{"id":46917,"date":"2019-11-02T14:23:44","date_gmt":"2019-11-02T13:23:44","guid":{"rendered":"https:\/\/www.thermal-engineering.org\/o-que-e-isolamento-de-algodao-definicao\/"},"modified":"2020-01-22T09:45:59","modified_gmt":"2020-01-22T08:45:59","slug":"o-que-e-isolamento-de-algodao-definicao","status":"publish","type":"post","link":"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-isolamento-de-algodao-definicao\/","title":{"rendered":"O que \u00e9 isolamento de algod\u00e3o – Defini\u00e7\u00e3o"},"content":{"rendered":"
\n
O isolamento otton consiste em 85% de algod\u00e3o reciclado e 15% de fibras pl\u00e1sticas.\u00a0Da mesma forma que na celulose, para tornar o isolamento do algod\u00e3o retardador de chamas, o algod\u00e3o deve ser impregnado.\u00a0Engenharia T\u00e9rmica<\/div>\n<\/div>\n
<\/div>\n
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<\/div>\n

Isolamento de algod\u00e3o<\/h2>\n

O isolamento de algod\u00e3o \u00e9 feito de t\u00eaxteis de algod\u00e3o reciclado p\u00f3s-industrial.\u00a0O isolamento do algod\u00e3o consiste em 85% de algod\u00e3o reciclado e 15% de fibras pl\u00e1sticas.\u00a0Da mesma forma que na celulose, para tornar o isolamento do algod\u00e3o retardador de chamas, o algod\u00e3o deve ser impregnado.<\/p>\n<\/div>\n<\/div>\n

 <\/p>\n

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Condutividade t\u00e9rmica do isolamento de algod\u00e3o<\/span><\/h2>\n

\"Isoladores<\/a>Condutividade t\u00e9rmica<\/span><\/a>\u00a0\u00e9 definida como a quantidade de\u00a0<\/span>calor<\/span><\/a>\u00a0(em watts) transferida atrav\u00e9s de uma \u00e1rea quadrada de material de determinada espessura (em metros) devido a uma diferen\u00e7a de\u00a0<\/span>temperatura<\/span><\/a>\u00a0.\u00a0Quanto menor a condutividade t\u00e9rmica do material, maior a capacidade do material de resistir \u00e0 transfer\u00eancia de calor e, portanto, maior a efic\u00e1cia do isolamento.\u00a0<\/span>Os valores t\u00edpicos de condutividade t\u00e9rmica<\/span><\/strong>\u00a0para o\u00a0<\/span>isolamento de algod\u00e3o\u00a0<\/span><\/strong>\u00a0\u00e9 de cerca de\u00a0\u00a0<\/span>0.035W \/ m \u2219 K<\/span><\/strong>\u00a0.<\/span><\/p>\n

Em geral, o\u00a0<\/span>isolamento t\u00e9rmico<\/span><\/a>\u00a0\u00e9 baseado principalmente na\u00a0<\/span>condutividade t\u00e9rmica<\/span><\/a>\u00a0muito baixa\u00a0dos gases<\/a>\u00a0.\u00a0Os gases possuem m\u00e1s propriedades de condu\u00e7\u00e3o t\u00e9rmica em compara\u00e7\u00e3o com l\u00edquidos e s\u00f3lidos e, portanto, s\u00e3o um bom material para isolamento se puderem ser presos (por exemplo, em uma estrutura semelhante a espuma).\u00a0Ar e outros gases geralmente s\u00e3o bons isolantes.\u00a0Mas o principal benef\u00edcio \u00e9 na aus\u00eancia de convec\u00e7\u00e3o.\u00a0Portanto, muitos materiais isolantes (por exemplo,\u00a0<\/span>isolamento de algod\u00e3o<\/span><\/strong>\u00a0) funcionam simplesmente com um grande n\u00famero de\u00a0<\/span>bolsas cheias<\/span><\/strong>\u00a0de\u00a0g\u00e1s<\/strong>\u00a0que\u00a0<\/span>impedem a convec\u00e7\u00e3o em grande escala<\/span><\/strong>\u00a0.<\/span><\/p>\n

A altern\u00e2ncia entre bolsa de g\u00e1s e material s\u00f3lido faz com que o calor seja transferido atrav\u00e9s de muitas interfaces, causando uma r\u00e1pida diminui\u00e7\u00e3o no coeficiente de transfer\u00eancia de calor.<\/span><\/p>\n<\/div>\n<\/div>\n

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Exemplo – Isolamento de Algod\u00e3o<\/span><\/h2>\n

