Exploration of Unsteady Spray Cooling for High Power Electronics at Microgravity Using NASA Glenn’s Drop Tower

2005 ◽  
Author(s):  
Eric L. Golliher ◽  
Chad P. Zivich ◽  
S. C. Yao
Keyword(s):  
High Power ◽  
High Speed ◽  
Fluid Management ◽  
Thermal Response ◽  
Spray Cooling ◽  
High Heat ◽  
Drop Tower ◽  
Space Environment ◽  
Microgravity Environment ◽  
High Heat Flux

At present, there is little understanding of the application of spray cooling to electronics in the microgravity environment. Typically in closed cycle terrestrial spray cooling systems, since not all of the liquid impinging on a hot substrate is evaporated, some residual liquid is separated from its vapor component by gravity and returned to the pump. This technique of phase separation is not available to spacecraft designers. Methods to predict spray cooling performance for ground systems do exist, but they are absent for the space environment. Particularly for NASA spacecraft, there is a need to design spacecraft that use high power laser systems and other systems that use evaporative spray cooling in microgravity. Such knowledge is very important for the performance and life of the device. Reliable analytical methods of predicting thermal response of a spray cooled substrate when considering a transient heat load, such as that found during start up and shut down of a space-based laser or other high heat flux electronics, do not exist. Our goal was to use NASA Glenn’s 2.2 second drop tower to investigate unsteady heat transfer at low Bond numbers and residual fluid behavior in spray cooling. The work contrasts other experiments aboard the NASA Glenn KC-135 low gravity aircraft [1]. Our future plans are to continue the experimental work and include the use of the NASA Glenn 5 second drop tower. This paper will report on some preliminary results of an interesting experimental study performed at NASA Glenn in the summer of 2004. The high speed camera and specially-designed “S.L.O.B.” drop rig provided video and data to assess the fluid management problems that arise in a microgravity spray environment, for both heated and unheated cases. The data show unexpected residual fluid management issues, such as the development of multiple spherical liquid globs, with apparent ordered and repeatable geometry, at the point of impact. The results of these experiments provide direction for further investigation in the future.

Phenomenon and Mechanism of Spray Cooling on Nanowire Arrayed and Hybrid Micro/Nanostructured Surfaces

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Jian-nan Chen ◽  
Rui-na Xu ◽  
Zhen Zhang ◽  
Xue Chen ◽  
Xiao-long Ouyang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
High Speed ◽  
Spray Cooling ◽  
High Heat ◽  
High Heat Flux ◽  
Transfer Enhancement ◽  
Nanostructured Surfaces ◽  
New Energy ◽  
Dry Out

Enhancing spray cooling with surface structures is a common, effective approach for high heat flux thermal management to guarantee the reliability of many high-power, high-speed electronics and to improve the efficiency of new energy systems. However, the fundamental heat transfer enhancement mechanisms are not well understood especially for nanostructures. Here, we fabricated six groups of nanowire arrayed surfaces with various structures and sizes that show for the first time how these nanostructures enhance the spray cooling by improving the surface wettability and the liquid transport to quickly rewet the surface and avoid dry out. These insights into the nanostructure spray cooling heat transfer enhancement mechanisms are combined with microstructure heat transfer mechanism in integrated microstructure and nanostructure hybrid surface that further enhances the spray cooling heat transfer.

Effect of Gravitational Orientation on Flow Boiling of Water in 1054 × 197 µm Parallel Minichannels

2004 ◽  
Author(s):  
Satish G. Kandlikar ◽  
Prabhu Balasubramanian
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Flow Boiling ◽  
High Heat ◽  
Operating Conditions ◽  
Microgravity Environment ◽  
High Heat Flux ◽  
Two Phase ◽  
Mass Fluxes ◽  
Heat Transfer Degradation

Microchannels and minichannels are being considered for high heat flux applications under microgravity environment in space missions. An experimental study is undertaken to determine the effect of gravitational orientation on flow boiling characteristics of water in a set of six parallel minichannels, each 1054 μm wide by 197 μm deep and 63.5 mm long with a hydraulic diameter of 333 μm. Three orientations — horizontal, vertical downflow and vertical upflow — are investigated under identical operating conditions of heat and mass fluxes. High-speed images are obtained to reveal the detailed two-phase flow structure and liquid-vapor interactions. The experimental data and high speed flow visualization indicate that compared to the horizontal case, the flow becomes less chaotic for vertical upflow, while the reversed flow becomes more pronounced in vertical downflow case. The resulting in increase in the back-flow is responsible for channel-to-channel flow maldistribution and heat transfer degradation. From the heat transfer data it is concluded that the performance of the tested channels under microgravity environment will be similar to the horizontal flow case.

An Experimental Study on the Effect of Gravitational Orientation on Flow Boiling of Water in 1054×197μm Parallel Minichannels

2005 ◽  
Vol 127 (8) ◽  
pp. 820-829 ◽  
Author(s):  
Satish G. Kandlikar ◽  
Prabhu Balasubramanian
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
High Speed ◽  
Flow Boiling ◽  
High Heat ◽  
Operating Conditions ◽  
Microgravity Environment ◽  
High Heat Flux ◽  
Two Phase ◽  
Heat Transfer Degradation

Microchannels and minichannels are being considered for high heat flux applications under microgravity environment in space missions. An experimental study is undertaken to determine the effect of gravitational orientation on flow boiling characteristics of water in a set of six parallel minichannels, each 1054μm wide by 197μm deep and 63.5mm long with a hydraulic diameter of 333μm. Three orientations—horizontal, vertical downflow, and vertical upflow—are investigated under identical operating conditions of heat and mass fluxes. High-speed images are obtained to reveal the detailed two-phase flow structure and liquid-vapor interactions. The experimental data and high speed flow visualization indicate that compared to the horizontal case, the flow becomes less chaotic for the vertical upflow case, while the reversed flow becomes more pronounced in the vertical downflow case. The resulting increase in the backflow is responsible for channel-to-channel flow maldistribution and heat transfer degradation. From the heat transfer data it is concluded that the performance of the tested channels in a microgravity environment will be similar to the horizontal flow case.

