Heat transfer coefficients for forced-air cooling and freezing of selected foods

2004 ◽  
Vol 27 (5) ◽  
pp. 540-551 ◽  
Author(s):  
Bryan R. Becker ◽  
Brian A. Fricke
Keyword(s):  
Heat Transfer ◽  
Air Cooling ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Forced Air

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.

Measurement and interpretation of the heat transfer coefficients of metal foams

2005 ◽  
Vol 219 (2) ◽  
pp. 183-191 ◽  
Author(s):  
A J Fuller ◽  
T Kim ◽  
H P Hodson ◽  
T J Lu
Keyword(s):  
Heat Transfer ◽  
Effective Porosity ◽  
Transfer Coefficients ◽  
Constant Input ◽  
Heat Transfer Coefficients ◽  
Copper Foam ◽  
Flow Mixing ◽  
Extended Surface ◽  
Conductive Substrates ◽  
Forced Air

The heat transfer characteristics of FeCrAlY (an iron-based alloy with a melting point of 1510°C sintered foams are presented. The foams have open cells and hollow cell ligaments. The foam samples had a range of cell sizes (1-3 mm) and relative densities (4.6-12.5 percent). Foam cores sandwiched between two conductive substrates were subjected to forced air convection with a constant input heat flux. The volumetric heat transfer coefficient is shown to depend on the effective porosity. Heat transfer is predominantly due to the increased flow mixing that the foam structure promotes. With higher-conductivity materials, the foam also acts to increase the heat transfer by providing an extended surface area, but this is not a strong effect in FeCrAlY foams owing to the low thermal conductivity of 16 W/m K. The FeCrAlY foam is compared with copper foam, and the latter effect is more significant.

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.

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