{"id":47535,"date":"2019-11-05T08:31:23","date_gmt":"2019-11-05T07:31:23","guid":{"rendered":"https:\/\/www.thermal-engineering.org\/o-que-e-o-numero-de-metais-liquidos-prandtl-definicao\/"},"modified":"2020-01-23T20:05:53","modified_gmt":"2020-01-23T19:05:53","slug":"o-que-e-o-numero-de-metais-liquidos-prandtl-definicao","status":"publish","type":"post","link":"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-o-numero-de-metais-liquidos-prandtl-definicao\/","title":{"rendered":"O que \u00e9 o n\u00famero de metais l\u00edquidos Prandtl &#8211; Defini\u00e7\u00e3o"},"content":{"rendered":"<div class=\"su-quote su-quote-style-default\">\n<div class=\"su-quote-inner su-clearfix\">N\u00famero Prandtl de metais l\u00edquidos.\u00a0Devido \u00e0 condutividade t\u00e9rmica muito alta, para metais l\u00edquidos, o n\u00famero de Prandtl \u00e9 muito pequeno, geralmente na faixa de 0,01 a 0,001.\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>N\u00famero Prandtl de metais l\u00edquidos<\/h2>\n<p>Para\u00a0<strong>metais l\u00edquidos,<\/strong>\u00a0o\u00a0<strong>n\u00famero de Prandtl<\/strong>\u00a0\u00e9 muito pequeno, geralmente na faixa de\u00a0<strong>0,01 a 0,001.\u00a0<\/strong>Isso significa que a\u00a0<a title=\"Difusividade t\u00e9rmica\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-difusividade-termica-definicao\/\"><strong>difusividade t\u00e9rmica<\/strong><\/a>\u00a0, que est\u00e1 relacionada \u00e0 taxa de\u00a0<strong><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\/\">transfer\u00eancia<\/a><\/strong>\u00a0de\u00a0<strong><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\/\">calor por condu\u00e7\u00e3o<\/a><\/strong>\u00a0,\u00a0<strong>domina<\/strong>\u00a0sem ambiguidade\u00a0.\u00a0Essa difusividade t\u00e9rmica muito alta resulta da condutividade t\u00e9rmica muito alta dos metais, que \u00e9 cerca de 100 vezes maior que a da \u00e1gua.\u00a0O\u00a0<strong>n\u00famero de Prandtl<\/strong>\u00a0para s\u00f3dio a uma temperatura de opera\u00e7\u00e3o t\u00edpica nos reatores r\u00e1pidos resfriados a s\u00f3dio \u00e9 de cerca de 0,004.<\/p>\n<p>O\u00a0<strong>n\u00famero de Prandtl<\/strong>\u00a0entra em muitos c\u00e1lculos de transfer\u00eancia de calor em reatores de metal l\u00edquido.\u00a0Dois dos projetos promissores dos reatores da gera\u00e7\u00e3o IV usam um metal l\u00edquido como refrigerante do reator.\u00a0O desenvolvimento de reatores da gera\u00e7\u00e3o IV representa um desafio do ponto de vista da engenharia.<\/p>\n<ul>\n<li>Reator r\u00e1pido resfriado a s\u00f3dio<\/li>\n<li>Reator r\u00e1pido resfriado a chumbo<\/li>\n<\/ul>\n<p>Um dos principais desafios da simula\u00e7\u00e3o num\u00e9rica \u00e9 a modelagem confi\u00e1vel de transfer\u00eancia de calor em reatores refrigerados a metal l\u00edquido pelo Computational Fluid Dynamics (CFD).\u00a0As aplica\u00e7\u00f5es de transfer\u00eancia de calor com\u00a0<strong>fluidos<\/strong>\u00a0com\u00a0<strong>baixo n\u00famero de Prandtl est\u00e3o<\/strong>\u00a0frequentemente na faixa de transi\u00e7\u00e3o entre regimes dominados por condu\u00e7\u00e3o e convec\u00e7\u00e3o.