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Heat and Mass Transfer Enhancement in Rotating Disk Systems

Thesis Info

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Author

Usman, Muhammad

Program

PhD

Institute

International Islamic University

City

Islamabad

Province

Islamabad.

Country

Pakistan

Thesis Completing Year

2019

Thesis Completion Status

Completed

Subject

Mathemaics

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/10627/1/Muhammad%20Usman_Maths_2019_IIU_PRR.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676726361233

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The design of an efficient cooling system comprising of a rotating disk arrangement is essential owing to the ever-growing demand in the power output and thermal efficiency of turbomachinery systems, gas turbine, transport engineering, chemical engineering, aircraft engineering, rotating disk contractors, and many other rotating heat exchanging devices. The engineering sophistication and economic incentives of industries do also require to improve the performance of heat exchangers in order to obtain the optimum use of energy, and materials, to achieve further thermal control, and to meet the compactness requirements. Ranging from the simple turbomachinery to the state - of - the - art aerospace vehicles most of the practical rotating systems have strong connections with the rotating disk configuration, either rotating freely or in a housing. This signifies the importance of the geometrical configuration of rotating disk system as it relates to a large number of practical applications, namely, spin coating, rotational air-cleaners, disk drivers, atomizers, jet cooling, food processing, rotating machinery, medical equipment and many more. Further understanding of the convective transport mechanism due to a rotating disk, whose surface is flat and also not essentially flat, is an important area of research. Explanation to the non-trivial augmentation in heat transfer and the identification of the agents contributing there are the fundamental reasons behind this study. Therefore, the present monograph focuses on the prediction of the enhanced heat transfer rate in some complex flows arising in the rotating disk system as it directly links to the cooling performance of such systems. On the other hand the consequential mitigation of environmental degradation has provoked many techniques of heat transfer augmentation. In this context, different approaches, such as active, passive and combined (i.e. both active and passive), techniques are employed to achieve the heat transfer augmentation. The primary objective of this work is to investigate the impact of non-homogenous distribution of nanoparticles, non-uniform disk temperature distribution, disk transpiration, waviness of the disk and the external forced flow to the rotating disk geometries. The detailed discussion of obtaining the heat transfer enhancement via Nanofluid is given in Chapter 2 where the weak prediction of homogeneous models (as compared to non-homogeneous model) on heat transfer enhancements is identified. Almost 67% enhancement in heat transfer rate is noted for the non-uniform nanoparticle distribution (non-homogeneous modeling) for some fixed values of the involved parameters whereas the uniform distribution (homogeneous model) yields only 22% which signifies the role of nanoparticle distribution in heat transfer augmentation. The research work presented in Chapter 2 are published in Thermal Science: Year 2018, Vol. 22, No. 6A, pp. 1-16. Some new classes of rotating disk temperatures have been considered in Chapter 3 due to which increased heat transfer rates were noticed. For instance, exponentially increasing disk temperature of a free rotating disk in the quiescent air yields 27% augmentation in heat transfer rate while a radially increasing non-linear disk temperature corresponds to 15% intensification in heat transfer rate as compared to isothermal disk. The heat transfer augmentation has also been acquired by the mass addition/removal to flow inside the gap between a cone and a disk. Chapter 4 highlights this analysis in detail. A serious lack of work is felt in the study of surface roughness effects on rotating disk boundarylayer and this is focused in Chapters 5 and 6. The sinusoidal-shaped (wavy) disk has been opted as it can be dealt quite easily with the mathematical modeling. A comprehensive discussion has been made in the aforementioned Chapters highlighting the role of surface texture in different flow regimes like non-isothermal distribution of disk temperature and under uniform forced flow. The findings of Chapter 5 are published in International Journal of Heat and Mass Transfer: Year 2019, Vol. 129, pp. 96-102. Finally, inferences are drawn in the Conclusions section which are very helpful in order to understand the heat transfer enhancement mechanisms in rotating disk systems. It is important to mention here that the existence of the analogy between convective heat and mass transfer phenomena leads this study to cover the topic of mass transfer in a rotating disk systems as well.
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جغرافیائی تناظر

