{"id":47459,"date":"2019-11-05T01:48:39","date_gmt":"2019-11-05T00:48:39","guid":{"rendered":"https:\/\/www.thermal-engineering.org\/exemplo-de-conveccao-problema-com-solucao-definicao\/"},"modified":"2020-01-23T14:34:05","modified_gmt":"2020-01-23T13:34:05","slug":"exemplo-de-conveccao-problema-com-solucao-definicao","status":"publish","type":"post","link":"https:\/\/www.thermal-engineering.org\/pt-br\/exemplo-de-conveccao-problema-com-solucao-definicao\/","title":{"rendered":"Exemplo de convec\u00e7\u00e3o &#8211; Problema com solu\u00e7\u00e3o &#8211; Defini\u00e7\u00e3o"},"content":{"rendered":"<div class=\"su-quote su-quote-style-default\">\n<div class=\"su-quote-inner su-clearfix\">Este exemplo mostra como calcular a transfer\u00eancia de calor por convec\u00e7\u00e3o.\u00a0C\u00e1lculo do coeficiente de transfer\u00eancia de calor e da temperatura da superf\u00edcie do revestimento.\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>Exemplo &#8211; Convec\u00e7\u00e3o &#8211; Temperatura da superf\u00edcie do revestimento<\/h2>\n<p><strong><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Convection-Convective-Heat-Transfer-example.png\"><img loading=\"lazy\" class=\"alignright size-medium wp-image-20406 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Convection-Convective-Heat-Transfer-example-275x300.png\" alt=\"Convec\u00e7\u00e3o - Transfer\u00eancia de calor por convec\u00e7\u00e3o\" width=\"275\" height=\"300\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Convection-Convective-Heat-Transfer-example-275x300.png\" \/><\/a><\/strong><\/p>\n<p><strong>Exemplo &#8211; Convec\u00e7\u00e3o &#8211; Problema com Solu\u00e7\u00e3o\u00a0<\/strong><\/p>\n<p><strong>O<\/strong>\u00a0revestimento \u00e9 a camada externa das barras de combust\u00edvel, situada entre o\u00a0<strong>l\u00edquido de arrefecimento<\/strong>\u00a0do\u00a0<strong>reator<\/strong>\u00a0e o\u00a0<a title=\"Combust\u00edvel nuclear\" href=\"https:\/\/www.nuclear-power.com\/nuclear-power-plant\/nuclear-fuel\/\"><strong>combust\u00edvel nuclear<\/strong><\/a>(isto \u00e9,\u00a0<strong>granulados de combust\u00edvel<\/strong>\u00a0).\u00a0\u00c9 feito de um material resistente \u00e0 corros\u00e3o com se\u00e7\u00e3o transversal de baixa absor\u00e7\u00e3o para\u00a0<a title=\"N\u00eautron t\u00e9rmico\" href=\"https:\/\/www.nuclear-power.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/fundamental-particles\/neutron\/thermal-neutron\/\">n\u00eautrons t\u00e9rmicos<\/a>\u00a0, geralmente\u00a0<strong>liga de zirc\u00f4nio<\/strong>\u00a0.\u00a0<strong>O revestimento<\/strong>\u00a0evita que os produtos de fiss\u00e3o radioativa escapem da matriz de combust\u00edvel para o l\u00edquido de arrefecimento do reator e os contaminem.\u00a0O revestimento constitui uma das barreiras na\u00a0abordagem de\u00a0&#8216;\u00a0<strong>defesa em profundidade<\/strong>\u00a0&#8216;; portanto, sua capacidade de\u00a0<strong>refrigera\u00e7\u00e3o<\/strong>\u00a0\u00e9 um dos principais aspectos de seguran\u00e7a.<\/p>\n<p>Considere o revestimento de combust\u00edvel do raio interno\u00a0<strong>r\u00a0<\/strong><strong><sub>Zr, 2<\/sub><\/strong><strong>\u00a0= 0,408 cm<\/strong>\u00a0e raio externo\u00a0<strong>r\u00a0<\/strong><strong><sub>Zr, 1<\/sub><\/strong><strong>\u00a0= 0,465 cm<\/strong>\u00a0.