{"id":43879,"date":"2019-10-14T00:11:05","date_gmt":"2019-10-13T23:11:05","guid":{"rendered":"https:\/\/www.thermal-engineering.org\/quest-ce-que-la-convection-exemple-probleme-de-solution-definition\/"},"modified":"2020-02-17T08:54:00","modified_gmt":"2020-02-17T07:54:00","slug":"quest-ce-que-la-convection-exemple-probleme-de-solution-definition","status":"publish","type":"post","link":"https:\/\/www.thermal-engineering.org\/fr\/quest-ce-que-la-convection-exemple-probleme-de-solution-definition\/","title":{"rendered":"Qu&#8217;est-ce que la convection Exemple &#8211; Probl\u00e8me de solution &#8211; D\u00e9finition"},"content":{"rendered":"<div class=\"su-quote su-quote-style-default\">\n<div class=\"su-quote-inner su-clearfix\">Cet exemple montre comment calculer le transfert de chaleur par convection.\u00a0Calcul du coefficient de transfert de chaleur et de la temp\u00e9rature de la surface de la gaine.\u00a0G\u00e9nie thermique<\/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>Exemple &#8211; Convection &#8211; Temp\u00e9rature de surface de la gaine<\/h2>\n<p><strong><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Convection-Convective-Heat-Transfer-example.png\"><img loading=\"lazy\" class=\"alignright size-medium wp-image-20406 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Convection-Convective-Heat-Transfer-example-275x300.png\" alt=\"Convection - Transfert de chaleur par convection\" width=\"275\" height=\"300\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Convection-Convective-Heat-Transfer-example-275x300.png\" \/><\/a><\/strong><\/p>\n<p><strong>Exemple &#8211; Convection &#8211; Probl\u00e8me de solution\u00a0<\/strong><\/p>\n<p><strong>La gaine<\/strong>\u00a0est la couche externe des barres de combustible, situ\u00e9e entre le\u00a0<strong>fluide de refroidissement<\/strong>\u00a0du\u00a0<strong>r\u00e9acteur<\/strong>\u00a0et le\u00a0<a title=\"Combustible nucl\u00e9aire\" href=\"https:\/\/www.nuclear-power.com\/nuclear-power-plant\/nuclear-fuel\/\"><strong>combustible nucl\u00e9aire<\/strong><\/a>(c&#8217;est-\u00e0-dire\u00a0<strong>les pastilles de combustible<\/strong>\u00a0).\u00a0Il est fabriqu\u00e9 dans un mat\u00e9riau r\u00e9sistant \u00e0 la corrosion avec une section efficace d&#8217;absorption faible pour\u00a0<a title=\"Neutron thermique\" href=\"https:\/\/www.nuclear-power.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/fundamental-particles\/neutron\/thermal-neutron\/\">les neutrons thermiques<\/a>\u00a0, g\u00e9n\u00e9ralement un\u00a0<strong>alliage de zirconium<\/strong>\u00a0.\u00a0<strong>Le rev\u00eatement<\/strong>\u00a0emp\u00eache les produits de fission radioactifs de s&#8217;\u00e9chapper de la matrice de combustible dans le liquide de refroidissement du r\u00e9acteur et de le contaminer.\u00a0Les rev\u00eatements constituent l&#8217;un des obstacles \u00e0 l&#8217;\u00a0approche de\u00a0\u00ab\u00a0<strong>d\u00e9fense en profondeur<\/strong>\u00a0\u00bb; sa\u00a0<strong>capacit\u00e9 de refroidissement<\/strong>\u00a0est donc l&#8217;un des aspects cl\u00e9s de la s\u00e9curit\u00e9.<\/p>\n<p>Consid\u00e9rons la gaine de combustible de rayon int\u00e9rieur\u00a0<strong>r\u00a0<\/strong><strong><sub>Zr, 2<\/sub><\/strong><strong>\u00a0= 0,408 cm<\/strong>\u00a0et de rayon ext\u00e9rieur\u00a0<strong>r\u00a0<\/strong><strong><sub>Zr, 1<\/sub><\/strong><strong>\u00a0= 0,465 cm<\/strong>\u00a0.