multif\u00e1sicos \u00e9 de muito maior import\u00e2ncia do que no caso dos fluxos monof\u00e1sicos.<\/span><\/li>\n<li><span>A\u00a0<\/span><strong><span>velocidade do som<\/span><\/strong><span>\u00a0muda drasticamente para materiais submetidos a mudan\u00e7as de fase e pode ter ordens de magnitude diferentes.\u00a0Isso influencia significativamente um\u00a0<\/span><strong><span>fluxo atrav\u00e9s de um orif\u00edcio<\/span><\/strong><span>\u00a0.<\/span><\/li>\n<li><span>A\u00a0<\/span><strong><span>concentra\u00e7\u00e3o<\/span><\/strong><span>\u00a0relativa\u00a0de diferentes fases \u00e9 geralmente um par\u00e2metro dependente de grande import\u00e2ncia nos fluxos multif\u00e1sicos, enquanto \u00e9 um par\u00e2metro sem conseq\u00fc\u00eancia nos fluxos monof\u00e1sicos.<\/span><\/li>\n<li><span>A mudan\u00e7a de fase significa que as quedas de press\u00e3o induzidas pelo fluxo podem causar altera\u00e7\u00f5es de fase adicionais (por exemplo, a \u00e1gua pode evaporar atrav\u00e9s de um orif\u00edcio), aumentando o volume relativo do meio gasoso, compress\u00edvel e aumentando as velocidades de efluxo, diferentemente do fluxo incompress\u00edvel monof\u00e1sico, em que a diminui\u00e7\u00e3o de um orif\u00edcio diminuiria a velocidade do efluxo.<\/span><\/li>\n<li><span>A distribui\u00e7\u00e3o espacial das v\u00e1rias fases no canal de fluxo afeta fortemente o comportamento do fluxo.<\/span><\/li>\n<li><span>Existem muitos tipos de instabilidades no fluxo multif\u00e1sico.<\/span><\/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-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<\/div>\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>Ebuli\u00e7\u00e3o do fluxo &#8211; canal vertical<\/span><\/h2>\n<p><span>Neste cap\u00edtulo, estudaremos o\u00a0<\/span><strong><span>fluxo de ebuli\u00e7\u00e3o<\/span><\/strong><span>\u00a0em um canal vertical de um\u00a0<\/span><a title=\"BWR - Reator de \u00e1gua fervente\" href=\"https:\/\/www.nuclear-power.com\/bwr-boiling-water-reactor\/\"><strong><span>reator de \u00e1gua fervente<\/span><\/strong><\/a><span>\u00a0.\u00a0Os regimes de ebuli\u00e7\u00e3o e a curva de fluxo de calor s\u00e3o semelhantes aos da ebuli\u00e7\u00e3o da piscina.\u00a0O processo ocorre tamb\u00e9m em caldeiras modernas de circula\u00e7\u00e3o for\u00e7ada de alta press\u00e3o.<\/span><\/p>\n<p><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(\u00a0<\/span><strong><span>CHF &#8211; fluxo de calor cr\u00edtico<\/span><\/strong><span>\u00a0), 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>.\u00a0Na regi\u00e3o de alta qualidade, a crise ocorre com um fluxo de calor menor.\u00a0Como a velocidade de fluxo no n\u00facleo de vapor \u00e9 alta, a transfer\u00eancia de calor p\u00f3s-CHF \u00e9 muito melhor do que no fluxo cr\u00edtico de baixa qualidade (ou seja, para PWRs, os aumentos de temperatura s\u00e3o maiores e mais r\u00e1pidos).<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Flow-Boiling-Dryout.png\"><img loading=\"lazy\" class=\"alignright size-medium wp-image-20773 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Flow-Boiling-Dryout-257x300.png\" alt=\"Ebuli\u00e7\u00e3o do fluxo - secagem\" width=\"257\" height=\"300\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Flow-Boiling-Dryout-257x300.png\" \/><\/a><span>Os\u00a0modos\u00a0t\u00edpicos de\u00a0<\/span><strong><span>ebuli\u00e7\u00e3o do fluxo<\/span><\/strong><span>\u00a0em um\u00a0<\/span><strong><span>canal vertical<\/span><\/strong><span>\u00a0s\u00e3o representados na figura.\u00a0Esta figura mostra a ordem t\u00edpica dos regimes de fluxo que s\u00e3o encontrados desde a entrada at\u00e9 a sa\u00edda de um\u00a0<\/span><strong><span>canal aquecido<\/span><\/strong><span>\u00a0.\u00a0Na entrada, o\u00a0<\/span><strong><span>l\u00edquido entra no sub-resfriado<\/span><\/strong><span>\u00a0(na temperatura mais baixa que a satura\u00e7\u00e3o).\u00a0Nesta regi\u00e3o, o fluxo \u00e9 monof\u00e1sico.\u00a0\u00c0 medida que o l\u00edquido esquenta, a temperatura da parede aumenta correspondentemente.\u00a0\u00c0 medida que a\u00a0<\/span><strong><span>temperatura<\/span><\/strong><span>\u00a0da\u00a0<strong>parede excede a temperatura de satura\u00e7\u00e3o<\/strong>\u00a0(por exemplo, 285 \u00b0 C a 6,8 MPa),\u00a0<\/span><strong><span>come\u00e7a a ebuli\u00e7\u00e3o do nucleado sub-resfriado<\/span><\/strong><span>\u00a0.\u00a0As bolhas nucleadas na\u00a0<\/span><a href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-camada-de-limite-definicao\/\"><span>camada limite<\/span><\/a><span>\u00a0t\u00e9rmica superaquecida\u00a0na parede aquecida, mas tendem a\u00a0<\/span><strong><span>condensar-se no volume sub-resfriado<\/span><\/strong><span>\u00a0.<\/span><\/p>\n<p><span>Um aumento adicional na temperatura do l\u00edquido causa que o volume do l\u00edquido atinja a\u00a0<\/span><strong><span>temperatura de satura\u00e7\u00e3o<\/span><\/strong><span>\u00a0e o processo de ebuli\u00e7\u00e3o por convec\u00e7\u00e3o passe pelo\u00a0<\/span><a title=\"Fluxo borbulhante - Fluxo bif\u00e1sico\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/two-phase-fluid-flow\/bubbly-flow-two-phase-flow\/\"><strong><span>fluxo borbulhante<\/span><\/strong><\/a><span>\u00a0para o\u00a0<\/span><a title=\"Fluxo de encaixe - Fluxo de lesma\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/two-phase-fluid-flow\/plug-flow-slug-flow\/\"><strong><span>fluxo<\/span><\/strong><\/a><span>\u00a0da\u00a0<a title=\"Fluxo de encaixe - Fluxo de lesma\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/two-phase-fluid-flow\/plug-flow-slug-flow\/\"><strong>lesma<\/strong><\/a>\u00a0.\u00a0O aumento da\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 vazios<\/span><\/a><span>\u00a0faz com que a estrutura do fluxo se torne inst\u00e1vel.