{"id":49455,"date":"2019-11-19T00:33:30","date_gmt":"2019-11-18T23:33:30","guid":{"rendered":"https:\/\/www.thermal-engineering.org\/quest-ce-que-le-changement-denthalpie-delta-h-definition\/"},"modified":"2020-02-25T17:03:00","modified_gmt":"2020-02-25T16:03:00","slug":"quest-ce-que-le-changement-denthalpie-delta-h-definition","status":"publish","type":"post","link":"https:\/\/www.thermal-engineering.org\/fr\/quest-ce-que-le-changement-denthalpie-delta-h-definition\/","title":{"rendered":"Qu&#8217;est-ce que le changement d&#8217;enthalpie &#8211; delta h &#8211; D\u00e9finition"},"content":{"rendered":"<div class=\"su-quote su-quote-style-default\">\n<div class=\"su-quote-inner su-clearfix\">L&#8217;enthalpie est repr\u00e9sent\u00e9e par le symbole H et le changement d&#8217;enthalpie dans un processus (delta h) est H2 &#8211; H1. Delta h est calcul\u00e9 ici pour divers exemples. G\u00e9nie thermique<\/div>\n<\/div>\n<div><\/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>Enthalpie en unit\u00e9s extensives<\/span><\/h2>\n<figure id=\"attachment_16538\" class=\"wp-caption alignright\" aria-describedby=\"caption-attachment-16538\"><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Extensive-vs.-Intensive-properties-min.png\"><img loading=\"lazy\" class=\"size-medium wp-image-16538 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Extensive-vs.-Intensive-properties-min-238x300.png\" alt=\"Propri\u00e9t\u00e9s thermodynamiques \u00e9tendues et intensives\" width=\"238\" height=\"300\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Extensive-vs.-Intensive-properties-min-238x300.png\" \/><\/a><figcaption id=\"caption-attachment-16538\" class=\"wp-caption-text\"><span>Propri\u00e9t\u00e9s extensives et intensives du milieu dans le pressuriseur.<\/span><\/figcaption><\/figure>\n<p><em><strong><span>H = U + pV<\/span><\/strong><\/em><\/p>\n<p><a title=\"Qu'est-ce que l'enthalpie\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/what-is-energy-physics\/what-is-enthalpy\/\"><strong><span>L&#8217;enthalpie<\/span><\/strong><\/a><span>\u00a0\u00a0est une quantit\u00e9 importante, elle d\u00e9pend de la taille du syst\u00e8me ou de la quantit\u00e9 de substance qu&#8217;il contient.\u00a0L&#8217;unit\u00e9 SI d&#8217;enthalpie est le joule (J).\u00a0Il s&#8217;agit de l&#8217;\u00e9nergie contenue dans le syst\u00e8me, \u00e0 l&#8217;exclusion de l&#8217;\u00e9nergie cin\u00e9tique de mouvement du syst\u00e8me dans son ensemble et de l&#8217;\u00e9nergie potentielle du syst\u00e8me dans son ensemble en raison des champs de force externes.\u00a0Il s&#8217;agit de la quantit\u00e9 thermodynamique \u00e9quivalente au<\/span><strong><span>\u00a0contenu calorifique total<\/span><\/strong><span>\u00a0d&#8217;un syst\u00e8me.<\/span><\/p>\n<p><span>D&#8217;un autre c\u00f4t\u00e9, l&#8217;\u00e9nergie peut \u00eatre stock\u00e9e dans les liaisons chimiques entre les atomes qui composent les mol\u00e9cules.