{"id":47703,"date":"2019-11-06T01:25:49","date_gmt":"2019-11-06T00:25:49","guid":{"rendered":"https:\/\/www.thermal-engineering.org\/o-que-e-o-valor-r-fator-de-isolamento-termico-definicao\/"},"modified":"2020-01-24T17:19:42","modified_gmt":"2020-01-24T16:19:42","slug":"o-que-e-o-valor-r-fator-de-isolamento-termico-definicao","status":"publish","type":"post","link":"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-o-valor-r-fator-de-isolamento-termico-definicao\/","title":{"rendered":"O que \u00e9 o valor R &#8211; Fator de isolamento t\u00e9rmico &#8211; Defini\u00e7\u00e3o"},"content":{"rendered":"<div class=\"su-quote su-quote-style-default\">\n<div class=\"su-quote-inner su-clearfix\">O valor R, o fator de isolamento t\u00e9rmico, \u00e9 uma medida da resist\u00eancia t\u00e9rmica.\u00a0Quanto maior o valor R, maior a efic\u00e1cia do isolamento. A isola\u00e7\u00e3o t\u00e9rmica possui as unidades [(m2.K) \/ W]<\/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>Valor R &#8211; Fator de isolamento t\u00e9rmico<\/h2>\n<p><strong>A resist\u00eancia t\u00e9rmica<\/strong>\u00a0\u00e9 uma propriedade de calor e uma medi\u00e7\u00e3o de uma diferen\u00e7a de temperatura pela qual um objeto ou material resiste ao fluxo de calor.\u00a0A resist\u00eancia t\u00e9rmica para condu\u00e7\u00e3o em uma parede plana \u00e9 definida como:<\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/thermal-resistance-definition.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20119 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/thermal-resistance-definition.png\" alt=\"resist\u00eancia t\u00e9rmica - defini\u00e7\u00e3o\" width=\"260\" height=\"170\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/thermal-resistance-definition.png\" \/><\/a><\/p>\n<p>Como o conceito de\u00a0<strong>resist\u00eancia t\u00e9rmica<\/strong>\u00a0pode ser usado em uma variedade de ramos de engenharia, definimos:<\/p>\n<ul>\n<li><strong>Resist\u00eancia t\u00e9rmica absoluta<\/strong>\u00a0,\u00a0<strong>R\u00a0<\/strong><strong><sub>t<\/sub><\/strong>\u00a0, que possui unidades de [K \/ W].\u00a0A resist\u00eancia t\u00e9rmica absoluta \u00e9 uma propriedade de um componente em particular, que definiu a geometria (espessura &#8211; L, \u00e1rea &#8211; A e forma).\u00a0Por exemplo, uma caracter\u00edstica de um trocador de calor definido.\u00a0Apenas uma diferen\u00e7a de temperatura \u00e9 necess\u00e1ria para resolver o calor transferido.<\/li>\n<li><strong>Resist\u00eancia t\u00e9rmica<\/strong>\u00a0espec\u00edfica ou resistividade t\u00e9rmica espec\u00edfica,\u00a0<strong>R\u00a0<sub>\u03bb<\/sub><\/strong>\u00a0, que possui unidades de [(K \u00b7 m) \/ W].\u00a0T\u00e9rmica espec\u00edfica \u00e9 uma constante do material.\u00a0A espessura do material e uma diferen\u00e7a de temperatura s\u00e3o necess\u00e1rias para resolver o calor transferido.<\/li>\n<li><strong>R-valor<\/strong>\u00a0.\u00a0O valor R (fator de isolamento t\u00e9rmico) \u00e9 uma medida de resist\u00eancia t\u00e9rmica.\u00a0Quanto maior o valor R, maior a efic\u00e1cia do isolamento.\u00a0A isola\u00e7\u00e3o t\u00e9rmica possui as unidades [(m\u00a0<sup>2<\/sup>\u00a0.K) \/ W] em unidades SI ou [(p\u00e9s\u00a0<sup>2<\/sup>\u00a0\u00b0 F \u00b7 h) \/ Btu] em unidades imperiais.\u00a0\u00c9 a resist\u00eancia t\u00e9rmica da \u00e1rea unit\u00e1ria de um material.\u00a0O valor R depende do tipo de isolamento, sua espessura e densidade.\u00a0\u00c9 necess\u00e1ria uma diferen\u00e7a de \u00e1rea e temperatura para resolver o calor transferido.<\/li>\n<\/ul>\n<h2>Valor R<\/h2>\n<p>A ind\u00fastria da constru\u00e7\u00e3o utiliza unidades como o\u00a0\u00a0<strong>valor R (resist\u00eancia)<\/strong>\u00a0, que \u00e9 expresso como a espessura do material normalizado para a condutividade t\u00e9rmica e, em condi\u00e7\u00f5es uniformes, \u00e9 a raz\u00e3o da diferen\u00e7a de temperatura entre um isolador e o calor densidade de fluxo atrav\u00e9s dele: R (x) = \u2206T \/ q.