{"id":48869,"date":"2019-11-12T13:29:42","date_gmt":"2019-11-12T12:29:42","guid":{"rendered":"https:\/\/www.thermal-engineering.org\/o-que-e-a-lei-da-termodinamica-definicao\/"},"modified":"2020-01-30T14:20:05","modified_gmt":"2020-01-30T13:20:05","slug":"o-que-e-a-lei-da-termodinamica-definicao","status":"publish","type":"post","link":"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-a-lei-da-termodinamica-definicao\/","title":{"rendered":"O que \u00e9 a Lei da Termodin\u00e2mica &#8211; Defini\u00e7\u00e3o"},"content":{"rendered":"<div class=\"su-quote su-quote-style-default\">\n<div class=\"su-quote-inner su-clearfix\">Existem quatro leis da termodin\u00e2mica que definem quantidades f\u00edsicas fundamentais (temperatura, energia e entropia) e que caracterizam os sistemas termodin\u00e2micos.\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>Leis da Termodin\u00e2mica<\/h2>\n<p>Existem\u00a0<strong>quatro leis da termodin\u00e2mica<\/strong>\u00a0que definem quantidades f\u00edsicas fundamentais (temperatura, energia e entropia) e que caracterizam os sistemas termodin\u00e2micos em\u00a0<a title=\"Equil\u00edbrio t\u00e9rmico\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/thermodynamic-properties\/what-is-temperature-physics\/thermal-equilibrium\/\"><strong>equil\u00edbrio t\u00e9rmico<\/strong><\/a>\u00a0.\u00a0Essas s\u00e3o consideradas uma das leis mais importantes de toda a f\u00edsica.\u00a0As leis s\u00e3o as seguintes:<\/p>\n<p><a title=\"Lei Zeroth da Termodin\u00e2mica\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-a-lei-zeroth-da-termodinamica-definicao\/\"><strong>Lei zero da termodin\u00e2mica:<\/strong><\/a><\/p>\n<p><em>Se dois sistemas est\u00e3o em equil\u00edbrio t\u00e9rmico com um ter\u00e7o, eles est\u00e3o em equil\u00edbrio t\u00e9rmico entre si. \u00a0<\/em><\/p>\n<p>Esta lei fornece uma defini\u00e7\u00e3o e m\u00e9todo para definir temperaturas, talvez a propriedade intensiva mais importante de um sistema ao lidar com problemas de convers\u00e3o de energia t\u00e9rmica.<\/p>\n<p><a title=\"Primeira Lei da Termodin\u00e2mica\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-a-primeira-lei-da-termodinamica-definicao\/\"><strong>Primeira lei da termodin\u00e2mica:<\/strong><\/a><\/p>\n<p><em>O aumento da energia interna de um sistema fechado \u00e9 igual ao calor fornecido ao sistema menos o trabalho realizado por ele. \u00a0<\/em><\/p>\n<p>Esta lei \u00e9 o\u00a0<a title=\"Lei de Conserva\u00e7\u00e3o de Energia\" href=\"https:\/\/www.nuclear-power.com\/laws-of-conservation\/law-of-conservation-of-energy\/\"><strong>princ\u00edpio da conserva\u00e7\u00e3o de energia<\/strong><\/a>\u00a0.\u00a0\u00c9 a lei mais importante para an\u00e1lise da maioria dos sistemas e a que quantifica como a energia t\u00e9rmica \u00e9\u00a0<strong>transformada<\/strong>\u00a0em outras\u00a0<a title=\"Formas de energia\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/what-is-energy-physics\/forms-of-energy\/\">formas de energia<\/a>\u00a0.\u00a0Segue-se que m\u00e1quinas perp\u00e9tuas de movimento do primeiro tipo s\u00e3o imposs\u00edveis.<\/p>\n<p><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><\/p>\n<p><em>A entropia de qualquer sistema isolado nunca diminui.\u00a0Em um processo termodin\u00e2mico natural, a soma das entropias dos sistemas termodin\u00e2micos em intera\u00e7\u00e3o aumenta. \u00a0<\/em><\/p>\n<p>Esta lei indica a\u00a0<strong>irreversibilidade<\/strong>\u00a0dos\u00a0<strong>processos naturais<\/strong>\u00a0.