\u00a0Ce stockage d&#8217;\u00e9nergie au niveau atomique comprend l&#8217;\u00e9nergie associ\u00e9e aux \u00e9tats orbitaux des \u00e9lectrons, au spin nucl\u00e9aire et aux forces de liaison dans le noyau.<\/span><\/p>\n<p><strong><span>L&#8217;enthalpie<\/span><\/strong><span>\u00a0est repr\u00e9sent\u00e9e par le symbole\u00a0<\/span><strong><span>H<\/span><\/strong><span>\u00a0, et le changement d&#8217;enthalpie (delta H) dans un processus est\u00a0<\/span><strong><span>H\u00a0<\/span><sub><span>2<\/span><\/sub><span>\u00a0&#8211; H\u00a0<\/span><sub><span>1<\/span><\/sub><\/strong><span>\u00a0.<\/span><\/p>\n<p><span>Il existe des expressions en termes de variables plus famili\u00e8res telles que la\u00a0<\/span><a title=\"Qu'est-ce que la temp\u00e9rature - Physique\" href=\"https:\/\/www.thermal-engineering.org\/fr\/quest-ce-que-la-temperature-physique-definition\/\"><span>temp\u00e9rature<\/span><\/a><span>\u00a0et la\u00a0<\/span><a title=\"Qu'est-ce que la pression - Physique\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/thermodynamic-properties\/what-is-pressure-physics\/\"><span>pression<\/span><\/a><span>\u00a0:<\/span><\/p>\n<p><em><strong><span>dH = C\u00a0<\/span><sub><span>p<\/span><\/sub><span>\u00a0dT + V (1-\u03b1T) dp<\/span><\/strong><\/em><\/p>\n<p><span>O\u00f9\u00a0<\/span><strong><span>C\u00a0<\/span><sub><span>p<\/span><\/sub><\/strong><span>\u00a0est la\u00a0<\/span><strong><span>capacit\u00e9 thermique \u00e0 pression constante<\/span><\/strong><span>\u00a0et\u00a0<\/span><strong><em><span>\u03b1<\/span><\/em><\/strong><span>\u00a0est le coefficient de dilatation thermique (cubique).\u00a0Pour un gaz parfait \u03b1T = 1 et donc:<\/span><\/p>\n<p><strong><em><span>dH = C\u00a0<\/span><sub><span>p<\/span><\/sub><span>\u00a0dT<\/span><\/em><\/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\">\n<div class=\"su-spacer\"><\/div>\n<h2><span>Exemple: Piston sans friction &#8211; Chaleur &#8211; Enthalpie<\/span><\/h2>\n<figure id=\"attachment_16678\" class=\"wp-caption alignright\" aria-describedby=\"caption-attachment-16678\"><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Enthalpy-example-min.png\"><img loading=\"lazy\" class=\"size-medium wp-image-16678 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Enthalpy-example-min-224x300.png\" alt=\"Enthalpie - Exemple - Un piston sans friction\" width=\"224\" height=\"300\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Enthalpy-example-min-224x300.png\" \/><\/a><figcaption id=\"caption-attachment-16678\" class=\"wp-caption-text\"><span>Calculez la temp\u00e9rature finale, si 3000 kJ de chaleur sont ajout\u00e9s.<\/span><\/figcaption><\/figure>\n<p><span>Un piston sans\u00a0frottement est utilis\u00e9 pour fournir une pression constante de\u00a0<\/span><strong><span>500 kPa<\/span><\/strong><span>\u00a0en une vapeur contenant de cylindre (\u00a0<\/span><a title=\"Vapeur surchauff\u00e9e\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/materials-nuclear-engineering\/properties-steam-what-is-steam\/superheated-steam\/\"><span>vapeur surchauff\u00e9e<\/span><\/a><span>\u00a0) d&#8217;un volume de\u00a0<\/span><strong><span>2 m\u00a0<\/span><sup><span>3<\/span><\/sup><\/strong><span>\u00a0\u00a0\u00e0\u00a0<\/span><strong><span>500 K<\/span><\/strong><span>\u00a0.