Begell House Inc.
Heat Transfer Research
HTR
1064-2285
50
9
2019
EXPERIMENTAL INVESTIGATION ON HEAT TRANSFER ENHANCEMENT WITH LOOSE-FIT PERFORATED TWISTED TAPES
821-837
Sibel
Gunes
Department of Mechanical Engineering, Faculty of Engineering, Erciyes University, Kayseri 38039,
Turkey
Ersin
Karakaya
Department of Mechanical Engineering, Faculty of Engineering, Erciyes University, Kayseri 38039,
Turkey
The thermal and flow resistance characteristics in a tube equipped with loose-fit perforated twisted tapes (LPTTs) were examined experimentally under uniform heat flux conditions. Two different twisted tape widths (W = 52 mm and 54 mm), which are smaller than the tube inside diameter of 56 mm, were taken into account with the purpose of minimizing the excessive friction loss related to the full width twisted tape elements. The experimental work was carried out with two different twisted tape width ratios (W/D = 0.9285 and 0.9642) and three different twist ratios (y/D = 2.0, 2.5, and 3.0) at a constant hole diameter ratio d/D = 0.0714, in a range of Reynolds numbers from 4859 to 24,000. The experimental results showed that the Nusselt number (Nu) and friction factor (f) increase with increasing W/D and decreasing y/D. A maximum value of the thermal performance factor (TPT) of 1.35 was provided by the use of a twisted tape with W/D = 0.9642, and y/D = 2.0 at Re = 5200. Consequently, correlations of Nu, f, and TPF for all investigated cases were also proposed.
MHD THIN FILM OLDROYD-B FLUID WITH HEAT AND VISCOUS DISSIPATION OVER OSCILLATING VERTICAL BELTS
839-849
Mehreen
Fiza
Department of Mathematics, Abdul Wali Khan University, Mardan 23200, Pakistan
Saeed
Islam
Department of Mathematics, Abdul Wali Khan University Mardan, 23200 Pakistan
Hakeem
Ullah
Department of Mathematics, Abdul Wali Khan University Mardan, 23200 Pakistan
Z.
Ali
Department of Mathematics, Abdul Wali Khan University Mardan, 23200 Pakistan
In this paper, we investigated magnetohydrodynamic (MHD) thin film flow of an Oldroyd-B fluid in the presence of heat transfer with effect of viscous dissipation over an oscillating vertical belt. The fluid is assumed to be unsteady, and the basic governing equations are modeled in the form of nonlinear coupled partial differential equations with pertinent initial and boundary conditions. For the analytical solutions of the problem we use the optimal homotopy asymptotic method (OHAM). For comprehension, the physical presentation of such modeled parameters as the Prandtl number Pr, Brinkman number Br, time retardation parameter a, time relaxation parameter β, gravitational parameter St, and magnetic parameter M are plotted graphically and discussed. An increase in M increases the velocity and temperature distribution, the boundary-layer thickness decreases by increasing the Prandtl number, and the velocity decreases by increasing the gravitational parameter.
ENHANCING THE THERMAL PERFORMANCE OF A MICRO FINNED TUBE WITH TiO2–WATER NANOFLUIDS USING TWISTED TAPE INSERTS
851-863
D.
Mageshbabu
Department of Mechanical Engineering, S.A. Engineering College, Chennai-600077, Tamil Nadu,
India
A. E.
Kabeel
Mechanical Power Engineering Department, Faculty of Engineering, Tanta University, Egypt
Ravishankar
Sathyamurthy
Mechanical Power Engineering Department, Faculty of Engineering, Mechanical Power
Engineering Department, Tanta, Egypt; Department of Automobile Engineering, Hindustan Institute of Technology and Science,
Chennai, 603103, Tamil Nadu, India
S. A.
El-Agouz
Mechanical Power Engineering Department, Faculty of Engineering, Tanta University, Egypt
Ali J.
Chamkha
Department of Mechanical Engineering, Prince Sultan Endowment for Energy and
Environment, Prince Mohammad Bin Fahd University, Al-Khobar 31952, Kingdom of Saudi
Arabia; RAK Research and Innovation Center, American University of Ras Al Khaimah, United Arab Emirates, 10021
M. S.
Girĳa
Department of Computer Science and Engineering, Jeppiaar Engineering College, Chennai-600119,
Tamil Nadu, India
B.
Madhu
Department of Mechanical Engineering, Velammal Institute of Technology, Chennai, Tamil Nadu,
India
This paper investigates the heat transfer characteristics and friction factor of finned microtube fitted with twisted tape inserts. Results show that the performance of the finned microtube with nanofluid depends on concentration of nanoparticles, pitch ratio, and the type of the pitch used. With increase in the concentration of nanoparticle with the base fluid the viscosity of the nanofluid increased by 30% compared to the fluid with concentration of 0.05%. The increase in the concentration of nanoparticles leads to increased pressure drop and pumping power. For the Reynolds number Re = 2000, the maximum performance ratio is found to be 1.5, 2.05, 2.1, and 2 for 0, 0.05, 0.1, and 0.2% concentration ratio, respectively. Similarly, with increase in the Reynolds number from 2000 to 10,000 the performance ratio decreases. Moreover, the results of performance ratio revealed that the use of a nanofluid have performance more than unity. Similarly, the performance of finned microtube heat exchanger is higher in the case of twist ratio (LR-Y = 6) and concentration ratio (φ = 0.2%), as the turbulence inside the tube is greatly influenced by the boundary layer separation by the inserts for enhanced friction ratio (f/fp) and Nusselt number ratio (Nu/Nup) compared to a smooth plain tube.