\u00a0En comparaison avec les pastilles de combustible, la gaine de combustible ne g\u00e9n\u00e8re presque pas de chaleur (la gaine est\u00a0<a href=\"https:\/\/www.nuclear-power.com\/nuclear-power\/fission\/energy-release-from-fission\/\">l\u00e9g\u00e8rement chauff\u00e9e par rayonnement<\/a>\u00a0).\u00a0Toute la chaleur g\u00e9n\u00e9r\u00e9e dans le carburant doit \u00eatre transf\u00e9r\u00e9e par\u00a0<a title=\"Conduction thermique - Conduction thermique\" href=\"https:\/\/www.thermal-engineering.org\/fr\/quest-ce-que-la-conduction-thermique-conduction-thermique-definition\/\"><strong>conduction \u00e0<\/strong><\/a>\u00a0travers la gaine et la surface interne est donc plus chaude que la surface externe.<\/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><span>Suppose que:<\/span><\/p>\n<ul>\n<li><span>le diam\u00e8tre ext\u00e9rieur du rev\u00eatement est:\u00a0<\/span><strong><span>d = 2 xr\u00a0<\/span><sub><span>Zr, 1<\/span><\/sub><span>\u00a0= 9,3 mm<\/span><\/strong><\/li>\n<li><span>le pas des goupilles de combustible est:\u00a0<\/span><strong><span>p = 13 mm<\/span><\/strong><\/li>\n<li><span>la\u00a0<\/span><a title=\"Conductivit\u00e9 thermique\" href=\"https:\/\/www.thermal-engineering.org\/fr\/quest-ce-que-la-conductivite-thermique-definition\/\"><span>conductivit\u00e9 thermique<\/span><\/a><span>\u00a0de l&#8217;\u00a0<\/span><a title=\"Liquide satur\u00e9 et sous-refroidi\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/materials-nuclear-engineering\/properties-steam-what-is-steam\/saturated-and-subcooled-liquid\/\"><span>eau satur\u00e9e<\/span><\/a><span>\u00a0\u00e0 300 \u00b0 C est:\u00a0<\/span><strong><span>k\u00a0<\/span><\/strong><strong><sub><span>H2O<\/span><\/sub><\/strong><strong><span>\u00a0= 0,545 W \/ mK<\/span><\/strong><\/li>\n<li><span>la viscosit\u00e9 dynamique de l&#8217;eau satur\u00e9e \u00e0 300 \u00b0 C est:\u00a0<\/span><strong><span>\u03bc = 0,0000859 Ns \/ m\u00a0<\/span><\/strong><strong><sup><span>2<\/span><\/sup><\/strong><\/li>\n<li><span>la\u00a0<\/span><a title=\"Qu'est-ce que la densit\u00e9 - Physique\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/thermodynamic-properties\/what-is-density-physics\/\"><span>densit\u00e9<\/span><\/a><span>\u00a0du fluide\u00a0est:\u00a0<\/span><strong><span>\u03c1 = 714 kg \/ m\u00a0<\/span><\/strong><strong><sup><span>3<\/span><\/sup><\/strong><\/li>\n<li><span>la\u00a0<\/span><a href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/laws-of-thermodynamics\/first-law-of-thermodynamics\/heat-capacity\/\"><strong><span>chaleur sp\u00e9cifique<\/span><\/strong><\/a><span>\u00a0est:\u00a0<\/span><strong><span>c\u00a0<\/span><\/strong><strong><sub><span>p<\/span><\/sub><\/strong><strong><span>\u00a0= 5,65 kJ \/ kg.K<\/span><\/strong><\/li>\n<li><span>la vitesse d&#8217;\u00e9coulement du c\u0153ur est constante et \u00e9gale \u00e0\u00a0<\/span><strong><span>V\u00a0<\/span><\/strong><strong><sub><span>c\u0153ur<\/span><\/sub><\/strong><strong><span>\u00a0= 5 m \/ s<\/span><\/strong><\/li>\n<li><span>la temp\u00e9rature du liquide de refroidissement du r\u00e9acteur \u00e0 cette coordonn\u00e9e axiale est:\u00a0<\/span><strong><span>T en\u00a0<\/span><\/strong><strong><sub><span>vrac<\/span><\/sub><\/strong><strong><span>\u00a0= 296 \u00b0 C<\/span><\/strong><\/li>\n<li><span>le taux de chaleur lin\u00e9aire du combustible est\u00a0<\/span><strong><span>q\u00a0<\/span><\/strong><strong><sub><span>L<\/span><\/sub><\/strong><strong><span>\u00a0= 300 W \/ cm<\/span><\/strong><span>\u00a0(F\u00a0<\/span><sub><span>Q<\/span><\/sub><span>\u00a0\u2248 2.0) et donc le taux de chaleur