\u00a0Calculez la temp\u00e9rature finale, si\u00a0<\/span><strong><span>3000 kJ<\/span><\/strong><span>\u00a0de\u00a0<\/span><strong><span>chaleur<\/span><\/strong><span>\u00a0sont ajout\u00e9s.<\/span><\/p>\n<p><strong><span>Solution:<\/span><\/strong><\/p>\n<p><span>En utilisant\u00a0<\/span><a title=\"Tables \u00e0 vapeur - Propri\u00e9t\u00e9s sp\u00e9cifiques de l'eau et de la vapeur\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/steam-tables\/\"><span>des tables \u00e0 vapeur,<\/span><\/a><span>\u00a0nous savons que l&#8217;\u00a0<\/span><strong><span>enthalpie sp\u00e9cifique<\/span><\/strong><span>\u00a0de cette vapeur (500 kPa; 500 K) est d&#8217;environ\u00a0<\/span><strong><span>2912 kJ \/ kg<\/span><\/strong><span>\u00a0.\u00a0\u00c9tant donn\u00e9 qu&#8217;\u00e0 cette condition, la vapeur a une densit\u00e9 de 2,2 kg \/ m\u00a0<\/span><sup><span>3<\/span><\/sup><span>\u00a0, alors nous savons qu&#8217;il y a environ\u00a0<\/span><strong><span>4,4 kg de vapeur<\/span><\/strong><span>\u00a0dans le piston \u00e0 l&#8217;enthalpie de 2912 kJ \/ kg x 4,4 kg =\u00a0<\/span><strong><span>12812 kJ<\/span><\/strong><span>\u00a0.<\/span><\/p>\n<p><span>Lorsque nous utilisons simplement\u00a0<\/span><strong><span>Q = H\u00a0<\/span><sub><span>2<\/span><\/sub><span>\u00a0&#8211; H\u00a0<\/span><sub><span>1<\/span><\/sub><\/strong><span>\u00a0, l&#8217;enthalpie de vapeur r\u00e9sultante sera alors:<\/span><\/p>\n<p><span>H\u00a0<\/span><sub><span>2<\/span><\/sub><span>\u00a0= H\u00a0<\/span><sub><span>1<\/span><\/sub><span>\u00a0+ Q =\u00a0<\/span><strong><span>15812 kJ<\/span><\/strong><\/p>\n<p><span>A partir\u00a0<\/span><strong><span>des tables \u00e0 vapeur<\/span><\/strong><span>\u00a0, une telle vapeur surchauff\u00e9e (15812 \/ 4,4 = 3593 kJ \/ kg) aura une temp\u00e9rature de\u00a0<\/span><strong><span>828 K (555 \u00b0 C)<\/span><\/strong><span>\u00a0.\u00a0Comme \u00e0 cette enthalpie, la vapeur a une densit\u00e9 de 1,31 kg \/ m\u00a0<\/span><sup><span>3<\/span><\/sup><span>\u00a0, il est \u00e9vident qu&#8217;elle a augment\u00e9 d&#8217;environ 2,2 \/ 1,31 = 1,67 (+ 67%).\u00a0Par cons\u00e9quent, le volume r\u00e9sultant est de 2 m\u00a0<\/span><sup><span>3<\/span><\/sup><span>\u00a0x 1,67 = 3,34 m\u00a0<\/span><sup><span>3<\/span><\/sup><span>\u00a0et \u2206V = 3,34 m\u00a0<\/span><sup><span>3<\/span><\/sup><span>\u00a0&#8211; 2 m\u00a0<\/span><sup><span>3<\/span><\/sup><span>\u00a0= 1,34 m\u00a0<\/span><sup><span>3<\/span><\/sup><span>\u00a0.