Thermal and Flow Characteristics of Water–Nitrogen Taylor Flow Inside Vertical Circular Tubes

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Jingzhi Zhang ◽  
Wei Li
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Flow Characteristics ◽  
Numerical Data ◽  
Bond Number ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Pressure Drops ◽  
Taylor Flow ◽  
Bubble Rising Velocity

Heat transfer and flow characteristics of Taylor flows in vertical capillaries with tube diameters ranging from 0.5 mm to 2 mm were studied numerically with the volume of fluid (VOF) method. Streamlines, bubble shapes, pressure drops, and heat transfer characteristics of the fully developed gas–liquid Taylor flow were investigated in detail. The numerical data fitted well with experimental results and with the predicted values of empirical correlations. The results indicate that the dimensionless liquid film thickness and bubble rising velocity increase with increasing capillary number. Pressure drops in liquid slug region are higher than the single-phase flow because of the Laplace pressure drop. The flow pattern dependent model and modified flow separation model which takes Bond number and Reynolds number into account can predict the numerical pressure drops well. Compared with the single-phase flow, less time is needed for the Taylor flow to reach a thermal fully developed status. The Nusselt number of Taylor flow is about 1.16–3.5 times of the fully developed single-phase flow with a constant wall heat flux. The recirculation regions in the liquid and gas slugs can enhance the heat transfer coefficient and accelerate the development of the thermal boundary layer.

Thermal and Flow Characteristics of Water-Nitrogen Taylor Flow Inside Vertical Circular Tubes

2016 ◽  
Author(s):  
Jingzhi Zhang ◽  
Wei Li
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Flow Characteristics ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Liquid Slug ◽  
Pressure Drops ◽  
Taylor Flow ◽  
Separate Model ◽  
Bubble Length

Heat transfer and flow characteristics of Taylor flow in vertical capillaries with tube diameters ranging from 0.5 mm to 2 mm have been investigated numerically with the Volume of Fluid (VOF) method. Streamlines, bubble shapes, pressure drops, and heat transfer characteristics of Taylor flow were investigated in detail. The results indicate that the dimensionless bubble length increases with increasing Re, while the variation of diameters have slight influence on it. A flat tail and sharper nose bubble with longer bubble length and thicker film thickness are obtained at higher Re for the increasing inertia force. Pressure drops in liquid slug region are higher than single phase flow because of the Laplace pressure drop. The flow pattern dependent model and modified separate model in this work can predict the simulation data well with a MAE of 2.416% and 2.289%, respectively. Bo and Re are adopted in the modified separate model to taking surface tension, gravity, inertia, and viscous force into account. The wall temperature Tw increases along X axis in liquid region, and gets its peak at the tail of Taylor bubble region. Nutp, which is about 1.2∼3 times of fully developed single phase flow with constant wall heat flux, is negatively proportional to the dimensionless liquid slug length (Ls*). Taylor flow can enhance the heat transfer efficiently.

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.

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

Frictional Pressure Drops During Vapour-Liquid Flow in Minichannels: Experimental Data and Modelling

2008 ◽  
Author(s):  
Alberto Cavallini ◽  
Davide Del Col ◽  
Marko Matkovic ◽  
Luisa Rossetto
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Single Phase ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Roughness Effects ◽  
Two Phase ◽  
Pressure Drops ◽  
Adiabatic Flow

Condensation in minichannels is widely used in air-cooled condensers for the automotive and air-conditioning industry, in heat pipes and other applications for cooling electronics. The knowledge of pressure drops in such small channels is important in order to optimize heat transfer surfaces. Most of the available experimental work refers to measurements obtained within multiport smooth extruded tubes and deal with the average values over the number of parallel channels. In this context, the present authors have set up a new test apparatus for heat transfer and fluid flow studies in single minichannels. This paper presents new experimental frictional pressure gradient data, relative to single-phase flow and adiabatic two-phase flow of R134a inside a single horizontal mini tube, with 0.96 mm inner diameter and with not-negligible surface roughness. The new all-liquid and all-vapour data are successfully compared against predictions of single-phase flow models. Also the two-phase flow data are compared against Cavallini et al. [1, 2] model, valid for adiabatic flow or for flow during condensation of halogenated refrigerants inside smooth minichannels. Surface roughness effects on the liquid-vapour flow are discussed. In this respect, the friction factor in the proposed model is modified, in order to take into consideration also effects due to wall roughness.

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 numerical investigation on single-phase flow characteristics and frictional pressure drop in helical pipes

2020 ◽  
Vol 52 (4) ◽  
pp. 045505
Author(s):  
Pengxin Cheng ◽  
Nan Gui ◽  
Xingtuan Yang ◽  
Jiyuan Tu ◽  
Shengyao Jiang ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Numerical Investigation ◽  
Single Phase ◽  
Flow Characteristics ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Frictional Pressure Drop
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