{"id":48203,"date":"2019-11-08T15:36:48","date_gmt":"2019-11-08T14:36:48","guid":{"rendered":"https:\/\/www.thermal-engineering.org\/o-que-e-causa-de-ineficiencia-eficiencia-termica-definicao\/"},"modified":"2020-01-28T08:22:29","modified_gmt":"2020-01-28T07:22:29","slug":"o-que-e-causa-de-ineficiencia-eficiencia-termica-definicao","status":"publish","type":"post","link":"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-causa-de-ineficiencia-eficiencia-termica-definicao\/","title":{"rendered":"O que \u00e9 causa de inefici\u00eancia &#8211; efici\u00eancia t\u00e9rmica &#8211; defini\u00e7\u00e3o"},"content":{"rendered":"<div class=\"su-quote su-quote-style-default\">\n<div class=\"su-quote-inner su-clearfix\">Causas de inefici\u00eancia.\u00a0Cada mecanismo t\u00e9rmico \u00e9 de alguma forma ineficiente.\u00a0Essa inefici\u00eancia pode ser atribu\u00edda a tr\u00eas causas.\u00a0Irreversibilidade de processos.\u00a0Presen\u00e7a de fric\u00e7\u00e3o.\u00a0Inefici\u00eancia do projeto.\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>Causas de inefici\u00eancia<\/h2>\n<p>Como foi discutido, uma efici\u00eancia pode variar entre 0 e 1. Cada mecanismo t\u00e9rmico \u00e9 de alguma forma ineficiente.\u00a0Essa inefici\u00eancia pode ser atribu\u00edda a tr\u00eas causas.<\/p>\n<ul>\n<li><strong>Irreversibilidade de processos<\/strong>\u00a0.\u00a0Existe um limite superior te\u00f3rico geral para a efici\u00eancia da convers\u00e3o de calor para trabalhar em qualquer motor t\u00e9rmico.\u00a0Esse limite superior \u00e9 chamado de\u00a0<strong>efici\u00eancia de Carnot<\/strong>\u00a0.\u00a0De acordo com o\u00a0<strong>princ\u00edpio Carnot<\/strong>\u00a0, nenhum motor pode ser mais eficiente que um motor revers\u00edvel (\u00a0<strong>um motor t\u00e9rmico Carnot<\/strong>\u00a0) operando entre os mesmos reservat\u00f3rios de alta temperatura e baixa temperatura.\u00a0Por exemplo, quando o reservat\u00f3rio quente tiver T\u00a0<sub>quente<\/sub>\u00a0de 400 \u00b0 C (673K) e T\u00a0<sub>frio<\/sub>\u00a0de cerca de 20 \u00b0 C (293K), a efici\u00eancia m\u00e1xima (ideal) ser\u00e1: = 1 &#8211; T\u00a0<sub>frio<\/sub>\u00a0\/ T\u00a0<sub>quente<\/sub>\u00a0= 1 &#8211; 293 \/ 673 = 56%.\u00a0Mas todos os processos termodin\u00e2micos reais s\u00e3o de alguma forma\u00a0<strong>irrevers\u00edveis<\/strong>.\u00a0Eles n\u00e3o s\u00e3o feitos infinitamente devagar.\u00a0Portanto, os motores t\u00e9rmicos devem ter efici\u00eancias mais baixas do que os limites de efici\u00eancia devido \u00e0 irreversibilidade inerente ao ciclo dos motores t\u00e9rmicos que utilizam.<\/li>\n<li><strong>Presen\u00e7a de fric\u00e7\u00e3o e perdas de calor.\u00a0<\/strong>Em sistemas termodin\u00e2micos reais ou em motores t\u00e9rmicos reais, parte da inefici\u00eancia geral do ciclo \u00e9 devida \u00e0s perdas dos componentes individuais.\u00a0Em dispositivos reais (como turbinas, bombas e compressores), um\u00a0<strong>atrito mec\u00e2nico<\/strong>\u00a0,\u00a0<strong>perdas de calor<\/strong>\u00a0e perdas no processo de combust\u00e3o causam mais perdas de efici\u00eancia.<\/li>\n<li><strong>Inefici\u00eancia do projeto<\/strong>\u00a0.\u00a0Finalmente, a \u00faltima e tamb\u00e9m importante fonte de inefici\u00eancias prov\u00e9m dos\u00a0<strong>compromissos<\/strong>\u00a0assumidos pelos\u00a0<strong>engenheiros<\/strong>\u00a0ao projetar um motor t\u00e9rmico (por exemplo, usina).\u00a0Eles devem considerar o custo e outros fatores no design e opera\u00e7\u00e3o do ciclo.\u00a0Como exemplo, considere um projeto do\u00a0<strong>condensador<\/strong>\u00a0nas usinas termel\u00e9tricas.\u00a0Idealmente, o vapor descarregado no condensador n\u00e3o teria\u00a0<strong>sub-resfriamento<\/strong>\u00a0.