\u00a0O processo de ebuli\u00e7\u00e3o passa atrav\u00e9s do\u00a0<strong><a title=\"Fluxo de rotatividade - Fluxo de espuma\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/two-phase-fluid-flow\/churn-flow-froth-flow\/\">fluxo de<\/a><\/strong><\/span><strong><span>\u00a0lesma e\u00a0<\/span><a title=\"Fluxo de rotatividade - Fluxo de espuma\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/two-phase-fluid-flow\/churn-flow-froth-flow\/\"><span>rotatividade<\/span><\/a><\/strong><span>\u00a0para o\u00a0<\/span><a title=\"Fluxo anular - Fluxo bif\u00e1sico\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/two-phase-fluid-flow\/annular-flow-two-phase-flow\/\"><strong><span>regime de fluxo anular<\/span><\/strong><\/a><span>\u00a0com sua pel\u00edcula anular caracter\u00edstica do l\u00edquido.\u00a0Em determinadas combina\u00e7\u00f5es de taxa de fluxo atrav\u00e9s de um canal, press\u00e3o, qualidade de fluxo e taxa de calor linear, o\u00a0<\/span><strong><span>filme l\u00edquido<\/span><\/strong><span>\u00a0da parede\u00a0<strong>pode esgotar-se<\/strong>\u00a0e a parede pode ser\u00a0<\/span><strong><span>seca<\/span><\/strong><span>.\u00a0No ponto de secagem, a temperatura da parede aumenta significativamente para dissipar o fluxo de calor aplicado.\u00a0O fluxo p\u00f3s-secagem (fluxo de\u00a0<\/span><a title=\"Fluxo de N\u00e9voa\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/two-phase-fluid-flow\/mist-flow\/\"><span>n\u00e9voa ou queda<\/span><\/a><span>\u00a0) no canal aquecido \u00e9 indesej\u00e1vel, porque a presen\u00e7a desse regime de fluxo \u00e9 acompanhada de temperaturas da parede significativamente mais altas e alta flutua\u00e7\u00e3o das temperaturas da parede.\u00a0As correla\u00e7\u00f5es usadas para determinar os coeficientes de transfer\u00eancia de calor no fluxo bif\u00e1sico s\u00e3o descritas abaixo.<\/span><\/p>\n<p><span>Refer\u00eancia especial: Tong, LS, Weisman, Joel.\u00a0An\u00e1lise T\u00e9rmica de Reatores de \u00c1gua Pressurizada.\u00a0Amer Nuclear Society, 3a edi\u00e7\u00e3o, 5\/1996.\u00a0ISBN-13: 978-0894480386.<\/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>Convec\u00e7\u00e3o For\u00e7ada Monof\u00e1sica &#8211; Correla\u00e7\u00e3o de Transfer\u00eancia de Calor<\/span><\/h2>\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><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>equa\u00e7\u00e3o de Dittus-Boelter<\/span><\/strong><\/a><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?5a260f\"><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?5a260f\" 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?5a260f\" \/><\/a><\/p>\n<p><span>A\u00a0\u00a0<\/span><strong><span>correla\u00e7\u00e3o de Dittus-Boelter<\/span><\/strong><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>Correla\u00e7\u00f5es de ebuli\u00e7\u00e3o de nucleados &#8211; ebuli\u00e7\u00e3o por fluxo<\/span><\/h2>\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>Correla\u00e7\u00e3o de McAdams<\/span><\/h2>\n<p><span>Na ebuli\u00e7\u00e3o de nucleados totalmente desenvolvida com refrigerante saturado, a temperatura da parede \u00e9 determinada pelo fluxo de calor e press\u00e3o locais e depende apenas ligeiramente do\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.\u00a0Para \u00e1gua sub-resfriada a press\u00f5es absolutas entre 0,1 &#8211; 0,6 MPa, a\u00a0<\/span><strong><span>correla\u00e7\u00e3o de McAdams<\/span><\/strong><span>\u00a0fornece:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/nucleate-boiling-McAdams-Correlation.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20789 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/nucleate-boiling-McAdams-Correlation.png\" alt=\"ebuli\u00e7\u00e3o nucleada - Correla\u00e7\u00e3o de McAdams\" width=\"453\" height=\"86\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/nucleate-boiling-McAdams-Correlation.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>Correla\u00e7\u00e3o de Thom<\/span><\/h2>\n<p><span>A\u00a0<\/span><strong><span>correla\u00e7\u00e3o de Thom<\/span><\/strong><span>\u00a0\u00e9 para a ebuli\u00e7\u00e3o do fluxo (sub-resfriado ou saturado a press\u00f5es de at\u00e9 cerca de 20 MPa) sob condi\u00e7\u00f5es em que a contribui\u00e7\u00e3o da ebuli\u00e7\u00e3o nucleada predomina sobre a convec\u00e7\u00e3o for\u00e7ada.\u00a0Essa correla\u00e7\u00e3o \u00e9 \u00fatil para a estimativa aproximada da diferen\u00e7a de temperatura esperada, dado o fluxo de calor:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/nucleate-boiling-Thom-Correlation.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20790 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/nucleate-boiling-Thom-Correlation.png\" alt=\"ebuli\u00e7\u00e3o de nucleados - Correla\u00e7\u00e3o de Thom\" width=\"377\" height=\"147\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/nucleate-boiling-Thom-Correlation.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>Correla\u00e7\u00e3o de Chen<\/span><\/h2>\n<p><span>Em 1963,\u00a0<\/span><strong><span>Chen<\/span><\/strong><span>\u00a0prop\u00f4s a primeira correla\u00e7\u00e3o de ebuli\u00e7\u00e3o do fluxo para a evapora\u00e7\u00e3o em tubos verticais, a fim de obter amplo uso.\u00a0<\/span><strong><span>A correla\u00e7\u00e3o de Chen<\/span><\/strong><span>\u00a0inclui os\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\/\"><span>coeficientes de transfer\u00eancia de calor<\/span><\/a><span>\u00a0devido \u00e0\u00a0<\/span><strong><span>ebuli\u00e7\u00e3o dos nucleados<\/span><\/strong><span>\u00a0, bem como os\u00a0<\/span><strong><span>mecanismos convectivos for\u00e7ados<\/span><\/strong><span>.\u00a0Deve-se notar que, em fra\u00e7\u00f5es de vapor mais altas, o coeficiente de transfer\u00eancia de calor varia fortemente com a vaz\u00e3o.\u00a0A velocidade do fluxo em um n\u00facleo pode ser muito alta, causando turbul\u00eancias muito altas.\u00a0Esse mecanismo de transfer\u00eancia de calor foi referido como &#8220;evapora\u00e7\u00e3o for\u00e7ada por convec\u00e7\u00e3o&#8221;.