Iran is connected to free ocean and other countries through Persian Gulf, Oman Sea and Caspian Sea. Thus, it is necessary to increase practical and scientific knowledge of seas rapidly.
Knowing heat distribution in Persian Gulf helps one to forecast weather condition, More
Iran is connected to free ocean and other countries through Persian Gulf, Oman Sea and Caspian Sea. Thus, it is necessary to increase practical and scientific knowledge of seas rapidly.
Knowing heat distribution in Persian Gulf helps one to forecast weather condition, predict the habitat of aquatic animals and plants, and provide other accurate information about sea.
Generally the total in flow and outflow heat flux of the oceans should be zero; otherwise this oceans will freeze or will be very hot. The heat balance in Persian Gulf is examined in the article. Considering the point that the amount of rain and the inflow water to Persian Gulf is about 90cm/a and evaporation is 213cm/a, therefore, the amount of evaporation is 20-25cm/a more than rain in Persian Gulf annually. Since the Persian Gulf volume of inflow and outflow is 0.186*106 and 0.169*106 m3 /s, the net transfer of heat to this Gulf is 25w/m2.
The aim of this article is to explain this extra heat entering Persian Gulf by heat flux terms. The annual mean values of upward heat transfer due to solar radiation, sensible heat, latent heat and infrared radiation fluxes are 245 , -4 , 179 and 92 w/m3 respectively .The result is upward flux of about 22 w/m2 at the sea surface of this Gulf. This is in fair agreement with the extra heat transport in the Persian Gulf.
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Due to the growing need of industries to improve heat transfer methods, the nucleate boiling region is of special interest to researchers because fluid boiling makes it possible to achieve higher heat fluxes than processes that are based only on non-boiling convection h More
Due to the growing need of industries to improve heat transfer methods, the nucleate boiling region is of special interest to researchers because fluid boiling makes it possible to achieve higher heat fluxes than processes that are based only on non-boiling convection heat transfer. In addition, the change of working fluid in boiling heat transfer systems from pure fluid to nanofluid improves the heat transfer characteristics and thus allows the transfer of higher heat flux at lower temperatures. At the critical heat flux point, where the heat flux is maximum, it is important to secure the boiling surface and protect it from overheating. The purpose of this study is to numerically simulate the pool boiling of a water-based hybrid nanofluid containing 30% multi-walled carbon nanotubes and 70% titanium oxide with a volumetric concentration of 0.5% on a polished copper circular surface and to investigate the heat transfer characteristics, especially the critical heat flux point. For this purpose, the boiling process of pure deionized water was first simulated by ANSYS-Fluent software and the results were compared with experimental data. According to the observed acceptable agreement, the mentioned water-based hybrid nanofluid, as boiling working fluid is numerically simulated by changing the density of nucleation sites and its heat transfer and heat flux characteristics are obtained. The results show that the critical heat flux for pure deionized water was occurred at 24.4 °C and is about 1.1 MW per square meter, while the critical heat flux for the hybrid nanofluid was occurred at 13 °C and is about 1 MW per square meter.
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در این مقاله تحلیل عددی جریان و انتقال حرارت وابسته به زمان میکرولوله محتوی نانوسیال در جریان آرام بررسی شده است. در این بررسی، انتقال حرارت جابهجایی نانوسیال و سیال پایه و تحلیل گذرا برای شار حرارتی متغیر با زمان، بهازای گام زمانی 4-10 ثانیه بررسی شده است. مشاهده شد More
در این مقاله تحلیل عددی جریان و انتقال حرارت وابسته به زمان میکرولوله محتوی نانوسیال در جریان آرام بررسی شده است. در این بررسی، انتقال حرارت جابهجایی نانوسیال و سیال پایه و تحلیل گذرا برای شار حرارتی متغیر با زمان، بهازای گام زمانی 4-10 ثانیه بررسی شده است. مشاهده شد که با افزایش کسر حجمی نانوذره، قدرت پمپاژ نانوسیال و دمای حداکثر دیواره میکرولوله بهترتیب افزایش و کاهش پیدا میکند. حداکثر دما سیال پایه (آب) 6/305 کلوین و برای نانوذره اکسید آلومینیوم AF با کسر حجمی سه درصد، دمای حداکثر 2/304 کلوین میباشد. علاوهبراین نتایج نشان داد که استفاده از نانوسیال با وجود شار حرارتی پریودیک دارای مزیت انتقال حرارتی است. از سویی دیگر نتایج نشان میدهد که پارامترهای ذکر شده، تأثیر قابل توجهی در انتقال حرارت سیستم دارند. همچنین مشاهده گردید که با افزایش عدد رینولدز دمای حداکثر دیواره میکرولوله کاهش پیدا میکند. بهعنوان مثال، برای عدد رینولدز 180، 360 و 720 دمای حداکثر به-ترتیب در 307.8 کلوین،304 کلوین و 302.8 کلوین رخ میدهد. علاوه براین افزایش کسر حجمی نانوذره موجب کاهش در تغییرات دما میشود. همچنین نتایج حاصل از مدل-سازی عددی با نتایج روابط تئوریک موجود که در تطابق خوبی با نتایج تجربی بودهاند، مقایسه شده است.
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