{"id":47575,"date":"2019-11-05T12:05:47","date_gmt":"2019-11-05T11:05:47","guid":{"rendered":"https:\/\/www.thermal-engineering.org\/o-que-e-conveccao-definicao\/"},"modified":"2020-01-24T10:36:22","modified_gmt":"2020-01-24T09:36:22","slug":"o-que-e-conveccao-definicao","status":"publish","type":"post","link":"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-conveccao-definicao\/","title":{"rendered":"O que \u00e9 convec\u00e7\u00e3o – defini\u00e7\u00e3o"},"content":{"rendered":"
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O que \u00e9 Convec\u00e7\u00e3o – Defini\u00e7\u00e3o de Convec\u00e7\u00e3o.\u00a0A convec\u00e7\u00e3o ocorre atrav\u00e9s de advec\u00e7\u00e3o, difus\u00e3o ou ambos.\u00a0A convec\u00e7\u00e3o n\u00e3o pode ocorrer na maioria dos s\u00f3lidos<\/div>\n<\/div>\n
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O que \u00e9 convec\u00e7\u00e3o<\/h2>\n

\"Convec\u00e7\u00e3o<\/a><\/p>\n

O que \u00e9 convec\u00e7\u00e3o<\/strong><\/p>\n

Em geral, a\u00a0convec\u00e7\u00e3o<\/strong>\u00a0\u00e9 a\u00a0transfer\u00eancia de massa<\/strong>\u00a0ou a\u00a0transfer\u00eancia de calor<\/strong>\u00a0devido ao\u00a0movimento em massa<\/strong>\u00a0de mol\u00e9culas dentro de fluidos, como gases e l\u00edquidos.\u00a0Embora l\u00edquidos e gases geralmente n\u00e3o sejam bons condutores de calor, eles podem transferir calor rapidamente\u00a0por convec\u00e7\u00e3o<\/strong>\u00a0.<\/p>\n

A convec\u00e7\u00e3o<\/strong>\u00a0ocorre atrav\u00e9s de\u00a0advec\u00e7\u00e3o<\/strong>\u00a0,\u00a0difus\u00e3o<\/strong>\u00a0ou ambos.\u00a0A convec\u00e7\u00e3o n\u00e3o pode ocorrer na maioria dos s\u00f3lidos, porque nem a difus\u00e3o significativa da mat\u00e9ria nem os fluxos de corrente a granel podem ocorrer.\u00a0A difus\u00e3o do calor ocorre em s\u00f3lidos r\u00edgidos, mas isso \u00e9 chamado\u00a0de condu\u00e7\u00e3o t\u00e9rmica<\/a>\u00a0.<\/p>\n

O processo de transfer\u00eancia de calor entre uma superf\u00edcie e um fluido que flui em contato com ela \u00e9 chamado de\u00a0transfer\u00eancia de calor por convec\u00e7\u00e3o<\/strong>\u00a0.\u00a0Na engenharia, a transfer\u00eancia de calor por convec\u00e7\u00e3o \u00e9 um dos principais mecanismos de\u00a0transfer\u00eancia<\/strong><\/a>\u00a0de\u00a0calor<\/strong><\/a>\u00a0.\u00a0Quando o calor \u00e9 transferido de um fluido para outro atrav\u00e9s de uma barreira, a convec\u00e7\u00e3o \u00e9 envolvida em ambos os lados da barreira.\u00a0Na maioria dos casos, a principal\u00a0resist\u00eancia<\/a>\u00a0ao fluxo de calor \u00e9 por convec\u00e7\u00e3o.\u00a0A transfer\u00eancia de calor por convec\u00e7\u00e3o<\/strong>\u00a0ocorre tanto por difus\u00e3o t\u00e9rmica (o movimento aleat\u00f3rio das mol\u00e9culas de fluido) quanto por advec\u00e7\u00e3o, na qual a mat\u00e9ria ou o calor \u00e9 transportado pelo movimento em larga escala das correntes no fluido.<\/p>\n<\/div>\n<\/div>\n

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Mecanismo de Convec\u00e7\u00e3o<\/h2>\n

Na\u00a0condu\u00e7\u00e3o t\u00e9rmica<\/strong><\/a>\u00a0, a\u00a0energia<\/a>\u00a0\u00e9 transferida como\u00a0calor<\/a>\u00a0devido \u00e0\u00a0migra\u00e7\u00e3o de el\u00e9trons livres<\/strong>\u00a0ou\u00a0ondas vibracionais em treli\u00e7a (\u00a0f\u00f4nons<\/a>\u00a0).\u00a0<\/strong>N\u00e3o h\u00e1 movimento de massa na dire\u00e7\u00e3o do fluxo de energia.\u00a0A transfer\u00eancia de calor<\/a>\u00a0por\u00a0condu\u00e7\u00e3o<\/strong>\u00a0depende da \u201cfor\u00e7a\u201d motriz da\u00a0diferen\u00e7a<\/strong>\u00a0de\u00a0temperatura.\u00a0<\/strong>A condu\u00e7\u00e3o<\/strong>\u00a0e a\u00a0convec\u00e7\u00e3o<\/strong>\u00a0s\u00e3o semelhantes, pois ambos os mecanismos requerem a presen\u00e7a de um meio material (em compara\u00e7\u00e3o com a radia\u00e7\u00e3o t\u00e9rmica).\u00a0Por outro lado, eles s\u00e3o diferentes, pois a convec\u00e7\u00e3o requer a presen\u00e7a de movimento fluido.<\/p>\n