OPTIMIZATION OF THERMAL AND SOLUTAL STRATIFICATION IN SIMULATION OF WILLIAMSON FLUID WITH ENTROPY GENERATION AND ACTIVATION ENERGY
865-882
Muhammad Ijaz
Khan
Department of Mathematics, Quaid-I-Azam University, Islamabad 44000, Pakistan
Sumaira
Qayyum
Department of Mathematics, Quaid-I-Azam University, Islamabad 44000, Pakistan
Tufail A.
Khan
Department of Basic Sciences, University of Engineering & Technology, Peshawar, Pakistan
M. Imran
Khan
Heriot Watt University, Edinburgh Campus, Edinburgh EH14 4AS, United Kingdom
Tasawar
Hayat
Department of Mathematics, Quaid-I-Azam University 45320, Islamabad 44000, Pakistan; Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Faculty of Science,
King Abdulaziz University, P.O. Box 80257, Jeddah 21589, Saudi Arabia
Ikram
Ullah
Department of Mathematics, Quaid-I-Azam University, Islamabad 44000, Pakistan
Ahmed
Alsaedi
Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Department of Mathematics, Faculty of Science, King Abdulaziz University, P. O. Box. 80257,
Jeddah 21589, Saudi Arabia
A numerical study is accomplished to examine the irreversibility (entropy generation optimization) of the behavior of Williamson fluid flow with Arrhenius activation energy. Viscous dissipation, thermal and solutal stratification, nonlinear mixed convection, activation energy, and thermal radiation are considered in mathematical modeling. The main attention here is paid to computing the total entropy generation rate. It is observed that influential variable parameters like the Brinkman number, temperature difference parameter, concentration difference parameter, and diffusion parameter have a major impact on entropy generation and Bejan number. Nondimensional irreversibility is defined to fully assess the comprehensive impacts of heat flux and mass flow rate. The obtained result shows that the entropy generation rate strongly depends on the mass flow rate and heat flux. Furthermore, the velocity and temperature gradients are numerically computed and discussed.
NUMERICAL AND EXPERIMENTAL STUDY OF THE SOLAR CHIMNEY WITH DIVERGENT COLLECTOR
883-898
Abdallah
Bouabidi
Laboratory of Electro-Mechanic Systems, National Engineering School of Sfax, University of Sfax,
B.P. 1173, km 3.5 Soukra, 3038 Sfax, Tunisia
Haythem
Nasraoui
Laboratory of Electro-Mechanic Systems, National Engineering School of Sfax, University of Sfax,
B.P. 1173, km 3.5 Soukra, 3038 Sfax, Tunisia
Ahmed
Ayadi
Laboratory of Electro-Mechanic Systems, National Engineering School of Sfax, University of Sfax,
B.P. 1173, km 3.5 Soukra, 3038 Sfax, Tunisia
Zied
Driss
Laboratory of Electro-mechanic Systems, National Engineering School of Sfax PB1173, Soukra 3038, Sfax, Tunisia
Mohamed Salah
Abid
Laboratory of Electro-mechanic Systems, National Engineering School of Sfax PB1173, Soukra 3038, Sfax, Tunisia
The aim of this work is to study and investigate the solar chimney power plant with divergent collector output. Interest is being shown in the standard solar chimney without collector divergence and in three solar chimneys with three divergence values. The computer simulation was achieved by using the ANSYS Fluent software. The flow characteristics inside all the solar chimney compounds were presented and discussed. An experimental setup of solar chimney was developed to carry out measurements. The results showed that the collector divergence affects the air flow behavior inside the chimney and, consequently, the system performance. The static pressure in the chimney inlet was affected by the collector slope and, consequently, by the velocity value. A comparison between the numerical results and experimental measurements showed good agreement.
INFLUENCE OF LONGITUDINAL HEAT CONDUCTION EFFECTS IN A HEAT SINK OVER THE THERMAL CREEP IN A MICROCHANNEL: CONJUGATE HEAT TRANSFER MECHANISM
899-920
I. G.
Monsivais
Departamento de Termofluidos, Facultad de Ingenieria, UNAM. México, D.F. 04510, Mexico
J. J.
Lizardi
Colegio de Ciencia y Tecnologia, Universidad Autónoma de la Ciudad de México, Campus San
Lorenzo Tezonco, Calle Prolongación San Isidro 151, 09790, Mexico
Federico
Mendez
Departamento de Termofluidos, Facultad de Ingenieria, UNAM. México, D.F. 04510, Mexico
In this work, we use asymptotic and numerical techniques to analyze the conjugated heat transfer between a rarified
gas flow and the lower wall of a thin horizontal microchannel exposed to a uniform heat flux, when the laminar motion of the gas is only caused by the thermal creep or transpiration effect on the lower wall of the microchannel. The surface temperature of the lower wall is unknown and must be determined as a part of the problem. Therefore, we can assume that the lower face of this heat sink with finite values of the thermal conductivity and thickness is exposed to a uniform heat flux, while the upper wall of the microchannel is subjected to a prescribed thermal boundary condition. The resulting governing equations are written in dimensionless form, assuming that the Reynolds number associated with the characteristic velocity of the thermal creep and the aspect ratio of the microchannel, are both very small. The velocity and temperature profiles of the gas phase and the temperature profile of the solid wall are determined as functions of the involved dimensionless parameters, and the predictions clearly confirm the influence of the conjugate thermal mechanism.