Heat and Momentum Transfer Analogies in Laminar Flow

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Anna Gancarczyk ◽  
Marzena Iwaniszyn ◽  
Przemysław J. Jodłowski ◽  
Marcin Piątek ◽  
Mateusz Korpyś ◽  
...  
Keyword(s):  
Laminar Flow ◽  
Momentum Transfer ◽  
Viscous Friction ◽  
Transfer Coefficients ◽  
Short Channel ◽  
Flow Friction ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Structured Catalyst ◽  
Flow Through

In this paper, we briefly present the heat/momentum transfer analogies of Reynolds and the followers for turbulent flow. Next, we discuss differences between turbulent and laminar flow and turn to the Lévêque analogy for laminar flow. This enables heat transfer coefficients (Nusselt numbers) to be derived, based on the flow friction results that include only viscous friction. Some examples of Lévêque analogy applications, such as flow through packed beds, wire gauzes, short-channel structures (short monoliths), and structured catalyst carriers (tube inserts), are given. The Lévêque analogy gave satisfactory accuracy when compared to experiments with flow friction derived on the theoretical basis.

Heat Transfer in a Surfactant Drag-Reducing Solution—A Comparison With Predictions for Laminar Flow

2005 ◽  
Vol 128 (6) ◽  
pp. 557-563 ◽  
Author(s):  
Paul L. Sears ◽  
Libing Yang
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Reynolds Numbers ◽  
High Heat ◽  
High Heat Flux ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Drag Reducing Additive ◽  
Good Agreement

Heat transfer coefficients were measured for a solution of surfactant drag-reducing additive in the entrance region of a uniformly heated horizontal cylindrical pipe with Reynolds numbers from 25,000 to 140,000 and temperatures from 30to70°C. In the absence of circumferential buoyancy effects, the measured Nusselt numbers were found to be in good agreement with theoretical results for laminar flow. Buoyancy effects, manifested as substantially higher Nusselt numbers, were seen in experiments carried out at high heat flux.

Augmentation of Laminar Flow Heat Transfer in Tubes by Means of Twisted-Tape Inserts

1976 ◽  
Vol 98 (2) ◽  
pp. 251-256 ◽  
Author(s):  
S. W. Hong ◽  
A. E. Bergles
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Reynolds Numbers ◽  
Twisted Tape ◽  
Transfer Coefficients ◽  
Constant Property ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Flow Heat ◽  
High Reynolds

Heat transfer coefficients for laminar flow of water and ethylene glycol in an electrically heated metal tube with two twisted-tape inserts were determined experimentally. The Nusselt number for fully developed flow was found to be a function of tape twist ratio, Reynolds number, and Prandtl number. These Nusselt numbers were as much as nine times the empty tube constant property values. The correlation of these data is in fair agreement with the only available analytical predictions. The friction factor is affected by tape twist only at high Reynolds numbers, in accordance with analytical predictions. The performance of these augmented tubes is compared with that of empty tubes under similar heating conditions.

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.

A Numerical Model for Stirling Cycle Machines

1980 ◽  
Vol 102 (4) ◽  
pp. 756-761 ◽  
Author(s):  
D. M. Berchowitz ◽  
I. Urieli ◽  
C. J. Rallis
Keyword(s):  
Integral Equation ◽  
Differential Forms ◽  
Local Heat Transfer ◽  
Viscous Friction ◽  
Local Heat ◽  
Momentum Equation ◽  
Transfer Coefficients ◽  
Reynolds Analogy ◽  
Stirling Cycle ◽  
Heat Transfer Coefficients

The further development of a model to accurately simulate the performance and detailed behavior of Stirling cycle machines is described. The transport equation set (which describe the working gas) is derived in both the so-called integral and differential forms. Only the integral equation set is solved for the simulation. The differential equation set is used to investigate the structure of individual terms in the integral equation set. This procedure allows these terms to be more accurately understood and, hence, modeled. The energy equation includes kinetic energy and dissipation terms while the momentum equation includes the effects of working gas acceleration and viscous friction. Heat leakage and longitudinal conduction in the machine walls are accounted for and due regard is taken of the working gas instantaneous properties. The Reynolds analogy is used to calculate the local heat transfer coefficients.

