Investigation on evaluation criteria of axial wall heat conduction under two classical thermal boundary conditions

Mei, Lin; Wang, Qiuwang; Guo, Zhixiong

doi:10.1016/j.apenergy.2015.04.099

Cited by 14 publications

(4 citation statements)

References 23 publications

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“…They indicated that under specific conditions (M < 0.01), the effect of axial heat conduction can be neglected. However, Lin et al 93 and Zhang et al 94 stated that M can be inadequate to judge whether the effect of the axial heat conduction on heat transfer if the uniform outside wall temperature boundary condition was existing. Moreover, Hetsroni et al 95 stated that the effect of axial heat conduction can be ignored when Re < 150 and M = 0.01.…”

Section: Axial Heat Conductionmentioning

confidence: 99%

A review of heat and fluid flow characteristics in microchannel heat sinks

Çetkin

2020

Heat Trans

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Heat transfer and flow characteristic in microchannel heat sinks (MCHS) are extensively studied in the literature due to high heat transfer rate capability by increased heat transfer surface area relative to the macroscale heat sinks. However, heat transfer and fluid flow characteristics in MCHS differ from conventional ones because of the scaling effects. This review summarizes the studies that are mainly based on heat transfer and fluid flow characteristic in MCHS. There is no consistency among the published results; however, everyone agrees on that there is no new physical phenomenon in microscale that does not exist at macroscale. Only difference between them is that the effect of some physical phenomena such as viscous dissipation, axial heat conduction, entrance effect, rarefaction, and so forth, is negligibly small at macroscale, whereas it is not at microscale. The effect of these physical phenomena on the heat transfer and flow characteristics becomes significant with respect to specified conditions such as Reynolds number, Peclet number, hydraulic diameter, and heat transfer boundary conditions. Here, the literature was reviewed to document when these physical phenomena become significant and insignificant.

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Section: Axial Heat Conductionmentioning

confidence: 99%

A review of heat and fluid flow characteristics in microchannel heat sinks

Çetkin

2020

Heat Trans

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“…Sparrow [3], Maranzana et al [16], Rahimi and Mehryar [17] and Lin et al [18] defined their own dimensionless wall conduction number M, which represented the ratio of the axial heat conduction in the solid wall to the heat convection in the fluid from different angles. Maranzana et al [16] concluded that the axial conduction could be neglected when M was lower than 0.01 for most cases.…”

Section: Introductionmentioning

confidence: 99%

“…Maranzana et al [16] concluded that the axial conduction could be neglected when M was lower than 0.01 for most cases. Lin et al [18] took the temperature gradient of the solid wall and fluid into consideration to define a modified axial conduction number. According to the conclusions obtained from above studies, whether the effects of the axial heat conduction can be neglected or not is highly situation-dependent and the axial conduction number is not the only criterion.…”

Section: Introductionmentioning

confidence: 99%

Numerical analysis of the axial heat conduction with variable fluid properties in a forced laminar flow tube

Zhai

Quan

et al. 2017

International Journal of Heat and Mass Transfer

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Copyright and Reuse:© 2017 Elsevier Ltd. This manuscript version is made available under the terms of the Creative Commons Attribution-NonCommercialNoDerivatives License CC BY NC-ND 4.0 ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way. and solid wall to fluid thermal conductivity ratio of 100, the maximum Nu deviation between constant and variable properties are up to 7.33% at the entrance part for water in the temperature range of 50℃, and 4.45% at the entrance part for n-decane in the temperature range of 120℃, as well as 2.20% at the ending part for air in the temperature range of 475℃, respectively. In addition, the average Nu deviation for water, n-decane and air are 3.24%, 1.94% and 1.74%, respectively. Besides, Nu decreases drastically with decreasing Pe when Pe≤500 and with increasing solid wall to fluid thermal conductivity ratio ( sf k ) when sf k ≤100. It is also found that variable properties have more obvious effects on the velocity profile at the upstream part while more obvious effects on the temperature profile at the downstream part. Enquiries KeywordsConjugate heat transfer; laminar flow; axial heat conduction; variable fluid properties; Nusselt number.

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“…They suggested that the effect of LHC could be neglected when the axial conduction number is less than 0.01. Lin et al [18] studied the effect of LHC for laminar flow in a circular tube by three evaluation criterion parameters i.e., the axial conduction number, the modified axial conduction number and the temperature gradient number. They found that, for constant outside wall temperature boundary condition, the effect of LHC was non-negligible for both axial conduction numbers were below 0.01 and at this condition the temperature gradient number could be used to quantify the effect of LHC.…”

Section: Introductionmentioning

confidence: 99%

A Numerical Study of Small-Scale Longitudinal Heat Conduction in Plate Heat Exchangers

Borjigin

Zeng

et al. 2018

Energies

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Abstract:Longitudinal heat conduction has a significant effect on the heat transfer performance of plate heat exchangers, but longitudinal heat conduction is usually neglected in numerical studies and the thermal design of a heat exchanger. In this paper, heat transfer models with and without longitudinal heat conduction are proposed to analyze the effect of small-scale longitudinal heat conduction in a plate heat exchanger. The performance of small-scale longitudinal heat conduction is illustrated by temperature and heat flux contours in the heat transfer models with and without longitudinal heat conduction. The results show that small-scale longitudinal heat conduction occurs in the plate and a more uniform temperature profile of the plate is obtained due to small-scale longitudinal heat conduction. In balanced flow, the contributions of longitudinal heat conduction for counter-flow, cross-flow and parallel-flow plate heat exchangers are −3.15%, −0.09% and 0, respectively, whereas, for the respective unbalanced flows they are evaluated to be −1.73%, 0.53% and 0.05%, respectively. Moreover, it is observed that small-scale longitudinal heat conduction in plates is influenced by the thermal conductivity of the plate. The higher the thermal conductivity, the larger is the reduction of thermal performance. The contribution of longitudinal heat conduction varies from −0.54% to −4.01%.

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Investigation on evaluation criteria of axial wall heat conduction under two classical thermal boundary conditions

Cited by 14 publications

References 23 publications

A review of heat and fluid flow characteristics in microchannel heat sinks

A review of heat and fluid flow characteristics in microchannel heat sinks

Numerical analysis of the axial heat conduction with variable fluid properties in a forced laminar flow tube

A Numerical Study of Small-Scale Longitudinal Heat Conduction in Plate Heat Exchangers

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