{"id":47176,"date":"2019-11-03T12:52:52","date_gmt":"2019-11-03T11:52:52","guid":{"rendered":"https:\/\/www.thermal-engineering.org\/o-que-e-analise-de-trocador-de-calor-calculo-de-desempenho-definicao\/"},"modified":"2020-01-22T14:51:48","modified_gmt":"2020-01-22T13:51:48","slug":"o-que-e-analise-de-trocador-de-calor-calculo-de-desempenho-definicao","status":"publish","type":"post","link":"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-analise-de-trocador-de-calor-calculo-de-desempenho-definicao\/","title":{"rendered":"O que \u00e9 an\u00e1lise de trocador de calor &#8211; C\u00e1lculo de desempenho &#8211; Defini\u00e7\u00e3o"},"content":{"rendered":"<div class=\"su-quote su-quote-style-default\">\n<div class=\"su-quote-inner su-clearfix\">Na an\u00e1lise de trocadores de calor, geralmente \u00e9 conveniente trabalhar com termos como LMTD e fator U.\u00a0Esses termos s\u00e3o definidos em An\u00e1lise do trocador de calor &#8211; C\u00e1lculo de desempenho.\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>An\u00e1lise do trocador de calor &#8211; C\u00e1lculo do trocador de calor<\/h2>\n<p><strong>Os trocadores de calor\u00a0s\u00e3o comumente usados \u200b\u200bna ind\u00fastria, e o design adequado de um trocador de calor depende de muitas vari\u00e1veis.\u00a0<\/strong>Na an\u00e1lise de permutadores de calor, muitas vezes \u00e9 conveniente trabalhar com um<strong><a title=\"Coeficiente geral de transfer\u00eancia de calor - fator U\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-o-coeficiente-geral-de-transferencia-de-calor-fator-u-definicao\/\">\u00a0\u00a0coeficiente de transfer\u00eancia total de calor<\/a>\u00a0,\u00a0<\/strong>conhecido como um\u00a0<strong>factor-L<\/strong>.\u00a0O fator U \u00e9 definido por uma express\u00e3o an\u00e1loga \u00e0\u00a0<strong><a title=\"Lei do resfriamento de Newton\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-a-lei-do-resfriamento-de-newton-definicao\/\">\u00a0lei do resfriamento de Newton<\/a>\u00a0.\u00a0<\/strong>Al\u00e9m disso, os engenheiros tamb\u00e9m usam a diferen\u00e7a de temperatura m\u00e9dia logar\u00edtmica (<strong>LMTD<\/strong>) para determinar a for\u00e7a motriz da temperatura na transfer\u00eancia de calor nos trocadores de calor.<\/p>\n<p>Refer\u00eancia especial: John R. Thome, livro de dados de engenharia III.\u00a0Wolverine Tube Inc. 2004.<\/p>\n<p><strong>Esses termos e m\u00e9todos, amplamente utilizados para\u00a0selecionar um trocador de calor apropriado, s\u00e3o descritos abaixo.<\/strong><\/p>\n<p><strong>An\u00e1lise do trocador de calor &#8211; C\u00e1lculo de desempenho<\/strong><\/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>Coeficiente geral de transfer\u00eancia de calor<\/h2>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/U-factor-Overall-Heat-Transfer-Coefficient-example.png\"><img loading=\"lazy\" class=\"alignright size-medium wp-image-20392 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/U-factor-Overall-Heat-Transfer-Coefficient-example-247x300.png\" alt=\"Fator U - Coeficiente geral de transfer\u00eancia de calor\" width=\"247\" height=\"300\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/U-factor-Overall-Heat-Transfer-Coefficient-example-247x300.png\" \/><\/a>Um\u00a0<strong>trocador de calor<\/strong>\u00a0normalmente envolve dois fluidos separados por uma parede s\u00f3lida.\u00a0Muitos dos processos de transfer\u00eancia de calor encontrados na ind\u00fastria envolvem sistemas compostos e at\u00e9 envolvem uma combina\u00e7\u00e3o de\u00a0<a href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-conducao-termica-conducao-termica-definicao\/\">condu\u00e7\u00e3o<\/a>\u00a0e\u00a0<a href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-conveccao-transferencia-de-calor-por-conveccao-definicao\/\">convec\u00e7\u00e3o<\/a>\u00a0.