Air cooling of concrete by means of embedded cooling pipes-Part I: Laboratory tests of heat transfer coefficients

1998 ◽  
Vol 31 (5) ◽  
pp. 329-334 ◽  
Author(s):  
Hans Hedlund ◽  
Patrik Groth
Keyword(s):  
Heat Transfer ◽  
Laboratory Tests ◽  
Air Cooling ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Cooling Pipes

A Study of Forced Convection Direct Air Cooling in the Downstream Vicinity of Heat Sinks

1990 ◽  
Vol 112 (3) ◽  
pp. 234-240 ◽  
Author(s):  
G. L. Lehmann ◽  
S. J. Kosteva
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Heat Sink ◽  
Convection Heat Transfer ◽  
Heat Sinks ◽  
Air Cooling ◽  
Transfer Coefficients ◽  
Packaging System ◽  
Transfer Rates ◽  
Heat Transfer Coefficients

An experimental study of forced convection heat transfer is reported. Direct air cooling of an electronics packaging system is modeled by a channel flow, with an array of uniformly sized and spaced elements attached to one channel wall. The presence of a single or complete row of longitudinally finned heat sinks creates a modified flow pattern. Convective heat transfer rates at downstream positions are measured and compared to that of a plain array (no heat sinks). Heat transfer rates are described in terms of adiabatic heat transfer coefficients and thermal wake functions. Empirical correlations are presented for both variations in Reynolds number (5000 < Re < 20,000) and heat sink geometry. It is found that the presence of a heat sink can both enhance and degrade the heat transfer coefficient at downstream locations, depending on the relative position.

scholarly journals EXPERIMENTAL MEASURES OF THE EFFECTIVE HEAT TRANSFER COEFFICIENTS IN AIR BLAST FREEZERS FOR THE PROCESSING OF FRUIT PULPS

2003 ◽  
Vol 2 (1) ◽  
Author(s):  
J. V. Resende ◽  
V. Silveira Junior ◽  
L. Neves Filho
Keyword(s):  
Heat Transfer ◽  
Surface Heat ◽  
Hydraulic Diameter ◽  
Air Cooling ◽  
Transfer Coefficients ◽  
Effective Surface ◽  
Air Blast ◽  
Surface Heat Transfer ◽  
Commercial Practice ◽  
Heat Transfer Coefficients

The effective surface heat transfer coefficients during air blast freezing of plastic polyethylene packages containing fruit pulp models conditioned inside multi layer boxes were evaluated under conditions encountered in commercial practice. The results were presented as dimensionless correlations based on hydraulic diameter of the rectangular ducts. The effects on the surface heat transfer coefficient of the air temperature, air velocity, transducer position inside the boxes and box position in the pillage on the surface were analyzed. The results show: the effect of air-cooling temperature on the surface heat transfer is negligible in the range encountered in blast freezing practice. The effective surface heat transfer coefficients predicted by the non-dimensional correlations based on hydraulic diameter was successfully used to represent the bed irregularities, mainly in arrays of 5 and 3 layers. The effective surface heat transfer coefficients varied according to the position between the top and the bottom of the boxes and was influenced by the number of layers in the arrays.

Estimation of Heat Transfer Coefficients in Dry and Cold-Air Cutting

2010 ◽  
Vol 126-128 ◽  
pp. 341-346 ◽  
Author(s):  
Feng Jiang ◽  
Jian Feng Li ◽  
Jie Sun ◽  
Song Zhang ◽  
Lan Yan
Keyword(s):  
Heat Transfer ◽  
Air Cooling ◽  
Transfer Coefficients ◽  
Temperature Dependent ◽  
Element Analysis ◽  
Cold Air ◽  
Heat Transfer Coefficients ◽  
The Finite Element Analysis ◽  
Infra Red ◽  
Cutting Inserts

For the analysis of cooling effect, the cutting inserts were heated to 900°C and then exposed in the room-air and cold-air with different pressure respectively. The temperature variation were recorded by infra-red (IR) pyrometer. The temperature-dependent global heat transfer coefficients were estimated by the theoretical analysis and experimental data. The finite element analysis (FEA) was employed to simulate the cooling process and modify the estimated heat transfer coefficients. The heat transfer coefficients decreased from 55.1 W/m2•°C (800°C) to 9.32 W/m2•°C (350°C) in the natural cooling and approximately 300 W/m2•°C (600°C) to 60 W/m2•°C (300°C) in the cold-air cooling. Cold-air cooling greatly increased the heat transfer coefficients, but it seemed the air pressure had little pressure on the heat transfer coefficients.