\u00a0<a title=\"Processo revers\u00edvel\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-processo-reversivel-definicao\/\">Processos revers\u00edveis<\/a>\u00a0s\u00e3o uma fic\u00e7\u00e3o te\u00f3rica \u00fatil e conveniente, mas n\u00e3o ocorrem na natureza.\u00a0A partir desta lei, \u00e9 imposs\u00edvel construir um dispositivo que opere em um ciclo e cujo \u00fanico efeito seja a transfer\u00eancia de calor de um corpo mais frio para um corpo mais quente.\u00a0Segue-se que m\u00e1quinas perp\u00e9tuas de movimento do segundo tipo s\u00e3o imposs\u00edveis.<\/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><a title=\"Terceira Lei da Termodin\u00e2mica - Terceira Lei\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-a-terceira-lei-da-termodinamica-terceira-lei-definicao\/\"><strong><span>Terceira lei da termodin\u00e2mica:<\/span><\/strong><\/a><\/p>\n<p><em><span>A entropia de um sistema se aproxima de um valor constante, \u00e0 medida que a temperatura se aproxima do zero absoluto.<\/span><\/em><\/p>\n<p><span>Com base em evid\u00eancias emp\u00edricas, essa lei afirma que a\u00a0<\/span><strong><a title=\"O que \u00e9 entropia\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/what-is-energy-physics\/what-is-entropy\/\"><span>entropia<\/span><\/a><span>\u00a0de uma subst\u00e2ncia cristalina pura \u00e9 zero<\/span><\/strong><span>\u00a0no\u00a0<strong>zero\u00a0<\/strong><\/span><strong><span>absoluto da temperatura<\/span><\/strong><span>\u00a0, 0 K e que \u00e9 imposs\u00edvel por meio de qualquer processo, n\u00e3o importa o ideal, reduzir a temperatura de um sistema para zero absoluto em um n\u00famero finito de etapas.\u00a0Isso nos permite definir um ponto zero para a energia t\u00e9rmica de um corpo.<\/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>Vers\u00e3o popular das leis da termodin\u00e2mica<\/span><\/h2>\n<p><strong><span>0. Voc\u00ea deve jogar o jogo.<\/span><\/strong><\/p>\n<p><strong><span>1. Voc\u00ea n\u00e3o pode vencer;\u00a0voc\u00ea s\u00f3 pode empatar.<\/span><\/strong><\/p>\n<p><strong><span>2. Voc\u00ea s\u00f3 pode empatar no zero absoluto.<\/span><\/strong><\/p>\n<p><strong><span>3. Voc\u00ea n\u00e3o pode alcan\u00e7ar o zero absoluto.<\/span><\/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\"><\/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>Trabalho e Calor em Termodin\u00e2mica<\/span><\/h2>\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>Calor na Termodin\u00e2mica<\/span><\/h2>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Zeroth-Law-of-Thermodynamics-heat.png\"><img loading=\"lazy\" class=\"alignright size-medium wp-image-16452 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Zeroth-Law-of-Thermodynamics-heat-300x158.png\" alt=\"zeroth-lei-da-termodin\u00e2mica-calor\" width=\"300\" height=\"158\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Zeroth-Law-of-Thermodynamics-heat-300x158.png\" \/><\/a><\/p>\n<p><span>Veja tamb\u00e9m:\u00a0<\/span><a title=\"Calor na Termodin\u00e2mica\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-calor-na-fisica-calor-definicao\/\"><span>Calor na termodin\u00e2mica<\/span><\/a><\/p>\n<p><span>Veja tamb\u00e9m:\u00a0<\/span><a title=\"Trabalho em Termodin\u00e2mica\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-trabalho-em-termodinamica-definicao\/\"><span>Trabalho em termodin\u00e2mica<\/span><\/a><\/p>\n<p><span>Enquanto\u00a0<\/span><strong><span>energia interna<\/span><\/strong><span>\u00a0se refere \u00e0 energia total de todas as mol\u00e9culas dentro do objeto, o\u00a0<\/span><strong><span>calor<\/span><\/strong><span>\u00a0\u00e9 a quantidade de energia que\u00a0<\/span><strong><span>flui<\/span><\/strong><span>\u00a0de um corpo para outro espontaneamente devido \u00e0 diferen\u00e7a de temperatura.