\u00a0O calor \u00e9 primeiro transferido do fluido quente para a parede por convec\u00e7\u00e3o, atrav\u00e9s da parede por condu\u00e7\u00e3o e da parede para o fluido frio novamente por convec\u00e7\u00e3o.<\/p>\n<p>Com estes sistemas compostos, muitas vezes \u00e9 conveniente trabalhar com um\u00a0<strong><a title=\"Coeficiente geral de transfer\u00eancia de calor - fator U\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-o-coeficiente-geral-de-transferencia-de-calor-fator-u-definicao\/\">coeficiente de transfer\u00eancia total de calor<\/a>\u00a0,<\/strong>\u00a0conhecido como um\u00a0<strong>factor-L<\/strong>\u00a0.\u00a0O fator U \u00e9 definido por uma express\u00e3o an\u00e1loga \u00e0\u00a0<strong>lei do resfriamento de Newton<\/strong>\u00a0:<\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/overall-heat-transfer-coefficient-equation.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-21046 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/overall-heat-transfer-coefficient-equation.png\" alt=\"coeficiente geral de transfer\u00eancia de calor - equa\u00e7\u00e3o\" width=\"359\" height=\"174\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/overall-heat-transfer-coefficient-equation.png\" \/><\/a><\/p>\n<p>O\u00a0<strong>coeficiente geral de transfer\u00eancia de calor, U,<\/strong>\u00a0est\u00e1 relacionado \u00e0\u00a0<a href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-resistencia-termica-resistividade-termica-definicao\/\">resist\u00eancia t\u00e9rmica total<\/a>\u00a0e depende da geometria do problema.\u00a0Por exemplo,\u00a0<a href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-transferencia-de-calor-definicao\/\">a transfer\u00eancia de calor<\/a>\u00a0em um\u00a0<a href=\"https:\/\/www.nuclear-power.com\/steam-generator\/\">gerador de vapor<\/a>\u00a0envolve a convec\u00e7\u00e3o do volume do l\u00edquido de arrefecimento do reator para a superf\u00edcie do tubo interno do gerador de vapor, condu\u00e7\u00e3o atrav\u00e9s da parede do tubo e convec\u00e7\u00e3o (ebuli\u00e7\u00e3o) da superf\u00edcie do tubo externo para o fluido lateral secund\u00e1rio.<\/p>\n<p>Nos casos de transfer\u00eancia combinada de calor para um trocador de calor, existem dois valores para h.\u00a0Existe o coeficiente de transfer\u00eancia de calor por convec\u00e7\u00e3o (h) para o filme fluido dentro dos tubos e um coeficiente de transfer\u00eancia de calor por convec\u00e7\u00e3o para o filme fluido fora dos tubos.\u00a0A\u00a0<a href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-condutividade-termica-definicao\/\">condutividade t\u00e9rmica<\/a> (k) e a espessura (\u0394x) da parede do tubo tamb\u00e9m devem ser levadas em considera\u00e7\u00e3o.<\/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\">O monitoramento on-line dos\u00a0<strong>trocadores\u00a0de\u00a0calor<\/strong>\u00a0comerciais\u00a0\u00e9 feito rastreando o\u00a0<strong>coeficiente geral de transfer\u00eancia de calor<\/strong>\u00a0, porque o coeficiente geral de transfer\u00eancia de calor tende a diminuir ao longo do tempo devido \u00e0\u00a0<strong>incrusta\u00e7\u00e3o<\/strong>\u00a0.\u00a0Ao calcular periodicamente o coeficiente geral de transfer\u00eancia de calor a partir das taxas de fluxo e temperaturas do trocador, o operador do trocador de calor pode estimar a vida \u00fatil dos trocadores de calor.