Flow and Heat Transfer Characteristics of Supercritical Nitrogen in Mini-Tube

2009 ◽  
Author(s):  
P. Zhang ◽  
Y. Huang ◽  
R. Z. Wang
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Flow Characteristics ◽  
Influential Factors ◽  
Experimental Investigations ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Liquid Phases ◽  
Fluid Flow Characteristics

Fluids with the state near the critical points-supercritical fluids show many tremendously strange characteristics, such as singularities in compressibility and viscosity, diminishing difference in vapor and liquid phases and so on which have attracted a lot of investigations both experimentally and theoretically for fundamental research. In the present study, experimental investigations of the heat transfer and fluid flow characteristics of supercritical nitrogen in a mini-tube of 2 mm in diameter and 250 mm in length are carried out, the effects of many influential factors on fluid flow and heat transfer are studied. Meanwhile, the numerical analysis of the fluid flow and heat transfer characteristics of supercritical nitrogen is also conducted by using FLUENT. It is found that the agreement between the experimental and numerical results is quite good and the further interpretation and discussion are carried out.

Fluid Flow and Heat Transfer Characteristics of Multiple Swirling Impinging Jets at Various Impingement Distances

2019 ◽  
Vol 6 (4) ◽  
Author(s):  
Md Habib Ullah Khan ◽  
Zahir U. Ahmed
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heated Surface ◽  
Flow Characteristics ◽  
Impinging Jets ◽  
Heated Plate ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Swirl Flows

This research investigates the fluid flow and heat transfer characteristics for the effect of multiple swirling jets impinging on a heated plate. In this regard, numerical simulations were performed for the inline-type jet arrangement using ANSYS v16.2. Governing equations for turbulent swirl flows were solved by coupled algorithm whereby turbulences are described by SST k-ω model. The analysis is studied for Reynolds number Re = 11600 and swirl number 0.74 at impingement distances equal to 1, 2, 3 and 4 times nozzle diameter. The numerical results showed that impinging distance has a significant effect on both heat transfer and fluid flow characteristics. In case of low impinging distance (H=1D) swirling effect was dominant and the strong recirculation zones resulted in a higher heat transfer from the heated surface. With the increase of impingement distance, the turbulent kinetic energy reduced significantly near the heated surface. It was evident that for higher impingement distance (H=4D) the effect of swirl was greatly reduced resulting in a lower heat transfer from the heated surface

Numerical investigation of heat transfer and fluid flow characteristics in circular wavy microchannel with tangentially branched secondary channels

2019 ◽  
Vol 233 (6) ◽  
pp. 1304-1316
Author(s):  
Valaparla Ranjith Kumar ◽  
Karthik Balasubramanian ◽  
K Kiran Kumar ◽  
Kanishk Bhatia ◽  
Nikhil Tiwari
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Flow Characteristics ◽  
Fluid Mixing ◽  
Heat Transfer Characteristics ◽  
Secondary Channel ◽  
Number Range ◽  
Flow And Heat Transfer ◽  
Overall Performance ◽  
Fluid Flow Characteristics

Wavy microchannels have been shown to possess improved heat transfer capabilities because of greater fluid mixing and boundary layer thinning. In this study, fluid flow and heat transfer characteristics of circular wavy microchannels with tangentially branched secondary channels, were numerically investigated. Its heat transfer and fluid flow characteristics were compared with other specific wavy microchannel geometries. Three-dimensional numerical studies were carried out in the Reynolds number range of 100–300 with uniform heat flux wall boundary condition, using Ansys Fluent commercial software. Validation of the model was done with experimental data from literature. Circular wavy microchannels, owing to constant curvature, lead to nearly constant Dean vortices strength. The tangential branched secondary channels helped in further effective fluid mixing and in reinitializing the boundary layer. These phenomena had significant effect on its heat transfer and fluid flow behavior. Circular wavy microchannels with tangentially branched secondary channels, having secondary channel width to primary channel width ratio (ω) equal to 0.25, showed higher overall performance than other designs considered in the present study. Velocity vectors, velocity and temperature contours are presented to explain the fluid flow and heat transfer characteristics. It is observed that circular wavy microchannels with tangentially branched secondary channel design (ω = 0.25) gives 39.36% higher Nusselt number with 21% increased pressure drop as compared to sinusoidal wavy microchannel design. The overall performance factor of circular wavy microchannel with tangentially branched secondary channel design (ω = 0.25) is higher in the Reynolds number range of 100–250 than all other designs considered in this study.

scholarly journals Heat transfer and flow region characteristics study in a non-annular channel between rotor and stator

2012 ◽  
Vol 16 (2) ◽  
pp. 593-603 ◽  
Author(s):  
M. Nili-Ahmadabadi ◽  
H. Karrabi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Characteristics ◽  
Annular Channel ◽  
Flow Region ◽  
Air Gap ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Slip Ring

This paper will present the results of the experimental investigation of heat transfer in a non-annular channel between rotor and stator similar to a real generator. Numerous experiments and numerical studies have examined flow and heat transfer characteristics of a fluid in an annulus with a rotating inner cylinder. In the current study, turbulent flow region and heat transfer characteristics have been studied in the air gap between the rotor and stator of a generator. The test rig has been built in a way which shows a very good agreement with the geometry of a real generator. The boundary condition supplies a non-homogenous heat flux through the passing air channel. The experimental devices and data acquisition method are carefully described in the paper. Surface-mounted thermocouples are located on the both stator and rotor surfaces and one slip ring transfers the collected temperature from rotor to the instrument display. The rotational speed of rotor is fixed at three under: 300rpm, 900 rpm and 1500 rpm. Based on these speeds and hydraulic diameter of the air gap, the Reynolds number has been considered in the range: 4000<Rez<30000. Heat transfer and pressure drop coefficients are deduced from the obtained data based on a theoretical investigation and are expressed as a formula containing effective Reynolds number. To confirm the results, a comparison is presented with Gazley?s (1985) data report. The presented method and established correlations can be applied to other electric machines having similar heat flow characteristics.

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