\u00a0<\/span><strong><span>O calor<\/span><\/strong><span>\u00a0\u00e9 uma forma de energia, mas \u00e9\u00a0<\/span><strong><span>energia em tr\u00e2nsito<\/span><\/strong><span>\u00a0.\u00a0O calor n\u00e3o \u00e9 propriedade de um sistema.\u00a0No entanto, a transfer\u00eancia de energia como calor ocorre no n\u00edvel molecular como resultado de uma\u00a0<\/span><strong><span>diferen\u00e7a de temperatura<\/span><\/strong><span>\u00a0.<\/span><\/p>\n<p><span>Considere um\u00a0<\/span><strong><span>bloco de metal<\/span><\/strong><span>\u00a0em alta temperatura, que consiste em \u00e1tomos que oscilam intensamente em torno de suas posi\u00e7\u00f5es m\u00e9dias.\u00a0<\/span><strong><span>A baixas temperaturas<\/span><\/strong><span>\u00a0, os \u00e1tomos continuam a oscilar, mas com\u00a0<\/span><strong><span>menos intensidade<\/span><\/strong><span>\u00a0.\u00a0Se um bloco mais quente de metal \u00e9 colocado em contato com um bloco mais frio, os \u00e1tomos intensamente oscilantes na borda do bloco mais quente emitem sua energia cin\u00e9tica para os \u00e1tomos menos oscilantes na borda do bloco frio.\u00a0Nesse caso, h\u00e1\u00a0<\/span><strong><span>transfer\u00eancia de energia<\/span><\/strong><span>\u00a0entre esses dois blocos e o\u00a0<\/span><strong><span>calor flui<\/span><\/strong><span>\u00a0do bloco mais quente para o mais frio por essas vibra\u00e7\u00f5es aleat\u00f3rias.<\/span><\/p>\n<p><span>Em geral, quando dois objetos s\u00e3o colocados em\u00a0<\/span><strong><span>contato t\u00e9rmico<\/span><\/strong><span>\u00a0, o\u00a0<\/span><strong><span>calor flui<\/span><\/strong><span>\u00a0entre eles\u00a0<\/span><strong><span>at\u00e9<\/span><\/strong><span>\u00a0que entrem em\u00a0<\/span><strong><span>equil\u00edbrio<\/span><\/strong><span>\u00a0um com o outro.\u00a0Quando\u00a0existe\u00a0uma\u00a0<\/span><strong><span>diferen\u00e7a de temperatura<\/span><\/strong><span>\u00a0, o calor flui espontaneamente\u00a0<\/span><strong><span>do sistema mais quente para o sistema mais frio<\/span><\/strong><span>\u00a0.\u00a0A transfer\u00eancia de calor ocorre por\u00a0<\/span><strong><span>condu\u00e7\u00e3o<\/span><\/strong><span>\u00a0ou por\u00a0<\/span><strong><span>radia\u00e7\u00e3o t\u00e9rmica<\/span><\/strong><span>\u00a0.\u00a0Quando o\u00a0<\/span><strong><span>fluxo de calor para<\/span><\/strong><span>\u00a0, diz-se que est\u00e1 na\u00a0<\/span><strong><span>mesma temperatura<\/span><\/strong><span>\u00a0.\u00a0Dizem que eles est\u00e3o em\u00a0<\/span><a title=\"Equil\u00edbrio t\u00e9rmico\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/thermodynamic-properties\/what-is-temperature-physics\/thermal-equilibrium\/\"><strong><span>equil\u00edbrio t\u00e9rmico<\/span><\/strong><\/a><span>\u00a0.<\/span><\/p>\n<p><span>Como no trabalho, a quantidade de calor transferida\u00a0<\/span><strong><span>depende do caminho<\/span><\/strong><span>\u00a0e n\u00e3o simplesmente das condi\u00e7\u00f5es iniciais e finais do sistema.\u00a0Na verdade, existem muitas maneiras de levar o g\u00e1s do estado i para o estado f.