سیالکوٹ پاکستان کا ایک قدیم شہر ہے۔یہ ۳۲ درجے ۳۰ دقیقے عرض بلد شمالی اور ۷۴ درجے ۳۲ دقیقے طول بلد پر واقع ہے۔یہ سطح سمند ر سے ۸۰۰ فٹ بلند ہے۔(۱)اس کے شمال میں ضلع گجرات اور جموں کا علاقہ ہے۔جنوب میں بھارت کا ضلع امر تسر ،مشرق میں ضلع گورداس پور،مغرب میں ضلع شیخوپورہ اور جنوب مغرب میں ضلع گوجرانوالہ ہے۔(۲) مغرب میں دریائے چناب ضلع سیالکوٹ اور ضلع گجرات کے درمیان بہتا ہے ۔سیالکوٹ رچنا دو آب میں (دریائے راوی اور چناب کے درمیان)واقع ہے اوراس کا بالائی حصہ (جو کوہ ہمالیہ کی تلہٹی میں واقع ہے) بہت زرخیز ہے۔جنوبی حصہ نسبتاً کم زرخیز ہے۔(۳)شہر کے شمال سے گزرنے والے دریائے چناب کے سوٹے کوہ ہمالیہ سے پھوٹتے ہیں ۔یہ قدیم دریا عوامی جمہوریہ چین کے قریب سے شروع ہوتا ہے۔قدیم زمانے میں اس دریا کو ’’چین آب ‘‘ کے نام سے پکارا جاتا تھا۔جو زمانے کے ساتھ ساتھ تبدیل ہوتا ہوا آج دریائے چناب کہلاتا ہے۔یہ دریا جموں کشمیر کے پہاڑی علاقوں سے گزرتا ہوا جب ضلع سیالکوٹ میں داخل ہوتا ہے تو ہیڈ مرالہ کے مقام پر یہاں اس میں دو اور دریا اٹھکیلیاں کرتے اور زندگی کی بہاریں تقسیم کرتے آکر مل جاتے ہیں۔یہ دریائے جموں توی اور دریائے (مناواں) مناور توی ہیں۔(۴)

          دریائے چناب میں مرالہ کے مقام پر بند باندھ کر نہر اپر چناب نکالی گئی ہے۔اس نہر کی تین شاخیں ہیں۔ایک شاخ کا پانی تحصیل ڈسکہ اور باقی دو شاخوں کا پانی ضلع گوجرانوالہ کے کھیتوں کو سیراب کرنے میں استعمال ہوتا ہے۔نہر مرالہ راوی لنک ضلع سیالکوٹ کے مغربی حصے کو سیراب کرتی ہے اور جو پانی باقی بچ جاتا ہے۔اس لنک کے ذریعے دریائے راوی میں چلا جاتا ہے تاکہ دریائے راوی سے نکلنے والی نہر اپر باری دو آب...

مسلم عائلی قوانین آرڈیننس ۱۹۶۱ء کی دفعہ ۴ (یتیم پوتے وغیرہ کی میراث) : اسلامی احکام کی روشنی میں تحقیقی جائزہ

Issues of inheritance have been thoroughly maintained in the Holy Quran and Sunnah. As per these injunctions, the principle of AL’Aqrab fal’aqrab “the closest in kin” is to be observed. According to these principles, grandchildren, even though orphaned, have no right to inherit grandfather in the presence of direct children. On the other hand, section 4 of Muslim Family Laws, 1961 grants a share to orphaned grandchildren from the inheritance of his grandfather. Whereas, as per the constitution, no law can be enacted which is repugnant to the injunctions of the Holy Quran and Sunnah, now, whether the above mentioned section is in conformity with the injunctions of the Holy Quran and Sunnah or not is to be treated properly. If not, so from which perspective, it is repugnant to the Islamic Injunctions? These questions have been analysed critically in this paper and finally it has been concluded that section 4 of Muslim Family Laws Ordinance, 1961 contrasts with the injunctions as laid down in the Holy Quran and Sunnah.

