{"id":47527,"date":"2019-11-05T07:52:33","date_gmt":"2019-11-05T06:52:33","guid":{"rendered":"https:\/\/www.thermal-engineering.org\/o-que-e-a-formula-do-numero-de-prandtl-definicao\/"},"modified":"2020-01-23T20:03:20","modified_gmt":"2020-01-23T19:03:20","slug":"o-que-e-a-formula-do-numero-de-prandtl-definicao","status":"publish","type":"post","link":"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-a-formula-do-numero-de-prandtl-definicao\/","title":{"rendered":"O que \u00e9 a f\u00f3rmula do n\u00famero de Prandtl – defini\u00e7\u00e3o"},"content":{"rendered":"
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O n\u00famero de Prandtl \u00e9 calculado como a raz\u00e3o entre a difusividade do momento e a difusividade t\u00e9rmica.\u00a0F\u00f3rmula do N\u00famero Prandtl – Equa\u00e7\u00e3o<\/div>\n<\/div>\n
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N\u00famero Prandtl<\/h2>\n

O\u00a0n\u00famero Prandtl<\/strong>\u00a0\u00e9 um n\u00famero sem dimens\u00e3o, nomeado em homenagem ao seu inventor, um engenheiro alem\u00e3o\u00a0Ludwig Prandtl<\/strong>\u00a0, que tamb\u00e9m identificou a\u00a0camada limite<\/a>\u00a0.\u00a0O\u00a0n\u00famero de Prandtl<\/strong>\u00a0\u00e9 definida como a\u00a0raz\u00e3o<\/strong>\u00a0de\u00a0difusividade impulso<\/strong>\u00a0a\u00a0difusividade t\u00e9rmica<\/strong>\u00a0.\u00a0A\u00a0difusividade 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, a\u00a0f\u00f3rmula do n\u00famero Prandtl<\/strong>\u00a0\u00e9 fornecida como:<\/p>\n

\"N\u00famero<\/a><\/p>\n

Onde:<\/p>\n

\u03bd<\/strong>\u00a0\u00e9\u00a0difusividade do momento<\/strong>\u00a0(viscosidade cinem\u00e1tica) [m\u00a02<\/sup>\u00a0\/ s]\n

\u03b1<\/strong>\u00a0\u00e9\u00a0difusividade t\u00e9rmica<\/a><\/strong>\u00a0[m\u00a02<\/sup>\u00a0\/ s]\n

\u03bc<\/strong>\u00a0\u00e9\u00a0viscosidade din\u00e2mica<\/strong>\u00a0[Ns \/ m\u00a02<\/sup>\u00a0]\n

k<\/strong>\u00a0\u00e9\u00a0condutividade t\u00e9rmica<\/strong><\/a>\u00a0[W \/ mK]\n

c\u00a0p<\/sub><\/strong>\u00a0\u00e9\u00a0calor espec\u00edfico<\/strong><\/a>\u00a0[J \/ kg.K]\n

\u03c1<\/strong>\u00a0\u00e9\u00a0densidade<\/a><\/strong>\u00a0[kg \/ m\u00a03<\/sup>\u00a0]\n

Pequenos valores do\u00a0n\u00famero de Prandtl<\/strong>\u00a0,\u00a0Pr << 1<\/strong>\u00a0, significam que a difusividade t\u00e9rmica domina.\u00a0Enquanto que com valores grandes,\u00a0Pr >> 1<\/strong>\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\u00a0condu\u00e7\u00e3o de calor<\/strong><\/a>\u00a0\u00e9 mais significativa em compara\u00e7\u00e3o com a\u00a0convec\u00e7\u00e3o<\/strong>\u00a0, de modo que a difusividade t\u00e9rmica \u00e9 dominante.\u00a0Quando Pr \u00e9 pequeno, significa que o calor se difunde rapidamente em compara\u00e7\u00e3o com a velocidade.<\/p>\n

Em compara\u00e7\u00e3o com o\u00a0n\u00famero de Reynolds<\/a>\u00a0, o\u00a0n\u00famero de Prandtl<\/strong>\u00a0n\u00e3o depende da geometria de um objeto envolvido no problema, mas depende apenas do estado do\u00a0fluido<\/a>\u00a0e do fluido.\u00a0Como tal, o\u00a0n\u00famero de Prandtl<\/strong>\u00a0\u00e9 frequentemente encontrado em tabelas de propriedades, ao lado de outras propriedades, como viscosidade e condutividade t\u00e9rmica.<\/p>\n<\/div>\n<\/div>\n

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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":"

O n\u00famero de Prandtl \u00e9 calculado como a raz\u00e3o entre a difusividade do momento e a difusividade t\u00e9rmica.\u00a0F\u00f3rmula do N\u00famero Prandtl – Equa\u00e7\u00e3o N\u00famero Prandtl O\u00a0n\u00famero Prandtl\u00a0\u00e9 um n\u00famero sem dimens\u00e3o, nomeado em homenagem ao seu inventor, um engenheiro alem\u00e3o\u00a0Ludwig Prandtl\u00a0, que tamb\u00e9m identificou a\u00a0camada limite\u00a0.\u00a0O\u00a0n\u00famero de Prandtl\u00a0\u00e9 definida como a\u00a0raz\u00e3o\u00a0de\u00a0difusividade impulso\u00a0a\u00a0difusividade t\u00e9rmica\u00a0.\u00a0A\u00a0difusividade do momento\u00a0, … 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":"\nO que \u00e9 a f\u00f3rmula do n\u00famero de Prandtl - defini\u00e7\u00e3o<\/title>\n<meta name=\"description\" content=\"O n\u00famero de Prandtl \u00e9 calculado como a raz\u00e3o entre a difusividade do momento e a difusividade t\u00e9rmica. 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