Estimation of Average and Local Heat Transfer in Parallel Plates and Circular Ducts Filled With Porous Materials

2004 ◽  
Vol 126 (3) ◽  
pp. 400-409 ◽  
Author(s):  
A. Haji-Sheikh
Keyword(s):  
Heat Transfer ◽  
Porous Materials ◽  
Practical Interest ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Sufficient Accuracy ◽  
Accurate Estimation ◽  
Parallel Plates ◽  
Transfer Coefficients ◽  
Average Heat

Accurate estimation of heat transfer to a fluid passing through a porous medium located between impermeable walls is of practical interest. Generally, the numerical computation of heat transfer to porous media can become time consuming and correlations are needed to enable practitioners to determine this quantity rapidly. In this paper, correlations for two cases are considered: one when porous materials are between two parallel plates and the other when they are within a circular pipe. This presentation includes correlations for both local and average heat transfer coefficients in these two passages for incompressible laminar flow. These correlations require knowledge of local and average heat transfer for unobstructed fluid flowing through these passages with sufficient accuracy. Because existing correlations lack sufficient accuracy, this presentation includes an appendix that emphasizes correlations for heat transfer to fluids passing through unobstructed parallel plate channels and also for circular pipes.

Forced Convection Heat Transfer From a Uniformly Heated Sphere

1962 ◽  
Vol 84 (2) ◽  
pp. 133-140 ◽  
Author(s):  
W. S. Brown ◽  
C. C. Pitts ◽  
G. Leppert
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convection Heat Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Sphere Diameter ◽  
Transfer Coefficients ◽  
Number Range ◽  
Average Heat

An approximate analytical solution is presented for the variation of the local heat-transfer coefficient over the forward half of a uniformly heated sphere. Experimental measurements with water over a Reynolds number range of 5000 to 480,000 and a Prandtl number range of 2.2 to 6.8 give local coefficients which are in good agreement with analytical results. Average heat-transfer coefficients for the uniformly heated sphere are slightly higher than similar results reported earlier [1] for an isothermal sphere. The effect of variations of heat flux on the average heat-transfer coefficient is correlated in a manner similar to that which was used for the isothermal data. Three different duct sizes were used in the experiment to determine the effect of this variable, and the correlations which are presented are based on duct-to-sphere diameter ratios of 2, 2.67, and 4.

Local and Average Heat Transfer and Pressure Drop for Refrigerants Evaporating in Horizontal Tubes

1960 ◽  
Vol 82 (3) ◽  
pp. 189-196 ◽  
Author(s):  
M. Altman ◽  
R. H. Norris ◽  
F. W. Staub
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Test Facility ◽  
Transfer Coefficients ◽  
Local Pressure ◽  
Average Heat ◽  
Heat Transfer Coefficients ◽  
Horizontal Tubes

A test facility is described that has been constructed to investigate local heat transfer and pressure drop for evaporating or condensing refrigerants. The empirical method of B. Pierre [1] for correlating the average heat-transfer coefficients of refrigerants evaporating in horizontal tubes is presented in conjunction with the data of several authors [3–6]. Data on local heat-transfer coefficients and pressure drop are presented for Refrigerant-22 evaporating in two 4-ft-long, 0.343-in-ID straight horizontal tubes, and are correlated by a refinement of the curve proposed in [1]. The procedure of Martinelli-Nelson [9] correlated the data for local pressure drop within 15 per cent.

Heat Transfer From Arrays of Impinging Jets with Large Jet-to-Jet Spacing

1978 ◽  
Vol 100 (2) ◽  
pp. 352-357 ◽  
Author(s):  
B. R. Hollworth ◽  
R. D. Berry
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Target Surface ◽  
Turbulent Jets ◽  
Local Heat ◽  
Impinging Jets ◽  
Transfer Coefficients ◽  
Average Heat ◽  
Turbine Cooling ◽  
Heat Transfer Coefficients

Local and average convective heat transfer coefficients were measured for arrays of widely spaced impinging air jets and correlated in terms of system geometry, air flow, and fluid properties. The configurations were square arrays of circular turbulent jets (spaced from 10–25 diameters apart) incident upon a flat isothermal target surface. Independent parameters were varied over ranges generally corresponding to gas turbine cooling applications. Local heat transfer coefficients were influenced by interference from neighboring jets only when the target plate and the jet orifice plate were less than five jet diameters apart. Average heat transfer coefficients were nearly equal for all the arrays tested as long as the coolant flow per unit area of target surface was held constant. In fact, there was a tendency for the more widely spaced configurations to produce slightly higher average heat transfer under such conditions.