volum\u00e9trique est q\u00a0<\/span><sub><span>V<\/span><\/sub><span>\u00a0= 597 x 10\u00a0<\/span><sup><span>6<\/span><\/sup><span>\u00a0W \/ m\u00a0<\/span><sup><span>3<\/span><\/sup><\/li>\n<\/ul>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Hydraulic-Diameter-Fuel-Channel.png\"><img loading=\"lazy\" class=\"alignright size-medium wp-image-20407 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Hydraulic-Diameter-Fuel-Channel-254x300.png\" alt=\"Diam\u00e8tre hydraulique - Canal de carburant\" width=\"254\" height=\"300\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Hydraulic-Diameter-Fuel-Channel-254x300.png\" \/><\/a><span>Calculez le nombre de\u00a0<\/span><a title=\"Qu'est-ce que le num\u00e9ro Prandtl\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/heat-transfer\/introduction-to-heat-transfer\/characteristic-numbers\/what-is-prandtl-number\/\"><span>Prandtl<\/span><\/a><span>\u00a0,\u00a0<\/span><a title=\"Le num\u00e9ro de Reynold\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/reynolds-number\/\"><span>Reynolds<\/span><\/a><span>\u00a0et Nusselt pour ce r\u00e9gime d&#8217;\u00e9coulement (\u00e9coulement turbulent forc\u00e9 interne) \u00e0 l&#8217;int\u00e9rieur du r\u00e9seau rectangulaire de combustible (canal de combustible), puis calculez le\u00a0<\/span><strong><span>coefficient de transfert de chaleur<\/span><\/strong><span>\u00a0et enfin la\u00a0<\/span><strong><span>temp\u00e9rature de surface de<\/span><\/strong><span>\u00a0la\u00a0<strong>gaine<\/strong>\u00a0,\u00a0<\/span><strong><span>T\u00a0<\/span><sub><span>Zr, 1<\/span><\/sub><\/strong><span>\u00a0.<\/span><\/p>\n<p><span>Pour calculer la\u00a0<\/span><strong><span>temp\u00e9rature de surface de<\/span><\/strong><span>\u00a0la\u00a0<strong>gaine<\/strong>\u00a0, nous devons calculer le nombre de\u00a0<\/span><strong><span>Prandtl<\/span><\/strong><span>\u00a0,\u00a0<\/span><strong><span>Reynolds<\/span><\/strong><span>\u00a0et\u00a0<\/span><strong><span>Nusselt<\/span><\/strong><span>\u00a0, car le transfert de chaleur pour ce r\u00e9gime d&#8217;\u00e9coulement peut \u00eatre d\u00e9crit par l&#8217;\u00a0<\/span><strong><span>\u00e9quation de Dittus-Boelter<\/span><\/strong><span>\u00a0, qui est:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Dittus-Boelter-Equation-Formula.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20409 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Dittus-Boelter-Equation-Formula.png\" alt=\"\u00c9quation Dittus-Boelter - Formule\" width=\"556\" height=\"278\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Dittus-Boelter-Equation-Formula.png\" \/><\/a><\/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>Calcul du nombre de Prandtl<\/span><\/h2>\n<p><span>Pour calculer le\u00a0<\/span><a title=\"Qu'est-ce que le num\u00e9ro Prandtl\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/heat-transfer\/introduction-to-heat-transfer\/characteristic-numbers\/what-is-prandtl-number\/\"><span>nombre de Prandtl<\/span><\/a><span>\u00a0, nous devons savoir:<\/span><\/p>\n<ul>\n<li><span>la conductivit\u00e9 thermique de l&#8217;eau satur\u00e9e \u00e0 300 \u00b0 C est:\u00a0<\/span><strong><span>k\u00a0<\/span><\/strong><strong><sub><span>H2O<\/span><\/sub><\/strong><strong><span>\u00a0= 0,545 W \/ mK<\/span><\/strong><\/li>\n<li><span>la viscosit\u00e9 dynamique de l&#8217;eau satur\u00e9e \u00e0 300 \u00b0 C est:\u00a0<\/span><strong><span>\u03bc = 0,0000859 Ns \/ m\u00a0<\/span><\/strong><strong><sup><span>2<\/span><\/sup><\/strong><\/li>\n<li><span>la\u00a0<\/span><a