<\/span><\/p>\n<p><span>La\u00a0partie\u00a0<\/span><strong><span>p\u2206V<\/span><\/strong><span>\u00a0de l&#8217;enthalpie, c&#8217;est-\u00e0-dire le travail effectu\u00e9 est:<\/span><\/p>\n<p><strong><span>W = p\u2206V = 500 000 Pa x 1,34 m\u00a0<\/span><sup><span>3<\/span><\/sup><span>\u00a0= 670 kJ<\/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\">\n<div class=\"su-spacer\"><\/div>\n<h2><span>Enthalpie en unit\u00e9s intensives &#8211; Enthalpie sp\u00e9cifique<\/span><\/h2>\n<p><span>L&#8217;\u00a0<\/span><strong><span>enthalpie<\/span><\/strong><span>\u00a0peut \u00eatre transform\u00e9e en une\u00a0variable\u00a0<\/span><strong><span>intensive<\/span><\/strong><span>\u00a0ou\u00a0<\/span><strong><span>sp\u00e9cifique<\/span><\/strong><span>\u00a0, en la divisant par la\u00a0<\/span><a title=\"Qu'est-ce que la masse\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/thermodynamic-properties\/what-is-mass-and-weight\/what-is-mass\/\"><span>masse<\/span><\/a><span>\u00a0.\u00a0<\/span><strong><span>Les ing\u00e9nieurs utilisent l&#8217;\u00a0<\/span><\/strong><strong><span>enthalpie sp\u00e9cifique<\/span><\/strong><span>\u00a0dans l&#8217;analyse thermodynamique plus que l&#8217;enthalpie elle-m\u00eame.\u00a0L&#8217;enthalpie sp\u00e9cifique (h) d&#8217;une substance est son enthalpie par unit\u00e9 de masse.\u00a0Elle est \u00e9gale \u00e0 l&#8217;enthalpie totale (H) divis\u00e9e par la masse totale (m).<\/span><\/p>\n<p><strong><em><span>h = H \/ m<\/span><\/em><\/strong><\/p>\n<p><span>o\u00f9:<\/span><\/p>\n<p><span>h = enthalpie sp\u00e9cifique (J \/ kg)<\/span><\/p>\n<p><span>H = enthalpie (J)<\/span><\/p>\n<p><span>m = masse (kg)<\/span><\/p>\n<p><span>Notez que l&#8217;enthalpie est la quantit\u00e9 thermodynamique \u00e9quivalente au\u00a0<\/span><strong><span>contenu calorifique total<\/span><\/strong><span>\u00a0d&#8217;un syst\u00e8me.\u00a0L&#8217;enthalpie sp\u00e9cifique est \u00e9gale \u00e0 l&#8217;\u00a0<\/span><a title=\"\u00c9nergie interne sp\u00e9cifique\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/what-is-energy-physics\/internal-energy-thermal-energy\/specific-internal-energy\/\"><span>\u00e9nergie interne sp\u00e9cifique<\/span><\/a><span>\u00a0du syst\u00e8me plus le produit de la\u00a0<\/span><a title=\"Qu'est-ce que la pression - Physique\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/thermodynamic-properties\/what-is-pressure-physics\/\"><span>pression<\/span><\/a><span>\u00a0et du\u00a0<\/span><a title=\"Quel est le volume sp\u00e9cifique\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/thermodynamic-properties\/what-is-specific-volume\/\"><span>volume sp\u00e9cifique<\/span><\/a><span>\u00a0.<\/span><\/p>\n<p><em><strong><span>h = u + pv<\/span><\/strong><\/em><\/p>\n<p><span>En g\u00e9n\u00e9ral, l&#8217;enthalpie est une\u00a0<\/span><strong><span>propri\u00e9t\u00e9 d&#8217;une substance<\/span><\/strong><span>\u00a0, comme la pression, la temp\u00e9rature et le volume, mais elle ne peut pas \u00eatre mesur\u00e9e directement.\u00a0Normalement, l&#8217;enthalpie d&#8217;une substance est donn\u00e9e par rapport \u00e0 une valeur de r\u00e9f\u00e9rence.