مدل‌سازی عددی اثر دما و فشار ورودی بر چگالش بخار و تولید آنتروپی در جداساز فشار بالا

نوع مقاله : مقاله پژوهشی

نویسندگان

گروه مهندسی مکانیک، مرکز پژوهشی شبکه‌های گاز رسانی، دانشکده مهندسی، دانشگاه شهید چمران اهواز، اهواز، ایران

چکیده

جداساز فراصوت گاز - مایع یک نازل همگرا - واگرا است که میعان و تغییر فاز در سرعت‌های بالاتر از صوت از خصوصیات عملکرد این دستگاه می‌باشد. جریان سیال، انتقال جرم و حرارت در جداسازهای فراصوت به دلیل بر هم کنش پیچیده جریان فراصوت و تغییر فاز به خوبی درک نشده است. در این پژوهش، از معادله حالت گاز ویریال و یک مدل ریاضی برای پیش‌بینی دقیق پدیده چگالش خود به خودی با استفاده از نظریه‌های هسته‌زایی و رشد قطره استفاده شده است. شعاع متوسط قطره و توزیع فشار حاصل شده از مدل عددی به خوبی با داده‌های تجربی سازگار است. نتایج نشان داد با 3/5% کاهش دمای ورودی در فشار ثابت، شعاع متوسط قطره‌های خروجی بیش از 40% افزایش یافت. همچنین، با حدود 40% افزایش فشار ورودی در دمای ثابت، بیش‌ترین کسر جرمی مایع بیش از 90% افزایش یافت. بنابراین، استفاده از دمای پایین و فشار بالا در ورودی به منظور بهبود راندمان جداسازی ضروری است. همچنین، کم‌ترین میزان نرخ تولید آنتروپی ناشی از تغییرات دما مربوط به بیش‌ترین فشار و کم‌ترین دما بوده و کم‌ترین میزان نرخ تولید آنتروپی ناشی از تغییرات فشار مربوط به کم‌ترین دما و فشار است. محاسبه عدد بیجان نشان داد که برگشت ناپذیری تحت تأثیر اثرات اصطکاک سیال در مقایسه با انتقال حرارت غالب است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Numerical Modeling of the Effect of Inlet Temperature and Pressure on Steam Condensation and Entropy Generation in High-Pressure Separator

نویسندگان [English]

  • Soroush Yousefi
  • Maziar Changizian
  • Seyed Saied Bahrainian
Department of Mechanical Engineering, Gas Networks Research Center, Faculty of Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran
چکیده [English]

The gas-liquid supersonic separator is a convergent-divergent nozzle in which condensation and phase change at speeds higher than sound are the characteristics of this device. The fluid flow, mass, and heat transfer in supersonic separators are not understood well due to the complicated interaction of the supersonic flow and phase change. In this research, the virial gas equation of state and a mathematical model have been used to accurately predict the phenomenon of spontaneous condensation using theories of nucleation and droplet growth. The droplet average radius and pressure distribution obtained from the numerical model are well consistent with the experimental data. The results showed that with a 3.5% decrease in inlet temperature at a constant pressure, the average radius of the outlet droplets increased by more than 40%. Also, with about a 40% increase in inlet pressure at a constant temperature, the maximum liquid mass fraction increased by more than 90%. Therefore, the use of low temperature and high pressure at the inlet is necessary to improve the separation efficiency.Also, the lowest entropy generation rate due to temperature changes is related to the highest pressure and the lowest temperature, and the lowest entropy generation rate due to pressure changes is related to the lowest temperature and pressure.The Bejan number calculation showed that irreversibility is affected by the effects of fluid friction compared to heat transfer.

کلیدواژه‌ها [English]

  • Supersonic separator
  • Two-phase flow
  • Spontaneous condensation
  • Entropy generation
  • The Bejan number
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