\u00a0Nenhum crit\u00e9rio adequado foi estabelecido para determinar a transi\u00e7\u00e3o da ebuli\u00e7\u00e3o nucleada para a vaporiza\u00e7\u00e3o por convec\u00e7\u00e3o for\u00e7ada.\u00a0No entanto, Chen desenvolveu uma correla\u00e7\u00e3o \u00fanica v\u00e1lida para a ebuli\u00e7\u00e3o nucleada e a vaporiza\u00e7\u00e3o por convec\u00e7\u00e3o for\u00e7ada, para condi\u00e7\u00f5es de ebuli\u00e7\u00e3o saturada e estendida para incluir a ebuli\u00e7\u00e3o sub-resfriada por outros.\u00a0Chen prop\u00f4s uma correla\u00e7\u00e3o em que o coeficiente de transfer\u00eancia de calor \u00e9 a\u00a0<\/span><strong><span>soma<\/span><\/strong><span>\u00a0de um\u00a0componente de\u00a0<\/span><strong><span>convec\u00e7\u00e3o for\u00e7ada<\/span><\/strong><span>\u00a0e uma\u00a0<\/span><strong><span>ebuli\u00e7\u00e3o nucleada<\/span><\/strong><span>componente.\u00a0Deve-se observar que a correla\u00e7\u00e3o de ebuli\u00e7\u00e3o de nucleados de Forster e Zuber (1955) \u00e9 usada para calcular o coeficiente de transfer\u00eancia de calor em ebuli\u00e7\u00e3o de nucleados, h\u00a0<\/span><sub><span>FZ<\/span><\/sub><span>\u00a0e a correla\u00e7\u00e3o de fluxo turbulento de Dittus-Boelter (1930) \u00e9 usada para calcular a fase l\u00edquida coeficiente de transfer\u00eancia de calor por convec\u00e7\u00e3o, h\u00a0<\/span><sub><span>l<\/span><\/sub><span>\u00a0.<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Chens-Correlation-Forster-Zuber-and-Dittus-Boelter.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20774 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Chens-Correlation-Forster-Zuber-and-Dittus-Boelter.png\" alt=\"Correla\u00e7\u00e3o de Chens - Forster-Zuber\" width=\"720\" height=\"669\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Chens-Correlation-Forster-Zuber-and-Dittus-Boelter.png\" \/><\/a><\/p>\n<p><span>O fator de supress\u00e3o de ebuli\u00e7\u00e3o dos nucleados, S, \u00e9 a raz\u00e3o entre o superaquecimento efetivo e o superaquecimento da parede.\u00a0\u00c9 respons\u00e1vel pela diminui\u00e7\u00e3o da transfer\u00eancia de calor em ebuli\u00e7\u00e3o porque o superaquecimento efetivo na camada limite \u00e9 menor que o superaquecimento com base na temperatura da parede.\u00a0O multiplicador bif\u00e1sico, F, \u00e9 uma fun\u00e7\u00e3o do par\u00e2metro Martinelli \u03c7\u00a0<\/span><sub><span>tt<\/span><\/sub><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>Crise de ebuli\u00e7\u00e3o &#8211; Fluxo cr\u00edtico de calor<\/span><\/h2>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Dryout-DNB-min.png\"><img loading=\"lazy\" class=\"alignright size-medium wp-image-14862 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Dryout-DNB-min-225x300.png\" alt=\"Dryout vs. DNB\" width=\"225\" height=\"300\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Dryout-DNB-min-225x300.png\" \/><\/a><span>Como foi escrito, nos\u00a0<\/span><a href=\"https:\/\/www.nuclear-power.com\/nuclear-power-plant\/nuclear-reactor\/\"><span>reatores nucleares<\/span><\/a><span>\u00a0, as limita\u00e7\u00f5es do\u00a0<\/span><strong><span>fluxo de calor local<\/span><\/strong><span>\u00a0s\u00e3o da maior import\u00e2ncia para a seguran\u00e7a do reator.\u00a0Para\u00a0<\/span><a href=\"https:\/\/www.nuclear-power.com\/pwr-pressurized-water-reactor\/\"><span>reatores de \u00e1gua pressurizada<\/span><\/a><span>\u00a0e tamb\u00e9m para\u00a0<\/span><a href=\"https:\/\/www.nuclear-power.com\/bwr-boiling-water-reactor\/\"><span>reatores de \u00e1gua fervente<\/span><\/a><span>\u00a0, existem fen\u00f4menos termo-hidr\u00e1ulicos, que causam uma diminui\u00e7\u00e3o repentina na\u00a0<\/span><strong><span>efici\u00eancia da transfer\u00eancia de calor<\/span><\/strong><span>\u00a0(mais precisamente no\u00a0<\/span><strong><span>coeficiente de transfer\u00eancia de calor<\/span><\/strong><span>\u00a0).\u00a0Esses fen\u00f4menos ocorrem com certo valor do fluxo de calor, conhecido como &#8221;\u00a0<\/span><strong><span>fluxo cr\u00edtico de calor<\/span><\/strong><span>\u00a0&#8220;.\u00a0Os fen\u00f4menos que causam a deteriora\u00e7\u00e3o da transfer\u00eancia de calor s\u00e3o diferentes para PWRs e BWRs.<\/span><\/p>\n<p><span>Nos dois tipos de reatores, o problema est\u00e1 mais ou menos associado \u00e0 sa\u00edda da ebuli\u00e7\u00e3o nucleada.\u00a0O fluxo de calor em ebuli\u00e7\u00e3o nucleado n\u00e3o pode ser aumentado indefinidamente.\u00a0Em algum valor, chamamos de \u201c\u00a0<\/span><strong><span>fluxo cr\u00edtico de calor<\/span><\/strong><span>\u00a0\u201d (\u00a0<\/span><strong><span>CHF<\/span><\/strong><span>\u00a0), o vapor produzido pode formar uma camada isolante sobre a superf\u00edcie, que por sua vez deteriora o coeficiente de transfer\u00eancia de calor.\u00a0Imediatamente ap\u00f3s o fluxo cr\u00edtico de calor ter sido atingido, a ebuli\u00e7\u00e3o se torna inst\u00e1vel e a ebuli\u00e7\u00e3o de pel\u00edcula ocorre.\u00a0A transi\u00e7\u00e3o da ebuli\u00e7\u00e3o nucleada para a ebuli\u00e7\u00e3o de pel\u00edcula \u00e9 conhecida como &#8221;\u00a0<\/span><strong><span>crise de ebuli\u00e7\u00e3o<\/span><\/strong><span>\u00a0&#8220;.\u00a0Como foi escrito, os fen\u00f4menos que causam a deteriora\u00e7\u00e3o da transfer\u00eancia de calor s\u00e3o diferentes para PWRs e BWRs.<\/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>Partida da Ebuli\u00e7\u00e3o Nucleada &#8211; DNB<\/span><\/h2>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/DNBR-Departure-from-Nucleate-Boiling-Ratio.png\"><img loading=\"lazy\" class=\"alignright size-medium wp-image-20775 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/DNBR-Departure-from-Nucleate-Boiling-Ratio-289x300.png\" alt=\"DNBR - Partida da Raz\u00e3o de Ebuli\u00e7\u00e3o Nucleada\" width=\"289\" height=\"300\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/DNBR-Departure-from-Nucleate-Boiling-Ratio-289x300.png\" \/><\/a><span>No caso de\u00a0<\/span><a href=\"https:\/\/www.nuclear-power.com\/pwr-pressurized-water-reactor\/\"><span>PWRs<\/span><\/a><span>\u00a0, a quest\u00e3o cr\u00edtica de seguran\u00e7a \u00e9 denominada\u00a0<\/span><strong><span>DNB<\/span><\/strong><span>\u00a0(\u00a0<\/span><strong><span>partida da ebuli\u00e7\u00e3o nucleada<\/span><\/strong><span>\u00a0), que causa a forma\u00e7\u00e3o de uma\u00a0<\/span><strong><span>camada de vapor local<\/span><\/strong><span>\u00a0, causando uma redu\u00e7\u00e3o dr\u00e1stica na capacidade de transfer\u00eancia de calor.