{"id":40073,"date":"2019-09-17T14:15:54","date_gmt":"2019-09-17T13:15:54","guid":{"rendered":"https:\/\/www.thermal-engineering.org\/que-es-el-numero-de-rayleigh-definicion\/"},"modified":"2020-01-07T08:54:11","modified_gmt":"2020-01-07T07:54:11","slug":"que-es-el-numero-de-rayleigh-definicion","status":"publish","type":"post","link":"https:\/\/www.thermal-engineering.org\/es\/que-es-el-numero-de-rayleigh-definicion\/","title":{"rendered":"\u00bfQu\u00e9 es el n\u00famero de Rayleigh? Definici\u00f3n"},"content":{"rendered":"<div class=\"su-quote su-quote-style-default\">\n<div class=\"su-quote-inner su-clearfix\">El n\u00famero de Rayleigh es un n\u00famero adimensional, llamado as\u00ed por Lord Rayleigh.\u00a0El n\u00famero de Rayleigh se utiliza para expresar la transferencia de calor en convecci\u00f3n natural.\u00a0Ingenieria termal<\/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>\u00bfQu\u00e9 es el n\u00famero de Rayleigh?<\/h2>\n<p>El\u00a0<strong>n\u00famero de Rayleigh<\/strong>\u00a0es un n\u00famero adimensional, llamado as\u00ed por Lord Rayleigh.\u00a0El\u00a0<strong>n\u00famero de Rayleigh<\/strong>\u00a0\u00a0est\u00e1 estrechamente relacionado con el n\u00famero de Grashof y ambos n\u00fameros se usan para describir la convecci\u00f3n natural (Gr) y la transferencia de calor por convecci\u00f3n natural (Ra).\u00a0El\u00a0\u00a0<strong>n\u00famero de Rayleigh<\/strong>\u00a0\u00a0se define simplemente como el producto del\u00a0<a title=\"\u00bfQu\u00e9 es el n\u00famero de Grashof?\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/heat-transfer\/introduction-to-heat-transfer\/characteristic-numbers\/what-is-grashof-number\/\">n\u00famero de Grashof<\/a>\u00a0, que describe la relaci\u00f3n entre flotabilidad y viscosidad dentro de un fluido, y el\u00a0<a title=\"\u00bfQu\u00e9 es el n\u00famero de Prandtl?\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/heat-transfer\/introduction-to-heat-transfer\/characteristic-numbers\/what-is-prandtl-number\/\">n\u00famero de Prandtl<\/a>\u00a0, que describe la relaci\u00f3n entre la difusividad de momento y la difusividad t\u00e9rmica.<\/p>\n<p><strong>Ra\u00a0<sub>x<\/sub>\u00a0= Gr\u00a0<sub>x<\/sub>\u00a0.\u00a0Pr<\/strong><\/p>\n<p>El\u00a0\u00a0<strong>n\u00famero de Grashof<\/strong>\u00a0\u00a0se define como la relaci\u00f3n entre la fuerza de flotaci\u00f3n y la fuerza viscosa que act\u00faa sobre un fluido en la capa l\u00edmite de velocidad.\u00a0Su papel en la convecci\u00f3n natural es muy similar al del\u00a0\u00a0<a title=\"Numero Reynolds\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/reynolds-number\/\">n\u00famero de Reynolds<\/a>\u00a0\u00a0en convecci\u00f3n forzada.\u00a0La convecci\u00f3n natural ocurre si este movimiento y la mezcla son causados \u200b\u200bpor\u00a0variaciones de\u00a0<a title=\"\u00bfQu\u00e9 es la densidad? - F\u00edsica\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/thermodynamic-properties\/what-is-density-physics\/\">densidad<\/a>\u00a0resultantes de las diferencias de temperatura dentro del fluido.\u00a0Por lo general, la densidad disminuye debido a un aumento de la\u00a0<a title=\"\u00bfQu\u00e9 es la temperatura? F\u00edsica\" href=\"https:\/\/www.thermal-engineering.org\/es\/que-es-la-temperatura-fisica-definicion\/\">temperatura<\/a>\u00a0y hace que el l\u00edquido suba.\u00a0Este movimiento es causado por la fuerza de flotaci\u00f3n.\u00a0La fuerza principal que resiste el movimiento es la fuerza viscosa.\u00a0El n\u00famero de Grashof es una forma de cuantificar las fuerzas opuestas.