Forced Convection Heat Transfer and Hydraulic Losses in Graphitic Foam

2006 ◽  
Vol 129 (9) ◽  
pp. 1237-1245 ◽  
Author(s):  
A. G. Straatman ◽  
N. C. Gallego ◽  
Q. Yu ◽  
L. Betchen ◽  
B. E. Thompson
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Aluminum Foam ◽  
Solid Phase ◽  
Thin Layers ◽  
Small Scale ◽  
Hydraulic Loss ◽  
Base Temperature ◽  
Extended Surface ◽  
Graphitic Foam

Experiments and computations are presented to quantify the convective heat transfer and the hydraulic loss that is obtained by forcing water through blocks of graphitic foam (GF) heated from one side. Experiments have been conducted in a small-scale water tunnel instrumented to measure the pressure drop and the temperature rise of water passing through the foam and the base temperature and heat flux into the foam block. The experimental data were then used to calibrate a thermal non-equilibrium finite-volume model to facilitate comparisons between GF and aluminum foam. Comparisons of the pressure drop indicate that both normal and compressed aluminum foams are significantly more permeable than GF. Results of the heat transfer indicate that the maximum possible heat dissipation from a given surface is reached using very thin layers of aluminum foam due to the inability of the foam to entrain heat into its internal structure. In contrast, graphitic foam is able to entrain heat deep into the foam structure due to its high extended surface efficiency and thus much more heat can be transferred from a given surface area. The higher extended surface efficiency is mainly due to the combination of moderate porosity and higher solid-phase conductivity.

Characterization of Porous Carbon Foam as a Material for Compact Recuperators

2006 ◽  
Author(s):  
A. G. Straatman ◽  
N. C. Gallego ◽  
Q. Yu ◽  
B. E. Thompson
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Porous Carbon ◽  
Aluminum Foam ◽  
Carbon Foam ◽  
Small Scale ◽  
Base Temperature ◽  
Extended Surface ◽  
Surface Convection

Experiments are presented to quantify the convective heat transfer and the hydrodynamic loss that is obtained by forcing water through blocks of porous carbon foam (PCF) heated from one side. The experiments were conducted in a small-scale water tunnel instrumented to measure the pressure drop and the temperature rise of the water passing through the blocks and the base temperature and heat flux into the foam block. In comparison to similar porosity aluminum foam, the present results indicate that the pressure drop across the porous carbon foam is higher due to the large hydrodynamic loss associated with the cell windows connecting the pores, but the heat transfer performance suggests that there may be a significant advantage to using PCF over aluminum foam for extended surface convection elements in recuperators and electronic cooling devices.

Characterization of Porous Carbon Foam as a Material for Compact Recuperators

2006 ◽  
Vol 129 (2) ◽  
pp. 326-330 ◽  
Author(s):  
A. G. Straatman ◽  
N. C. Gallego ◽  
Q. Yu ◽  
B. E. Thompson
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Porous Carbon ◽  
Aluminum Foam ◽  
Carbon Foam ◽  
Small Scale ◽  
Base Temperature ◽  
Extended Surface ◽  
Surface Convection

Experiments are presented to quantify the convective heat transfer and hydrodynamic loss that is obtained by forcing water through blocks of porous carbon foam (PCF) heated from one side. The experiments were conducted in a small-scale water tunnel instrumented to measure the pressure drop and temperature rise of the water passing through the blocks and the base temperature and heat flux into the foam block. In comparison to similar porosity aluminum foam, the present results indicate that the pressure drop across the porous carbon foam is higher due to the large hydrodynamic loss associated with the cell windows connecting the pores, but the heat transfer performance suggests that there may be a significant advantage to using PCF over aluminum foam for extended surface convection elements in recuperators and electronic cooling devices.

Numerical Modeling of Multidirectional Flow and Heat Transfer in Graphitic Foams

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
S. A. Mohsen Karimian ◽  
Anthony G. Straatman
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Pore Structure ◽  
Linear Models ◽  
A Priori ◽  
Experimental Results ◽  
Transfer Model ◽  
Thermal Dispersion ◽  
Wide Range ◽  
Graphitic Foam

To investigate the feasibility of the use of foams with an interconnected spherical pore structure in heat transfer applications, models for heat transfer and pressure drop for this type of porous materials are developed. Numerical simulations are carried out for laminar multidirectional thermofluid flow in an idealized pore geometry of foams with a wide range of geometry parameters. Semiheuristic models for pressure drop and heat transfer are developed from the results of simulations. A simplified solid-body drag equation with an extended high inertia term is used to develop the hydraulic model. A heat transfer model with a nonzero asymptotic term for very low Reynolds numbers is also developed. To provide hydraulic and heat transfer models suitable for a wide range of porosity, only a general form of the length-scale as a function of pore structure is defined a priori, where the parameters of the function were determined as part of the modeling process. The proposed ideal models are compared to the available experimental results, and the source of differences between experimental results and the ideal models is recognized and then calibrated for real graphitic foam. The thermal model is used together with volume-averaged energy equations to calculate the thermal dispersion in graphitic foam. The results of the calculations show that the linear models for thermal dispersion available in literature are oversimplified for predicting thermal dispersion in this type of porous material.