\u00a0Esse fen\u00f4meno ocorre na regi\u00e3o sub-resfriada ou de baixa qualidade.\u00a0O comportamento da crise de ebuli\u00e7\u00e3o depende de muitas condi\u00e7\u00f5es de fluxo (press\u00e3o, temperatura, taxa de fluxo), mas a crise de ebuli\u00e7\u00e3o ocorre em fluxos de calor relativamente altos e parece estar associado \u00e0 nuvem de bolhas adjacentes \u00e0 superf\u00edcie.\u00a0Essas bolhas ou filme de vapor reduzem a quantidade de \u00e1gua que entra.\u00a0Como esse fen\u00f4meno deteriora o coeficiente de transfer\u00eancia de calor e o fluxo de calor permanece, o calor\u00a0<\/span><strong><span>acumula-se<\/span><\/strong><span>na barra de combust\u00edvel, causando\u00a0<\/span><strong><span>aumento dram\u00e1tico<\/span><\/strong><span>\u00a0do revestimento e da\u00a0<\/span><strong><span>temperatura do<\/span><\/strong><span>\u00a0combust\u00edvel\u00a0.\u00a0Simplesmente, \u00e9 necess\u00e1ria uma diferen\u00e7a de temperatura muito alta para transferir o fluxo de calor cr\u00edtico produzido da superf\u00edcie da barra de combust\u00edvel para o l\u00edquido de arrefecimento do reator (atrav\u00e9s da camada de vapor).<\/span><\/p>\n<p><span>No caso de PWRs, o fluxo cr\u00edtico \u00e9 um fluxo\u00a0<\/span><strong><span>anular invertido<\/span><\/strong><span>\u00a0, enquanto que nos BWRs, o fluxo cr\u00edtico \u00e9 geralmente um fluxo anular.\u00a0A diferen\u00e7a no regime de fluxo entre o fluxo p\u00f3s-secagem e o fluxo p\u00f3s-DNB \u00e9 mostrada na figura.\u00a0Em\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).<\/span><\/p>\n<p><span>Nos reatores de \u00e1gua pressurizada, um dos principais requisitos de seguran\u00e7a \u00e9 que a sa\u00edda da ebuli\u00e7\u00e3o nucleada (DNB) n\u00e3o ocorrer\u00e1 durante a opera\u00e7\u00e3o em estado estacion\u00e1rio, transientes operacionais normais e ocorr\u00eancias operacionais previstas (AOOs).\u00a0A integridade do revestimento de combust\u00edvel ser\u00e1 mantida se o DNBR m\u00ednimo permanecer acima do limite de 95\/95 DNBR para PWRs (uma probabilidade de 95% a um n\u00edvel de confian\u00e7a de 95%).\u00a0O crit\u00e9rio DNB \u00e9 um dos crit\u00e9rios de aceita\u00e7\u00e3o nas an\u00e1lises de seguran\u00e7a, al\u00e9m de constituir um dos limites de seguran\u00e7a nas especifica\u00e7\u00f5es t\u00e9cnicas.<\/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 de calor cr\u00edtico para DNB &#8211; correla\u00e7\u00f5es<\/span><\/h2>\n<p><span>Como foi escrito, a\u00a0<\/span><strong><span>crise de ebuli\u00e7\u00e3o<\/span><\/strong><span>\u00a0pode ser classificada como\u00a0<\/span><strong><span>seca<\/span><\/strong><span>\u00a0(ser\u00e1 descrita abaixo DNB) na regi\u00e3o de alta qualidade e\u00a0<\/span><strong><span>sa\u00edda da ebuli\u00e7\u00e3o nucleada (DNB)<\/span><\/strong><span>\u00a0na regi\u00e3o sub-resfriada ou de baixa qualidade (faixa aproximada de qualidade: de \u20135% para + 5%).\u00a0Mas o\u00a0<\/span><strong><span>fluxo de calor cr\u00edtico<\/span><\/strong><span>\u00a0\u00e9 usado para ambos os regimes.<\/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>DNB &#8211; Correla\u00e7\u00e3o W-3<\/span><\/h2>\n<p><span>Uma das correla\u00e7\u00f5es de projeto mais conhecidas para prever a\u00a0<\/span><strong><span>sa\u00edda da ebuli\u00e7\u00e3o nucleada<\/span><\/strong><span>\u00a0\u00e9 a\u00a0<\/span><strong><span>correla\u00e7\u00e3o W-3<\/span><\/strong><span>\u00a0desenvolvida na\u00a0<\/span><strong><span>Divis\u00e3o de Energia At\u00f4mica de Westinghouse por Tong<\/span><\/strong><span>\u00a0.\u00a0\u00c9 aplic\u00e1vel a fluxos de qualidade sub-resfriados e de baixa a moderada\u00a0<\/span><strong><span>. A correla\u00e7\u00e3o W-3<\/span><\/strong><span>\u00a0\u00e9 uma fun\u00e7\u00e3o da\u00a0<\/span><a title=\"O que \u00e9 entalpia\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/what-is-energy-physics\/what-is-enthalpy\/\"><span>entalpia<\/span><\/a><span>\u00a0do refrigerante\u00a0(saturada e entrada),\u00a0<\/span><a title=\"O que \u00e9 press\u00e3o - F\u00edsica\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/thermodynamic-properties\/what-is-pressure-physics\/\"><span>press\u00e3o<\/span><\/a><span>\u00a0,\u00a0<\/span><a title=\"Qualidade de Vapor - Fra\u00e7\u00e3o de Secura\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/materials-nuclear-engineering\/properties-steam-what-is-steam\/vapor-quality-dryness-fraction\/\"><span>qualidade<\/span><\/a><span>\u00a0e fluxo de massa do refrigerante:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/CHF-Critical-Heat-Flux-Correlation.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20791 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/CHF-Critical-Heat-Flux-Correlation.png\" alt=\"CHF - Fluxo Cr\u00edtico de Calor - Correla\u00e7\u00e3o\" width=\"489\" height=\"46\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/CHF-Critical-Heat-Flux-Correlation.png\" \/><\/a><\/p>\n<p><span>A correla\u00e7\u00e3o W-3 \u00e9 para fluxo de calor cr\u00edtico em canais uniformemente aquecidos.\u00a0Para explicar os fluxos de calor n\u00e3o uniformes, Tong introduziu o fator de corre\u00e7\u00e3o F.<\/span><\/p>\n<p><span>Refer\u00eancia especial: Tong, LS, Weisman, Joel.\u00a0An\u00e1lise T\u00e9rmica de Reatores de \u00c1gua Pressurizada.\u00a0Amer Nuclear Society, 3a edi\u00e7\u00e3o, 5\/1996.