<\/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>N\u00famero Prandtl<\/h2>\n<p>O\u00a0<strong>n\u00famero Prandtl<\/strong>\u00a0\u00e9 um n\u00famero sem dimens\u00e3o, nomeado em homenagem ao seu inventor, um engenheiro alem\u00e3o\u00a0<strong>Ludwig Prandtl<\/strong>\u00a0, que tamb\u00e9m identificou a\u00a0<a title=\"Camada limite\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-camada-de-limite-definicao\/\">camada limite<\/a>\u00a0.\u00a0O\u00a0<strong>n\u00famero de Prandtl<\/strong>\u00a0\u00e9 definida como a\u00a0<strong>raz\u00e3o<\/strong>\u00a0de\u00a0<strong>difusividade impulso<\/strong>\u00a0a\u00a0<strong>difusividade t\u00e9rmica<\/strong>\u00a0.\u00a0A\u00a0<strong>difusividade do momento<\/strong>\u00a0, ou como \u00e9 normalmente chamada, viscosidade cinem\u00e1tica, indica a resist\u00eancia do material aos fluxos de cisalhamento (diferentes camadas do fluxo viajam com velocidades diferentes devido, por exemplo, a diferentes velocidades das paredes adjacentes) em rela\u00e7\u00e3o \u00e0 densidade.\u00a0Ou seja, o\u00a0<strong>n\u00famero Prandtl<\/strong>\u00a0\u00e9 dado como:<\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Prandtl-Number-definition.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20298 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Prandtl-Number-definition.png\" alt=\"N\u00famero Prandtl\" width=\"767\" height=\"394\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Prandtl-Number-definition.png\" \/><\/a><\/p>\n<p><span>Onde:<\/span><\/p>\n<p><strong><span>\u03bd<\/span><\/strong><span>\u00a0\u00e9\u00a0<\/span><strong><span>difusividade do momento<\/span><\/strong><span>\u00a0(viscosidade cinem\u00e1tica) [m\u00a0<\/span><sup><span>2<\/span><\/sup><span>\u00a0\/ s]<\/span><\/p>\n<p><strong><span>\u03b1<\/span><\/strong><span>\u00a0\u00e9\u00a0<\/span><strong><a title=\"Difusividade t\u00e9rmica\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-difusividade-termica-definicao\/\"><span>difusividade t\u00e9rmica<\/span><\/a><\/strong><span>\u00a0[m\u00a0<\/span><sup><span>2<\/span><\/sup><span>\u00a0\/ s]<\/span><\/p>\n<p><strong><span>\u03bc<\/span><\/strong><span>\u00a0\u00e9\u00a0<\/span><strong><span>viscosidade din\u00e2mica<\/span><\/strong><span>\u00a0[Ns \/ m\u00a0<\/span><sup><span>2<\/span><\/sup><span>\u00a0]<\/span><\/p>\n<p><strong><span>k<\/span><\/strong><span>\u00a0\u00e9\u00a0<\/span><a title=\"Condutividade t\u00e9rmica\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-condutividade-termica-definicao\/\"><strong><span>condutividade t\u00e9rmica<\/span><\/strong><\/a><span>\u00a0[W \/ mK]<\/span><\/p>\n<p><strong><span>c\u00a0<\/span><sub><span>p<\/span><\/sub><\/strong><span>\u00a0\u00e9\u00a0<\/span><a title=\"Capacidade t\u00e9rmica - Capacidade t\u00e9rmica espec\u00edfica\" 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[J \/ kg.K]<\/span><\/p>\n<p><strong><span>\u03c1<\/span><\/strong><span>\u00a0\u00e9\u00a0<\/span><strong><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><\/strong><span>\u00a0[kg \/ m\u00a0<\/span><sup><span>3<\/span><\/sup><span>\u00a0]<\/span><\/p>\n<p><span>Pequenos valores do\u00a0<\/span><strong><span>n\u00famero de Prandtl<\/span><\/strong><span>\u00a0,\u00a0<\/span><strong><span>Pr &lt;&lt; 1<\/span><\/strong><span>\u00a0, significam que a difusividade t\u00e9rmica domina.