{"id":48087,"date":"2019-11-08T02:37:47","date_gmt":"2019-11-08T01:37:47","guid":{"rendered":"https:\/\/www.thermal-engineering.org\/o-que-e-limitacao-do-vapor-umido-definicao\/"},"modified":"2020-01-27T13:48:50","modified_gmt":"2020-01-27T12:48:50","slug":"o-que-e-limitacao-do-vapor-umido-definicao","status":"publish","type":"post","link":"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-limitacao-do-vapor-umido-definicao\/","title":{"rendered":"O que \u00e9 limita\u00e7\u00e3o do vapor \u00famido – Defini\u00e7\u00e3o"},"content":{"rendered":"
\n
A limita\u00e7\u00e3o do vapor \u00famido tamb\u00e9m est\u00e1 associada \u00e0 conserva\u00e7\u00e3o da entalpia. Nesse caso, uma redu\u00e7\u00e3o na press\u00e3o causa um aumento na qualidade do vapor. Engenharia T\u00e9rmica<\/div>\n<\/div>\n
<\/div>\n
<\/div>\n
\n

Processo de estrangulamento – processo isent\u00e1lpico<\/span><\/h2>\n

Um\u00a0<\/span>processo de estrangulamento<\/span><\/strong>\u00a0\u00e9 um\u00a0<\/span>processo termodin\u00e2mico<\/span><\/strong><\/a>\u00a0, no qual a\u00a0<\/span>entalpia<\/span><\/strong><\/a>\u00a0do g\u00e1s ou do meio\u00a0<\/span>permanece constante (h = const)<\/span><\/strong>\u00a0.\u00a0De fato, o\u00a0<\/span>processo de estrangulamento<\/span><\/strong>\u00a0\u00e9 um dos\u00a0<\/span>processos isent\u00e1licos<\/span><\/strong>\u00a0.\u00a0Durante o processo de estrangulamento,\u00a0<\/span>nenhum trabalho<\/span><\/strong>\u00a0\u00e9 realizado pelo sistema (dW = 0) e, geralmente, n\u00e3o\u00a0<\/span>h\u00e1 transfer\u00eancia de calor<\/span><\/strong>\u00a0(\u00a0<\/span>adiab\u00e1tica<\/span><\/strong>\u00a0) do ou para o sistema (dQ = 0).\u00a0Por outro lado, o processo de estrangulamento n\u00e3o pode ser isentr\u00f3pico, \u00e9 um\u00a0<\/span>processo fundamentalmente irrevers\u00edvel<\/span><\/strong><\/a>\u00a0.\u00a0Caracter\u00edsticas do processo de estrangulamento:<\/span><\/p>\n

    \n
  1. Transfer\u00eancia sem trabalho<\/span><\/li>\n
  2. Sem transfer\u00eancia de calor<\/span><\/li>\n
  3. Processo irrevers\u00edvel<\/span><\/li>\n
  4. Processo isent\u00e1lpico<\/span><\/li>\n<\/ol>\n

    Um estrangulamento do fluxo causa uma\u00a0<\/span>redu\u00e7\u00e3o<\/span><\/strong>\u00a0significativa\u00a0da\u00a0<\/strong>press\u00e3o<\/a><\/strong>\u00a0, porque um dispositivo de estrangulamento causa uma\u00a0<\/span>perda de press\u00e3o local<\/span><\/strong><\/a>\u00a0.\u00a0Uma limita\u00e7\u00e3o pode ser alcan\u00e7ada simplesmente introduzindo uma restri\u00e7\u00e3o em uma linha atrav\u00e9s da qual um g\u00e1s ou l\u00edquido flui.\u00a0Essa restri\u00e7\u00e3o \u00e9 comumente feita por meio de uma v\u00e1lvula parcialmente aberta ou um buj\u00e3o poroso.\u00a0Tais perdas de press\u00e3o s\u00e3o geralmente denominadas\u00a0<\/span>perdas menores<\/span><\/strong><\/a>\u00a0, embora geralmente representem uma parte importante da\u00a0<\/span>perda de<\/span><\/a>\u00a0carga\u00a0.\u00a0As perdas menores s\u00e3o aproximadamente proporcional ao\u00a0<\/span>quadrado da taxa de fluxo<\/span><\/strong>\u00a0e, portanto, eles podem ser facilmente integrados na\u00a0<\/span>equa\u00e7\u00e3o de Darcy-Weisbach<\/span><\/a>\u00a0atrav\u00e9s de\u00a0<\/span>coeficiente de resist\u00eancia K<\/span><\/strong> .<\/span><\/p>\n<\/div>\n

