Shell and tube heat exchangers are widely used for various industrial refrigeration applications. There is no data available in open literature on the direct expansion evaporation characteristics of refrigerants on the shell side of tube bundle. With the current Ozone Depletion and Global Warming issues it is critical to develop systems with low charge refrigerants especially with natural refrigerants such as ammonia which has zero Ozone Depletion Potential (ODP) and zero Global Warming Potential (GWP). A comprehensive literature survey has been presented to summarize previous single phase correlations for estimating heat transfer coefficient inside circular tubes and studies performed with ammonia boiling outside single tube and bundles and the correlations thereof developed. Considerable amount of work has been performed and correlations developed for estimating heat transfer and pressure drop in smooth circular tubes for single phase flow. There are limited studies available on pool boiling and spray evaporation of ammonia outside single tube and bundle. As of now, there are no studies available in the open literature on the subject of direct expansion evaporation of refrigerants. The basic purpose of the present study is to quantify the effects of various parameters such as saturation temperature, heat flux, inlet quality and degree of exit superheat on the heat transfer performance for ammonia boiling on the shell side of tube bundle under direct expansion mode, and to develop empirical correlations. Overall performance of the heat exchanger and performance of individual passes are also studied. The design and details of the single phase and two phase experimental setup, instrumentations, data acquisition system and test heat exchanger are described. Single phase experiments were performed to develop single phase correlations for specific geometry and flow conditions for estimating heat transfer coefficient inside tube bundle using simple Wilson plot and modified Wilson plot method. Prandtl number was varied from 10 to 20, with Reynolds number ranging from 3000 to 15000. The correlations developed are compared vii with existing single phase correlations and were found to be in good agreement with the previous studies. Two phase experiments were performed at steady state conditions with ammonia boiling on the shell side of heat exchanger, while water/glycol solution flowing in the tubes. Saturation temperature was varied from -1.7 to -20 , inlet quality was varied from 0 to 0.3, and heat flux was varied between 5 and 45 , with exit degree of superheat ranging from 2 to 10 . Heat transfer coefficient was observed to increase with saturation temperature and heat flux and decrease with exit superheat (quality) because of the diminishing effect of boiling and dominance of single-phase sensible regime. The effects of inlet quality on the average bundle performance were found to be negligible. Heat transfer coefficient slightly decreased or remained unchanged with inlet quality. The quality effects were found to be more dominant at higher saturation temperature than at lower saturation temperature. Bundle effect was observed between the passes which was a function of saturation temperature, heat flux and exit degree superheat. The present data suggests that bundle effect is less significant at low heat flux, with lower degree of exit superheat. The variations in heat transfer coefficients of individual passes are usually smaller under these circumstances. At higher exit degree superheat and heat flux the upper tubes experienced greater dry out which resulted in a sharp drop in their performance. The trend was similar across the saturation temperature range. The effects of exit degree of superheat became more dominant on the bundle performance over heat flux when ammonia was subjected to vapor quality at the inlet of the evaporator. With increase in the inlet quality the performance of lower three passes converge. Two phase pressure drop under direct expansion mode was found to be sufficiently small. The effects of saturation temperature and inlet quality on pressure drop were negligible. Pressure drop marginally increased with decrease in the degree of exit superheat and with increase in the heat flux.
