scholarly journals The Role of Buoyancy Induced Instability in Transpirational Cooling Applications

2021 ◽  
Vol 11 (24) ◽  
pp. 11766
Author(s):  
C. Taber Wanstall ◽  
Phillip R. Johnson
Keyword(s):  
Porous Media ◽  
Thermal Protection ◽  
High Heat ◽  
Working Fluid ◽  
Governing Equations ◽  
Protection Method ◽  
Through Flow ◽  
High Heat Load ◽  
Cubic Density

Transpirational cooling is an effective thermal protection method in hypersonic vehicles. In order to properly manage the high heat load, an understanding of the convective flow regimes as well as the thermophysical properties of the working fluid are required. Often, the vehicle’s fuel is re-purposed as the coolant or working fluid that is passed through the porous media. If the geometry is such that the coolant is heated from below, buoyancy-induced instability can ensue resulting in a mixed convection phenomena. Transpirational cooling applications require a unique analysis which combines a Darcy–Forchheimer relationship for the momentum relation, a flowing base state which introduces non-negligible convective terms for the energy equation, and a novel consideration of a cubic density dependence on temperature. This latter feature is justified by fitting thermodynamic data for typical transpirational cooling conditions. A base state solution is provided and the onset of instability is investigated using linear stability analysis. The governing equations are solved utilizing multiple methods, comparing results from a combination of analytical solutions, finite difference, power series, and Chebyshev methods. Results demonstrate excellent consistency in predictions across these methods and indicate that including non-linear density effects promote a stabilizing effect. Finally, the effect of varying the net through-flow in the porous media is investigated.

scholarly journals Performance of cryogenically cooled, high‐heat‐load silicon crystal monochromators with porous media augmentation

1996 ◽  
Vol 67 (9) ◽  
pp. 3350-3350
Author(s):  
C. S. Rogers ◽  
D. M. Mills ◽  
L. Assoufid ◽  
T. Graber
Keyword(s):  
Porous Media ◽  
Heat Load ◽  
Silicon Crystal ◽  
High Heat ◽  
High Heat Load

scholarly journals Numerical heat transfer analysis of transcritical hydrocarbon fuel flow in a tube partially filled with porous media

Open Physics ◽  
2016 ◽  
Vol 14 (1) ◽  
pp. 659-667 ◽  
Author(s):  
Yuguang Jiang ◽  
Yu Feng ◽  
Silong Zhang ◽  
Jiang Qin ◽  
Wen Bao
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Heat Transfer Enhancement ◽  
Thermal Protection ◽  
Hydrocarbon Fuel ◽  
High Heat ◽  
Heat Transfer Analysis ◽  
High Heat Flux ◽  
Rocket Engines ◽  
Transfer Enhancement

AbstractHydrocarbon fuel has been widely used in air-breathing scramjets and liquid rocket engines as coolant and propellant. However, possible heat transfer deterioration and threats from local high heat flux area in scramjet make heat transfer enhancement essential. In this work, 2-D steady numerical simulation was carried out to study different schemes of heat transfer enhancement based on a partially filled porous media in a tube. Both boundary and central layouts were analyzed and effects of gradient porous media were also compared. The results show that heat transfer in the transcritical area is enhanced at least 3 times with the current configuration compared to the clear tube. Besides, the proper use of gradient porous media also enhances the heat transfer compared to homogenous porous media, which could help to avoid possible over-temperature in the thermal protection.

