Hydrodynamic and thermal effects of drag and heat transfer coefficients under laminar unsteady flow conditions in porous media

2012 ◽  
Author(s):  
Mihir G. Pathak ◽  
Thomas Mulcahey ◽  
S. Mostafa Ghiaasiaan
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Unsteady Flow ◽  
Thermal Effects ◽  
Flow Conditions ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

scholarly journals Heat Transfer Measurements for Rotating Turbine Discs

1989 ◽  
Author(s):  
G. Qureshi ◽  
M. H. Nguyen ◽  
N. R. Saad ◽  
R. N. Tadros
Keyword(s):  
Heat Transfer ◽  
Coolant Flow ◽  
Flow Conditions ◽  
Transfer Coefficients ◽  
Rotating Disc ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Rotating Discs ◽  
Turbine Disc ◽  
State Technique

To optimise the turbine disc weight and coolant flow requirements, the aspect of improving thermal analysis was investigated. As a consequence, an experimental investigation was undertaken to measure the rates of convective heat transfer. The constant temperature steady state technique was used to determine the local and average heat transfer coefficients on the sides of rotating discs. The effects of coolant flow rates, CW (3000 ≤ CW ≤ 18600) with two types of cavity in-flow conditions and of the rotational speeds, Reθ (from 4×105 to 1.86×106) on the disc heat transfer were studied and correlations developed. For a rotating disc in confined cavities with superimposed coolant flows, Nusselt numbers were found to be higher than those for the free rotating disc without confinement.

Toward the Detailed Simulation of the Heat Transfer Processes in Unsaturated Porous Media

2009 ◽  
Author(s):  
F. A. Jafar ◽  
G. R. Thorpe ◽  
O¨. F. Turan
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Unsaturated Porous Media ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Transfer Processes ◽  
Numerical Predictions ◽  
Three Phase ◽  
Detailed Simulation ◽  
Horizontal Cylinders

Trickle bed chemical reactors and equipment used to cool horticultural produce usually involve three phase porous media. The fluid dynamics and heat transfer processes that occur in such equipment are generally quantified by means of empirical relationships between dimensionless groups. The research reported in this paper is motivated by the possibility of using detailed numerical simulations of the phenomena that occur in beds of irrigated porous media to obviate the need for empirical correlations. Numerical predictions are obtained using a CFD code (FLUENT) for 2-D configurations of three cylinders. Local and mean heat transfer coefficients around these non-contacting horizontal cylinders are calculated numerically. The present results compare well with those available in the literature. The numerical results provide an insight into the cooling mechanisms within beds of unsaturated porous media.

The Cooling Impact of a Pair of Opposed Unsteady Confined Impinging Air Jets

2005 ◽  
Author(s):  
Victor Chiriac ◽  
Jorge L. Rosales
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Unsteady Flow ◽  
Jet Flow ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Air Jets ◽  
Laminar Jets ◽  
Vortex Patterns ◽  
Two Jets

A numerical investigation was performed at two Reynolds numbers to analyze the flow-field and heat transfer characteristics for a pair of laminar jets impinging on opposite walls in a channel. The present study is a continuation of the authors’ earlier work [1] in which the jets flowing out normal to the top channel wall produce a large stagnant bubble between the two jets which greatly reduce the heat transfer removal from the lower wall. In this case, the lower Reynolds number jet flow of 300 produces a symmetric, steady flow hydrodynamic pattern with the jets being deflected laterally. By further increasing the Reynolds number to 750, a complex asymmetric and highly unsteady flow develops between the two jets due to the opposite jet flow interaction. The convective heat transfer coefficients and the unsteady flow development between the jets are studied for each case. The flow unsteadiness is also characterized by analyzing the stagnation point displacement on the channel walls. The complex vortex patterns resulting from the jet interaction at the higher Reynolds number is investigated and its impact on the chip/microelectronics component cooling is thoroughly documented.   This paper was also originally published as part of the Proceedings of the ASME 2005 Heat Transfer Summer Conference.

