Numerical Investigation of Heat Transfer Enhancement in a Circular Tube with Rectangular Opened Rings

Turbulent forced convection of coolant air flow (10 m/s velocity) in a steel tube of 50 cm long having outside diameter of 60 mm and inside diameter of 30 mm with constant outside surface temperature of 1000, 1200 and 1400 Ko is numerically analyzed. The renormalization group k-ε model is used to simulate turbulence in ANSYS - FLUENT 14.5. An opened ring of rectangular cross section (5x7 mm) is fitted in the tube and separated by 8cm pitch. Results of temperature and velocity distribution along the tube center line for the case of tube with internal ribs  were compared with that of plain tube  , these results show that the use of internal ribs enhance the heat transfer rate and found to possess the highest performance factors for turbulent flow

NUMERICAL INVESTIGATION OF HEAT TRANSFER ENHANCEMENT IN A CIRCULAR TUBE USING RIBS OF SEPARATED PORTS ASSEMBLY

The paper deals with numerical investigation for the influence of separated ports assembly ribs on heat transfer ina steel tube of 50 cm long , outside diameter of 60 mm and inside diameter of 30 mm with constant outside surface temperature of 1000, 1200 and 1400 Ko.The renormalization group k-ε model is used to simulate turbulence in ANSYS - FLUENT 14.5. The ribs assembly (5x5 mm triangle passage) were fitted in the tube and separated by 8cm pitch. Results of temperature and velocity distribution along the tube center line for the case of tube with internal ribs were compared with that of plain tube , these results show that the use of internal ribs enhance the heat transfer rate and found to possess the highest performance factors for turbulent flow

Efficient Design of a Large Storage Tank for Liquefied Natural Gas

يعتبر الغاز الطبيعي واحد من مصادر التي تنتج طاقة نظيفة قليلة الانبعاثات شديدة الكثافة وصديقة للبيئة. لنقل الغاز الطبيعي، من المهم جدا تحويل الغاز الطبيعي الى الحالة السائلة لتقليل خسائر عملية النقل، لذلك تصميم خزانات لحفظ الغازي الطبيعي المسائل يعتبر من العوامل التي تساعد على دعم تجارة الغاز الطبيعي. تتميز خزانات الغاز الطبيعي المسال بحجومها الكبيرة جدا التي تصل الى 2000000 متر مكعب. يعتبر تصميم خزانات الغاز الطبيعي تكنلوجيا جديدة للكثير من الدول. تتميز خزانات الخزن بسمك عزل عالي يصل الى متر في بعض الاحيان لان الغاز المسال يكون عادة بدرجات حرارة منخفظة تصل -165 درجة سيليزية. هذا التصميم يجمع بين عدة كودات تصميم لدراسة تفصيلية لعملية تصميم خزان غاز مسال يشمل مايلي الهيكل الداخلي والخارجي للتصميم، تصميم قاعدة الخزان، تصميم الجزء العلوي من الخزان. بالاضافة الى ذلك، التصميم يتناول محاكاة تفصيلية للحرارة المتسربة من كل جزء من الخزان ليتبين ان التصميم يعمل بكفاءة عالية والحرارة المتسربة ضمن الحدود المقبولة.Natural gas is known as a green source of energy due to high purity, high energy density and environment friendly. To transport natural gas, it is an important to convert it into liquid case to reduce the cost, therefore the design of storage tank can be important factor in the natural gas trade. Liquefied natural gas (LNG) tank as a kind of storage column is quite different with other storage columns. Firstly, the size of this type of LNG tank is highly large, which comes with capacity up to 200,000 m3. LNG storage tank can be considered as a new technique in this field for many countries. Secondly, the low temperature of LNG will increase the isolation part and lead to difficult process through the operation and installation time. This work combines different designs codes to study in details the LNG tank design in terms of inner and outer construction, bottom design with corner protection, and top design with corner protection. In addition, the heat leakages have been calculated for each part to show that the heat leakage is acceptable. &nbsp

Heat Transfer Augmentation in Gas Turbine Blade Rectangular Passages Using Circular Ribs with Fins

في هذا البحث تم تصميم وبناء نظام تجريبي لمحاكاه ظروف تبريد ريشه التوربين الغازي حيث كانت درجه حراره هواء التبريد الداخل (300 كلفن ) ورقم رينولد (7901) ودرجه الحراره المحيطه (673كلفن) وتم اجراء المحاكاه العدديه باستخدام برنامج الفلونت (14.5) حيث تم دراسه تأثير الاضلاع الدائريه ذات الزعانف الوسطيه خلال مجرى مستطيل بابعاد (30 *60 ملم) وبسمك (1.5 ملم) وطول (0,5 م) على الجريان وانتقال الحراره .لاحظنا ان باستخدام الاضلاع الدائريه ذات الزعانف الوسطيه تم زياده حراره هواء التبريد الداخل بنسبه (10.22%) و نقصان بدرجه السطح الداخلي للقناه بنسبه (6.15%) وكان معامل الاداء الحراري اكبر من واحد وهذا يدل على ان الاضلاع الدائريه حسن بانتقال الحراره من خلال زياده المساحه السطحيه للانتقال وزياده الاضطراب الذي يؤدي الى زياده الخلط .In this paper, an experimental system  was designed and built to simulate conditions in the gas turbine blade cooling and run the experimental part. Boundary conditions are: inlet coolant air temperature is 300K with Reynolds numbers (Re=7901) .The surrounding constant hot air temperatures was (673 K).The numerical simulations were done by using software FLUENT version (14.5), in this part, it was presented the effect of using circular ribs having middle fin fitted in rectangular passage channel on fluid flow and heat transfer characteristics.  Ribs used with pitch-rib height of 10, rectangular channel of (30x60 mm) cross section, 1.5 mm duct thickness and 0.5 m long. The temperature, velocity distribution contours, cooling air temperature distribution at the duct centerline, the inner wall surface temperature of the duct, and thermal performance factor are presented in this paper. it can be seen that the duct with all ribs with middle fins was the better case which leads to increase the coolant air temperature by (10.22 %) and decrease the inner wall temperature by (6.15 % ). The coolant air flow velocity seems to be accelerated and decelerated through the channel in the presence of ribs, so it was shown that the thermal performance factor along the duct is larger than 1, this is due to the fact that the ribs create turbulent conditions and increasing thermal surface area, and thus increasing heat transfer coefficient than the smooth channel