\u00a0Par exemple, l&#8217;enthalpie sp\u00e9cifique de l&#8217;eau ou de la vapeur est donn\u00e9e en utilisant la r\u00e9f\u00e9rence selon laquelle l&#8217;enthalpie sp\u00e9cifique de l&#8217;eau est\u00a0<\/span><strong><span>nulle \u00e0 0,01 \u00b0 C<\/span><\/strong><span>\u00a0et\u00a0<\/span><a title=\"Pression atmosph\u00e9rique\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/thermodynamics\/thermodynamic-properties\/what-is-pressure-physics\/atmospheric-pressure\/\"><strong><span>\u00e0 la pression atmosph\u00e9rique normale<\/span><\/strong><\/a><span>\u00a0, o\u00f9\u00a0<\/span><strong><span>h\u00a0<\/span><sub><span>L<\/span><\/sub><span>\u00a0= 0,00 kJ \/ kg<\/span><\/strong><span>\u00a0.\u00a0Le fait que la valeur absolue de l&#8217;enthalpie sp\u00e9cifique ne soit pas connue n&#8217;est cependant pas un probl\u00e8me, car c&#8217;est le\u00a0<\/span><strong><span>changement d&#8217;enthalpie sp\u00e9cifique (\u2206h)<\/span><\/strong><span>\u00a0et non la valeur absolue qui est important dans les probl\u00e8mes pratiques.<\/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 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>Changements d&#8217;enthalpie dans les r\u00e9actions chimiques<\/span><\/h2>\n<figure id=\"attachment_15727\" class=\"wp-caption aligncenter\" aria-describedby=\"caption-attachment-15727\"><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Combustion-of-Hydrogen-schematic.png\"><img loading=\"lazy\" class=\"size-medium wp-image-15727 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Combustion-of-Hydrogen-schematic-300x248.png\" alt=\"Combustion d'hydrog\u00e8ne\" width=\"300\" height=\"248\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Combustion-of-Hydrogen-schematic-300x248.png\" \/><\/a><figcaption id=\"caption-attachment-15727\" class=\"wp-caption-text\"><span>Dans une flamme d&#8217;hydrog\u00e8ne pur, br\u00fblant dans l&#8217;air, l&#8217;hydrog\u00e8ne (H2) r\u00e9agit avec l&#8217;oxyg\u00e8ne (O2) pour former de l&#8217;eau (H2O) et lib\u00e8re de l&#8217;\u00e9nergie.<\/span><\/figcaption><\/figure>\n<p><span>Consid\u00e9rez la\u00a0<\/span><strong><span>combustion de l&#8217;hydrog\u00e8ne<\/span><\/strong><span>\u00a0dans l&#8217;air.\u00a0Dans une flamme d&#8217;hydrog\u00e8ne gazeux pur, br\u00fblant dans l&#8217;air, l&#8217;\u00a0<\/span><strong><span>hydrog\u00e8ne (H\u00a0<\/span><sub><span>2<\/span><\/sub><span>\u00a0)<\/span><\/strong><span>\u00a0r\u00e9agit avec l&#8217;\u00a0\u00a0<\/span><strong><span>oxyg\u00e8ne (O\u00a0<\/span><sub><span>2<\/span><\/sub><span>\u00a0)<\/span><\/strong><span>\u00a0pour former de l&#8217;\u00a0<\/span><strong><span>eau (H\u00a0<\/span><sub><span>2<\/span><\/sub><span>\u00a0O)<\/span><\/strong><span>\u00a0et\u00a0<\/span><strong><span>lib\u00e8re de l&#8217;\u00e9nergie<\/span><\/strong><span>\u00a0.<\/span><\/p>\n<p><span>\u00c9nerg\u00e9tiquement, le processus peut \u00eatre consid\u00e9r\u00e9 comme n\u00e9cessitant de l&#8217;\u00e9nergie pour dissocier le\u00a0<\/span><strong><span>H\u00a0<\/span><sub><span>2<\/span><\/sub>\u00a0<\/strong><span>\u00a0et l&#8217;\u00a0<\/span><strong><span>O\u00a0<\/span><sub><span>2<\/span><\/sub><\/strong><span>\u00a0, mais la liaison du H\u00a0<\/span><sub><span>2<\/span><\/sub><span>\u00a0O ram\u00e8ne le syst\u00e8me \u00e0 un \u00e9tat li\u00e9 avec\u00a0<\/span><strong><span>un potentiel n\u00e9gatif<\/span><\/strong><span>\u00a0.