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Experimental Study of Heat Transfer by Natural Convection Through Vertical Cylinders

Thesis Info

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Author

Muhammad Arshad

Program

PhD

Institute

Pakistan Institute of Engineering and Applied Sciences

City

Islamabad

Province

Islamabad

Country

Pakistan

Thesis Completing Year

2012

Thesis Completion Status

Completed

Subject

Applied Sciences

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/2759/1/1468S.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676726155228

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Miniature Neutron Source Reactor (MNSR) is a passively cooled system operating in Natural convection heat transfer mode. A typical MNSR located at the premises of PIEAS (Pakistan Institute of Engineering and Applied Sciences) called as Pakistan Atomic Research Reactor-II, PARR-II. From safety analysis point of view the literature lacks any experimental study or information that can be used to predict the outer surface temperatures along the axial length of a fuel rod in the reactor core. Similarly the literature also lacks any information regarding the prediction of the fluid exit bulk temperature as a function of the reactor thermal power. The thermal power range for the operation of this particular MNSR studied ranges from 5.4 to 27 KW. The current experimental study is a pioneering effort to find a solution to the above mentioned problem. Hence, steady state heat transfer by natural convection was investigated experimentally from an enclosed assembly of thin vertical cylinders at high Grashof numbers. The published literature lacks experimental data regarding such a study in the turbulent boundary layer regime. An enclosed assembly consisted of a 3 x 3 array of vertical cylinders immersed in a large volume tank of water was used. All the cylinders were electrically heated. Various uniform heat fluxes were applied to each cylinder and the surface temperature at different positions along the cylinders were measured. The experimental results show that the surface temperature increases axially up to a certain length, then decreases due to some extra mixing which increases the heat transfer. However, such a behavior is expected to have little effect if the enclosed assembly consists of a large number of thin vertical cylinders. A criterion has been proposed for the determination of the onset of turbulent boundary layer in an assembly. The local heat transfer coefficient, local Nusselt number and local modified Rayleigh number have been presented for the experimental data. It has been found that a much better representation of experimental data results, if the Nusselt number is presented as a function of modified Grashof number and Prandtl number separately instead of modified Rayleigh number. This representation includes the effect of different fluids and L/d ratios. Similarly empirical correlations between overall Nusselt number and average modified Rayleigh number have also been developed based on the data of the assembly of cylinders used in the current study. This empirical correlation for an assembly * developed in current study is valid for 1.28 x 10 12 £ RaL £ 1.18 x 1013. A much better generalized correlation has also been proposed for natural convection heat transfer from a single vertical cylinder in an infinite medium which shows a better fit to all the currently available experimental data. The literature also lacks such a generalized correlation. The results obtained in this study have been utilized to predict the axial surface temperatures as well as the fluid bulk outlet temperature of PARR-II. Hence the correlations developed from current study are applicable to all thermal power ranges in PARR-II type MNSR reactors or any other assembly of vertical heated thin cylinders.
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محمد مجید زبیری

محمد مجید زبیری
افسوس ۲۳؍ مئی کو شبلی کالج کے سابق استاد جناب محمد مجید زبیری کا علی گڑھ میں انتقال ہوگیا، ریٹائر ہونے کے بعد وہ جناب سید صباح الدین عبدالرحمن مرحوم کے اصرار پر دارالمصنفین کے شعبۂ انصرام سے وابستہ ہوئے، اپنی نیکی، بھلمنساہت، صلح پسند طبیعت اور ایمانداری و دینداری کی وجہ سے ہر طبقہ میں مقبول و محترم تھے، صحافی و شاعر بھی تھے تقریباً دو سال قبل سخت بیمار ہوئے، علاج کے لیے اپنی صاحبزادی کے پاس علی گڑھ چلے گئے اور وہیں سے سفر آخرت اختیار کیا، اﷲ تعالیٰ بال بال مغفرت فرمائے اور پس ماندگان کو صبر و رضا کی توفیق دے، آمین۔ (ضیاء الدین اصلاحی، جون ۱۹۹۲ء)