Effects of Several Roughness Elements on an Insulated Wall for Heat Transfer From the Opposite Smooth Heated Surface in a Parallel Plate Duct

1987 ◽  
Vol 109 (1) ◽  
pp. 68-73 ◽  
Author(s):  
K. Ichimiya
Keyword(s):  
Heat Transfer ◽  
Parallel Plate ◽  
Heated Surface ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heated Plate ◽  
Parallel Plates ◽  
Transfer Coefficients ◽  
Roughness Elements ◽  
Flow Situation

Experiments were carried out to examine the effects of several roughness elements on the insulated wall opposite the smooth heated plate for the heat transfer with air flowing through a parallel plate duct. The local heat transfer coefficient, the velocity distribution, the turbulence intensity, and the pressure drop were measured. An optimum pitch of roughness elements for the augmentation of heat transfer exists for each space between two parallel plates. Additionally, the correspondence between the heat transfer and the flow situation is also examined. Acceleration and turbulence produced by roughness elements contribute to the increase of the local heat transfer coefficients on the smooth heated plate. Thermal performance is evaluated at constant pumping power.

Forced-Convective Condensation of Pure Steam and Ammonia-Steam Vapor Mixtures in a Shell-Tube Condenser

1999 ◽  
Author(s):  
Ratnesh K. Sharma ◽  
Vahab Hassani ◽  
Roop L. Mahajan
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Ammonia Concentration ◽  
Transfer Coefficients ◽  
Average Heat ◽  
Heat Transfer Coefficients ◽  
Pure Steam ◽  
Convective Condensation ◽  
Tube Condenser

Abstract In this paper, we present our experimental findings for the forced-convective condensation of pure steam and ammonia-steam vapor mixture in a horizontal annulus in a counter-current shell-tube condenser. Experiments with ammonia-steam mixtures were conducted for ∼ 90% ammonia concentration (by wt.) for vapor inlet mass fluxes ranging from 2 to 5 kg/m2s. The local heat transfer coefficient varied considerably along the condenser and this variation was strongly linked to the condensate flow patterns in the annulus. Based on a condensate drainage model, the flow in the annulus was mapped on to flow maps for horizontal in-tube condensing flows. The delineated flow regimes were utilized to explain augmentation or deterioration of local heat transfer in the condenser. The average heat transfer coefficients are presented as a function of the condensate and vapor Reynolds number for both steam and ammonia-steam mixture. The results for pure steam are higher than those predicted by annular flow correlation developed in the past. For ammonia-steam mixtures, the average heat transfer coefficients are about 16% of those for pure steam due to the vapor layer resistance at the interface.

The Effect of Regulating Elements on Convective Heat Transfer along Shaped Heat Exchange Surfaces

2013 ◽  
Vol 34 (1) ◽  
pp. 5-16 ◽  
Author(s):  
Jozef Cernecky ◽  
Jan Koniar ◽  
Zuzana Brodnianska
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Cfd Simulation ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Temperature Fields ◽  
Transfer Coefficients ◽  
Heat Transfer Intensification ◽  
Heat Transfer Coefficients ◽  
Forced Air