An Analytical Study of the Optimized Performance of an Impingement Heat Sink

2004 ◽  
Vol 126 (4) ◽  
pp. 528-534 ◽  
Author(s):  
S. B. Sathe ◽  
B. G. Sammakia
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Sink ◽  
High Performance ◽  
Cross Flow ◽  
High Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
High Heat Transfer ◽  
Flow Through

The results of a study of a new and unique high-performance air-cooled impingement heat sink are presented. An extensive numerical investigation of the heat sink performance is conducted and is verified by experimental data. The study is relevant to cooling of high-power chips and modules in air-cooled environments and applies to workstations or mainframes. In the study, a rectangular jet impinges on a set of parallel fins and then turns into cross flow. The effects of the fin thickness, gap nozzle width and fin shape on the heat transfer and pressure drop are investigated. It is found that pressure drop is reduced by cutting the fins in the central impingement zone without sacrificing the heat transfer due to a reduction in the extent of the stagnant zone. A combination of fin thicknesses of the order of 0.5 mm and channel gaps of 0.8 mm with appropriate central cutout yielded heat transfer coefficients over 1500 W/m2 K at a pressure drop of less than 100 N/m2, as is typically available in high-end workstations. A detailed study of flow-through heat sinks subject to the same constraints as the impingement heat sink showed that the flow-through heat sink could not achieve the high heat transfer coefficients at a low pressure drop.

Conjugate Heat Transfer in Air-to-Refrigerant Airfoil Heat Exchangers

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
Yutaka Ito ◽  
Naoya Inokura ◽  
Takao Nagasaki
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Heat Exchangers ◽  
Transfer Coefficients ◽  
Exchange System ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Heat Exchange System ◽  
Inverse Heat Transfer ◽  
Transfer Method

A light and compact heat exchange system was realized using two air-to-refrigerant airfoil heat exchangers and a recirculated heat transport refrigerant. Its heat transfer performance was experimentally investigated. Carbon dioxide or water was used as a refrigerant up to a pressure of 30 MPa. Heat transfer coefficients on the outer air-contact and inner refrigerant-contact surfaces were calculated using an inverse heat transfer method. Correlations were developed for the Nusselt numbers of carbon dioxide and water on the inner refrigerant-contact surface. Furthermore, we proposed a method to evaluate a correction factor corresponding to the thermal resistance of the airfoil heat exchanger.

scholarly journals CONVECTIVE HEAT TRANSFER CHARACTERISTICS OF AQUEOUS TiO2 NANOFLUID UNDER LAMINAR FLOW CONDITIONS

2008 ◽  
Vol 07 (06) ◽  
pp. 325-331 ◽  
Author(s):  
S. M. SOHEL MURSHED ◽  
KAI CHOONG LEONG ◽  
CHUN YANG ◽  
NAM-TRUNG NGUYEN
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Volume Fraction ◽  
Convective Heat Transfer Coefficient ◽  
Transfer Coefficients ◽  
Enhancement Of Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Constant Wall Heat Flux

This paper reports an experimental investigation into force convective heat transfer of nanofluids flowing through a cylindrical minichannel under laminar flow and constant wall heat flux conditions. Sample nanofluids were prepared by dispersing different volumetric concentrations (0.2–0.8%) of nanoparticles in deionized water. The results showed that both the convective heat transfer coefficient and the Nusselt number of the nanofluid increase considerably with the nanoparticle volume fraction as well as the Reynolds number. Along with the enhanced thermal conductivity of nanofluids, the migration, interactions, and Brownian motion of nanoparticles and the resulting disturbance of the boundary layer are responsible for the observed enhancement of heat transfer coefficients of nanofluids.