\u00a0ISBN-13: 978-0894480386.<\/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>Fator de parede fria &#8211; CWF<\/span><\/h2>\n<p><span>Tong, LS e Weisman, Joel tamb\u00e9m introduzem um novo fator conhecido como \u201c\u00a0<\/span><strong><span>fator de parede fria<\/span><\/strong><span>\u00a0\u201d, que corrige o CHF em um canal que cont\u00e9m uma parede n\u00e3o aquecida (por exemplo, canal adjacente ao tubo guia da haste de controle).\u00a0Nesses canais, o filme l\u00edquido se acumula ao longo da parede fria e esse fluido n\u00e3o \u00e9 eficaz no resfriamento da superf\u00edcie aquecida e o fluido que resfria a superf\u00edcie aquecida est\u00e1 em entalpia mais alta do que o calculado sem a hip\u00f3tese de parede fria.\u00a0Observe que, existe uma suposi\u00e7\u00e3o de que a parede fria deteriora a transfer\u00eancia de calor em compara\u00e7\u00e3o com o canal com todos os lados aquecidos na\u00a0<\/span><strong><span>mesma entalpia de sa\u00edda em massa<\/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>Tabelas de consulta CHF<\/span><\/h2>\n<p><strong><span>As tabelas de consulta de CHF<\/span><\/strong><span>\u00a0s\u00e3o amplamente utilizadas para a previs\u00e3o do fluxo de calor cr\u00edtico (CHF).\u00a0A tabela de consulta do CHF \u00e9 basicamente um banco de dados normalizado para um tubo vertical de 8 mm refrigerado a \u00e1gua.\u00a0A tabela de consulta do CHF de 2006 \u00e9 baseada em um banco de dados contendo mais de 30.000 pontos de dados e abrange os intervalos de press\u00e3o de 0,1\u201321 Mpa, 0\u20138000 kg.m\u00a0<\/span><sup><span>\u20132<\/span><\/sup><span>\u00a0.s\u00a0<\/span><sup><span>-1<\/span><\/sup><span>\u00a0(fluxo zero refere-se \u00e0 fervura da piscina condi\u00e7\u00f5es) fluxo de massa e qualidade de vapor de -0,5 a 1 (qualidades negativas referem-se a condi\u00e7\u00f5es sub-resfriadas).<\/span><\/p>\n<p><span>Refer\u00eancia especial: GROENEVELD, DC et al., A tabela de consulta de 2006, Nuclear Engineering and Design 237 (2007), 1909\u20131922.<\/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>Partida da Raz\u00e3o de Ebuli\u00e7\u00e3o Nucleada &#8211; DNBR<\/span><\/h2>\n<p><span>Como foi escrito, no caso de\u00a0<\/span><a href=\"https:\/\/www.nuclear-power.com\/pwr-pressurized-water-reactor\/\"><span>PWRs<\/span><\/a><span>\u00a0, a quest\u00e3o cr\u00edtica de seguran\u00e7a \u00e9 denominada\u00a0<\/span><strong><span>DNB<\/span><\/strong><span>\u00a0(\u00a0<\/span><strong><span>partida da ebuli\u00e7\u00e3o nucleada<\/span><\/strong><span>\u00a0), que causa a forma\u00e7\u00e3o de uma\u00a0<\/span><strong><span>camada de vapor local<\/span><\/strong><span>\u00a0, causando uma redu\u00e7\u00e3o dr\u00e1stica na capacidade de transfer\u00eancia de calor.\u00a0Observe que, mesmo para BWRs, que t\u00eam um perfil de pot\u00eancia axial com um pico significativamente inferior, o risco DNB deve ser levado em considera\u00e7\u00e3o.<\/span><\/p>\n<p><span>DNB ocorre quando o fluxo de calor local atinge o valor do fluxo de calor cr\u00edtico.\u00a0Esse fen\u00f4meno ocorre na regi\u00e3o sub-resfriada ou de baixa qualidade (faixa aproximada de qualidade: de \u20135% a + 5%).\u00a0O comportamento desse tipo de crise de ebuli\u00e7\u00e3o depende de muitas condi\u00e7\u00f5es de fluxo (press\u00e3o, temperatura, taxa de fluxo), uma vez que o fluxo cr\u00edtico de calor geralmente \u00e9 uma fun\u00e7\u00e3o da\u00a0<\/span><a title=\"O que \u00e9 entalpia\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/what-is-energy-physics\/what-is-enthalpy\/\"><span>entalpia<\/span><\/a><span>\u00a0do refrigerante\u00a0\u00a0\u00a0(saturada e de entrada),\u00a0\u00a0<\/span><a title=\"O que \u00e9 press\u00e3o - F\u00edsica\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/thermodynamic-properties\/what-is-pressure-physics\/\"><span>press\u00e3o<\/span><\/a><span>\u00a0,\u00a0\u00a0<\/span><a title=\"Qualidade de Vapor - Fra\u00e7\u00e3o de Secura\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/materials-nuclear-engineering\/properties-steam-what-is-steam\/vapor-quality-dryness-fraction\/\"><span>qualidade<\/span><\/a><span>\u00a0\u00a0e fluxo de massa do refrigerante:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/CHF-Critical-Heat-Flux-Correlation.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20791 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/CHF-Critical-Heat-Flux-Correlation.png\" alt=\"CHF - Fluxo Cr\u00edtico de Calor - Correla\u00e7\u00e3o\" width=\"489\" height=\"46\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/CHF-Critical-Heat-Flux-Correlation.png\" \/><\/a><\/p>\n<p><span>Esse tipo de crise de ebuli\u00e7\u00e3o ocorre em fluxos de calor relativamente altos e parece estar associado \u00e0 nuvem de bolhas, adjacente \u00e0 superf\u00edcie.\u00a0Essas bolhas ou filme de vapor reduzem a quantidade de \u00e1gua que entra.\u00a0Como esse fen\u00f4meno deteriora o coeficiente de transfer\u00eancia de calor e o fluxo de calor permanece, o calor se\u00a0<\/span><strong><span>acumula<\/span><\/strong><span>\u00a0na barra de combust\u00edvel, causando\u00a0<\/span><strong><span>um aumento dram\u00e1tico<\/span><\/strong><span>\u00a0do revestimento e da\u00a0<\/span><strong><span>temperatura do<\/span><\/strong><span>\u00a0combust\u00edvel\u00a0.\u00a0Simplesmente, \u00e9 necess\u00e1ria uma diferen\u00e7a de temperatura muito alta para transferir o fluxo de calor cr\u00edtico produzido da superf\u00edcie da barra de combust\u00edvel para o l\u00edquido de arrefecimento do reator (atrav\u00e9s da camada de vapor).\u00a0No caso de PWRs, o fluxo cr\u00edtico \u00e9 um fluxo\u00a0<\/span><strong><span>anular invertido<\/span><\/strong><span>\u00a0, enquanto que nos BWRs, o fluxo cr\u00edtico \u00e9 geralmente um fluxo anular.