<\/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-accordion\">\n<div class=\"su-spoiler su-spoiler-style-default su-spoiler-icon-plus su-spoiler-closed\">\n<div class=\"su-spoiler-content su-clearfix\"><\/div>\n<\/div>\n<\/div>\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<h2><span>Diferen\u00e7a logar\u00edtmica de temperatura m\u00e9dia &#8211; LMTD<\/span><\/h2>\n<p><span>Para resolver certos problemas do trocador de calor, os\u00a0<\/span><strong><span>engenheiros<\/span><\/strong><span>\u00a0costumam usar uma\u00a0<\/span><strong><span>diferen\u00e7a de temperatura m\u00e9dia logar\u00edtmica (LMTD)<\/span><\/strong><span>\u00a0, que \u00e9 usada para determinar a for\u00e7a motriz da temperatura na transfer\u00eancia de calor nos trocadores de calor.\u00a0<\/span><strong><span>O LMTD<\/span><\/strong><span>\u00a0\u00e9 introduzido devido ao fato de que a mudan\u00e7a de temperatura que ocorre no trocador de calor da entrada at\u00e9 a sa\u00edda\u00a0<\/span><strong><span>n\u00e3o<\/span><\/strong><span>\u00a0\u00e9\u00a0<strong>linear<\/strong>\u00a0.<\/span><\/p>\n<p><span>A transfer\u00eancia de calor atrav\u00e9s da parede do trocador de calor em um determinado local \u00e9 dada pela seguinte equa\u00e7\u00e3o:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/overall-heat-transfer-coefficient-equation.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-21046 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/overall-heat-transfer-coefficient-equation.png\" alt=\"coeficiente geral de transfer\u00eancia de calor - equa\u00e7\u00e3o\" width=\"359\" height=\"174\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/overall-heat-transfer-coefficient-equation.png\" \/><\/a><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/logarithmic-mean-temperature-difference-example.png\"><img loading=\"lazy\" class=\"alignright size-medium wp-image-21044 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/logarithmic-mean-temperature-difference-example-287x300.png\" alt=\"diferen\u00e7a logar\u00edtmica de temperatura m\u00e9dia - exemplo\" width=\"287\" height=\"300\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/logarithmic-mean-temperature-difference-example-287x300.png\" \/><\/a><span>Aqui, o valor do\u00a0<\/span><strong><span>coeficiente geral de transfer\u00eancia de calor<\/span><\/strong><span>\u00a0pode ser assumido como uma constante.\u00a0Por outro lado, a diferen\u00e7a de temperatura varia continuamente com a localiza\u00e7\u00e3o (especialmente no arranjo de contra-fluxo).\u00a0Para determinar o fluxo total de calor, o fluxo de calor deve ser resumido usando \u00e1reas elementares e a diferen\u00e7a de temperatura no local ou, mais convenientemente, os engenheiros podem calcular a m\u00e9dia do valor da diferen\u00e7a de temperatura.\u00a0A equa\u00e7\u00e3o do trocador de calor pode ser resolvida com muito mais facilidade se pudermos definir uma\u00a0<\/span><strong><span>&#8220;diferen\u00e7a de temperatura m\u00e9dia&#8221; (MTD)<\/span><\/strong><span>\u00a0.\u00a0Pode ser visto pela figura que a diferen\u00e7a de temperatura varia ao longo do fluxo e a m\u00e9dia aritm\u00e9tica pode n\u00e3o ser a m\u00e9dia real, portanto, os engenheiros usam a diferen\u00e7a de temperatura m\u00e9dia logar\u00edtmica.\u00a0O &#8220;<\/span><strong><span>Diferen\u00e7a logar\u00edtmica de temperatura m\u00e9dia<\/span><\/strong><span>\u00a0\u201c\u00a0<\/span><strong><span>(LMTD)<\/span><\/strong><span>\u00a0\u00e9 uma m\u00e9dia logar\u00edtmica da diferen\u00e7a de temperatura entre as alimenta\u00e7\u00f5es quente e fria em cada extremidade do trocador de calor.\u00a0Quanto maior o LMTD, mais calor \u00e9 transferido.\u00a0Pode ser visto pela figura que a diferen\u00e7a de temperatura varia ao longo do fluxo e a m\u00e9dia aritm\u00e9tica pode n\u00e3o ser a m\u00e9dia real.