{"id":48151,"date":"2019-11-08T07:58:47","date_gmt":"2019-11-08T06:58:47","guid":{"rendered":"https:\/\/www.thermal-engineering.org\/o-que-e-eficiencia-isentropica-turbina-compressor-bico-definicao\/"},"modified":"2020-01-27T17:09:25","modified_gmt":"2020-01-27T16:09:25","slug":"o-que-e-eficiencia-isentropica-turbina-compressor-bico-definicao","status":"publish","type":"post","link":"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-eficiencia-isentropica-turbina-compressor-bico-definicao\/","title":{"rendered":"O que \u00e9 Efici\u00eancia Isentr\u00f3pica – Turbina \/ Compressor \/ Bico – Defini\u00e7\u00e3o"},"content":{"rendered":"
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Efici\u00eancia isentr\u00f3pica \u00e9 a raz\u00e3o entre trabalho real e trabalho em condi\u00e7\u00f5es isentr\u00f3picas.\u00a0Geralmente \u00e9 definido para turbinas, compressores, bocais.\u00a0Engenharia T\u00e9rmica<\/div>\n<\/div>\n
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Efici\u00eancia isentr\u00f3pica – turbina, compressor, bocal<\/h2>\n

Nos cap\u00edtulos anteriores assumiu-se que a expans\u00e3o do g\u00e1s \u00e9\u00a0isentr\u00f3pica<\/strong>\u00a0e, portanto, utilizou-se\u00a0o t\u00a04, \u00e9<\/sub><\/strong>\u00a0\u00a0como a temperatura de sa\u00edda do g\u00e1s.\u00a0Essas premissas s\u00e3o aplic\u00e1veis \u200b\u200bapenas aos ciclos ideais.<\/p>\n

A maioria\u00a0dos dispositivos de fluxo constante<\/strong>\u00a0(turbinas, compressores, bicos) opera em\u00a0condi\u00e7\u00f5es adiab\u00e1ticas<\/strong>\u00a0, mas n\u00e3o s\u00e3o verdadeiramente isentr\u00f3picos, mas s\u00e3o idealizados como isentr\u00f3picos para fins de c\u00e1lculo.\u00a0Definimos os par\u00e2metros\u00a0\u03b7\u00a0<\/em><\/strong>T<\/sub><\/em><\/strong>\u00a0,\u00a0<\/em><\/strong>\u00a0\u03b7\u00a0<\/em><\/strong>C<\/sub><\/em><\/strong>\u00a0, \u03b7\u00a0<\/em><\/strong>N<\/sub><\/em><\/strong>\u00a0,<\/em><\/strong>\u00a0como uma\u00a0raz\u00e3o<\/strong>\u00a0entre\u00a0o trabalho real realizado<\/strong>\u00a0pelo dispositivo e o\u00a0trabalho por dispositivo quando operado em condi\u00e7\u00f5es isentr\u00f3picas<\/strong>\u00a0(no caso de turbinas).\u00a0Essa rela\u00e7\u00e3o \u00e9 conhecida como\u00a0efici\u00eancia isentr\u00f3pica de turbina \/ compressor \/ bico<\/strong>\u00a0.<\/p>\n

Esses par\u00e2metros descrevem com que efici\u00eancia uma turbina, compressor ou bico se aproxima de um dispositivo isentr\u00f3pico correspondente.\u00a0Este par\u00e2metro reduz a efici\u00eancia geral e a produ\u00e7\u00e3o do trabalho.\u00a0Para turbinas, o valor de\u00a0\u03b7\u00a0<\/em><\/strong>T<\/sub><\/em><\/strong>\u00a0\u00e9 tipicamente de 0,7 a 0,9 (70-90%).<\/p>\n

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

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\"Compress\u00e3o<\/a><\/p>\n