<\/span><\/p>\n<p><span>Al\u00e9m disso, como no trabalho, \u00e9 importante distinguir entre o\u00a0<\/span><strong><span>calor adicionado<\/span><\/strong><span>\u00a0a um sistema do ambiente e o\u00a0<\/span><strong><span>calor removido<\/span><\/strong><span>\u00a0do sistema para o ambiente.\u00a0Q \u00e9 positivo para o calor adicionado ao sistema, portanto, se o calor sai do sistema, Q \u00e9 negativo.\u00a0Como W na equa\u00e7\u00e3o \u00e9 o trabalho realizado pelo sistema, se o trabalho for realizado no sistema, W ser\u00e1 negativo e E\u00a0<\/span><sub><span>int<\/span><\/sub><span>\u00a0aumentar\u00e1.<\/span><\/p>\n<p><span>O s\u00edmbolo\u00a0<\/span><strong><span>q<\/span><\/strong><span>\u00a0\u00e9 usado algumas vezes para indicar o calor adicionado ou removido de um sistema\u00a0<\/span><strong><span>por unidade de massa<\/span><\/strong><span>\u00a0.\u00a0\u00c9 igual ao calor total (Q) adicionado ou removido dividido pela massa (m).<\/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>Trabalho em Termodin\u00e2mica<\/span><\/h2>\n<figure id=\"attachment_16883\" class=\"wp-caption alignright\" aria-describedby=\"caption-attachment-16883\"><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/pdV-Work-Thermodynamics.png\"><img loading=\"lazy\" class=\"size-medium wp-image-16883 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/pdV-Work-Thermodynamics-300x242.png\" alt=\"Trabalho pdV - Termodin\u00e2mica\" width=\"300\" height=\"242\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/pdV-Work-Thermodynamics-300x242.png\" \/><\/a><figcaption id=\"caption-attachment-16883\" class=\"wp-caption-text\"><span>p\u0394V O trabalho \u00e9 igual \u00e0 \u00e1rea sob a curva do processo plotada no diagrama press\u00e3o-volume.<\/span><\/figcaption><\/figure>\n<p><span>Na termodin\u00e2mica, o\u00a0<\/span><strong><span>trabalho<\/span><\/strong><span>\u00a0realizado por um sistema \u00e9 a energia transferida pelo sistema para os arredores.\u00a0Energia cin\u00e9tica, energia potencial e energia interna s\u00e3o formas de energia que s\u00e3o propriedades de um sistema.\u00a0<\/span><strong><span>O trabalho \u00e9 uma forma de energia<\/span><\/strong><span>\u00a0, mas \u00e9\u00a0<\/span><strong><span>energia em tr\u00e2nsito<\/span><\/strong><span>\u00a0.\u00a0Um sistema n\u00e3o cont\u00e9m trabalho, trabalho \u00e9 um processo realizado por ou em um sistema.\u00a0Em geral, o trabalho \u00e9 definido para sistemas mec\u00e2nicos como a a\u00e7\u00e3o de uma for\u00e7a sobre um objeto a dist\u00e2ncia.<\/span><\/p>\n<p><strong><em><span>W = F.\u00a0d<\/span><\/em><\/strong><\/p>\n<p><span>Onde:<\/span><\/p>\n<p><span>W = trabalho (J)<\/span><\/p>\n<p><span>F = for\u00e7a (N)<\/span><\/p>\n<p><span>d = deslocamento (m)<\/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>Motores de calor e efici\u00eancia t\u00e9rmica<\/span><\/h2>\n<figure id=\"attachment_16900\" class=\"wp-caption alignright\" aria-describedby=\"caption-attachment-16900\"><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/heat-engine-example.png\"><img loading=\"lazy\" class=\"size-medium wp-image-16900 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/heat-engine-example-300x224.png\" alt=\"Exemplo de motor t\u00e9rmico\" width=\"300\" height=\"224\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/heat-engine-example-300x224.png\" \/><\/a><figcaption id=\"caption-attachment-16900\" class=\"wp-caption-text\"><span>O ciclo Rankine descreve de perto os processos em motores t\u00e9rmicos a vapor comumente encontrados na maioria das usinas termel\u00e9tricas.