A Theoretical Model for Axial Heat Conduction Effects During Single-Phase Flow in Microchannels

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Ting-Yu Lin ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Single Phase ◽  
Inlet Section ◽  
Phase Flow ◽  
Fluid Temperature ◽  
Single Phase Flow ◽  
Axial Conduction ◽  
Axial Heat ◽  
Axial Heat Conduction

A model is developed to analyze the effect of axial conduction on heat transfer during single-phase flow in microchannels. The axial heat conduction in the wall introduces heat flow toward the inlet section resulting in an increase in the local fluid temperature and a corresponding increase in the wall temperature. Neglecting this effect while reducing the experimental data results in a lower value of the experimental Nusselt number. The model derived in this work takes into account this effect and offers a parameter to estimate the effect introduced by the axial heat conduction effect in the wall.

scholarly journals INVESTIGATION OF SINGLE-PHASE FLOW CHARACTERISTICS IN A STAGGER PIN-FINS COMPLEX GEOMETRY

2021 ◽  
Vol 25 (6) ◽  
pp. 74-81
Author(s):  
R. Shakir ◽  
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Complex Geometry ◽  
Flow Characteristics ◽  
Inlet Temperature ◽  
Phase Flow ◽  
Fluid Temperature ◽  
Single Phase Flow ◽  
Pin Fins ◽  
Micro Pin Fins

The cooling equipment project must use electrical and electronic equipment because of the need to remove the heat generated by this equipment. Investigation; R-113 single-phase flow heat transfer; (50 x 50 mm2) cross-section and (5 mm) height; used in a series of stagger-square micro-pin fins. Inlet temperature of (25 °C); (6) Mass flow rate at this temperature, the recommended range is (0. 0025 -0.01 kg/sec) the inlet and outlet pressures are approximately (1-1.10 bar), and through (25- 225 watts) applied heat. The iterative process is used to obtain the heat flow characteristics, for example; the single-phase heat transfer coefficient is completely laminar flow developing, in this flow, guesses the wall temperature, guess the fluid temperature. The possible mechanism of heat transfer has been discussed

Heat Transfer Investigation of Air Flow in Microtubes—Part I: Effects of Heat Loss, Viscous Heating, and Axial Conduction

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Ting-Yu Lin ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Turbulent Flow ◽  
Heat Loss ◽  
Air Flow ◽  
Heat Losses ◽  
Viscous Heating ◽  
Axial Conduction ◽  
Axial Heat ◽  
Axial Heat Conduction

Experiments were conducted to investigate local heat transfer coefficients and flow characteristics of air flow in a 962 μm inner diameter stainless steel microtube (minichannel). The effects of heat loss, axial heat conduction and viscous heating were systematically analyzed. Heat losses during the experiments with gas flow in small diameter tubes vary considerably along the flow length, causing the uncertainties to be very large in the downstream region. Axial heat conduction was found to have a significant effect on heat transfer at low Re. Viscous heating was negligible at low Re, but the effect was found to be significant at higher Re. After accounting for varying heat losses, viscous heating and axial conduction, Nu was found to agree very well with the predictions from conventional heat transfer correlations both in laminar and turbulent flow regions. No early transition to turbulent flow was found in the present study.

A Porous Medium Approach for Single-Phase Flow and Heat Transfer Modeling in Manifold Microchannel Heat Exchangers

2020 ◽  
Author(s):  
Fabio Battaglia ◽  
Raphael Mandel ◽  
Amir Shooshtari ◽  
Michael M. Ohadi
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Transfer Rate ◽  
Single Phase ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Axial Conduction ◽  
Manifold Microchannel