href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/laws-of-thermodynamics\/first-law-of-thermodynamics\/heat-capacity\/\"><strong><span>chaleur sp\u00e9cifique<\/span><\/strong><\/a><span>\u00a0est:\u00a0<\/span><strong><span>c\u00a0<\/span><\/strong><strong><sub><span>p<\/span><\/sub><\/strong><strong><span>\u00a0= 5,65 kJ \/ kg.K<\/span><\/strong><\/li>\n<\/ul>\n<p><span>Notez que tous ces param\u00e8tres diff\u00e8rent de mani\u00e8re significative pour l&#8217;eau \u00e0 300 \u00b0 C de ceux \u00e0 20 \u00b0 C.\u00a0Le nombre de Prandtl pour l&#8217;\u00a0<\/span><a href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/materials-nuclear-engineering\/properties-of-water\/\"><span>eau<\/span><\/a><span>\u00a0\u00e0 20 \u00b0 C est d&#8217;environ\u00a0<\/span><strong><span>6,91.\u00a0<\/span><\/strong><span>Le nombre de Prandtl pour le liquide de refroidissement du r\u00e9acteur \u00e0 300 \u00b0 C est alors:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/prandtl-number-example.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20411 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/prandtl-number-example.png\" alt=\"num\u00e9ro prandtl - exemple\" width=\"469\" height=\"80\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/prandtl-number-example.png\" \/><\/a><\/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>Calcul du nombre de Reynolds<\/span><\/h2>\n<p><span>Pour calculer le nombre de Reynolds, nous devons savoir:<\/span><\/p>\n<ul>\n<li><span>le diam\u00e8tre ext\u00e9rieur du rev\u00eatement est:\u00a0<\/span><strong><span>d = 2 xr\u00a0<\/span><sub><span>Zr, 1<\/span><\/sub><span>\u00a0= 9,3 mm<\/span><\/strong><span>\u00a0(pour calculer le diam\u00e8tre hydraulique)<\/span><\/li>\n<li><span>le pas des goupilles de combustible est:\u00a0<\/span><strong><span>p = 13 mm<\/span><\/strong><span>\u00a0\u00a0(pour calculer le diam\u00e8tre hydraulique)<\/span><\/li>\n<li><span>la viscosit\u00e9 dynamique de l&#8217;eau satur\u00e9e \u00e0 300 \u00b0 C est:\u00a0<\/span><strong><span>\u03bc = 0,0000859 Ns \/ m\u00a0<\/span><\/strong><strong><sup><span>2<\/span><\/sup><\/strong><\/li>\n<li><span>la densit\u00e9 du fluide est:\u00a0<\/span><strong><span>\u03c1 = 714 kg \/ m\u00a0<\/span><\/strong><strong><sup><span>3<\/span><\/sup><\/strong><\/li>\n<\/ul>\n<p><strong><span>Le diam\u00e8tre hydraulique, D\u00a0<\/span><\/strong><strong><sub><span>h<\/span><\/sub><\/strong><span>\u00a0, est un terme couramment utilis\u00e9 pour g\u00e9rer le d\u00e9bit dans\u00a0<\/span><strong><span>des tubes et canaux non circulaires<\/span><\/strong><span>\u00a0.\u00a0Le\u00a0<\/span><strong><span>diam\u00e8tre hydraulique du canal de carburant<\/span><\/strong><span>\u00a0,\u00a0<\/span><em><span>D\u00a0<\/span><\/em><em><sub><span>h<\/span><\/sub><\/em><span>\u00a0, est \u00e9gal \u00e0 13,85 mm.<\/span><\/p>\n<p><span>Voir aussi:\u00a0<\/span><a title=\"Diam\u00e8tre hydraulique\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/internal-flow\/hydraulic-diameter-2\/\"><span>Diam\u00e8tre hydraulique<\/span><\/a><\/p>\n<p><span>Le\u00a0<\/span><strong><span>nombre de Reynolds<\/span><\/strong><span>\u00a0\u00e0 l&#8217;int\u00e9rieur du canal de carburant est alors \u00e9gal \u00e0:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/reynolds-number-example.