Begell House Inc.
Heat Transfer Research
HTR
1064-2285
45
1
2014
ANALYSIS OF THERMALLY DEVELOPING LAMINAR CONVECTION IN THE FINNED DOUBLE-PIPE HEAT EXCHANGER
1-21
Mazhar
Iqbal
School of Natural Sciences, National University of Sciences and Technology, Islamabad, Pakistan
K. S.
Syed
CASPAM, B.Z.U, Multan, Pakistan
In this work we have carried out the study of convective heat transfer of hydrodynamically fully developed but thermally developing laminar flow in the entrance region of a finned double-pipe heat exchanger. We have taken one-dimensional temperature profile in the radial direction of the fins under the thin fin assumption. It is shown that the heat transfer rate in the thermal entrance region is much higher than in the fully developed region, and the assumption of infinite fin conductivity loses validity in the entrance region.
EFFECT OF RADIATION HEAT TRANSFER ON HCCI MULTIZONE COMBUSTION
23-41
Aidin
Akbarzadeh
Department of Mechanical Engineering, University of Tabriz, Tabriz, Iran
Faramarz
Talati
Department of Mechanical Engineering, University of Tabriz, Tabriz, Iran
Amin
Paykani
Department of Mechanical Engineering, Parand Branch, Islamic Azad University, Parand, Iran
During past two decades, combustion of the Homogeneous Charge Compression Ignition (HCCI) type has shown itself as a well-known and applicable method for several types of internal combustion engines, whether stationary or mobile. This work is intended to develop a mathematical model in order to analyze radiation heat transfer in HCCI engines. In the current study, in order to consider in-cylinder charge heterogeneity, multizone modeling is adopted. Then, suitable equations of emissivity and absorption coefficients of the in-cylinder gaseous species are used, and applied to the equations of radiation heat transfer between the zones, and eventually are converted to the FORTRAN code. The in-house code is applied to a detailed code of HCCI combustion and its results are obtained from three different cases of engine operating conditions. For validating the numerical results, experimentally measured pressure data is used showing very good agreement. Moreover, results obtained by using the model which took into account radiation are compared with results of no-radiation model.
GLOBAL STABILITY FOR THERMAL CONVECTION IN A COUPLE STRESS FLUID: RIGID BOUNDARIES
43-57
Sunil
Department of Mathematics, National Institute of Technology, Hamirpur, (H.P.) 177005, India
Reeta
Devi
Department of Mathematics, National Institute of Technology, Hamirpur, (H.P.) − 177 005, India
We show that the global nonlinear stability threshold for convection in a couple-stress fluid (and for a rotating couple-stress fluid) is exactly the same as the linear instability boundary. This optimal result is important, because it shows that the linearized instability theory has captured completely the physics of the onset of convection. The eigenvalue problems for the rigid−rigid (RR) conducting boundaries are solved by the single-term Galerkin method. The effect of the couple-stress parameter F and rotation parameter TA on the onset of convection is also analyzed.
FLOW INTO VERTICAL CHANNELS IN THE PRESENCE OF BLOCKS: HEAT TRANSFER CHARACTERISTICS
59-73
S. Z.
Shuja
Mechanical Engineering Department, KFUPM Box 1913, Dhahran 31261, Saudi Arabia
Bekir S.
Yilbas
Mechanical Engineering Department, KFUPM Box 1913, Dhahran 31261, Saudi Arabia
Heat transfer characteristics in a vertical channel in the presence of heat releasing and nonreleasing blocks are investigated. The influence of the spacing between the blocks on the heat transfer characteristics is examined. The blocks are made of the same material, and the location of the heat releasing block is fixed. The temperature and flow fields in the channel are simulated using the control volume approach. It is found that the thermally induced convective current emergent from the first block modifies the flow and temperature fields in the neighborhood of the second block. In this case, the Nusselt number increases along the side walls of the second block in the case of a small spacing, and an increasing spacing results in a reduced Nusselt number at the second block surfaces.
MIXED CONVECTION HEAT TRANSFER IN A DOUBLE LID-DRIVEN INCLINED SQUARE ENCLOSURE SUBJECTED TO Cu−WATER NANOFLUID WITH PARTICLE DIAMETER OF 90 nm
75-95
Mohammad Reza
Heydari
Parand Branch, Islamic Azad University, Tehran, Iran
Mohammad
Hemmat Esfe
Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran
Mohammad Hadi
Hajmohammad
Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Isfahan, Iran
Mohammad
Akbari
Department of Mechanical Engineering, Semnan University, Semnan, Iran
Seyed Sadegh Mirtalebi
Esforjani
Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Isfahan, Iran
In this article, mixed convection flow in a two-sided lid-driven cavity at different inclination angles filled with Cu−water nanofluid (with diameter of 90 nm) is studied numerically using the finite volume method. For different values of solid volume fraction of nanoparticles, flow is induced by the top and right-hand sidewalls sliding at constant speed. The left-hand sidewall is kept constant at higher temperature (Th), while the right moving wall is maintained at a lower temperature (Tc), thereby introducing natural convection. In this study, bottom and top walls were assumed isolated; Richardson number ranged from 0.001 to 10, nanoparticles solid volume fraction (φ) up to 0.06 were investigated, and cavity inclination angle from 0° to 90° was considered and the Grashof number was set to 104. The influence of inclination angle and φ of the nanofluids on hydrodynamic and thermal characteristics is discussed. The results indicated that increase in φ for a constant Ri enhances heat transfer. Also, heat transfer was increased as Ri was decreased for a particular φ. Moreover, where natural convection is dominant (i.e., higher Ri), the flow form seems to be influenced more by φ.