Unsteady Simulation of One Dimensional Heat Transfer in Porous Media with a Temperature Jump Condition

2014 ◽  
Author(s):  
Pravin Gangwar ◽  
Michael J. Martin
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Temperature Jump ◽  
Jump Condition ◽  
One Dimensional ◽  
Unsteady Simulation

Two-phase model for mixed convection and flow enhancement of a nanofluid in an inclined channel patterned with heated slip stripes

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Subhasree Dutta ◽  
Somnath Bhattacharyya ◽  
Ioan Pop
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Temperature Jump ◽  
Volume Fraction ◽  
Volume Flow Rate ◽  
Homogeneous Model ◽  
Jump Condition ◽  
Two Phase ◽  
Content Type ◽  
The Impact

Purpose The purpose of this study is to analyze the heat transfer and flow enhancement of an Al2O3-water nanofluid filling an inclined channel whose lower wall is embedded with periodically placed discrete hydrophobic heat sources. Formation of a thin depletion layer of low viscosity over each hydrophobic heated patch leads to the velocity slip and temperature jump condition at the interface of the hydrophobic patch. Design/methodology/approach The mixed convection of the nanofluid is analysed based on the two-phase non-homogeneous model. The governing equations are solved numerically through a control volume approach. A periodic boundary condition is adopted along the longitudinal direction of the modulated channel. A velocity slip and temperature jump condition are imposed along with the hydrophobic heated stripes. The paper has validated the present non-homogeneous model with existing experimental and numerical results for particular cases. The impact of temperature jump condition and slip velocity on the flow and thermal field of the nanofluid in mixed convection is analysed for a wide range of governing parameters, namely, Reynolds number (50 ≤ Re ≤ 150), Grashof number ( 103≤Gr≤5×104), nanoparticle bulk volume fraction ( 0.01≤φb≤0.05), nanoparticle diameter ( 30≤dp≤60) and the angle of inclination ( −60°≤σ≤60°). Findings The presence of the thin depletion layer above the heated stripes reduces the heat transfer and augments the volume flow rate. Consideration of the nanofluid as a coolant enhances the rate of heat transfer, as well as the entropy generation and friction factor compared to the clear fluid. However, the rate of increment in heat transfer suppresses by a significant margin of the loss due to enhanced entropy generation and friction factor. Heat transfer performance of the channel diminishes as the channel inclination angle with the horizontal is increased. The paper has also compared the non-homogeneous model with the corresponding homogeneous model. In the non-homogeneous formulation, the nanoparticle distribution is directly affected by the slip conditions by virtue of the no-normal flux of nanoparticles on the slip planes. For this, the slip stripes augment the impact of nanoparticle volume fraction compared to the no-slip case. Originality/value This paper finds that the periodically arranged hydrophobic heat sources on the lower wall of the channel create a significant augmentation in the volume flow rate, which may be crucial to augment the transport process in mini- or micro-channels. This type of configuration has not been addressed in the existing literature.

Numerical Analysis of Heat Exchangers Used in a Liquid Piston Compressor Using a One-Dimensional Model With an Embedded Two-Dimensional Submodel

2014 ◽  
Author(s):  
Chao Zhang ◽  
Jacob Wieberdink ◽  
Terrence W. Simon ◽  
Perry Y. Li ◽  
James Van de Ven ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Heat Conduction ◽  
Heat Exchangers ◽  
Piston Compressor ◽  
Two Dimensional ◽  
Dimensional Model ◽  
One Dimensional ◽  
Temperature Distributions ◽  
Liquid Piston

The present study presents a one-dimensional liquid-piston compressor model with an embedded two-dimensional submodel. The submodel is for calculating heat conduction across a representative internal plate of a porous heat exchanger matrix within the compression space. The liquid-piston compressor is used for Compressed Air Energy Storage (CAES). Porous-media-type heat exchangers are inserted in the compressor to absorb heat from air as it is compressed. Compression without heat transfer typically results in a temperature rise of a gas and a drop in efficiency, for the elevated temperature leads to wasted thermal energy, due to cooling during subsequent cooling back to ambient temperature. The use of heat exchangers can reduce the air temperature rise during the compression period. A typical numerical model of a heat exchanger is a one-dimensional simplification of the two-energy-equation porous media model. The present authors proposed a one-dimensional model that incorporates the Volume of Fluid (VOF) method for application to the two-phase flow, liquid piston compressor with exchanger inserts. Important to calculating temperature distributions in both the solid and fluid components of the mixture is heat transfer between the two, which depends on the local temperature values, geometry, and the velocity of fluid through the matrix. In the one-dimensional model, although the axial temperatures vary, the solid is treated as having a uniform temperature distribution across the plate at any axial location. This may be in line with the physics of flow in most heat exchangers, especially when the exchangers are made of metal with high thermal conductivity. However, it must be noted that for application to CAES, the gas temperature in the compression chamber rises rapidly during compression and the core of the solid wall may heat up to a different temperature than that of the surface, depending on the geometry, solid material of the exchanger and fluid flow situation. Therefore, a new, one-dimensional model with embedded two-dimensional submodel is developed to consider two-dimensional heat conduction in a representative solid plate. The VOF concept is used in the model to handle the moving liquid-gas interface (liquid piston). The model gives accurate solutions of temperature distributions in the liquid piston compression chamber. Six different heat exchangers with different length scales and different materials are simulated and compared.

Heat Transfer for Gaseous Flow in Microtubes With Viscous Heating

2000 ◽  
Author(s):  
Gokturk Tunc ◽  
Yildiz Bayazitoglu
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Temperature Jump ◽  
Integral Transform ◽  
Jump Condition ◽  
Viscous Heating ◽  
Brinkman Number ◽  
Viscous Effects ◽  
Knudsen Numbers ◽  
Integral Transform Technique

Abstract Convective heat transfer for steady state, laminar, hydrodynamically developed flow in microtubes with a boundary condition of constant temperature is solved by the integral transform technique. Temperature jump condition at the wall and viscous heating within the medium are included. For a given Brinkman number, at specified axial lengths, the viscous effects are presented for the developing range, reaching the fully developed Nusselt number. In previous studies without temperature jump condition at the wall, a 22% increase in the Nusselt number was found for Knudsen numbers ∈ [0,0.12]. In this work we have found that for the same range of Knudsen numbers, the Nusselt number decreases by 35.6%. In addition, as we increase the Prandtl number the temperature jump effect diminishes.

INTERFACIAL CONVECTIVE HEAT TRANSFER FOR RANDOMLY GENERATED POROUS MEDIA

2018 ◽  
Vol 49 (1) ◽  
pp. 77-90
Author(s):  
Eren Ucar ◽  
Moghtada Mobedi ◽  
Azita Ahmadi
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Convective Heat Transfer ◽  
Convective Heat
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