مولانا ابوالعرفان خاں ندوی مرحوم جناب مولانا ابوالعرفان خاں ندوی صاحب ۱۷؍ نومبر کو تقریباً ساڑھے تین بجے شب میں اپنے رب کے حضور پہنچ گئے۔ اناﷲ وانا الیہ راجعون۔ عالمِ کی موت کو عالم کی موت سے تعبیر کیا جاتا ہے، مولانا مرحوم کی وفات ہوئی تو یہ محسوس ہوتا ہے کہ علوم کا ایک جہان ویران ہوگیا ہے، ان کے احباب و رفقاء اور متعلقین و تلامذہ ہی خوب جانتے ہیں کہ کیسی مجموعۂ فضائل ہستی کو انھوں نے سپردخاک کردیا۔ مولانا مرحوم کا وطن شیرازہند دارالخیور جونپور تھا، لیکن جونپوری کی نسبت محض ایک وطنی نسبت نہیں تھی، ان کی شخصیت میں علم و ادب، فلسفہ و کلام، وقار و استغناء تواضع، منکسر المزاجی، مہمان نوازی بلکہ دلنوازی کی وہ تمام روایات مجتمع تھیں جن کے لیے خطہ جونپور کبھی رشک ہرات و نیشاپور تھا اور جن کی وجہ سے صاحبقران بادشاہ شاہجہاں نے کہا تھا کہ پورب شیراز ماست۔ وہ جونپور کے ایک علمی خانوادہ میں پیدا ہوئے ان کے والد جناب مولانا دین محمد صاحب اس علاقہ کے مشہور عالم دین تھے اور مولانا حافظ عبداﷲ غازیپوریؒ کے خاص شاگرد تھے جو اتباع سنت اور زہد و ورع میں بھی ممتاز تھے۔ والد ماجد سے ابتدائی تعلیم حاصل کرنے کے بعد وہ مدرسہ امدادیہ دربھنگہ میں زیر تعلیم رہے، دارالعلوم دیوبند میں بھی داخلہ لیا، مگر جلد ہی ۳۹ء میں ندوہ آگئے اور یہیں تعلیم مکمل کی، فراغت کے بعد دارالمصنفین میں مولانا سید سلیمان ندویؒ کی رہنمائی میں فلسفہ و کلام اور تاریخ کی کتابوں کا مطالعہ کیا، اس کے بعد دارالعلوم ندوۃ العلماء میں درس و تدریس کی خدمت پر مامور ہوئے اور دمِ واپسیں تک ندوہ سے ان کا رشتہ استوار رہا، ۶۷ء میں شیخ عبداﷲ مرحوم کی دعوت پر کشمیر کے ایک تعلیمی ادارہ سے بھی وابستہ رہے...
In most of service organizations particularly in Pakistan financial sector, employees have reduced their job performance and shortened quality of work due to many factors influencing them at workplace. This research study aims to explore such antecedents in view of Islam that can improve the quality of work in banking sector wherein mediating effect of perceived job performance has been tested. Model variables of this study have also been described in the Islamic perspective. Islam is complete religion in all respect and provides foundation for quality of work. Accuracy & beatification in work, discipline, sequence of tasks, impartiality, and Islamic job satisfaction, knowing ourselves and its link with knowing to our God are parts of quality of work and employees’ performance in the Islamic point of view. The target population of this study covers 20,514 employees of banking sector working in capital cities of Pakistan. Data were collected via cross sectional approach from 380 desk and frontline officials of Public and private banks. Confirmatory factor analysis and structural equation modeling techniques were used for data analysis. Findings of this research are demonstrated that job satisfaction and emotional intelligence are found the valuable antecedents of job performance and quality of work where employee’s job performance has been proved as a partial mediator between antecedents and quality of work. The two antecedents i.e. Job satisfaction, emotional intelligence of perceived job performance and quality of work have been supposed in this study to take as interpreters for the improvement of employees’ contentment and abilities in the working environment of banking sector. These are positively persuaded to job performance and quality of work. A practical exposure is offered by this research that organizational education about importance to employee’s satisfaction and emotional intelligence would be vital for achieving optimum results in this industry.
Uniformly Convex and Bazilevic Functions This work is in the field of Geometric Function Theory in which we study geometric properties of analytic functions. It was originated around the turn of 20th century and has many applications in the field of applied sciences such as engineering, physics, electronics, medicines. In this dissertation, we define and discuss some new subclasses of normalized analytic functions by using some integral operators such as the operator Q a given by Q a f(z) z a ( )za 1 ta 0 2 log z t 1 f (t)dt, where G denotes gamma function, f(z) is analytic in open unit disc, a>0 and 0. We also study generalized Bazilevič functions. The functions in these classes generalize the idea of Bazilevič functions, k-uniformly convexity and bounded boundary and bounded radius rotations. The subordination and convolution tools are used to investigate the geometric properties of the functions in these classes and several inclusion results with some interesting consequences have been proved. We have investigated the univalency condition and coefficient bounds, arc length problem, integral preserving properties and rate of growth of Hankel determinant for these functions. The most of our results are sharp and they have been connected with previously known results.