<\/span><\/figcaption><\/figure>\n<p><a title=\"Fontes de energia\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/what-is-energy-physics\/energy-sources\/\"><strong><span>As fontes de energia<\/span><\/strong><\/a><span>\u00a0sempre desempenharam um papel muito importante no desenvolvimento da sociedade humana.\u00a0<\/span><strong><a title=\"O que \u00e9 energia - F\u00edsica\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/what-is-energy-physics\/\"><span>A energia<\/span><\/a><\/strong><span>\u00a0\u00e9 geralmente definida como o<\/span><strong><span>\u00a0potencial de\u00a0<\/span><a title=\"Trabalho em Termodin\u00e2mica\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-trabalho-em-termodinamica-definicao\/\"><span>trabalhar<\/span><\/a><\/strong>\u00a0<strong><span>ou produzir\u00a0<\/span><a title=\"Calor na Termodin\u00e2mica\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-calor-na-fisica-calor-definicao\/\"><span>calor<\/span><\/a><\/strong><span>\u00a0.\u00a0\u00c0s vezes, \u00e9 como a &#8220;moeda&#8221; para executar o trabalho.\u00a0Uma das propriedades mais maravilhosas do universo \u00e9 que a<\/span><strong><span>\u00a0energia pode ser transformada de um tipo para outro<\/span><\/strong><span>\u00a0e<\/span><strong><span>\u00a0transferida de um objeto para outro<\/span><\/strong><span>\u00a0.<\/span><\/p>\n<p><span>Em geral, \u00e9 f\u00e1cil produzir\u00a0<\/span><a href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-energia-interna-energia-termica-definicao\/\"><strong><span>energia t\u00e9rmica<\/span><\/strong><\/a>\u00a0<strong><span>realizando trabalhos<\/span><\/strong><span>\u00a0, por exemplo, por qualquer processo de atrito.\u00a0Mas\u00a0<\/span><strong><span>conseguir trabalho com energia t\u00e9rmica<\/span><\/strong><span>\u00a0\u00e9 mais\u00a0<\/span><strong><span>dif\u00edcil<\/span><\/strong><span>\u00a0.\u00a0Est\u00e1 intimamente associado ao\u00a0<\/span><a title=\"O que \u00e9 entropia\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/what-is-energy-physics\/what-is-entropy\/\"><span>conceito de entropia<\/span><\/a><span>\u00a0.\u00a0Por exemplo, a eletricidade \u00e9 particularmente \u00fatil, pois possui\u00a0<strong>entropia\u00a0<\/strong><\/span><strong><span>muito\u00a0<\/span><\/strong><strong><span>baixa<\/span><\/strong><span>\u00a0(\u00e9 altamente ordenada) e pode ser convertida em outras formas de energia com\u00a0<\/span><strong><span>muita efici\u00eancia<\/span><\/strong><span>\u00a0.<\/span><\/p>\n<p><span>\u00c0s vezes,\u00a0<\/span><a title=\"O que \u00e9 energia mec\u00e2nica\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/what-is-energy-physics\/what-is-mechanical-energy\/\"><span>a energia mec\u00e2nica<\/span><\/a><span>\u00a0est\u00e1 diretamente dispon\u00edvel, por exemplo, energia e\u00f3lica e hidrel\u00e9trica.\u00a0Mas a maior parte de nossa energia vem da queima de\u00a0<\/span><strong><span>combust\u00edveis f\u00f3sseis<\/span><\/strong><span>\u00a0(carv\u00e3o, petr\u00f3leo e g\u00e1s) e de\u00a0<\/span><a title=\"Rea\u00e7\u00f5es nucleares\" href=\"https:\/\/www.nuclear-power.com\/nuclear-power\/nuclear-reactions\/\"><strong><span>rea\u00e7\u00f5es nucleares<\/span><\/strong><\/a><span>\u00a0.\u00a0Atualmente, o combust\u00edvel f\u00f3ssil ainda \u00e9 a fonte de energia predominante no mundo.