Enhancement of Temperature Blending in Convective Heat Transfer by Motionless Inserts With Variable Segment Length

2010 ◽  
Vol 2 (3) ◽  
Author(s):  
Ramin K. Rahmani ◽  
Anahita Ayasoufi ◽  
Emad Y. Tanbour ◽  
Hosein Molavi
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Convective Heat Transfer ◽  
Turbulent Flows ◽  
Convective Heat ◽  
Segment Length ◽  
Width Ratio ◽  
Enhance Heat Transfer ◽  
Variable Segment ◽  
The Impact

Stationary spiral inserts can effectively enhance heat transfer and temperature blending in the heat convection systems. In this paper, the impact of the segment length on the performance of a stationary insert is studied for flow Re numbers from ∼80 to ∼7900 through numerical simulation of heat transfer in streams of cold and hot gases flowing across it. The segment length to width ratio is from 1.11 to 2.33. The temperature of the studied gas is from 300 K to 1300 K. It is shown that the insert with variable segment length is more effective in temperature blending for two compressible streams compared with an insert with constant segment length, especially for low-Re-number turbulent flows.

A Numerical Study of the Convective Heat Transfer in Low-Reynolds Number Turbulent Flows in Corrugated Pipes

2012 ◽  
Author(s):  
Ramin K. Rahmani ◽  
J. Eric Arnold ◽  
George W. Kraus
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Convective Heat Transfer ◽  
Turbulent Flows ◽  
Convective Heat ◽  
Numerical Study ◽  
Internal Flow ◽  
Eddy Simulation ◽  
Corrugated Surfaces ◽  
The Impact

Enhancement of convective heat transfer in internal turbulent flows with low-to-moderate Re number has been the subject of numerous studies, due to its vast applications. Corrugated surfaces can be used as enhancement devices in the heat convection systems. An ideal corrugation, for heat transfer in internal flow applications, provides a higher heat transfer rate with minimized pressure drop. The ratio of heat flux to the pressure drop can be used to determine the efficiency of a design. Using Large-Eddy Simulation, the heat transfer in low-Re turbulent flow in a pipe is studied to investigate the impact of different corrugated profiles with similar hydraulic diameter.

Experimental Model of Temperature-Driven Nanofluid

2006 ◽  
Vol 129 (6) ◽  
pp. 697-704 ◽  
Author(s):  
A. G. Agwu Nnanna
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Small Volume ◽  
Volume Fraction ◽  
Convective Heat Transfer Coefficient ◽  
Isothermal Condition ◽  
Carrier Fluid ◽  
Small Volume Fraction ◽  
The Impact

This paper presents a systematic experimental method of studying the heat transfer behavior of buoyancy-driven nanofluids. The presence of nanoparticles in buoyancy-driven flows affects the thermophysical properties of the fluid and consequently alters the rate of heat transfer. The focus of this paper is to estimate the range of volume fractions that results in maximum thermal enhancement and the impact of volume fraction on Nusselt number. The test cell for the nanofluid is a two-dimensional rectangular enclosure with differentially heated vertical walls and adiabatic horizontal walls filled with 27 nm Al2O3–H2O nanofluid. Simulations were performed to measure the transient and steady-state thermal response of nanofluid to imposed isothermal condition. The volume fraction is varied between 0% and 8%. It is observed that the trend of the temporal and spatial evolution of temperature profile for the nanofluid mimics that of the carrier fluid. Hence, the behaviors of both fluids are similar. Results shows that for small volume fraction, 0.2⩽ϕ⩽2% the presence of the nanoparticles does not impede the free convective heat transfer, rather it augments the rate of heat transfer. However, for large volume fraction ϕ>2%, the convective heat transfer coefficient declines due to reduction in the Rayleigh number caused by increase in kinematic viscosity. Also, an empirical correlation for Nuϕ as a function of ϕ and Ra has been developed, and it is observed that the nanoparticle enhances heat transfer rate even at a small volume fraction.

scholarly journals Radiation heat transfer between human and cryocabin walls

2021 ◽  
Vol 2119 (1) ◽  
pp. 012146
Author(s):  
I A Burkov ◽  
S I Khutsieva ◽  
V A Voronov
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Human Body ◽  
Transfer Problem ◽  
Radiation Heat Transfer ◽  
Vertical Wall ◽  
Heat Transfer Problem ◽  
Radiation Heat ◽  
The Impact

Abstract The paper considers the particular case of intensive radiation heat transfer in the system consisting of a human body and cryocabin walls of cryosauna. Calculations for three models have been made, namely, human-vertical wall, which is arranged parallel to a human, human-vertical wall, which is positioned at a certain angle, and a human-cryosauna. Analytical calculations are compared with Ansys-bassed numerical calculations. The impact of radiation heat transfer in this radiation-convective heat transfer problem is estimated. Conclusions are drawn about taking into account the radiation heat transfer and a rational method for calculating this heat transfer problem.

Direct numerical simulation of convective heat transfer in a pipe with transverse vibration

2020 ◽  
Vol 148 ◽  
pp. 119048 ◽  
Author(s):  
Akihiko Mitsuishi ◽  
Masato Sakoh ◽  
Takaaki Shimura ◽  
Kaoru Iwamoto ◽  
Akira Murata ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Transverse Vibration

scholarly journals Prediction of Convective Heat Transfer Coefficient and Temperature Distribution of Air-Conditioned Spaces Using Numerical Simulation

2016 ◽  
Vol 10 (8) ◽  
pp. 12
Author(s):  
Hussein J. Akeiber ◽  
Mazlan A. Wahid ◽  
Hasanen M. Hussen ◽  
Abdulrahman Th. Mohammad ◽  
Bashar Mudhaffar Abdullah ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Transfer Coefficient ◽  
Temperature Distribution ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Solution Technique ◽  
Geometrical Parameters

Accurate and efficient modeling of convective heat transfer coefficient (CHTC) by considering the detailed room geometry and heat flux density in building is demanding for economy, environmental amiability, and user satisfaction. We report the three-dimensional finite-volume numerical simulation of internal room flow field characteristics with heated walls. Two different room geometries are chosen to determine the CHTC and temperature distribution. The conservation equations (elliptic partial differential) for the incompressible fluid flows are numerically solved using iterative method with no-slip boundary conditions to compute velocity components, pressure, temperature, turbulent kinetic energy, and dissipation rate. A line-by-line solution technique combined with a tri-diagonal matrix algorithm (TDMA) is used. The temperature field is simulated for various combinations of air-change per hour and geometrical parameters. The values of HTCs are found to enhance with increasing wall temperatures.

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