Experimental Analysis and Modelling of a Novel Thermosyphon System for Electronics Cooling

2021 ◽  
Author(s):  
Filippo Cataldo ◽  
Yuri Carmelo Crea
Keyword(s):  
Machine Learning ◽  
Electronics Cooling ◽  
High Heat ◽  
Working Fluid ◽  
Maximum Heat ◽  
Heat Rejection ◽  
Machine Learning Approach ◽  
Absorbed Power ◽  
High Heat Load ◽  
Footprint Area

Abstract In an era of ever-growing digitalisation, the absorbed power of processing units is becoming an actual challenge for cooling systems. The effectiveness is imperative, but compactness and passiveness are driving factors in the design as well. The goal of the present paper is twofold: 1) to present a detailed experimental campaign on a thermosyphon system for high-heat-load electronics; 2) to propose a model of the thermosyphon system using a Machine Learning approach. The thermosyphon system is composed of a micro-channel evaporator plate directly attached to the heat-generating device and an air-cooled multiport condenser. The height between the evaporator and condenser inlets is 12 cm. The condenser is also proposed in two solutions: the first one has a footprint heat exchange area of 180 x 120 mm2, which allows a single fan's placement; the second one has a footprint area of 240x120 mm2, allowing the placement of two fans. The working fluid used in the system is R1234ze(E) with different charges. The experimental results show that the single-fan condenser reached a maximum heat rejection of 330 W, corresponding to a heat flux of 21.9 W/cm2. The double-fan condenser bore a maximum heat rejection of 570 W (37.7 W/cm2). The model, constructed purely via a Machine Learning tool, shows a very satisfactory agreement between experimental and predicted data.

Role of Flow Enhancement Network during Filling of Fibrous Porous Media

2005 ◽  
Vol 8 (3) ◽  
pp. 281-297 ◽  
Author(s):  
B. Markicevic ◽  
D. Litchfield ◽  
D. Heider ◽  
Suresh G. Advani
Keyword(s):  
Porous Media ◽  
Fibrous Porous Media ◽  
Flow Enhancement

Capillary Imbibition Dynamics in Porous Media

2014 ◽  
Author(s):  
Swayamdipta Bhaduri ◽  
Pankaj Sahu ◽  
Siddhartha Das ◽  
Aloke Kumar ◽  
Sushanta K. Mitra
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Paper Strip ◽  
Capillary Imbibition ◽  
Flow Physics ◽  
Fundamental Understanding ◽  
Paper Based Microfluidics ◽  
To Come

The phenomenon of capillary imbibition through porous media is important both due to its applications in several disciplines as well as the involved fundamental flow physics in micro-nanoscales. In the present study, where a simple paper strip plays the role of a porous medium, we observe an extremely interesting and non-intuitive wicking or imbibition dynamics, through which we can separate water and dye particles by allowing the paper strip to come in contact with a dye solution. This result is extremely significant in the context of understanding paper-based microfluidics, and the manner in which the fundamental understanding of the capillary imbibition phenomenon in a porous medium can be used to devise a paper-based microfluidic separator.

The Role of Porous Media in Homogenization of High Pressure Diesel Fuel Spray Combustion

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Navid Shahangian ◽  
Damon Honnery ◽  
Jamil Ghojel
Keyword(s):  
High Pressure ◽  
Porous Media ◽  
High Speed ◽  
Fuel Spray ◽  
Compression Ignition Engines ◽  
System Pressure ◽  
Novel Approach ◽  
Air Mixing ◽  
The Media

Interest is growing in the benefits of homogeneous charge compression ignition engines. In this paper, we investigate a novel approach to the development of a homogenous charge-like environment through the use of porous media. The primary purpose of the media is to enhance the spread as well as the evaporation process of the high pressure fuel spray to achieve charge homogenization. In this paper, we show through high speed visualizations of both cold and hot spray events, how porous media interactions can give rise to greater fuel air mixing and what role system pressure and temperature plays in further enhancing this process.

Role of macrolayer evaporation in pool boiling at high heat flux

1986 ◽  
Vol 29 (12) ◽  
pp. 1953-1961 ◽  
Author(s):  
A.M. Bhat ◽  
J.S. Saini ◽  
R. Prakash
Keyword(s):  
Heat Flux ◽  
Pool Boiling ◽  
High Heat ◽  
High Heat Flux
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