Abstract Manifold Microchannels have been proven to enhance thermal management in different fields, such as electronic cooling, dry cooling, and high temperature heat exchangers. Manifold-microchannels use a system of manifolds to divide a microgrooved surface into a system of manifolds, thereby reducing pressure drop and increasing heat transfer by utilizing the developing flow regime. Because of this, design of a manifold-microchannel heat exchanger requires the design of the manifold and microchannel. In some situations, a sequential design approach, where one first designs the microchannel and then the manifold — is sufficient to meet the requirements of the problem statements. The more demanding requirements of contemporary applications require manifold microchannel design to evolve and become more complex. In particular, reducing the volume and pitch of the manifold has become necessary. Reducing the volume of the manifold results in a higher flow maldistribution, and the ability to predict how maldistribution affects heat transfer rate is critical. Similarly, reducing the pitch of the manifold increases the effect of axial conduction in the solid, and understanding the effect on heat transfer is important. To those ends, this work shows a porous medium approach for single-phase flow in manifold microchannel, which allows to predict pressure drop, maldistribution, axial conduction, and heat transfer rate with a much smaller computational demand when compared to a full 3D simulation, while guaranteeing very similar results.

Experimental Study on Heat Transfer of Single-Phase Flow and Boiling Two-Phase Flow in Vertical Narrow Annuli

2002 ◽  
Author(s):  
Suizheng Qiu ◽  
Minoru Takahashi ◽  
Guanghui Su ◽  
Dounan Jia
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Two Phase Flow ◽  
Annular Channel ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Narrow Annuli ◽  
Narrow Gaps

Water single-phase and nucleate boiling heat transfer were experimentally investigated in vertical annuli with narrow gaps. The experimental data about water single-phase flow and boiling two-phase flow heat transfer in narrow annular channel were accumulated by two test sections with the narrow gaps of 1.0mm and 1.5mm. Empirical correlations to predict the heat transfer of the single-phase flow and boiling two-phase flow in the narrow annular channel were obtained, which were arranged in the forms of the Dittus-Boelter for heat transfer coefficients in a single-phase flow and the Jens-Lottes formula for a boiling two-phase flow in normal tubes, respectively. The mechanism of the difference between the normal channel and narrow annular channel were also explored. From experimental results, it was found that the turbulent heat transfer coefficients in narrow gaps are nearly the same to the normal channel in the experimental range, and the transition Reynolds number from a laminar flow to a turbulent flow in narrow annuli was much lower than that in normal channel, whereas the boiling heat transfer in narrow annular gap was greatly enhanced compared with the normal channel.

A homogeneous flow model for boiling heat transfer calculation based on single phase flow

2009 ◽  
Vol 50 (7) ◽  
pp. 1862-1868 ◽  
Author(s):  
Guo-xiang Li ◽  
Song Fu ◽  
Yun Liu ◽  
Yong Liu ◽  
Shu-zhan Bai ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Single Phase ◽  
Flow Model ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Homogeneous Flow ◽  
Heat Transfer Calculation

An Experimental Investigation of Gas-Liquid Heat Transfer in Rectangular Micro-Channels

2013 ◽  
Author(s):  
Sira Saisorn ◽  
Somchai Wongwises ◽  
Piyawat Kuaseng ◽  
Chompunut Nuibutr ◽  
Wattana Chanphan
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Flow Direction ◽  
Flow Characteristics ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Two Phase ◽  
Camera System ◽  
Micro Channels ◽  
Flow Mechanisms

The investigations of heat transfer and fluid flow characteristics of non-boiling air-water flow in micro-channels are experimentally studied. The gas-liquid mixture from y-shape mixer is forced to flow in the 21 parallel rectangular microchannels with 40 mm long in the flow direction. Each channel has a width and a depth of 0.45 and 0.41 mm, respectively. Flow visualization is feasible by incorporating the stereozoom microscope into the camera system and different flow patterns are recorded. The experiments are performed under low superficial velocities. Two-phase heat transfer gives better results when compared with the single-phase flow. It is found from the experiment that heat transfer enhancement up to 53% is obtained over the single-phase flow. Also, the change in the configuration of the inlet plenum can result in the different two-phase flow mechanisms.

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