<\/p>\n<p>El\u00a0<strong>n\u00famero de Rayleigh<\/strong>\u00a0se utiliza para expresar la transferencia de calor en convecci\u00f3n natural.\u00a0La magnitud del n\u00famero de Rayleigh es una buena indicaci\u00f3n de si la capa l\u00edmite de convecci\u00f3n natural es laminar o turbulenta.\u00a0Las correlaciones emp\u00edricas simples para el n\u00famero de Nusselt promedio, Nu, en convecci\u00f3n natural son de la forma:<\/p>\n<p><strong>Nu\u00a0<sub>x<\/sub>\u00a0\u00a0= C. Ra\u00a0<sub>x\u00a0<\/sub><sup>n<\/sup><\/strong><\/p>\n<p>Los valores de las\u00a0<strong>constantes C<\/strong>\u00a0y\u00a0<strong>n<\/strong>\u00a0dependen de la geometr\u00eda de la superficie y el\u00a0<a title=\"R\u00e9gimen de flujo\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/flow-regime\/\">r\u00e9gimen de flujo<\/a>\u00a0, que se caracteriza por el rango del\u00a0<strong>n\u00famero de Rayleigh<\/strong>\u00a0.\u00a0El valor de n suele ser n = 1\/4 para flujo laminar y n = 1\/3 para flujo turbulento.<\/p>\n<p>El\u00a0\u00a0<strong>n\u00famero de Rayleigh<\/strong>\u00a0se define como:<\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/rayleigh-number-definition-formula.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20353 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/rayleigh-number-definition-formula.png\" alt=\"n\u00famero rayleigh - definici\u00f3n - f\u00f3rmula\" width=\"381\" height=\"354\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/rayleigh-number-definition-formula.png\" \/><\/a><\/p>\n<p><span>d\u00f3nde:<\/span><\/p>\n<p><span>g es la aceleraci\u00f3n debido a la gravedad de la Tierra<\/span><\/p>\n<p><span>\u03b2 es el coeficiente de expansi\u00f3n t\u00e9rmica<\/span><\/p>\n<p><span>T\u00a0<\/span><sub><span>wall<\/span><\/sub><span>\u00a0es la temperatura de la pared<\/span><\/p>\n<p><span>T\u00a0<\/span><sub><span>\u221e<\/span><\/sub><span>\u00a0es la temperatura a granel<\/span><\/p>\n<p><span>L es la longitud vertical<\/span><\/p>\n<p><span>\u03b1 es\u00a0\u00a0<\/span><a title=\"Difusividad T\u00e9rmica\" href=\"https:\/\/www.thermal-engineering.org\/es\/que-es-la-difusividad-termica-definicion\/\"><span>difusividad t\u00e9rmica<\/span><\/a><\/p>\n<p><span>\u03bd es la viscosidad cinem\u00e1tica.<\/span><\/p>\n<p><span>Para gases \u03b2 = 1 \/ T donde la temperatura est\u00e1 en K. Para l\u00edquidos se puede calcular \u03b2 si se conoce la variaci\u00f3n de densidad con temperatura a presi\u00f3n constante.\u00a0Para una placa plana vertical, el flujo se vuelve\u00a0<\/span><a title=\"Flujo turbulento\" href=\"https:\/\/www.thermal-engineering.org\/es\/que-es-el-flujo-turbulento-definicion\/\"><span>turbulento<\/span><\/a><span>\u00a0por un valor de:<\/span><\/p>\n<p><strong><span>Ra\u00a0<\/span><sub><span>x<\/span><\/sub><span>\u00a0\u00a0= Gr\u00a0<\/span><sub><span>x<\/span><\/sub><span>\u00a0\u00a0.\u00a0Pr&gt; 10\u00a0<\/span><sup><span>9<\/span><\/sup>\u00a0<\/strong><\/p>\n<p><span>Al igual que en la convecci\u00f3n forzada, la naturaleza microsc\u00f3pica del flujo y las correlaciones de convecci\u00f3n son claramente diferentes en las\u00a0regiones\u00a0<\/span><a title=\"Flujo Laminar - Flujo Viscoso\" href=\"https:\/\/www.thermal-engineering.org\/es\/que-es-el-flujo-laminar-flujo-viscoso-definicion\/\"><span>laminar<\/span><\/a><span>\u00a0y\u00a0<\/span><a title=\"Flujo turbulento\" href=\"https:\/\/www.thermal-engineering.org\/es\/que-es-el-flujo-turbulento-definicion\/\"><span>turbulenta<\/span><\/a><span>\u00a0.