\u00a0Enquanto que com valores grandes,\u00a0<\/span><strong><span>Pr &gt;&gt; 1<\/span><\/strong><span>\u00a0, a difusividade do momento domina o comportamento.\u00a0Por exemplo, o valor t\u00edpico de merc\u00fario l\u00edquido, que \u00e9 de cerca de 0,025, indica que a\u00a0<\/span><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><span>condu\u00e7\u00e3o de calor<\/span><\/strong><\/a><span>\u00a0\u00e9 mais significativa em compara\u00e7\u00e3o com a\u00a0<\/span><strong><span>convec\u00e7\u00e3o<\/span><\/strong><span>\u00a0, portanto a difusividade t\u00e9rmica \u00e9 dominante.\u00a0Quando Pr \u00e9 pequeno, significa que o calor se difunde rapidamente em compara\u00e7\u00e3o com a velocidade.<\/span><\/p>\n<p><span>Em compara\u00e7\u00e3o com 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, o\u00a0<\/span><strong><span>n\u00famero de Prandtl<\/span><\/strong><span>\u00a0n\u00e3o depende da geometria de um objeto envolvido no problema, mas depende apenas do estado do\u00a0<\/span><a title=\"Defini\u00e7\u00e3o de Fluido\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/definition-of-fluid\/\"><span>fluido<\/span><\/a><span>\u00a0e do fluido.\u00a0Como tal, o\u00a0<\/span><strong><span>n\u00famero de Prandtl<\/span><\/strong><span>\u00a0\u00e9 freq\u00fcentemente encontrado em tabelas de propriedades, ao lado de outras propriedades, como viscosidade e condutividade t\u00e9rmica.<\/span><\/p>\n<\/div>\n<\/div>\n<p>&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;.<\/p>\n<p>Este artigo \u00e9 baseado na tradu\u00e7\u00e3o autom\u00e1tica do artigo original em ingl\u00eas. Para mais informa\u00e7\u00f5es, consulte o artigo em ingl\u00eas. Voc\u00ea pode nos ajudar. Se voc\u00ea deseja corrigir a tradu\u00e7\u00e3o, envie-a para: translations@nuclear-power.com ou preencha o formul\u00e1rio de tradu\u00e7\u00e3o on-line. Agradecemos sua ajuda, atualizaremos a tradu\u00e7\u00e3o o mais r\u00e1pido poss\u00edvel. Obrigado.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>N\u00famero Prandtl de metais l\u00edquidos.\u00a0Devido \u00e0 condutividade t\u00e9rmica muito alta, para metais l\u00edquidos, o n\u00famero de Prandtl \u00e9 muito pequeno, geralmente na faixa de 0,01 a 0,001.\u00a0Engenharia T\u00e9rmica N\u00famero Prandtl de metais l\u00edquidos Para\u00a0metais l\u00edquidos,\u00a0o\u00a0n\u00famero de Prandtl\u00a0\u00e9 muito pequeno, geralmente na faixa de\u00a00,01 a 0,001.\u00a0Isso significa que a\u00a0difusividade t\u00e9rmica\u00a0, que est\u00e1 relacionada \u00e0 taxa de\u00a0transfer\u00eancia\u00a0de\u00a0calor &#8230; <a title=\"O que \u00e9 o n\u00famero de metais l\u00edquidos Prandtl &#8211; Defini\u00e7\u00e3o\" class=\"read-more\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-o-numero-de-metais-liquidos-prandtl-definicao\/\" aria-label=\"More on O que \u00e9 o n\u00famero de metais l\u00edquidos Prandtl &#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 o n\u00famero de metais l\u00edquidos Prandtl - Defini\u00e7\u00e3o<\/title>\n<meta name=\"description\" content=\"N\u00famero Prandtl de metais l\u00edquidos. 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