\u00a0Em compara\u00e7\u00e3o com o pellet de combust\u00edvel, quase n\u00e3o h\u00e1 gera\u00e7\u00e3o de calor no revestimento do combust\u00edvel (o revestimento \u00e9\u00a0<a href=\"https:\/\/www.nuclear-power.com\/nuclear-power\/fission\/energy-release-from-fission\/\">levemente aquecido pela radia\u00e7\u00e3o<\/a>\u00a0).\u00a0Todo o calor gerado no combust\u00edvel deve ser transferido por\u00a0<a title=\"Condu\u00e7\u00e3o T\u00e9rmica - Condu\u00e7\u00e3o T\u00e9rmica\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-conducao-termica-conducao-termica-definicao\/\"><strong>condu\u00e7\u00e3o<\/strong><\/a>\u00a0atrav\u00e9s do revestimento e, portanto, a superf\u00edcie interna \u00e9 mais quente que a superf\u00edcie externa.<\/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<p><span>Assuma isso:<\/span><\/p>\n<ul>\n<li><span>o di\u00e2metro externo do revestimento \u00e9:\u00a0<\/span><strong><span>d = 2 xr\u00a0<\/span><sub><span>Zr, 1<\/span><\/sub><span>\u00a0= 9,3 mm<\/span><\/strong><\/li>\n<li><span>o passo dos pinos de combust\u00edvel \u00e9:\u00a0<\/span><strong><span>p = 13 mm<\/span><\/strong><\/li>\n<li><span>a\u00a0<\/span><a title=\"Condutividade t\u00e9rmica\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-condutividade-termica-definicao\/\"><span>condutividade t\u00e9rmica<\/span><\/a><span>\u00a0da\u00a0<\/span><a title=\"L\u00edquido saturado e sub-resfriado\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/materials-nuclear-engineering\/properties-steam-what-is-steam\/saturated-and-subcooled-liquid\/\"><span>\u00e1gua saturada<\/span><\/a><span>\u00a0a 300 \u00b0 C \u00e9:\u00a0<\/span><strong><span>k\u00a0<\/span><\/strong><strong><sub><span>H2O<\/span><\/sub><\/strong><strong><span>\u00a0= 0,545 W \/ mK<\/span><\/strong><\/li>\n<li><span>a viscosidade din\u00e2mica da \u00e1gua saturada a 300 \u00b0 C \u00e9:\u00a0<\/span><strong><span>\u03bc = 0,0000859 Ns \/ m\u00a0<\/span><\/strong><strong><sup><span>2<\/span><\/sup><\/strong><\/li>\n<li><span>a\u00a0<\/span><a title=\"O que \u00e9 densidade - F\u00edsica\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/thermodynamic-properties\/what-is-density-physics\/\"><span>densidade<\/span><\/a><span>\u00a0do fluido\u00a0\u00e9:\u00a0<\/span><strong><span>\u03c1 = 714 kg \/ m\u00a0<\/span><\/strong><strong><sup><span>3<\/span><\/sup><\/strong><\/li>\n<li><span>o\u00a0<\/span><a href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/laws-of-thermodynamics\/first-law-of-thermodynamics\/heat-capacity\/\"><strong><span>calor espec\u00edfico<\/span><\/strong><\/a><span>\u00a0\u00e9:\u00a0<\/span><strong><span>c\u00a0<\/span><\/strong><strong><sub><span>p<\/span><\/sub><\/strong><strong><span>\u00a0= 5,65 kJ \/ kg.K<\/span><\/strong><\/li>\n<li><span>a velocidade de fluxo do n\u00facleo \u00e9 constante e igual a\u00a0<\/span><strong><span>V\u00a0<\/span><\/strong><strong><sub><span>core<\/span><\/sub><\/strong><strong><span>\u00a0= 5 m \/ s<\/span><\/strong><\/li>\n<li><span>a temperatura do l\u00edquido de arrefecimento do reator nesta coordenada axial \u00e9:\u00a0<\/span><strong><span>T a\u00a0<\/span><\/strong><strong><sub><span>granel<\/span><\/sub><\/strong><strong><span>\u00a0= 296 \u00b0 C<\/span><\/strong><\/li>\n<li><span>a taxa linear de calor do combust\u00edvel \u00e9\u00a0<\/span><strong><span>q\u00a0<\/span><\/strong><strong><sub><span>L<\/span><\/sub><\/strong><strong><span>\u00a0= 300 W \/ cm<\/span><\/strong><span>\u00a0(F\u00a0<\/span><sub><span>Q<\/span><\/sub><span>\u00a0\u2248 2.0) e, portanto, a taxa volum\u00e9trica de calor \u00e9 q\u00a0<\/span><sub><span>V<\/span><\/sub><span>\u00a0= 