مطالعۀ آزمایشگاهی عملکرد رادیومتر کروکس

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشکدۀ مهندسی، دانشگاه فردوسی مشهد.

2 دانشکدۀ مهندسی، دانشگاه فردوسی مشهد

چکیده

  این مقاله به بررسی و مطالعۀ آزمایشگاهی عملکرد پره­های پمپ­های رادیومتریک می­پردازد. یک نمونه از این پمپ­های رادیومتریک، رادیومتر کروکس است که شامل محفظه­ای شیشه­ای شکل است که درون آن خلأ است. داخل این محفظۀ شیشه­ای پره­هایی برروی یک سوزن قرار دارند. یک طرف از این پره­ها به‌صورت براق و سمت دیگر به‌صورت تیره هستند. در این پژوهش برای اولین‌بار مکانیزمی برای تعیین دما به‌صورت مستقیم از روی پره­های سرد و گرم درنظر گرفته شده‌است. مشاهده می­شود که نیروی اندازه­گیری‌شده با اختلاف دمای میان دو سر پره متناسب است و این تناسب به‌صورت خطی است؛ اما این ارتباط تنها تا بیشینۀ اختلاف دما صادق است. سرعت زاویه­ای پره­ها نیز توسط یک تاکومتر لیزری اندازه‌گیری شده‌است. برای محاسبۀ نیرو از سرعت اندازه‌گیری‌شده استفاده شده‌است. این مطالعه در سه بخش صورت گرفته‌است. بخش اول (آزمایشگاهی)  ساخت یک نمونه رادیومتر کروکس است. بخش دوم شامل مطالعه و بازخوانی تحلیل جریان رادیومتریک و تئوری­های مربوط به نیروی رادیومتریک می­باشد و در بخش سوم مقایسۀ نتایج آزمایشگاهی و تئوری­های موجود در قسمت آزمایشگاهی انجام شده‌است. این آزمایش در چهار فشار کاری 30 pa، 6 pa، 0.6pa، و 0.06 pa انجام شده‌است. هر فشار به‌ترتیب نمایندۀ اعداد نودسن 0.05، 0.1، 1 و 10 و یک رژیم جریان است. بیشینۀ نیرو­ها در فشار 6 pa و بیشینۀ سرعت در فشار 0.6 pa مشاهده شد که با داده­های تئوری تطابق خوبی دارد.

کلیدواژه‌ها


عنوان مقاله [English]

An Experimental Study of Crookes Radiometer

نویسندگان [English]

  • Ehsan Roohi 1
  • Reza Arabpour 2
1 Ferdowsi University of Mashhad, Mashhad, Iran.
2 Ferdowsi University of Mashhad, Mashhad, Iran.
چکیده [English]

This paper investigates and studies the vanes of radiometric pumps. An example of a radiometric pump is the Crooks radiometer, which consists of an airtight glass bulb containing a partial vacuum, with a set of vanes mounted on a spindle inside. One side of the vane is white, and the other side is black. In this study, for the first time, a mechanism to measure the temperature directly from hot and cold blades is considered. It is observed that the measured force is proportional to the temperature difference between the two blade ends, and this proportionality is linear. But this relationship is only valid up to the maximum temperature difference. The angular velocity of the blades was also measured by a laser tachometer. The measured velocity is used to calculate the force. This study has been performed in three parts. Part 1 (Laboratory): Designing and constructing a radiometer with different types of vanes. Part II includes the study and review of radiometric flow analysis and theories related to radiometric force. In the third part, a comparison of laboratory results and theories is reported. The tests were performed at four working pressures of 30 pa, 6 pa, 0.6pa, and 0.06 pa. These pressures represent the Knudsen numbers of 0.05, 0.1, 1 and 10 and different flow regimes, respectively. Maximum forces were observed at a pressure of 6 pa and maximum velocity at 0.6 pa, which is in a cooperative agreement with the theoretical data.

کلیدواژه‌ها [English]

  • Rarified flow
  • Radiometer pumps
  • Radiometric force
  • Crookes radiometer
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