\u00a0Quanto maior o valor R, mais um material impede a transfer\u00eancia de calor.\u00a0Como pode ser visto, a resist\u00eancia depende da espessura do produto.<\/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>Resist\u00eancia t\u00e9rmica &#8211; Resistividade t\u00e9rmica<\/h2>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/thermal-resistance-definition-analogy.png\"><img loading=\"lazy\" class=\"alignright size-medium wp-image-20125 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/thermal-resistance-definition-analogy-243x300.png\" alt=\"resist\u00eancia t\u00e9rmica - defini\u00e7\u00e3o - analogia\" width=\"243\" height=\"300\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/thermal-resistance-definition-analogy-243x300.png\" \/><\/a>Na engenharia, outro conceito muito importante \u00e9 frequentemente usado.\u00a0Como existe uma\u00a0<strong>analogia<\/strong>\u00a0entre a\u00a0<strong>difus\u00e3o do calor<\/strong>\u00a0e\u00a0<strong>a carga el\u00e9trica<\/strong>\u00a0, os engenheiros costumam usar a\u00a0<strong>resist\u00eancia t\u00e9rmica<\/strong>\u00a0(isto \u00e9, a resist\u00eancia t\u00e9rmica contra a condu\u00e7\u00e3o de calor) para calcular a transfer\u00eancia de calor atrav\u00e9s dos materiais.\u00a0<strong>A resist\u00eancia t\u00e9rmica<\/strong>\u00a0\u00e9 o inverso da condut\u00e2ncia t\u00e9rmica.\u00a0Assim como uma resist\u00eancia el\u00e9trica est\u00e1 associada \u00e0 condu\u00e7\u00e3o de eletricidade, uma resist\u00eancia t\u00e9rmica pode estar associada \u00e0 condu\u00e7\u00e3o de calor.<\/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>Considere uma parede plana de espessura L e condutividade t\u00e9rmica m\u00e9dia k.\u00a0As duas superf\u00edcies da parede s\u00e3o mantidos a temperaturas constantes de T\u00a0<\/span><sub><span>1<\/span><\/sub><span>\u00a0e T\u00a0<\/span><sub><span>2<\/span><\/sub><span>\u00a0.\u00a0Para condu\u00e7\u00e3o de calor constante unidimensional atrav\u00e9s da parede, temos T (x).\u00a0Ent\u00e3o\u00a0<\/span><strong><span>a lei de Fourier<\/span><\/strong><span>\u00a0de\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\/\"><span>condu\u00e7\u00e3o de calor<\/span><\/a><span>\u00a0para a parede pode ser expressa como:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Fourier%E2%80%99s-law-with-thermal-resistance-equation.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20118 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Fourier%E2%80%99s-law-with-thermal-resistance-equation.png\" alt=\"Lei de Fourier com resist\u00eancia t\u00e9rmica\" width=\"398\" height=\"215\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Fourier\u2019s-law-with-thermal-resistance-equation.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>\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>O valor R, o fator de isolamento t\u00e9rmico, \u00e9 uma medida da resist\u00eancia t\u00e9rmica.\u00a0Quanto maior o valor R, maior a efic\u00e1cia do isolamento. A isola\u00e7\u00e3o t\u00e9rmica possui as unidades [(m2.K) \/ W] Valor R &#8211; Fator de isolamento t\u00e9rmico A resist\u00eancia t\u00e9rmica\u00a0\u00e9 uma propriedade de calor e uma medi\u00e7\u00e3o de uma diferen\u00e7a de temperatura pela &#8230; <a title=\"O que \u00e9 o valor R &#8211; Fator de isolamento t\u00e9rmico &#8211; Defini\u00e7\u00e3o\" class=\"read-more\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-o-valor-r-fator-de-isolamento-termico-definicao\/\" aria-label=\"More on O que \u00e9 o valor R &#8211; Fator de isolamento t\u00e9rmico &#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 valor R - Fator de isolamento t\u00e9rmico - Defini\u00e7\u00e3o<\/title>\n<meta name=\"description\" content=\"O valor R, o fator de isolamento t\u00e9rmico, \u00e9 uma medida da resist\u00eancia t\u00e9rmica. 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