597 x 10\u00a0<\/span><sup><span>6<\/span><\/sup><span>\u00a0W \/ m\u00a0<\/span><sup><span>3<\/span><\/sup><\/li>\n<\/ul>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Hydraulic-Diameter-Fuel-Channel.png\"><img loading=\"lazy\" class=\"alignright size-medium wp-image-20407 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Hydraulic-Diameter-Fuel-Channel-254x300.png\" alt=\"Di\u00e2metro hidr\u00e1ulico - canal de combust\u00edvel\" width=\"254\" height=\"300\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Hydraulic-Diameter-Fuel-Channel-254x300.png\" \/><\/a><span>Calcule o n\u00famero de\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,\u00a0<\/span><a title=\"N\u00famero de Reynolds\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/reynolds-number\/\"><span>Reynolds<\/span><\/a><span>\u00a0e Nusselt para esse regime de fluxo (fluxo turbulento for\u00e7ado interno) dentro da estrutura retangular de combust\u00edvel (canal de combust\u00edvel), depois calcule o\u00a0<\/span><strong><span>coeficiente de transfer\u00eancia de calor<\/span><\/strong><span>\u00a0e, finalmente, a\u00a0<\/span><strong><span>temperatura da superf\u00edcie<\/span><\/strong><span>\u00a0do\u00a0<strong>revestimento<\/strong>\u00a0,\u00a0<\/span><strong><span>T\u00a0<\/span><sub><span>Zr, 1<\/span><\/sub><\/strong><span>\u00a0.<\/span><\/p>\n<p><span>Para calcular a\u00a0<\/span><strong><span>temperatura da superf\u00edcie<\/span><\/strong><span>\u00a0do\u00a0<strong>revestimento<\/strong>\u00a0, precisamos calcular o n\u00famero de\u00a0<\/span><strong><span>Prandtl<\/span><\/strong><span>\u00a0,\u00a0<\/span><strong><span>Reynolds<\/span><\/strong><span>\u00a0e\u00a0<\/span><strong><span>Nusselt<\/span><\/strong><span>\u00a0, porque a transfer\u00eancia de calor para esse regime de fluxo pode ser descrita pela\u00a0<\/span><strong><span>equa\u00e7\u00e3o de Dittus-Boelter<\/span><\/strong><span>\u00a0, que \u00e9:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Dittus-Boelter-Equation-Formula.png\"><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\" 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\" \/><\/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>C\u00e1lculo do n\u00famero Prandtl<\/span><\/h2>\n<p><span>Para calcular 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, precisamos saber:<\/span><\/p>\n<ul>\n<li><span>a condutividade t\u00e9rmica da \u00e1gua saturada a 300 \u00b0 C \u00e9:\u00a0<\/span><strong><span>k\u00a0<\/span><\/strong><strong><sub><span>H2O<\/span><\/sub><\/strong><strong><span>\u00a0= 0,545 W \/ mK<\/span><\/strong><\/li>\n<li><span>a viscosidade din\u00e2mica da \u00e1gua saturada a 300 \u00b0 C \u00e9:\u00a0<\/span><strong><span>\u03bc = 0,0000859 Ns \/ m\u00a0<\/span><\/strong><strong><sup><span>2<\/span><\/sup><\/strong><\/li>\n<li><span>o\u00a0<\/span><a href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/laws-of-thermodynamics\/first-law-of-thermodynamics\/heat-capacity\/\"><strong><span>calor espec\u00edfico<\/span><\/strong><\/a><span>\u00a0\u00e9:\u00a0<\/span><strong><span>c\u00a0<\/span><\/strong><strong><sub><span>p<\/span><\/sub><\/strong><strong><span>\u00a0= 5,65 kJ \/ kg.K<\/span><\/strong><\/li>\n<\/ul>\n<p><span>Observe que todos esses par\u00e2metros diferem significativamente para a \u00e1gua a 300 \u00b0 C daqueles a 20 \u00b0 C.