<\/span><\/p>\n<p><span>Nos reatores de \u00e1gua pressurizada, um dos principais requisitos de seguran\u00e7a \u00e9 que a sa\u00edda da ebuli\u00e7\u00e3o nucleada (DNB) n\u00e3o ocorrer\u00e1 durante a opera\u00e7\u00e3o em estado estacion\u00e1rio, transientes operacionais normais e ocorr\u00eancias operacionais previstas (AOOs).\u00a0A integridade do revestimento de combust\u00edvel ser\u00e1 mantida se o\u00a0<\/span><strong><span>DNBR<\/span><\/strong><span>\u00a0m\u00ednimo\u00a0<strong>permanecer acima<\/strong>\u00a0do\u00a0<\/span><strong><span>limite de<\/span><\/strong><span>\u00a095\/95\u00a0<strong>DNBR<\/strong>\u00a0para PWRs (uma probabilidade de 95% a um n\u00edvel de confian\u00e7a de 95%).\u00a0O crit\u00e9rio DNB \u00e9 um dos crit\u00e9rios de aceita\u00e7\u00e3o nas an\u00e1lises de seguran\u00e7a, al\u00e9m de constituir um dos limites de seguran\u00e7a nas especifica\u00e7\u00f5es t\u00e9cnicas.\u00a0Desnecess\u00e1rio dizer que o estabelecimento de uma rela\u00e7\u00e3o DNB m\u00ednima fornece uma grande limita\u00e7\u00e3o no projeto de reatores refrigerados a \u00e1gua.\u00a0Esse fen\u00f4meno limita a pot\u00eancia t\u00e9rmica m\u00e1xima de cada PWR.<\/span><\/p>\n<p><strong><span>A rela\u00e7\u00e3o DNB (DNBR &#8211; Partida da taxa de ebuli\u00e7\u00e3o de nucleados)<\/span><\/strong><span>\u00a0\u00e9 a medida da margem para o fluxo de calor cr\u00edtico.\u00a0DNBR \u00e9 definido como:<\/span><\/p>\n<p><em><span>o fluxo de calor cr\u00edtico em um local espec\u00edfico e os par\u00e2metros espec\u00edficos do l\u00edquido de refrigera\u00e7\u00e3o divididos pelo fluxo de calor local em opera\u00e7\u00e3o nesse local<\/span><\/em><span>\u00a0.<\/span><\/p>\n<p><em><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/DNBR-definition.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20792 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/DNBR-definition.png\" alt=\"DNBR - defini\u00e7\u00e3o\" width=\"242\" height=\"82\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/DNBR-definition.png\" \/><\/a><\/em><\/p>\n<p><span>O n\u00facleo do reator deve ser projetado para manter o DNBR maior que o valor m\u00ednimo permitido (conhecido como limite de correla\u00e7\u00e3o) durante a opera\u00e7\u00e3o em estado estacion\u00e1rio, transit\u00f3rios operacionais normais e ocorr\u00eancias operacionais previstas (AOOs).\u00a0Para prever a sa\u00edda da ebuli\u00e7\u00e3o nucleada, o CHF pode ser, por exemplo, determinado usando a correla\u00e7\u00e3o W-3 desenvolvida na Divis\u00e3o de Energia At\u00f4mica de Westinghouse.\u00a0Se essas correla\u00e7\u00f5es fossem perfeitas (sem incertezas), o crit\u00e9rio seria simples:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/DNBR-criterion.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20793 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/DNBR-criterion.png\" alt=\"DNBR - crit\u00e9rio\" width=\"278\" height=\"74\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/DNBR-criterion.png\" \/><\/a><\/p>\n<p><em><span>O fluxo de calor local deve ser menor que o fluxo de calor cr\u00edtico (ou seja, DNBR deve ser maior que um).<\/span><\/em><\/p>\n<p><strong><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/DNBR-Departure-from-Nucleate-Boiling-Ratio.png\"><img loading=\"lazy\" class=\"alignright size-medium wp-image-20775 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/DNBR-Departure-from-Nucleate-Boiling-Ratio-289x300.png\" alt=\"DNBR - Partida da Raz\u00e3o de Ebuli\u00e7\u00e3o Nucleada\" width=\"289\" height=\"300\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/DNBR-Departure-from-Nucleate-Boiling-Ratio-289x300.png\" \/><\/a><span>Mas, na realidade<\/span><\/strong><span>\u00a0, nenhuma correla\u00e7\u00e3o \u00e9 perfeita e incertezas devem estar envolvidas nesse c\u00e1lculo.\u00a0Essas faixas de incerteza ou limites de erro estabelecem um valor m\u00ednimo aceit\u00e1vel para a rela\u00e7\u00e3o DNB, que pode ser significativamente maior que um, conforme indicado na figura.\u00a0As incertezas podem chegar a cerca de 20% e, portanto, o DNBR deve ser maior que, por exemplo,\u00a0<\/span><strong><span>DNBR\u00a0<\/span><sub><span>lim<\/span><\/sub><span>\u00a0= 1,2<\/span><\/strong><span>\u00a0.<\/span><\/p>\n<p><span>Como pode ser visto na figura, o CHF diminui significativamente com o aumento da entalpia do l\u00edquido de arrefecimento, portanto, o valor m\u00ednimo de DNBR n\u00e3o est\u00e1 necessariamente no centro do n\u00facleo.\u00a0A rela\u00e7\u00e3o DNB m\u00ednima (MDNBR) ocorre no local onde o fluxo de calor cr\u00edtico e o fluxo de calor operacional s\u00e3o os mais pr\u00f3ximos e geralmente est\u00e1 na parte superior do n\u00facleo.\u00a0Al\u00e9m disso, na entrada do canal onde o sub-resfriamento do refrigerante \u00e9 o mais alto, esperamos que o fluxo de calor necess\u00e1rio fa\u00e7a com que o DNB neste local seja extremamente alto.\u00a0Por outro lado, na sa\u00edda do canal onde a entalpia do refrigerante \u00e9 a mais alta, o fluxo de calor necess\u00e1rio para causar DNB deve ser o mais baixo.<\/span><\/p>\n<p><span>Refer\u00eancia especial: Tong, LS, Weisman, Joel.\u00a0An\u00e1lise T\u00e9rmica de Reatores de \u00c1gua Pressurizada.\u00a0Amer Nuclear Society, 3a edi\u00e7\u00e3o, 5\/1996.\u00a0ISBN-13: 978-0894480386.<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/critical-heat-flux-vs-local-heat-flux.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20776 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/critical-heat-flux-vs-local-heat-flux.png\" alt=\"fluxo de calor cr\u00edtico vs fluxo de calor local\" width=\"582\" height=\"622\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/critical-heat-flux-vs-local-heat-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\"><\/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<h2><span>Transfer\u00eancia de calor p\u00f3s-DNB<\/span><\/h2>\n<p><span>O fluxo de calor em ebuli\u00e7\u00e3o nucleado n\u00e3o pode ser aumentado indefinidamente.