\"perda<\/a>Uma das principais fontes de\u00a0<\/span>perda<\/span><\/strong>\u00a0de\u00a0calor<\/strong>\u00a0de uma casa \u00e9 atrav\u00e9s das paredes.\u00a0Calcule a taxa de\u00a0<\/span>fluxo<\/span><\/a>\u00a0de\u00a0calor<\/a>\u00a0atrav\u00e9s de uma parede com 3 mx 10 m de \u00e1rea (A = 30 m\u00a0<\/span>2<\/span><\/sup>\u00a0).\u00a0A parede tem 15 cm de espessura (L\u00a0<\/span>1<\/span><\/sub>\u00a0) e \u00e9 feita de tijolos com\u00a0<\/span>condutividade t\u00e9rmica<\/span><\/a>\u00a0de k\u00a0<\/span>1<\/span><\/sub>\u00a0= 1,0 W \/ mK (isolador t\u00e9rmico ruim).\u00a0Suponha que as\u00a0<\/span>temperaturas<\/span><\/a>\u00a0interna e externa\u00a0sejam 22 \u00b0 C e -8 \u00b0 C, e os\u00a0<\/span>coeficientes de transfer\u00eancia de calor por convec\u00e7\u00e3o<\/span><\/a>\u00a0nos lados interno e externo sejam h\u00a0<\/span>1<\/span><\/sub>\u00a0= 10 W \/ m\u00a0<\/span>2<\/span><\/sup>\u00a0K e h\u00a0<\/span>2<\/span><\/sub>\u00a0= 30 W \/ m\u00a0<\/span>2<\/span><\/sup>K, respectivamente.\u00a0Observe que esses coeficientes de convec\u00e7\u00e3o dependem muito das condi\u00e7\u00f5es ambientais e interiores (vento, umidade etc.).<\/span><\/p>\n

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  1. Calcule o fluxo de calor (\u00a0<\/span>perda de calor<\/span><\/strong><\/a>\u00a0) atrav\u00e9s desta parede n\u00e3o isolada.<\/span><\/li>\n
  2. Agora assuma o\u00a0<\/span>isolamento t\u00e9rmico<\/span><\/strong>\u00a0no lado externo desta parede.\u00a0Use\u00a0<\/span>isolamento de algod\u00e3o com\u00a0<\/span><\/strong>\u00a010 cm de espessura (L\u00a0<\/span>2<\/span><\/sub>\u00a0) com a condutividade t\u00e9rmica de k\u00a0<\/span>2<\/span><\/sub>\u00a0= 0,04 W \/ mK e calcule o fluxo de\u00a0<\/span>calor<\/span><\/strong><\/a>\u00a0(\u00a0perda de calor<\/strong><\/a>\u00a0) atrav\u00e9s dessa parede composta.<\/span><\/li>\n<\/ol>\n

    Solu\u00e7\u00e3o:<\/span><\/strong><\/p>\n

    Como foi escrito, muitos dos processos de transfer\u00eancia de calor envolvem sistemas compostos e at\u00e9 envolvem uma combina\u00e7\u00e3o de\u00a0<\/span>condu\u00e7\u00e3o<\/span><\/a>\u00a0e\u00a0<\/span>convec\u00e7\u00e3o<\/span><\/a>\u00a0.\u00a0Com estes sistemas compostos, muitas vezes \u00e9 conveniente trabalhar com um\u00a0<\/span>coeficiente de transfer\u00eancia total de calor<\/span><\/a>\u00a0,<\/span><\/strong>\u00a0conhecido como um\u00a0<\/span>factor-L<\/span><\/strong>\u00a0.\u00a0O fator U \u00e9 definido por uma express\u00e3o an\u00e1loga \u00e0\u00a0<\/span>lei do resfriamento de Newton<\/span><\/strong><\/a>\u00a0:<\/span><\/p>\n

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

    O\u00a0<\/span>coeficiente geral de transfer\u00eancia de calor<\/span><\/strong>\u00a0est\u00e1 relacionado \u00e0\u00a0<\/span>resist\u00eancia t\u00e9rmica total<\/span><\/a>\u00a0e depende da geometria do problema.<\/span><\/p>\n

      \n
    1. parede nua<\/span><\/strong><\/li>\n<\/ol>\n

      Assumindo a transfer\u00eancia de calor unidimensional atrav\u00e9s da parede plana e desconsiderando a radia\u00e7\u00e3o, o\u00a0<\/span>coeficiente geral de transfer\u00eancia de calor<\/span><\/strong>\u00a0pode ser calculado como:<\/span><\/p>\n

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

      O\u00a0<\/span>coeficiente geral de transfer\u00eancia de calor<\/span><\/strong>\u00a0\u00e9 ent\u00e3o:<\/span><\/p>\n