Abstract The paper deals with a study of the effect of regulating elements on local values of heat transfer coefficients along shaped heat exchange surfaces with forced air convection. The use of combined methods of heat transfer intensification, i.e. a combination of regulating elements with appropriately shaped heat exchange areas seems to be highly effective. The study focused on the analysis of local values of heat transfer coefficients in indicated cuts, in distances expressed as a ratio x/s for 0; 0.33; 0.66 and 1. As can be seen from our findings, in given conditions the regulating elements can increase the values of local heat transfer coefficients along shaped heat exchange surfaces. An optical method of holographic interferometry was used for the experimental research into temperature fields in the vicinity of heat exchange surfaces. The obtained values correspond very well with those of local heat transfer coefficients αx, recorded in a CFD simulation.

scholarly journals Investigations of Flow and Heat Transfer Characteristics in a Channel Impingement Cooling Configuration with a Single Row of Water Jets

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4327
Author(s):  
Min-Seob Shin ◽  
Santhosh Senguttuvan ◽  
Sung-Min Kim
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Target Surface ◽  
Channel Height ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Impingement Cooling ◽  
Average Heat ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

The present study experimentally and numerically investigates the effect of channel height on the flow and heat transfer characteristics of a channel impingement cooling configuration for various jet Reynolds numbers in the range of 2000–8600. A single array consisting of eleven jets with 0.8 mm diameter injects water into the channel with 2 mm width at four different channel heights (3, 4, 5, and 6 mm). The average heat transfer coefficients at the target surface are measured by maintaining a temperature difference between the jet exit and the target surface in the range of 15–17 °C for each channel height. The experimental results show the average heat transfer coefficient at the target surface increases with the jet Reynolds number and decreases with the channel height. An average Nusselt number correlation is developed based on 85 experimentally measured data points with a mean absolute error of less than 4.31%. The numerical simulation accurately predicts the overall heat transfer rate within 10% error. The numerical results are analyzed to investigate the flow structure and its effect on the local heat transfer characteristics. The present study advances the primary understanding of the flow and heat transfer characteristics of the channel impingement cooling configuration with liquid jets.

scholarly journals Heat Transfer Coefficient Determination in a Gravity Die Casting Process with Local Air Gap Formation and Contact Pressure Using Experimental Evaluation and Numerical Simulation

2021 ◽  
Author(s):  
T. Vossel ◽  
N. Wolff ◽  
B. Pustal ◽  
A. Bührig-Polaczek ◽  
M. Ahmadein
Keyword(s):  
Heat Transfer ◽  
Contact Pressure ◽  
Local Heat Transfer ◽  
Casting Process ◽  
Local Heat ◽  
Air Gap ◽  
Gap Formation ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Die Casting Process

AbstractAnticipating the processes and parameters involved for accomplishing a sound metal casting requires an in-depth understanding of the underlying behaviors characterizing a liquid melt solidifying inside its mold. Heat balance represents a major factor in describing the thermal conditions in a casting process and one of its main influences is the heat transfer between the casting and its surroundings. Local heat transfer coefficients describe how well heat can be transferred from one body or material to another. This paper will discuss the estimation of these coefficients in a gravity die casting process with local air gap formation and heat shrinkage induced contact pressure. Both an experimental evaluation and a numerical modeling for a solidification simulation will be performed as two means of investigating the local heat transfer coefficients and their local differences for regions with air gap formation or contact pressure when casting A356 (AlSi7Mg0.3).

scholarly journals Condensation inside smooth horizontal tubes: Part 1. Survey of the methods of heat-exchange prediction

2015 ◽  
Vol 19 (5) ◽  
pp. 1769-1789 ◽  
Author(s):  
Volodymyr Rifert ◽  
Volodymyr Sereda
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Film Condensation ◽  
Experimental Investigations ◽  
Phase Flow ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Horizontal Tubes

Survey of the works on condensation inside smooth horizontal tubes published from 1955 to 2013 has been performed. Theoretical and experimental investigations, as well as more than 25 methods and correlations for heat transfer prediction are considered. It is shown that accuracy of this prediction depends on the accuracy of volumetric vapor content and pressure drop at the interphase. The necessity of new studies concerning both local heat transfer coefficients and film condensation along tube perimeter and length under annular, stratified and intermediate regimes of phase flow was substantiated. These characteristics being defined will allow determining more precisely the boundaries of the flow regimes and the methods of heat transfer prediction.

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