Name: gas cooling and heating in throttling
Uploaded: 2025-05-22T09:05:59.000Z
Duration: 1 min 21 s
Channel: JoVE

K12 Standards

Florida Department of Education

High School

Physical Science

SC.912.P.10

SC.912.P.10.2

Joule-Thomson Effect

يوضح تأثير جول طومسون أنه في نظام ثابت الحرارة ، إذا أجبر غاز يتم الاحتفاظ به عند ضغط عال على المرور عبر سدادة مسامية إلى منطقة ضغط منخفض ، فإنه يتمدد ويحتل حجما أكبر ، مما يغير درجة حرارته ، ونتيجة لذلك ، يصبح طاقته الداخلية.
في هذه العملية الثابتة، يجب أن يساوي التغير في الطاقة الداخلية للغاز الشغل المنجز على الغاز مطروحا منه الشغل الذي يقوم به الغاز. تظهر إعادة ترتيب المصطلحات أن المحتوى الحراري محفوظ.
يعرف التغير في درجة الحرارة مع الضغط عند المحتوى الحراري الثابت بأنه معامل جول طومسون. باستخدام نظرية المعاملة بالمثل واستبدال علاقة السعة الحرارية ، يتم التعبير عن معامل جول طومسون من حيث المشتق الجزئي للمحتوى الحراري بالضغط.
التعبير عن المشتق الجزئي من حيث الانتروبيا واستخدام علاقة ماكسويل يعطي معامل جول طومسون كدالة لدرجة الحرارة.
تشير قيمة المعامل الموجب إلى التبريد ، بينما تشير القيمة السالبة إلى تسخين الغاز أثناء التمدد.
بالنسبة للغاز المثالي ، فإن معامل جول طومسون يساوي صفرا حيث تظل درجة حرارته كما هي عند المرور إلى منطقة الضغط المنخفض.

<ol>
	<li>Blundell ، S.J. و Blundell ، K.M. (2010). مفاهيم في الفيزياء الحرارية. الطبعة الثانية. نيويورك ، الولايات المتحدة: مطبعة جامعة أكسفورد.</li>
	<li>ريكس ، أ (2017). الفيزياء الحرارية الفنلندي. الطبعة الثالثة. بوكا راتون ، فلوريدا: مطبعة CRC. ص. 212.</li>
</ol>

تأثير جول طومسون

<div style="direction:rtl">يصف تأثير جول طومسون، المعروف أيضًا باسم تأثير جول كلفن، التغير في درجة حرارة السائل عندما يتم دفعه عبر صمام أو سدادة مسامية مع إبقائه في بيئة معزولة حرارياً. تسمى هذه التجربة بعملية الاختناق. وهذا تأثير مهم يستخدم على نطاق واسع في التبريد وتسييل الغازات. تدفع هذه التجربة الغاز عالي الضغط عبر صمام خانق أو سدادة مسامية إلى منطقة الضغط المنخفض. يتمدد الغاز أثناء مروره بمنطقة الضغط المنخفض ويحتل حجمًا أكبر من الحجم الأولي. يتم العمل على الغاز عندما يتم دفع الغاز عبر صمام الخانق. ومع ذلك، عندما يتوسع، يتم العمل بواسطة الغاز الموجود على المناطق المحيطة به. تختلف درجة حرارة الغاز في هذه العملية؛ ومن ثم يكتسب طاقة داخلية جديدة. يجب أن يكون التغير في الطاقة الداخلية للغاز مساويًا للشغل المبذول على الغاز مطروحًا منه الشغل الذي يبذله الغاز. لقد وجد أن الإنثالبي محفوظ (isenthalpic) في عملية التدفق هذه. يتم الحصول على التغير في درجة حرارة الغاز عند انخفاض الضغط عند المحتوى الحراري الثابت بواسطة معامل جول-طومسون: <img alt="Equation1" src="/files/ftp_upload/14174/14174_Equation_1.png" style="text-align: center; height: 42px;"> بما أن درجة حرارة الغاز تختلف، فإن معامل جول طومسون يمكن أن يأخذ أي من الإشارة، اعتمادًا على ما إذا كان الغاز يسخن أو يبرد. يوضح منحنى الانعكاس في المستوى T-p تسخين وتبريد الغاز أثناء عملية الاختناق. <img alt="الشكل1" src="/files/ftp_upload/14174/14174_Figer_1.png"> يفصل منحنى الانعكاس منطقة التسخين عن منطقة التبريد. الحد الأقصى لمختلف isenthalps يقع على منحنى الانعكاس. لاحظ أن isenthalp هو موضع نقاط النهاية لعمليات الاختناق المختلفة، بدءًا من نفس الحالة الأولية. اعتمادًا على مكان اختيار النقاط الأولية والنهائية، يمكن إنتاج تأثيرات التسخين والتبريد أثناء عملية الاختناق. معامل جول طومسون هو صفر للغاز المثالي، مما يشير إلى عدم وجود تغير في درجة الحرارة عندما يخضع الغاز المثالي لعملية الاختناق. ويكون المعامل سالبًا بالنسبة للغازات الحقيقية عند درجات الحرارة المرتفعة للغاية والمنخفضة للغاية.</div>

يصف تأثير جول طومسون ، المعروف أيضا باسم تأثير جول كلفن ، تغير درجة حرارة السائل عندما يتم دفعه من خلال صمام أو مسامية ...

Education

JoVE Core

Physics

الفيزياء

Unit 1

الوحدة الأولى

The First Law of Thermodynamics

القانون الأول للديناميكا الحرارية

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

gas cooling and heating in throttling

Gas cooling and heating in throttling is explained by the Joule-Thomson effect, also called the Joule-Kelvin effect. It describes how a fluid changes temperature when it passes through a valve or porous plug in a thermally insulated system. This type of flow is called a throttling process.

In the experiment, a high-pressure gas is forced through a throttle valve or porous plug into a lower-pressure region. The gas expands as it moves into the larger volume. Work is done on the gas as it is pushed through the valve. After expansion, the gas also does work on the surroundings.

Because the temperature changes during the process, the gas reaches a new internal energy state. The change in internal energy equals the work done on the gas minus the work done by the gas. In this flow process, enthalpy stays constant, so the process is isenthalpic. The Joule-Thomson coefficient gives the temperature change when pressure drops at constant enthalpy.

The gas may either warm up or cool down, so the Joule-Thomson coefficient can be positive or negative. The inversion curve on a temperature-pressure diagram shows where heating changes to cooling. It separates the heating region from the cooling region, and the peaks of different isenthalps lie on this curve. An isenthalp is the set of end points for throttling processes that start from the same initial state.

Depending on the starting and ending points, throttling can produce either heating or cooling. For an ideal gas, the Joule-Thomson coefficient is zero, so no temperature change occurs during throttling. For real gases, the coefficient is negative at extremely high and extremely low temperatures. This effect is important in refrigeration and in the liquefaction of gases.

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Gas cooling and heating in throttling is explained by the Joule-Thomson effect, also called the Joule-Kelvin effect. It describes how a fluid changes temperature when it passes through a valve or porous plug in a thermally insulated system. This type of flow is called a throttling process. In the experiment, a high-pressure gas is forced through a throttle valve or porous plug into a lower-pressure region. The gas expands as it moves into the larger volume. Work is done on the gas as it is...

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Gas Cooling and Heating in Throttling

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