Experimental Study on Heat Transfer of Pressurized Spray Cooling on the Heated Plate by Using 45° Full Cone Nozzles

2014 ◽  
Vol 535 ◽  
pp. 32-36 ◽  
Author(s):  
Peng Jiang ◽  
Qian Wang ◽  
I. Sabariman ◽  
Eckehard Specht
Keyword(s):  
Heat Transfer ◽  
Heat Removal ◽  
Infrared Camera ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Spray Cooling ◽  
Material Surface ◽  
Transient Temperature ◽  
Heated Plate ◽  
Water Spray Cooling

Water spray cooling is widely used in many industrial processes to control heat removal from a hot material surface. In this work, pressurized spray nozzle was applied to break film boiling immediately once the quenching process is started. For this purpose, a circular disc made of non-ferrous metals is heated to approximately 850 °C and sprayed on one side by hydraulic nozzle and the temperature distribution with respect to time and space is measured by using Infrared camera. On the other side, the measured surface was coated with graphite paint in order to achieve a high emissivity. By this IR thermography, transient temperature measurement can be carried out within the window of 320 × 80 pixels. The heat transfer was analyzed through 1D method. In this method, the temperature difference between both sides neglected. The local heat transfer can then be calculated from a simple differential energy balance.

Experimental Investigation of Corona Wind Heat Transfer Enhancement With a Heated Horizontal Flat Plate

1995 ◽  
Vol 117 (2) ◽  
pp. 309-315 ◽  
Author(s):  
B. L. Owsenek ◽  
J. Seyed-Yagoobi ◽  
R. H. Page
Keyword(s):  
Heat Transfer ◽  
Infrared Camera ◽  
Local Heat Transfer ◽  
Threshold Value ◽  
Local Heat ◽  
Heated Plate ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Heat Transfer Efficiency ◽  
Corona Wind

Corona wind enhancement of free convection was investigated with the needle-plate geometry in air. High voltage was applied to a needle suspended above a heated plate, and heat transfer coefficients were computed by measuring the plate surface temperature distribution with an infrared camera. Local heat transfer coefficients greater than 65 W/m2 K were measured, an enhancement of more than 25:1 over natural convection. The enhancement extended over a significant area, often reaching beyond the 30 cm measurement radius. At high power levels, Joule heating significantly reduced the effective impingement point heat transfer coefficient. The corona wind was found to be more efficient with positive potential than with negative. The heat transfer efficiency was optimized with respect to electrode height and applied voltage. The needle-plate heat transfer effectiveness improved rapidly with increasing height, and became relatively insensitive to height above a threshold value of about 5 cm.

Theoretical and Experimental Study of Electrohydrodynamic Heat Transfer Enhancement Through Wire-Plate Corona Discharge

1997 ◽  
Vol 119 (3) ◽  
pp. 604-610 ◽  
Author(s):  
B. L. Owsenek ◽  
J. Seyed-Yagoobi
Keyword(s):  
Heat Transfer ◽  
Fluid Motion ◽  
Infrared Camera ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Numerical Code ◽  
Transfer Coefficients ◽  
Camera System ◽  
Heat Transfer Coefficients ◽  
Fine Wire

Heat and mass transfer between a surface and the surrounding gas can be enhanced by the application of electric body forces that induce jet or plume-like fluid motion. Such enhancement causes no noise or vibration, can be applied in complex, isolated geometries, and allows simple control of surface temperatures. This paper examines the potentially useful case of multiple fine-wire electrodes suspended in the open air above a grounded and heated horizontal surface. An infrared camera system was used to obtain a complete and accurate distribution of local heat transfer coefficients on the impingement surface. A numerical code was developed and verified by comparison with experimental data. This code was then used to investigate and compare the heat transfer generated by novel electrode geometries.

Experimental Mapping of Local Heat Transfer Coefficients Under Multiple Piezoelectric Fans

2006 ◽  
Author(s):  
Mark Kimber ◽  
Suresh Garimella ◽  
Arvind Raman
Keyword(s):  
Heat Transfer ◽  
Fluid Motion ◽  
Infrared Camera ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Convection Coefficient ◽  
Transfer Coefficients ◽  
Coverage Area ◽  
Heat Transfer Coefficients ◽  
Piezoelectric Fans