scholarly journals EXPERIMENTAL MEASURES OF THE EFFECTIVE HEAT TRANSFER COEFFICIENTS IN AIR BLAST FREEZERS FOR THE PROCESSING OF FRUIT PULPS

2003 ◽  
Vol 2 (1) ◽  
pp. 11
Author(s):  
J. V. Resende ◽  
V. Silveira Junior ◽  
L. Neves Filho
Keyword(s):  
Heat Transfer ◽  
Surface Heat ◽  
Hydraulic Diameter ◽  
Air Cooling ◽  
Transfer Coefficients ◽  
Effective Surface ◽  
Air Blast ◽  
Surface Heat Transfer ◽  
Commercial Practice ◽  
Heat Transfer Coefficients

The effective surface heat transfer coefficients during air blast freezing of plastic polyethylene packages containing fruit pulp models conditioned inside multi layer boxes were evaluated under conditions encountered in commercial practice. The results were presented as dimensionless correlations based on hydraulic diameter of the rectangular ducts. The effects on the surface heat transfer coefficient of the air temperature, air velocity, transducer position inside the boxes and box position in the pillage on the surface were analyzed. The results show: the effect of air-cooling temperature on the surface heat transfer is negligible in the range encountered in blast freezing practice. The effective surface heat transfer coefficients predicted by the non-dimensional correlations based on hydraulic diameter was successfully used to represent the bed irregularities, mainly in arrays of 5 and 3 layers. The effective surface heat transfer coefficients varied according to the position between the top and the bottom of the boxes and was influenced by the number of layers in the arrays.

Natural and forced convection heat transfer coefficients of various finned heat sinks for miniature electronic systems

2018 ◽  
Vol 233 (2) ◽  
pp. 249-261 ◽  
Author(s):  
SW Pua ◽  
KS Ong ◽  
KC Lai ◽  
MS Naghavi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Sink ◽  
Convection Heat Transfer ◽  
Heat Sinks ◽  
Air Cooling ◽  
Transfer Coefficients ◽  
Cooling Mode ◽  
Heat Transfer Coefficients ◽  
Experimental Heat

Downward lighting light-emitting diodes require cooling with cylindrical fin heat sinks to be mounted on top and cooled under natural convection air cooling mode. Performance simulation would involve specification of the heat transfer coefficient. Numerous methods are available to simulate the performance of conventional plate fin heat sinks including computational fluid dynamics packages. It would be feasible to perform simulation based on conventional flat plate fin heat sinks. A cylindrical fin heat sinks could be simply treated as a plate fin heat sink, if we imagine it cut open and laid out horizontally. A theoretical model is proposed in this paper. An experimental investigation is conducted here to validate its accuracy. Convective heat transfer coefficients were experimentally determined for a horizontally and vertically inclined bare plate operating under natural and forced air cooling modes. In addition, a vertical plate fin heat sink and a vertical cylindrical fin heat sink under natural convection were investigated. Power inputs were kept from 5 to 40 W in order to keep operating temperatures below 100 ℃. Comparison of the experimental heat transfer coefficients and those obtained from well-known existing Nusselt number correlations show that agreement was poor for the bare plate but satisfactory for the plate and cylindrical fin heat sinks. Although they are within the generally accepted range, it would be advisable for actual measurements to be carried out in order to provide more accurate sizing for thermal measurements.

Natural Convection Air Cooling of a Discrete Heat Source on a Conducting Board in a Shallow Horizontal Enclosure

1998 ◽  
Vol 120 (1) ◽  
pp. 89-97 ◽  
Author(s):  
A. Ortega ◽  
B. S. Lall
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Source Area ◽  
Air Cooling ◽  
Transfer Coefficients ◽  
Length Scales ◽  
Heat Transfer Coefficients ◽  
Aspect Ratios ◽  
Significant Length ◽  
Plate Area

Experiments were performed to measure the heat transfer coefficient on the surface of a square flush heat source mounted at the center of an FR-4 plate in a small horizontal enclosure. The plate area was six times larger than the heat source area. Four cases were considered: the plate facing upwards and downwards, and the backside either insulated or convecting. The heat transfer coefficients exhibited distinct behavior at high aspect ratio in which the dominant length scales were related to the source. At intermediate aspect ratios, the length scales of both the source and the enclosure were relevant, and at small aspect ratios a conduction limit was observed. The heat transfer coefficients at high aspect ratios exceeded the prior correlations by 14 percent for upward facing isolated plates when the ratio of heat source area to perimeter was used as the significant length scale, but the dependence on Ra1/4 was consistent. For the downward facing case, the data exceeded the values for a uniformly heated isolated plate by 68 percent. Classical correlations for shallow differentially heated horizontal enclosures were not satisfactory in describing the dependence on enclosure height.

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