\u00a0Em algum valor, chamamos de \u201c\u00a0<\/span><strong><span>fluxo cr\u00edtico de calor<\/span><\/strong><span>\u00a0\u201d (\u00a0<\/span><strong><span>CHF<\/span><\/strong><span>\u00a0), o vapor produzido pode formar uma camada isolante sobre a superf\u00edcie, que por sua vez deteriora o coeficiente de transfer\u00eancia de calor.\u00a0Isso ocorre porque uma grande fra\u00e7\u00e3o da superf\u00edcie \u00e9 coberta por uma pel\u00edcula de vapor, que atua como um isolamento t\u00e9rmico devido \u00e0 baixa condutividade t\u00e9rmica do vapor em rela\u00e7\u00e3o \u00e0 do l\u00edquido.\u00a0Imediatamente ap\u00f3s o fluxo cr\u00edtico de calor ter sido atingido, a ebuli\u00e7\u00e3o se torna inst\u00e1vel e a ebuli\u00e7\u00e3o de transi\u00e7\u00e3o ocorre.\u00a0A transi\u00e7\u00e3o da ebuli\u00e7\u00e3o nucleada para a ebuli\u00e7\u00e3o de pel\u00edcula \u00e9 conhecida como &#8221;\u00a0<\/span><strong><span>crise de ebuli\u00e7\u00e3o<\/span><\/strong><span>\u00a0&#8220;.\u00a0Como al\u00e9m do ponto CHF o coeficiente de transfer\u00eancia de calor diminui, a transi\u00e7\u00e3o para a ebuli\u00e7\u00e3o de pel\u00edcula \u00e9 geralmente inevit\u00e1vel.<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Boiling-Curve-Boiling-Modes.png\"><img loading=\"lazy\" class=\"alignright size-medium wp-image-20779 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Boiling-Curve-Boiling-Modes-208x300.png\" alt=\"Curva de Ebuli\u00e7\u00e3o - Modos de Ebuli\u00e7\u00e3o\" width=\"208\" height=\"300\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Boiling-Curve-Boiling-Modes-208x300.png\" \/><\/a><span>Um aumento adicional no fluxo de calor n\u00e3o \u00e9 necess\u00e1rio para manter a ebuli\u00e7\u00e3o de pel\u00edcula.\u00a0Uma pel\u00edcula de vapor cobre completamente a superf\u00edcie.\u00a0Isso reduz significativamente o coeficiente de convec\u00e7\u00e3o, uma vez que a camada de vapor tem uma capacidade de transfer\u00eancia de calor significativamente menor.\u00a0Como resultado, o excesso de temperatura atinge um valor muito alto.\u00a0Al\u00e9m do\u00a0<\/span><a title=\"Efeito Leidenfrost - Ponto Leidenfrost\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/heat-transfer\/boiling-and-condensation\/leidenfrost-effect-leidenfrost-point\/\"><span>ponto de Leidenfrost<\/span><\/a><span>\u00a0, um filme de vapor cont\u00ednuo cobre a superf\u00edcie e n\u00e3o h\u00e1 contato entre a fase l\u00edquida e a superf\u00edcie.\u00a0Nesta situa\u00e7\u00e3o, a transfer\u00eancia de calor \u00e9 tanto por radia\u00e7\u00e3o quanto por condu\u00e7\u00e3o ao vapor.\u00a0A superf\u00edcie aquecida estabiliza estabiliza sua temperatura no ponto E (veja a figura).\u00a0Se o material n\u00e3o for suficientemente forte para suportar essa temperatura, o equipamento falhar\u00e1 por danos ao material.<\/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>Rela\u00e7\u00e3o de pot\u00eancia cr\u00edtica &#8211; Secagem<\/span><\/h2>\n<p><strong><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Flow-Boiling-Dryout.png\"><img loading=\"lazy\" class=\"alignright size-medium wp-image-20773 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Flow-Boiling-Dryout-257x300.png\" alt=\"Ebuli\u00e7\u00e3o do fluxo - secagem\" width=\"257\" height=\"300\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Flow-Boiling-Dryout-257x300.png\" \/><\/a><\/strong>Nos BWRs, um fen\u00f4meno semelhante \u00e9 conhecido como\u00a0<strong>\u201csecagem\u201d<\/strong>\u00a0e est\u00e1 diretamente associado a\u00a0<strong>altera\u00e7\u00f5es no padr\u00e3o de fluxo<\/strong>\u00a0durante a evapora\u00e7\u00e3o na regi\u00e3o de alta qualidade.\u00a0Em determinadas combina\u00e7\u00f5es de taxa de fluxo atrav\u00e9s de um canal, press\u00e3o, qualidade de fluxo e taxa de calor linear, o\u00a0<strong>filme l\u00edquido\u00a0<\/strong>da parede\u00a0<strong>pode esgotar-se<\/strong>\u00a0e a parede pode ser\u00a0<strong>seca<\/strong>\u00a0.\u00a0Normalmente, a superf\u00edcie do combust\u00edvel \u00e9 efetivamente resfriada com l\u00edquido fervente.\u00a0No entanto, quando o fluxo de calor excede um\u00a0<strong>valor cr\u00edtico<\/strong>\u00a0(CHF &#8211; fluxo de calor cr\u00edtico), o padr\u00e3o de fluxo pode atingir as\u00a0<strong>condi\u00e7\u00f5es de secagem<\/strong>\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<strong>aumento dr\u00e1stico da temperatura da superf\u00edcie do combust\u00edvel\u00a0<\/strong>.\u00a0Na regi\u00e3o de alta qualidade, a crise ocorre com um fluxo de calor menor.\u00a0Como a velocidade do fluxo no n\u00facleo de vapor \u00e9 alta, a transfer\u00eancia de calor p\u00f3s-CHF \u00e9 muito melhor do que no fluxo cr\u00edtico de baixa qualidade (ou seja, para PWRs, os aumentos de temperatura s\u00e3o mais altos e mais r\u00e1pidos).<\/p>\n<p><span>Nesse caso, os engenheiros definem o par\u00e2metro conhecido como\u00a0<\/span><strong><span>rela\u00e7\u00e3o de pot\u00eancia cr\u00edtica m\u00ednima (MCPR), em<\/span><\/strong><span>\u00a0vez de DNBR.\u00a0A\u00a0<\/span><strong><span>raz\u00e3o de pot\u00eancia cr\u00edtica (RCP)<\/span><\/strong><span>\u00a0\u00e9 usada para determinar os limites t\u00e9rmicos dos reatores de \u00e1gua fervente.<\/span><\/p>\n<p><strong><span>Defini\u00e7\u00e3o de RCP:<\/span><\/strong><\/p>\n<p><em><span>A RCP \u00e9 a energia na montagem que \u00e9 calculada pela aplica\u00e7\u00e3o da (s) correla\u00e7\u00e3o (\u00f5es) apropriada (s) para causar algum ponto na montagem para sofrer uma transi\u00e7\u00e3o de ebuli\u00e7\u00e3o, dividida pela pot\u00eancia operacional real da montagem.<\/span><\/em><\/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<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>Na ebuli\u00e7\u00e3o do fluxo (ou ebuli\u00e7\u00e3o por convec\u00e7\u00e3o for\u00e7ada), o fluxo de fluido \u00e9 for\u00e7ado sobre uma superf\u00edcie por meios externos, como uma bomba, bem como por efeitos de flutuabilidade.