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

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

    Uma v\u00e1lvula parcialmente aberta ou um buj\u00e3o poroso pode ser usado para reduzir a press\u00e3o em um sistema.<\/span><\/p>\n

     <\/p>\n

    Regulagem do vapor \u00famido<\/span><\/h2>\n

    O vapor \u00famido<\/span><\/strong><\/a>\u00a0\u00e9 caracterizado pela<\/span>\u00a0qualidade<\/span><\/strong><\/a>\u00a0do\u00a0vapor<\/strong><\/a>\u00a0, que varia de zero a unidade – intervalo aberto (0,1).\u00a0A limita\u00e7\u00e3o do vapor \u00famido tamb\u00e9m est\u00e1 associada \u00e0<\/span>\u00a0conserva\u00e7\u00e3o da entalpia<\/span><\/strong>\u00a0.\u00a0A entalpia \u00e9 conservada porque nenhum trabalho \u00e9 realizado pelo sistema (dW = 0) e, geralmente, n\u00e3o h\u00e1 transfer\u00eancia de calor (adiab\u00e1tica) do ou para o sistema (dQ = 0).\u00a0Mas, neste caso, uma<\/span>\u00a0redu\u00e7\u00e3o na press\u00e3o<\/span><\/strong>\u00a0causa um<\/span>\u00a0aumento na qualidade do vapor<\/span><\/strong>\u00a0.\u00a0\u00c0 medida que a press\u00e3o cai, parte do l\u00edquido no vapor \u00famido vaporiza e aumenta a qualidade do vapor (ou seja, a fra\u00e7\u00e3o de secura).\u00a0Esse processo ocorre porque a<\/span>\u00a0temperatura de satura\u00e7\u00e3o<\/span><\/strong><\/a>\u00e9 menor na press\u00e3o mais baixa.\u00a0A temperatura mais baixa, a press\u00e3o mais baixa e o vapor de maior qualidade cont\u00eam a mesma entalpia que o vapor original.<\/span><\/p>\n

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

     <\/p>\n

    \n
    \n

    Exemplo: Regulagem de vapor \u00famido<\/span><\/h2>\n

    Um est\u00e1gio de alta press\u00e3o da turbina a vapor opera em estado estacion\u00e1rio com condi\u00e7\u00f5es de entrada de 6 MPa, t = 275,6 \u00b0 C, x = 1 (ponto C).\u00a0O vapor sai deste est\u00e1gio da turbina a uma press\u00e3o de 1,15 MPa, 186 \u00b0 C ex = 0,87 (ponto D).\u00a0Determine a qualidade do vapor quando regulado entre 1,15 MPa e 1,0 MPa.\u00a0Suponha que o processo seja adiab\u00e1tico e que nenhum trabalho seja realizado pelo sistema.<\/span><\/p>\n