<\/span><\/p>\n<p><span>Para trocadores de calor com duas extremidades (que chamamos de &#8220;A&#8221; e &#8220;B&#8221;) nas quais as correntes de calor e frio entram ou saem de ambos os lados, o LMTD \u00e9 definido como:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/logarithmic-mean-temperature-difference-definition.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-21043 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/logarithmic-mean-temperature-difference-definition.png\" alt=\"diferen\u00e7a logar\u00edtmica de temperatura m\u00e9dia - defini\u00e7\u00e3o\" width=\"304\" height=\"88\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/logarithmic-mean-temperature-difference-definition.png\" \/><\/a><\/p>\n<p><span>A transfer\u00eancia de calor \u00e9 dada por:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/LMTD-heat-transfer-equation.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-21045 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/LMTD-heat-transfer-equation.png\" alt=\"LMTD - equa\u00e7\u00e3o de transfer\u00eancia de calor\" width=\"331\" height=\"169\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/LMTD-heat-transfer-equation.png\" \/><\/a><\/p>\n<p><span>Isso vale tanto para o arranjo de fluxo paralelo, onde os fluxos entram pela mesma extremidade, quanto para o arranjo de contra-fluxo, onde entram de diferentes extremos.<\/span><\/p>\n<p><span>Em um fluxo cruzado, no qual um sistema, geralmente o dissipador de calor, tem a mesma temperatura nominal em todos os pontos da superf\u00edcie de transfer\u00eancia de calor, existe uma rela\u00e7\u00e3o semelhante entre o calor trocado e o LMTD, mas com um fator de corre\u00e7\u00e3o.\u00a0Tamb\u00e9m \u00e9 necess\u00e1rio um fator de corre\u00e7\u00e3o para outras geometrias mais complexas, como um trocador de cascas e tubos com defletores.<\/span><\/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><span>LMTD &#8211; Condensadores e Caldeiras<\/span><\/h2>\n<figure id=\"attachment_17812\" class=\"wp-caption alignright\" aria-describedby=\"caption-attachment-17812\"><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Temperature-gradients-typical-PWR-steam-generator.png\"><img loading=\"lazy\" class=\"size-medium wp-image-17812 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Temperature-gradients-typical-PWR-steam-generator-300x212.png\" alt=\"Gerador de vapor - trocador de calor de contrafluxo\" width=\"300\" height=\"212\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Temperature-gradients-typical-PWR-steam-generator-300x212.png\" \/><\/a><figcaption id=\"caption-attachment-17812\" class=\"wp-caption-text\"><span>Gradientes de temperatura no gerador de vapor PWR t\u00edpico.<\/span><\/figcaption><\/figure>\n<p><a title=\"Gerador de vapor\" href=\"https:\/\/www.nuclear-power.com\/steam-generator\/\"><span>Geradores de vapor<\/span><\/a><span>\u00a0e\u00a0<\/span><a title=\"Condensador Principal - Condensador a Vapor\" href=\"https:\/\/www.nuclear-power.com\/nuclear-power-plant\/turbine-generator-power-conversion-system\/main-condenser-steam-condenser\/\"><span>condensadores<\/span><\/a><span>\u00a0tamb\u00e9m s\u00e3o exemplos de componentes encontrados em instala\u00e7\u00f5es nucleares, onde o conceito de\u00a0<\/span><strong><span>LMTD<\/span><\/strong><span>\u00a0\u00e9 necess\u00e1rio para resolver certos problemas.\u00a0Quando a \u00e1gua sub-resfriada entra no gerador de vapor, ela deve ser aquecida at\u00e9 o ponto de ebuli\u00e7\u00e3o e depois deve ser evaporada.\u00a0Como a evapora\u00e7\u00e3o est\u00e1 ocorrendo a temperatura constante, n\u00e3o pode ser usado um \u00fanico LMTD.\u00a0Nesse caso, o trocador de calor deve ser tratado como uma combina\u00e7\u00e3o de dois ou tr\u00eas (quando ocorre superaquecimento) trocadores de calor.