The Local Heat-Transfer Coefficient Around a Heated Horizontal Cylinder in an Intense Sound Field

1962 ◽  
Vol 84 (3) ◽  
pp. 245-250 ◽  
Author(s):  
R. M. Fand ◽  
J. Roos ◽  
P. Cheng ◽  
J. Kaye
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Sound Field ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Horizontal Cylinder ◽  
Local Heat Transfer Coefficient ◽  
The Heat Transfer Coefficient

In order to achieve a better understanding of the physical mechanism of interaction between free convection and sound, an experimental investigation of the local heat-transfer coefficient around the circumference of a heated horizontal cylinder, both in the presence and absence of a strong stationary sound field, has been carried out. The results show that superposition of intense sound upon the free-convection temperature-velocity field about a heated horizontal cylinder increases the heat-transfer coefficient both on the under and upper portions of the cylinder’s surface. In the presence of a sound field for which SPL = 146 db (re 0.0002 microbar) and f = 1500 cps, the maximum measured increases in the local heat-transfer coefficient on the under and upper portions of a 3/4-in-diam cylinder—relative to the free convection case at the same temperature potential—were found to be approximately 250 and 1200 per cent, respectively. A comparison of these results with earlier flow-visualization studies indicates that the relatively large percentage increase in the heat-transfer coefficient on the upper portion of the cylinder is caused by the oscillating vortex flow which is characteristic of thermoacoustic streaming. The reasons for the increase in the heat-transfer coefficient on the lower portion of the cylinder appear to be: (a) An increase in laminar boundary-layer velocities (steady components) in this region; and (b) modification of the boundary-layer temperature profile due to acoustically induced oscillations (unsteady components) within the laminar boundary layer. The experimental data presented can be used to check the validity of future analytical investigations of thermoacoustic phenomena.

Heat Transfer to the Turbulent Separated Flow of Air Downstream of a Step in the Surface of a Plate

1964 ◽  
Vol 86 (2) ◽  
pp. 259-264 ◽  
Author(s):  
R. A. Seban
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Separated Flow ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Local Heat Transfer Coefficient ◽  
Suction Or Injection ◽  
Turbulent Separated Flow

Experiments on a system in which separation of a turbulent boundary layer occurred at a downward step in the surface of a plate and reattached on the plate downstream of the step have produced additional results for the local heat-transfer coefficient and for the velocity and temperature distribution in the separated and reattached regions of the flow. In neither region was there found the kind of similarity near the wall that characterizes flows that are dominated by the friction at the wall, so that even this first element of the usual rationalization of the heat transfer is unavailable for the interpretation of the results. The effect of suction or injection through a slot at the base of the step is also indicated and this demonstrates relatively small effects on both the pressure distribution and the local heat-transfer coefficient.

Local Heat Transfer Coefficient During Condensation in a 0.8 mm Diameter Pipe

2006 ◽  
Author(s):  
Alberto Cavallini ◽  
Davide Del Col ◽  
Marko Matkovic ◽  
Luisa Rossetto
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Operating Conditions ◽  
Local Heat Transfer Coefficient ◽  
Wide Range ◽  
The Heat Transfer Coefficient

The first preliminary tests carried on a new experimental rig for measurement of the local heat transfer coefficient inside a circular 0.8 mm diameter minichannel are presented in this paper. The heat transfer coefficient is measured during condensation of R134a and is obtained from the measurement of the heat flux and the direct gauge of the saturation and wall temperatures. The heat flux is derived from the water temperature profile along the channel, in order to get local values for the heat transfer coefficient. The test section has been designed so as to reduce thermal disturbances and experimental uncertainty. A brief insight into the design and the construction of the test rig is reported in the paper. The apparatus has been designed for experimental tests both in condensation and vaporization, in a wide range of operating conditions and for a wide selection of refrigerants.

Local Heat Transfer Measurements on a Gas Turbine Blade

1971 ◽  
Vol 13 (1) ◽  
pp. 1-12 ◽  
Author(s):  
A. B. Turner
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbine ◽  
Accurate Determination ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Local Heat Transfer Coefficient ◽  
Main Stream ◽  
The Heat Transfer Coefficient

This paper presents an experimental method for determining the variation of the local heat transfer coefficient around gas turbine blades. The method involves the accurate determination of the distribution of metal surface temperature and the heat transfer coefficient and air coolant temperature in the internal cooling passages of the blade. It is shown that from the solution of Laplace's equation and a numerical differentiation at the blade surface of the resulting two-dimensional temperature field an estimate can be made of the normal temperature gradient in the metal which can be related directly to the local heat transfer coefficient at any point of the blade periphery. The results of experiments on a cascade blade undertaken to demonstrate the method are presented. These results show a clear laminar–turbulent transition on the convex surface of the blade but no transition, as such, is indicated on the concave surface. The magnitude of turbulence in the main stream is shown to have a very marked effect both on the mean level of heat transfer to the blade and on the local variation of the heat transfer coefficient.

scholarly journals Heat transfer during condensation of refrigerants in tubular minichannels

2012 ◽  
Vol 33 (2) ◽  
pp. 3-22 ◽  
Author(s):  
Tadeusz Bohdal ◽  
Henryk Charun ◽  
Małgorzata Sikora
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Limited Range ◽  
Local Heat Transfer Coefficient ◽  
Experimental Investigations ◽  
Condensation Process ◽  
The Heat Transfer Coefficient

Abstract The present paper describes the results of experimental investigations of heat transfer during condensation of R134a, R404A and R407C in pipe minichannels with internal diameters 0.31-3.30 mm. The results concern investigations of the local heat transfer coefficient. The results were compared with the correlations proposed by other authors. Within the range of examined parameters of the condensation process in minichannels made of stainless steel, it was established that the values of the heat transfer coefficient may be described with Akers et al., Mikielewicz and Shah correlations within a limited range of the mass flux density of the refrigerant and the minichannel diameter. On the basis of experimental investigations, the authors proposed their own correlation for the calculation of local heat transfer coefficient.

Local and Average Heat Transfer Characteristics for a Disk Situated Perpendicular to a Uniform Flow

1985 ◽  
Vol 107 (2) ◽  
pp. 321-326 ◽  
Author(s):  
E. M. Sparrow ◽  
G. T. Geiger
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Stagnation Point ◽  
Radial Distance ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Local Heat Transfer Coefficient ◽  
Average Heat ◽  
Radial Profiles

Wind tunnel experiments were performed to determine both the average heat transfer coefficient and the radial distribution of the local heat transfer coefficient for a circular disk facing a uniform oncoming flow. The experiments covered the range of Reynolds numbers Re from 5000 to 50,000 and were performed using the naphthalene sublimation technique. To complement the experiments, an analysis incorporating both potential flow theory and boundary layer theory was used to predict the stagnation point heat transfer. The measured average Nusselt numbers definitively resolved a deep disparity between information from the literature and yielded the correlation Nu = 1.05 Pr0.36 Re1/2. The radial distributions of the local heat transfer coefficient were found to be congruent when they were normalized by Re1/2. Furthermore, the radial profiles showed that the local coefficient takes on its minimum value at the stagnation point and increases with increasing radial distance from the center of the disk. At the outer edge of the disk, the coefficient is more than twice as large as that at the stagnation point. The theoretical predictions of the stagnation point heat transfer exceeded the experimental values by about 6 percent. This overprediction is similar to that which occurs for cylinders and spheres in crossflow.

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