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20412 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/reynolds-number-example.png\" alt=\"nombre de reynolds - exemple\" width=\"593\" height=\"78\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/reynolds-number-example.png\" \/><\/a><\/p>\n<p><span>Cela satisfait pleinement les\u00a0<\/span><a title=\"\u00c9coulement turbulent\" href=\"https:\/\/www.thermal-engineering.org\/fr\/quest-ce-quun-ecoulement-turbulent-definition\/\"><strong><span>conditions turbulentes<\/span><\/strong><\/a><span>\u00a0.<\/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>Calcul du nombre de Nusselt \u00e0 l&#8217;aide de l&#8217;\u00e9quation de Dittus-Boelter<\/span><\/h2>\n<p><span>Pour un \u00e9coulement turbulent pleinement d\u00e9velopp\u00e9 (hydrodynamiquement et thermiquement) dans un tube circulaire lisse, le\u00a0<\/span><strong><span>nombre de Nusselt<\/span><\/strong><span>\u00a0local\u00a0peut \u00eatre obtenu \u00e0 partir de l&#8217;\u00a0<\/span><strong><span>\u00e9quation<\/span><\/strong><span>\u00a0bien connue de\u00a0<strong>Dittus ?? Boelter<\/strong>\u00a0.<\/span><\/p>\n<p><span>Pour calculer le\u00a0<\/span><strong><span>nombre de Nusselt<\/span><\/strong><span>\u00a0, nous devons savoir:<\/span><\/p>\n<ul>\n<li><span>le\u00a0<\/span><a title=\"Le num\u00e9ro de Reynold\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/fluid-dynamics\/reynolds-number\/\"><span>nombre de Reynolds<\/span><\/a><span>\u00a0, qui est\u00a0<\/span><strong><span>Re\u00a0<\/span><sub><span>Dh<\/span><\/sub><span>\u00a0= 575600<\/span><\/strong><\/li>\n<li><span>le\u00a0<\/span><a title=\"Qu'est-ce que le num\u00e9ro Prandtl\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/heat-transfer\/introduction-to-heat-transfer\/characteristic-numbers\/what-is-prandtl-number\/\"><span>nombre de Prandtl<\/span><\/a><span>\u00a0, qui est\u00a0<\/span><strong><span>Pr = 0,89<\/span><\/strong><\/li>\n<\/ul>\n<p><span>Le\u00a0<\/span><strong><span>nombre de Nusselt<\/span><\/strong><span>\u00a0pour la convection forc\u00e9e \u00e0 l&#8217;int\u00e9rieur du canal de carburant est alors \u00e9gal \u00e0:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/nusselt-number-example.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20413 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/nusselt-number-example.png\" alt=\"num\u00e9ro nusselt - exemple\" width=\"387\" height=\"58\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/nusselt-number-example.png\" \/><\/a><\/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>Calcul du coefficient de transfert de chaleur et de la temp\u00e9rature de surface du rev\u00eatement, T\u00a0<\/span><sub><span>Zr, 1<\/span><\/sub><\/h2>\n<p><span>Une connaissance d\u00e9taill\u00e9e de la g\u00e9om\u00e9trie, des param\u00e8tres des fluides, du rayon ext\u00e9rieur du rev\u00eatement, du taux de chaleur lin\u00e9aire, du coefficient de transfert de chaleur par convection nous permet de calculer la diff\u00e9rence de temp\u00e9rature\u00a0<\/span><strong><span>\u2206T<\/span><\/strong><span>\u00a0entre le liquide de refroidissement (T en\u00a0<\/span><sub><span>vrac<\/span><\/sub><span>\u00a0) et la surface du rev\u00eatement (T\u00a0<\/span><sub><span>Zr, 1<\/span><\/sub><span>\u00a0).