\u00a0Mas a queima de combust\u00edveis f\u00f3sseis gera\u00a0<\/span><strong><span>apenas energia t\u00e9rmica<\/span><\/strong><span>\u00a0, portanto, essas fontes de energia s\u00e3o chamadas de \u201c\u00a0<\/span><a title=\"Fontes de energia prim\u00e1ria\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/what-is-energy-physics\/primary-energy-sources\/\"><strong><span>fontes de energia prim\u00e1ria<\/span><\/strong><\/a><span>\u00a0\u201d, que devem\u00a0<\/span><strong><span>ser convertidas<\/span><\/strong><span>\u00a0em\u00a0<\/span><strong><a title=\"Fontes de energia secund\u00e1rias - Transportadoras de energia\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/what-is-energy-physics\/secondary-energy-sources-energy-carriers\/\"><span>fonte de energia secund\u00e1ria<\/span><\/a><\/strong><span>\u00a0, chamadas de\u00a0<\/span><strong><span>portadores de energia<\/span><\/strong><span>\u00a0(\u00a0<\/span><a title=\"Energia el\u00e9trica\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/what-is-energy-physics\/electrical-energy\/\"><span>energia el\u00e9trica<\/span><\/a><span>\u00a0etc.).\u00a0Para converter energia t\u00e9rmica em outra forma de energia, um\u00a0<\/span><strong><span>motor t\u00e9rmico<\/span><\/strong><span>\u00a0deve ser usado.<\/span><\/p>\n<p><span>Em geral, um\u00a0<\/span><strong><span>motor t\u00e9rmico<\/span><\/strong><span>\u00a0\u00e9 um dispositivo que converte energia qu\u00edmica em calor ou energia t\u00e9rmica e depois em energia mec\u00e2nica ou em energia el\u00e9trica.\u00a0Muitos\u00a0<\/span><strong><span>motores t\u00e9rmicos<\/span><\/strong><span>\u00a0\u00a0operam de maneira c\u00edclica, adicionando energia na forma de calor em uma parte do ciclo e usando essa energia para realizar trabalhos \u00fateis em outra parte do ciclo.<\/span><\/p>\n<p><span>Por exemplo, como \u00e9 t\u00edpico em todas as\u00a0<\/span><strong><span>usinas t\u00e9rmicas<\/span><\/strong><span>\u00a0convencionais\u00a0<strong>,<\/strong>\u00a0\u00a0o calor \u00e9 usado para gerar\u00a0<\/span><a title=\"Propriedades do Steam - O que \u00e9 o Steam\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-o-steam-propriedades-do-steam-definicao\/\"><span>vapor<\/span><\/a><span>\u00a0que aciona uma\u00a0<\/span><strong><span>turbina a vapor<\/span><\/strong><span>\u00a0conectada a um gerador que produz eletricidade.\u00a0<\/span><a title=\"Gerador de vapor\" href=\"https:\/\/www.nuclear-power.com\/steam-generator\/\"><span>Geradores de<\/span><\/a><span>\u00a0vapor, turbinas a vapor, condensadores e bombas de \u00e1gua de alimenta\u00e7\u00e3o constituem um\u00a0<\/span><strong><span>motor t\u00e9rmico<\/span><\/strong><span>\u00a0, sujeito \u00e0s limita\u00e7\u00f5es de efici\u00eancia impostas pela\u00a0<\/span><strong><span>segunda lei da termodin\u00e2mica<\/span><\/strong><span>\u00a0.\u00a0Nas modernas\u00a0<\/span><a title=\"Usina nuclear\" href=\"https:\/\/www.nuclear-power.com\/nuclear-power-plant\/\"><span>usinas nucleares,<\/span><\/a><span>\u00a0a efici\u00eancia termodin\u00e2mica geral \u00e9 de cerca de\u00a0<\/span><strong><span>um ter\u00e7o<\/span><\/strong><span>\u00a0(33%); portanto, s\u00e3o necess\u00e1rios\u00a0<\/span><strong><span>3000 MWth<\/span><\/strong><span>\u00a0de energia t\u00e9rmica da rea\u00e7\u00e3o de fiss\u00e3o para gerar\u00a0<\/span><strong><span>1000 MWe<\/span><\/strong><span>\u00a0de energia el\u00e9trica.