\"Expans\u00e3o<\/a>
O processo isentr\u00f3pico \u00e9 um caso especial de processos adiab\u00e1ticos.\u00a0\u00c9 um processo adiab\u00e1tico revers\u00edvel.\u00a0Um processo isentr\u00f3pico tamb\u00e9m pode ser chamado de processo de entropia constante.<\/figcaption><\/figure>\n<\/div>\n<\/div>\n
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<\/div>\n

Exemplo: Efici\u00eancia isentr\u00f3pica da turbina<\/h2>\n
\"Expans\u00e3o<\/a>
O processo isentr\u00f3pico \u00e9 um caso especial de processos adiab\u00e1ticos.\u00a0\u00c9 um processo adiab\u00e1tico revers\u00edvel.\u00a0Um processo isentr\u00f3pico tamb\u00e9m pode ser chamado de processo de entropia constante.<\/figcaption><\/figure>\n

Assuma uma\u00a0expans\u00e3o isentr\u00f3pica<\/strong>\u00a0de h\u00e9lio (3 \u2192 4) em uma turbina a g\u00e1s.\u00a0Nestas turbinas, o est\u00e1gio de alta press\u00e3o recebe g\u00e1s (ponto 3 na figura; p\u00a03<\/sub>\u00a0=\u00a06,7 MPa<\/strong>\u00a0; T\u00a03<\/sub>\u00a0= 1190 K (917 \u00b0 C)) de um trocador de calor e o esgota em outro trocador de calor, onde a press\u00e3o de sa\u00edda \u00e9 p\u00a04<\/sub>\u00a0=\u00a02,78 MPa<\/strong>\u00a0(ponto 4)\u00a0.\u00a0<\/strong>A temperatura (para processo isentr\u00f3pico) do g\u00e1s na sa\u00edda da turbina \u00e9 T\u00a04s<\/sub>\u00a0= 839 K (566 \u00b0 C).<\/p>\n

Calcule<\/strong>\u00a0o trabalho realizado por esta turbina e calcule a temperatura real na sa\u00edda da turbina, quando a\u00a0efici\u00eancia da turbina isentr\u00f3pica<\/strong>\u00a0for\u00a0\u03b7\u00a0<\/strong>T<\/sub><\/strong>\u00a0= 0,91 (91%)<\/strong>\u00a0.<\/p>\n

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

A partir da primeira lei da termodin\u00e2mica, o trabalho realizado pela turbina em um processo isentr\u00f3pico pode ser calculado a partir de:<\/span><\/p>\n

W\u00a0<\/span><\/strong>T<\/span><\/sub><\/strong>\u00a0= h\u00a0<\/span><\/strong>3<\/span><\/sub><\/strong>\u00a0– h\u00a0<\/span><\/strong>4s<\/span><\/sub><\/strong>\u00a0\u00a0\u00a0\u00a0\u00a0\u2192 W\u00a0<\/span><\/strong>Ts<\/span><\/sub><\/strong>\u00a0=\u00a0<\/span>c\u00a0<\/span><\/em><\/strong>p<\/span><\/sub><\/em><\/strong>\u00a0(T\u00a0<\/span><\/em><\/strong>3<\/span><\/sub><\/em><\/strong>\u00a0– T\u00a0<\/span><\/em><\/strong>4s<\/span><\/sub><\/em><\/strong>\u00a0)<\/span><\/em><\/strong><\/p>\n

Pela Lei do G\u00e1s Ideal, sabemos que o calor molar espec\u00edfico de um g\u00e1s ideal monat\u00f4mico \u00e9:<\/span><\/p>\n

C\u00a0<\/span><\/em><\/strong>v<\/span><\/sub><\/em><\/strong>\u00a0= 3 \/ 2R = 12,5 J \/ mol K<\/span><\/em><\/strong>\u00a0e<\/span>\u00a0C\u00a0<\/span><\/em><\/strong>p<\/span><\/sub><\/em><\/strong>\u00a0= C\u00a0<\/span><\/em><\/strong>v<\/span><\/sub><\/em><\/strong>\u00a0+ R = 5 \/ 2R = 20,8 J \/ mol K<\/span><\/em><\/strong><\/p>\n