<\/span><\/p>\n<p><span>Pour calculer la temp\u00e9rature de surface de la gaine, il faut savoir:<\/span><\/p>\n<ul>\n<li><span>le diam\u00e8tre ext\u00e9rieur du rev\u00eatement est: d = 2 x\u00a0<\/span><strong><span>r\u00a0<\/span><\/strong><strong><sub><span>Zr, 1<\/span><\/sub><\/strong><strong><span>\u00a0= 9,3 mm<\/span><\/strong><\/li>\n<li><span>le nombre de Nusselt, qui est\u00a0<\/span><strong><span>Nu\u00a0<\/span><\/strong><strong><sub><span>Dh<\/span><\/sub><\/strong><strong><span>\u00a0= 890<\/span><\/strong><\/li>\n<li><span>le diam\u00e8tre hydraulique du canal de carburant est:\u00a0<\/span><strong><em><span>D\u00a0<\/span><\/em><\/strong><strong><em><sub><span>h<\/span><\/sub><\/em><\/strong><strong><span>\u00a0= 13,85 mm<\/span><\/strong><\/li>\n<li><span>la conductivit\u00e9 thermique du liquide de refroidissement du r\u00e9acteur (300 \u00b0 C) est:\u00a0<\/span><strong><span>k\u00a0<\/span><\/strong><strong><sub><span>H2O<\/span><\/sub><\/strong><strong><span>\u00a0= 0,545 W \/ mK<\/span><\/strong><\/li>\n<li><span>la temp\u00e9rature en vrac du liquide de refroidissement du r\u00e9acteur \u00e0 cette coordonn\u00e9e axiale est:\u00a0<\/span><strong><span>T en\u00a0<\/span><\/strong><strong><sub><span>vrac<\/span><\/sub><\/strong><strong><span>\u00a0= 296 \u00b0 C<\/span><\/strong><\/li>\n<li><span>le taux de chaleur lin\u00e9aire du combustible est:\u00a0<\/span><strong><span>q\u00a0<\/span><\/strong><strong><sub><span>L<\/span><\/sub><\/strong><strong><span>\u00a0= 300 W \/ cm<\/span><\/strong><span>\u00a0(F\u00a0<\/span><sub><span>Q<\/span><\/sub><span>\u00a0\u2248 2.0)<\/span><\/li>\n<\/ul>\n<p><span>Le coefficient de transfert de chaleur par convection,\u00a0<\/span><strong><span>h<\/span><\/strong><span>\u00a0, est donn\u00e9 directement par la d\u00e9finition du nombre de Nusselt:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/convective-heat-transfer-coefficient-example.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20410 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/convective-heat-transfer-coefficient-example.png\" alt=\"coefficient de transfert de chaleur par convection - exemple\" width=\"619\" height=\"92\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/convective-heat-transfer-coefficient-example.png\" \/><\/a><\/p>\n<p><span>Enfin, nous pouvons calculer la temp\u00e9rature de surface de la gaine (T\u00a0<\/span><sub><span>Zr, 1<\/span><\/sub><span>\u00a0) simplement en utilisant la\u00a0<\/span><strong><span>loi de Newton du refroidissement<\/span><\/strong><span>\u00a0:<\/span><\/p>\n<p><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Newton-law-of-cooling-example.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-20408 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Newton-law-of-cooling-example.png\" alt=\"Loi de Newton du refroidissement - exemple\" width=\"377\" height=\"369\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Newton-law-of-cooling-example.png\" \/><\/a><\/p>\n<p><span>Pour les REP en fonctionnement normal, il y a une\u00a0<\/span><a href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/materials-nuclear-engineering\/properties-steam-what-is-steam\/saturated-and-subcooled-liquid\/\"><span>eau liquide comprim\u00e9e \u00e0 l&#8217;<\/span><\/a><span>\u00a0int\u00e9rieur du c\u0153ur du r\u00e9acteur, des boucles et des g\u00e9n\u00e9rateurs de vapeur.\u00a0La pression est maintenue \u00e0 environ\u00a0<\/span><strong><span>16 MPa<\/span><\/strong><span>\u00a0.\u00a0\u00c0 cette pression, l&#8217;eau bout \u00e0 environ\u00a0<\/span><strong><span>350 \u00b0 C<\/span><\/strong><span>\u00a0(662 \u00b0 F).\u00a0Comme on peut le voir, la temp\u00e9rature de surface T\u00a0<\/span><sub><span>Zr, 1<\/span><\/sub><span>\u00a0= 325 \u00b0 C garantit que m\u00eame une \u00e9bullition sous-refroidie ne se produit pas.