<\/span><\/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><span>Pinch Point &#8211; Trocador de Calor<\/span><\/h2>\n<p><span>H\u00e1 outro aspecto interessante no projeto, pois a diferen\u00e7a de temperatura conhecida como\u00a0<\/span><strong><span>&#8216;pitada&#8217;<\/span><\/strong><span>\u00a0pode limitar o desempenho dos trocadores de calor se as \u00e1reas e taxas de fluxo n\u00e3o forem projetadas adequadamente.\u00a0<\/span><strong><span>O ponto de aperto<\/span><\/strong><span>\u00a0\u00e9 o local no trocador de calor em que a diferen\u00e7a de temperatura entre o fluido quente e o frio \u00e9\u00a0<\/span><strong><span>m\u00ednima<\/span><\/strong><span>\u00a0nesse local.<\/span><\/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><span>M\u00e9todo de efic\u00e1cia NTU<\/span><\/h2>\n<p><span>O\u00a0m\u00e9todo da\u00a0<\/span><strong><span>diferen\u00e7a de temperatura m\u00e9dia logar\u00edtmica<\/span><\/strong><span>\u00a0(LMTD) discutido na se\u00e7\u00e3o anterior \u00e9 f\u00e1cil de usar na an\u00e1lise do trocador de calor quando as temperaturas de entrada e sa\u00edda dos fluidos quente e frio s\u00e3o conhecidas ou podem ser determinadas a partir de um balan\u00e7o energ\u00e9tico.\u00a0Portanto, o m\u00e9todo LMTD \u00e9 muito adequado para determinar o tamanho e o desempenho de um trocador de calor.<\/span><\/p>\n<p><span>Quando o conhecimento direto do LMTD n\u00e3o est\u00e1 dispon\u00edvel e o m\u00e9todo NTU (m\u00e9todo\u00a0<\/span><strong><span>N\u00famero de unidades de transfer\u00eancia<\/span><\/strong><span>\u00a0) pode ser usado.\u00a0Este m\u00e9todo \u00e9 baseado em um par\u00e2metro sem dimens\u00e3o chamado efetividade da transfer\u00eancia de calor, definido como:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/NTU-Effectiveness-Method-equation.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-21051 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/NTU-Effectiveness-Method-equation.png\" alt=\"M\u00e9todo de Efetividade NTU - equa\u00e7\u00e3o\" width=\"368\" height=\"53\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/NTU-Effectiveness-Method-equation.png\" \/><\/a><\/p>\n<p><span>Como pode ser visto, a\u00a0<\/span><em><span>efic\u00e1cia<\/span><\/em><span>\u00a0\u00e9 a raz\u00e3o entre a taxa real de transfer\u00eancia de calor e a taxa m\u00e1xima poss\u00edvel de transfer\u00eancia de calor.\u00a0Para definir a efic\u00e1cia de um trocador de calor, devemos primeiro determinar a taxa de transfer\u00eancia de calor m\u00e1xima poss\u00edvel, q\u00a0<\/span><sub><span>max<\/span><\/sub><span>\u00a0, para o trocador de calor.<\/span><\/p>\n<p><span>Leitura adicional:<\/span><\/p>\n<ol>\n<li><span>Fundamentos de transfer\u00eancia de calor e massa, 7\u00aa edi\u00e7\u00e3o.\u00a0Theodore L. Bergman, Adrienne S. Lavine, Frank P. Incropera.\u00a0John Wiley &amp; Sons, Incorporated, 2011. ISBN: 9781118137253.<\/span><\/li>\n<li><span>Transfer\u00eancia de Calor e Massa.\u00a0Yunus A. Cengel.\u00a0McGraw-Hill Education, 2011. ISBN: 9780071077866.<\/span><\/li>\n<\/ol>\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><span>Exemplo: C\u00e1lculo do Trocador de Calor<\/span><\/h2>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/example-heat-exchanger-calculation-LMTD.png\"><img loading=\"lazy\" class=\"alignright size-medium wp-image-21042 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/example-heat-exchanger-calculation-LMTD-300x266.png\" alt=\"exemplo - c\u00e1lculo de trocador de calor - LMTD\" width=\"300\" height=\"266\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/example-heat-exchanger-calculation-LMTD-300x266.png\" \/><\/a><span>Considere um\u00a0<\/span><strong><span>trocador de calor de fluxo paralelo<\/span><\/strong><span>\u00a0, usado para resfriar o \u00f3leo de 70 \u00b0 C a 40 \u00b0 C usando \u00e1gua dispon\u00edvel a 30 \u00b0 C.