Heat Transfer and Pressure Drop of Lotus-Type Porous Metals

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
Kenshiro Muramatsu ◽  
Takuya Ide ◽  
Hideo Nakajima ◽  
John K. Eaton
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Performance ◽  
Flow Direction ◽  
Heated Surface ◽  
Metal Foams ◽  
Thin Layers ◽  
Random Structure ◽  
Transfer Performance ◽  
Layer Spacing

Metal foams are of interest for heat transfer applications because of their high surface-to-volume ratio and high convective heat transfer coefficients. However, conventional open-cell foams have high pressure drop and low net thermal conductivity in the direction normal to a heated surface due to the fully random structure. This paper examines heat transfer elements made by stacking thin layers of lotus metal which have many small pores aligned in the flow direction. The reduction in randomness reduces the pressure drop and increases the thermal conduction compared to conventional metal foams. Experimental results are presented for the heat transfer performance of two types of lotus metal fins, one with a deterministic pattern of machined holes and one with a random hole pattern made by a continuous casting technique. The layer spacing, the hole diameter, the porosity, and the flow Reynolds number were all varied. The measurements show that spacing between fin layers and the relative alignment of pores in successive fins can have a substantial effect on the heat transfer performance.

scholarly journals Validation of a CFD Model Predicting the Effect of High Level Lateral Acceleration Sloshing on the Heat Transfer and Pressure Drop in a Small-Scale Tank in Normal Gravity

2018 ◽  
Author(s):  
O. Kartuzova ◽  
M. Kassemi
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Current Model ◽  
Lateral Acceleration ◽  
Small Scale ◽  
Cfd Model ◽  
Two Phase ◽  
Large Eddy Simulation Model ◽  
Tank Pressure ◽  
High Level

A two-phase CFD model is developed to study the effects of sloshing with high level lateral acceleration on the heat transfer and pressure drop in a small scale tank. Computational results are compared to the data provided by a non-isothermal sloshing experiment without phase change conducted by T. Himeno et al. at the University of Tokyo and JAXA in 2011 [1]. The results of the current model are, also, compared to CFD predictions reported by Himeno et al. [2]. A step change in lateral acceleration was applied in the experiment. Different levels of lateral acceleration amplitude, varying between 0G and 0.5G, were considered. CFD results for interface movement and tank pressure are presented and compared in this paper to the experimental data for the case in which the value of lateral acceleration was set to 0.5G. The effects of initial and boundary conditions and turbulence modeling approach on the tank pressure change during sloshing are discussed in detail. The effect of conjugate heat transfer in the tank wall is also studied to show its important role in determining the tank pressure evolution. The results of the Reynolds Averaged Navier Stokes (RANS) models are compared to the results of the Large Eddy Simulation model (LES) to underscore the importance of correctly capturing the effects of turbulence for high fidelity predictions.

Heat Transfer Performance of Lotus-Type Porous Metals

2012 ◽  
Author(s):  
Kenshiro Muramatsu ◽  
Takuya Ide ◽  
Hideo Nakajima ◽  
John K. Eaton
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Performance ◽  
Heated Surface ◽  
Metal Foams ◽  
Thin Layers ◽  
Random Structure ◽  
Transfer Performance ◽  
Porous Metals ◽  
Layer Spacing

Metal foams are of interest for heat transfer applications because of their high surface-to-volume ratio and high convective heat transfer coefficients. However, conventional open-cell foams have high pressure drop and low net thermal conductivity in the direction normal to a heated surface due to the fully random structure. This paper examines porous metals made by stacking thin layers of lotus metal which have many small pores aligned in the flow direction. The reduction in randomness reduces the pressure drop and increases the thermal conduction compared to conventional metal foams. Experimental results are presented for the heat transfer performance of two types of lotus metal fins, one with a deterministic pattern of machined holes and one with a random hole pattern made by a continuous casting technique. The layer spacing, the hole diameter, the porosity and the flow Reynolds number were all varied. The measurements show that spacing between fin layers and the relative alignment of pores in successive fins can have a substantial effect on the heat transfer performance.

A Experimental Study of Condensation Heat Transfer and Pressure Drop in a Single High Aspect Ratio Micro-Channel for Refrigerant R134a

2006 ◽  
Author(s):  
Sourav Chowdhury ◽  
Ebrahim Al-Hajri ◽  
Serguei Dessiatoun ◽  
Amir Shooshtari ◽  
Michael Ohadi
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Small Diameter ◽  
Hydraulic Diameter ◽  
Condensation Heat Transfer ◽  
Small Scale ◽  
Measurement Instruments

Only recently, experimental data is available in open literature in condensation of various refrigerants in small hydraulic diameter microchannels. The phenomenon of two-phase flow and heat transfer mechanism in small diameter microchannels (< 1 mm) may be different than that in conventional tube sizes due to increasing dominance of several influencing parameters like surface tension, viscosity etc. This paper presents an on-going experimental study of condensation heat transfer and pressure drop of refrigerant R134a is a single high aspect ratio rectangular microchannel of hydraulic diameter 0.7 mm and aspect ratio 7:1. This data will help explore the condensation phenomenon in microchannels that is necessary in the design and development of small-scale heat exchangers and other compact cooling systems. The inlet vapor qualities between 20% and 80% and mass fluxes of 130 and 200 kg/m2s have been studied at present. The microchannel outlet conditions are maintained at close to thermodynamic saturated liquid state through a careful experimental procedure. A unique process for fabrication of the microchannel involving milling and electroplating steps has been adopted to maintain the channel geometry close to design values. Measurement instruments are well-calibrated to ensure low system energy balance error, uncertainty and good repeatability of test data. The trends of data recorded are comparable to that found in recent literature on similar dimension tubes.

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