Begell House Inc.
Heat Transfer Research
HTR
1064-2285
49
14
2018
EXPERIMENTAL DETERMINATION OF EMISSIVITY MODELS OF STEEL 201 AT 800−1100 K DURING OXIDE LAYER GROWTH
1323-1337
Wenjie
Zhu
College of Physics and Material Science, Henan Normal University, Xinxiang 453007, China
Deheng
Shi
College of Physics and Material Science, Henan Normal University, Xinxiang 453007, China
Zunlue
Zhu
College of Physics and Material Science, Henan Normal University, Xinxiang 453007, China
Jinfeng
Sun
College of Physics and Material Science, Henan Normal University, Xinxiang 453007, China
This work investigated the variation in the spectral emissivity with wavelength and temperature during the growth of
an oxide layer on the surface of steel 201 specimens. The measurements were performed at the wavelengths 1.4, 1.5, 1.6,
1.7, 1.8, 1.9, 2.0, and 2.1 µm over a temperature range from 800 to 1100 K in steps of 20 K. During the experiment, the
specimen was kept at a certain temperature in air for 6 h. Multispectral radiation thermometry was used to measure the
radiances stemming from the specimen surface and the spectral emissivity at a certain temperature. Two thermocouples
were symmetrically welded on the front surface of specimens near the measuring area for accurate monitoring of the surface
temperature. The average of their readings was regarded as the true temperature of specimens. With the spectral emissivity
measured, the variation of it with wavelength was studied at different temperatures and at different heating times. Similar variation in the spectral emissivity with wavelength at different temperatures and different heating times showed that it was governed by the same emissivity models. Ten emissivity models were ex− the thermometry. The experiments proved that both the five-parameter LLWE and LWE models can generate the best overall temperature predictions during 6 h of heating.
As a conclusion, we confirm that the five-parameter LLWE and LWE models could be employed to accurately predict the
surface temperature of steel 201 over the present wavelength and temperature ranges regardless of surface oxidization.
A NEW APPROACH TO NUMERICAL INVESTIGATION OF GFX AND POWER-PIPE DRAIN WATER HEAT RECOVERY (DWHR) SYSTEMS IN BUILDINGS
1339-1352
Pooria
Akbarzadeh
Department of Mechanical and Mechatronics Engineering, Shahrood University of Technology,
Shahrood P.Box: 3619995161, Iran
A. Abbas
Nejad
Department of Mechanical and Mechatronics Engineering, Shahrood University of Technology,
Shahrood P.Box: 3619995161, Iran
F.
Movahed
Department of Mechanical and Mechatronics Engineering, Shahrood University of Technology,
Shahrood P.Box: 3619995161, Iran
S.
Zolfaghari
Department of Mechanical and Mechatronics Engineering, Shahrood University of Technology,
Shahrood P.Box: 3619995161, Iran
In this study, a new computational approach is introduced to numerically investigate the thermal characteristics of the
vertical GFX and Power-Pipe Drain Water Heat Recovery (DWHR) systems. In a DWHR exchanger, drained warm water
from showering passes through a pipe, and it transfers a part of its thermal energy to cold water flowing through a pipe coiled around the vertical one. This computational approach includes three steps: (i) fluid film thickness measurement in the vertical tube using 2D numerical and analytical calculations; (ii) 3D thermal modeling of the heat exchanger (two rings of the GFX exchanger and one ring of the power-pipe exchanger), and finally (iii) generalization of the results into more numbers of rings by using heat exchanger relations. The numerical approaches are based on the finite volume method. This methodology is validated by the experimental works of others and also by using the grid independence study. The main outputs and results include pressure drop in the coiled pipe, thermal effectiveness, and recovered heat energy. One of the
important conclusions is that an increase in flow rate decreases the exchanger effectiveness.
DRYING KINETICS OF HOT-AIR DRIED BEEF MEAT: APPLICATION OF MATHEMATICAL MODELS, ENERGY CONSUMPTION, AND COLOR CHARACTERISTICS
1353-1366
Osman
Ismail
Department of Chemical Engineering, Faculty of Chemical and Metallurgical Engineering, Yildiz
Technical University, Davutpasa Campus, 34210 Istanbul, Turkey
Ozlem Gökce
Kocabay
Department of Chemical Engineering, Faculty of Chemical and Metallurgical Engineering, Yildiz
Technical University, Davutpasa Campus, 34210 Istanbul, Turkey; T.R. Ministry of Culture and Tourism, Directorate of Central and Laboratory for Restoration and Conservation, Istanbul, Turkey
In this study, the effect of different drying conditions on the thermal and physical properties of beef meat samples was
studied. The drying experiments were carried out at three different temperatures (40, 50, and 60°C) with a constant air flow rate of 1 m/s. Moisture transfer from beef meat samples was described by applying Fick's diffusion model. Effective moisture diffusivity of beef meat samples during experiments was achieved to be (4.56–11.98) × 10–10 m2/s. The activation energy of the samples was found as 42.93 kJ/mol. The results showed that the Alibas model had the best performance in predicting the moisture ratio. The highest and lowest values of energy consumption were calculated to be equal to 10.83 and 5.32 kWh, respectively. After drying, the total color difference increased. The changes in the sample surface color after drying were also measured, and the total color change ΔE of the samples at all temperatures and after each drying process was greater than 11.
