No abstract

This paper presents an experimental study to investigate the heat transfer enhancement in a horizontal circular tube using three metal oxide (ZrO 2 (80 nm), γ Al 2 O 3 (20 nm), CuO (40 nm)distilled water) nanofluids and fitted with three types of twisted tape (typical twisted tape, twisted tape with V-cut and clockwise-counter clockwise twisted tape) with twist ratios (TR=4, 6, 8). The studied concentrations of nanofluids are (φ = 0, 0.01, 0.05, 0.1, 0.5, 1, 2, 3% by volume) under fully developed turbulent flow and uniform heat flux condition.The experimental test rig includes all the required instruments to study the heat transfer enhancement. All the tests were carried out with Reynolds number range (2490-20100) and uniform heat flux (2108-9280 W/m 2 ). The experimental study also includes preparation and measurement of properties of density, viscosity and specific heat of nanofluids. The pressure drop, wall temperature, flow rate, heat flux and temperature of nanofluids.For nanofluid, the maximum enhancement in the heat transfer (Nusselt number ratio) was (7.5), and the maximum thermal performance factor was (3.9) using (CuO)-distilled water nanofluid, clockwise-counter clockwise twisted tape with twist ratio (TR=4) at Reynolds number (2490) and concentration (φ=3%). The average Nusselt number and friction factor with Reynolds number, nanofluid concentration and twist ratio were correlated for each type of the used nanofluid. ‫دائري‬ ‫أنبوب‬ ‫داخل‬ ‫الملتويت‬ ‫األشرطت‬ ‫مع‬ ‫الذقت‬ ‫متناهيت‬ ‫الموائع‬ ‫باستخذام‬ ‫الحرارة‬ ‫انتقال‬ ‫لتحسين‬ ‫تجريبيت‬‫دراست‬ ‫الخالصت‬ ٍِ ‫أّىاع‬ ‫ىثالثخ‬ ‫اىجشَبُ‬ ‫و‬ ‫اىحشاسح‬ ‫الّزقبه‬ ‫ػَيُخ‬ ‫دساصخ‬ ‫إجشاء‬ ‫رٌ‬ ‫اىجحث,‬ ‫هزا‬ ‫فٍ‬ ‫اىَيزىَخ‬ ‫األششطخ‬ (typical, V-cut and clockwise-counter clockwise) ( ‫اىزىاء‬ ‫ّضت‬ ‫ثثالثخ‬ ‫رصُْؼهب‬ ‫رٌ‬ TR=4, 6, 8 ‫داخو‬ ,) ‫هٍ‬ ‫ٍؼذُّخ‬ ‫ألمبصُذ‬ ‫اىذقخ‬ ‫ٍزْبهُخ‬ ‫اىَىائغ‬ ٍِ ‫أّىاع‬ ‫ثالثخ‬ ‫ثبصزخذاً‬ ‫اىَْبرج‬ ‫مو‬ ‫اخزجبس‬ ‫رٌ‬ ‫أفقٍ.‬ ‫دائشٌ‬ ‫أّجىة‬ (ZrO 2 (80 nm), γ Al 2 O 3 (20 nm), and CuO (40 nm))-distilled water ‫وثزشامُز‬ (φ = 0, 0.01, 0.05, 0.1, 0.5, 1, 2, 3% by volume)

No abstract

This work presents an experimental investigation for effective thermal properties of open cell ceramic foam (80.13 Al 2 O 3 , 17.79 SiO 2 , 1.57 MgO, and 0.51 Na 2 O. % weight),which were measured using the Transient Plane Source (TPS) technique, and the parameters, which influenced them, and the influence of foam structure. Three types of pore per inch (ppi) were tested (10, 30 and 50). Three sensors were used, K5599 (of 60 mmdiameter), K4922 (of 30 mmdiameter) and K5501 (of 13 mmdiameter).The percentage difference between the highest and lowest results for each sensor and ppi are: for K5501 sensor were 34% in 10 ppi, 15% in 30 ppi and 18% in 50 ppi, for sensor K4922 were 19%, 11% and 13%, respectively, and for K5599 were 17%, 14% and 16%, respectively. The results show that the sensor K4922 is the more suitable sensor to test such material especially which has high ppi.

This paper presents an advanced approach to compute the three-dimensional, rotational, adiabatic, inviscid flow of a perfect gas in a highly twisted transonic axial turbine stage. The time-dependent Euler equations, expressed in a Cartesian coordinate system, are solved using a time marching method and a finite volume approach. The absolute flow is computed in the nozzle vanes passage, whereas the relative flow is computed in the rotor blades passage. The phase relation of nozzle and rotor flows and the related blade row interaction are accounted for in the time-space domain. The results show that the present method of calculation makes a practical contribution to predict actual turbine flows through a turbine stage that have an arbitrary number of vanes and blades for each nozzle and rotor. It is clear that this flow has a three dimensional aspects, in spite of the high hub/tip ratio which has theoretically a two-dimensional flow aspects.