\u00a0O n\u00famero de prandtl para\u00a0<\/span><a href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/materials-nuclear-engineering\/properties-of-water\/\"><span>\u00e1gua<\/span><\/a><span>\u00a0a 20 \u00b0 C \u00e9 de cerca de\u00a0<\/span><strong><span>6,91.\u00a0<\/span><\/strong><span>O n\u00famero de Prandtl para o l\u00edquido de refrigera\u00e7\u00e3o do reator a 300 \u00b0 C \u00e9 ent\u00e3o:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/prandtl-number-example.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20411 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/prandtl-number-example.png\" alt=\"n\u00famero prandtl - exemplo\" width=\"469\" height=\"80\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/prandtl-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-spacer\"><\/div>\n<h2><span>C\u00e1lculo do n\u00famero de Reynolds<\/span><\/h2>\n<p><span>Para calcular o n\u00famero de Reynolds, precisamos saber:<\/span><\/p>\n<ul>\n<li><span>o di\u00e2metro externo do revestimento \u00e9:\u00a0<\/span><strong><span>d = 2 xr\u00a0<\/span><sub><span>Zr, 1<\/span><\/sub><span>\u00a0= 9,3 mm<\/span><\/strong><span>\u00a0(para calcular o di\u00e2metro hidr\u00e1ulico)<\/span><\/li>\n<li><span>o passo dos pinos de combust\u00edvel \u00e9:\u00a0<\/span><strong><span>p = 13 mm<\/span><\/strong><span>\u00a0\u00a0(para calcular o di\u00e2metro hidr\u00e1ulico)<\/span><\/li>\n<li><span>a viscosidade din\u00e2mica da \u00e1gua saturada a 300 \u00b0 C \u00e9:\u00a0<\/span><strong><span>\u03bc = 0,0000859 Ns \/ m\u00a0<\/span><\/strong><strong><sup><span>2<\/span><\/sup><\/strong><\/li>\n<li><span>a densidade do fluido \u00e9:\u00a0<\/span><strong><span>\u03c1 = 714 kg \/ m\u00a0<\/span><\/strong><strong><sup><span>3<\/span><\/sup><\/strong><\/li>\n<\/ul>\n<p><strong><span>O di\u00e2metro hidr\u00e1ulico, D\u00a0<\/span><\/strong><strong><sub><span>h<\/span><\/sub><\/strong><span>\u00a0, \u00e9 um termo comumente usado ao manipular o fluxo em\u00a0<\/span><strong><span>tubos e canais n\u00e3o circulares<\/span><\/strong><span>\u00a0.\u00a0O\u00a0<\/span><strong><span>di\u00e2metro hidr\u00e1ulico do canal de combust\u00edvel<\/span><\/strong><span>\u00a0,\u00a0<\/span><em><span>D\u00a0<\/span><\/em><em><sub><span>h<\/span><\/sub><\/em><span>\u00a0, \u00e9 igual a 13,85 mm.<\/span><\/p>\n<p><span>Veja tamb\u00e9m:\u00a0<\/span><a title=\"Di\u00e2metro hidr\u00e1ulico\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/internal-flow\/hydraulic-diameter-2\/\"><span>Di\u00e2metro hidr\u00e1ulico<\/span><\/a><\/p>\n<p><span>O\u00a0<\/span><strong><span>n\u00famero de Reynolds<\/span><\/strong><span>\u00a0dentro 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\/reynolds-number-example.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20412 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/reynolds-number-example.png\" alt=\"n\u00famero de reynolds - exemplo\" width=\"593\" height=\"78\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/reynolds-number-example.png\" \/><\/a><\/p>\n<p><span>Isso satisfaz plenamente as\u00a0<\/span><a title=\"Fluxo turbulento\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-fluxo-turbulento-definicao\/\"><strong><span>condi\u00e7\u00f5es turbulentas<\/span><\/strong><\/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-spacer\"><\/div>\n<h2><span>C\u00e1lculo do coeficiente de transfer\u00eancia de calor e da temperatura da superf\u00edcie do revestimento, T\u00a0<\/span><sub><span>Zr, 1<\/span><\/sub><\/h2>\n<p><span>O conhecimento detalhado da geometria, par\u00e2metros do fluido, raio externo do revestimento, taxa de calor linear, coeficiente de transfer\u00eancia de calor por convec\u00e7\u00e3o nos permite calcular a diferen\u00e7a de temperatura\u00a0<\/span><strong><span>\u2206T<\/span><\/strong><span>\u00a0entre o l\u00edquido de arrefecimento (T a\u00a0<\/span><sub><span>granel<\/span><\/sub><span>\u00a0) e a superf\u00edcie do revestimento (T\u00a0<\/span><sub><span>Zr, 1<\/span><\/sub><span>\u00a0).