Thermal Energy Storage by Nanofluids

Nanofluids are suspensions of nanoparticles in base fluids, a new challenge for thermal sciences provided by nanotechnology. Nanofluids have unique features different from conventional solid-liquid mixtures in which mm or ?m sized particles of metals and non-metals are dispersed. At  this research adding of small weight percent of magnesium oxide MgO(0.1, 0.2, 0.4 and 0.5wt.%) to pure water as working fluid in the building heating system by solar energy gave us different behavior, adding 0.1, 0.2wt,% gave low temperature gradient than the pure water, while 0.4 and 0.5wt.% gave greater temperature gradient than pure water which is desired. Keywords: Nanomaterials, Nanofluids, Thermal Energy, Energy Storage

Preparation of (PS-PMMA) Copolymer and Study The Effect of Sodium Fluoride on Its Optical Properties

Composites materials are used in many applications: solar cells, elements, light emitting diodes (LED), optoelectronic device, industrial applications in aircraft, military and car industry for their low cost, light weight, electrical properties, mechanical and optical properties. In this work, preparation of PS-PMMA copolymer have been investigated.  The sodium fluoride was add to PS-PMMA copolymer with concentrations are (0,1,2,3) wt.%. The samples were prepared casting technique. The optical properties of composites in the wavelength range (200-800) nm. The results showed that the absorption coefficient, extinction coefficient, refractive index and  real and imaginary dielectric constants PS-PMMA copolymer are increasing with increase the sodium fluoride concentration. Keyword: composite, copolymer, absorbance, dielectric constants

Preparation and Characterization of (PMMA-Berry Paper or Plan Leaves) Composites

In this paper, study the effect of addition the Berry Paper or Plan Leaves on optical properties of PMMA. The samples have been prepared by casting technique and different thickness. . The absorption and transmission spectra have been recorded in the wavelength range (200 – 800) nm. The experimental results show that the absorption coefficient, energy gap of the indirect allowed and forbidden  transition, extinction coefficient, read and imaginary dielectric constant and refractive index are changing with increase the of Berry Paper or Plan Leaves concentration

Optical Properties of (PVA-CoCl2) Composites

Polymers are used in a wide range of manufacture applications for their low cost, light weight, mechanical and optical properties. In this paper, study effect of addition cobalt chloride on  optical  properties of poly-vinyl alcohol(PVA). The cobalt chloride was add to poly-vinyl alcohol with weight percentages are (0,1,2,4) wt.%. The absorption and transmission  spectra has been recorded in the wavelength range (200-800) nm. The experimental results showed that the absorption coefficient, optical energy gap, extinction coefficient, refractive index and  real and imaginary dielectric constant effected by addition different weight percentages from cobalt chloride. Keyword: polymer, optical constants, absorption, cobalt chloride

Preparation of [Co(NH3)5Cl]Cl2 Complexes and Characterization of (PVA- [Co(NH3)5Cl]Cl2]) Composites

In this paper , preparation of  [Co(NH3)5Cl]Cl2 complexes and study the effect of addition [Co(NH3)5Cl]Cl2 complexes on optical properties of polyvinyl alcohol. The  samples have been prepared by casting technique and different thickness. . The absorption and transmission spectra has been recorded in the wavelength range ( 200 – 800 ) nm. The experimental results show that the absorption coefficient, energy gap of the indirect allowed and forbidden  transition, extinction coefficient, read and imaginary dielectric constant and refractive index are changing with increase the of [Co(NH3)5Cl]Cl2 concentration. Key words: polymer, optical properties, complexes

Advancements in Fresnel Lens Technology across Diverse Solar Energy Applications: A Comprehensive Review

Concentration of solar energy may be obtained by reflection, refraction, or a combination of the two. The collectors of a reflection system are designed to concentrate the sun’s rays onto a photovoltaic cell or steam tube. Refractive lenses concentrate light by having it travel through the lens. The sun’s rays are partially reflected and then refracted via a hybrid technique. Hybrid focus techniques have the potential to maximize power output. Fresnel lenses are an efficient tool for concentrating solar energy, which may then be used in a variety of applications. Development of both imaging and non-imaging devices is occurring at this time. Larger acceptance angles, better concentration ratios with less volume and shorter focal length, greater optical efficiency, etc., are only some of the advantages of non-imaging systems over imaging ones. This study encompasses numerical, experimental, and numerical and experimental studies on the use of Fresnel lenses in various solar energy systems to present a comprehensive picture of current scientific achievements in this field. The framework, design criteria, progress, and difficulties are all dissected in detail. Accordingly, some recommendations for further studies are suggested