Deve-se enfatizar que\u00a0, na superf\u00edcie,<\/strong>\u00a0o fluxo de energia ocorre\u00a0\u00a0puramente por condu\u00e7\u00e3o,<\/strong>\u00a0mesmo em condu\u00e7\u00e3o.\u00a0Isso ocorre porque sempre h\u00e1 uma\u00a0fina camada de filme estagnado\u00a0na superf\u00edcie da transfer\u00eancia de calor.\u00a0<\/strong>\u00a0Por\u00e9m, nas pr\u00f3ximas camadas, ocorrem movimentos de condu\u00e7\u00e3o e difus\u00e3o-massa no n\u00edvel molecular ou no n\u00edvel macrosc\u00f3pico.\u00a0Devido ao movimento de massa, a taxa de transfer\u00eancia de energia \u00e9 maior.\u00a0Quanto maior a taxa de movimento de massa, mais fina ser\u00e1 a camada de filme fluido estagnado e maior ser\u00e1 a taxa de fluxo de calor.<\/p>\n

Deve-se notar que a\u00a0ebuli\u00e7\u00e3o nucleada<\/strong>\u00a0na superf\u00edcie interrompe efetivamente essa camada estagnada e, portanto, a ebuli\u00e7\u00e3o nucleada aumenta significativamente a capacidade de uma superf\u00edcie de transferir energia t\u00e9rmica para o fluido a granel.<\/p>\n

Como foi escrito, a transfer\u00eancia de calor atrav\u00e9s de um fluido \u00e9 por convec\u00e7\u00e3o na presen\u00e7a de movimento de massa e por condu\u00e7\u00e3o na aus\u00eancia dele.\u00a0Portanto, a condu\u00e7\u00e3o t\u00e9rmica em um fluido pode ser vista como o caso limitador de convec\u00e7\u00e3o, correspondendo ao caso de fluido inativo.<\/p>\n<\/div>\n<\/div>\n

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Lei de Newton de resfriamento<\/span><\/h2>\n

Apesar da complexidade da\u00a0<\/span>convec\u00e7\u00e3o<\/span><\/strong>\u00a0, a taxa de transfer\u00eancia de calor por convec\u00e7\u00e3o \u00e9 observada\u00a0<\/span>proporcional<\/span><\/strong>\u00a0\u00e0\u00a0<\/span>diferen\u00e7a de temperatura<\/span><\/strong>\u00a0e \u00e9 convenientemente expressa pela\u00a0<\/span>lei do resfriamento de Newton<\/span><\/strong>\u00a0, que afirma que:<\/span><\/p>\n

A taxa de perda de calor de um corpo \u00e9 diretamente proporcional \u00e0 diferen\u00e7a de temperatura entre o corpo e seus arredores, desde que a diferen\u00e7a de temperatura seja pequena e a natureza da superf\u00edcie radiante permane\u00e7a a mesma.<\/span><\/em><\/p>\n

\"lei<\/a><\/p>\n

Observe que\u00a0<\/span>\u0394T<\/span><\/strong>\u00a0\u00e9 dado pela\u00a0<\/span>temperatura<\/span><\/strong>\u00a0da superf\u00edcie ou da\u00a0parede<\/strong>\u00a0,\u00a0parede<\/sub><\/strong><\/span>\u00a0T<\/span>\u00a0<\/strong>e\u00a0<\/span>temperatura<\/span><\/strong>\u00a0do\u00a0volume<\/strong>\u00a0,\u00a0<\/span>T\u00a0<\/span>\u221e<\/span><\/sub><\/strong>\u00a0, que \u00e9 a temperatura do fluido suficientemente longe da superf\u00edcie.<\/span><\/p>\n<\/div>\n<\/div>\n

……………………………………………………………………………………………………………………………….<\/p>\n

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":"

O que \u00e9 Convec\u00e7\u00e3o – Defini\u00e7\u00e3o de Convec\u00e7\u00e3o.\u00a0A convec\u00e7\u00e3o ocorre atrav\u00e9s de advec\u00e7\u00e3o, difus\u00e3o ou ambos.\u00a0A convec\u00e7\u00e3o n\u00e3o pode ocorrer na maioria dos s\u00f3lidos O que \u00e9 convec\u00e7\u00e3o O que \u00e9 convec\u00e7\u00e3o Em geral, a\u00a0convec\u00e7\u00e3o\u00a0\u00e9 a\u00a0transfer\u00eancia de massa\u00a0ou a\u00a0transfer\u00eancia de calor\u00a0devido ao\u00a0movimento em massa\u00a0de mol\u00e9culas dentro de fluidos, como gases e l\u00edquidos.\u00a0Embora l\u00edquidos e gases … 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 convec\u00e7\u00e3o - defini\u00e7\u00e3o<\/title>\n<meta name=\"description\" content=\"O que \u00e9 Convec\u00e7\u00e3o - Defini\u00e7\u00e3o de Convec\u00e7\u00e3o. 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