<\/span><\/p>\n<p><span>Para calcular a temperatura da superf\u00edcie do revestimento, precisamos saber:<\/span><\/p>\n<ul>\n<li><span>o di\u00e2metro externo do revestimento \u00e9: d = 2 x\u00a0<\/span><strong><span>r\u00a0<\/span><\/strong><strong><sub><span>Zr, 1<\/span><\/sub><\/strong><strong><span>\u00a0= 9,3 mm<\/span><\/strong><\/li>\n<li><span>o n\u00famero de Nusselt, que \u00e9\u00a0<\/span><strong><span>Nu\u00a0<\/span><\/strong><strong><sub><span>Dh<\/span><\/sub><\/strong><strong><span>\u00a0= 890<\/span><\/strong><\/li>\n<li><span>o di\u00e2metro hidr\u00e1ulico do canal de combust\u00edvel \u00e9:\u00a0<\/span><strong><em><span>D\u00a0<\/span><\/em><\/strong><strong><em><sub><span>h<\/span><\/sub><\/em><\/strong><strong><span>\u00a0= 13,85 mm<\/span><\/strong><\/li>\n<li><span>a condutividade t\u00e9rmica do l\u00edquido de refrigera\u00e7\u00e3o do reator (300 \u00b0 C) \u00e9:\u00a0<\/span><strong><span>k\u00a0<\/span><\/strong><strong><sub><span>H2O<\/span><\/sub><\/strong><strong><span>\u00a0= 0,545 W \/ mK<\/span><\/strong><\/li>\n<li><span>a temperatura a granel do l\u00edquido de refrigera\u00e7\u00e3o do reator nesta coordenada axial \u00e9:\u00a0<\/span><strong><span>T a\u00a0<\/span><\/strong><strong><sub><span>granel<\/span><\/sub><\/strong><strong><span>\u00a0= 296 \u00b0 C<\/span><\/strong><\/li>\n<li><span>a taxa linear de calor do combust\u00edvel \u00e9:\u00a0<\/span><strong><span>q\u00a0<\/span><\/strong><strong><sub><span>L<\/span><\/sub><\/strong><strong><span>\u00a0= 300 W \/ cm<\/span><\/strong><span>\u00a0(F\u00a0<\/span><sub><span>Q<\/span><\/sub><span>\u00a0\u2248 2.0)<\/span><\/li>\n<\/ul>\n<p><span>O coeficiente de transfer\u00eancia de calor convectivo,\u00a0<\/span><strong><span>h<\/span><\/strong><span>\u00a0, \u00e9 dado diretamente pela defini\u00e7\u00e3o do n\u00famero de Nusselt:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/convective-heat-transfer-coefficient-example.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20410 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/convective-heat-transfer-coefficient-example.png\" alt=\"coeficiente de transfer\u00eancia de calor por convec\u00e7\u00e3o - exemplo\" width=\"619\" height=\"92\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/convective-heat-transfer-coefficient-example.png\" \/><\/a><\/p>\n<p><span>Finalmente, podemos calcular a temperatura da superf\u00edcie do revestimento (T\u00a0<\/span><sub><span>Zr, 1<\/span><\/sub><span>\u00a0) simplesmente usando a\u00a0<\/span><strong><span>Lei de Newton de resfriamento<\/span><\/strong><span>\u00a0:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Newton-law-of-cooling-example.