Adsorption of Water-Soluble Polymers on Solid Surfaces

The adsorption of water-soluble polymer, Poly (vinylpyrrolidone) on kaolin has been investigated as a function of polymer concentration. The highest amount of polymer adsorbed was 1.19 mg m-2 with an average value of 1.142 mg m-2. The effect of different parameters like pH, molecular mass of polymer and pre-heat treatment on the adsorption of PVP has been deliberated. The 20.7% decrease in adsorption in pH ranging from 2–10 has been found. Maximum adsorption was observed at pH 5.6 that was also molecular mass dependent. By increasing the pretreatment temperature of kaolin, the amount of polymer (PVP) adsorbed was also increased up to certain temperature and was then decreased. This trend was attributed to variation in specific surface area of kaolin with the temperature. FTIR–Spectroscopy reveled the disappearance of C=O in PVP molecule, conversion of C-N to C=N and formation of C-O from C=O during adsorption process. Further the shifting of IR bands of outer OH groups of kaolin to lower frequency was indicated the involvement of OH groups of kaolin in hydrogen bonding with carbonyl group of PVP. In case of adsorption of Poly (vinylpyrrolidone) (PVP) on AEROSIL®OX 50, the average value of amount adsorbed was 0.6 mg.m-2. The adsorbed amount was noted to be highest at low pH and decreased by 2.7% if the pH was varied from 3 to 6.3. Same trend was observed for all the three PVP samples indicating that the adsorption-pH dependent trend was almost independent of molecular mass of the polymer. However, the adsorption of PVP on the AEROSIL®OX 50 was slightly dependent on its surface charge. This trend was attributed to the fact that the dissociation of Silanol groups occurring at the pH greater than 3 effectively prohibited the formation of hydrogen bonds between Silanol groups of silica and PVP. The hydrophobic interactions played significant role in the adsorption phenomenon. Further, the pretreatment temperature beyond 523K increased the adsorption of polymer sharply. The FTIR spectroscopic results indicated that C=O group disappeared during the adsorption process. It suggested the formation of hydrogen bonding between Hydrogen of silanol and oxygen of C=O. The same was observed in case of N-C=O groups PVP which is electron donor in nature. From the adsorption data it was concluded that kaolin is an excellent adsorbent for PVP with an average value of 1.142 mg m-2 as compared to silica having average value of 0.6 mg m-2.Though the ultrasonication of kaolin up to 30 min led to decrease in size and widened its distribution little bit but it increased the surface charge of kaolin significantly. The addition of (PVP) polymer widened the size distribution of particles and increased the surface charge as well as Zeta potential of kaolin. This effect was increased with the increase in concentration and molecular mass of the polymer and hence the stability of dispersion. This trend was attributed to columbic as well as steric stabilization of dispersion. The addition of 0.1 to 0.15 mg/g of poly (diallyldimethylammonium chloride) (PDADMAC) resulted in flocculation of kaolin. The maximum removal of the turbidity/flocculation was achieved at 0.1 mg/g of polyelectrolyte concentration for the samples homogenized for 60 min. Further increase in the concentration of polymer caused an increase in residual turbidity as well as zeta potential of the system and hence re-stabilized the system. This was due to surface charge neutralization of particles by adsorbed polymer and formation of further adsorbed layers through hydrogen or hydrophobic bonding mechanisms. The settling rate was noted to be function of polyelectrolyte concentration. The highest settling rate (0.75 cm/min) was observed for 0.3 mg/g of kaolin concentration. For the sample ultra-sonicated for 10 min, flocculation was initiated at the concentration of 0.2 mg/g, and much broader (0.2 to 1.6 mg/g) flocculation window was observed and the optimum flocculation dosage was 1.4 mg/g. The maximum removal of the turbidity was also pH dependent and was achieved at concentration of 0.2, for pH 8, 0.4 for pH 10 and 0.8 mg/L for pH 9. The flocculation of kaolin induced by PDADMAC at pH 8 occurred from 0.2 to 2.0 mg/L whereas, pH 9 a very narrow (0.8-1.2 mg/L) flocculation window was observed and same was the case for pH 10. The largest floc size of aqueous suspensions of kaolin was observed at pH 10. From the flocculation of silica by PDADMAC it was observed that maximum removal of the turbidity was achieved for polyelectrolyte concentration as 0.2 mg/g of silica and flocculation zone was from 0.1 to 0.2 mg/g. The optimum doze was found to be 0.2 mg/g. As the concentration of the polymer was increased the number of the particles was decreased and size was increased due to formation of aggregates. For the sample having 60 min homogenization, flocculation started at the concentration of 0.2 mg/g, flocculation window, having the flocculation zone from 0.2 to 2 mg/g was observed. Though the overall impact of ultrasonication times had little impact but it was noted that for the samples homogenized for 10 min, flocculation started at the concentration of 0.3 mg/g and ended at 1.2 mg/g. However the optimum flocculation dosage became 0.6 mg/g indicated that ultrasonication played a very significant role in the flocculation of negatively charged particles. The maximum removal of the turbidity is achieved at the optimum conc of 1.4 mg/g, for pH 8 with the flocculation zone of 1.2 to 3.6 mg/g, 2.0 mg/g for pH 9 with flocculation zone of 1.2 to 4.0 mg/g and 2.4 mg/g for pH 10 having the flocculation zone of 1.2 to 4.4 mg/g of silica respectively. Further increasing the concentration of polymer the residual turbidity of the system increases, and restabilization of system occurs. Volume % of particle fraction remained almost constant in the absence of polycation and uni-model curve was obtained for all the pH values while it was significantly reduced after the addition of polymer and flocculation. From the above observations it was concluded that PDADMAC was a best flocculant for both of the pigments. However it showed better performance for silica rather than kaolin.