Social Welfare in the Religions of Subcontinent a Critical Study

Islam, Hinduism and Buddhism are among the major religions of Sub-continent. The present study highlights the fact that public welfare is preached by all of these religions. Giving alms for the sake of public welfare is an important part of various Hindu religious practices. The role of latest reformist movements is also worth mentioning along with the Hindu literature related with social well-being. Arya Sam฀j movement did many activities for the welfare of people. The founder of Buddhism made efforts for the betterment of mankind and used his religion and teachings to propagate public welfare. Buddhism rejected the caste system and played an important and effective role to minimize the sufferings of affected community. In this regard Islam rises to the highest pedestal as the topic of Holy Quran is Man. It focuses not only on the worldly success of man but also his success in the hereafter. Islam has gone a step ahead than other religions as the activities of public welfare are considered worship in it. The rights of human beings are given great importance and they are given no less importance than rights of Allah. Moreover, the Holy Prophet (S. A. W) took noteworthy steps for the welfare of whole mankind without any discrimination and these are highlighted in this paper. Islam also gives lineaments of the methods and modes of public welfare and goes beyond the other Semitic and non-Semitic religions in this regard. This paper explores and highlights the measures taken by the mentioned religions in a comparative manner and also proves that Islamic concept of social welfare is not only limited to human beings but it also enfolds other living beings and even plants. Islam provides a complete road map of public welfare. Islamic society not only progresses financially but it also focuses on spiritual, ideological and social progress. The aim of social welfare cannot be achieved unless equilibrium is maintained between rights and duties. Islam not only stresses on the rights of the weak but also safeguards the rights of the rich.

الاعجاز البیانی فی ضوء النصوص القرآنیة

There is no doubt that the Holy Qur'an is a great blessing from Almighty Allah. If this had been the only blessing bestowed on this final Ummah, we would still have surpassed all previous ummahs in blessings. This book is the epitome of sweetness. Its beauty stretches from the tongue of the .2 gam and can be felt in the very depths of the heart of the listener. One can not tire of reading it, nor of listening to it; the more one delves into it, the richer its treasures reveal themselves to be. This book appeals equally to a scholar and a layperson at the same time, and guides them both. It has the power to awaken nations from ignorant slumber, and to show them the path to success. One aspect of this brilliance is the fact that not only does it encompass vast treasures of wisdom and knowledge, but it is also a literary and linguistic miracle. This latter point is expounded further in this present research work. The direct and implied meaning of the text of the Holy Book is indeed beautiful. The very vocabulary and its mesmerizing usage are so apt and balanced that there can be absolutely no comparison. Revealed at the time when Arabia was at the pinnacle of linguistic excellence, nothing could face up to its splendor, attempts by the disbelievers who put together all their resources to this futile end notwithstanding. This was one reason why the opponents of this message, having completely failed this way, resorted to violence and warfare. If they could have countered the linguistic beauty of the Holy Qur'an, the world would not have seen the battles of Badr, Uhud and Khandaq. To illustrate this linguistic miracle of the Holy Qur'an, a few styles have been selected from its vast treasures of Ilm-ul-Bayan. These include, but are not limited to, the vocabulary, the usage of similes and metaphor etc. that challenge human ability and leave it pale in comparison. The Holy Qur'an chooses different styles beautifully based on specific contexts, catering beautifully to the addressee and the message. Where the circumstance calls for simplicity, the Holy Qur'an employs a simple yet brilliant style, and where the need is for eloquence, it engages a sparkling dignity. Thus it is a direct and correct conclusion that the Holy Qur'an's linguistic approach is a string of gems that embodies many different styles; each gem is magnificent on its own, and at the same time, the majesty of the string is revealed even more fully when considered as a whole. A miracle of the Holy Qur'an is that it showcases divine brilliance in a way that is comprehendible by efforts of human knowledge and imagination without compromising its full magnificence. This becomes evident in another way also. It is interesting to note that the best amongst human literature now employs the same vocabulary and similar linguistic techniques, and yet the distinction between the products of the human mind and this divine book has not been bridged at all. 1. Arabic, for the larger Islamic concept of 'nation' that surpasses all geographic boundaries. 2. Arabic, for one who recites. 3. The three battles from the early age of Islam. Holy Qur'an stands to this day, and shall continue to do so for all time, with all its glory as a shining testament to the boundary less divine wisdom and magnificence, for which even the entire creative prowess in the world around us is no match. This research has engaged several noted exegesis of the Holy Qur'an to identify, understand and classify a part of the linguistic magnificence of this divine book. The Glorious Qur'an's eloquent stylizations embody infinite beauty, and showcase the miracle of the brilliance of the divine wisdom. It presents a spectacular combination of eloquence that radiates beauty, and comprehensive conciseness. These are just two of the miracles that form the Holy Qur'an. The characteristics outlined in these preceding lines, and subsequently in this research show the outline of a magnificent picture, and yet this only be labeled as being hardly a drop in the ocean in comparison to the full glory of the Holy Book. I pray to Almighty Allah to accept my endeavor to showcase some of this grandeur in this research, and to make it beneficial for me, and the whole Muslim Ummah.