Mini- and micro-channels: influence of axial conduction in the walls

Maranzana, Gaël; Perry, Isabelle; Maillet, Denis

doi:10.1016/j.ijheatmasstransfer.2004.04.016

Cited by 277 publications

(211 citation statements)

References 11 publications

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“… conjugate heat transfer is a relevant phenomenon in microchannels and its influence has always to be checked;  the criterion of Maranzana et al [43], eq. (9), can be employed to define the condition for conjugate heat transfer effects being negligible.…”

Section: Conjugate Heat Transfermentioning

confidence: 99%

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Single-phase heat transfer in microchannels: The importance of scaling effects

Rosa

Karayiannis

Collins

2009

Applied Thermal Engineering

249

117

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Microscale single-phase heat transfer is widely used in industrial and scientific applications and for this reason, many related papers have been published in the last two decades. Nevertheless, inconsistencies between published results still exist and there is no generally accepted model for the prediction of singlephase heat transfer in microchannels. This paper presents a review of the experimental and numerical results available in the open literature. Heat transfer in microchannels can be suitably described by standard theory and correlations, but scaling effects (entrance effects, conjugate heat transfer, viscous heating, electric double layer (EDL) effects, temperature dependent properties, surface roughness, rarefaction and compressibility effects), often negligible in macro-channels, may now have a significant influence and have to be accounted for. Furthermore, measurement uncertainties may be more important, due to the reduced characteristic dimensions, so have to be accurately checked and, where possible, reduced. Experiments with single channels are more accurate and in good agreement with predictions from published correlations, in contrast to multi-(parallel) channel experiments. The latter are subject to maldistribution, 3D conjugate heat transfer effects and larger measurement uncertainties. Sub-continuum mathematical models for fluid dynamics are briefly reviewed and explained. These models are expected to gain a growing interest in the near future due to the rapid descent of microchannel dimensions down to the nano-scale. The paper concludes with a concise set of recommendations for purposes of performance and design. For single channels, available correlations for macro-channels can also give reliable predictions at the micro-scale, but only if all the scaling effects can be considered negligible. Otherwise, when scaling effects cannot be neglected or for the case of heat exchangers with parallel channels, suitable numerical simulations may be the sole alternative to carefully designed experiments to evaluate the heat transfer rates. KeywordsMicrochannels, scaling effects, measurement uncertainties, sub-continuum effects.

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Section: Conjugate Heat Transfermentioning

confidence: 99%

“…In these cases, good predictions may be achieved only by appropriate numerical simulations. The criterion of Maranzana et al [43], eq. (9), is used to evaluate if conjugate heat transfer effects have to be taken into account;  viscous heating.…”

Section: Detailed Conclusionmentioning

confidence: 99%

Single-phase heat transfer in microchannels: The importance of scaling effects

Rosa

Karayiannis

Collins

2009

Applied Thermal Engineering

249

117

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“…Reviews on experimental and numerical studies of heat transfer in microchannels published by Mokrani, Bourouga, Castelain and Peerhossaini [19], Hetsroni, Mosyak, Pogrebnyak and Yarin [20], Rosa, Karayiannis and Collins [21] and Sobhan and Garimella [22] confirm the very large scatter in published results and attribute this to "scaling effects", which arise from neglecting phenomenon which are insignificant in conventional sized channels but become significant with the high channel wall surface to fluid volume ratio in microchannel flow. Some examples of these include surface roughness [14], entrance and exit effects [23,24], axial conduction effects [15,25], thermal boundary conditions [26], viscous dissipation effects [27], electric double layer [28] and increased measurement uncertainties [29]. Therefore, it may be difficult to apply traditional correlations to adequately describe the heat transfer in this microchannel absorber plate.…”

Section: Introductionmentioning

confidence: 99%

Thermal analysis of a solar collector absorber plate with microchannels

Oyinlola

Shire

Moss

2015

Experimental Thermal and Fluid Science

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“…The role of the wall axial heat conduction was found to unify the inner wall surface heat flux. With axial conduction included in the convectional size ducts and the uncertainty in the friction factor associated with measurement error addressed in the micro-channels, the analysis of the convectional theory are adequate for micro channels [25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Effects of the thick walled pipes with convective boundaries on laminar flow heat transfer

2014

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Highlights Analytical approach is employed to solve the energy equations with convective boundary condition of the third kind.  The wall thickness, Bi and k pf significantly influence the interfacial heat flux, the wall and fluid bulk temperatures.  The fluid bulk and wall temperatures decrease with decreasing pipe wall thickness and increasing Bi number and k pf .  Increase in the convective heat loss corresponds to a decrease in wall thickness but increase in both Bi and k pf .  The thermal entrance length increases with pipe wall thickness while it decreases with increase in both Bi and k pf . ABSTRACTConjugate heat transfer in laminar tube flow with convective boundary conditions is considered analytically. The steady state problem involving two-dimensional wall and axial fluid conduction is solved using separation of variables for a thick walled cylindrical pipe. The effects of the wall thickness, external Biot number and wall-tofluid thermal conductivity ratio are investigated on the heat flux, fluid bulk and wall temperatures. Results are presented for the cases when the wall thickness is between 0.1 and 2, Biot number ranging between 0.1 and 10, and the ratio of wall-to-fluid thermal conductivity between 3 and 100. These parameters are found to significantly affect the heat transfer characteristics at the thermal entrance region, for instance, increase in wall thickness results in reduced heat flux while increase in Biot number and the ratio of the wall-to-fluid thermal conductivity result in increased heat flux. Decrease in wall thickness, increase in both Biot number and the ratio of the wall-to-fluid thermal conductivity correspond to decreased fluid bulk and wall temperature profiles.Keywords: thick-walled pipe; Biot number; Peclet number; wall-to-fluid thermal conductivity ratio; convective heat transfer characteristic eigen values or roots of pipe eq.

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Mini- and micro-channels: influence of axial conduction in the walls

Cited by 277 publications

References 11 publications

Single-phase heat transfer in microchannels: The importance of scaling effects

Single-phase heat transfer in microchannels: The importance of scaling effects

Thermal analysis of a solar collector absorber plate with microchannels

Effects of the thick walled pipes with convective boundaries on laminar flow heat transfer

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