<\/span><\/p>\n<p><span>Veja tamb\u00e9m:\u00a0<\/span><a title=\"Motores t\u00e9rmicos\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-o-heat-engine-definicao\/\"><span>Motores de calor<\/span><\/a><\/p>\n<p>&nbsp;<\/p>\n<h2><span>Efici\u00eancia t\u00e9rmica<\/span><\/h2>\n<p><span>Definimos a\u00a0\u00a0<\/span><a title=\"Efici\u00eancia t\u00e9rmica\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-eficiencia-termica-definicao\/\"><strong><span>efici\u00eancia t\u00e9rmica<\/span><\/strong><\/a><span>\u00a0,\u00a0\u00a0<\/span><strong><em><span>\u03b7\u00a0<\/span><sub><span>th<\/span><\/sub><\/em><\/strong><span>\u00a0, de qualquer motor de calor como a raz\u00e3o entre o\u00a0\u00a0<\/span><a href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-trabalho-em-termodinamica-definicao\/\"><span>trabalho<\/span><\/a><span>\u00a0\u00a0que faz,\u00a0\u00a0<\/span><strong><span>W<\/span><\/strong><span>\u00a0, para o\u00a0\u00a0<\/span><a href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-calor-na-fisica-calor-definicao\/\"><span>calor<\/span><\/a><span>\u00a0\u00a0de entrada a uma temperatura elevada, Q\u00a0<\/span><sub><span>H<\/span><\/sub><span>\u00a0.<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/thermal-efficiency-formula-1.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-16945 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/thermal-efficiency-formula-1.png\" alt=\"f\u00f3rmula de efici\u00eancia t\u00e9rmica - 1\" width=\"125\" height=\"82\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/thermal-efficiency-formula-1.png\" \/><\/a><\/p>\n<p><span>A\u00a0\u00a0<\/span><strong><span>efici\u00eancia t\u00e9rmica<\/span><\/strong><span>\u00a0,\u00a0\u00a0<\/span><strong><em><span>\u03b7\u00a0<\/span><sub><span>th<\/span><\/sub><\/em><\/strong><span>\u00a0, representa a fra\u00e7\u00e3o de\u00a0\u00a0<\/span><strong><span>calor<\/span><\/strong><span>\u00a0,\u00a0\u00a0<\/span><strong><span>Q\u00a0<\/span><sub><span>H<\/span><\/sub><\/strong><span>\u00a0, que \u00e9 convertida\u00a0\u00a0<\/span><strong><span>em trabalho<\/span><\/strong><span>\u00a0.\u00a0\u00c9 uma medida de desempenho adimensional de um motor t\u00e9rmico que usa energia t\u00e9rmica, como uma turbina a vapor, um motor de combust\u00e3o interna ou um refrigerador.\u00a0Para uma refrigera\u00e7\u00e3o ou bombas de calor, a efici\u00eancia t\u00e9rmica indica at\u00e9 que ponto a energia adicionada pelo trabalho \u00e9 convertida na produ\u00e7\u00e3o l\u00edquida de calor.\u00a0Como \u00e9 um n\u00famero sem dimens\u00e3o, devemos sempre expressar W, Q\u00a0<\/span><sub><span>H<\/span><\/sub><span>\u00a0e Q\u00a0<\/span><sub><span>C<\/span><\/sub><span>\u00a0\u00a0nas mesmas unidades.<\/span><\/p>\n<p><span>Como a energia \u00e9 conservada de acordo com a\u00a0\u00a0<\/span><a href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-a-primeira-lei-da-termodinamica-definicao\/\"><strong><span>primeira lei da termodin\u00e2mica<\/span><\/strong>\u00a0<\/a><span>\u00a0e a energia n\u00e3o pode ser convertida para funcionar completamente, a entrada de calor, Q\u00a0<\/span><sub><span>H<\/span><\/sub><span>\u00a0, deve ser igual ao trabalho realizado, W, mais o calor que deve ser dissipado como\u00a0\u00a0<\/span><strong><span>calor residual Q\u00a0<\/span><sub><span>C<\/span><\/sub><\/strong><span>\u00a0\u00a0no meio Ambiente.\u00a0Portanto, podemos reescrever a f\u00f3rmula da efici\u00eancia t\u00e9rmica como:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/thermal-efficiency-formula-2.