\u00a0Il est en fait\u00a0<\/span><strong><span>plus n\u00e9gatif<\/span><\/strong><span>\u00a0que les \u00e9tats li\u00e9s des r\u00e9actifs, et la formation des deux mol\u00e9cules d&#8217;eau est donc une\u00a0<\/span><strong><span>r\u00e9action exothermique<\/span><\/strong><span>\u00a0, qui lib\u00e8re 5,7 eV d&#8217;\u00e9nergie.\u00a0En termes d&#8217;enthalpie, l&#8217;enthalpie de combustion est de -286 kJ \/ mol:<\/span><\/p>\n<p><strong><span>2H\u00a0<\/span><sub><span>2<\/span><\/sub><span>\u00a0(g) + O\u00a0<\/span><sub><span>2<\/span><\/sub><span>\u00a0(g) \u2192 2H\u00a0<\/span><sub><span>2<\/span><\/sub><span>\u00a0O (g)<\/span><\/strong><\/p>\n<p><span>En termes d&#8217;enthalpie, l&#8217;enthalpie de combustion est de -286 kJ \/ mol (\u00e9nergie par mol d&#8217;hydrog\u00e8ne mol\u00e9culaire):<\/span><\/p>\n<p><strong><span>2H\u00a0<\/span><sub><span>2<\/span><\/sub><span>\u00a0(g) + O\u00a0<\/span><sub><span>2<\/span><\/sub><span>\u00a0(g) \u2192 2H\u00a0<\/span><sub><span>2<\/span><\/sub><span>\u00a0O (l) +572 kJ<\/span><\/strong><\/p>\n<p><span>L&#8217;\u00e9quilibre \u00e9nerg\u00e9tique avant et apr\u00e8s la r\u00e9action peut \u00eatre illustr\u00e9 sch\u00e9matiquement par l&#8217;\u00e9tat dans lequel tous les atomes sont libres pris comme r\u00e9f\u00e9rence pour l&#8217;\u00e9nergie.<\/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>Enthalpie de vaporisation<\/span><\/h2>\n<figure id=\"attachment_16677\" class=\"wp-caption alignright\" aria-describedby=\"caption-attachment-16677\"><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Specific-Enthalpy-Water-and-Steam-min.png\"><img loading=\"lazy\" class=\"size-medium wp-image-16677 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Specific-Enthalpy-Water-and-Steam-min-242x300.png\" alt=\"Chaleur latente de vaporisation - eau \u00e0 0,1 MPa, 3 MPa, 16 MPa\" width=\"242\" height=\"300\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Specific-Enthalpy-Water-and-Steam-min-242x300.png\" \/><\/a><figcaption id=\"caption-attachment-16677\" class=\"wp-caption-text\"><span>La chaleur de vaporisation diminue avec l&#8217;augmentation de la pression, tandis que le point d&#8217;\u00e9bullition augmente.\u00a0Elle dispara\u00eet compl\u00e8tement \u00e0 un certain point appel\u00e9 le point critique.<\/span><\/figcaption><\/figure>\n<p><span>En g\u00e9n\u00e9ral, lorsqu&#8217;un mat\u00e9riau\u00a0<\/span><strong><span>change de phase<\/span><\/strong><span>\u00a0du solide au liquide, ou du liquide au gaz, une certaine quantit\u00e9 d&#8217;\u00e9nergie est impliqu\u00e9e dans ce changement de phase.\u00a0En cas de changement de phase liquide en gaz, cette quantit\u00e9 d&#8217;\u00e9nergie est connue sous le nom d&#8217;\u00a0<\/span><strong><span>enthalpie de vaporisation<\/span><\/strong><span>\u00a0, (symbole \u2206H\u00a0<\/span><sub><span>vap<\/span><\/sub><span>\u00a0; unit\u00e9: J) \u00e9galement connue sous le nom de\u00a0<\/span><strong><span>chaleur (latente) de vaporisation<\/span><\/strong><span>\u00a0ou chaleur d&#8217;\u00e9vaporation.