      U = 1 \/ (1\/10 + 0,15 \/ 1 + 1\/30) = 3,53 W \/ m\u00a0<\/span>2<\/span><\/sup>\u00a0K<\/span><\/p>\n

      O fluxo de calor pode ser calculado simplesmente como:<\/span><\/p>\n

      q = 3,53 [W \/ m\u00a0<\/span>2<\/span><\/sup>\u00a0K] x 30 [K] = 105,9 W \/ m\u00a0<\/span>2<\/span><\/sup><\/p>\n

      A perda total de calor atrav\u00e9s desta parede ser\u00e1:<\/span><\/p>\n

      q\u00a0<\/span>perda<\/span><\/sub>\u00a0= q.\u00a0A = 105,9 [W \/ m\u00a0<\/span>2<\/span><\/sup>\u00a0] x 30 [m\u00a0<\/span>2<\/span><\/sup>\u00a0] = 3177W<\/span><\/p>\n

        \n
      1. parede comp\u00f3sita com isolamento t\u00e9rmico<\/span><\/strong><\/li>\n<\/ol>\n

        Assumindo a transfer\u00eancia de calor unidimensional atrav\u00e9s da parede composta plana, sem resist\u00eancia ao contato t\u00e9rmico e sem considerar a radia\u00e7\u00e3o, o\u00a0<\/span>coeficiente geral de transfer\u00eancia de calor<\/span><\/strong>\u00a0pode ser calculado como:<\/span><\/p>\n

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

        \"isolamento<\/a>O\u00a0<\/span>coeficiente geral de transfer\u00eancia de calor<\/span><\/strong>\u00a0\u00e9 ent\u00e3o:<\/span><\/p>\n

        U = 1 \/ (1\/10 + 0,15 \/ 1 + 0,1 \/ 0,040 + 1\/30) = 0,359 W \/ m\u00a0<\/span>2<\/span><\/sup>\u00a0K<\/span><\/p>\n

        O fluxo de calor pode ser calculado simplesmente como:<\/span><\/p>\n

        q = 0,359 [W \/ m\u00a0<\/span>2<\/span><\/sup>\u00a0K] x 30 [K] = 10,78 W \/ m\u00a0<\/span>2<\/span><\/sup><\/p>\n

        A perda total de calor atrav\u00e9s desta parede ser\u00e1:<\/span><\/p>\n

        q\u00a0<\/span>perda<\/span><\/sub>\u00a0= q.\u00a0A = 10,78 [W \/ m\u00a0<\/span>2<\/span><\/sup>\u00a0] x 30 [m\u00a0<\/span>2<\/span><\/sup>\u00a0] = 323 W<\/span><\/p>\n

        Como pode ser visto, uma adi\u00e7\u00e3o de isolador t\u00e9rmico causa uma diminui\u00e7\u00e3o significativa nas perdas de calor.\u00a0Deve ser adicionado, uma adi\u00e7\u00e3o da pr\u00f3xima camada de isolador t\u00e9rmico n\u00e3o causa economias t\u00e3o altas.\u00a0Isso pode ser visto melhor no m\u00e9todo de resist\u00eancia t\u00e9rmica, que pode ser usado para calcular a transfer\u00eancia de calor atrav\u00e9s de\u00a0<\/span>paredes compostas<\/span><\/strong>\u00a0.\u00a0A taxa de transfer\u00eancia constante de calor entre duas superf\u00edcies \u00e9 igual \u00e0 diferen\u00e7a de temperatura dividida pela\u00a0<\/span>resist\u00eancia t\u00e9rmica<\/span><\/a>\u00a0total\u00a0entre essas duas superf\u00edcies.<\/span><\/p>\n

        \"resist\u00eancia<\/a><\/p>\n<\/div>\n<\/div>\n

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        \n
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        \n

         <\/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<\/div>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

        O isolamento otton consiste em 85% de algod\u00e3o reciclado e 15% de fibras pl\u00e1sticas.\u00a0Da mesma forma que na celulose, para tornar o isolamento do algod\u00e3o retardador de chamas, o algod\u00e3o deve ser impregnado.\u00a0Engenharia T\u00e9rmica Isolamento de algod\u00e3o O isolamento de algod\u00e3o \u00e9 feito de t\u00eaxteis de algod\u00e3o reciclado p\u00f3s-industrial.\u00a0O isolamento do algod\u00e3o consiste em 85% … 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 isolamento de algod\u00e3o - Defini\u00e7\u00e3o<\/title>\n<meta name=\"description\" content=\"O isolamento otton consiste em 85% de algod\u00e3o reciclado e 15% de fibras pl\u00e1sticas. 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