\u00a0Engenharia T\u00e9rmica Ebuli\u00e7\u00e3o por fluxo &#8211; fervura por convec\u00e7\u00e3o for\u00e7ada Na\u00a0ebuli\u00e7\u00e3o do fluxo\u00a0(ou ebuli\u00e7\u00e3o por convec\u00e7\u00e3o for\u00e7ada), o fluxo de fluido \u00e9 for\u00e7ado sobre uma superf\u00edcie &#8230; <a title=\"O que \u00e9 ebuli\u00e7\u00e3o por fluxo &#8211; ebuli\u00e7\u00e3o por convec\u00e7\u00e3o for\u00e7ada &#8211; Defini\u00e7\u00e3o\" class=\"read-more\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-ebulicao-por-fluxo-ebulicao-por-conveccao-forcada-definicao\/\" aria-label=\"More on O que \u00e9 ebuli\u00e7\u00e3o por fluxo &#8211; ebuli\u00e7\u00e3o por convec\u00e7\u00e3o for\u00e7ada &#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 ebuli\u00e7\u00e3o por fluxo - ebuli\u00e7\u00e3o por convec\u00e7\u00e3o for\u00e7ada - Defini\u00e7\u00e3o<\/title>\n<meta name=\"description\" content=\"Na ebuli\u00e7\u00e3o do fluxo (ou ebuli\u00e7\u00e3o por convec\u00e7\u00e3o for\u00e7ada), o fluxo de fluido \u00e9 for\u00e7ado sobre uma superf\u00edcie por meios externos, como uma bomba, bem como por efeitos de flutuabilidade. Engenharia T\u00e9rmica\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-ebulicao-por-fluxo-ebulicao-por-conveccao-forcada-definicao\/\" \/>\n<meta property=\"og:locale\" content=\"pt_BR\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"O que \u00e9 ebuli\u00e7\u00e3o por fluxo - ebuli\u00e7\u00e3o por convec\u00e7\u00e3o for\u00e7ada - Defini\u00e7\u00e3o\" \/>\n<meta property=\"og:description\" content=\"Na ebuli\u00e7\u00e3o do fluxo (ou ebuli\u00e7\u00e3o por convec\u00e7\u00e3o for\u00e7ada), o fluxo de fluido \u00e9 for\u00e7ado sobre uma superf\u00edcie por meios externos, como uma bomba, bem como por efeitos de flutuabilidade. Engenharia T\u00e9rmica\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-ebulicao-por-fluxo-ebulicao-por-conveccao-forcada-definicao\/\" \/>\n<meta property=\"og:site_name\" content=\"Thermal Engineering\" \/>\n<meta property=\"article:published_time\" content=\"2019-11-03T21:23:08+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2020-01-23T09:29:35+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Flow-Boiling-Boiling-Modes-117x300.png\" \/>\n<meta name=\"twitter:card\" content=\"summary\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\">\n\t<meta name=\"twitter:data1\" content=\"Nick Connor\">\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\">\n\t<meta name=\"twitter:data2\" content=\"17 minutos\">\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebSite\",\"@id\":\"https:\/\/www.thermal-engineering.org\/fr\/#website\",\"url\":\"https:\/\/www.thermal-engineering.org\/fr\/\",\"name\":\"Thermal Engineering\",\"description\":\"\",\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":\"https:\/\/www.thermal-engineering.org\/fr\/?s={search_term_string}\",\"query-input\":\"required name=search_term_string\"}],\"inLanguage\":\"pt-BR\"},{\"@type\":\"ImageObject\",\"@id\":\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-ebulicao-por-fluxo-ebulicao-por-conveccao-forcada-definicao\/#primaryimage\",\"inLanguage\":\"pt-BR\",\"url\":\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Flow-Boiling-Boiling-Modes-117x300.png\"},{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-ebulicao-por-fluxo-ebulicao-por-conveccao-forcada-definicao\/#webpage\",\"url\":\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-ebulicao-por-fluxo-ebulicao-por-conveccao-forcada-definicao\/\",\"name\":\"O que \\u00e9 ebuli\\u00e7\\u00e3o por fluxo - ebuli\\u00e7\\u00e3o por convec\\u00e7\\u00e3o for\\u00e7ada - Defini\\u00e7\\u00e3o\",\"isPartOf\":{\"@id\":\"https:\/\/www.thermal-engineering.org\/fr\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-ebulicao-por-fluxo-ebulicao-por-conveccao-forcada-definicao\/#primaryimage\"},\"datePublished\":\"2019-11-03T21:23:08+00:00\",\"dateModified\":\"2020-01-23T09:29:35+00:00\",\"author\":{\"@id\":\"https:\/\/www.thermal-engineering.org\/fr\/#\/schema\/person\/e8c544db9afedaec8574d6464f9398bb\"},\"description\":\"Na ebuli\\u00e7\\u00e3o do fluxo (ou ebuli\\u00e7\\u00e3o por convec\\u00e7\\u00e3o for\\u00e7ada), o fluxo de fluido \\u00e9 for\\u00e7ado sobre uma superf\\u00edcie por meios externos, como uma bomba, bem como por efeitos de flutuabilidade. Engenharia T\\u00e9rmica\",\"inLanguage\":\"pt-BR\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-ebulicao-por-fluxo-ebulicao-por-conveccao-forcada-definicao\/\"]}]},{\"@type\":\"Person\",\"@id\":\"https:\/\/www.thermal-engineering.org\/fr\/#\/schema\/person\/e8c544db9afedaec8574d6464f9398bb\",\"name\":\"Nick Connor\",\"image\":{\"@type\":\"ImageObject\",\"@id\":\"https:\/\/www.thermal-engineering.org\/fr\/#personlogo\",\"inLanguage\":\"pt-BR\",\"url\":\"https:\/\/secure.gravatar.com\/avatar\/84c0dec310b44b65da29dc9df6925239?s=96&d=mm&r=g\",\"caption\":\"Nick Connor\"}}]}<\/script>\n<!-- \/ Yoast SEO plugin. -->","_links":{"self":[{"href":"https:\/\/www.thermal-engineering.org\/pt-br\/wp-json\/wp\/v2\/posts\/47292"}],"collection":[{"href":"https:\/\/www.thermal-engineering.org\/pt-br\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.thermal-engineering.org\/pt-br\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.thermal-engineering.org\/pt-br\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.thermal-engineering.org\/pt-br\/wp-json\/wp\/v2\/comments?post=47292"}],"version-history":[{"count":0,"href":"https:\/\/www.thermal-engineering.org\/pt-br\/wp-json\/wp\/v2\/posts\/47292\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.thermal-engineering.org\/pt-br\/wp-json\/wp\/v2\/media?parent=47292"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.thermal-engineering.org\/pt-br\/wp-json\/wp\/v2\/categories?post=47292"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.thermal-engineering.org\/pt-br\/wp-json\/wp\/v2\/tags?post=47292"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}