\u00a0A temperatura de sa\u00edda da \u00e1gua \u00e9 de 36 \u00b0 C.\u00a0A taxa de fluxo de \u00f3leo \u00e9 de 1 kg \/ s.\u00a0O calor espec\u00edfico do \u00f3leo \u00e9 de 2,2 kJ \/ kg K. O coeficiente de transfer\u00eancia total de calor\u00a0<\/span><strong><span>U = 200 W \/ m\u00a0<\/span><sup><span>2<\/span><\/sup><span>\u00a0K<\/span><\/strong><span>\u00a0.<\/span><\/p>\n<p><span>Calcule a\u00a0<\/span><strong><span>diferen\u00e7a de temperatura m\u00e9dia logar\u00edtmica<\/span><\/strong><span>\u00a0.\u00a0Determine a\u00a0<\/span><strong><span>\u00e1rea<\/span><\/strong><span>\u00a0desse trocador de calor necess\u00e1ria para esse desempenho.<\/span><\/p>\n<ol>\n<li><strong><span>LMTD<\/span><\/strong><\/li>\n<\/ol>\n<p><span>A diferen\u00e7a logar\u00edtmica de temperatura m\u00e9dia pode ser calculada simplesmente usando sua defini\u00e7\u00e3o:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/LMTD-example.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-21050 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/LMTD-example.png\" alt=\"LMTD - exemplo\" width=\"371\" height=\"76\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/LMTD-example.png\" \/><\/a><\/p>\n<ol start=\"2\">\n<li><span>\u00c1rea do trocador de calor<\/span><\/li>\n<\/ol>\n<p><span>Para calcular a \u00e1rea desse trocador de calor, precisamos calcular a taxa de fluxo de calor usando a taxa de fluxo de massa de \u00f3leo e LMTD.<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Energy-Balance-Example.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-21049 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Energy-Balance-Example.png\" alt=\"Balan\u00e7o Energ\u00e9tico - Exemplo\" width=\"412\" height=\"265\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Energy-Balance-Example.png\" \/><\/a><\/p>\n<p><span>A \u00e1rea necess\u00e1ria desse trocador de calor pode ser calculada diretamente usando a equa\u00e7\u00e3o geral de transfer\u00eancia de calor:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/heat-exchanger-calculation.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-21048 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/heat-exchanger-calculation.png\" alt=\"trocador de calor - c\u00e1lculo\" width=\"512\" height=\"306\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/heat-exchanger-calculation.png\" \/><\/a><\/p>\n<\/div>\n<\/div>\n<div class=\"inside-grid-column\"><\/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>Na an\u00e1lise de trocadores de calor, geralmente \u00e9 conveniente trabalhar com termos como LMTD e fator U.\u00a0Esses termos s\u00e3o definidos em An\u00e1lise do trocador de calor &#8211; C\u00e1lculo de desempenho.\u00a0Engenharia T\u00e9rmica An\u00e1lise do trocador de calor &#8211; C\u00e1lculo do trocador de calor Os trocadores de calor\u00a0s\u00e3o comumente usados \u200b\u200bna ind\u00fastria, e o design adequado de &#8230; <a title=\"O que \u00e9 an\u00e1lise de trocador de calor &#8211; C\u00e1lculo de desempenho &#8211; Defini\u00e7\u00e3o\" class=\"read-more\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-analise-de-trocador-de-calor-calculo-de-desempenho-definicao\/\" aria-label=\"More on O que \u00e9 an\u00e1lise de trocador de calor &#8211; C\u00e1lculo de desempenho &#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 an\u00e1lise de trocador de calor - C\u00e1lculo de desempenho - Defini\u00e7\u00e3o<\/title>\n<meta name=\"description\" content=\"Na an\u00e1lise de trocadores de calor, geralmente \u00e9 conveniente trabalhar com termos como LMTD e fator U. 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