Conjugate Heat Transfer in a Rotor-Stator System With Through-Flow

2002 ◽  
Author(s):  
Reby Roy ◽  
B. V. S. S. S. Prasad ◽  
S. Srinivasa Murthy
Keyword(s):  
Heat Transfer ◽  
Boundary Layer Thickness ◽  
Conjugate Heat Transfer ◽  
Rotating Disk ◽  
Thermal Boundary Layer Thickness ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Commercial Code ◽  
Through Flow

The conjugate heat transfer in a stationary cylindrical cavity with a rotating disk and fluid through-flow is analysed at various rotational speeds ranging from 10000 to 50000 rpm by using a finite volume commercial code. The numerical model and code are validated for a problem, which involves rotation and fluid through-flow. A reduction of the thermal boundary layer thickness and increase in the heat transfer coefficients are observed with increase in the rotational speed. Marked differences are noticed between the Nusselt numbers obtained from the conjugate and constant temperature analyses.

Unsteady Wake Over a Linear Turbine Blade Cascade With Air and CO2 Film Injection: Part I—Effect on Heat Transfer Coefficients

1994 ◽  
Vol 116 (4) ◽  
pp. 721-729 ◽  
Author(s):  
S. Ou ◽  
J.-C. Han ◽  
A. B. Mehendale ◽  
C. P. Lee
Keyword(s):  
Heat Transfer ◽  
Transition Region ◽  
Density Ratio ◽  
Wake Flow ◽  
Transfer Coefficients ◽  
Pressure Surface ◽  
Heat Transfer Coefficients ◽  
Blowing Ratio ◽  
Nusselt Numbers ◽  
Unsteady Wake

The effect of unsteady wake flow and air (D.R. = 1.0) or CO2 (D.R. = 1.52) film injection on blade heat transfer coefficients was experimentally determined. A spoked wheel-type wake generator produced the unsteady wake. Experiments were performed on a five-airfoil linear cascade in a low-speed wind tunnel at the chord Reynolds number of 3 × 105 for the no-wake case and at the wake Strouhal numbers of 0.1 and 0.3. Results from a blade with three rows of film holes in the leading edge region and two rows each on the pressure and suction surfaces show that the Nusselt numbers are much higher than those for the blade without film holes. On a large portion of the blade, the Nusselt numbers “without wake but with film injection” are much higher than for “with wake but no film holes.” An increase in wake Strouhal number causes an increase in pressure surface Nusselt numbers; but the increases are reduced at higher blowing ratios. As blowing ratio increases, the Nusselt numbers for both density ratio injectants (air and CO2) increase over the entire blade except for the transition region where the effect is reversed. Higher density injectant (CO2) produces lower Nusselt numbers on the pressure surface, but the numbers for air and CO2 injections are very close on the suction surface except for the transition region where the numbers for CO2 injection are higher. From this study, one may conclude that the additional increases in Nusselt numbers due to unsteady wake, blowing ratio, and density ratio are only secondary when compared to the dramatic increases in Nusselt numbers only due to film injection over the no film holes case.

Single-Phase Heat Transfer in Mems-Based Pin Fin Heat Sink

2005 ◽  
Author(s):  
Ali Kosar ◽  
Yoav Peles
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Reynolds Numbers ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Pin Fins ◽  
Micro Pin Fins

An experimental study has been performed on single-phase heat transfer of de-ionized water over a bank of shrouded micro pin fins 243-μm long with hydraulic diameter of 99.5-μm. Heat transfer coefficients and Nusselt numbers have been obtained over effective heat fluxes ranging from 3.8 to 167 W/cm2 and Reynolds numbers from 14 to 112. The results were used to derive the Nusselt numbers and total thermal resistances. It has been found that endwalls effects are significant at low Reynolds numbers and diminish at higher Reynolds numbers.

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