RADIATION-AUGMENTED RIGID POLYURETHANE FOAM FIRE SUPPRESSION USING A WATER SPRAY
1367-1383
Hengze
Zhao
College of Mining Engineering, North China University of Science and Technology, Tangshan,
Hebei 063210, P.R. China
Ye
Li
College of Mining Engineering, North China University of Science and Technology, Tangshan,
Hebei 063210, P.R. China
Qixing
Zhang
State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei, Anhui
230026, P.R. China
Jianfei
Luo
State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei, Anhui
230026, P.R. China
Gao
Xu
State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei, Anhui
230026, P.R. China
Yongming
Zhang
State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei, Anhui, 23 0026, China
A series of laboratory-scale experimental tests were carried out to investigate the extinguishment of radiation-augmented
vertical Rigid Polyurethane (RPU) fires by a water spray. The experimental work included freeburn and suppression tests under various conditions of external radiation and water application rates. The critical RPU burning rates for two extreme situations were simulated with various water application rates used in the experiment. The simulation data are consistent with experimental results. Both the freeburn and fire suppression experimental data indicate a linear dependence of the burning rate on the external radiant flux. The relationships between three ratios and proper dimensionless indices are discussed. The results show that the external radiant flux plays a more important role than the water application rate for fire suppression. Note that the current experiment was conducted at a significantly reduced scale compared to real building facade. Nevertheless, it still has a guiding significance for fire suppression.
NUMERICAL SIMULATION OF DOUBLE-DIFFUSIVE MIXED CONVECTION IN A HORIZONTAL ANNULUS UNDER TANGENTIAL MAGNETIC FIELD, WITH A ROTATING OUTER CYLINDER
1385-1402
Mehdi
Bidabadi
Department of Mechanical Engineering, Department of Energy Conversion, Combustion and
Heat Transfer Modeling Laboratory, Iran University of Science and Technology, Tehran, Iran
Vahid
Bordbar
Department of Mechanical Engineering, Department of Energy Conversion, Combustion and
Heat Transfer Modeling Laboratory, Iran University of Science and Technology, Tehran, Iran
Alireza Khoeini
Poorfar
Department of Mechanical Engineering, Department of Energy Conversion, Combustion and
Heat Transfer Modeling Laboratory, Iran University of Science and Technology, Tehran, Iran
Bengt
Sunden
Division of Heat Transfer, Department of Energy Sciences, Lund University, P.O. Box 118,
SE-22100, Lund, Sweden
Goodarz
Ahmadi
Department of Mechanical and Aeronautical Engineering, Clarkson University, Potsdam, NY,
13699, USA
Double-diffusive mixed convection in a horizontal annulus under combined buoyancy effect of temperature and concentration gradients and in the presence of a tangential magnetic field is studied numerically. Different constant temperatures and concentrations are imposed along the inner cylinder and the outer cylinder, and a steady-state laminar condition is considered. The governing equations consisting of continuity, momentum, energy, and spices transfer equations in dimensionless form are solved using an in-house Fortran code based on the Patankar-Spalding SIMPLE algorithm. The results are reported in terms of streamlines, isotherms, and isoconcentrations for different values of governing parameters such as the Reynolds number, Rayleigh number, Hartmann number, and the Lewis number. In addition, the results for heat transfer rate and mass transfer rate are presented in terms of local and average Nusselt numbers and local and average Sherwood numbers, respectively, for various parametric conditions. Throughout the present study, the Prandtl number and buoyancy ratio are considered constant, 0.71 and -1, respectively, while the other parameters vary in the following intervals: 5 × 103 ≤ Ra ≤ 5 × 104, 10 ≤ Re ≤ 200, 0 ≤ Ha ≤ 200, and 0.01 ≤ Le ≤ 5
ANALYSIS OF HEAT AND MASS TRANSFER IN UNSTEADY NANOFLUID FLOW BETWEEN MOVING DISKS WITH CHEMICAL REACTION — A NUMERICAL STUDY
1403-1417
Muhammad Farooq
Iqbal
Centre for Advanced Studies in Pure and Applied Mathematics, (CASPAM), Bahauddin
Zakariya University, (BZU), Multan, 608000 Pakistan
Shahzad
Ahmad
Center for Advanced Studies in Pure and Applied Mathematics, Bahauddin Zakariya University,
Multan, Pakistan
Kashif
Ali
Department of Basic Sciences and Humanities, Muhammad Nawaz Sharif University of
Engineering and Technology, Multan, Pakistan
Muhammad Zubair
Akbar
Center for Advanced Studies in Pure and Applied Mathematics, Bahauddin Zakariya University,
Multan, Pakistan
Muhammad
Ashraf
Center for Advanced Studies in Pure and Applied Mathematics, Bahauddin Zakariya University,
Multan, Pakistan
The study is devoted to the analysis of heat and mass transfer in an unsteady hydromagnetic viscous incompressible water-based nanofluid flow between two orthogonally moving porous coaxial disks with suction. Similarity transformation is used to convert the governing partial differential equations into a system of coupled nonlinear ODEs which are then solved by employing an algorithm based on the quasi-linearization and the finite difference discretization. Viscous dissipation and the chemical reaction effects have also been taken into account. Influence of the governing parameters on the heat and mass transfer characteristics of the problem has been presented through tables and graphs. The outcome of the investigation may be valuable for the electronic industry in maintaining the electronic components under effective and safe operational conditions.