\u00a0La chaleur latente est la quantit\u00e9 de chaleur ajout\u00e9e ou retir\u00e9e d&#8217;une substance pour produire un changement de phase.\u00a0Cette \u00e9nergie d\u00e9compose les forces d&#8217;attraction intermol\u00e9culaires, et doit \u00e9galement fournir l&#8217;\u00e9nergie n\u00e9cessaire \u00e0 l&#8217;expansion du gaz (le\u00a0<\/span><strong><span>travail p\u0394V<\/span><\/strong><span>).\u00a0Lorsque de la chaleur latente est ajout\u00e9e, aucun changement de temp\u00e9rature ne se produit.\u00a0L&#8217;enthalpie de vaporisation est fonction de la pression \u00e0 laquelle cette transformation a lieu.<\/span><\/p>\n<p><span>Chaleur latente de vaporisation &#8211; eau \u00e0 0,1 MPa (pression atmosph\u00e9rique)<\/span><\/p>\n<p><strong><span>h\u00a0<\/span><sub><span>lg<\/span><\/sub><span>\u00a0= 2257 kJ \/ kg<\/span><\/strong><\/p>\n<p><span>Chaleur latente de vaporisation &#8211; eau \u00e0 3 MPa (pression \u00e0 l&#8217;int\u00e9rieur d&#8217;un g\u00e9n\u00e9rateur de vapeur)<\/span><\/p>\n<p><strong><span>h\u00a0<\/span><sub><span>lg<\/span><\/sub><span>\u00a0= 1795 kJ \/ kg<\/span><\/strong><\/p>\n<p><span>Chaleur latente de vaporisation &#8211; eau \u00e0 16 MPa (pression \u00e0 l&#8217;int\u00e9rieur d&#8217;un\u00a0<\/span><a title=\"Pressuriseur\" href=\"https:\/\/www.nuclear-power.com\/pressurizer\/\"><span>pressuriseur<\/span><\/a><span>\u00a0)<\/span><\/p>\n<p><strong><span>h\u00a0<\/span><sub><span>lg<\/span><\/sub><span>\u00a0= 931 kJ \/ kg<\/span><\/strong><\/p>\n<p><span>La\u00a0<\/span><strong><span>chaleur de vaporisation<\/span><\/strong><span>\u00a0diminue avec l&#8217;augmentation de la pression, tandis que le\u00a0<\/span><a title=\"Saturation - point d'\u00e9bullition\" href=\"https:\/\/www.thermal-engineering.org\/fr\/quest-ce-que-la-saturation-point-debullition-definition\/\"><span>point d&#8217;\u00e9bullition<\/span><\/a><span>\u00a0augmente.\u00a0Elle dispara\u00eet compl\u00e8tement \u00e0 un certain point appel\u00e9 le\u00a0<\/span><a title=\"Point critique de l'eau\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/materials-nuclear-engineering\/properties-of-water\/critical-point-of-water\/\"><span>point critique<\/span><\/a><span>\u00a0.\u00a0Au-dessus du point critique, les phases liquide et vapeur sont indiscernables et la substance est appel\u00e9e\u00a0<\/span><a title=\"Fluide supercritique - Eau supercritique\" href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/materials-nuclear-engineering\/properties-steam-what-is-steam\/supercritical-fluid-supercritical-water\/\"><span>fluide supercritique<\/span><\/a><span>\u00a0.