Transferimos as capacidades de calor espec\u00edficas em unidades de\u00a0<\/span>J \/ kg K via:<\/span><\/strong><\/p>\n

c\u00a0<\/span><\/em><\/strong>p<\/span><\/sub><\/em><\/strong>\u00a0= C\u00a0<\/span><\/em><\/strong>p<\/span><\/sub><\/em><\/strong>\u00a0.\u00a01 \/ M (peso molar de h\u00e9lio) = 20,8 x 4,10\u00a0<\/span><\/em><\/strong>-3<\/span><\/sup><\/em><\/strong>\u00a0= 5200 J \/ kg K<\/span><\/em><\/strong><\/p>\n

O trabalho realizado pela turbina a g\u00e1s no processo isentr\u00f3pico \u00e9 ent\u00e3o:<\/span><\/p>\n

W\u00a0<\/span><\/em><\/strong>T, s<\/span><\/sub><\/em><\/strong>\u00a0= c\u00a0<\/span><\/em><\/strong>p<\/span><\/sub><\/em><\/strong>\u00a0(\u00a0<\/span><\/em><\/strong>T3<\/span><\/sub><\/em><\/strong>\u00a0–\u00a0<\/span><\/em><\/strong>T4s<\/span><\/sub><\/em><\/strong>\u00a0) = 5200 x (1190 – 839) = 1,825 MJ \/ kg<\/span><\/em><\/strong><\/p>\n

O trabalho real realizado pela turbina a g\u00e1s no processo adiab\u00e1tico \u00e9 ent\u00e3o:<\/span>
\nWT\u00a0<\/span><\/em><\/strong>, real<\/span><\/sub><\/em><\/strong>\u00a0=\u00a0<\/span><\/em><\/strong>cp<\/span><\/sub><\/em><\/strong>\u00a0(\u00a0<\/span><\/em><\/strong>T3<\/span><\/sub><\/em><\/strong>\u00a0–\u00a0<\/span><\/em><\/strong>T4s<\/span><\/sub><\/em><\/strong>\u00a0).\u00a0<\/span><\/em><\/strong>\u03b7\u00a0<\/span><\/em><\/strong>T<\/span><\/sub><\/em><\/strong>\u00a0= 5200 x (1190 – 839) x 0,91 = 1,661 MJ \/ kg<\/span><\/em><\/strong><\/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","protected":false},"excerpt":{"rendered":"

Efici\u00eancia isentr\u00f3pica \u00e9 a raz\u00e3o entre trabalho real e trabalho em condi\u00e7\u00f5es isentr\u00f3picas.\u00a0Geralmente \u00e9 definido para turbinas, compressores, bocais.\u00a0Engenharia T\u00e9rmica Efici\u00eancia isentr\u00f3pica – turbina, compressor, bocal Nos cap\u00edtulos anteriores assumiu-se que a expans\u00e3o do g\u00e1s \u00e9\u00a0isentr\u00f3pica\u00a0e, portanto, utilizou-se\u00a0o t\u00a04, \u00e9\u00a0\u00a0como a temperatura de sa\u00edda do g\u00e1s.\u00a0Essas premissas s\u00e3o aplic\u00e1veis \u200b\u200bapenas aos ciclos ideais. A maioria\u00a0dos … 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 Efici\u00eancia Isentr\u00f3pica - Turbina \/ Compressor \/ Bico - Defini\u00e7\u00e3o<\/title>\n<meta name=\"description\" content=\"Efici\u00eancia isentr\u00f3pica \u00e9 a raz\u00e3o entre trabalho real e trabalho em condi\u00e7\u00f5es isentr\u00f3picas. Geralmente \u00e9 definido para turbinas, compressores, bocais. 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