Experimental analysis of the influence of wall axial conduction on gas-to-gas micro heat exchanger effectiveness

Yang, Yahui; Morini, Gian Luca; Brandner, Juergen J.

doi:10.1016/j.ijheatmasstransfer.2013.10.008

Cited by 28 publications

(24 citation statements)

References 15 publications

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“…This is done due to the practical limitation of the heat losses to the surroundings in the laboratory environment from both streams. A similar approach has been used by Yang et al [12,13,15] and Koyama et al [19,20] for gas to gas µHxs. There are heat losses to the surroundings in a typical experimental campaign but as shown in this work, given a good insulation of the µHx, the real reason for the deviation ofQ on hot and cold fluid streams in a gas to gas µHx might actually stems from gas compressibility.…”

Section: Cht Modelmentioning

confidence: 99%

“…In this work, a two step methodology is proposed to conduct a performance evaluation study on µHx with acceptable computational power. A gas to gas double layer µHx as shown in Figure 1 that has been experimentally investigated previously by Yang et al [12,13] and Gerken et al [14], is used for validation of proposed methodology. As a first step, a 3D conjugate heat transfer (CHT) model of gas to gas µHx is developed without distributing and collecting manifolds.…”

Section: Introductionmentioning

confidence: 99%

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A Hybrid Numerical Methodology Based on CFD and Porous Medium for Thermal Performance Evaluation of Gas to Gas Micro Heat Exchanger

et al. 2020

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In micro heat exchangers, due to the presence of distributing and collecting manifolds as well as hundreds of parallel microchannels, a complete conjugate heat transfer analysis requires a large amount of computational power. Therefore in this study, a novel methodology is developed to model the microchannels as a porous medium where a compressible gas is used as a working fluid. With the help of such a reduced model, a detailed flow analysis through individual microchannels can be avoided by studying the device as a whole at a considerably less computational cost. A micro heat exchanger with 133 parallel microchannels (average hydraulic diameter of 200 μ m) in both cocurrent and counterflow configurations is investigated in the current study. Hot and cold streams are separated by a stainless-steel partition foil having a thickness of 100 μ m. Microchannels have a rectangular cross section of 200 μ m × 200 μ m with a wall thickness of 100 μ m in between. As a first step, a numerical study for conjugate heat transfer analysis of microchannels only, without distributing and collecting manifolds is performed. Mass flow inside hot and cold fluid domains is increased such that inlet Reynolds number for both domains remains within the laminar regime. Inertial and viscous coefficients extracted from this study are then utilized to model pressure and temperature trends within the porous medium model. To cater for the density dependence of inertial and viscous coefficients due to the compressible nature of gas flow in microchannels, a modified formulation of Darcy–Forschheimer law is adopted. A complete model of a double layer micro heat exchanger with collecting and distributing manifolds where microchannels are modeled as the porous medium is finally developed and used to estimate the overall heat exchanger effectiveness of the investigated micro heat exchanger. A comparison of computational results using proposed hybrid methodology with previously published experimental results of the same micro heat exchanger showed that adopted methodology can predict the heat exchanger effectiveness within the experimental uncertainty for both cocurrent and counterflow configurations.

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Section: Cht Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Hybrid Numerical Methodology Based on CFD and Porous Medium for Thermal Performance Evaluation of Gas to Gas Micro Heat Exchanger

et al. 2020

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“…The partition foil that separates the hot and cold fluid plays a vital role in heat transfer enhancement. Brandner et al [21,22] compared the performance of heat exchange devices with various microstructures manufactured on thin foils to enhance heat transfer. The smaller the foil thickness, the lower the axial conduction thereby leading to high heat transfer.…”

Section: Introductionmentioning

confidence: 99%

Numerical and experimental investigation of a wire-net compact heat exchanger performance for high-temperature applications

Joseph¹,

Delanaye²,

Nacereddine³

et al. 2019

Applied Thermal Engineering

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The objective of this paper is to have a detailed investigation of the microchannel performance of a complex wire-net compact heat exchanger and investigate its collector performance experimentally for a micro combined heat and power system. Localised turbulence can enhance the heat exchanger performance. Besides, this will increase the pressure losses also. Shifting the Reynolds critical to smaller Reynolds number by using perturbators will control the pressure losses and enhance the microchannel thermal e ciency. In this paper, we consider microchannels with wire-net perturbators. The wire-net micro heat exchanger is assembled as a stack of counterflow flow passages with optimised thickness separated by thin foils. A metallic wire-net mesh is inserted in the flow passages to provide the required sti↵ness and enhance the microchannel e ciency. A parametric study was conducted on various heat exchanger parameters to optimise the heat exchanger size, thermal e↵ectiveness and pressure losses for a micro-CHP system. Besides, a detailed investigation of the wire-net flow physics was made using a higher order Reynolds stress turbulence model to obtain the full velocity gradient tensor. This could detail the e↵ect of anisotropic flow physics in the isotropic wire-net microchannels. Lambda 2 criteria was implemented to investigate the flow mixing of the centrally convected non-disturbed mass flow. Furthermore, the analysis of the turbulence production terms provided a deeper insight into flow attachment and detachment near the wire-net intersections. The heat exchanger was experimentally tested, and it was found that the collector pressure losses are not su ciently low as compared to the microchannel pressure losses. The microchannel conjugate heat transfer thermal e↵ectiveness is in good agreement with the overall experimental e ciency.

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“…Obvious manufacturing constraints imply that most microchannels/microtubes are characterized by thick walls, and this induces relevant heat conduction through the microchannel walls, as pointed out by several literatures [1][2][3][4][5][6][7][8][9]. This has an effect on heat transfer device performances: as an example, Rosa et al [2] showed that experiments on single microchannels were in better agreement with macroscale correlations than those performed on arrays of tubes machined from a silicon substrate.…”

Section: Introductionmentioning

confidence: 99%

“…[3][4][5][6][7][8][9]. The magnitude of the axial conduction effect through the walls may be estimated via a nondimensional parameter, the axial conduction number M, defined by Maranzana et al [10].…”

Section: Introductionmentioning

confidence: 99%

Computational Analysis of Conjugate Heat Transfer in Gaseous Microchannels

Croce

Rovenskaya

D’Agaro

2015

Journal of Heat Transfer

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A fully conjugate heat transfer analysis of gaseous flow in short microchannels is presented. Navier-Stokes equations, coupled with Maxwell and Smoluchowski slip and temperature jump boundary conditions, are used for numerical analysis. Results are presented in terms of Nusselt number, heat sink thermal resistance, and resulting wall temperature as well as Mach number profiles for different flow conditions. The comparative importance of wall conduction, rarefaction, and compressibility are discussed. It was found that compressibility plays a major role. Although a significant penalization in the Nusselt number, due to conjugate heat transfer effect, is observed even for a small value of solid conductivity, the performances in terms of heat sink efficiency are essentially a function only of the Mach number.

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Experimental analysis of the influence of wall axial conduction on gas-to-gas micro heat exchanger effectiveness

Cited by 28 publications

References 15 publications

A Hybrid Numerical Methodology Based on CFD and Porous Medium for Thermal Performance Evaluation of Gas to Gas Micro Heat Exchanger

A Hybrid Numerical Methodology Based on CFD and Porous Medium for Thermal Performance Evaluation of Gas to Gas Micro Heat Exchanger

Numerical and experimental investigation of a wire-net compact heat exchanger performance for high-temperature applications

Computational Analysis of Conjugate Heat Transfer in Gaseous Microchannels

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