Piezoelectric fans have been shown to provide large enhancements in heat transfer over natural convection while consuming very little power. These fans consist of a piezoelectric material attached to a flexible cantilever. When driven at resonance, large oscillations at the cantilever tip cause fluid motion, which in turn, results in improved heat transfer rates. In this study, the local heat transfer coefficients are determined experimentally for piezoelectric fans vibrating close to an electrically heated stainless steel foil, and the entire temperature field is observed by means of an infrared camera. Various vibration amplitudes, distances from heater to fan tip (or gap), and fan pitches are considered for both single-fan and two-fan configurations in impinging orientations. Of particular interest is the increase in heat transfer performance with an additional fan present and the dependence of this increase on the variable parameters. Results show nearly uniform cooling within the envelope of vibration for single-fan experiments with small gaps, and the existence of an optimal gap distance which is dependent on vibration amplitude. The benefits of an additional fan include greater coverage area, but the resulting increase in peak convection coefficient is highly dependent on the fan pitch. Conditions exist where constructive interference is observed which causes a roughly 10% increase in peak convection coefficient while significantly increasing the coverage area. Understanding the local performance of piezoelectric fans provides an important tool to help implement these devices in practical cooling systems.

Pressure Based Prediction of Spray Cooling Heat Transfer Coefficients

2007 ◽  
Author(s):  
Thierry Some ◽  
Eckhard Lehmann ◽  
Hitoshi Sakamoto ◽  
Jungho Kim ◽  
Jin Taek Chung ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Spray Cooling ◽  
Local Heat Transfer Coefficient ◽  
Transfer Coefficients ◽  
Local Pressure ◽  
Heat Transfer Coefficients

An important goal of spray cooling research is the ability to predict local heat transfer coefficient from the spray hydrodynamics. It is postulated in this work that the local pressure is the controlling parameter for local heat transfer coefficient. To test this hypothesis, local pressure and heat transfer data were obtained for a 1×1, 1×2, and 2×2 arrays of hollow cone sprays at two pressures and three standoff distances. A correlation between the pressure and heat transfer coefficient was determined, then used to “predict” the heat transfer coefficient from the pressure data. The local variations in heat transfer coefficient were captured well using this technique, and the area-averaged heat transfer coefficient could be predicted within 12.6%. The technique needs to be verified with different nozzles and fluids over a wider range of 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.

Development of Local Heat Transfer Models for the Safety Assessment of High Temperature Gas-Cooled Reactor Cores—Part II: Prismatic Modular Reactors

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Richard Stainsby ◽  
Matthew Worsley ◽  
Frances Dawson ◽  
Joakim Baker ◽  
Andrew Grief ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Effective Conductivity ◽  
Heat Removal ◽  
Local Heat Transfer ◽  
Multiscale Model ◽  
Local Heat ◽  
Finite Element Simulations ◽  
Normal Operation ◽  
Fuel Elements

This paper extends the work of Part I to be applicable to prismatic block fuel elements and presents a model developed for determining fuel compact and fuel block temperatures of a prismatic core modular reactor. The model is applicable both in normal operation and under fault conditions and is an extension of the multiscale modeling techniques presented in Part I. The new model has been qualified by comparison with finite element simulations for both steady-state and transient conditions. Furthermore, a model for determining the effective conductivity of the block fuel elements—important for heat removal in loss of flow conditions—is presented and, again, qualified by comparison with finite element simulations. A numerical model for predicting conduction heat transfer both within and between block fuel elements has been developed, which, when coupled with the above multiscale model, allows simulations of whole cores to be carried out, while retaining the ability to predict the temperatures of individual coolant channels and individual coated particles in the fuel if required.

An Experimental Study of Mixed, Forced, and Free Convection Heat Transfer From a Horizontal Flat Plate to Air

1982 ◽  
Vol 104 (1) ◽  
pp. 139-144 ◽  
Author(s):  
X. A. Wang
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Flat Plate ◽  
Free Stream ◽  
Convection Heat Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Stream Velocity ◽  
Heated Plate ◽  
Buoyancy Effect

A heated flat plate is tested in a wind tunnel to study mixed convection in both upward and downward positions. It is found that the local heat transfer coefficient is strongly dependent on the free stream velocity and the temperature difference between the surface and the free stream. The buoyancy effect is more pronounced for the heated plate facing upward. This paper correlates the experimental data in terms of Nusselt, Grashof, and Reynolds numbers. The points of onset of instability caused by the buoyancy effect are also examined and correlated in terms of the dimensionless groups. Experimental data are compared with analysis documented in the literature, and the agreement is found satisfactory.

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