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20408 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Newton-law-of-cooling-example.png\" alt=\"Lei de Newton do resfriamento - exemplo\" width=\"377\" height=\"369\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Newton-law-of-cooling-example.png\" \/><\/a><\/p>\n<p><span>Para PWRs em opera\u00e7\u00e3o normal, h\u00e1\u00a0<\/span><a href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/materials-nuclear-engineering\/properties-steam-what-is-steam\/saturated-and-subcooled-liquid\/\"><span>\u00e1gua l\u00edquida comprimida<\/span><\/a><span>\u00a0dentro do n\u00facleo do reator, loops e geradores de vapor.\u00a0A press\u00e3o \u00e9 mantida em aproximadamente\u00a0<\/span><strong><span>16MPa<\/span><\/strong><span>\u00a0.\u00a0A essa press\u00e3o, a \u00e1gua ferve a aproximadamente\u00a0<\/span><strong><span>350 \u00b0 C<\/span><\/strong><span>\u00a0(662 \u00b0 F).\u00a0Como pode ser visto, a temperatura da superf\u00edcie T\u00a0<\/span><sub><span>Zr, 1<\/span><\/sub><span>\u00a0= 325 \u00b0 C garante que mesmo a ebuli\u00e7\u00e3o sub-resfriada n\u00e3o ocorra.\u00a0Observe que a ebuli\u00e7\u00e3o sub-resfriada requer T\u00a0<\/span><sub><span>Zr, 1<\/span><\/sub><span>\u00a0= T\u00a0<\/span><sub><span>sat<\/span><\/sub><span>\u00a0.\u00a0Como as temperaturas de entrada da \u00e1gua s\u00e3o geralmente de cerca de\u00a0<\/span><strong><span>290 \u00b0 C<\/span><\/strong><span>(554 \u00b0 F), \u00e9 \u00f3bvio que este exemplo corresponde \u00e0 parte inferior do n\u00facleo.\u00a0Em eleva\u00e7\u00f5es mais altas do n\u00facleo, a temperatura a granel pode atingir at\u00e9 330 \u00b0 C.\u00a0A diferen\u00e7a de temperatura de 29 \u00b0 C causa a fervura sub-resfriada (330 \u00b0 C + 29 \u00b0 C&gt; 350 \u00b0 C).\u00a0Por outro lado, a\u00a0<\/span><strong><span>ebuli\u00e7\u00e3o nucleada<\/span><\/strong><span>\u00a0na superf\u00edcie interrompe efetivamente a camada estagnada e, portanto, a ebuli\u00e7\u00e3o nucleada aumenta significativamente a capacidade de uma superf\u00edcie de transferir\u00a0<\/span><a href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/what-is-energy-physics\/internal-energy-thermal-energy\/\"><span>energia t\u00e9rmica<\/span><\/a><span>\u00a0para o fluido a granel.\u00a0Como resultado, o coeficiente de transfer\u00eancia de calor por convec\u00e7\u00e3o aumenta significativamente e, portanto, em eleva\u00e7\u00f5es mais altas, a diferen\u00e7a de temperatura (T\u00a0<\/span><sub><span>Zr,\u00a0<\/span><\/sub><sub><span>volume\u00a0<\/span><\/sub><span><sub>1<\/sub>\u00a0&#8211; T\u00a0) diminui significativamente.<\/span><\/p>\n<\/div>\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","protected":false},"excerpt":{"rendered":"<p>Este exemplo mostra como calcular a transfer\u00eancia de calor por convec\u00e7\u00e3o.\u00a0C\u00e1lculo do coeficiente de transfer\u00eancia de calor e da temperatura da superf\u00edcie do revestimento.\u00a0Engenharia T\u00e9rmica Exemplo &#8211; Convec\u00e7\u00e3o &#8211; Temperatura da superf\u00edcie do revestimento Exemplo &#8211; Convec\u00e7\u00e3o &#8211; Problema com Solu\u00e7\u00e3o\u00a0 O\u00a0revestimento \u00e9 a camada externa das barras de combust\u00edvel, situada entre o\u00a0l\u00edquido de arrefecimento\u00a0do\u00a0reator\u00a0e &#8230; <a title=\"Exemplo de convec\u00e7\u00e3o &#8211; Problema com solu\u00e7\u00e3o &#8211; Defini\u00e7\u00e3o\" class=\"read-more\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/exemplo-de-conveccao-problema-com-solucao-definicao\/\" aria-label=\"More on Exemplo de convec\u00e7\u00e3o &#8211; Problema com solu\u00e7\u00e3o &#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>Exemplo de convec\u00e7\u00e3o - Problema com solu\u00e7\u00e3o - Defini\u00e7\u00e3o<\/title>\n<meta name=\"description\" content=\"Este exemplo mostra como calcular a transfer\u00eancia de calor por convec\u00e7\u00e3o. C\u00e1lculo do coeficiente de transfer\u00eancia de calor e da temperatura da superf\u00edcie do revestimento. 