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-16944 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/thermal-efficiency-formula-2.png\" alt=\"f\u00f3rmula de efici\u00eancia t\u00e9rmica - 2\" width=\"352\" height=\"83\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/thermal-efficiency-formula-2.png\" \/><\/a><\/p>\n<p><span>Para fornecer a efici\u00eancia em porcentagem, multiplicamos a f\u00f3rmula anterior por 100. Observe que\u00a0\u00a0<\/span><strong><em><span>\u03b7\u00a0<\/span><sub><span>th<\/span><\/sub><\/em><\/strong><span>\u00a0\u00a0pode ser 100% apenas se o calor residual Q\u00a0<\/span><sub><span>C<\/span><\/sub><sub>\u00a0<\/sub><span>\u00a0for zero.<\/span><\/p>\n<p><span>Em geral, a efici\u00eancia dos\u00a0\u00a0<\/span><strong><span>melhores motores t\u00e9rmicos<\/span><\/strong><span>\u00a0\u00a0\u00e9 bastante baixa.\u00a0Em suma, \u00e9\u00a0<\/span><strong><span>\u00a0muito dif\u00edcil<\/span><\/strong><span>\u00a0\u00a0para converter\u00a0<\/span><a href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/what-is-energy-physics\/internal-energy-thermal-energy\/\"><span>\u00a0energia t\u00e9rmica<\/span><\/a><span>\u00a0\u00a0a\u00a0\u00a0<\/span><a href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/what-is-energy-physics\/what-is-mechanical-energy\/\"><span>energia mec\u00e2nica<\/span><\/a><span>\u00a0.\u00a0As efici\u00eancias t\u00e9rmicas geralmente s\u00e3o\u00a0\u00a0<\/span><strong><span>inferiores a 50%<\/span><\/strong><span>\u00a0\u00a0e geralmente muito abaixo.\u00a0Tenha cuidado ao compar\u00e1-lo com a efici\u00eancia da energia e\u00f3lica ou hidrel\u00e9trica (turbinas e\u00f3licas n\u00e3o s\u00e3o motores de calor), n\u00e3o h\u00e1 convers\u00e3o de energia entre a energia t\u00e9rmica e mec\u00e2nica.<\/span><\/p>\n<p><span>Veja tamb\u00e9m:\u00a0<\/span><a title=\"Princ\u00edpio de Carnot - regra de Carnot\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/laws-of-thermodynamics\/second-law-of-thermodynamics\/carnots-principle-carnots-rule\/\"><span>Princ\u00edpio de Carnot<\/span><\/a><\/p>\n<p><span>Veja tamb\u00e9m:\u00a0<\/span><span><a title=\"Efici\u00eancia t\u00e9rmica\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-eficiencia-termica-definicao\/\">Efici\u00eancia t\u00e9rmica<\/a><\/span><\/p>\n<\/div>\n<\/div>\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>Existem quatro leis da termodin\u00e2mica que definem quantidades f\u00edsicas fundamentais (temperatura, energia e entropia) e que caracterizam os sistemas termodin\u00e2micos.\u00a0Engenharia T\u00e9rmica Leis da Termodin\u00e2mica Existem\u00a0quatro leis da termodin\u00e2mica\u00a0que definem quantidades f\u00edsicas fundamentais (temperatura, energia e entropia) e que caracterizam os sistemas termodin\u00e2micos em\u00a0equil\u00edbrio t\u00e9rmico\u00a0.\u00a0Essas s\u00e3o consideradas uma das leis mais importantes de toda a f\u00edsica.\u00a0As &#8230; <a title=\"O que \u00e9 a Lei da Termodin\u00e2mica &#8211; Defini\u00e7\u00e3o\" class=\"read-more\" href=\"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-a-lei-da-termodinamica-definicao\/\" aria-label=\"More on O que \u00e9 a Lei da Termodin\u00e2mica &#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 a Lei da Termodin\u00e2mica - Defini\u00e7\u00e3o<\/title>\n<meta name=\"description\" content=\"Existem quatro leis da termodin\u00e2mica que definem quantidades f\u00edsicas fundamentais (temperatura, energia e entropia) e que caracterizam os sistemas termodin\u00e2micos. 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