    Veja tamb\u00e9m:\u00a0<\/span>Tabelas Steam<\/span><\/a><\/p>\n

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

    A entalpia para o estado D deve ser calculada usando a qualidade do vapor:<\/span><\/p>\n

    h\u00a0<\/span><\/em><\/strong>D, \u00famido<\/span><\/sub><\/em><\/strong>\u00a0= h\u00a0<\/span><\/em><\/strong>D, vapor<\/span><\/sub><\/em><\/strong>\u00a0x + (1 – x) h\u00a0<\/span><\/em><\/strong>D, l\u00edquido<\/span><\/sub><\/em><\/strong>\u00a0\u00a0= 2782.\u00a00,87 + (1 – 0,87).\u00a0790 = 2420 + 103 =<\/span>\u00a02523 kJ \/ kg<\/span><\/strong><\/p>\n

    Como \u00e9 um processo isent\u00e1lico, conhecemos a entalpia do ponto T. Nas tabelas de vapor, temos que encontrar a qualidade do vapor usando a mesma equa\u00e7\u00e3o e resolvendo a equa\u00e7\u00e3o para a qualidade do vapor, x:<\/span><\/p>\n

    h\u00a0<\/span><\/em><\/strong>T, \u00famido<\/span><\/sub><\/em><\/strong>\u00a0= h\u00a0<\/span><\/em><\/strong>T, vapor<\/span><\/sub><\/em><\/strong>\u00a0x + (1 – x) h\u00a0<\/span><\/em><\/strong>T, l\u00edquido<\/span><\/sub><\/em><\/strong><\/p>\n

    x = (\u00a0<\/span>h\u00a0<\/span><\/em><\/strong>T, \u00famido<\/span><\/sub><\/em><\/strong>\u00a0– h\u00a0<\/span><\/em><\/strong>T, l\u00edquido<\/span><\/sub><\/em><\/strong>\u00a0) \/ (\u00a0<\/span>h\u00a0<\/span><\/em><\/strong>T, vapor<\/span><\/sub><\/em><\/strong>\u00a0– h\u00a0<\/span><\/em><\/strong>T, l\u00edquido<\/span><\/sub><\/em><\/strong>\u00a0) = (2523 – 762) \/ (2777 – 762) = 0,874 = 87,4%<\/span><\/p>\n

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

    Neste caso do processo de estrangulamento (1,15 MPa a 1MPa), a qualidade do vapor aumenta de 87% para 87,4% e a temperatura diminui de 186 \u00b0 C para 179,9 \u00b0 C.<\/span><\/p>\n<\/div>\n<\/div>\n

    \n
    \n
    \"Regulagem<\/a>
    A limita\u00e7\u00e3o do vapor \u00famido geralmente causa aumento na qualidade do vapor, aumento da entropia e diminui\u00e7\u00e3o da temperatura.<\/span><\/figcaption><\/figure>\n<\/div>\n<\/div>\n
    <\/div>\n
    <\/div>\n
    \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","protected":false},"excerpt":{"rendered":"

    A limita\u00e7\u00e3o do vapor \u00famido tamb\u00e9m est\u00e1 associada \u00e0 conserva\u00e7\u00e3o da entalpia. Nesse caso, uma redu\u00e7\u00e3o na press\u00e3o causa um aumento na qualidade do vapor. Engenharia T\u00e9rmica Processo de estrangulamento – processo isent\u00e1lpico Um\u00a0processo de estrangulamento\u00a0\u00e9 um\u00a0processo termodin\u00e2mico\u00a0, no qual a\u00a0entalpia\u00a0do g\u00e1s ou do meio\u00a0permanece constante (h = const)\u00a0.\u00a0De fato, o\u00a0processo de estrangulamento\u00a0\u00e9 um dos\u00a0processos … 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 limita\u00e7\u00e3o do vapor \u00famido - Defini\u00e7\u00e3o<\/title>\n<meta name=\"description\" content=\"A limita\u00e7\u00e3o do vapor \u00famido tamb\u00e9m est\u00e1 associada \u00e0 conserva\u00e7\u00e3o da entalpia. Nesse caso, uma redu\u00e7\u00e3o na press\u00e3o causa um aumento na qualidade do vapor. 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