Begell House Inc.
Heat Transfer Research
HTR
1064-2285
46
9
2015
NUMERICAL SIMULATION OF PROCESSES OCCURRING IN A STEAM−WATER MIXING HEATER
785-794
10.1615/HeatTransRes.2015006021
Xingfang
Zhang
College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024, China
Junhui
Zhang
CNNC Xinneng Nuclear Engineering Co., Ltd., Taiyuan 030012, China
Xinghui
Zhang
College of Environmental Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, China
Sheng
Wu
Taiyuan Boiler Group Co., Ltd., Taiyuan 030021, China
Jian
Liu
College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024, China
Xiujuan
Zhang
Taiyuan Boiler Group Co., Ltd., Taiyuan 030021, China
steam-water mixing heater
two-phase flow
direct contact
numerical simulation
Numerical simulations were conducted to examine the heat transfer processes occurring in a steam−water mixing heater that has different inlet steam pressures. The FLUENT, which is a commercial computational fluid dynamics software, and the volume of fluid multiphase flow model were used to simulate the two-phase flow in a steam−water mixing heater. The condensation heat transfer source term and the mass transfer source term, which were obtained by calculating the phase interface temperature gradient, were integrated in the simulation. The simulation results coincide with experimental data and show that the exit speed, temperature, and the nondimensional length of the steam plume increase with increasing inlet steam pressure.
NUMERICAL STUDY OF THE HYDROTHERMAL BEHAVIOR AND EXERGY DESTRUCTION OF MAGNETIC NANOFLUID IN CURVED RECTANGULAR MICROCHANNELS
795-818
10.1615/HeatTransRes.2015007542
Mousa
Mohammadpourfard
University of Tabriz
Sajjad Ahangar
Zonouzi
Department of Mechanical Engineering, Razi University Kermanshah, Iran
F.
Mohseni
Institute for Building Materials, Computational Physics for Engineering Materials, ETH Zurich, Switzerland
ferrofluid
microchannel
entropy generation
mixture model
nonuniform magnetic field
This paper presents a numerical investigation of entropy generation and exergy destruction of a magnetic nanofluid in curved rectangular microchannels. The microchannels with different aspect ratios and curvatures have been studied using two-phase mixture model and control volume technique. Additionally the effect of a nonuniform transverse magnetic field on exergy destruction has been investigated. Based on the results obtained, it is found that the aspect ratio of the microchannels plays a considerable role in the entropy generation for the same length of microchannels. The total entropy generation also decreases with increasing curvature of the microchannels. It has also been shown that adding Fe3O4 nanoparticles to the base fluid decreases the entropy generation due to heat transfer irreversibilities. Furthermore, the total entropy generation decreases considerably on applying a nonuniform transverse magnetic field.
NUMERICAL STUDY OF HEAT TRANSFER ENHANCEMENT AND FLOW CHARACTERISTICS OF THREE-DIMENSIONAL PLATE FIN HEAT EXCHANGERS
819-837
10.1615/HeatTransRes.2015007449
Ertan
Buyruk
Cumhuriyet University, Engineering Faculty, Mechanical Engineering Department, 58140, Sivas/Turkey
KORAY
KARABULUT
Sivas Cumhuriyet University Sivas Vocational High School
plate heat exchanger
numerical heat transfer
fin
The present study is aimed at numerical investigation, by using conjugated heat transfer approach, of the effect of different types of rectangular fins (outer zigzag-inner zigzag-flat-outer zigzag (type B) and inner zigzag-flat-inner zigzag (type C)), which are mounted on a flat plate channel having three-dimensional rectangular cross section, on heat transfer enhancement in a plate fin heat exchanger. The numerical computations are performed by solving a steady, three-dimensional Navier−Stokes equation and an energy equation by using the FLUENT software program. Air is taken as a working fluid. The study is carried out at Re = 400, at the inlet temperatures and velocities of cold and hot air fixed at 300 K, 600 K and 1.338 m/s, 0.69 m/s, respectively. The results show that the heat transfer is increased by 9 percent at the exit of channel with the fin type C, when compared to a channel without a fin with counterflow. The effect exerted on heat transfer enhancement by different values of the Reynolds number and fin heights, and also by temperature distributions on the hot and cold fluid sides of the channel surface are investigated in the case of parallel flow and counterflow.
NATURAL CONVECTION HEAT TRANSFER INSIDE AN INCLINED SOLAR COLLECTOR WITH A V-CORRUGATED ABSORBER
839-859
10.1615/HeatTransRes.2015007200
Meisam
Habibi Matin
School of Mechanical Engineering, Amirkabir University of Technology (Tehran Polytechnic), 424 Hafez Avenue, Tehran, Iran
Reza
Hosseini
School of Mechanical Engineering, Amirkabir University of Technology (Tehran Polytechnic), 424 Hafez Avenue, Tehran, Iran
H.
Naderan
School of Mechanical Engineering, Amirkabir University of Technology (Tehran Polytechnic), 424 Hafez Avenue, Tehran, Iran
natural convection
numerical study
solar collector
V-corrugated absorber
The present article deals with the numerical study of two-dimensional steady-state laminar natural convection heat transfer inside an inclined solar collector with a V-corrugated absorber (hot wall) and a flat cover (cold wall). The Rayleigh number is considered to be lower than 5 × 104 to satisfy the assumption of laminar region for the heat transfer problem. The governing continuity, momentum, and energy equations are converted to a quadrant domain by means of conformal mapping. The finite volume technique has been used for discretization of the equations using a staggered grid, and finally the SIMPLE algorithm is utilized to solve them. The effects of parameters such as the inclination angle, aspect ratio, wave parameter, and of the Rayleigh number on the local Nusselt and the mean Nusselt number have been considered. Patterns of heat and fluid flows are also simulated. The results show that there are conditions in which the mean Nusselt number could be optimized.
ULTRAFAST LASER PULSE TRAIN RADIATION TRANSFER IN A SCATTERING-ABSORBING 3D MEDIUM WITH AN INHOMOGENEITY
861-879
10.1615/HeatTransRes.2015012439
Masato
Akamatsu
Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata 992-8510, Japan
Zhixiong
Guo
Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New
Jersey, Piscataway, NJ 08854, USA
discrete-ordinates method
superposition
short-pulse train
radiative transfer
inhomogeneity
heterogeneous medium
In this study, we continue investigating the ultrafast laser pulse train irradiation of inhomogeneous media, focusing on different degrees of inhomogeneity in a base scattering-absorbing medium. We used the transient discrete-ordinates method to acquire basic solutions of radiation transfer in the 3D inhomogeneous media subjected to a unit step pulse and then adopted the Duhamel's superposition theorem to construct series solutions subjected to a pulse of different pulse widths or a pulse train consisting of many such pulses. The effects of scattering albedo, inhomogeneity size and location, pulse width and interval, and detector position on the temporal reflectance and transmittance signals are characterized and revealed.