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\/exemplo-de-conveccao-problema-com-solucao-definicao\/\" \/>\n<meta property=\"og:locale\" content=\"pt_BR\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Exemplo de convec\u00e7\u00e3o - Problema com solu\u00e7\u00e3o - Defini\u00e7\u00e3o\" \/>\n<meta property=\"og:description\" content=\"Este exemplo mostra como calcular a transfer\u00eancia de calor por convec\u00e7\u00e3o. C\u00e1lculo do coeficiente de transfer\u00eancia de calor e da temperatura da superf\u00edcie do revestimento. Engenharia T\u00e9rmica\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.thermal-engineering.org\/pt-br\/exemplo-de-conveccao-problema-com-solucao-definicao\/\" \/>\n<meta property=\"og:site_name\" content=\"Thermal Engineering\" \/>\n<meta property=\"article:published_time\" content=\"2019-11-05T00:48:39+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2020-01-23T13:34:05+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Convection-Convective-Heat-Transfer-example-275x300.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=\"5 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\/exemplo-de-conveccao-problema-com-solucao-definicao\/#primaryimage\",\"inLanguage\":\"pt-BR\",\"url\":\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Convection-Convective-Heat-Transfer-example-275x300.png\"},{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.thermal-engineering.org\/pt-br\/exemplo-de-conveccao-problema-com-solucao-definicao\/#webpage\",\"url\":\"https:\/\/www.thermal-engineering.org\/pt-br\/exemplo-de-conveccao-problema-com-solucao-definicao\/\",\"name\":\"Exemplo de convec\\u00e7\\u00e3o - Problema com solu\\u00e7\\u00e3o - Defini\\u00e7\\u00e3o\",\"isPartOf\":{\"@id\":\"https:\/\/www.thermal-engineering.org\/fr\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\/\/www.thermal-engineering.org\/pt-br\/exemplo-de-conveccao-problema-com-solucao-definicao\/#primaryimage\"},\"datePublished\":\"2019-11-05T00:48:39+00:00\",\"dateModified\":\"2020-01-23T13:34:05+00:00\",\"author\":{\"@id\":\"https:\/\/www.thermal-engineering.org\/fr\/#\/schema\/person\/e8c544db9afedaec8574d6464f9398bb\"},\"description\":\"Este exemplo mostra como calcular a transfer\\u00eancia de calor por convec\\u00e7\\u00e3o. C\\u00e1lculo do coeficiente de transfer\\u00eancia de calor e da temperatura da superf\\u00edcie do revestimento. Engenharia T\\u00e9rmica\",\"inLanguage\":\"pt-BR\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/www.thermal-engineering.org\/pt-br\/exemplo-de-conveccao-problema-com-solucao-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\/47459"}],"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=47459"}],"version-history":[{"count":0,"href":"https:\/\/www.thermal-engineering.org\/pt-br\/wp-json\/wp\/v2\/posts\/47459\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.thermal-engineering.org\/pt-br\/wp-json\/wp\/v2\/media?parent=47459"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.thermal-engineering.org\/pt-br\/wp-json\/wp\/v2\/categories?post=47459"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.thermal-engineering.org\/pt-br\/wp-json\/wp\/v2\/tags?post=47459"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}