\u00a0Notez que l&#8217;\u00e9bullition sous-refroidie n\u00e9cessite T\u00a0<\/span><sub><span>Zr, 1<\/span><\/sub><span>\u00a0= T\u00a0<\/span><sub><span>sat<\/span><\/sub><span>\u00a0.\u00a0\u00c9tant donn\u00e9 que les temp\u00e9ratures d&#8217;entr\u00e9e de l&#8217;eau sont g\u00e9n\u00e9ralement d&#8217;environ\u00a0<\/span><strong><span>290 \u00b0 C<\/span><\/strong><span>(554 \u00b0 F), il est \u00e9vident que cet exemple correspond \u00e0 la partie inf\u00e9rieure du noyau.\u00a0Aux altitudes plus \u00e9lev\u00e9es du c\u0153ur, la temp\u00e9rature globale peut atteindre jusqu&#8217;\u00e0 330 \u00b0 C.\u00a0La diff\u00e9rence de temp\u00e9rature de 29 \u00b0 C peut entra\u00eener une \u00e9bullition sous-refroidie (330 \u00b0 C + 29 \u00b0 C&gt; 350 \u00b0 C).\u00a0D&#8217;autre part, l&#8217;\u00a0<\/span><strong><span>\u00e9bullition nucl\u00e9\u00e9e<\/span><\/strong><span>\u00a0\u00e0 la surface perturbe efficacement la couche stagnante et, par cons\u00e9quent, l&#8217;\u00e9bullition nucl\u00e9\u00e9e augmente consid\u00e9rablement la capacit\u00e9 d&#8217;une surface \u00e0 transf\u00e9rer l&#8217;\u00a0<\/span><a href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/what-is-energy-physics\/internal-energy-thermal-energy\/\"><span>\u00e9nergie thermique<\/span><\/a><span>\u00a0au fluide en vrac.\u00a0En cons\u00e9quence, le coefficient de transfert de chaleur convectif augmente consid\u00e9rablement et donc \u00e0 des altitudes plus \u00e9lev\u00e9es, la diff\u00e9rence de temp\u00e9rature (T\u00a0<\/span><sub><span>Zr, 1<\/span><\/sub><span>\u00a0&#8211; T en\u00a0<\/span><sub><span>vrac<\/span><\/sub><span>\u00a0) diminue consid\u00e9rablement.<\/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\"><\/div>\n<\/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>Cet article est bas\u00e9 sur la traduction automatique de l&#8217;article original en anglais. Pour plus d&#8217;informations, voir l&#8217;article en anglais. Pouvez vous nous aider Si vous souhaitez corriger la traduction, envoyez-la \u00e0 l&#8217;adresse: translations@nuclear-power.com ou remplissez le formulaire de traduction en ligne. Nous appr\u00e9cions votre aide, nous mettrons \u00e0 jour la traduction le plus rapidement possible. Merci<\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>Cet exemple montre comment calculer le transfert de chaleur par convection.\u00a0Calcul du coefficient de transfert de chaleur et de la temp\u00e9rature de la surface de la gaine.\u00a0G\u00e9nie thermique Exemple &#8211; Convection &#8211; Temp\u00e9rature de surface de la gaine Exemple &#8211; Convection &#8211; Probl\u00e8me de solution\u00a0 La gaine\u00a0est la couche externe des barres de combustible, situ\u00e9e &#8230; <a title=\"Qu&#8217;est-ce que la convection Exemple &#8211; Probl\u00e8me de solution &#8211; D\u00e9finition\" class=\"read-more\" href=\"https:\/\/www.thermal-engineering.org\/fr\/quest-ce-que-la-convection-exemple-probleme-de-solution-definition\/\" aria-label=\"En savoir plus sur Qu&#8217;est-ce que la convection Exemple &#8211; Probl\u00e8me de solution &#8211; D\u00e9finition\">Lire la suite<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[8],"tags":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v15.4 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Qu&#039;est-ce que la convection Exemple - Probl\u00e8me de solution - D\u00e9finition<\/title>\n<meta name=\"description\" content=\"Cet exemple montre comment calculer le transfert de chaleur par convection. 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