Thermal response of plasma sprayed tungsten coating to high heat flux

2004 ◽  
Vol 70 (4) ◽  
pp. 341-349 ◽  
Author(s):  
X. Liu ◽  
L. Yang ◽  
S. Tamura ◽  
K. Tokunaga ◽  
N. Yoshida ◽  
...  
Keyword(s):  
Heat Flux ◽  
Thermal Response ◽  
High Heat ◽  
High Heat Flux ◽  
Tungsten Coating ◽  
Plasma Sprayed

Experimental Investigation on Contact Angle of Sintered Copper Powder Wick

2016 ◽  
Vol 819 ◽  
pp. 575-579 ◽  
Author(s):  
Nandy Putra ◽  
Iwan Setyawan ◽  
Dimas Raditya
Keyword(s):  
Contact Angle ◽  
Copper Powder ◽  
High Speed ◽  
Ambient Air ◽  
Video Camera ◽  
High Heat ◽  
High Heat Flux ◽  
Powder Particle Size ◽  
Air Exposure ◽  
Sintered Copper

Heat pipes are widely used in electronic cooling and other applications that require efficient transport or spreading of heat from local sources of high heat flux. One factor that most affect the performance of this device is the wetting properties of the wick material, whereby a hydrophilic wick material is required to transport the liquid from the evaporator to the condenser. The performance of heat pipe will decrease when the wick surface becomes hydrophobic as indicated by changes in its contact angle (CA). This study aims to determine the effect of ambient air exposure on the wettability of wick material. Wettability for a surface by a certain liquid can be shown by measuring the contact angle of liquid droplets on the surface. In this experiment, the contact angle was captured using a high speed video camera followed by image processing and then measured using Image J software. The surface of the sample/wick is a sintered copper powder which in this study through a process of forming or compaction by various parameters such as powder particle size, compacting pressure and sintering temperature. From the results of this study was found that the longer wicks were exposed in the ambient air, the contact angle of the liquid on the wick surface will be getting increased. After 7 days were contaminated on the ambient air, then all samples have been turned into hydrophobic, CA>90°.

An Experimental Study on Saturated Liquid Nitrogen’s Boiling Under Transient Pulsed Laser Irradiation

2004 ◽  
Author(s):  
Zhaoyi Dong ◽  
Xiulan Huai ◽  
G.-X. Wang
Keyword(s):  
Temperature Variation ◽  
High Speed ◽  
Short Pulse ◽  
Heating Surface ◽  
High Heat ◽  
Measuring System ◽  
Experimental Result ◽  
High Speed Photography ◽  
High Heat Flux ◽  
Explosive Boiling

Liquid nitrogen (LN2) was widely applied in many areas, but researches on the boiling behavior under the transient high heat flux have not been reported. In this paper, the high power short pulse duration laser was used to heat the saturated LN2 rapidly, and the high-speed photography aided by the spark light system was employed to take series of photos which displayed the process of LN2’s boiling behavior under such conditions. At the same time, a special temperature measuring system was applied to record the temperature variation of the heating surface. The experimental result disclosed that at the earlier stage of laser heating, an explosive boiling would happen within LN2. After the newly-defined changeover time, the conventional boiling behavior would follow. Therefore the changeover time became an important index to distinguish these two kinds of boiling behaviors. By analyzing the temperature variation of the heating surface, it is found that the latent heat released by the crack of bubbles in explosive boiling is an important factor that greatly influences the boiling heat transfer mechanism.

Effect of Orientation and Draining on Linear Spray Array Thermal Management

2007 ◽  
Author(s):  
Benjamin M. Regner ◽  
Timothy A. Shedd
Keyword(s):  
Heat Transfer ◽  
Fluid Management ◽  
High Heat ◽  
Practical Implementation ◽  
High Heat Flux ◽  
Large Area ◽  
Candidate Solution ◽  
The Impact ◽  
Volumetric Flux ◽  
Uniform Droplet

Spray cooling is a candidate solution for high heat flux cooling applications, and previous work has investigated the impact of parameters of conical sprays such as volumetric flux and Sauter mean diameter on heat transfer performance. However, there has been little work on the impact of drainage and spray orientation on spray performances. In addition, conical sprays are not very practical for large area coverage in compact packages, so this study, presents a novel arrangment that uses linear sprays impinging at an angle such that fluid management and uniform droplet coverage of large areas are both improved. Results for the heat transfer coefficient and CHF of a constrained, practical implementation of a spray array (as opposed to a laboratory-only geometry) are presented for FC-72, FC-40 and HFE-7000.

High heat flux spray cooling with ammonia: Investigation of enhanced surfaces for HTC

2014 ◽  
Vol 75 ◽  
pp. 718-725 ◽  
Author(s):  
Huseyin Bostanci ◽  
Daniel P. Rini ◽  
John P. Kizito ◽  
Virendra Singh ◽  
Sudipta Seal ◽  
...  
Keyword(s):  
Heat Flux ◽  
Spray Cooling ◽  
High Heat ◽  
High Heat Flux
Sign in / Sign up

Export Citation Format

Share Document