The Influence of the Boundary Layer State and Reynolds Number on Film Cooling and Heat Transfer on a Cooled Nozzle Guide Vane

2000 ◽  
Author(s):  
Hans Reiss ◽  
Albin Bölcs
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Film Cooling ◽  
Guide Vane ◽  
Suction Side ◽  
Flow Conditions ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nozzle Guide Vane ◽  
Nozzle Guide

Film cooling and heat transfer measurements were carried out on a cooled nozzle guide vane in a linear cascade, using a transient liquid crystal technique. Three flow conditions were realized: the nominal operating condition of the vane with an exit Reynolds number of 1.47e6, as well as two lower flow conditions: Re2L = 1.0e6 and 7.5e5. The vane model was equipped with a single row of inclined round film cooling holes with compound angle orientation on the suction side. Blowing ratios ranging form 0.3 to 1.5 were covered, all using foreign gas injection (CO2) yielding an engine-representative density ratio of 1.6. Two distinct states of the incoming boundary layer onto the injection station were compared, an undisturbed laminar boundary layer as it forms naturally on the suction side, and a fully turbulent boundary layer which was triggered with a trip wire upstream of injection. The aerodynamic flow field is characterized in terms of profile Mach number distribution, and the associated heat transfer coefficients around the uncooled airfoil are presented. Both detailed and spanwise averaged results of film cooling effectiveness and heat transfer coefficients are shown on the suction side, which indicate considerable influence of the state of the incoming boundary layer on the performance of a film cooling row. The influence of the mainstream flow condition on the film cooling behavior at constant blowing ratio is discussed for three chosen injection regimes.

An Experimental Investigation of Reflux Condensation Phenomena in Multiple U-Tubes With and Without Noncondensible Gas

2001 ◽  
Author(s):  
Moon-Hyun Chun ◽  
Kyung-Won Lee ◽  
In-Cheol Chu
Keyword(s):  
Heat Transfer ◽  
Atmospheric Condition ◽  
Flow Conditions ◽  
Transfer Coefficients ◽  
Flow Rates ◽  
Heat Transfer Coefficients ◽  
Condensation Mode ◽  
Series Of Experiments ◽  
Pure Steam ◽  
The Heat Transfer Coefficient

Abstract A series of experiments were performed to investigate the thermal-hydraulic phenomena inside U-tubes in a reflux condensation mode. A total of 512 data for local condensation heat transfer coefficients (108 for pure steam flow and 404 for steam-air flow conditions, respectively) have been obtained for various inlet flow rates of steam and air under atmospheric condition. A new correlation, which includes the effects of flow rates of steam and noncondensible gases (air) on the heat transfer coefficient and is applicable to the reflux condensation mode, has been developed using the concept of degradation factor based on the steam-air experimental results. In addition, the effects of multiple U-tubes with different lengths (i.e., two-long and two-short U-tubes) and noncondensible gases on the onset of flooding during a reflux condensation have been examined.

Forced-Convection Heat Transfer for Single and Two-Phase Helical Flow in a Solar Receiver

1986 ◽  
Vol 108 (1) ◽  
pp. 76-83 ◽  
Author(s):  
F. N. Vafaie ◽  
J. R. Dunn
Keyword(s):  
Heat Transfer ◽  
Convection Heat Transfer ◽  
Flow Conditions ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Water Steam ◽  
Heat Transfer Coefficients ◽  
Phase Water ◽  
Solar Receiver

The heat transfer characteristics of a single-tube, helically coiled receiver for a concentrating solar collector are presented. Heat transfer coefficients were measured for single and two-phase water-steam flow in a helical coil subjected to radiant heating for a range of flow conditions and radiant flux levels. Results are presented for both the local and average heat transfer coefficients in several flow regimes.

An Improved Analytical Approach to Steam Turbine Heat Transfer

2004 ◽  
Author(s):  
Howard M. Brilliant ◽  
Anil K. Tolpadi
Keyword(s):  
Heat Transfer ◽  
Steam Turbine ◽  
Steam Turbines ◽  
Flow Conditions ◽  
Transfer Coefficients ◽  
Operating Cycle ◽  
Local Flow ◽  
Heat Transfer Coefficients ◽  
Thermal Growth ◽  
Cfd Analyses

Improvements to the design of advanced steam turbines require an improved understanding of the heat transfer within the various components of the unit. Physics-based ANSYS models for typical high pressure and intermediate pressure units have been developed. The boundary conditions were derived from full-load, steady state flow analyses, steam turbine performance code outputs and computational fluid dynamics (CFD) analyses to develop normalized (non-dimensional) local flow conditions, with the normalizing parameters based on key cycle parameters. These normalized local flow conditions and cycle parameters were then used to define local transient boundary temperatures and heat transfer coefficients for input to the thermal ANSYS model. Transient analyses of components were performed. The results were compared with temperature measurements taken during the operating cycle of an operational steam turbine to validate and improve the methodology and were applied to structural models of the components to predict their thermal growth and the net impact on the clearance between the rotor and diaphragms and other secondary flow paths in the steam turbine, including seals.

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