Begell House Inc.
Heat Transfer Research
HTR
1064-2285
45
4
2014
DOUBLE-DIFFUSIVE NATURAL CONVECTIVE PERISTALTIC FLOW OF A JEFFREY NANOFLUID IN A POROUS CHANNEL
293-307
Noreen Sher
Akbar
DBS&H, CEME, National University of Sciences and Technology, Islamabad, Pakistan
Double-diffusive natural convective peristaltic flow of a Jeffrey nanofluid in a two-dimensional porous asymmetric channel has been studied. Using long wavelength approximation with low Reynolds number, the problem has been simplified, and using dynamic boundary conditions, numerical solutions have been derived for stream function, pressure rise, velocity profile, temperature, solutal concentration, and nanoparticle fraction. Numerical solutions are presented graphically for the involved fluid parameter.
MIXED CONVECTION FLOW AND HEAT TRANSFER IN A VENTILATED INCLINED CAVITY CONTAINING HOT OBSTACLES SUBJECTED TO A NANOFLUID
309-338
Mohammad
Hemmat Esfe
Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran
Sina
Niazi
Department of Mechanical Engineering, Faculty of Engineering, University of Kashan, Kashan, Iran
Seyed Sadegh Mirtalebi
Esforjani
Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Isfahan, Iran
Mohammad
Akbari
Department of Mechanical Engineering, Semnan University, Semnan, Iran
The present study focuses on the problem of mixed convection fluid flow and heat transfer of nanofluid in a ventilated square cavity. The cavity contains two heated blocks subjected to external Al2O3−water (with particle diameter of 47 nm)nanofluid, while temperature and nanoparticle concentration are dependent on thermal conductivity and effective viscosity insidea square cavity. The governing equations have been solved utilizing the finite volume method, while the SIMPLER algorithm is used to couple velocity and pressure fields. The natural convection effect is obtained by heating from the blocks on the bottom wall and cooling from the inlet flow. Using the developed code, the effect of Richardson number, the aspect ratio of hot blocks, solid volume fraction, and cavity inclination angles on the thermal behavior and fluid flow inside the cavity are studied. The study has been executed for the Richardson number in the range of 0.1 ≤ Ri ≤ 10, solid volume fraction 0 ≤ φ ≤ 0.06, aspect ratio 0.5 ≤ AR ≤ 1, and cavity inclination angles between 0° and 90°.The obtained results are presented in the form of streamline and isotherm counter and Nusselt diagrams. It was observed from the results that for both obstacles and in all ranges of the parameters in this study, adding nanoparticles to the base fluid or increasing the volume fraction of the nanoparticles causes the Nusselt number increases. Also, the rate of heat transfer increases when the Reynolds number increases.
EFFECTS OF MATERIAL SELECTION ON THE RADIATION FLUX OF A TUBE RECEIVER IN A DISH SOLAR SYSTEM
339-347
Mao
Qianjun
Wuhan University of Science and Technology
Ming
Xie
School of Energy Science and Engineering, Harbin Institute of Technology, 92 West Dazhi Street,
Harbin 150001, P.R. China
Heping
Tan
Key Laboratory of Aerospace Thermophysics of MIIT, School of Energy Science of Engineering, Harbin Institute of Technology, Harbin 150001, China
A solar receiver plays an important role in the performance of a solar dish electric generator. Its radiation flux can directly affect the efficiency of the whole solar energy system. In this article, the distribution of radiation flux inside a tube receiver made of five materials is simulated successfully using a Monte Carlo ray-tracing method. The mathematical model of the radiation flux based on a Monte Carlo ray-tracing method is developed in this article, and the computer code for the method is written in FORTRAN language in-house. It is evident that the radiation flux distribution inside the tube receiver is highly nonuniform. The effects of five materials on the radiation flux inside the tube receiver have been investigated, among which steel with a black paint achieves the maximum radiation flux. The results show that the radiation flux is almost negligible up to the receiver height of 80 mm, then increases sharply to its maximum at about 130 mm, and finally decreases at the height of 260 mm. The results also indicate that the maximum radiation flux occurs at the position of 130 mm for all five materials.
FLOOR SHAPE EFFECTS ON HEAT LOSSES TO THE GROUND
349-360
Marco
Spiga
Department of Industrial Engineering, University of Parma, 43124 Parma (PR), Italy
Pamela
Vocale
Univeristy of Parma
In this paper, the effect of the floor shape on the steady-state heat flow to the ground of an insulated slab on the ground floor is investigated. A rectangular floor, a square one, and L- and H-shaped floors are considered. The thermal processes in the ground are analyzed by means of a finite element code, validated in accordance with the requirements of International Standard ISO 10211. The results of numerical analysis are compared with the results obtained by the International Standard method ISO 13370. The results show that the heat losses to the ground are significantly influenced by the floor shape: ranging from an H-shaped floor to a square one the steady-state ground global heat transfer coefficient decreases by about 22%. The analysis also highlights that the methodology provided by the International Standard overestimates the losses compared to numerical calculations.
ANALYSIS OF LAMINAR MIXED CONVECTION IN AN INCLINED SQUARE LID-DRIVEN CAVITY WITH A NANOFLUID BY USING AN ARTIFICIAL NEURAL NETWORK
361-390
M. R.
Faridzadeh
Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Najafabad,
Iran
Davood Semiromi
Toghraie
Department of Mechanical Engineering, Khomeinishahr Branch, Islamic Azad University,
Khomeinishahr, Iran
Amirhossein
Niroomand
Department of Mechanical Engineering, Kashan University, Kashan, Isfahan, Iran
This study has focused on laminar mixed convection in an inclined square ventilated lid-driven cavity filled with a copper−water nanofluid. The governing equations in the two-dimensional space are discretized by using the finite volume method with the SIMPLER algorithm. The effects of independent parameters, including the Richardson number, Reynolds number, inclination angle, and the solid volume fraction of nanoparticles, on the streamlines, isotherm lines, and the average Nusselt number along the heat source have been studied. It is found that both the inclination angle and solid volume fraction, especially the second one, have remarkable effects on the fluid flow and heat transfer characteristics in the cavity. Artificial neural networks (ANN) used to extract a relation involve independent parameters for calculating the Nusselt number. The back propagation-learning algorithm with the tangent sigmoid transfer function is used to train the ANN. Finally, analytical relations for the nanofluid mixed convection in a lid-driven cavity are derived from the available ANN. It is found that the coefficient of multiple determinations (R2) between the real values and ANN results is equal to 0.9999, the maximum error being less than 0.5829 and the mean square error being equal to 5.37 × 10−5.