\u00a0Mas os condensadores reais s\u00e3o projetados para sub-resfriar o l\u00edquido em alguns graus Celsius, a fim de evitar a\u00a0<a title=\"Cavita\u00e7\u00e3o por suc\u00e7\u00e3o\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/centrifugal-pumps\/cavitation\/suction-cavitation\/\"><strong>cavita\u00e7\u00e3o de suc\u00e7\u00e3o<\/strong><\/a>\u00a0nas bombas de condensado.\u00a0Por\u00e9m, esse sub-resfriamento aumenta a inefici\u00eancia do ciclo, porque \u00e9 necess\u00e1ria mais energia para reaquecer a \u00e1gua.<\/li>\n<\/ul>\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>Efici\u00eancia t\u00e9rmica e a segunda lei<\/h2>\n<p>A\u00a0<a title=\"Segunda Lei da Termodin\u00e2mica\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-a-segunda-lei-da-termodinamica-definicao\/\"><strong>segunda lei da termodin\u00e2mica<\/strong><\/a>\u00a0pode ser expressa de v\u00e1rias maneiras espec\u00edficas.\u00a0Cada declara\u00e7\u00e3o expressa a mesma lei.\u00a0Listados abaixo est\u00e3o tr\u00eas frequentemente encontrados.<\/p>\n<ul>\n<li><a title=\"Clausius Declara\u00e7\u00e3o da Segunda Lei\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/laws-of-thermodynamics\/second-law-of-thermodynamics\/clausius-statement-of-the-second-law\/\">Declara\u00e7\u00e3o Clausius<\/a><\/li>\n<li><a title=\"Declara\u00e7\u00e3o da Segunda Lei de Kelvin-Planck\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/laws-of-thermodynamics\/second-law-of-thermodynamics\/kelvin-planck-statement-of-the-second-law\/\">Declara\u00e7\u00e3o de Kelvin-Planck<\/a><\/li>\n<li><a title=\"Entropia e a Segunda Lei da Termodin\u00e2mica\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/laws-of-thermodynamics\/second-law-of-thermodynamics\/entropy-and-the-second-law-of-thermodynamics\/\">Entropia e a Segunda Lei<\/a><\/li>\n<\/ul>\n<p><span>Antes dessas declara\u00e7\u00f5es, devemos lembrar o trabalho de\u00a0\u00a0<\/span>um engenheiro e f\u00edsico franc\u00eas,\u00a0<strong><b><span>Nicolas L\u00e9onard Sadi Carnot<\/span><\/b><\/strong>, que\u00a0avan\u00e7ou o estudo da segunda lei, formando um princ\u00edpio (\u00a0tamb\u00e9m chamado\u00a0<strong><b><span>de regra de Carnot<\/span><\/b><\/strong>\u00a0) que especifica limites para a m\u00e1xima efici\u00eancia que qualquer motor t\u00e9rmico pode obter .<\/p>\n<\/div>\n<\/div>\n<div><\/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<\/div>\n","protected":false},"excerpt":{"rendered":"<p>Causas de inefici\u00eancia.\u00a0Cada mecanismo t\u00e9rmico \u00e9 de alguma forma ineficiente.\u00a0Essa inefici\u00eancia pode ser atribu\u00edda a tr\u00eas causas.\u00a0Irreversibilidade de processos.\u00a0Presen\u00e7a de fric\u00e7\u00e3o.\u00a0Inefici\u00eancia do projeto.\u00a0Engenharia T\u00e9rmica Causas de inefici\u00eancia Como foi discutido, uma efici\u00eancia pode variar entre 0 e 1. Cada mecanismo t\u00e9rmico \u00e9 de alguma forma ineficiente.\u00a0Essa inefici\u00eancia pode ser atribu\u00edda a tr\u00eas causas. Irreversibilidade de &#8230; <a title=\"O que \u00e9 causa de inefici\u00eancia &#8211; efici\u00eancia t\u00e9rmica &#8211; defini\u00e7\u00e3o\" class=\"read-more\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-causa-de-ineficiencia-eficiencia-termica-definicao\/\" aria-label=\"More on O que \u00e9 causa de inefici\u00eancia &#8211; efici\u00eancia t\u00e9rmica &#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 causa de inefici\u00eancia - efici\u00eancia t\u00e9rmica - defini\u00e7\u00e3o<\/title>\n<meta name=\"description\" content=\"Causas de inefici\u00eancia. Cada mecanismo t\u00e9rmico \u00e9 de alguma forma ineficiente. 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