<\/span><\/p>\n<p><span>La chaleur de vaporisation est la chaleur n\u00e9cessaire pour vaporiser compl\u00e8tement une unit\u00e9 de\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>liquide satur\u00e9<\/span><\/a><span>\u00a0(ou condenser une unit\u00e9 de masse de vapeur satur\u00e9e) et elle est \u00e9gale \u00e0\u00a0<\/span><strong><span>h\u00a0<\/span><sub><span>lg<\/span><\/sub><span>\u00a0= h\u00a0<\/span><sub><span>g<\/span><\/sub><span>\u00a0&#8211; h\u00a0<\/span><sub><span>l<\/span><\/sub><\/strong><span>\u00a0.<\/span><\/p>\n<p><span>La chaleur n\u00e9cessaire pour faire fondre (ou geler) une masse unitaire \u00e0 la substance \u00e0 pression constante est la chaleur de fusion et est \u00e9gale \u00e0\u00a0<\/span><strong><span>h\u00a0<\/span><sub><span>sl<\/span><\/sub><span>\u00a0= h\u00a0<\/span><sub><span>l<\/span><\/sub><span>\u00a0&#8211; h\u00a0<\/span><sub><span>s<\/span><\/sub><\/strong><span>\u00a0, o\u00f9 h\u00a0<\/span><sub><span>s<\/span><\/sub><span>\u00a0est l&#8217;enthalpie du solide satur\u00e9 et h\u00a0<\/span><sub><span>l<\/span><\/sub><span>\u00a0est l&#8217;enthalpie du liquide satur\u00e9.<\/span><\/p>\n<figure id=\"attachment_16676\" class=\"wp-caption aligncenter\" aria-describedby=\"caption-attachment-16676\"><a href=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Phease-Changes-Heat-of-Vaporization-Water-min.png\"><img loading=\"lazy\" class=\"size-large wp-image-16676 lazy-loaded\" src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Phease-Changes-Heat-of-Vaporization-Water-min-1024x454.png\" alt=\"Changements de phase - enthalpie de vaporisation\" width=\"669\" height=\"297\" data-lazy-type=\"image\" data-src=\"https:\/\/thermal-engineering.org\/wp-content\/uploads\/2019\/05\/Phease-Changes-Heat-of-Vaporization-Water-min-1024x454.png\" \/><\/a><figcaption id=\"caption-attachment-16676\" class=\"wp-caption-text\"><span>Chaleur latente de vaporisation &#8211; eau \u00e0 0,1 MPa.\u00a0Partie dominante de la chaleur absorb\u00e9e.<\/span><\/figcaption><\/figure>\n<\/div>\n<\/div>\n<\/div>\n<div><\/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>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>L&#8217;enthalpie est repr\u00e9sent\u00e9e par le symbole H et le changement d&#8217;enthalpie dans un processus (delta h) est H2 &#8211; H1. Delta h est calcul\u00e9 ici pour divers exemples. G\u00e9nie thermique Enthalpie en unit\u00e9s extensives Propri\u00e9t\u00e9s extensives et intensives du milieu dans le pressuriseur. H = U + pV L&#8217;enthalpie\u00a0\u00a0est une quantit\u00e9 importante, elle d\u00e9pend de &#8230; <a title=\"Qu&#8217;est-ce que le changement d&#8217;enthalpie &#8211; delta h &#8211; D\u00e9finition\" class=\"read-more\" href=\"https:\/\/www.thermal-engineering.org\/fr\/quest-ce-que-le-changement-denthalpie-delta-h-definition\/\" aria-label=\"En savoir plus sur Qu&#8217;est-ce que le changement d&#8217;enthalpie &#8211; delta h &#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 le changement d&#039;enthalpie - delta h - D\u00e9finition<\/title>\n<meta name=\"description\" content=\"L&#039;enthalpie est repr\u00e9sent\u00e9e par le symbole H et le changement d&#039;enthalpie dans un processus (delta h) est H2 - H1. 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