<\/span><\/p>\n<h2><strong><span>Ejemplo: n\u00famero de Rayleigh<\/span><\/strong><\/h2>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Rayleigh-Number-and-Grashof-Number.png\"><img loading=\"lazy\" class=\"alignright size-full wp-image-20349 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Rayleigh-Number-and-Grashof-Number.png\" alt=\"N\u00famero de Rayleigh y n\u00famero de Grashof\" width=\"404\" height=\"425\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Rayleigh-Number-and-Grashof-Number.png\" \/><\/a><span>Una placa vertical se mantiene a 50 \u00b0 C en 20 \u00b0 C de aire.\u00a0Determine la altura a la cual la capa l\u00edmite se volver\u00e1 turbulenta si la turbulencia se establece en Ra = Gr.Pr = 10\u00a0<\/span><sup><span>9<\/span><\/sup><span>\u00a0.<\/span><\/p>\n<p><span>Soluci\u00f3n:<\/span><\/p>\n<p><span>Los valores de propiedad requeridos para este ejemplo son:<\/span><\/p>\n<p><span>\u03bd = 1,48 x\u00a0<\/span><sup><span>10-5<\/span><\/sup><span>\u00a0m\u00a0<\/span><sup><span>2<\/span><\/sup><span>\u00a0\/ s<\/span><\/p>\n<p><span>\u03c1 = 1,17 kg \/ m\u00a0<\/span><sup><span>3<\/span><\/sup><\/p>\n<p><span>Pr = 0.700<\/span><\/p>\n<p><span>\u03b2 = 1 \/ (273 + 20) = 1\/293<\/span><\/p>\n<p><span>Sabemos que la circulaci\u00f3n natural se vuelve turbulenta a aproximadamente Ra = Gr.Pr&gt; 10\u00a0<\/span><sup><span>9<\/span><\/sup><span>\u00a0, que se cumple a la siguiente altura:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/grashof-number-example.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20338 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/grashof-number-example.png\" alt=\"n\u00famero grashof - ejemplo\" width=\"607\" height=\"142\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/grashof-number-example.png\" \/><\/a><\/p>\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<\/div>\n<\/div>\n<p>Este art\u00edculo se basa en la traducci\u00f3n autom\u00e1tica del art\u00edculo original en ingl\u00e9s. Para m\u00e1s informaci\u00f3n vea el art\u00edculo en ingl\u00e9s. Puedes ayudarnos. Si desea corregir la traducci\u00f3n, env\u00edela a: translations@nuclear-power.com o complete el formulario de traducci\u00f3n en l\u00ednea. Agradecemos su ayuda, actualizaremos la traducci\u00f3n lo antes posible. Gracias.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>El n\u00famero de Rayleigh es un n\u00famero adimensional, llamado as\u00ed por Lord Rayleigh.\u00a0El n\u00famero de Rayleigh se utiliza para expresar la transferencia de calor en convecci\u00f3n natural.\u00a0Ingenieria termal \u00bfQu\u00e9 es el n\u00famero de Rayleigh? El\u00a0n\u00famero de Rayleigh\u00a0es un n\u00famero adimensional, llamado as\u00ed por Lord Rayleigh.\u00a0El\u00a0n\u00famero de Rayleigh\u00a0\u00a0est\u00e1 estrechamente relacionado con el n\u00famero de Grashof y &#8230; <a title=\"\u00bfQu\u00e9 es el n\u00famero de Rayleigh? Definici\u00f3n\" class=\"read-more\" href=\"https:\/\/www.thermal-engineering.org\/es\/que-es-el-numero-de-rayleigh-definicion\/\" aria-label=\"M\u00e1s en \u00bfQu\u00e9 es el n\u00famero de Rayleigh? Definici\u00f3n\">Leer m\u00e1s<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[16],"tags":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v15.4 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>\u00bfQu\u00e9 es el n\u00famero de Rayleigh? Definici\u00f3n<\/title>\n<meta name=\"description\" content=\"El n\u00famero de Rayleigh es un n\u00famero adimensional, llamado as\u00ed por Lord Rayleigh. El n\u00famero de Rayleigh se utiliza para expresar la transferencia de calor en convecci\u00f3n natural. 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